Dirt Bike Suspension vs Chassis EP.2 | Sag and Springs EXPLAINED

We're back! Episode 2 of Dirt Bike Suspension vs Chassis tackles rider sag and springs. Be sure to subscribe to the Ride JBI KZbin channel for more Race Recaps, JBI Spec, or Shop Talk Episodes!
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Timestamps:
0:10 - Intro
1:51 - What is Sag?
4:58 - What is Spring Preload?
7:44 - KTM Sag
10:25 - Real World Example
17:36 - Chassis vs Suspension Adjustments
20:24 - Q&A

[@bdubz01]

The more i watch, the more i learn and the more confused i get!!!! Thank you for sharing you guys are awesome!

[@RideJBI]

Thank you! We're stoked you're learning through our videos series. Don't hesitate to reach out with any questions you may have via e-mail or phone. [e-mail] 480-269-5585

[@darrenmabe5838]

best semi-technical explanation of overall handling I have ever watched - thank you!

[@LetRRoll]

Please don’t forget about enduro and hard enduro riders. If you have specific tips for those disciplines, please share. Thanks guys!!

[@RideJBI]

You asked (along with a few others) and we shall deliver. Stay tuned!

[@yt310yt]

@@RideJBI yes def interested in enduro and single track

[@jaywilburn1239]

Great series! Never figured out the suspension equation when riding in my teens-20’s but now in my 40’s, I’ve focused on getting educated and seeing the results on the trail. I’d be interested in seeing a video on how fork fluid levels affect the stroke, impact on compression, rebound and ride overall. I’ve never really played too much with the fluid levels and would like better understand that variable a bit more. Thanks!

[@RideJBI]

Thank you! We appreciate you tuning in. Are you spying on me (JB)? Just kidding. I say that because that is the topic of the next video. Oil volume!

[@jaywilburn1239]

@@RideJBI Hah! Sweet! Looking forward to it!

[@tvelaify]

I am getting a lot of values from your videos. Keep them coming

[@RideJBI]

Thanks for tuning in!

[@whitehollywood6447]

Can you do a whole video on hard enduro setups .. not many videos out there covering the subject. Thank you 🤙🏻

[@RideJBI]

Yes we can. We're getting a lot of requests for hard endurance suspension/chassis setup tips. With that being said, it's on the schedule. Stay tuned!

[@whitehollywood6447]

@@RideJBI while doing hard enduro topic please add in endurocross setups and the difference between a hard enduro setup and enduro cross setups. 🤙🏻

[@justinfritz3635]

Keep these vids coming

[@leethomas556]

Thanks guys! Is "slap down characteristic" a thing?

[@bwhaskell]

Higher spring preload is also more difficult to initiate initial compression. If I have a 6.0kg/mm spring with 0 preload, it would take 6kg to compress the shock 1 mm. If I had preload set on that same spring at 5mm, I would need 30kg of force just to get the spring to compress. I have tried a lot of different suspension setups and for motocross I tend to prefer a little higher than normal spring rate with less preload. It makes for a more lively suspension setup, and when paired with appropriate valving, makes for a very confidence inspiring setup. Also, stiffer springs tend to absorb energy better, so in the shock that leads to a cooler running shock.

[@RideJBI]

Thanks for tuning and the comment. You are spot on and correct with your summary of spring rate and preload. Thanks for sharing your experience and insight on this.

[@korabeats_]

I agree 100%. I ride single track and enduro, and even then prefer a stiffer spring rate. I feel it just handles the large hits better while still remaining relatively soft/smooth for the faster choppy stuff with running less preload.

[@manny.9273]

Love this series, sending my rmz450 suspension out to you guys, cant wait!

[@1176hambone]

Great discussion....Moving the ball forward in understanding of chassis and suspension concepts for riders!

[@RideJBI]

That's the goal! Thanks for tuning in

[@vinceseyb2640]

Static sag like you say gives a great reference to preload. Unfortunately with WP you have that massive 35n/mm top out spring which fudges the static numbers. It also has a weird effect on spring "rate" through the first 18mm of of shock travel (50mm of wheel travel) Most of the time the right shock spring will end up with 7-8mm preload to achieve the right static and race numbers. Preload effects rebound significantly and most importantly how the bike behaves when you come off the throttle.

[@RideJBI]

Agreed! Those WP top out springs (especially on the Trax shocks) can make setting spring preload a little more involved compared to a shock with a smaller or no top out spring such as a KYB.

[@vinceseyb2640]

@RideJBI that's why I try to convince most people to remove them in the wp or showa units. I then run no cross over in the rebound stack, use a rebound separator valve and run a more open rebound clicker setting. As you've mentioned it's all about managing pressures and most importantly getting the damper to transition quickly at the end of the compression stroke and beginning of the rebound stroke without ending up with a damper that wallows. Have you tried your new WP adjuster pistons with the KYB main piston in the WP units yet? I can guarantee it'll put the icing on the 🎂 Great videos

[@RideJBI]

@@vinceseyb2640 That is unique setup. Thank you for sharing.

[@Vurpvarning]

Great stuff, keep it coming!

[@robinbartling7305]

Awesome video series. Thanks for the knowledge!

[@Tukball]

Fantastic video, i have been trying to find really technical videos on suspension and chassis tuning and a lot of stuff out there is just not really in depth. I want to understand quite literally everything about my bikes suspension (2024 KX450) so i can make educated decisions on chassis or suspension changes on the fly. My goal one day is to have the tools to do my own valving and service work and not do a butchered job.

[@RideJBI]

Hey there! Thanks for tuning in and dropping a comment. That's the entire goal of this video series, to provide in depth technical information on suspension and chassis tuning. We're about to film episode three, stay tuned!

[@EricCogburn]

I’d be interested in hearing how you approach testing. Do you prefer to “bracket” settings by going really far in one direction with the clickers, then really far in the other direction and then see which end of the spectrum feels better? Or do you start in the middle and tweak one way or another? It would be cool to see a graphic of what pro tuners use to document feedback at the track-like a photo of whatever log you have in your notebook (or whatever you use). I feel like most consumers don’t have a formal testing process-they just randomly turn clickers and hope they stumble on something that works.

[@RideJBI]

If it is a brand new stock bike we start with the stock settings. Ride the bike (myself) along with other riders as well to get a good sample of feedback. Based on that will make some track side adjustments while recording down the information. The adjustments will vary based on rider feedback and experience. It is important to note the track or trail conditions and if those conditions are influencing the suspension more then normal. I like to keep the bike stock for a while and ride various tracks and the same track in different conditions to learn what is consistent and inconsistent in the bike setup. In a future video this will be a great topic so please keep tuned in.

[@Pheedub]

Love this stuff.

[@motoxposse]

Question regarding moving forks up or down in the clamps. Let’s say you want better or faster steering in the slow technical stuff so you move the forks up in the clamps, should you reset your sag? Will resetting the sag off set the fork adjust up in the clamps?

[@RideJBI]

Good question. In your case I would start with the fork height. Adjust as necessary. And if the fork height adjustment was not enough of a change then I would look into adjusting sag as well to compliment the fork height adjustment.

[@bradmfrost]

Awesome, thank you

[@raymondharold5973]

My grandson races a GAS GAS 65 2024 we have we come value forks they have limited spring choices currently running the stiffest offered he weighs 120 lbs wo- gear he’s only 8 yrs old but really fast the air fork was harsh when we had to run 3.4-3.5 Bar to get some hold up. So the cone valve was what we went with the action is good but to get the hold up and balance we’re all the way in on the preload adjustment and 1 click from full stiff on the compression adjustment. We races Moto getting it safe for him is the most important thing he’s been racing since 5 yrs old and getting the Cobra 50 & 65 to work well was easier we used gold valves and could get proper spring rates. Do you have a suggestion for spring rates F&R even if we need to have some made by cannon race craft. I know he’s heavy for a 65 but he fits in pretty good ❤

[@RideJBI]

Hello! Thank you for watching and the comment. Ride JBI does not have any experience with the mini bikes. Our testing and development starts at the 85cc bikes. While I am not able to speak from experience I can agree with you that spring rates are important. You are on the right track. Cannon Racecraft is a great source for custom springs. I am unsure of what spring rate to recommend. I would start by speaking with Cannon to see what spring rates can be made for that fork and shock.

[@mickcain7397]

Do all dirt bike springs have a progressive spring rate?

[@RideJBI]

Commonly the fork springs and shock springs are linear in spring rate. However the overall effective spring rate meaning accounting for the main spring, pus air volume / pressure increase, and pressure spring contribution results in an overall effective spring rate that some what starts off linear but ends progressive.

[@Hammy56]

Are you measuring sag in full gear?

[@RideJBI]

At the track yes. At the shop customers usually don’t have their gear but we are able to account for lack of gear weight when setting sag.

[@kostasadams4457]

hi i have 25 ktmsxf 250 adamo edition i change my rear spring to 36n im 57 kg and i thing i need more soft spring whats your opinion(motocross and scramble use)

[@jcbenson01]

Would you mind sharing Anthony’s weight and skill level? Just for a little more context since I ride the same chassis as him? Thank you.

[@RideJBI]

Hi there! Anthony is 5'7" and weighs 150lbs without gear. He rides at an advanced level

[@jcbenson01]

@@RideJBIthank you for replying. I was second guessing myself because I find the 42 and even the 45nm to be soft for me and I settled on the 4.9kg (stock linkage). But I’m right at 200 in gear. So your info is helpful. Thank you. 🍻

[@richyoung409]

It's suspension...it's always suspension! It's all your fault that I suck so bad...hahahahaha! Love you boys!

[@RideJBI]

How dare you! Hahaha. 😂

[@enduro-parts-aus]

Very interesting

[@justinthomas27]

Did any of you go to MMI? And do you recommend going?

[@RideJBI]

Neither of us attended MMI. I (JB) attended ASU in Arizona and had many friends that attended MMI. My fiends all had a good experience and learned a lot at MMI. I was fortunate to work with and be mentored by many great mechanics and engineers while coming growing up. The mechanics helped me with the hands on bike work. The engineers helped me understand and appreciate the fundamentals of suspension.

[@MatthewBurgess25]

What is Anthony’s height and weight?? On a 42 rear spring?

[@RideJBI]

Anthony is 5'7" and 150 lbs without riding gear

[@B.LanglaisCT203]

I have a 22 fc 450 stock suspension not valved run the keefer testing settings and play with the clickers to try and get it right but it beats me up bad to get it to not bottom on hard landings and being the 450 I tend to OJ the shit out of most tables at the track and my wheels take the brunt of it just trying to see how if any way to make this better I ride moto am 5’10 170lbs any info would help

[@RideJBI]

Hi and thanks for the comment. As you are finding out the clickers are limited in their tuning potential. Only so much can be achieved with the clickers and air pressure. Great job making the adjustments yo have so far. The next step to further improve the perform would be to have the suspension revalved.

[@weStayModest]

I just switched from being a lifelong 4t guy to a 2t and my front wheel always feels like it’s floating, I never feel like I’m connected to the ground anymore like I did on my previous bike. Is this synonymous with 2t bikes or is this a suspension issue. I checked my sag and it’s at 105mm in full gear, I set my clickers at the mid way point and I’ve been adjusting them but I never feel planted. I’m 185lbs fully geared I stand a lot and I’m 6’2.

[@BikesandBlickeys]

Sounds like lack of engine braking pushing the front end into the ground.

[@weStayModest]

@@BikesandBlickeys yes my thoughts exactly so I’ve been trying to give a little front brake in the turn to keep it compressed

[@enduro-parts-aus]

Slide your forks up in the triples to put more weight on your front end Thats what i do on my 2t

[@weStayModest]

@@enduro-parts-aus I did it helped but it’s definitely a different feel opposed to the 4t. I will say I still “send it” and haven’t crashed so it holds I just don’t feel comfortable. That same feeling in the front on my 4t meant the front was about to wash out I’ve really been focusing on keeping my weight in the front and giving light front make in the turn.

[@RideJBI]

This would be a great video topic. Yes the engine type (2T or 4T) does have a big influence on how the bike feels. Especially as the engine displacement increases, this applies to both engine types. What you are experience is likely a few things all happening at once. First the difference in engine personality. Secondly, I am unsure of the bike models you are reference but likely the chassis and ergos is unique to each bike. Thirdly likely the suspension hardware and/or settings are different as well. In combination this will make for a much different riding experience.

[@Joe-pb3lx]

im kind of mad......40 years ago nobody gave away suspension secrets like spring rates and sag......im 65 now and understand what its all about......i knew something wasnt right when i rode back then but i didnt understand it.......kids these days have it so good if they know enough to watch these kind of videos and ask questions at the races.....i used to race a lot at southwick in my 20's and everything was hush hush......my 1984 RM125 could of used stiffer fork springs, would of made for a more enjoyable ride and maybe i could of won a race or two.....lol

[@RideJBI]

We appreicate you watching the videos and tuning in! More to come!