Ask Dave: Changing Motorcycle Fork Springs

[@robertcostello9473]

I have recently bought a yamaha fz1s which is extremely fast compared to my previous bike. The handling was terrible when I got it but now is amazing thanks to your videos. Many thanks 👌👍

[@catalystreactionsbw]

Thank you for rolling your sleeves up and getting to work to make a difference!

[@David.Horne72]

I love your honesty and direct approach. We need you in Australia lol

[@catalystreactionsbw]

I tour there every year in November and December traveling to Cairns, Melbourne, Sydney, Adelaide and Perth. I want to add in Townsend, Canberra and Darwin for 2018

[@David.Horne72]

Dave Moss Tuning Working? Or Holidays? If your in Sydney were would you be visiting? I would not mind meeting you in person if circumstances permitted.

[@catalystreactionsbw]

It is always work. I haven't had a vacation in a very, very long time. International travel is all about teaching others to help them get a better understanding and for them to then pass on/pay forward to other riders who are not quite so mechanical.

[@Yeahbuddylightweigh]

Dave Moss Tuning please tell us when your in Sydney next !!!! 2021

[@chriscox52282]

Fantastic videos dave. This one is vital info thats much needed for all us new riders learning the bike.

[@catalystreactionsbw]

Thank you very much! Glad you feel the content is very helpful.

[@PistonSlap]

Good info Dave! I just put new springs for my weight all the way around on my 2013 ZX6-R. Now I need to get back to the track and dial it in.

[@catalystreactionsbw]

Remember to mark bottom out on the fork and use the zip tie for the first few sessions to assess general travel. Also remember that new springs (stiffer) will make the front end ride higher so evaluate turn in initially verses travel used in braking. That is task #1, not travel used.

[@PistonSlap]

Thank you for the information. So just a though if you have time. If I had my stock springs cranked all the way up to get my sag at (30mm) front and rear. I replaced both front and rear springs for my weight and adjust the sag to 30mm would I not be at the same ride height? I feel like this is a beginners question. Also I use 30mm for sag as i ride street mostly and only have one track day under my belt.

[@catalystreactionsbw]

Great question! If you went to much stiffer springs, in theory at 30mm sag you might be at the same place with ride height. You would need to measure several times due to potential stiction to get an average. You MUST also use a zip tie and mark bottom out to see how much travel you are using, as 30mm sag may be way to little a number. The zip tie should be 10-15mm off the bottom out mark to get the best out of fork compliance with bumps.

[@PistonSlap]

Thanks you so much for the information. I'm really curious to see what happens. I was using all the travel with the stock springs. and like you said with the stiffer sprung I might be able to have rome.of adjusting thkngs.

[@catalystreactionsbw]

Exactly and be very thoughtful about what rate you do need by being honest in your assessment of yourself and what you will be doing with the bike.

[@eb8905-v1m]

Good video and good explanation, thanks for this!

[@subocito]

This is probably a really big question, but... I'm not sure I understand the difference between Compression and Preload. I understand the mechanics in the fork when you adjust them, but not quite the effect that it has. Why would it not be enough to turn the compression in, if you bottom out the fork? (And ofcourse I've watched your videos on both preload and compression, but I still can't figure out when to adjust what) Other than my troubles understanding, the videos are amazing. I've learnt so much more after watching your series.

[@catalystreactionsbw]

Thanks for the kind words! Preload settings are to get travel to within 20-15mm of the bottom out marked on the fork. As it is a big piece of structural equipment, that is the role it fulfills. The compression is there to assist preload in making sure that the spring is not over powered by skill (braking dive) so compression is used as a balance in that regard. Both are tools, you just cannot use one of them alone.

[@maakamccadless8076]

.Dont know if you are still out there Dave,,I bought a used Honda cb 1300 X4 SC 38. when it arrived I noted it sitting low down, on first ride, not only did the water boil after 6km in Thailand , but the forks bottomed...they are not adjustable. not sure of water problem, but forks need new springs..is Progessive ok..I dont look at brand just buy if I can locate...will I need new seals as well..

[@catalystreactionsbw]

I would suggest new 15w oil to the stock amount right away and if you bottom be prepared to add 25cc of oil to each leg.

[@jaakkopusa]

Hey Dave, can you give me an educated opinion? Should I also put thicker fork oil on my year 2004 Suzuki gsx 1400 with 20mm raise blocks on rear springs, when I change for stiffer fork springs 0,73->1,1kg/mm or should I first experiment with original w recommendation? Great videos and if you ever organize test&tune days in Finland I will definetly attend on it

[@catalystreactionsbw]

Thank you for your kind words. I would suggest heavier oil for your 1400 and I would choose 15 or 20w with the increased spring rate.

[@Steve-ec6ed]

I know this video is old but hopefully you'll still see this... At what mileage should I service my forks? I just purchased an 8 yr old bike (R1) w/ 14k miles. Everything feels right but I want to be proactive on my maintenance.

[@catalystreactionsbw]

General rule of thumb is every 6-8,000 miles or 4 years if you want to have excellent tyre wear based on narrow oil viscosity cold to hot. This applies to fork and rear shock.

[@Ninja9981000]

I have a question Dave. What if you are hitting the correct sag numbers, but you've maxed or just about maxed your preload. Would a new heavier spring be beneficial? I've always been under the impression that it would, as you don't want to be maxed in either direction, all in or all out.

[@catalystreactionsbw]

You want to be in the middle 75% of adjustment as much as possible. You also need to review and gather data on installed preload as sometimes correcting this can solve the issue. A quick test is to extend the forks, put the zip tie up against the dust seal and add preload. If the forks don't extend, the issue is internal, not too soft a spring.

[@mrschwifty5564]

Thanks for the videos you probably saved me from a very bad day. Got my first street bike in July a 22 zx6r. And at 190 lbs Preload maxed out I am able to bottom out the front end on the street just messing around. Could you recommend a spring rate better suited for my weight ?

[@catalystreactionsbw]

Thank you for sharing your thoughts and experience. For the forks, changing the damping leg to 7.5w oil is essential, then look for a 1.0kg fork spring. For the rear, shock oil viscosity is good and look for a 95kg spring rate

[@jwdiho]

You mention taking preload all the way out or all the way in. Is it more important to be at correct sag or correct fork travel at full compression when riding hard?

[@catalystreactionsbw]

Taking sag measurements tells you if you are too stiff or too soft to start with. If you can "set" sag as starting point that makes sense so you know where you are. Then riding at 75% if you add or remove all preload, you can start feeling what the suspension does in a controlled testing environment. Out hadns do, but we need to teach them to feel what the forks are telling you.

[@brouder]

Hi Dave! Thank you very much for your videos. I have a CRF450RX 2022 and I use only half of the travel on my forks. Does changing for a lighter density oil will help? Thank you!

[@catalystreactionsbw]

Step one would be to set compression all the way counter clockwise to minimum, then 2 clicks right. See how much travel you use. Then check how much shock travel you are using. If 100% shock travel you are getting no weight transfer forward. Stiffen the shock via compression to you get 3-4mm from the rubber bumper and assess fork travel again. Then lower the forks 5mm and test once more. If you do not get travel, lighter oil will not help as the spring is far too strong for your type of use and a softer spring is needed.

[@brouder]

@@catalystreactionsbw thanks!

[@HORNET6]

Hi Dave, firstly, I really enjoy your vids. Secondly, a question on this video. Should the preload adjuster be treated as a fine tuner once you've changed out for a heavier or lighter spring, starting from all the way out then increasing until 120-130mm of travel is achieved?

[@catalystreactionsbw]

Preload should be used to get the travel/cable tie to 220-25mm from a marked bottom out. You ca then fine tune preload to get closer to that mark with less, or you can add to reduce travel based on what you want/need. You would work in 1 turn increments at that point.

[@aswints5810]

How can i soften the front forks. I tried changing fort oil but still ita quite stiff.. please help. I am using a 400 cc motorcycle in india which wiegh roughly around 180kgs. But stll my bike is giving me a rough ride. Indian roads are filled with potholes and bad pathes and i need a suspension which can absorb them and give me s comfortable ride. Please help..

[@apexhunter2k]

great vids Dave. In really learning alot but I to have a question. I have the 2017 gsxr1000. How do I find out where the fork bottoms out so I can measure effectively to see if I'm in the 20-25 mm range to see how my preload and compression are effected.

[@catalystreactionsbw]

Which 2017 - the standard or RR? In either case there are specs for travel. I have reviewed both of those bikes for exactly this information. The standard is here: kzbin.info/www/bejne/lXalZqKom6xsgZo

[@catalystreactionsbw]

The RR version is here: kzbin.info/www/bejne/mIawpYeXgbVnbbM

[@catalystreactionsbw]

You also get my settings recommendations in there as well so a 2 for 1 video bonus :)

[@robmuhfacka5986]

I have a question I seriously need some help with with my zx10r and it seems you're the Guru 🙌 I'm having the exact opposite problem I have my preload turned out and still have little to no rider sag on my bike even hitting speed bumps with the front tire my zip tie only comes down maybe a quarter away from the fork tube 🙃 I've been trying to dial in the front and back to my weight and I just don't think I'm going to be able to shake this stiff front. It performs well enough for me but I've noticed pains in my palms and some other things from it being so rugged. Also where I'm located the roads aren't the best around so it's been a bumpy ride up front and Cadillac in the back 😅 but for this reason I'm afraid of squatting and running wide 🤦‍♂️

[@catalystreactionsbw]

1. If you cannot get more travel out of the forks no matter what you do, then your oil level is probably way too high taking travel away. That is the most likely answer. You will need to remove the forks and get all the oil out to see what you have for volume. Normally in this instance, forks are overfilled by 50-75cc per leg. You can also remove 100cc from the fork and see if it will bottom. If so, oil volume was the culprit. 2. Once oil volume has been verified, check static sag. If it is less than 15mm from the bike at rest to forks fully extended, the springs are most probably 10-20mm too long. Start here - let's see what you find out.

[@robmuhfacka5986]

@@catalystreactionsbw thank you so much for the reply I never thought about the fork oil being the problem I was thinking spring rate was too high for my light weight as the forks are oem gen 4 zx10r from factory so I'll see if this is the issue thank you for all the information sir 🙏 the only other option I thought of was taking them to get resprung with cartridges setup for my weight once I have the funding and time

[@johnpublic168]

Hi Dave. What spring cps. Is usual for track use.

[@catalystreactionsbw]

Preload is based on skills and track design. You set it to have 15-20mm travel left. If you are a maximum/minimum to get that travel, springs need changing or you refine your skills.

[@DL180sx]

Hi Dave, Aware this video is over 6 years old now but hoping for a response. In order to set rider sag correctly at say 25mm for a track bike I need 7.5/15 turns on preload, well after a few track sessions i have dialled in more preload to prevent bottom out so im sitting at 12/15 turns on preload. Well now my rider sag is far less. Do we ignore rider sag essentially at this point?

[@catalystreactionsbw]

Sag is dynamic and will change. If your compression damping is set correctly at 30% back from maximum with that preload, you ability is better than the spring rate can cope with so potentially (if fork oil is fresh or relatively fresh), you may be in the earning a gold star situation. I would check that your fork oil level is at maximum and you have the righty viscosity oil in there.....

[@DL180sx]

@@catalystreactionsbw my compression is around 5 turns from hardest out of a possible 8.5. I think perhaps heavier springs are required as oil and hight is set per manual.

[@jeradlove8960]

Would this apply to track speeds as well? I have a 2006 R6 with .95 springs in the front and it seems to feel much better in faster turns and tracks than on slower more technical turns and tracks. Is this the suspension or more the rider?

[@catalystreactionsbw]

Great question:- are you more familiar with the fasts tracks, therefore more confident with speed at lean? Are you challenged with technical tracks in carrying lean with less speed? A little self review from memory or video or photo's (body position) is really a great exercise in examining your mind set and skills between the two tracks. If you use the fast settings on a technical track you are getting beaten up....... I'll let you ponder that one :)

[@mechielhengstmengel3590]

Hi Dave, bit late on this video but on my Z900 I bottom out according to my ziptie. I think this is because my rear shock is rock hard, the bike is in balance tho. I believe that in some of your premium video's (I think i've watched like all of them so can't remember exactly which) you've mentioned this as a possibility. Can you confirm or deny this?

[@catalystreactionsbw]

That is correct. If the shock travel is verified as minimal it will crush the front forks as the balance point of the motorcycle is in front of the gas cap. Get 12 to 15mm of static sag in the rear shock and reset the cable tie.

[@perrysimpson4906]

Question: when does a fork spring upgrade go wrong? When you hand over your GSXR 1000 forks to your local Suzuki shop to carry out refurb/seals/bushing/oil etc and swap springs. They carry out your instructions but loose three clicks rebound adjustment on one fork - apologise and quickly resolve in 10 mins, no problem. You then refit forks only to find min rider sag is 49mm! Removed springs free length 260mm, KTECH springs are 230mm as are OEM - spot the most likely cause? :( Lucky I have second had set of fork cartridges where I can source correct length spacers - 100mm. :)

[@perrysimpson4906]

The joys of modified bikes with no records from previous owners and not having the tools etc to check yourself.

[@perrysimpson4906]

By the way OEM springs are progressive as standard on this model.

[@catalystreactionsbw]

I have a video on "what is installed preload in a fork" and that will give you the answer. Bottom line is that spring/spacer length must be calculated accurately.

[@perrysimpson4906]

Thanks Dave. Garage left me a message, tried fitting new Ktech springs but could not secure fork caps, turns out new springs 5mm longer than OEM. Spacers need shortening by 5mm. OEM springs 230mm, spacers 100mm =330mm.

[@perrysimpson4906]

Forks now back on the bike so had a go at setting rider sag. With preload set to 4.5 lines out, first attempt, sag of 53mm, but after exercising forks with damping both completely open forks seemed to free off, sticky at first. Is it possible that with new seals despite proper greasing on assembly that some stiction still present because with preload all out eventually sag of 37mm - new springs 10N? Hopefully give the bike a gentle run out today see if it will benefit from a good warm up then check again.

[@giodc8599]

My current track zx10r, '04, is in the first scenario. I am at 15 mm from the bottom of the forks and all my preload and compression is in. This is on Q3 and old rotors so far (rotors just changed to new ones) . Would you suggest a spring only or a cartridge kit? The latter, i guess, can get expensive.

[@catalystreactionsbw]

How oil is the fork oil, what oil height or volume do you have? That is the first data point. The old oil and low volume may be causing you to use all the travel so review this first. Then check installed preload in the forks: kzbin.info/www/bejne/f3SukGWqjZ6Sh8k If that all adds up, springs are next. A cartridge kit is a long way away yet.

[@giodc8599]

Dave Moss Tuning Cheers Dave, i'll start with spring and setup to try and get a better feel on the front.

[@yammydodger1988]

Hi Dave, i have an Mt09 2018 model with front spring total length of 138mm, could you tell me what the ideal rider sag measurement should be please? I'm currently at 45mm. Great vids by the way.

[@catalystreactionsbw]

Ideal sag is 30-40mm. Ride and put a zip tie on the right fork tube to see how much travel you use. If you are close to bottom, change to 30mm and ride again. davemosstuning.com/?s=fork+bottom+out

[@MT--WesleyCrumblebee]

Hey Dave. Running as you advised for my 2016 ZX10 for the forks. But with 5 in preload, 2.5 out rebound and 2 out comp, im getting 15mm of sag because the springs are so heavy, BUT im getting mechanical bottom out under heavy braking. The forks feel quite aggressive in the canyons/mountains through bumpy turns so Im concerned with the comp or rebound skipping over some rough patches, but I also dont want to back out the preload further because I am making full use of the travel with braking. I dont know whats worse, pushing the front over rough patches or tucking it under braking :( 98kg in gear. Shock is at 25mm sag. 1.5 comp out, 2.5 rebound out. Rear feels good.

[@catalystreactionsbw]

In that case you need to add more preload and back off the compression setting slightly to find a better balance for you.

[@4jeeper95]

Question Dave..(93xj600) I'm 230lbs. so I am upgrading my springs front and rear..maxed the fork springs out a few times..factory is .47 (10 wt.)went to a .95. and a +200 lb rear spring.. should I change the oil weight to a 7.5, 5 or 2.5?? I ride off road 40% of the time. thanks for any advice.

[@catalystreactionsbw]

Given the off road component and your weight, I would try 20w for the forks and see how the damping works when the forks get hot.

[@patdudley7635]

Hi Dave. Id like to ask.... As forks are constantly improving over the years. wondering should I upgrade the springs and re-valve the ones on my old CBR900RR (SC33) or swap the front end for something like 09 CBR1000R USD forks (radial) and front wheel. Ive done this before on other bikes but can a 98 front end ever be as good as these later ones ?. Total road use for me but I like to improve older bikes in any way I can as far as Performance and handling goes

[@catalystreactionsbw]

Hi Pat. Remember that forks were built to match the frame, so upgrading to modern forks can have a negative effect on handling as the steering head can twist more. I have hard personal experience of this first hand with a front wheel hopping in the air mid corner. So my advice would be to respring/revalve the OEM forks and get the best out of that so you find a win win solution.

[@patdudley7635]

@@catalystreactionsbw Brilliant thanks. On my old 97 TL1000S the suspension front and back (especially back) was terrible imo , so I swapped for better and it worked for me. This time on the CBR the suspension doesn't seem too bad for my riding skills but as I'm throwing money at it I just need to spend it in the right places. Glad I asked . Don't want to make things worse

[@perrysimpson4906]

Hi Dave if my investigation rings true and I need new springs, given road/street only riding, what are your thoughts on progressive springs? I can only presume they have weight limit and cover quite a large spring range/rates?

[@catalystreactionsbw]

That type of spring can be created different ways so you need to look at the soft to hard rate eg: .85-1.0 in 3 inches of travel. Most spring manufacturers do assist with this type of information so you know what you are getting for range.

[@karlogrady4907]

Loving the vids dave. Long story short i was bottoming out my standard forks with max pre load so ive swapped them out for heavier ones and got it about right, but ive now found that my shock if way too soft in comparison, especially when i go two up even on max rear preload still. Is it now just a case of getting a heavier shock spring and making them equal ? Cheers

[@catalystreactionsbw]

Thanks Karl! If you have set sag on the tight side 25-30mm and have compression & rebound set correctly, put a little grease on the shock shaft or ale a look to see if it is 100% clean. If it has 3-5mm of dirt at the base of the shaft your damping settings will be the source of the issue. If it is 100% clean, then the shock spring upgrade is required.

[@karlogrady4907]

@@catalystreactionsbw thats awesome thanks dave. Could i also ask what spring/spring rate you would recommend if i do have to change ? Its a standard 2010 bmw s1000rr shock in my 1990 vfr nc30 (i have got a hrc replica shock linkage to allow use of linear shocks like this) (it also has a surrogate zxr400 front) I weigh 220lbs fully geared up and i ride hard on the street 365 rain or shine and i do ride two up regularly. I did contact k-tech and they recommended a 95Nm spring but i wanted to ask you as i know you know what your doing. Any help will be great

[@lachlanmassie5691]

Thanks very much for the video dave, is it ok if my front fork is bottoming out on hard braking? or should the zip tie still be 20mm above the mechanical bottom out? i have changed my springs for my weight and i still find the zip tie on my forks being bottomed out.

[@catalystreactionsbw]

Did you mark mechanical bottom out so you know it bottomed? If that is confirmed, how much preload are you using - 50% of the total range? Is compression set at 30% from maximum? Is the oil fresh and if so, did you use the oil level set in the service manual? If yes to all, add preload to 75% of the total range. If you bottom again, recheck the math on installed preload/spacer length to make sure you did the math right.

[@lachlanmassie5691]

thanks dave for your prompt reply!!

[@LigerZero1985]

i really wish the yamaha r3 has inverted fork rather than the conventional fork. very hard to tell if i have bottom out the spring

[@catalystreactionsbw]

You can still mark bottom out on the R3 just as you would any other fork that is telescopic or upside down. When we get a chance to shoot some video, I will try to find an R3 for this purpose.

[@sipwitme4625]

Dave I've added a zip tie on my 13 R1.. my forks has never been adjusted (all stock).. I noticed that it's bottoming out,. How do I fix this.. I don't know what to turn or click on each fork.. thanks in advance. Probably a dumb question, but hey if u don't know, u don't know..

[@catalystreactionsbw]

Please email me [e-mail] with answers to these questions: miles/kms on the bike, changes from stock, your weight without gear, brand, model and size of tires.

[@kostasrestas]

hello my friend! i have an xt660z tenere 2008 and some days before i replace the forks and the wheel with forks and wheel from wr426f now i have to change the springs with stiffer ones because tenere is way more heavy and i'm 100 kilos. but i don't know what springs i buy.. what i have to check ,calculate or consider before i buy???

[@catalystreactionsbw]

Kostas - you would remove and measure spring length and diameter and then look at Hyperpro's website for replacement springs. General rule of thumb is 8.5 to 9.5 range to start with the bike and your weight. Getting a piston kit from Race Tech for the forks would also be a very good idea.

[@johnwoo505]

HI Dave I thank you for all the information you give us i have question to ask you i have 2000 kawasaki c10 concors every time i hit the bump or pad hole the handle bar shake what coud be the problem thanks

[@catalystreactionsbw]

If you put a zip tie on the fork you may find that the zip tie is bottomed out on the fork. If not, tire pressure may be too low so the impact alters the steering via carcass deflection. Try the zip tie first, then move on to tyre pressures.

[@johnwoo505]

ok thank let me try

[@IvoBELGIUM]

Hi Dave, In the other video, you talked about adjusting sag. In my case, i need to reduce preload to get the right sag, BUT i also have to increase preload due to bottom lining the fork as demonstrated in this vid. What should i do? progressive springs??

[@catalystreactionsbw]

If your skill level means that you need to increase preload to stop the forks bottoming, then I'd like to ask where is your compression setting? Is it also close to being close/all the way clockwise? If you don't have compression, how old is the fork oil? Fresh oil that is slightly thicker with a higher all level may be all you need.

[@IvoBELGIUM]

Specs : GSXR 600 K4 compression is 1.5 turns out, springs are stock, im 210lbs, preload is at stock setting (4 rings showing) oil needs to be replaced but im not sure wich thickness to get. Also i'm only bottoming the forks when emergency braking (should that be ignored?)

[@epiphonesg007]

You need stiffer springs.

[@catalystreactionsbw]

Given your weight, 10 or 15w Maxima or Motul oil. Springs will help, .95 or 1.0 rate.

[@IvoBELGIUM]

ok thanks Dave !

[@matt3122]

I hear a spring knocking sound when I hold the brake and compress the forks. I have another bike of the same model it never made this sound. I replaces the seals and oil. The internals looked mint. The only think "unusual" was one spring was 1/16" shorter than the other. They are Yamaha WR250Rs. Can you give me any advice about what's wrong and what to do to fix it?

[@catalystreactionsbw]

If the spring knocks it might not be seated correctly in the fork against the cap and/or the cartridge. That much shorter won't leave it loose in the forks. Loosen the cap and check the alignment.

[@matt3122]

Dave Moss Tuning the things they seat against are just flat. Any other possibilities?

[@matt3122]

Dave Moss Tuning I found the problem on my bike. My bike has forks with the wide tube on top and narrow tube on bottom. So I held the bottom of the wide tube and the bottom of the narrow tube at the place where the axle is. I moved the narrow tube forward/backward. One fork had play. I rotated the wide tube by 90 degrees in the triple tree clamp. I checked for play and it was no longer there. So I think the wide tube is bad in my case. BTW way thanks for responding to my comments!!!

[@catalystreactionsbw]

@@matt3122 excellent approach to find a source that requires an inspection of the bushings and fork tube

[@navystrackstar]

Thanks for these videos Dave, question, depending on the day and my time spent in the gym I’m about 155 lbs, I have gotten up to 170 but no higher what springs would you recommend for my 2011 R1 and 2009 R6? Out of any mods I know when it comes to roadracing suspension is the most important so I want to know where to start

[@catalystreactionsbw]

I would start at .90 for the street and if you are very aggressive, .95 would be better.

[@navystrackstar]

Dave Moss Tuning thanks and how about for the track which I’m focusing more on now?

[@catalystreactionsbw]

Carry on with what you have until you are in the last 25%of preload range for the forks and shock springs, then upgrade. You don't instantly go faster at the track and it takes several days before you settle in to track speeds as some serious calibration is required.

[@DmanGuitar327]

In theory, if at .90kg spring, n lets say you need it a tad stiffer.. Next step is .95kg but thats a bit stiff,.. Can you run .90 spring in one fork and .95 in the other? Would that equal a .925kg spring? Thx dave

[@catalystreactionsbw]

Splt rate of .25 and .75 is normal practice. Stiff spring in the right leg every time.

[@DmanGuitar327]

So i can run .95 in right fork and .90 in the left?

[@catalystreactionsbw]

@@DmanGuitar327 correct

[@mechanictp]

Hey Dave. I run a 2007 CBR 600 RR with stock suspension and my weight is 203-205 lbs full geared. I have set the sag to 37-27 for track use. It's time to service again my suspension but i decided to upgrade my suspension and i will buy a ttx gp for the rear and piston kit plus springs for the front. On the stock shock the preload was set 4 from HARD to have the that sag (27) and on the forks 8 from hard (6 3/8 from soft) What are the proper springs for my bike, weight and use(track/road 50/50)? Do i have to remove the oil lock from the forks?

[@catalystreactionsbw]

I take it that you are getting the right springs for your weight? The fork springs in the forks I believe were 1.0kg stock, so those should not need to be replaced. What are you getting for a rear shock spring rate and what piston and spring kit are you buying? Setting your oil level in the forks will be very important.

[@mechanictp]

Dave Moss Tuning I think that the stock fork springs are 0.90 and mine have 60.000 km so I think it is time to replace them that's why I am asking you. I will buy fork piston kit pfk 106 and fork springs with oil (it's a kit). For the shock I think that the spring that comes from the factory is 9.5 kg. What springs to choose fro front and rear? And what oil level if I remove the oil lock at the bottom? Thank you and have a nice day

[@catalystreactionsbw]

Yes, remove the oil lock and replace the springs, that all makes sense.

[@mechanictp]

What oil level i must have? I will do them myself tomorrow

[@catalystreactionsbw]

Sorry for the delay. Race week at Sonoma so I am free from the track at last. Set the oil level to 110mm.

[@powpow4033]

hey Dave... What do you suggest to put as a spring rate for a rider that weights 112 kg without gear doing track days intermediate level on a CBR 1000 RR 2004. I was thinking at 10.5 Ktech...

[@catalystreactionsbw]

Via Race Tech's web site, the stock spring was a 12kg/nm which is in the ball park for track intermediate at your weight. 13kg would give you some "growing room" as your skills improved. May I ask where the 10.5kg/nm rate data point came from?

[@powpow4033]

@@catalystreactionsbw I am talking about the front fork springs. Sorry for the confusion. Reading your comment I believe you reefer to the rear spring which is fine from my point ov view. I Have issues with the front. The 10.5N came from a K-Tech dealer in UK.

[@catalystreactionsbw]

@@powpow4033 Ah, okay. Yes, 10.5 makes sense. Have you set the oil level to 120mm to provide assistance against bottoming?

[@powpow4033]

@@catalystreactionsbw i did not. I had a recent sealing replacement and i was not inspired to see the spring stifness.... I am thinking to get it open and take a look without changing the oil. I did fill it up according to the manual with 466 mil or something likee that.... But comming back to the spring stifness... What is your opinion about 10.5 in the front... The only manufacturer that makes atifer springs is racetech but they are in us and i am in europe.... And modification ia required to the spacer... Alsoi am affraid of rebound valve, if is stock, not to be able to slowdown the reboind of such a strong spring

[@catalystreactionsbw]

@@powpow4033 Rather than project the downside, let's see where you end up in settings. You might also go one grade higher in oil (eg 5w to 7.5w) if you find you need to close rebound to far down (1/2 turn from closed would be the maximum). Springs should be fine is they are they same length as the stock ones.

[@scorpiongag]

Dave I have a KTM Duke 390 with preload adjustment at back only.i weigh 60 kg . I have kept it at 7 setting .can u tell me the setting at which it should bounce evenly.i had recently changed fork oil 5 w due to bad dust caps.this is because during riding on uneven surface above 70 I get headshake moderately and it feels as if it might go for tankslapper but it doesn't.i get really scared.its wp suspension on both and back is not serviceable as per manufacturers.the bike is 42 k kms

[@catalystreactionsbw]

The fork oil needed replacing every 8-10,000kms. The shock is a non serviceable unit and should have been replaced at 20-25,000kms. So, the shock is pogoing with that many miles on it when the oil gets hot, so the tank slapper should appear once the shock gets hot. If that is correct you need to get another low miles stock shock to replace it. For your weight I would have the shock on 5 not 7.

[@scorpiongag]

Dave Moss Tuning thanks for reply .btw I shd tell u for rear shock KTM has it at 1 setting for comfort on street.3 to 5 are for moderate tracks..I used 7 at Buddh international Circuit India and it worked ok but I did not have any feel of track...I use the same setting for road and regarding front shock if I put 15 w oil will the valves support it and will it get firm or plush as far as damping because I don't think any other way of increasing damping. For front shock I used your tie method and even on hard braking and cornering I am using only half of shock. I also tried pillion and still it goes to half length.

[@catalystreactionsbw]

Glad you tried different settings. 10w oil will be fine as a replacement with slightly less volume than the shop manual suggests for more fork travel and feel.

[@Deehornet]

Boa noite mestre.. Acompanho seus vídeos aqui do Brasil, seria legal se colocasse legendas neles para facilitar tradução.

[@perrysimpson4906]

Hi Dave love the videos but I still have a lot to learn especially when it comes to what my suspension is doing when riding so I can resolve issues. My question may already have been covered but to be sure: I have a GSXR 1000 K2/K4 hybrid, K4 suspension all round plus k4 swinger - I can barely get to 35mm rider sag with max preload, approx 25mm fork tube left after mixed road ride, with trail at approx 100mm, despite very little compression damping, approx 25% rebound damping, I appear to be hitting the bumps. My impression would be forks cannot compress quickly enough? I am 240lbs in full leathers/gear and ride one up only, single seat only, road riding only - despite above issue very confident about the bends at speed or slow, nice and stable. Are we talking upgrade to fork springs?

[@catalystreactionsbw]

Thanks for the diligence Perry. If you have OEM springs, the preload will make the forks stiffer and with 25% rebound and very little compression, you have no balance between spring and compression. Try 3 lines showing on preload and set compression at 8 clicks out. See how much travel that gives you, then experiment with less preload and more compression while keeping rebound constant.

[@perrysimpson4906]

Thanks for the quick reply, much appreciated. Re OEM springs, I cannot confirm this I have inherited forks, labelled KTEC - previous owner was not sure might have been modified or just serviced, no receipts, the joy of people modifying bikes and not keeping records. Rebound figures now to hand: Forks: Rebound 8 out, of 14, compression 22 out, of 28. Harsh over all bumps stable round all bends apart from bumpiest. Copes well with pot holes, shallow just rises in the road all felt even road patches. When trying to balance front to back pushing down at rear of tank area shock always compresses but forks reluctant to compress pushing wheel forward despite trail 103mm - forks 10mm above yokes.

[@catalystreactionsbw]

You have no compression working at 22 out, so my guess is very strong springs. K-Tech will have records if the parts were sold to a shop or to the previous owner so a little detective work should yield some information.

[@perrysimpson4906]

I cannot call tonight's ride conclusive but followed your advice re preload 3 lines out of 5 and compression 8 out of 28. Not my usual full run but very bumpy road, few slow and fast bends and threw in some heavy braking to get a ball park on fork travel all after a good 30 mins initial warm up stint. Zip tie left at approx 25mm still - bottom out point previously measured/calculated at approx 3mm from casting lower, 128mm fork measured on front paddock stand, 125mm front wheel travel Suzuki spec for model/forks. Strange zip tie result almost no difference. During run added a couple of clicks out on compression to 10 out but barely noticed any change. Tempted strangely to try 4 lines out on preload for next time or does that sound barking?

[@catalystreactionsbw]

If you are hitting the same spot irrespective of settings, I would try to bottom the forks out by hand (forks off the bike) with zero preload and no compression. If you get to 25mm by hand, I would consider removing 50ml of oil from each leg and see if you can get more travel by hand.

[@TwentyTwoThirtyThree]

I have a late 90's Triumph Trophy that I've turned into a naked bike, and I'm looking to go with a stiffer spring. Right now it says stock spring is 0.6kg/mm, and I'm looking to increase to .85kg/mm. Anyone have any advice, or tips when it comes to swapping the springs out?

[@catalystreactionsbw]

Remove spring and spacer and measure total length. When you get the new springs in, measure again and modify the spacer if and as needed. 10w or 15w oil for the forks (based on use).

[@TwentyTwoThirtyThree]

Thanks for the advice! When you say 10w or 15w based on use, what does that mean? And what are the pros and cons of running thicker/thinner oil?

[@catalystreactionsbw]

@@TwentyTwoThirtyThree fork oil weight is the reference for 10w light or slightly heavier15w kzbin.infosearch?query=fork+oil+viscosity

[@catalystreactionsbw]

thicker oil with old model forks = better braking stability and rebound control. Too thick oil creates harshness.

[@TwentyTwoThirtyThree]

Awesome, this has helped a ton! Much love from Canada 🇨🇦

[@dielauwen]

Most Bikers don't know crap about suspension tuning. Here is a place to learn. Question is where do you get alternate springs?

[@catalystreactionsbw]

There are many sources you can go to. Ohlins, KTech, Nitron and KTM have their own range. Race Tech sells the vast majority of springs for suspension businesses. You have many options :)

[@noext7001]

what if you are 60kg and running heavy spring and you can get the sag ?

[@catalystreactionsbw]

If you accurately measured and added static and rider sag together and get 30-40mm for sag, you are at the right starting point.

[@jedigeekbiker]

just put hagon springs in my bandit and I'm having to add the same preload,, which seems I've wasted my time lol

[@catalystreactionsbw]

Oil level in the forks is too low. Bump it by 25cc.

[@jedigeekbiker]

@@catalystreactionsbw Thanks Dave

[@seinfeld11123]

if you bottom out with lots of preload. why not just take out 20% of the preload and you would probably use about 90% of the fork then

[@catalystreactionsbw]

As suspension is dynamic and springs are progressive there is no linear relationship to be used. Similarly we don't ride like robots so there's no given perfect road etc. As such, we "find" what works best most of the time for the ultimate compromise.

[@MackSmooth]

I'm not usually one to complain but I paid for 2 months of Dave's Services about 4 or 5 months ago for my previous bike. I was admittedly busy but there's no information on HOW to utilize the information I paid for.. Truth be told I didn't learn squat. Nothing. 0 And the free videos are just teasers to get you to pay more... Now I can't afford it with the pandemic and am the ww3 bs.. However, now I desperately need help learning how to adjust my showa bpf forks on my new 2010 cbr1000rr... Any advice where I can get FREE assistance that's NOT going to lollygag until I fork out more money I don't have??? Tia

[@catalystreactionsbw]

Thanks for your post. What unique video content and instructions would have been useful to you as a stand alone video?

[@MackSmooth]

@@catalystreactionsbw I appreciate the timely responce. I just am having a hard time understanding which adjustments do what to be completely honest..

[@catalystreactionsbw]

@@MackSmooth Great answer and thanks for your honesty. Here are the steps in sequence and use these words in the search option: lever shapes, sportbike ergonomics, bad handlebars. That will help you with handlebars and levers. Next will be static sag, rider sag, fork bottom out and that will help you understand how to use fork and shock preload. Next will be rebound too fast or slow for the forks and then the shock (2 videos). That will get you through all the fundamentals. If you are still a member, this new course will do the same for you: davemosstuning.com/courses/

[@blairknight7793]

Triumph engineers need to watch this video, Speed Triple 1200 rs, my god its hard, physically hurts your arms from the factory, forks sag 10mm with an 83kg rider. Backed out to the limit, id say its springs and lighter oil on these suckers, how did these fools get it so wrong on a $29,000 bike ?

[@catalystreactionsbw]

I am always curious to see how engineers arrived at springs, valving and settings. Is it based on Triumph's demographics, or other data points? Unfortunately, that information is not available for us to review and gain an insight on.