Front wheel rubbing against brakes on fast descents

[Danny]

I have 2018 Cannondale Synapse with the original Mavic wheels. Recently the front wheel has started to rub against the Shmano 105 brakes when I descend at speed - which in my case is approx 20mph or above.

The wheel is very slightly out of true but no where near enough to rub against the brake blocks when I have the bike on a workstand. Nor does it rub against the breaks if I am riding on the flat or down short hills. However if I come down a long hill I get a terrible vibrating or rubbing noise starting approximately 45 seconds into the descent. I'm pretty sure it is caused by the wheel rubbing against the breaks as I inadvertently left the quick release mechanism open at the start of my ride on Sunday and didn't get the noise. But as soon as I stopped to close the breaks the noise started.

Could the higher speeds be causing the wheel to flex in some way? Or could it be a sign that there is some more seriously wrong with the wheel?

 

[raleighnut]

I have 2018 Cannondale Synapse with the original Mavic wheels. Recently the front wheel has started to rub against the Shmano 105 brakes when I descend at speed - which in my case is approx 20mph or above.

The wheel is very slightly out of true but no where near enough to rub against the brake blocks when I have the bike on a workstand. Nor does it rub against the breaks if I am riding on the flat or down short hills. However if I come down a long hill I get a terrible vibrating or rubbing noise starting approximately 45 seconds into the descent. I'm pretty sure it is caused by the wheel rubbing against the breaks as I inadvertently left the quick release mechanism open at the start of my ride on Sunday and didn't get the noise. But as soon as I stopped to close the breaks the noise started.

Could the higher speeds be causing the wheel to flex in some way? Or could it be a sign that there is some more seriously wrong with the wheel?

Could be at higher speeds it is making the 'out of true' portion oscillate, get the wheel trued up

 

[fossyant]

Also check tyre seating or for any odd bumps in the tyre. Check bearings.

 

[Sharky]

Google "frame shimmy" .....

A violent vibration at a certain speed.
Has happened to me.
My cause was a tyre sidewall bulging.

The Google search gives other causes and strategies to mitigate.

Good luck

 

[Danny]

Definitely not a tyre sidewall issue. When it first started happening I did get the wheel trued by my LBS who said they got it 99% true but couldn‘t get it 100%.

 

[Ajax Bay]

My first port of call would be to check the front hub. If you apply lateral force to the top of the wheel, is there any movement?
Assume QR.
But if the hub allows play, it'll roll OK in gentle conditions but may generate the symptoms described downhill, with or without braking.

 

[wafter]

Probably also worth inspecting the fork thoroughly for damage; could be that an oscillation is being exacerbated by a weakness somewhere..

 

[fossyant]

New bike.

 

[Punkawallah]

New bike.

“N+1”

 

[wafter]

New bike.

Best get three; just to be on the safe side.

 

[Gillstay]

Check nothing on the brake is loose and and the axle is held well in the fork. Do you have another wheel any where that you could try, or a chums ?

 

[Danny]

My first port of call would be to check the front hub. If you apply lateral force to the top of the wheel, is there any movement?
Assume QR.
But if the hub allows play, it'll roll OK in gentle conditions but may generate the symptoms described downhill, with or without braking.

No movement at all in the front hub as far as I can tell. When I got my LBS to try and true the wheel a few weeks ago they mentioned that one of the spokes was frozen - could that be causing a problem?

 

[Danny]

Check nothing on the brake is loose and and the axle is held well in the fork. Do you have another wheel any where that you could try, or a chums ?

I don't have a compatible wheel but was going to see if I could borrow one. One challenge is that where I live in York there are no hills so I have to cycle for 1-2 hours to find a long and steep enough descent to reproduce the problem.

 

[Danny]

Probably also worth inspecting the fork thoroughly for damage; could be that an oscillation is being exacerbated by a weakness somewhere..

No obvious damage and it was hopefully checked by my LBS when I brought the bike in for a full service.

 

[fossyant]

Check the back wheel !