ausmini
https://www.ausmini.com/forums/

Pulsing brake pedal
https://www.ausmini.com/forums/viewtopic.php?f=2&t=101826		 Page 1 of 1
Author:  sheddweller [ Mon May 01, 2023 8:17 am ]
Post subject:  Pulsing brake pedal
I have an interesting problem.

Recently purchased a ‘99 Rover Mini 40. It has a speed related pulsing brake pedal. Checked the rotors and there was quite a bit of run out on both (.30-.50mm) so I replaced the pads and rotors, no change and runout still there.

I swapped out the rotors and flange with a known good car and the run out was the same so not rotor or flange problem.

Bought new bearings and pulled the hubs. Noticed someone had been a bit rough with the hubs, looked like they air hammered the cups out damaging the hub shoulder where the cup sits resulting in slightly cocked bearings. The left hub cleaned up ok and with new bearings the disc runout was about .10mm. The right hub was about .40mm. Pulsing still there.

Bought a new right hub and bearings, fitted it and disc run out is .10mm. Pulsing is still there.

Before I continue to load the parts cannon has anyone experienced this before? Any ideas? Seems strange that such a small defection could cause the pedal to pulse when it has twin cylinder calipers, you’d think the fluid would just move between the sides rather than push back up to the master cylinder.

Could the misaligned bearings have bent the CV stubs? They seem quite sturdy although they are polished more on one side but can’t see or feel any edge.

Any help would be appreciated.
Author:  drmini in aust [ Mon May 01, 2023 10:12 am ]
Post subject:  Re: Pulsing brake pedal
I would fit a new drive flange. Not expensive. They do wear.
Also measure the rotor thickness with a micrometer. Even 0.001" variation can cause pulsing, I replaced one recently for this.
Cheaper than machining.
Author:  68+86auto [ Mon May 01, 2023 1:49 pm ]
Post subject:  Re: Pulsing brake pedal
What procedure was followed when tightening the hub nut. If the incorrect procedure is used the bearings and swivel hub will be damaged. A thick washer needs to be used with the cone removed to tighten them up before removing the washer and reinstalling the cone.

My new discs had more runout and I have no issues.
Author:  sheddweller [ Mon May 01, 2023 2:29 pm ]
Post subject:  Re: Pulsing brake pedal
drmini in aust wrote:
I would fit a new drive flange. Not expensive. They do wear.
Also measure the rotor thickness with a micrometer. Even 0.001" variation can cause pulsing, I replaced one recently for this.
Cheaper than machining.


Thanks drmini. We tried swapping over a rotor and flange from another car and same issue. I think the runout was caused by poor bearing removal and installation. Replacing the bearings and the one hub has improved it but not eliminated it. Flanges, CV's, left upright, and calipers are the only things I can think of left to replace. Unless its now a problem in the Master Cylinder?

I checked the original rotors and thickness was consistent. Pretty sure it's not a rotor issue.
Author:  sheddweller [ Mon May 01, 2023 4:18 pm ]
Post subject:  Re: Pulsing brake pedal
68+86auto wrote:
What procedure was followed when tightening the hub nut. If the incorrect procedure is used the bearings and swivel hub will be damaged. A thick washer needs to be used with the cone removed to tighten them up before removing the washer and reinstalling the cone.

My new discs had more runout and I have no issues.


Good point. Seeing the damage from when the bearings were replaced it's a good bet the correct procedure wasn't followed torquing the hub nut.

I would have thought a little runout would cause the brake to shimmy when stopping but not cause the pedal to bounce.
Author:  simon k [ Mon May 01, 2023 6:27 pm ]
Post subject:  Re: Pulsing brake pedal
Stupud question - you've swapped the wheels around, right?

Take the wheels off and run it in gear up on stands - see if you can see what's moving
Author:  IndigoBlueCooperS [ Mon May 01, 2023 10:30 pm ]
Post subject:  Re: Pulsing brake pedal
Have you checked the rear brakes? I have had a rear brake drum that did not run concentric with the axle. OK when driving but when brakes applied, pulsing and under heavy braking rear wheel lockup. This was on a single line system with discs on front and spaced drums on rear.
Author:  sheddweller [ Tue May 02, 2023 6:24 am ]
Post subject:  Re: Pulsing brake pedal
simon k wrote:
Stupud question - you've swapped the wheels around, right?

Take the wheels off and run it in gear up on stands - see if you can see what's moving


Yes, done that. The rotors had a noticible wobble. Wobble is still there but not as noticeable now.
Author:  sheddweller [ Tue May 02, 2023 6:29 am ]
Post subject:  Re: Pulsing brake pedal
IndigoBlueCooperS wrote:
Have you checked the rear brakes? I have had a rear brake drum that did not run concentric with the axle. OK when driving but when brakes applied, pulsing and under heavy braking rear wheel lockup. This was on a single line system with discs on front and spaced drums on rear.


I hadn’t considered a rear brake problem. The focus has been on the front because the original rotors were so badly misaligned. Good point, that needs to be checked.
Page 1 of 1 All times are UTC + 10 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/