Poor brakes = Bent rear stub axle? (long)

[JsnPpp]

Hi Folks,

After 5 years of ownership I think I have finally isolated my brake problem. Let me get your opinion.

No matter what I did when adjusting the rear drums I could not get rid of the massive DRAG-NO DRAG-DRAG-NO DRAG that was happening. It was almost an ON-OFF type of thing. So, I did the best I could and adjusted it so there was a light drag at it's worst spot.

Car has 2002 Turbo disks and drums but has never been as good as my stock Tii's brake system. It's good, but not great, know what I mean? When I push on the pedal, car stops but needs more travel than I would like and it's not as firm as I would like. Not mushy, but not as good as my other car. I would probably not complain if I didn't have the other car to compare!

I have replaced all the following during the last 5 years::

- Brake, clutch slave hoses

- Hand brake cables

- Rear drums + shoes

- Front disks + pads

I've bled and rebled and rebled... Today I carefully spun the drum while holding a flashlight behind and comparing it to a very close piece of wood underneath. I can see the drum moving up and down by as much as 1mm. I know that a very small wobble can make a huge difference in the feel of the brakes. Here is my setup:

Could it be Bent rear stub axles? Both sides do this. I need to check the stub axles for the same wobble because what I am seeing may just be casting error in the drum itself..

What are your thoughts? Anyone else have a severe drag/no drag? What was the problem? I feel that I know how to adjust rear drums because I adjust my other 02 yearly and it works great.

Am in Austin, if someone is near and feels like a beer and take a look, just give me a shout. Got a full fridge in the garage.

Thanks for reading!

-Jason

[gracer]

Remove the drums and do the same thing with more boards. That will tell you if your stub axles are bent. G

[BillWilliams]

Both the drag no-drag and the too much pressure needed.

This is happening on P2. The "need too much pressure" has been an issue since I put the car on the road last year.

The drag no-drag is new to me. I to have adjusted and readjusted the brakes with no success. It looks the rear show on the driver's side is what is dragging and only the lower half of that show. It is dragging where the e-brake attaches.

I took one more shot at adjusting them Friday but we have had some snow and I worked at picking up leaves today so the last try has not been tested. Maybe tomorrow.

The low pedal pressure issue, I am thinking I do not have the bar from the pedal to the bell crank on the brake booster tight enough. I have not spent too much time on that issue yet. The brakes do not get tighter when pumped and stop well once you really get on the pedal.

I have the big brake set-up.

[robspeed]

take drums to wheel/brake shop and havem checked for runout. if they come out @ spec, then suspect the axles. axles, stout. drums, fungible...

[Guest Anonymous]

No matter what I did when adjusting the rear drums I could not get rid of the massive DRAG-NO DRAG-DRAG-NO DRAG that was happening. It was almost an ON-OFF type of thing. So, I did the best I could and adjusted it so there was a light drag at it's worst spot.

Car has 2002 Turbo disks and drums but has never been as good as my stock Tii's brake system. It's good, but not great, know what I mean? When I push on the pedal, car stops but needs more travel than I would like and it's not as firm as I would like. Not mushy, but not as good as my other car. I would probably not complain if I didn't have the other car to compare!

I have replaced all the following during the last 5 years::

- Brake, clutch slave hoses - Hand brake cables - Rear drums + shoes

- Front disks + pads

I've bled and rebled and rebled... Today I carefully spun the drum while holding a flashlight behind and comparing it to a very close piece of wood underneath. I can see the drum moving up and down by as much as 1mm. I know that a very small wobble can make a huge difference in the feel of the brakes.

Could it be Bent rear stub axles? Both sides do this. I need to check the stub axles for the same wobble because what I am seeing may just be casting error in the drum itself..

What are your thoughts? Anyone else have a severe drag/no drag? What was the problem? I feel that I know how to adjust rear drums because I adjust my other 02 yearly and it works great. -Jason

Jason:

Bent half shafts could cause a wobble/vibration, but that should not translate to braking issues - and it is even less doubtful at low speeds. Out of round, warped or unbalanced drums would be more likely to cause your problem though. But I do not think any of those things are your real problem. Can I guess that your car will roll with little resistance at some times, but at others (without any real change of circumstances) you need to really push much harder to get it to roll? At very low speed like coasting a few feet in traffic, the brakes seem to apply themselves?

I noticed you omitted any mention of replacement of rear wheel cylinders. You can rebleed them all day long, but if one of the two opposing pistons hangs due to wear, dirt, corrosion, inappropriate fluid, bad seals, or even air - you may get the symptom you described. Inconsistent pedal behavior also points to this or some other hydraulic issue.

This dragging brake phenomenon has been addressed on the forum before. Look at a new wheel cylinder and you will notice that both pistons float back and forth and accommodate minor irregularities that might occur with heat cycling. If only one piston moves, the brakes will work, but the tension applied to each shoe will not be balanced. I have had this problem where cool (rear) brakes seems trouble free while warmer brakes may seem tight at only certain spots when you hand rotate the wheel.

Years ago, I had a brake specialty garage misdiagnose this problem on my then girlfriend's car. They tried to convince her all drum brakes did this especially with limited slip differentials and sway bars. This might have been the case before disk brakes when some racers used solid metal shoes that greatly expanded when heated and rapidly killed wheel bearings due to the same heat, but I knew better. This is typically not the case with 02's.

hth! Make mine a Lonestar!

[c.d.iesel]

YOU DON'T SAY if the parts (rear drums and shoes)

were USED ?, or new parts.

if used - get new drums right now.

if your not trusting your stub axles (the flange

is where it would be bent) then remove the rear

drums, and with a DIAL INDIACTOR - MEASURE

THE RUN-OUT at the flange face where the rim

with the machined flange - to the outside of the

wheel studs. If the flanges have been beat?,

hammered?, in an accident? sometime duing the

last 30 years?, then replace the stub axles with

the outer wheel mounting flanges - WITH NEW PARTS.

AS SUGGESTED ABOVE, while your drums are off to

measure run-out of the flanges - have a 'brake' shop

spin your drums on their truing machine. If they need

much cutting - there toast.

It will just confirm that the drums WERE out-of-round - buy

NEW DRUMS. AND - if someone has been prying?,

wedging?, beating up the shoes that are on the car ?-

that's another source for the irratic behavior of the rear

drums. BUY NEW SHOES. Beginning to see a pattern?

Used suspect parts = krap performance, no reliability,

and repeated labor. Forget the 'turbo' stuff, just refit

'stock' tii components(new) and be happy with

safe stopping power.

Then shine a timing light on the motor.

[peteinjp]

I'm down for a Shiner. See ya at the short horn lounge when i come net summer- if that place is even still there?

I'd pull the drums and run them over to a good brake shop. I've had similar issues on front rotors and i think it was from jamming on the brakes at speed down to a full stop and keeping the pads on the rotors super hot while they were super hot. No idea if this might be your problem but a brake shop could tell if the drums are out or not. The parts on now- whats the history? Newish? On the car when you got it? I find it hard to believe that both stub axles might be bent the same amount.

[allbim]

If the stub axle is bent, then the hole in the center of the axle will move up and down when you rotate the drum or wheel.

The hole is exactly in the center of the axle.

It was used to support the end of the axle during machining.

[JsnPpp]

Great feedback - thanks folks!

I removed the drum today and checked the stub axle flange. I see very little out-of-round (radial) movement (1mm or less), and about 1mm run-out at the outer most point on the flange. I know that a slight change in rear brake adjustment results in a dramatically different pedal feel, so am still thinking this is the problem.

Like Bill said is happening with P2, pumping the brakes do not give better brakes. And it has the low-pedal problem too. I have not yet checked the bar from the pedal to the bell-crank on the brake booster yet.

As CD asks, the drums are new (all parts were replaced with new) and I even had them checked for roundness last time I was trying to figure out the problem. The only old parts in the brake system are the actual front calipers and the rear cylinder/pistons themselves. CD thanks for the diagram.

I still feel that something is "out of round" because I can feel the massive drag/no drag by simply adjusting the two 17 mm adjustment bolts on the back of the backing plate. There isn't a way to adjust the brakes so that there is only a light drag around 360 degrees of the circle. It's all on for 1-180 degrees or so, and all off for the rest.

I think the long pedal travel is a result of this problem - the rear brakes are adjusted out enough (to allow them to spin) that I have to use 1/2 the pedal travel to simply push out those rear pistons to grab nicely!

I suppose I am answering my own question here. The car is 35 years old and I am sure has slid into a curb at speed enough to bend the flange face slightly. I don't know for sure but it seems very possible.

Enrique, I like your line of thought but haven't yet noticed a time when the car doesn't have this problem so I can't attribute it to temperature just yet. Not ruling it out tho!

Peteinjp - do you live in Austin when not in Japan? I agree with you that it seems odd that both stubs would be bent the same amount. In fact hardly likely at all. Man, if I rule out the bent flanges I am not sure where to turn!

Not sure if I am any further along here, but I do appreciate the time you all took to write a reply and I will let you know when I figure this out. Again, give me a shout if you are in town, beer fridge is full and right in the garage. Maybe that is part of the diagnostic problem. :-)

-Jason

[BillWilliams]

I took some time, with the car on stands and adjusted the rear brakes as best as I know how. Let each shoe drag a bit and then slightly back off. Did this on all four shoes.

The front shoe on the problem brake, driver's side, was way too loose before I spent the time adjusting. The drag no-drag got better and only manifests itself at full brake pedal presssure. The sound is not there with no or slight brake pedal pressure.

So it did get better but I still have the sound and the obvious drag no-drag.

I now wonder if the emergency brake is pulling the rear shoe somehow or rubbing on something making the noise. That is my next step.

Plus I still need to pull the carpet and adjust the bar.

Sorry to be jamming up your thread. Hopefully your resolve will help me with mine.

[JsnPpp]

Not at all Bill. Sounds like we have similar symptoms, but I am thinking mine is a tad worse. :-(

Both sides exhibit the same symptoms, which is making me start to believe that something more basic is the problem here.

Car has 2002 Turbo front disks/calipers/etc. and supposedly 2002 Turbo rear brakes as well. I know that the rear brake parts (at least the drum) is the same as the e21 rear drum. I looked at realoem and saw that I have the e21 shoes on it, but honestly I don' t know if I have e21 throughout, or 2002 Turbo with just an e21 drum. I don't really care, but I want to make it work and get the right parts.

Regardless of the shoe, I can't get away from the feeling it is out of round somehow since when I adjust my eccentrics (for any of the four shoes) I have the heavy drag/no drag. So much so that if I try to have it lightly drag on the "free portion" then there is no way the wheel will turn on the portion that drags. So in the past I have adjusted it so that it lightly drags on the portion that drags the most - leaving the free portion to move very freely indeed.

I want to make sure it's not the stub axles that are bent. But like Peteinjp says, what are the odds both sides are bent the same?

Sigh.

-Jason

[peteinjp]

I grew up there and I miss it. I left when I was 19 or 20 in 1990 or so. I get back at lest once a year to see my family there.

Jason- what master cylinder do you have? THe standard 02 unit is 4 mm smaller than the tii and turbo units as per real oem. If you have the smaller unit in then your pedal rtavel and feel may be separate issues.

IF that is the case then:

When i adjust my drums I jack the car up supprt the swingarms bolt on the drums only and run the car at idle in gear. I have an lsd so if there is some drag the axles keep spinning. I adjust each adjuster to have as little drag as possible and more so the same amount of drag. Basically when I can just tell its dragging I leave it there. If you think about it just because its dragging unevenly at low to no pedal pressure doesn't mean it will exhibit any adverse effects when you are actually using the brakes. I guess where I'm going with this is that Ifn' it were me If I couldn't tell the difference when I'm driving (given your pedal reavel/pressure issues could be solved with a cyliinder of larger diameter?) I'd set it and forget it.

[BillWilliams]

Jason, have you completely taken the emergency brake out of the equation? Maybe try releasing the emergency brake completely free from the arm inside the rear drums and see what happens.

Can you tell which shoe is dragging on each side? Front shoe, rear shoe....

I am thinking new drums and shoes maybe the cheapest and quickest way to get to the bottom of these issues. However, my drums and shoes are less than 7 months old.

[Ian]

Years ago I had a problem with my rear drums dragging. I couldn't adjust them for the life of me. Turns out the pressure switch (#1311360940, 1 in the pic) for the rear brake line was malfunctioning. I removed the switch and the problem went away. I installed a Tilton adjustable proportioning valve so I did not replace the factory switch, but they are still available and fairly cheap.

Ian

'76 M2

[JsnPpp]

Good thought Bill - yes, I actually completely removed the 4 10mm nuts on the emergency brake so the cable is quite free. Unfortunately!

I will check today to see if it's only one of the shoes on each drum that is causing the problem - or both. For some reason I thought it was both.

If it was only a little dragging problem I wouldn't care so much. But maybe you guys are right, if I can adjust the brake pedal height in the pedal box (haven't done this before need to check it out) then perhaps all is o-kay. While I have the drums off I will make sure the pistons in the cylinders are moving freely.

My parts are all new (except for rear cylinders and front calipers) and about 5 years old, but no more than 5k miles on them. Probably more like 2k!

Pete next time you come to Austin, give me a shout! Ian, thanks for the thoughts there, I will give it a look-see as well.

I'll report back, thanks for all the input!

-Jason