FinanceGuy

At speeds of 25+mph (mostly downhill) , the font end (carbon fork) on my 2005 Giant OCR carbon frame starts a loud screeching sound along with vibration. The bike has 9,000 miles.

• I tested the bike with two sets of wheels, one of which recently had the bearings replaced—same result
• The front wheel is not making contact with the brake pads
• I tightened the headset—no play

Any ideas?--thanks

tonski 

How tightly are you clamping the wheels?

operator

https://en.wikipedia.org/wiki/Speed_wobble

If that's a carbon steerer, i'd pull the fork and inspect.

tonski 

Probably a good idea anyway.

I'd suspect screeching if he's pinching bearings in the wheel, I can't think of another place it would come from if the sound is definitely forward the BB. Pinching bearings in the wheel would slow the front and cause the rear to accelerate faster causing that type of wobble. The usual fix for that is speeding up or taking weight off of the front wheel which wouldn't be possible if the wheel won't spin well at speed, nor is doing any kind of weight reduction on the front during a wobble advisable on a descent. Headset tightness, wheel problems, or fork problems would definitely be first suspects - in this case it sounds like a fork problem if the other 2 are good though I'm not sure how it would screech.

DMF 

Please confirm that it is screeching when you're not applying the brakes. (And have you checked that the brake isn't dragging?) These are rim brakes, right?

FinanceGuy

Sound emanates at speed—no brakes applied; Tektro road caliper brake set

DMF 

If nothing is touching the wheel it must be the hub.

Or you're mis-locating the sound, which riders frequently do. Have someone ride alongside you and listen.

Otherwise, I'm stumped.

operator

On both wheelsets though?

DMF 

That's why I'm stumped. :/

operator

It's possible both wheelsets are ****ed though, although not that likely...

DMF 

If the hubs are adjusted too tight and the QR too loose, maybe the QR is spinning? Okay, that's a real stretch.



Maybe it's the rider screaming?

m4ximusprim3

They said everything intelligent, so I'll ask the dumb question: there's nothing on the fork (speed sensor, stupid alleycat sticker card, etc) that could be whistling/vibrating at speed, is there?

ExMachina

did you figure this out?

i've got a very similar problem.

i thought it was the front wheel but it now seems to be the rear wheel.

the test i did: while coasting down hill and the screeching starts, begin to pedal. when i did this the noise immediatly stopped, so i think my freewheel is farked

idutri

Any one figure this out yet? My bike is being shipped to Trek (carbon 5200 frame) for exactly the same problem.
Very similar scenario, coasting downhill, speed over 25mph, would hit a slight road crack and frame starts screeching, a turn or two of the pedals would stop it 85% of the time otherwise have to come to almost stop.
Been occurring for 2+ years but getting much more frequent. Started with replacing bottom bracket and eventually disassembled and reassembled bike, still issue. Was riding in GA last weekend and problem was occurring at much lower speeds on 'shake and bake' roads. Was able to ride with screeching and listen and problem seems to be coming from above bottom bracket. I do have some clearcoat issues, exposed carbon
at joint in that area.

Booger1

Freewheel /freehub bearings are dry.