Last night I changed the 26 inch fox 32 for a x fusion sweep now there is a vibration in the front brake. The bike is a BFe 275 and I am still running the 26inch wheels.

The change went fine, no problems putting the 15 mm adapters in the Pro2 Evo hub, head set went together fine and I have checked everything is tight.

These forks have been in this frame before at 140mm but different wheels and brakes. LBS did a lower fork service and lowered to 100mm, I have checked there is no play in the forks.

Could this be that the rotors have bedded in for the 26 forks and there is slightly different angle with the 650b forks?

Or the different angle change in the older brake line is causing internal pressure issues?

Could I have your thoughts please before I refit the old forks and start changing brakes around, thanks

A spot of oil or grease on the rotor?

Remove, clean everything and refit. Check for a ridge on the pads just in case they were not fully contacting the rotor previously.

Is everything straight on the fork? Brake lined up properly? Rotor straight?

agree with cleaning the rotor and pads, plus check for a groove. Only time I have had something similar was a slightly bent rotor.

@crashrash- rotors and pads cleaned etc, still does it. Incidentally, this bike gets used on road a lot so i get the squealling brakes, I have sets of pads and rotors dishwashered, baked and sanded ready to rotate when the noise starts!

@mikewsmith- disassembled, all clean, no movement. Tried the pads and 2 other sets, no ridges, rotor is straight, tried another as well. The fork moves without any uneven patches, tried higher and lower pressure but no change to vibrations.

Put the old forks back on and it is now doing it with them too but not as bad. Brake line has an external mark where it was fixed to the 26 fork, [fixes higher up with the new fork] but I can’t see a kink externally. Is it time for a new brake line?

… if there is no “Play”… – possible that your combination of parts: frame, fork, brake disc, wheels and so on has a “resonance frequency” which the brakes “excite”.

And in this case you might have a real problem.

Easiest then to start changing parts which are not expensive. Easiest to start with the brake disc. As new brake disc pick a different disc from what you have right now. Maybe one which is rotational much more stiff (has more material).

Had such an issue with a RockShox Reba fork. Terrible. A new (really cheap) brake disc solved it.

@andreas- frame and fork work as have been paired before, I have some Aztec rotors so will try a 180 and 160 tomorrow. Just been on my beer run and the issue is pressure related. On the flat needs about 2/3 lever pull, down a steep hill about 1/3. When cold it does it at all speeds when hot on when pulling harder.

haha. Great research! Bikers which never had these issues think we are nuts…

Yes – good approach.

With the “wrong” rotors I even had some influence from the tyre pressure…

The rotors (and resin pads) fixed it on my (old) bike.

Later on: same frame but much stiffer fork (34) never had this vibrating thing again – no matter which rotors, wheels, tyres….

Beer run & bike research: great combination!

Good luck!

So I have solved the problem and it was entirely of my own creation!

I was about to try some different rotors and while bending to pick my spares box, I came eye to eye with the font calliper of my gen 5 bfe’s sweep roughcuts, eureka! No adapter, my fox 32 takes a 160mm rotor as standard and the sweep 180mm. Without thinking I had just transferred everything across. I did not notice on the bike as the calliper now sits slightly inboard of the rotor and with the adapter slightly outboard.

A bike shop or expert would have picked it up right away and I will now know to suggest this.

Thanks to all who commented, it gave me a few ideas to try.

Disc brake friction is a dark science connected with transfer of molecules from the pad to the very hot disc. With brakes used in a wet gritty abrasive environment this doesn’t get a chance to happen, which is why mountain bikers don’t suffer some of the squealing and vibration problems that roadies sometimes suffer.

D’oh, didn’t read the second to last comment before mine.

Glad to hear it’s sorted!

@globalty – that explains why gen 5 never has a problem,  it only goes on the road for a drying off ride after a wash, whereas bfe 275 rides on the road weekly and goes on the back of the car on holidays and I get endless problems with squealing. As I said above I have a supply or washed and cooked pads and rotors left over from being sold new ones to cure the problem. I find if I regularly dishwasher the pads and degreese and sand the rotors with 120 grit I get about 4 weeks from the rear and about 4 months for the front. The baking I find is easier to do with a Bunsen burner but is only needed if the pad is really contaminated.

@philjunior- I missed your unedited comment but thanks anyway