What Width Tyre Is Best For Cross Country Riding? |

Welcome back to another episode of Ask GMBN Tech, where we try to answer all of your complex, scary, niche, and technical questions about mountain bikes and MTB-related tech!
⏱ Time Stamps 👇
00:00 - Intro
00:19 - I currently have a bike with 175mm crank arms and get a lot of pedal strikes and have issues with manuals, would going to shorter cranks help out? Thinking 165mm. Would 10mm really affect anything, or is it too big of a jump in size?
02:05 - What width tyre is best for cross-country riding?
04:38 - Why do the officials blow a whistle after each downhill racer goes by? It's not the fans. It was during practice I noticed
05:19 - I've been having problems with my shifting, only half of the cassette shifts well, if you use the barrel adjuster chain goes well to the biggest gear but then when going to the smallest cogs shifting doesn't work well, I've already changed cable and cable housing, shifter
06:48 - Why are internal hub gears so uncommon? I know nothing about modern variants, but surely there must be good decently priced ones to mount on MTBs? Less maintenance and wear would be a nice upside to have for sure.
09:12 - Why does nobody remember BOS suspension as much as before considering it wasn't long ago they released a 39mm stanchion enduro fork
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[@gmbntech]

Do you have an MTB Tech-related question for us here at GMBN Tech? Use the hashtag #AskGMBNTech with your comment for a chance to be featured on the channel! 👇

[@billderas3420]

#AskGMBNTech Please note that there is another benefit to having shorter cranks. Besides having the pedals go down less to reduce pedal strikes, they also go up less which reduces knee flexion. Reducing knee flexion at the top of the stroke was an unexpected bonus for me after multiple knee surgeries over the years. Would be interesting for GMBN to do a video on this topic...Maybe with a professional bike fitter present. Cheers!

[@chimps4gimps]

Hardtail Party did a vid or two on trialing different crank length. Worth a look.

[@brian6speed]

shorter cranks also affects your seat height. I had to lower my dropper post which means shorter cranks equals lower center of gravity without making pedal strikes more likely.

[@richardjohnston6688]

​@@brian6speed why would you lower your seat with shorter cranks raises your peddal off the bottom of the stroke. Makes no sense. You have to raise your seat 10mm to get position back to normal.

[@floydblandston108]

Bike fit is criminally neglected- start with Zinn's guidelines and go from there. Beyond that, the sheer number of variables can be confounding, and it becomes like detective work. A bike shop owners wife wanted to quit riding, as she was having progressively worse knee and back problems- this is a very fit woman, a professional dance instructor and dedicated tennis player- but biking was giving her pain. He went right through the obvious; seat/stem/bars/cranks, and even tried a few different frames, but nothing was working. Fortunately, someone observant was out with her on a group ride and noticed she had an odd little kick in the right leg at the bottom of her pedal stroke; they changed her Shimano SPD's out for some Speedplay frog-style pedals and all the problems went away!😉😊

[@rinky_dinky]

shorter cranks for me at least made my lowest gear about a gear harder , so i changed out my chainring from 32t to 30t

[@harcormor]

Hey my question was first! Thanks Anna! I already made the call on doing this and purchased and installed them on my bike about 3weeks ago. It has helped a lot. I think I had my saddle set wrong because I didn’t adjust anything and it fits way better now!

[@Stussy787]

I find a Maxxis Aspen 2.25 on the rear and a Maxxis Aspen 2.4 on the front is my go to tyre choice from spring through to early autumn.

[@exothermal.sprocket]

You two are so pleasant to listen to. Good job!

[@esoxcycles]

A few years ago I chased a case of mis-shifting on half a block for ages, turned out I had mistakenly clamped the inner cable the wrong side of the clamp bolt. Switched it over and shifted perfectly.

[@billblake4029]

Anna and Isaac, the two of you do a really great job together for GMBN.

[@IIISentorIII]

I disagree, Isaac is just horrible...

[@ajack6521]

A buddy of mine is running 2.2 ardent race's on his xc hardtail. Surprisingly works great, even won some races against full sus xc bikes

[@hallstewart]

It was a dilemma to choose between 2.4 (lower rotation weight) and 2.6 (higher volume). I picked a 2.6 for comfort and contact patch on the HT but lower profile tread to reduce drag and weight. It’s less grippy is deep loose/mud but better on hard pack and rock. The main thing is more comfort!

[@ByronWWW]

2.25's on both my XC bikes, rocket rons on the hardtail for winter (not best, but nice getting used to low grip) and then racing ralph/ray combo super grounds for the summer bike which are good all rounders.

[@socas_nic]

Do you have the addix speed and speedgrip compounda or the "performance" compound? Thinking of getting Ralph/Ray combo o ride forest roads mostly, nothing major

[@KoyotBravo]

About the problems with shifting across part of the cassete, I've been there, seen that. It was bent and/or twisted derailleur cage.

[@moss30114]

Seth just did a great video on why internal hubs are not popular. TDLR is that they have a lot of friction and are not as efficient.

[@floydblandston108]

$$$ for Rohloff as well...

[@JulianKent]

The Pinion gearboxes are more suitable to MTBs

[@Prinnydood024]

#AskGMBNTech A question related to the tire width question asked a few weeks ago. Would running a wider front wheel(25mm id w/22.5 rear) but mounting the same tires front and rear have a similar effect as a wider tire in front? I understand that the tire profile for a 2.35 front and rear would be "flatter" up front. Conversely you would be able to achieve a similar profile if you used a 2.25 rear and 2.35 front. Untimely my question is the effects/benefits of said setup? Thanks for all the helpful and informative videos.

[@fra93ilgrande]

2.4, it's so amazing, specially with semi slick like tires like Pirelli's Scorpion Xc rc

[@CritRateDenier]

I personally run 2.25 ikon rear and 2.4 aspen front for racing.

[@campbellclark3458]

Where do punctures start to become a big factor? I swapped my DHR2 to a Rekon and it was great for about... 30 minutes. Then I got a puncture

[@floydblandston108]

Crank length is a 'feel' thing- I tried to put a 5'1" rider into some 165's and she revolted and demanded her 175's back. She was a true spinner and everything, but short cranks threw her off. Testing a SS blind, she chose 180's!

[@brian6speed]

doesn't mean it is the right thing to do, she just made bad decision.

[@floydblandston108]

@@brian6speed- thanks god. Does it matter she was faster with her own choice?

[@brian6speed]

@@floydblandston108 that is called selective bias son.

[@floydblandston108]

@@brian6speed - whatever you're pushing is classic bikeweenie overthink, based on theoretical BS you can't even prove.

[@floydblandston108]

@@brian6speed - if you'd care to preserve your honor; she was a long thigh/short calf/short torso/long arm build on a custom built Ti frame, a long rail saddle, and Time ATAC pedals. With everything set up to Zinn specs, she still preferred (and was faster) on longer cranks and skinnier tires than the 'brotard standard', preferring high pressure skinnies and smooth lines. Find your fault or excuse in the details....

[@AmvC]

@gmbntech what tyres would you go for riding rough roads - asphalt, cobblestone, ...? No loose underground. Continental RaceKing have been working very fine, but i'd like an option in 2,4"x29"

[@TypicalGuy84]

Hmm makes sense. Thanks

[@johnnyrocket1320]

I find a Maxxis 2.25" gives me lower weight, fast rolling and enough traction (Rekons) to aggressively attack technical terrain.

[@johangreydanus6243]

Anna and Isaac nice video but in the video, you said that if you use shorter crankarms(1:29) you have to place your saddle also higher. But that's not right you will lower your saddle because the rotation of the crank is smaller with -10mm it's also better for your knees because you bend them lesser at the high stroke

[@franmcgowan4068]

Nope, saddle raised. A 5mm shorter crank arm puts the pedal at the bottom of the stroke 5mm closer to the saddle. You need to keep the hip/knee angles the same.

[@bikebudha01]

Tire width varies so much there is no hard rule. What type of dirt are your riding on? (hero dirt? loose over hardpack? etc). Is is steep where you ride? How much do you weigh? This one is one that gets negleget a lot. My wife is tiny, 120lbs soaking wet. We've found that wider tires don't dig in at all, as she doesn't weigh enough to make the tires dig in. So for her, 2.0-2.2 is the best range.

[@zbigniewandruszkiewicz7703]

I second that! After many years of experimentation, my wife and myself we arrived individually at our ideal tire size. For me it is 2.1"-2.2". For my wife it's 40-42mm. And we ride the same terrain. How come, why so different, you may ask? I am a XXL bloke, and i usually carry more gear. My wife is a wm M size. If you divide our weights by tire width, we both are at the same numbers!

[@zonoskar]

If you're running 2.25" tires, why not immediately go to 2.35? This fits most modern frames and the difference with 2.25 is not that big.

[@KMWS]

#AskGMBNTech I've treated myself a new Santa Cruz Megatower and it came with asymmetrical rims - what's the reason for that please? If I may add another bonus question please: that bike came with SRAM Guide brakes and the front brake lost some of its braking bite all of a sudden (between rides, while being stored) - I think I've checked everything but I don't know what happened and why - what does spring to your minds could be the reason(s) with my only few weeks old bike please? Thanks for hopefully featuring or getting a reply for these questions and keep up the great work, cheers

[@bruceythomson5490]

rollof hubs a great big pain to service hence not many people use them

[@kornbeck]

@gmbntech - Kindernay makes a 7 speed and a 14 speed hub gears also for mtb.

[@moss30114]

2.4 Recon front 2.4 recon race rear. You can run them in the teens and roll over stuff better.

[@stefanwagener]

The efficiency of internal hubs isn't as good as derailleur gears. Good ones like Rohloff and Pinion have efficiencies above 90% and are getting close to derailleur gears but cheaper hubs like Alfine have an efficiency of roughly only 85 to 90%. That means 10 to 15% of your power is lost in the hub. That is a lot and probably the biggest reason why they are not adopted in sportive bike riding but rather included for city bikes where convenience of maintenance is more important than power efficiency. Classified is only a 2-gear-hub, so you still need a derailleur and the maintenance of 1-by system.

[@chimps4gimps]

How efficient is a ‘normal’ set up when it’s half covered in mud though?

[@stefanwagener]

@@chimps4gimps If the hub-solution also uses a chain, that can get muddy, then there is not much difference, I guess. But with a hub you have the chance to use chain protection (not sure how many MTB riders would do that) or probably to be seen more often in the future (e.g. with the Pinion eBike solution) to use a belt instead of a chain.

[@ravennexusmh]

i love my 165mm cranks, not easy to find (cause i'm cheap) so my trail bike has 165mm XO DH. by gravel bike has 170mm (on sale and i didn't want to pay twice the money for 165mm whiich werent on sale) and my trainer bike has 172.5 road cranks. i'm always searching for 165mm for all of them, or if i can find them the rare as heck sram nx 155mm. i'm 5ft 9by the way.

[@brian6speed]

I'm running the Sram GX alloy 165mm cranks on both my bikes. For $125 on sale for a pair with chainring, it is a great price.

[@erlendsteren9466]

I have a small very smooth trail with no roots and rock where I now and then go as fast as I can on either 44mm, 2,2" or 2,6" tyres. It is very hard to figure out which tyres are faster, and fastest time depends on how clean and strong I was riding that spesific day. But I have a slight feeling the big tyres are cornering better so I guess the largest are faster going down and the skinny faster going up. The big tyres are definitively faster on a 30 meter part with deep sand.

[@socas_nic]

I believe part of it is that the wider tyres give you more confidence hence they are faster in tests. And it sure plays a huge role i wider tyre you can trust into the corners, with lower pressures will grip better. The only scenario the skinnier tyre would be faster is asphalt Which in mountain biking rarely happens.

[@adamweb]

I only knew the answer to the whistle question because Red Bull Bike explained it when I asked on their live chat 😂

[@XCRiders]

Short cranks are terrible for me thought for years I would benefit with shorter cranks, finally tried it out, and heck no can’t hammer as well. 175mm is right for me. Pedal strikes are a matter of technique.

[@ChrisCapoccia]

Complex hub also means that when you bend a wheel, it's a wheel rebuild and more expensive

[@floydblandston108]

how so? Most ig hubs use standard spokes and nipples...

[@troymortimer3487]

#askgmbntech. Less of a tech question more of a test vid. I would love the team to do a timed test of enduro riders wearing shorts knee pads with enduro full face on enduro track, then doing it again with XC kit on the same enduro track. and then do XC track with the same outfits. I’m really curious to see if XC kit of lack of protection really does make a difference to a riders time on different tracks. It’s probably only fair if you get a enduro rider and XC rider in test.

[@Heckisack]

#AskGMBNTech Hi guys, i am currently getting back on the bike after a few years of not riding at all. I still ride my 2011 Stumpjumper FSR, which is obviously pretty outdated in terms of tech and geometry. Right now i am looking into buying an affordable (2000-3000 €) bike with modern geometry that suits my riding style. This means more of a tour-focused style, but with technical descents (i've been on two Alp-Crosses with that stumpy and several multi-day trips through the Black/Palatinate Forest and the Vosges mainly on hiking trails) and steep uphills. I was wondering what i should look out for, since All-Mountain is not really a category any more. Trail seems to be more descent-focused than i might need. So what should i been hunting for? Also, 27.5 or 29? I am 1.78 m and around 70 kg...

[@Blackdevilcar91]

Something like the Giant Stance perhaps?

[@landslide4187]

#AskGMBNTech is there a correct method to tighten and adjust a 2 bolt seat clamp like most dropper posts have?

[@richardjohnston6688]

After working as bike mechanic for 30 years do up both bolts to near snug. If you want your seat up or down at front tighten one and loosen the other wen you get position were you want it make sure both bolts are tight and simple as that. Just trying to help.

[@mark-jx6qi]

#AskGMBNTech i currently have a trek supercaliber with 100mm fork and 60mm shock travel. My strengths are riding up, but not so much down. Will I really feel that more confident on an xc bike with something like 100mm on the back and 120mm and would it be worth getting a new frame or bike? Thanks

[@floydblandston108]

Don't sell the Trek until you try a genuine 'all-mountain' bike. Go to a demo day at a bike park and try one- you may just naturally be more favorable to a pure XC riding style and there's no shame in that.

[@mark-jx6qi]

@@floydblandston108 I don’t have access to any bike parks or demo days unfortunately. I only live on a small island, but thanks for the help. I won’t sell the trek until I’m happy with a new bike

[@JamesJacobson-ov4ps]

2.4

[@feedbackzaloop]

#askgmbntech what was that with Pidcock's ghost shifting during his champion run?

[@uldi1s]

#AskGMBNTech FAT bikes: why doesn't the industry offer HCHT FAT frame designs? Been looking for a long, low and slack fat one and aside from one small manufacturer that hand builds them (steel and at a steep price: KRUCH), there is nothing else.

[@henrybatson8455]

I went to 165mm cranks and I definitely noticed less pedal strikes

[@henrybatson8455]

Im 6foot as well so its not just for shorter riders

[@floydblandston108]

@@henrybatson8455 - depends on your frame and setup. Specialized bb's were usually at least 12mm lower than competitors; riders from other brands jumping on them would complain of pedal strikes, so big s put 165s on a lot of their frames. Voila! fewer complaints....

[@henrybatson8455]

@@floydblandston108 ive got s Nukeproof mega dont know how high the bottom bracket is but i got a lot of strikes before i swapped my cranks out

[@wallyedmonds8199]

I changed from 175 to 165 , worlds better .

[@MaQuGo119]

short cranks give less leverage, so not for me

[@laeljon]

Went from 165mm to 135mm and will never go back...

[@jurekgadzinowski2895]

WHAT? How tall are you?

[@jurekgadzinowski2895]

135mm is like a crank of an 16 inch wheel bike, isnt it?

[@laeljon]

5'0" I tried everything from 170mm to 90mm twenty miles on each length130-135 were my faves...@@jurekgadzinowski2895

[@g.fortin3228]

Anna does a great job she's got the knowledge and the right personality ! And that smile :- )

[@phenofinder9145]

Gmbn cycles through alot of employees... Why?

[@uriteruel]

Mixed size brake rotors... Why don't we use bigger discs at the back since it's the brake we use most of the time thus it heats more? We might need more stopping power at the front and because of the weight transfers under braking, but I feel my front doesn't heat up as much as the rear does #AskGMBNTech

[@feedbackzaloop]

Some manufacturers already do so. Also heat is rather managed by caliper size, while rotor size is responsible for braking force. So it may be even wiser to keep the rotor still smaller, but swap the calipers for 4-pot.

[@jurekgadzinowski2895]

In general the rear brake is used more frequently, but since the weight is being transfered to the front while braking, the front brake usually has to brake harder

[@chimps4gimps]

Physics. It’s the exact same reason why cars often have discs at the front and drum brakes at the rear.

[@feedbackzaloop]

@@chimps4gimps cars normally do not operate in same conditions as MTBs and their brake bias is fixed. When we come to special vehicles and racing cars, brakes differ from usual too. Your comment is superficial and doesn't get into the actual physics.

[@floydblandston108]

@@feedbackzaloop- you are suffering from bikeweenie brain cramping. Try some other hobby until your argument begins to seem meaningless.

[@floydblandston108]

....Part II of the 'U Need Fat Tires' fallacy; SCHWALBE put out a bunch of BS studies (and Specialized joined right in) *proving* (blahblahblah) that buying fatter tires- and the frames to fit them- would add inches to your pecker, or whatever their rationale was. NEW bikes must be sold, and FAT TIRES were a must if you wanted to out-choadify your rivals. Tinker Juarez and I remain unimpressed...

[@grahampye2314]

knee over pedal still being mentioned as a thing? I thought that was debunked ages ago

[@TundeEszlari]

I love your videos, can I get a comment heart?

[@Jacob99174]

❤

[@floydblandston108]

What a strangely needy little character quirk you have...🤔

[@IIISentorIII]

5 seconds listening to Isaac make me skip the entire video...

[@B_r_u_c_e]

You adrenaline junkies have no concept of what cross country biking is. It entails using the pedals (not gravity) to propel forwards across terrain that is mostly flat, with little concern for high speed cornering. And there is no jumping.

[@EMTB17]

Neil and Doddy only. Fire everyone else.

[@floydblandston108]

See, now I'd like Martyn in there with them.

[@jurekgadzinowski2895]

Pretty much agreed

[@floydblandston108]

@@jurekgadzinowski2895 - I don't find Anna problematic, do you?

[@phenofinder9145]

Doddy isn't with gmbn anymore. Things got weird before he left also. We never got clarification on wtf really happened

[@jurekgadzinowski2895]

@@phenofinder9145 What? Really? When did he left?