Wheel Vibration Under Braking

[paulhb]

I have just fitted second hand 314's and from the off they have vibrated when I brake, I had 302's on before and they didn't however to add more confusion I had my wheels refurbished and they are very tight to get on and off.
My thoughts are the second hand discs are slightly warped as I know the hub nuts are tight and its just had an MOT so the suspension is tight, or the powder coating that makes the wheels tight is making the wheels run slightly out of true, however the vibration is only when I brake.

Anyone have any suggestions please

[ditchp]

deffo sounds like warped disk's to me, can you feel the brake pedal sort of bounce when braking..

[m8internet]

Second hand brakes, I would start there
Presumably the pads and discs are second hand
The 314mm discs are known for vibrations, I've had it twice now
Ideally perform lots of full service brake applications, rather than light ones
Once you have performed about 20 take a look at the discs
If there is a ring around the inner edge then there is nothing to worry about, this is just the surfaces coming together and eventually they will match, the ring will then disappear
I get this with roughly every fifth or sixth pad change on used discs, it typically happens on the second set of pads on the discs

Nextly have you had the brake bias checked and adjusted?
If the rear brakes are the same, then it will need to be adjusted towards the rear

[paulhb]

I was going to get new discs but if this vibration is common there doesn't seem much point I'll try the heavy braking and see, the brakes are solid but they are second hand pads and discs but I have done 300 miles on them so far

The rears are new 292's but everything there seems fine no rings just clean discs, forgot to add that the discs were rusted when I got them and they are now clean after about 150 miles of use.

[m8internet]

As the rears are 292, then you don't need to change the brake bias, the difference is negligible

As above, perform several heavy braking applications then inspect the discs and post again
It usually takes about 2000 miles / 4 weeks for the pads and discs surfaces to match up and wear down evenly

Surface rust on discs is common, mine even have this after leaving the car overnight!

Nextly, presumably you swapped the calipers from 302mm to 314mm
What condition were these replacement calipers and pistons?
I only ever fit new calipers, I wouldn't touch a used one, even if it was free, unless it was refurbished/tested/overhauled

[paulhb]

I fitted second hand ones but they were in very good condition had them apart and replaced the seals and they are solid and don't pull to one side passed the MOT 2 weeks ago and were fine apart for a comment about the rust.
I have just been out and about with the car and did as you suggested about 20 full hard brakes to a standstill from 40 and strangely the vibration isn't there under heavy braking only if the are gently applied for normal slowing down.
I looked for a ring around the inner part of the disc and there is a small band so maybe they just need to fully bed in.

[melvyn8181]

i had same problem, so i got my wheels balanced and then it was cured.

[paulhb]

Strange you should say that had mine rebalanced today and its mostly gone, also M8Internet I did the heavy braking which left a dark ring around the inside of the disc and it was continuous which pretty much rules out warped discs I hope

[m8internet]

I looked for a ring around the inner part of the disc and there is a small band so maybe they just need to fully bed in

This is quite normal for used discs and used pads
Eventually the ring will disappear as the surfaces wear and match up flat with each other
I was worried the first time, suspecting a binding caliper, but was advised to monitor it weekly and if it had not disappeared after four weeks to bring them back, there was no need as I had covered 1000 miles and although it started to get worse it very quickly disappeared