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The mkiv Supra Owners Club

Are my new UK Brakes warped?


SupraGirlie
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On Sunday a member on here sold me some UK front brakes, (calipers, discs and pads) and also fitted them for me. When I first drove the car and used the brakes it is like the peddle is pumping its self up and down when I use them at any speed, although they pump faster the faster the car is going, they also vibrate alot when I brake from a high speed i.e 60mph+ He said this should go after a good drive, so after the 80 mile drive home, it is still happening, although not as bad, it's still very much happening :( He also said the discs were new can new discs be warped?

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Guest Supra2

who fitted them for you?

 

and no new disks cant get warped that quickly. especially genuine toyota disks.

 

"new" disks and pads fitted Properly and brake fluid flushed 2-3 times would not cause you any problems at all, especially within 80 miles of normal driving.

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Try this for help;

 

http://www.mkivsupra.net/vbb/showthread.php?t=188807&highlight=brakes+FAQ

 

New discs and pads, correctly fitted and bled out should work problem free albeit some will need bedding in for a few hundread miles as the surfaces key toegther. However they should be vibration free and the pedal should feel adeqaute at the least and not conerning. Could be new discs mounted on dirty hubs or hubs that were not fully cleaned. Possible issue with a caliper piston seal etc.

 

Have you taken it easy for the first few hundred miles on the new brakes or have you used them as normal?

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When fitting new discs it's important to make sure that the run-out is within tolerance. I can't remember what that tolerance is off the top of my head but I do know it is very much next to nothing, maybe something like 0.07mm??. The only way to measure the run-out is with a dial test indicator gauge.

This run-out needs to be measured on the hub, and on the disc. If the run-out on the hub is too great then you need to replace the wheel bearing or the hub itself. If the run-out on the hub is good but the disc is out, it may be possible to index the disc round until the run-out falls within tolerance. If not, then it's likely that the disc is warped so you would need to replace that.

As DSK said as well, all the mating surfaces need to be cleaned and rust free to have any chance of getting the run-out's within tolerance.

 

Hope that helps you in some way....

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I'd hazard a guess at crud on the hubs between the hub and disc aswell. Discs would need to have been abused very badly to get warped, incorrect bedding procedure would leave high spots but if they're new then thats not the case. Take the discs of and clean the hub and the part of the disc that sits on the hub, then refit them.

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Have the disc run-out checked with a DTI (dial test indicator) as per the info (below) in DSK's link - although the maximum run-out should read 0.05mm

 

Recommended Maximum Disc Run-Out

Good Practice;

Always remember to check disc run-out before fitting new brake pads. (Maximum disc run-out on vehicle 01.5mm)

Problems;

Excessive run-out will cause noise, judder, uneven pad wear and poor brake efficiency.

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Fairly common problem. Providing you are not getting any steering wheel vibration and its just the pedal that is jumping up and down then they have overheated. Where the internal vanes are attached to the rotor, conduction is very good, but where there is only air behind the rotor the conduction is very poor. This uneven heating causes the disc to distort and go thick-thin. You may be able to see blue heat areas radiating from the centre of the disc inline with the vanes. Did you bed them in?

 

You can get the discs machined true again. I've used pro-cut equipment in the past and been charged 20 quid per disc. They machine the disc to your hub whilst on the car.

Edited by 4packet (see edit history)
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Have the disc run-out checked with a DTI (dial test indicator) as per the info (below) in DSK's link - although the maximum run-out should read 0.05mm

 

I had it in my head it was 0,125mm or 0.005". Didn't think the runout on the disc had to be 0.001".

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Thanks for the comments, they have been very helpful. I will be dropping the car in to AFR tomorrow to have them taken off and cleaned etc. Really gutted to be honest as I have now got to pay AFR to sort them out and possibly buy new discs if they are warped and pay to get them fitted again! I will be getting some money back from the member I got them from who fitted them hopefully....

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I had it in my head it was 0,125mm or 0.005". Didn't think the runout on the disc had to be 0.001".

 

No, it's 0.05mm or 0.002". :)

 

From Toyota Service Manual

 

3. MEASURE DISC RUNOUT

Using a dial indicator, measure the disc runout at a position

10 mm (0.39 in.) from the outside edge.

Maximum disc runout:

0.05 mm (0.0020 in.)

If the disc’s runout is at the maximum value or greater, check

the bearing play in the axial direction and check the axle hub

runout (See page SA–16). If the bearing play and axle hub

runout are not abnormal, adjust the disc runout.

4. IF NECESSARY, ADJUST DISC RUNOUT

(a) Remove the 2 bolts and torque plate.

(b) Remove the hub nuts and the disc. Reinstall the disc 1/5 of

a turn round from its original position on the hub. Install and

torque the hub nuts.

Torque: 103 NVm (1,050 kgfVcm, 76 ftVlbf)

Remeasure the disc runout. Make a note of the runout and

disc’s position on the hub.

© Repeat (b) until the disc has been installed on the 3 remaining

hub positions.

(d) If the minimum runout recorded in (b) and © is less than 0.05

mm (0.0020 in.), install the disc in that position.

(e) If the minimum runout recorded in (b) and © is greater than

0.05 mm (0.0020 in.), replace the disc and repeat step 3.

(f) Install the torque plate and torque the 2 bolts.

Torque: 118 NVm (1,200 kgfVcm, 87 ftVlbf)

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