Can I put 650b wheels on my Giant Defy?

Discuss light weight issues concerning road bikes & parts.
Post Reply
Mort
Posts: 18
Joined: Sun Dec 03, 2017 5:02 pm

by Mort

I just built a new TCR so I want to turn my 2017 Giant Defy advanced pro 1 size M in to a gravel bike that I can ride in the winter when it snows. I’m going to make the switch to 1x and was wondering if I could put some 650b wheels on so I can use bigger tires. The biggest I can fit right now are 28mm maybe 30. Has anyone done this? Or know if it’s possible? Thanks.

bm0p700f
in the industry
Posts: 4708
Joined: Sat May 12, 2012 7:25 pm
Location: Glermsford, Suffolk U.K
Contact:

by bm0p700f

You can if you accept a smaller rolling diameter. You won't get a 42mm tyre in there. Waste if time.

by Weenie


Catagory6
Posts: 338
Joined: Thu Feb 09, 2017 2:36 am

by Catagory6

bm0p700f wrote:
Tue Feb 12, 2019 4:05 pm
You can if you accept a smaller rolling diameter. You won't get a 42mm tyre in there. Waste if time.
Using a tire that WILL fit will lower the bottom bracket, causing pedaling / cornering issues

You might be able to compensate by getting a drastically shorter crank arm.

User avatar
kman
Posts: 1117
Joined: Wed Jul 13, 2005 10:51 am
Location: Sydney, Australia

by kman

You'll probably get the desired effect at the front but not on the rear. The way the chain stays pinch in limits the tyre size - even if you drop to 650b. Measure the gap about where the braking surface of your 700c rim sits. Thats (very) roughly where you need the width for a 650b tyre to sit.
You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer.
-- Frank Zappa

NickJHP
Posts: 223
Joined: Wed Feb 14, 2018 2:22 am
Location: Canberra, Australia

by NickJHP

Catagory6 wrote:
Tue Feb 12, 2019 6:26 pm
bm0p700f wrote:
Tue Feb 12, 2019 4:05 pm
You can if you accept a smaller rolling diameter. You won't get a 42mm tyre in there. Waste if time.
Using a tire that WILL fit will lower the bottom bracket, causing pedaling / cornering issues

You might be able to compensate by getting a drastically shorter crank arm.
As mentioned, the gap between the chainstays will be the limiting factor in the tyre size you can fit. I've converted a couple of frames from 700c to 650b - a Litespeed, where the bowed-in chainstays meant that I could just run a 32mm 650b tyre with very minimal clearances between the stays, and a Merckx Mourenx that my wife rides, which has much better clearance between the chainstays - I can fit a 35mm 650b tyre and still have 3-4mm of clearance each side.

On the Litespeed, which had 76mm BB drop and 170mm cranks, it was possible to ground a pedal on the converted bike when cornering fast and pedalling. On the Merckx that's not been a problem, as the BB drop is 5mm less and the 165mm cranks are 5mm shorter.

Mort
Posts: 18
Joined: Sun Dec 03, 2017 5:02 pm

by Mort

I appreciate the reply’s, and it looks like I’ll be getting the new Revolt after all. I was hoping to make due with the Defy because the trade in value is less than a third of what I paid for it a year and a half ago. But, 28mm tires are doing nothing for me in the snow. Thanks for the input.

by Weenie


Post Reply
  • Similar Topics
    Replies
    Views
    Last post