Forum menu
Running 26" wh...
 

[Closed] Running 26" wheels in a 650b frame. Any issues with doing this? (death content)

Posts: 0
Free Member
Topic starter
 
[#6792529]

I'm looking at a new frame which only comes in 650b. I'll be buying the frame and a 650b fork to go with it. I'd rather run my 26" wheels as I have a load of tyres, some of which aren't even available in 650b yet.

BB height of my 26" frame is 335mm

BB height of the new 650b frame is 345mm

Front and rear travel of the frames are basically the same.

Taking into consideration the 12mm difference between the radius/BB height, swapping to 170mm cranks will get my a tiny bit more clearance, so I'm assuming everything will be fine and dandy?

I'm assuming the trail will be slightly different between the forks, but is there anything else I've overlooked? (Trails not coming alive has been factored in)


 
Posted : 19/01/2015 8:17 pm
Posts: 0
Free Member
 

I only hope you have life insurance cover !


 
Posted : 19/01/2015 9:06 pm
Posts: 31089
Full Member
 

Check the BB drop rather than height… height means little when comparing just frames, because it depends what build the bike is. No?


 
Posted : 19/01/2015 9:18 pm
 JoeG
Posts: 0
Full Member
 

Surely the humiliation that you will endure from the on-trend 650b crowd will make life not worth living and death very attractive in comparison! 😆


 
Posted : 19/01/2015 9:23 pm
Posts: 0
Free Member
 

The trails will die, so will kittens.


 
Posted : 19/01/2015 9:24 pm
Posts: 0
Full Member
 

Unless the wheels/tyres say "these are not 650b" in massive letters I doubt ANYONE will ever notice.


 
Posted : 19/01/2015 9:28 pm
Posts: 251
Full Member
 

I've got 26" wheels in a 650b fork and frame that claims to allow both.

I've not died yet. Although I have to confess I haven't actually ridden it yet either.


 
Posted : 19/01/2015 9:30 pm
Posts: 14169
Full Member
 

You'll be fine. What's the old and what will the new be?


 
Posted : 19/01/2015 9:36 pm
Posts: 0
Free Member
Topic starter
 

Check the BB drop rather than height… height means little when comparing just frames, because it depends what build the bike is. No?

Didn't think BB drop would make much difference, other than stability.


 
Posted : 19/01/2015 9:38 pm
Posts: 14484
Free Member
 

The trails will die, so will kittens.

And puppies, whole sacks of them.


 
Posted : 19/01/2015 9:43 pm
Posts: 0
Free Member
Topic starter
 

You'll be fine. What's the old and what will the new be?

Old is a Stumpy Evo, new is a Foxy.


 
Posted : 19/01/2015 9:51 pm
 br
Posts: 18125
Free Member
 

[i]Old is a Stumpy Evo, new is a Foxy. [/i]

Ride the Evo until you've worn out the tyres?


 
Posted : 19/01/2015 10:24 pm
Posts: 828
Free Member
 

I run 26" wheel in my 650b fork and am still here and a 26" on the back as it is a 26 frame

Cat is also still around 🙁


 
Posted : 19/01/2015 10:31 pm
Posts: 0
Free Member
 

That's what I ride^

I've got a 160 fork up front on a 140mm Lapierre and it was pretty awful at full travel but offset bushes make a difference. The biggest being - it feeling quicker in 130mm travel up front, which is around 4mm higher than the fork that came with it. I tried 650 xc wheels in it before the offset bushes but I nearly fell off it on the first turn during a carpark test so decided against splashing out. Looking forward to having a 650x2.8 on a wider rim up front as soon as a certain tyre comes into stock.


 
Posted : 19/01/2015 10:41 pm
Posts: 14169
Full Member
 

Old is a Stumpy Evo, new is a Foxy.

The Foxy has a lot more anti-squat than the Stumpy so should be less prone to strikes when pedalling.


 
Posted : 19/01/2015 10:51 pm
Posts: 0
Free Member
Topic starter
 

The Foxy has a lot more anti-squat than the Stumpy so should be less prone to strikes when pedalling

No idea what anti-squat is, but it sounds cool, so it must be good.


 
Posted : 19/01/2015 10:59 pm
Posts: 14169
Full Member
 

No idea what anti-squat is, but it sounds cool, so it must be good.

Exactly. 😀

P.S. It's the difference between a frame that bobs up and down when you pedal (unless you add lots of damping/platform/lockout on the shock) and one that puts all your efforts into going forwards.


 
Posted : 19/01/2015 11:09 pm
Posts: 0
Free Member
Topic starter
 

P.S. It's the difference between a frame that bobs up and down when you pedal (unless you add lots of damping/platform/lockout on the shock) and one that puts all your efforts into going forwards.

Ah marketing guff for pedal bob 😆


 
Posted : 19/01/2015 11:19 pm
 igm
Posts: 11873
Full Member
 

Almost as bad as running 1.8" tyres when the frame was designed for 2.4" ones - that'd make a similar difference to wheel radius


 
Posted : 19/01/2015 11:20 pm
Posts: 15458
Full Member
 

Check the BB drop rather than height… height means little when comparing just frames, because it depends what build the bike is. No?

Hmmmm, OP's thoughts make perfect sense to me.

BB drop remains the same as it's measured relative to the axles, drop the axles 12mm, drop remains the same BB height reduces by 12mm also....

This is all static, of course suspension sags, reported numbers are simply a loose indication of how a bike might ride.

Marginally smaller wheels will be fine, give it a whirl...


 
Posted : 19/01/2015 11:22 pm
Posts: 14169
Full Member
 

Ah marketing guff for pedal bob

No, engineering guff - if it was marketing guff you'd read about it in reviews...


 
Posted : 20/01/2015 12:02 am
Posts: 0
Free Member
Topic starter
 

Engineering guff, even better!


 
Posted : 20/01/2015 12:06 am
Posts: 0
Free Member
 

I'm thinking of doing this to save my trail wheels on an uplift to Antur, which can be pretty hard on wheels and tyres! My cranks are 170mm and pedals only 12mm thick, so should be fine?!


 
Posted : 20/01/2015 8:06 am
Posts: 31089
Full Member
 

Quoted BB height is useful for comparing bikes, but depends on wheels, tyres, forks, sag etc, so if working out what your build will be like BB drop is the place to start, as it doesn't include all those variable that don't apply in the same way to your build with different choices being made. BB height is ultimately the thing that matters in this case, I agree that it is ultimately what you are trying to work out, but comparing two sets of manufacturers BB height figures is fruitless when comparing frames rather than bikes, whereas their BB drop measurement methods should be a bit more consistent.


 
Posted : 20/01/2015 11:57 am
Posts: 0
Free Member
 

You are going to have a low BB but apart from that it will be fine.


 
Posted : 20/01/2015 12:02 pm
Posts: 0
Free Member
 

You'll be fine, some frames are made for both sizes so it obviously can be done...didnt some bloke at last years mud-fest Megavalanche put 26 inch wheels in his 650b for better mud clearance and do rather well?!


 
Posted : 20/01/2015 12:05 pm
Posts: 0
Free Member
 

throw all your numbers in and what you come out with is a BB that will be about 4mm lower than you currently have BUT the new Mondy frame IS designed not to squat under load so much. The result? "Pretty ****ing close to what you have now" So close in fact that I doubt you would even notice it at all. Forget the frame clearance on rocks for a minute though and tell me honestly, that you are worried about hitting your BB? Honestly??? I'd be more worried about smashing the teeth off my chainring which sits another 70mm lower than your BB. Have you thought about it that way before with your old bike? If not, dont worry about the whole situation because it's obviously never been an issue.

Cats and dogs will be fine, birds will still tweet and your Mrs will undoubtedly come home with yet another pair of shoes because you have a new bike... take the cost of the shoes on the chin and be content with 'getting one over' on the world. The Geometry of the frame will be unchanged, you'll just be half inch closer to the ground at the axle points from where the designers intended... and they wont give a sh*t.


 
Posted : 20/01/2015 12:19 pm
Posts: 806
Free Member
 

You'll be fine, some frames are made for both sizes so it obviously can be done...didnt some bloke at last years mud-fest Megavalanche put 26 inch wheels in his 650b for better mud clearance and do rather well?!

Yeah - it was Karim Amour, European champion. He and quite a lot of the Frenchies did!


 
Posted : 20/01/2015 12:35 pm