Juddering under light braking
Discussion
I had new MTEC brake discs (drilled and grooved) and new Brembo pads fitted to two cars, professionally installed by a garage using a DTI gauge. After around 1,000 miles car A has a severe judder from the front of the car under light braking at low and high speeds. Car B is absolutely fine, also doing similar mileage with no signs of fault.
Both cars have had shocks, springs and bushes replaced in the past year and there are no knocking noises. This issue was not present with previous sets of discs / pads. MTEC were dismissive and suspect an underlying issue as the fault took 1,000 miles to appear. There's nothing obviously upset with the problem car, no other strange noises, and the problem only occurs under breaking. I do not sit on the brakes at lights cooking the discs and I did not abuse the discs from new. I've tried harder braking to try and "correct" the wobble but it makes no difference. The brakes are effective but the judder is getting worse.
Faulty car A is a BMW E92 330i and car B is a BMW E30 325i. My plan is to get back to the garage and use the MOT brake tester. Is there anything else that I should be looking for?
Both cars have had shocks, springs and bushes replaced in the past year and there are no knocking noises. This issue was not present with previous sets of discs / pads. MTEC were dismissive and suspect an underlying issue as the fault took 1,000 miles to appear. There's nothing obviously upset with the problem car, no other strange noises, and the problem only occurs under breaking. I do not sit on the brakes at lights cooking the discs and I did not abuse the discs from new. I've tried harder braking to try and "correct" the wobble but it makes no difference. The brakes are effective but the judder is getting worse.
Faulty car A is a BMW E92 330i and car B is a BMW E30 325i. My plan is to get back to the garage and use the MOT brake tester. Is there anything else that I should be looking for?
More likely that you've been braking a tad hard in the 1000 miles, and got the discs hot, and some pad material has transfered to the disc while you sat with your foot on the brake causing teh judder.
Find a quiet road @ 60mph, and brake firmly to ~5mph. Repeat 2-3 more times, and see how it is. Allow the discs to cool down while driving around.
Find a quiet road @ 60mph, and brake firmly to ~5mph. Repeat 2-3 more times, and see how it is. Allow the discs to cool down while driving around.
If you've got them hot and stood stationary on the brakes (or your hubs had some crud on or weren't flat when fitted) then generated some runout and you have a sticky pin slider or ageing caliper seals then you can generate DTV which causes judder, in which case M-tech are right and it's an underlying fault. Aggressive pads can make this materialise very quickly where you might not even have suffered a problem at all before.
As said you can also get uneven pad deposition or corrosion deposits in which case it should clear up with a re-bedding cycle/decent thrashing.
If none of the above then there are plenty of manufacturing defects that can cause excessive runout and then judder (such as poor material quality or an undersized centre bore) but they should be easy to check for with the right equipment.
I'd probably get the calipers rebuilt, pin sliders replaced and either get the discs skimmed on the car or bin them and get another set, perhaps another brand if you're not happy. Personally I'd also stick with OEM discs unless you're changing to a 2 piece or floating upgrade kit from a top brand, quality is much more important than grooves/drill holes and indeed they can introduce their own issues.
You're onto a loser trying to argue it IMHO and if they've not turned around and been helpful it probably means that it's either rare they have issues and they genuinely think it's your fault or they have loads of problems and they're just being difficult.
As said you can also get uneven pad deposition or corrosion deposits in which case it should clear up with a re-bedding cycle/decent thrashing.
If none of the above then there are plenty of manufacturing defects that can cause excessive runout and then judder (such as poor material quality or an undersized centre bore) but they should be easy to check for with the right equipment.
I'd probably get the calipers rebuilt, pin sliders replaced and either get the discs skimmed on the car or bin them and get another set, perhaps another brand if you're not happy. Personally I'd also stick with OEM discs unless you're changing to a 2 piece or floating upgrade kit from a top brand, quality is much more important than grooves/drill holes and indeed they can introduce their own issues.
You're onto a loser trying to argue it IMHO and if they've not turned around and been helpful it probably means that it's either rare they have issues and they genuinely think it's your fault or they have loads of problems and they're just being difficult.
S. Gonzales Esq. said:
I'd add that OEM style pads don't really need bedding at all and will perform perfectly well for any single stop right from the off, although if they are given some stick in the first few hundred miles they may go through a slight fade phase and smoke or stink as the resins boil off,.With performance oriented pads it's also worth thinking being sympathetic while using that process, it's about right for a typical performance car but overheating a new set of brakes will introduce more problems than a good bedding will solve. If you start getting fade then go straight into the cool off phase, don't keep hammering it.
S. Gonzales Esq. said:
This has made everything better. I'd tried a few 60-0 mph stops but not to the point of brake fade, and the complete stop defeated the aim of the bed in cycle.It took 9 goes to get to the point of brake fade, the 10th cycle was for good measure. I let the discs cool and have had no judder this morning and the brakes are much more effective.
Thanks for the pointer and for the correct bed in technique!
The Wookie said:
If you've got them hot and stood stationary on the brakes (or your hubs had some crud on or weren't flat when fitted) then generated some runout and you have a sticky pin slider or ageing caliper seals then you can generate DTV which causes judder, in which case M-tech are right and it's an underlying fault. Aggressive pads can make this materialise very quickly where you might not even have suffered a problem at all before.
As said you can also get uneven pad deposition or corrosion deposits in which case it should clear up with a re-bedding cycle/decent thrashing.
If none of the above then there are plenty of manufacturing defects that can cause excessive runout and then judder (such as poor material quality or an undersized centre bore) but they should be easy to check for with the right equipment.
I'd probably get the calipers rebuilt, pin sliders replaced and either get the discs skimmed on the car or bin them and get another set, perhaps another brand if you're not happy. Personally I'd also stick with OEM discs unless you're changing to a 2 piece or floating upgrade kit from a top brand, quality is much more important than grooves/drill holes and indeed they can introduce their own issues.
You're onto a loser trying to argue it IMHO and if they've not turned around and been helpful it probably means that it's either rare they have issues and they genuinely think it's your fault or they have loads of problems and they're just being difficult.
I think you've hit the nail on the head with the aggressive pads and possibly dirty hubs prior to fitting, combined with me being overly gentle in the initial bed in period. Out of interest how many miles would you recommend before bedding the new pads in properly? My re-bedding technique was incorrect and following the advice linked in this post has sorted it.As said you can also get uneven pad deposition or corrosion deposits in which case it should clear up with a re-bedding cycle/decent thrashing.
If none of the above then there are plenty of manufacturing defects that can cause excessive runout and then judder (such as poor material quality or an undersized centre bore) but they should be easy to check for with the right equipment.
I'd probably get the calipers rebuilt, pin sliders replaced and either get the discs skimmed on the car or bin them and get another set, perhaps another brand if you're not happy. Personally I'd also stick with OEM discs unless you're changing to a 2 piece or floating upgrade kit from a top brand, quality is much more important than grooves/drill holes and indeed they can introduce their own issues.
You're onto a loser trying to argue it IMHO and if they've not turned around and been helpful it probably means that it's either rare they have issues and they genuinely think it's your fault or they have loads of problems and they're just being difficult.
On the subject of drilled / grooved discs and performance pads, they were a "give it a go" purchase and I had no complaints about the OEM set up other than the discs / pads being due replacement. When this set is worn out I'll be switching back to OEM discs and pads, I agree with the sentiment here that there's no real benefit for road use.
SoupAnxiety said:
I think you've hit the nail on the head with the aggressive pads and possibly dirty hubs prior to fitting, combined with me being overly gentle in the initial bed in period. Out of interest how many miles would you recommend before bedding the new pads in properly? My re-bedding technique was incorrect and following the advice linked in this post has sorted it.
On the subject of drilled / grooved discs and performance pads, they were a "give it a go" purchase and I had no complaints about the OEM set up other than the discs / pads being due replacement. When this set is worn out I'll be switching back to OEM discs and pads, I agree with the sentiment here that there's no real benefit for road use.
If the judder has gone with a good bedding then it sounds like it was uneven pad deposits.On the subject of drilled / grooved discs and performance pads, they were a "give it a go" purchase and I had no complaints about the OEM set up other than the discs / pads being due replacement. When this set is worn out I'll be switching back to OEM discs and pads, I agree with the sentiment here that there's no real benefit for road use.
In terms of miles until bedding, I'd say brand new for a track biased pad and never for an OEM style pad unless it starts developing issues like you've had!
fatboy b said:
More likely that you've been braking a tad hard in the 1000 miles, and got the discs hot, and some pad material has transfered to the disc while you sat with your foot on the brake causing teh judder.
Yes, very likely. Should wear off in normal driving but can take a while. Gassing Station | General Gassing | Top of Page | What's New | My Stuff