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Putting 26" Disc wheels on a 29er (Kona Ute) to drop the BB

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Putting 26" Disc wheels on a 29er (Kona Ute) to drop the BB

Old 01-29-16, 04:18 PM
  #1  
Pukeskywalker
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Putting 26" Disc wheels on a 29er (Kona Ute) to drop the BB

Is this crazy?

I've got a Kona Ute I want to use as a kids carrier. Here is my reasoning:

1. The stock kickstand is not safe enough. Wobbles with a light touch.


The 29er rear wheel puts the kids very high off the ground, so center of gravity will be an issue when loading up the 60lbs of baby.

2. The safest replacement kickstand option available is 11.8" (Ursus Jumbo)

Which is about 0.2" shorter than the stock kickstand and leaves the front wheel sitting on the ground (I've been told the ideal utility bike has front wheel 2" off the ground w/kickstand down for loading).

3. 26" disc rims would fit the frame (100mm/135mm)


And could drop the BB and the kickstand down enough to work with the Jumbo.


Also would leave ~100mm pedal clearance from the ground with 175mm cranks


Benefits to 26"...
1. Lower BB for safer stopping (rough math: still a reasonable 11" / 280mm to avoid heelstrikes)
2. Slightly lower center of gravity
3. Kickstand fully functional
4. Option for fatter tires than the 29er rims allow

Negatives:
1. Potential negative effects on handling.


Anybody want to weigh in? The 26" wheels have not been purchased yet.

Last edited by Pukeskywalker; 01-29-16 at 04:22 PM.
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Old 01-29-16, 05:21 PM
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Changing both wheels will leave the geometry (seat tube and head tube angles and wheelbase) unchanged and the trail will change a small amount so the handling shouldn't change dramatically. If you use really fat 26" tires the actual wheel diameter may not change a lot.
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Old 01-29-16, 05:41 PM
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So long as you've still got ample ground-to-bottom bracket clearance, you should be OK. Assuming similar tire width, your bottom bracket will be 31.5 mm or about 1 inches lower, which is a pretty significant difference. If that's too much of a difference, you could make up some of that difference by using fatter tires like HillRider pointed out.
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Old 01-29-16, 06:02 PM
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Originally Posted by SkyDog75 View Post
So long as you've still got ample ground-to-bottom bracket clearance, you should be OK. Assuming similar tire width, your bottom bracket will be 31.5 mm or about 1 inches lower, which is a pretty significant difference. If that's too much of a difference, you could make up some of that difference by using fatter tires like HillRider pointed out.
thanks for doing the math. With 31.5mm looking at roughly 85mm pedal clearance, on a bike I will never lean hard into a turn... I'll give it a try. I can tweak crank arm length to 170 if need be...
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Old 01-29-16, 06:03 PM
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If I may extrapolate a bit in the OP's comments- a kickstand should NEVER be used to support a bike when there's a child on board, NEVER. Andy.
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Old 01-29-16, 06:23 PM
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You might also look at 650B.

Halfway between 26" and 700c.

Used 26" tires and wheels are a dime a dozen, and might be something that is cheap to try. You can get better wheels later.
650B would probably have to be custom unless you find a good Craigslist score.

Post a photo of the chainstays and seatstays. Many bikes have a dimple where the tire is supposed to be. It wouldn't absolutely be necessary, but might limit your tire choices.
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Old 01-29-16, 06:28 PM
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A couple more ideas: Look at some utility bikes like maybe a Mundo or a Dummy to see what bb height designers think is reasonable. You could use 27.5 wheels if the 26ers are too much. At any size you could install narrower slicks to get up to an inch of drop.

i don't think lower CG height has much to do with stability but that debate would derail your thread here and you have enough other good reasons.
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Old 01-29-16, 06:32 PM
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Haha, Clifford beat me to it
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Old 01-29-16, 06:44 PM
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Do some simple math to figure out where the bottom bracket will ACTUALLY end up. Sheldon Brown says that old road bikes traditionally had a bottom bracket height of 10 5/8". I would use that as your lower limit.

Upgrading Older Road Bicycles
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Old 01-29-16, 06:50 PM
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Originally Posted by Andrew R Stewart View Post
If I may extrapolate a bit in the OP's comments- a kickstand should NEVER be used to support a bike when there's a child on board, NEVER. Andy.
THIS !! Very important. Lowering the BB is not going to make a kid in a child seat on a bike noticeably better.

Even just loading a kid onto a bike on a kickstand is dangerous. Trailer is safer.
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Old 01-29-16, 07:31 PM
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Originally Posted by SkyDog75 View Post
So long as you've still got ample ground-to-bottom bracket clearance, you should be OK. Assuming similar tire width, your bottom bracket will be 31.5 mm or about 1 inches lower, which is a pretty significant difference. If that's too much of a difference, you could make up some of that difference by using fatter tires like HillRider pointed out.
You could also consider fitting shorter cranks to gain some pedal clearance if needed, depending of course on what you have now.
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Old 01-31-16, 05:13 AM
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Originally Posted by Pukeskywalker View Post
Is this crazy?

2. The safest replacement kickstand option available is 11.8" (Ursus Jumbo)

Which is about 0.2" shorter than the stock kickstand and leaves the front wheel sitting on the ground (I've been told the ideal utility bike has front wheel 2" off the ground w/kickstand down for loading).
Have you looked at the Haulin' Colin kickstand for cargo bikes? It might help with some of your problems, though I like your idea of 26" wheels.
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Old 01-31-16, 07:31 AM
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"Loading 60lbs of baby?" A kid that big should have their own bike!
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Old 01-31-16, 12:09 PM
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Originally Posted by Andrew R Stewart View Post
If I may extrapolate a bit in the OP's comments- a kickstand should NEVER be used to support a bike when there's a child on board, NEVER. Andy.
Originally Posted by 2manybikes View Post
THIS !! Very important. Lowering the BB is not going to make a kid in a child seat on a bike noticeably better.

Even just loading a kid onto a bike on a kickstand is dangerous. Trailer is safer.
They're uncommon in NA, but there are bike stands intended for such use, and common in Europe. The stand the OP mentioned is one of the best available.


Ursus Jumbo stand
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Old 01-31-16, 12:23 PM
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Originally Posted by Pukeskywalker View Post
Which is about 0.2" shorter than the stock kickstand and leaves the front wheel sitting on the ground (I've been told the ideal utility bike has front wheel 2" off the ground w/kickstand down for loading).
I had a center stand on my Gazelle TP before switching to a traditional rear rack stand. I found it worked best to have it adjusted so the front wheel was as close to the ground as possible without actually putting weight on it, maybe 1/4".
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