ajrothm

I haven't checked rotor temps. I do know the brakes work better after they are hot and after 4-5 HARD stops... The pulling is reduced and it actually stops straight on hard stops, but still has a slight pull when touching the brakes..

When the car/brakes are cold (say the first 5-10 miles) it pulls HARD right when stabbing the brakes. Seems like heat masks the problem some. All of the calipers have been replaced in the last month... The left front has been replaced twice as has the left rear.

I'm all for thinking outside of the box, problem is, my box is empty. I have done and tried everything I can think of.

Only thing left is to try a brake pressure testing tool and see if the clamping force is the same from side to side.





That would be a good diagnostic tool and quantify if the calipers are working evenly. I hate to dump another $180 for a tool but...It would take a lot of the guessing out of it. I've already spent over $1k trying to get my stock brake system to work correctly. I'm running out of time and money.

ctuinstra

The pressure testers sound like a great idea! You might be able to sell the tool once you are done with it and recoupe most of the cost.

I'll bet there is a bit of fade after a couple of test braking causing the issue to seem less when they are warm.


I know this sounds stupid, but are you sure the tie rods are both in the fast turn hole of the spindle if you have PS? Like I said just trying to think outside.

In my profession I have to do a lot of difficult troubleshooting at times and I have seen some very strange things cause problems (i.e. sunlight, rodents, candy bars).

OMF

Are all your tires worn evenly? Have you swapped fronts and rears side to side for testing? Confirmed tire pressures?
I just can't remember if you did this.....

gungatim

I suggested the pressure tool way back at the beginning...try a good brake shop and see if you can borrow one if you don't want to buy it, but I really think you are at the point where you need some solid data to analyze here. If you really want to get into it, there are a number of factors in play to measure, including pressure, clamping force, pad material and caliper flex. I can send you a spreadsheet with the formulas if you want, I did the research for designing better motorcycle braking systems but you can still use it you will need to know some things such as vehicle mass, static axle load distribution, COG height, Coefficient of friction for the pad material, piston size, effective torque radius of rotor, etc. most all of this can be measured, and you already have the tools with the exception of measuring the system pressures at various points as well as pressure loss.

leadfoot4

Looking at the "underhood" pictures, after the new brake line install, it appears that one of the lines runs somewhat close to the #1 header pipe. Maybe this is heating up the brake fluid, causing a problem?

"AJ", just a simple diagnostic question....when did the brakes last work properly? Think back to that point, and then think what changed, or what WAS changed, after that, that caused this problem to surface.

BLUE1972

Just a thought,

When we were rebuilding my friends 69, he was going to reuse some of the brake components. He had a pulling problem, not bad but annoying.
While I was going over the system when it was apart on the floor one of the blocks, I think it was the rear right had a deformed hole in the block, it never leaked. You could see that it would restrict flow of the fluid to the cylinders. It was either made improperly or smooched when someone replaced the rubber hose in the past.

I convinced him to get all new and the problem disappeared.

OLD SCHOOL TEST (1950's)

car in neutral.
Jack up the rear, take off the tire, use a bungee cord + 2x4 with the steering wheel to apply some brake pressure. Put a short bar across the studs and use a torque wrench to turn the bar. Do both sides to see if you have equal drag. Dial or pointer type torque wrench. They used to make a tool that bolted on to the studs with a nut in the middle ,,,,
A person can't hold equal pressure.

We had a spring tool for the brake pedal that went on the steering wheel and looked like a pogo stick to apply the pressure. It was adjusted by turning the bottom.
Also came in handy for sticking a 3-4 speed after a clutch change.

Hope you find the issue.

mysixtynine

Man you've gone through heck on this... interesting read.

(nevermind onthe relay rod... just checked post and you have power steering, sorry)
Have you ever rebuilt the relay rod end? My ball stud was shot. Seems that gets overlooked. NOT saying thats it. Not even sure how you could test it since it has springs in it. But maybe under brake loading and with the "trutle back" of the road and you pulling wheelies....

I also learned something interesting on my wifes car a while back. I always checked her ball joints at oil changes with a pry bar and the old shake the wheel method.. They always seemed good. Well I never thought to put the jack under the control arm spring pocket to remove the spring load on the joints. The ball joints were sloppy when I removed the spring pressure. With the spring trying to tear them apart the looseness was not detectable. Live and learn.

ajrothm

Round 9

So I come out to bleed the brakes, jack it up, yank the wheels and pressure up the Power bleeder, then I see this:


Leaking where the line goes into the caliper, the line is tight as hell... I pull the line and sure enough, there is a ding in the casting where the copper washer seals, this is the second caliper from O Reilys that has leaked in the same spot with the same type of ding in the casting..

So I blow a gasket myself, call O Reilys and talk to the manager, I tell him I have had to swap 3 out of the 4 calipers I have bought from them. He offers a full refund with core charge refund... I accept and strip it all back down and returned them. They even refunded me a couple Qts of brake fluid.

I called Gulf Coast Corvettes (local to me) and order a full set of stainless/O-Ring calipers. I also decided to change rotors since I have this brake squealing problem that I can not stop no matter what I try. So I ordered at set of drilled/slotted rotors. My original rotors are .010" below min thickness so...With everything else being new, I pulled the trigger on the rotors.

Everything should be here tomorrow or Sat, then I'll reassemble, bleed and go from there. I do not by any stretch think this will solve the pulling problem, however I need reliable calipers that don't spring leaks as a foundation to work with so...back to basics...calipers/pads/rotors and go from there. I will measure the run out on the new rotors and orientate them for the least amount of run out.

Drilling out the rivets:



Yes, pain in the a$$


Cleaned the hubs up to hopefully minimize any run out issues.

OMF

This is a Damn interesting thread...to me at least. Your going to get it fixed for sure

ajrothm

Round 10

I received my super duper stainless/O-Ring calipers from Lonestar caliper and new slotted/drilled rotors and jumped on the install..

First, measure run out:

About .0085".. A bit out of spec.. Rotated the rotor a few times and got it down to about .0075". Still out of spec but...Nothing I can do...Gonna roll with it.

Same thing here:


Stock rotors were only like .004" so...they were more true, as expected since they were machined on the car with the hubs from the factory.

Calipers on, new pads, new rotors




Start bleeding the brakes, get them pretty clear of air.... Pedal is spongy as crap... Keep bleeding...

After about 3-4 rounds of bleeding and pedal spongy, I decide to re-bleed the master cylinder, so I disconnect the lines, put the plugs in, bleed it, jack the rear of the car up and bleed it, I get some air out and the pedal is rock hard with the plugs in...That's good.-- reconnect and start bleeding the brakes again.

Couple rounds of bleeding, pedal is spongy. Then I notice the right front caliper is dripping... clean it up real well and watch it with pressure on the system, leaking out of the bleeder...the bleeder is CLOSED..


I tightened it and cleaned it several times, to the point I couldn't even budge the bleeder...still leaking by.

So I clean it up, tighten the bleeder as tight as I can get it, put this hose on it, and get in the car and depress the brakes and hold them a few times and this is what I had:

So obviously, something is wrong with the bleeder/seat, so now I have to swap out one of my super duper, high dollar stainless/o-ring calipers...which won't happen til Tuesday when the vette shop opens..

So even when I penny up for the "best" repro/reman parts, I still end up with junk.

I'll try again Tuesday. I missed a killer Vette show in Galveston today to work on my own car....hoping for a miracle and good brakes... couldn't even get past the bleeding process...

JEBSi

My guess is that when you brake, the rear suspension gets lighter and extends, then the e-brake cable gets tighter because of the trailing arm lowering/suspension extending which is causing a drag on the e-brake drum system or I could be way off if you have some upgraded e-brake system that the drum brake cable doesn't get tighter when the suspension extends. It does on my 77 with the drum and disc on each side in the rear. We can only guess from behind our computers. Maybe see if the 4 sets of brakes in the rear do not drag with the rear up in the air which is still hard to tell with the drag from the diff. I have rebuilt the trailing arms but I am still a newbie.

OMF

Did you try swapping the bleeder with another?

74 LS4-454

Just thinking out loud...in post #29 you mentioned....
"Round 5

So I come home, decide to try to swap the front tires from side to side...Didn't expect much but it was easy so I did that. Brakes are plenty hot, it did seem that the right side was hotter then the left...Even the lug nuts were hotter on the right."

Looking at another logical point of view,(as if you haven't thought of everything already) the heat on the right side would have me concerned to the point that even though you have repacked the front wheel bearings, could it be possible that the RF or LF wheel bearing(s)may be defective and since you have replaced everything else, maybe replace both front wheel bearings with new????

Great thread, hope it gets corrected for your trip.........Tom

Also on a 74 Coupe I once had was having trouble with the RF also and as another member has mentioned one of the bolts was loose in the steering knuckle, retighten and problem solved.

leadfoot4

With respect to post #90, man that SUCKS!!

Anyway, in an effort to resolve the problem, do you, by any chance, have a drill bit whose diameter will allow it to just slip down into the bleeder screw hole, and whose cutting angle matches the angle of the bleeder screw?

What I'm thinking is that you could use the bit, and by turning it by hand, so as to not bung up the threads in the hole, clean up the "seat" that the bleeder screw sits against, so it will seal.


Just a thought.....

ajrothm

Yeah I probably do...BUT... for $120 a caliper, I'd rather just swap it out and get another one.. I'm heading to the Vette shop tomorrow and they normally have them in stock. Then Tuesday I'll put it on and go from there.


SSROADSTER,

The wheel bearings are perfect, they are older, I've pulled them out, cleaned and inspected them 3 times in the last 2 years. I was going to replace them but once I compared the Chinese replacements to the Timken bearings that are in there, I decided to stick with my old stuff... Repacked and adjusted, I have no radial play at all...Its snug as can be, spins very easily and smoothly.

Also, remember I swapped rotors from side to side and it still pulled right.



Thanks for the comments fellas...

I hope to get the caliper back on Tuesday and HOPEFULLY, the leaking bleeder was the cause of the soft pedal...It basically had NO pedal and that's the first time its ever done that... As much as I have bled the brakes on this thing in the last two months, I'd think I was pretty good at it...LOL

74 LS4-454

I think we are all as excited for Tuesday to arrive as you are....
It will be very interesting to say the least at what finally corrects your problem...... Tom

BB68Vett

I chased a similar issue a number of years ago and it ended up being that the left hand inner wheel bearing race was spinning in the hub. I bought a good used hub, put in new bearings and races and the problem was solved. This was NOT bearing play, the race itself was spinning.

Obviously you have to get your calipers working correctly before looking elsewhere. Good luck with figuring out the issue.

- Mike

ctuinstra

This is thinking outside of the box. I agree, he's on his way to making sure the brakes are perfect and after that it has to be something else causing the issue.

ajrothm

Round 11 & 12

Well the saga continued to the point of desperation....

Last week I picked up the replacement right front caliper that had the leaking bleeder, installed it and it sealed fine. So I bled, bled, bled and so on, so forth, for a solid week. I could NOT get a firm pedal and hardly any stopping power at all. This was the first time this has happened to me.... I pressure bled, 2 person bled, gravity bled, tail up, tail down, hammer this/hammer that...Pretty much everything. Re-bench bled the MC....pretty much everything I could think of, just could not get a firm pedal or any good stopping power.

I slept on it for a few days, talked to Lonestar caliper about the calipers and get some ideas, to no avail...

So I threw the towel in, I took it to a Classic Car restoration shop, they were confident they could fix it... Well after 4 days, and 3 attempts, they somewhat have the brakes working... The pedal is still a bit soft but it does stop decent. I don't think it has the sheer clamping power that I had with the O Reily calipers that would easily lock the front brakes at 40 mph but...it does stop, the pedal doesn't bottom out (although its close), IT DOESNT PULL and it doesn't squeak...

They bled them several different ways, including unbolting the rear calipers and bleeding them in the air with the bleeders pointed up. They also changed the MC again in attempts to gain more brake pressure but it didn't make much difference. They also removed the switch from the proportioning valve and put a tool in there to lock the spool piece to bleed it. So they had it better then I did but....

So I am not 100% happy with the braking power or pedal feel, hopefully its liveable, I am happy with it stopping straight and the system feels "balanced" when the brakes come in, and the hellacious squeaking is gone with the slotted rotors.

I will test it out good this weekend if the weather holds out, if all seems good, then its off to get tires, alignment and hopefully off to Bowlingreen in July...

As for the actual cause of the pull, It "seems" to have been fixed going to the Lonestar calipers vs. the 7 different OReilys calipers I had but, who knows.

I'll report back in a few weeks and update the thread if the car is stopping ok... for the money I spent on this thing, it better be...

OMF

Wow...I feel for you brother, you've done everything except turn the damn thing upside down. I sure hope I don't have any of those troubles when putting mine back together....trailing arms out/ bushing/ bearing change.
Keep your chin up....