Brake upgrade trouble??

[Bruce]

Ok Guys, I'm stumped. I'm wondering if you can give me some ideas on what my problem might be?

I FINALLY finished my '96 front disc brake upgrade on my '89 and I have a problem with it. Under hard braking (and only hard braking) there is a shuddering going on in the left front. When I installed the new knuckles I replaced the bearings in them, I also put in new lower ball joints including the LCA's, I have new rotors (run-out is .0025") new PF pads, I rebuilt the calipers, bled the system, serviced the slider pins and have some anti sieze where the ends of the pads fit into the caliper brackets. I brought my friend over to look at it and drive it and he's stumped also. It only does it under hard braking. I was thinking of just driving it for a while and see if anything changes once the pads bed in better. I thought I'd bounce this off of you guys and see what you think? We both double checked everything and it's all tight! Wheels are torqued to 95 ft. lbs.

It's making my brain hurt thinking about this! headbang

Mucho Thanks,

 

[Hack]

Totally off topic, but very impressive list of cars you have there! thumb

 

[Bruce]

yellowSHO:
Totally off topic, but very impressive list of cars you have there! thumb

Thanks! thumb

They are all my babies!! They all get treated with kid gloves!!

<small>[ October 31, 2003, 11:12 PM: Message edited by: Bruce ]</small>

 

[rangerj]

Bruce,

Just some thoughts;

LCA strut bushing

inner and/or outer tie-rod end

Weak spring and/or strut

Sway bar bushings and/or end-links

Subframe bushings

In hard braking the weight is dumped onto the front suspension, thus the above thoughts come to mind in re your shudder! shrug rangerj

 

[shojuan]

It sounds like you've got everything covered with the brakes. That being said it sounds like your shuddering is the result of suspension "tramp" The only thing I can add to rangerj (who knows his stuff)'s list below is strut mounts and check the condition of those tires and their balance. After replacing my front brake pads and rotors a year ago (Hawk HPS + new rotors) I was left with some nasty vibration after the excitement of the new pads wore off. Felt like warped rotors even though that didn't make sense given the treatment (not EASY treatment, just not foolish treatment). Got even worse after I flatspotted my tires during the spring Pinnacles run, but that's besides the point. Turns out, just as I suspected, that the vibration was caused by suspension tramp which I cured by shotgunning the whole front suspension. Most was worn and or shot, as can be expected after 160,000 miles. A few pieces weren't. The tension strut to subframe bushings seemed fine. Lower control arm to subframe bushings seemed fine and the tension strut to lower subframe bushings weren't TOO bad. Struts weren't as bad as I had let on, but that's ok because I needed that argument to justify some new Tokicos. Subframe bushings were pretty bad and the sway bar bushings weren't too great either. Inner and outer tie rods were shot to ****. Ditto ball joints. Replaced all with new, including new tires to replace the flatspotted tires and my brakes were smooth as silk (keep in mind, I had shuddering brakes before I flatspotted the tires). No need to be at wits end with the brake problem. There are still some worn parts that you probably haven't replaced and if you haven't then they are likely the culprits. I've got a list of all the parts I replaced on here somewhere with a price breakdown from what I gathered to be the most inexpensive source. If you want it then just holler and I'll try to dig it up. Having a list already made sure saves time vs making one yourself....there are a lot of wear parts in that front suspension that are hard to keep track of until you replace them at least once.

rangerj:
Bruce,

Just some thoughts;

LCA strut bushing

inner and/or outer tie-rod end

Weak spring and/or strut

Sway bar bushings and/or end-links

Subframe bushings

In hard braking the weight is dumped onto the front suspension, thus the above thoughts come to mind in re your shudder! shrug rangerj

 

[Bruce]

rangerj:
Bruce,

Just some thoughts;

LCA strut bushing

inner and/or outer tie-rod end

Weak spring and/or strut

Sway bar bushings and/or end-links

Subframe bushings

In hard braking the weight is dumped onto the front suspension, thus the above thoughts come to mind in re your shudder! shrug rangerj

Rangerj and SHOjaun:

You guys have given me some great ideas here and I appreciate it greatly. I will get busy on them. The LCA strut bushing is a definite possibility? We had the right side off and retightened it down but the left we did not have apart. Would I just replace the rubber baby bumpers?

We took the front wheels off and ran the lug nuts down on the rotors and ran the car in third gear and hit the brakes and it seems to also have the same shuddering which would eliminate all of this suspension theory, correct?

I also forgot to mention the car did not do this before the brake upgrade. I also have a brandy spanking new set of tires on slicers on the car.

What I'm going to do Monday night is swap l-r rotors, caliper brackets (I think they are the same?) and pads along with swapping front to rear slicers on the left side and see what happens?

Thanks again for the direction and I will keep you posted!!!

Bruce

<small>[ November 01, 2003, 10:47 PM: Message edited by: Bruce ]</small>

 

[shojuan]

Bruce:
The LCA strut bushing is a definite possibility? We had the right side off and retightened it down but the left we did not have apart. Would I just replace the rubber baby bumpers?

If you replaced the balljoints then that means you replaced the lower control arms and those new lower control arms would have come with new lower control arm to subframe bushings and also new lower control arm to tension strut rod bushings. Did you replace your lower control arms with used parts? I'm not quite clear on what you did there. <strong>

I also forgot to mention the car did not do this before the brake upgrade. I also have a brandy spanking new set of tires on slicers on the car.

This would have been good to know. I'll let rangerj comment.

One thing that sticks out is you said you used antiseize on the pad ends. What you want to use there is a thin layer of silicone grease like sylglide. Antiseize is to prevent galling on bolt threads. A bunch of that antiseize would cook off from the heat of braking. Clean that stuff off and put on some silicone grease. I'm not sure if this could have contributed to your problem so soon. In fact maybe you meant to say silicone grease when you said antiseize. shrug
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[projectSHO89]

If the new LCAs were Moogs and you have oversized rotors, the outer edge of the LCA may be contacting the inner rim of the brake rotor when the front suspension is under the heaviest load of hard braking.

This flattens out the LCA and causes the lower, outer edge of the LCA to rub against the inner portion of the rotor.


I ran into this issue when I worked on Cobria's car last summer. It was necessary to grind down the outer portion of the LCA body to give enough clearance between it and the oversized rotors he had installed.

With the tires on the ground, look at the gap between the LCA and the rotor. If the gap is smaller that 1/4 inch while the car is just sitting there, this is likely your problem.

The casting of the body of the Ford LCAs is a little smaller so they did not rub.

Steve

 

[Bruce]

shojuan:

I replaced the LCA's which have the lower ball joints on them. They are Moog parts and were new. The rubber baby bumpers I was referring to were the donuts on the front end of the LCA strut rod. (I think that's what they're called?)

I did put a tiny bit of anti-seize compound on the ends of the pads where they sit in the caliper brackets. When I swap this stuff around I will clean off the anti-seize and use the Ford silicone caliper grease instead.

Projectsho89

I have more than 1/4" clearance between the new Moog LCA's and the rotor when it is jacked up. I thought I got some grease on the rotors when I lubed the lower ball joints and I took it apart and cleaned the excess grease off and sprayed brakleen on the rotors. I will check the clearance when the car is sitting on the ground. Maybe it gets closer with weight on the suspension?

I may be going to the shop tomorrow to work on the car because it is blocking the aisle in my shop!

I'll keep you posted and thanks again for all the great ideas. I don't know what I'd do without this site?!? thumb

Bruce

 

[SHOspazz92]

Glad to see you made it over here For help Bruce thumb

 

[projectSHO89]

Bruce,

The clearance on Cobria's car was also pretty large with the suspension unsprung. With the weight of the car on it and flattening out the LCA, the gap disappeared causing rubbing.

Steve

 

[Bruce]

Ok Guys, quick update here.

I swapped rotors, pads and caliper brackets from l-r and tires on the left side front to back.

The shuddering moved over to the right side but it had changed quite a bit. It was not nearly as rhythmic and much more sporatic. The more I drove it and applied the brakes the less it became evident. It was wet outside and I was not able to do any real hard braking but I was locking up the front tires and as far as I could tell on the wet roads, the shuddering is now gone. I may have gotten some grease on the rotor when I lubed the lower ball joint, who knows? Then it got on the pad and took a while to burn off? Why that would cause a shuddering is anyone's guess.

Just as a side note, I had about 5/8" of clearance between the lower ball joint and the inside of the rotor in the unsprung condition. It changed slightly when I let it down but not nearly close enough to even investigate.

Now, I just have to bleed the old fluid out of the system, get an alignment and I should be good to go.

Thanks to all for your help and concern. I truly love this car and without this site I would be lost most of the time.

You guys are the best!!!!

thumb beer hail

 

[Dave Romanski]

Bruce,
Guess what? I just did a 96' upgrade on my 95' ATX and have the same problem. The first time I drove it, I braked hard to see how well the brakes stopped and I encountered the shuudering as well. I am still not sure what is causing it, but it seems the more I drive it the less and less it is happening. When I first noticed it, I took it back home and rechecked everything I assembled, not obvious problems. It seems to be happening from both sides. I have a feeling the pads need to wear in too. I am going to drive it some more and see what happens.

 

[Bruce]

Dave:

I would just run it for a while, I think you will be ok?

Just as an update I had the car out yesterday for a little exercise and the shuddering was still slightly present initially. Actually more like a ka-nuking than a shudder.

But I got the brakes pretty warm (without overheating the rotors) and it is now almost completely gone. This was the weirdest thing I have ever seen in 30 years of working on cars.

But those brakes are so powerful I can lock up the front tires if I'm not careful!!

Yeah Baby!!!!! That's what I'm talking about!!!!

Thanks to everyone who helped me through this!! I appreciate it!!

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