Wheel flex and tire rubbing

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Wheel flex and tire rubbing

Postby Davetdf » November 27th, 2016, 12:25 pm

Hi,
Just have a question about tire-clearance and wheel flex.
I bought a brand new set recently which included a rear carbon flo 60.

I put 25mm conti tires on them; the rear wheel has about 1.5-2mm clearance to the chainstay on each side. I went on an initial ride with no issues, but last week I was on a ride and one side was rubbing significantly - causing very stark streakmarks on the tire. Off the bike, I'm actually able to "bend" the tire into the chainstay with my bare hands without too much force. Is this normal for the wheel to flex this much? I understand I may need to downsize to 23mm but I'm worried that the issue may be more serious with the wheels ability to flex this much... these are brand new wheels so I'd rather know for sure if this is normal for a few milimeters of flex, or if the wheels' dish or spokes may be faulty?
Davetdf
 
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Joined: November 27th, 2016, 10:11 am

Re: Wheel flex and tire rubbing

Postby Chris Thornham » November 29th, 2016, 1:01 pm

Davetdf wrote:Hi,
Just have a question about tire-clearance and wheel flex.
I bought a brand new set recently which included a rear carbon flo 60.

I put 25mm conti tires on them; the rear wheel has about 1.5-2mm clearance to the chainstay on each side. I went on an initial ride with no issues, but last week I was on a ride and one side was rubbing significantly - causing very stark streakmarks on the tire. Off the bike, I'm actually able to "bend" the tire into the chainstay with my bare hands without too much force. Is this normal for the wheel to flex this much? I understand I may need to downsize to 23mm but I'm worried that the issue may be more serious with the wheels ability to flex this much... these are brand new wheels so I'd rather know for sure if this is normal for a few milimeters of flex, or if the wheels' dish or spokes may be faulty?


I'll start with saying that 1.5-2mm of clearance is a small amount of clearance. Additionally, 25mm tires often to not work on specific frames. I'm not sure what frame you are using the 25mm tires on, but more than likely frame incompatibility is the issue. As an example, I have Cannondale Super Six Evo and I can't run 25mm tires on that frame without significant rub.

The bending the wheel with your hand test is also not a good test to determine how flexible a wheel is. This is because the frame is also bending during this test, and the force from the road is not applied to the wheel where you are bending it with you hand. Any wheel can be made to bend into a frame with your hands. And as I mentioned, often times it's the frame bending, not the wheel.

My best advice is to swap to a 23mm tire. I'm quite certain that all of your issues with rubbing will be fixed.

I hope that helps,
Chris Thornham
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