We are at a loss here and have exhausted our options.
We have a customer with a brand new Cervelo P5 with SRAM Force AXS. As we do with every build, we took the bike out and test rode it thoroughly, bedded the brakes, and everything checked out.
Customer takes the bike out on their second ride and the brakes are screaming like crazy. I’m not talking a little squeal after running through a puddle. SCREAMING. He brings it back to us, we inspect the pads, check the calipers for signs of leaking, check the rotors, and everything looks normal. We clean the rotors and pads with alcohol. Lightly sanded the top layer of the brake pads and went through the full bedding process again. It never made a sound. We test rode it the very next day and went through a number of braking scenarios at different speeds. It didn’t make a peep and worked as expected.
Customer picked up the bike, rode it two days later and it was screaming bloody murder. He brings it back furious. At this point we are thinking something has to be wrong with they system. We replace the entire brake set. New rotors, new caliper, new pads, bed everything again. We test it every day for 4 straight days and never hear a sound. Customer picks up the bike and rides it twice and it starts the screaming again.
We asked how he was storing it. It is kept in an air conditioned garage with no chemicals to speak of near the bike.
At this point we are considering sending him home with another bike to see if it happens with a new disc brake bike (this is his first disc brake bike).
Has anyone found any other situations that could be causing this? We are stuck.
Customer is doing something. Washing the bike with some odd detergent or other product? Using a spray-on chain lube and getting overspray on the rotors?
The sending home with another bike plan sounds good to me.
I’m interested in how this gets resolved. I have two bikes with SRAM hydraulic brakes, and I’ve only had the squeal once (today as a matter of fact). Disc brakes squealing in cars is usually an issue with vibration which is why high end pads have coatings with some damping on the backing. I’m wondering if this tech will trickle down to bike brake pads too.
Thin dab of copper slip on the metal back of the pads helped a lot in the past. I don’t find the shimano road ones to need that in the dry, but in the wet they do tend to be a bit screamy.
Which does make me wonder if the customer was riding in the wet (through a ford?) compared to your test rides in the dry? Or if they were dragging the brakes on long descents and getting the pads much hotter than when you were test riding with short sharp decelereations. In cases like this it’s understanding the variables that have changed. Ears - is it customer really sensitive and is reporting loud screaming from brakes when mechanic is saying it’s a nice quiet just normal disk brake noise. Hands - is the customer applying brakes in a different way. Environment. Heat/humidity/rain.
How big is this guy? I’ve heard that big people ( 250lbs, 3-bills size) can torque a bike in such a way they throw the drivetrain out of balance; could fuck up the wheels & discs, too
As a joke, my brother (6’2"; 320, easy - basically an Offensive Lineman #BrotherlyShove) sat on my bike and I SWEAR I heard her shriek “HE’S killing me!!!”
Yes, no sound. Not sure if morning humidity has anything to do with it, but if that was the contributing factor, all of our customer would be dealing with this.
Yes, these are all questions we are asking. We have the bike now and he will be joining us tomorrow night for our Tuesday group ride and riding with one of our technicians.
Last spring I bought a new P series and rode it quite a bit this summer with no issues. Last week the front disc started rubbing a little and and when the wheel was spinning just a little there was a slight ringing. On the weekend during it screeched very loudly for most of a sprint tri. Nothing after the race and nothing when I took it into the bike shop.
Actually, that reminded me of another possible variable. If the customer is removing the wheels to carry the bike to/from shop/ride and not tensiosing the through axle the same (too loose).