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Can I put 650b wheels on my Giant Defy?

Posted: Tue Feb 12, 2019 3:57 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.

Can I put 650b wheels on my Giant Defy?

Posted: Tue Feb 12, 2019 3:57 pm
by Weenie

Re: Can I put 650b wheels on my Giant Defy?

Posted: Tue Feb 12, 2019 4:05 pm
by bm0p700f
You can if you accept a smaller rolling diameter. You won't get a 42mm tyre in there. Waste if time.

Re: Can I put 650b wheels on my Giant Defy?

Posted: Tue Feb 12, 2019 6:26 pm
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.

Re: Can I put 650b wheels on my Giant Defy?

Posted: Wed Feb 13, 2019 4:07 am
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.

Re: Can I put 650b wheels on my Giant Defy?

Posted: Wed Feb 13, 2019 5:08 am
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.

Re: Can I put 650b wheels on my Giant Defy?

Posted: Wed Feb 13, 2019 12:28 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.

Re: Can I put 650b wheels on my Giant Defy?

Posted: Wed Feb 13, 2019 12:28 pm
by Weenie