Strange front wheel symptoms

[JLGsDad]

Anyone any ideas:

• 2001 Honda Accord 65,000m. Recent new tyres, 1,000m since last service.
• Driving on M25, ran over noisy concrete section, steering started to wobble as if poor tyre balance. Steering stopped wobbling on smooth tarmac then wobbled again on next noisy section. No apparent change with speed. Later concrete sections no symptoms then Came back briefly on a smooth section. No undue noises, runs straight and true and braking fine
• checked wheels at Service station. No apparent damage or movement. Tyre pressures checked before journey. Car sits straight.
• Next 100 miles no problems. Did 2 short journeys then horrible brake pad smell. Front offside wheel very hot. Let it cool, took wheel off, banged calliper, wheel turns OK, no noticeable damage to suspension. Drove few more miles, no apparent heating.
• bought spanner’s, took calliper and pads off, both sliders move freely and I can just about push the piston back (1,000m since brake fluid change and slider pins regrease). No abnormal wear on pads or disc. Hub spins fine with no noise.

Wheel bearing? But there’s no noise when driving and no noise or vibration when spinning the wheel.
Brake calliper sticking? Maybe for the heat but what about the wheel vibration (coincidence).

I’m at a loss.

[GreenV8S]

Vibration on the concrete was probably due to the tyres interacting with the surface finish an nothing to be concerned about unless it comes back on tarmac.

The sticking brakes could be caused by a problem at the master cylinder preventing the m/c piston coming back fully, or the pads sticking in the calipers.

[finlo]

I've had this problem exactly, it was a seized piston in a two pot caliper the shuddering was the brake grabbing.
Very hard to pinpoint as it came and went dependent on speed I think.

[Coilspring]

As above, or.

Brake flexy hose is restricting flow backwards. Clamp the hose and go for a gentle drive but heavy on the brakes, and then repeat with the hose not clamped.

[JLGsDad]

Guys. thanks.
I'm back home now, so I'm on my PC which is far better than my phone.
Specifically;
1. The vibration was far from normal. I should have made clear that I've driven on those sections of concrete countless times and never had anything but the mild vibration normal from ridged concrete. I've also driven with unbalanced wheels and this was far worse than that. Also, the brake dust on all the leftover glue from lead wheel weights suggests that I didn't lose a lead weight from that wheel. The problem didn't reoccur on the return journey over similar concrete on the other carriageway.
2. I think that if the master cylinder was causing problems then the nearside rear wheel would at the very least show some heating too. I'll therefore leave overhauling that as an option until I've seen if the problem reoccurs after i overhaul the calipers.
3. The caliper pins moved in and out as easy as you like and the boots looked perfect.. The piston boot looked good and had no tears or holes that I could see. Overhauling the front calipers looks as straightforward and inexpensive (say £40 for a blueprint kit inc pistons, brake fluid for a complete flush/replacement and caliper grease) as the ones I've done before.
4. I fitted stainless brake hoses 20,000 miles ago. It's possible that the central restraining clip broke under the vibration and allowed the hose to kink, thus causing intermittent brake grabbing that was self-perpetuating, with my then missing the heat build up until the pads smelt and my investigations freeing it without my noticing (and I didn't think to check the hose).

The factory service manual that i now have access to confirms that the front wheel bearing is pressed into the knuckle and therefore changing it is a PITA and/or expensive job. So it's good news that no-one has so far said it could be that (and I would be very surprised if it were).

[E-bmw]

As it only happened at that point it must be triggered by the road.

As you have recent new tyres, what are they?

Are they across the full car/just front?

Are they RFT/not?

[anonymous-user]

Check your brake fluid level and check for any kinks on hoses.

[JLGsDad]

Thanks.

The stainless braided hoses are fine, as is the level in the master cylinder. Now I can use my piston rewind tool I find the piston is more than a bit sticky in the caliper. I've ordered an overhaul kit for both fronts that I'll fit later in the week and will change the fluid at the same time.

The tyres are reasonable quality (Goodyear Efficient Grip 215/50/16 non-RFT) with 7+mm left and I can find nothing suspicious. The pressures haven't changed.

I've never had this problem with previous sticking calipers but I can imagine one scenario that fits:
@ the piston was starting to stick and the frequency of vibration from the concrete was sufficient for it to oscillate the pads to grab the discs, which then gave positive feedback to the vibration until I got onto smooth road again. This repeated several times.
@At the end of the long journey the lack of cooling air led to the the piston sticking and it didn't withdraw from braking at the next short journey, thus causing the caliper to heat up and start smelling..
@ My removing the caliper and banging everything freed up the piston sufficiently for me to get home without further trouble.

[lufbramatt]

Had the exact same symptoms as you on my E39 5-series. Intermittent judder through steering, hot wheel etc. Cleaning up the piston and slider pins improved it slightly. Cured completley with new (well, remanufactured) brake caliper.

[sjj84]

Same problem on my z4, steering wheel judder which would suddenly realise and then come back again. Sent the calipers off for a refurb, problem solved.