Crank sizes for Road 29ers

Recently I changed the cranks as an experiment on my Nimbus 29er from 125 mm ProWheels to 114 mm Quax. I was really surprised about the difference the change made. The flywheel effect is fantastic and it seems I roll along quite easily at or over 8 mph and I’ve been able to sustain short spells of 12 mph. Hill climbing has not been adversely affected; just took some getting used to.

I was wondering how far the benefit goes. Has anyone tried 102 or 89 mm cranks on a 29er? At what point does it become unrideable?

A friend of mine has 89mm’s on his 26" with a 48 spoke wheel and GB4 handles. They’re not too bad for hills actually but I’m used to riding a 29 with 112mm cranks or my 36er with 127’s. The 29 could still be ridable on 102s

I bought my 29er with 125mm cranks on them and quickly changed them for 110s. It transfromed the ride dramatically, and my cruising speed is now around 10mph. (I’ve seen 13mph on my gps unit, but know I’ve been faster… I’d rather look where I’m giong at higer speeds though!)

I’d love to try out 102s, but for rush hour in Central London I’m not sure they’ll be all that suitable.


ive tried 89s on a 28", decided here was no speed advantage over 114s and they are consideraby harder to mount and ride on

I’ll probably buy 102’s for my 29 when the moment of truth comes to change my 125’s to 110’s on my 36" wheel…I’m hoping for the best when that happens in a few weeks.

I am constantly using 114 on a 29 for trails, 102 are possible for smooth bike path, I have 89 too but unable to control those.
prefered size: 114

Brian MacKenzie made 40mm cranks for his Coker in the movie “Training Wheel Not Required”.

It was crazy looking, almost looked like a 36" BC Wheel.

Yah, I thought that was pretty fun to watch, I was going to buy some 50mm cranks from Schlumpf to try on my coker but he wouldn’t sell them :< I know Yuto Ando uses 50mm cranks on his 29er :wink: Ryan Atkins uses 80mm, I use whatever cranks I’m not running on my coker at that moment (usually 90mm, using 80mm on coker atm).

I experimented a bit with shorter cranks, but in the end I stuck with 125s on mine. Once you learn to spin with them you can go pretty fast. I averaged 12.99mph on an 8 mile commute once on the 125s.

Funnily, I like 110s on the coker.


I use 102s for racing or cruising on my 29" I have also tried a pair of homemade cranks about 55mm long on there. Those were pretty useless.

But mostly my 29" has a MUni tire on it, and currently a pair of 160mm cranks for the trails. These are maybe a little long, now that my Wilder has 150s on it…

My 11 year old son reduced the crank length on his 29" gradually over the past year. He started of with 114mm, then 102mm and is currently down to 90mm cranks.

WIth the 90mm cranks he is now faster than me (Coker with 125mm).

He rides mainly on roads. When we do short unicycle trips on the weekends and I involve hills in the route I will always get complaints from him. If it is flat, I only see his back :roll_eyes:

WIth 90mm cranks he can still idle, ride one-footed, ride backwards

I think, it is those short legs that enable him to handle those short cranks though :stuck_out_tongue:

I ride 28s (700c x 23 mm and a 700c x 28mm) on the road and easy cross country. This has less flywheel effect, and takes more moment to moment control instead of relying on momentum.

110 is a good versatile crank size. 114 is almost identical, but gives marginally more control.

102s are easily rideable for cruising. I went right down to 80mm for a short while and made quite a splash:

Once you aren’t sure you can stop safely, you lose top speed. Once you have to slow down for the tricky bits, you lose journey speed. If you can idle, then the smallest size of cranks you can confidently idle is a good starting size. Super short cranks are great fun, but you’d do better to learn to go fast on slightly longer cranks, rather than relying on short cranks and losing out on hills and rough stuff. 110-114 highly recommended.