Knock from suspension

Southdowns

Joined
Aug 25, 2024
Messages
11
Age
61
Location
Winchester, UK
So I’m posting this here as I think it’s suspension related, but I can’t be sure.

I’m getting quite a loud knock from the front of the bike when going over bumps at low speed - could also be there at higher speeds but there’s too much wind noise to hear it then.

The fork seals were replaced not long ago, but that’s about the only extra info I can give! Where should I start looking?
 
Southdowns said:
So I’m posting this here as I think it’s suspension related, but I can’t be sure.

I’m getting quite a loud knock from the front of the bike when going over bumps at low speed - could also be there at higher speeds but there’s too much wind noise to hear it then.

The fork seals were replaced not long ago, but that’s about the only extra info I can give! Where should I start looking?
Click to expand...
I believe you will find the knocking or rattling is from the secondary master cylinder pushrod linkage on the left fork and left brake caliper. Mine would begin to rattle a little toward the end of 12,000 mile brake fluid flush/bleed intervals. A good fluid service would remove it even close to 180,000 total miles. When the brake is applied the caliper pivots on the bracket and this brings the pushrod link into compression and the secondary master cylinder is pressurized. If there is a little play in the linkage when the brakes are not applied the pushrod rattles. You can check it by riding over a series of bumps that makes the noise. Then go back over the bumps with slight front brake pressure - just enough to take up play in the linkage.
 
Interesting, I have an occasional rattle up front and always thought it was a brake pad after the caliper retraced. I have all "new" to me hoses and a new SMC to install, as I have a hose that looks VERY suspect, but isn't leaking.
 
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