Bad brake discs - is it possible?

[Chrisgti6]

Morning all,

Not on a Clio, but the car's not really relevent.

I upgraded the front calipers, discs and pads on my car a few weeks ago. The calipers are from a Focus ST and are used but in perfect condition, and I bought a brand new set of 320mm discs and accompanying pads from Eurocarparts. The discs and pads are Pagid, which i'm aware of a decent brand and are OE on many cars.

Now i'm a few weeks in and i've developed a pretty serious vibration when the brakes are applied, but it only happens after 5-10 minutes of driving. From cold they are fine.

They were bedded in correctly as per the instructions that come with the discs, i've also subsequently tried the 'fast' bedding in approach but still the issue is there. I've stripped and cleaned EVERYTHING, the hub face is perfect and 'as new', the pistons and sliders are completely free and they aren't binding. Everything is torqued to manufacturers spec but it's still there. There's no visible defects in the discs, no pad deposits etc.

Is it possible that i've just got a bad batch of discs that are deforming slightly once warm? is that even possible?

I've ordered some Brembo HC discs that are coming tomorrow, but if possible I want to take the Pagid ones back to ECP for a refund but need to be convinced that i'm right before doing so.

Thoughts?

 

[Martin.]

Try checking each side after a run and see if there is a noticeable difference in heat. Also if all the pad material is evenly worn?

Could be a seized or sticking piston on one side. I've had this before and it warped my discs.

Can you feel the vibration at all times? Or is it just on heavy breaking, or once some heat gets into the brakes?

When I had this problem I couldn't really notice it until I was really using the brake pedal.

 

[loggyboy]

**didn't read post properly - please delete**

 

[Chrisgti6]

Try checking each side after a run and see if there is a noticeable difference in heat. Also if all the pad material is evenly worn?

Could be a seized or sticking piston on one side. I've had this before and it warped my discs.

Can you feel the vibration at all times? Or is it just on heavy breaking, or once some heat gets into the brakes?

When I had this problem I couldn't really notice it until I was really using the brake pedal.

I've checked the temps, both are evenly warm. The calipers were checked before being bolted on, the pistons are free moving throughout the full range. Pads appear to be evenly worn (baring in mind they've only covers about 1,000 miles it's difficult to tell) and if I jack the car up they rotate freely. The vibration is only once I get some heat into the discs, but once warm can be felt whenever the brakes are used regardless of speed. The steering wheel can be seen to move, especially if I let go of it!

I'm pretty clued up on this sort of thing, having maintained my own cars for 15 years, but this has really stumped me!

 

[Gaverick]

Got any gear to measure the lateral run out?

 

[George@RTR_Parts]

Yep, get a dial indicator on them mate

Could have got you the Brembo HC discs off the Focus ST aswel for future reference

 

[Chrisgti6]

Got any gear to measure the lateral run out?

Afraid not. Well I've swapped them out for a new pair of brembo discs and instantly it feels better, I'll just have to wait and see if it returns. If so I've got a deeper issue but I've no clue what!

 

[Chrisgti6]

Yep, get a dial indicator on them mate

Could have got you the Brembo HC discs off the Focus ST aswel for future reference

i know mate, it's the same disc/pad/caliper setup. The calipers came off a broken ST!

got them for £95 delivered so not too bad price wise