Shake Under Braking Diagnosis mystery

[Bellow]

It doesnt pull anymore since alignment was done, just a vibration under light to mid braking over 50mph.

This sounds more feasible, how would I check and remedy? Remove the wheel obviously and then what?

Then remove caliper followed by disc. Caliper removal can be awkward as can re torqueing its retaining bolts when done.

My guess is it’s either wheel or tyre damage then.

Does the A45 run the same wheel width front and rear, or is it a staggered setup? If the former, try swapping the “repaired” front with one of the rears and see if the shudder under braking changes.

If the above is feasible, consider that first. Disc removal is tricky, the above simple. Could be a vibration due to a slight distortion in the wheel that took the kerb.

 

[whitenemesis]

Clean the hub/disc interface very thoroughly.
I would also try some really hard stops from 70mph, just to clean any pad materials from the disc faces

 

[colwill1]

So car is in with Colin Ferns and they advised alloy has a buckle and that would be his first thing to fix...

Car due back next week.

Fingers crossed that solves it. Can't believe that graze with the curb buckled it. Unless it is a coincidence and I hit a pot hole around the same time.

 

[colwill1]

Buckled alloys fixed and it unfortunately still does shake under braking at speeds over 45/50mph.

Going back to colin ferns on Monday.

 

[zipdip]

Well could be a warped disc ,does the shake seem to come from one side,I would rule out a wheel bearing as that would have been checked when the buckled wheel was found,just maybe you have a brake caliper that is only working one side,thats my best guess.

 

[zipdip]

Thinking on it you say it comes when you are braking from 40/50 mph,now if you drive like me ,you are aware that you will have to brake and so you touch the brake pedal in a light and progressive way to stop the car,I take it if you drive down the road and jam the brakes on you do not get this shake,it seems like it could be a caliper.

 

[colwill1]

Thinking on it you say it comes when you are braking from 40/50 mph,now if you drive like me ,you are aware that you will have to brake and so you touch the brake pedal in a light and progressive way to stop the car,I take it if you drive down the road and jam the brakes on you do not get this shake,it seems like it could be a caliper.

Yes under light to mid braking you feel it, under heavy braking far less noticable. So whether a disc is slightly warped or a caliper I'm not sure.

Just seems unlikely as it occurred after kerbing it and the discs and pads only being 2000 miles old and merc parts

 

[whitenemesis]

Warped discs are extremely uncommon. Much more likely to be dirty disc/hub interface or pad material deposited on the disc faces.
Try a few very hard stops from 70mph to clear the disc faces. It may be you have to do this routinely if most of you driving is town or low speed.
I needed to do this in my CLS55 after pootling around town, no great hardship

 

[brigadier]

As above - uneven deposits of brake pad material is the most common cause of brake judder. Just need to remember not to stop completely after few hard stops from 70mph to 20mph, as this will deposit brake pad material in one spot - but drive for a bit without stopping to let the brakes cool.
Best done at motorway with no traffic lights late at night when no cars around.

 

[colwill1]

Cars with Colin Ferns garage for the week, he is taking it home tomorrow and will let me know his thoughts, ironically he used to rent space off my dad back in the day so I'm happy to just leave it with him and trust them... hopefully he cures it on his drive home with some hard braking braking because I'm with you cant see it being discs.

If it is a disc issue, I'll take it up with the garage I bought the car from, who I did speak too briefly and were helpful too and just asked to keep them updated and not to carry out work without prior consent.

 

[Deleted member 149005]

If you curved it could have bent the disc?

 

[Deleted member 149005]

If you curved it could have bent the disc?

Meant to say curbed it.,.

 

[Bellow]

If you curved it could have bent the disc?

Extremely unlikely.

 

[Deleted member 149005]

Unlikely but possible- I managed it..,

 

[colwill1]

Hi all,

Sooooooooo....

Got the car back yesterday and everything is fine and Colin did not need to do anything. I think he was being nice in saying that he cleared some brake deposit and rust in town before he got to the motorways.

However I also think it was also a combo of paranoia and the 19" alloys with low profile tyres.

Although my last car had 18" alloys, the tyres were nowhere near as firm as these are so when you brake you do feel every little bump under braking. Combine this with the paranoia of curbing the alloy, plus some deposits on the discs and you have a cocktail that equals me thinking there was a problem.

Anyway, drove the car home last night and everything is fine.

Thanks all