vibrating front brakes on 88 Turbo Coupe

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vibrating front brakes on 88 Turbo Coupe

December 31, 2017, 05:14:31 PM

Hello all, and Happy New Year!
Our turbo coupe has developed a little by little, worsening vibration when braking in the past several months. I finally pulled the front wheels and found that the calipers had some play in them.
I tightened the bolts that hold the calipers on and removed most of the movement, in a test drive it was better, but still had some vibration.
I wonder if the chattering has caused some problem in the calipers so that they will have to be replaced in order to fix the shakes when braking.
Any knowledgable suggestions on this will be greatly appreciated.
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #1 – December 31, 2017, 08:24:22 PM

It's called runout, more commonly warped rotors. Have a mechanic take your rotors off, put them on a brake lathe and resurface them and eliminate the lateral runout (maybe repack and preload your wheel bearings while they're apart). Since it's a TC, it could be either in the front or back (4 wheel disc), but my money is on the front.

vibrating front brakes on 88 Turbo Coupe

Reply #2 – January 01, 2018, 01:52:57 PM

Quote from: TheFoeYouKnow;464119

It's called runout, more commonly warped rotors. Have a mechanic take your rotors off, put them on a brake lathe and resurface them and eliminate the lateral runout (maybe repack and preload your wheel bearings while they're apart). Since it's a TC, it could be either in the front or back (4 wheel disc), but my money is on the front.

Thank you for the response. I am pretty sure that it is the fronts since I feel it strongly in the steering wheel.
I will pull the parts and see if the rotors can be resurfaced to specs.
Another thought that I have had is going with larger rotor and calipers. Have any of you on here gone with larger slotted rotors & larger calipers? If so, what mods had to be done to get them to fit?
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #3 – January 03, 2018, 05:10:31 PM

So lets look at this another way. The calipers were loose and most likely walking around under non-braking and braking events. Any chance the pads are now unevenly worn? This would not cause any pulsation once tightened back down and on flat rotors but not optimum. Another thing you need to check is that the rotors are torqued properly to the spindle such that they are not wobbling on the spindle. If the calipers were loose who knows what else is loose on that front end.

As for a four disc car and saying if the steering wheel develops a shimmy under braking and it is the front brakes...negative ghost rider, pattern is full. I have personally had a couple vehicles with a warped rear disc cause vibration into the steering wheel.

I would check the things that do not cost money first:
1) Check for run out on the front rotors i.e. not torqued properly or bad bearings
2) Check for run out on the rear axles i.e. bad wheel bearings or bent axle
3) Check for worn brake pads

Next I would see if the rotors are warped which is typically easier to just pull them off the car and take them to a parts store that can turn them. Here turning a rotor is about $10 so with your brake setup you at looking at $40 to turn them or you can opt for new ones. The fronts are pretty expensive in that they house the bearings but the rear ones are typically cheaper as they slide onto the axle . If you replace the pads, or turn the rotors, or replace the pads and either turn the rotors or buy new ones you will need to bed the brakes.

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=85

http://www.stoptech.com/technical-support/technical-white-papers/bed-in-theory-definitions-and-procedures/stock-brake-system-bed-in

http://brakeperformance.com/bedding-in-rotors.php

Typically what most track guys do is bed new rotors in with old pads then install the new pads and bed them in. Typically you get better life out of the new pads if you do it this way.

vibrating front brakes on 88 Turbo Coupe

Reply #4 – January 03, 2018, 08:53:18 PM

Aerocoupe, that is what I call a very complete troubleshooting answer.
Thank you!
I wondered about the ghost effect on four wheel disc brakes.
My wife and I have had the flu, or at least some kind of virus since Christmas Eve, so I haven't been to the garage to pull rotors, pads, etc. yet. Next week I am having cataract surgery, so hope to get the parts to a machine shop before that.
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #5 – January 04, 2018, 05:07:18 PM

Another thing to do while you are at it is a complete brake fluid flush if you have not done one in a while or ever. The fluid does not circulate so over time it will cook and become less affective in that it will not hold up as well to high temps and boil at a lower point than when new. Motive has a really good power bleeder which allows one person to bleed the brakes and almost guarantees you will not run the MC out of fluid.

Read this first:
https://www.motiveproducts.com/pages/application-guide

Then go here and find the correct bleeder kit:
https://www.motiveproducts.com/collections/domestic-bleeder-kits

Or do it the old fashioned way and get a brake pedal pumper and work as a team. Just remember that if you have ABS this is an at your own risk kind of thing. The Motive bleeder works great with the SN95 Mustang ABS and works really well on my 2014 F150.

vibrating front brakes on 88 Turbo Coupe

Reply #6 – January 05, 2018, 12:45:20 AM

as a undercar tech whos been doing brakes almost daily for the last decade or so, i will almost guarantee that if the rotors are warped, that the pads will have some uneven wear. It may not be visiable to the naked eye, but I've seen one too many times were a rotor was turned, the pads looked "like new", and the problem developed again.

From your description, it sounds like the loose caliper was the culprit, but pay careful attention to the pins and slides. Ive seen plenty of pins that dont move quite smoothly enough, or slides that look fine, but have a small amount of rust jacketing built up under it, and the entire system doesnt move properly, wasting all the time and money you just invested in fixing the problem, only to have it re-appear.

If there is anything I have learned in doing brakes, it's that the smallest things make the biggest difference.

vibrating front brakes on 88 Turbo Coupe

Reply #7 – January 05, 2018, 08:04:41 PM

Thanks for the advice bootleggers deluxe.
When I take the brake system apart I will be examining every piece and part. I do not want this problem to return once dealt with.
What part of Iowa are you from? I am originally from Altoona, near Des Moines.
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #8 – January 06, 2018, 12:40:35 AM

Quote from: BLKBRD88;464174

Thanks for the advice bootleggers deluxe.
When I take the brake system apart I will be examining every piece and part. I do not want this problem to return once dealt with.
What part of Iowa are you from? I am originally from Altoona, near Des Moines.
Ron

little town called Delhi, over in northeast iowa. if you go along highway 20 between Waterloo and Dubuque, I'm halfway in between there.

I know of Altoona. It's iowa, and since there isnt a lot to do, we travel to other parts of iowa to see if there's something different, lol

And call me Boot. everyone else does!

vibrating front brakes on 88 Turbo Coupe

Reply #9 – June 05, 2018, 03:43:52 PM

OK, I am finally back home from months away, and ready to tackle the brake problem on our 88TC.

Before I have the rotors turned, I am curious, is there an upgrade that some of you have tried that makes the braking system on these four wheel disc brake systems even better?
Are there any parts such as larger rotors, slotted rotors, better calipers, etc that you feel is worth the extra costs for a daily driver?
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #10 – June 05, 2018, 05:40:42 PM

Get quality brake pads and bed them in after installation. If the calipers are original I would replace them with some remanufactured ones. The front brake lines are rubber and if they are original I would put new ones on as the ID can close up because of swelling. You can go back rubber or opt for Braided SS. If you find that the front brake lines are suspect then the rear lines (one on each caliper and one where the hard line from the body goes to the rear end) should also be replaced. That is a good start but the real upgrade would be to ditch the Teeves (if the car still has it) and go to a 93 Cobra booster and master cylinder. All of this is just my opinion so approach it how best fits your needs.

vibrating front brakes on 88 Turbo Coupe

Reply #11 – June 05, 2018, 07:17:27 PM

Quote from: Aerocoupe;466014

Get quality brake pads and bed them in after installation. If the calipers are original I would replace them with some remanufactured ones. The front brake lines are rubber and if they are original I would put new ones on as the ID can close up because of swelling. You can go back rubber or opt for Braided SS. If you find that the front brake lines are suspect then the rear lines (one on each caliper and one where the hard line from the body goes to the rear end) should also be replaced. That is a good start but the real upgrade would be to ditch the Teeves (if the car still has it) and go to a 93 Cobra booster and master cylinder. All of this is just my opinion so approach it how best fits your needs.

Thank you again Aerocoupe....will check these things out.
Ron

vibrating front brakes on 88 Turbo Coupe

Reply #12 – June 13, 2018, 11:47:57 AM

another thing to look at closer is the line to the caliper.
where the rubber meets the crimp.

if you were a tiny spec you would see the rubber on the inside of the line becoming worn and the interior perimeter of the hose is sorta "cut".

over time this rubber hanging down in the fluid is in the way of the fluid returning back to the master.

the interior rubber line becomes a check valve so to speak.
the user pushed on the pedal and fluid travels out to the caliper.
you let off the pedal but the fluid is not fully returning back keeping the caliper partially engaged.

the heat will warp the rotor,,
you replace the rotor/bearings and notice if "feels" better but in short time the rotor is warped again. then you start thinking things like "cheap china steel" ect,,

then you change the hose to the caliper and suddenly your rotor lasts longer!

i personally have noticed this problem is more apparent on the front passanger side,, not sure why.

what i do know is the front driver is the only caliper that does **NOT** pass through the prop valve !!