Uneven Rear Braking

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Amskeptic
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Re: Uneven Rear Braking

Post by Amskeptic » Mon Jul 01, 2013 8:49 am

vwlover77 wrote:OK, today I verified that the steel lines from the tee to the passenger side rear brake are free and clear.

To summarize:
1. Driver's side rear brake locks much sooner than passenger side under very hard braking.
2. After a normal drive, the driver's side drum is significantly hotter than the passenger side.
3. Shoes properly adjusted with no sound of shoe/drum contact on the driver's side, and a slight rub for part of a wheel revolution on the passenger side.
4. Driver's side drum is nearly new (the old one showed significantly more wear than the passenger side).
5. Wheel cylinders on both sides nearly new.
6. Brake shoes on both sides nearly new (but have plenty of miles to be broken in).
7. Rubber hoses on both sides nearly new.
8. Braking action with the parking brake is equal on both sides.

What gives? Thanks!
What gives? Let's hear your hypotheses . . .

I'll offer this, brake springs different?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Mon Jul 01, 2013 9:48 am

The only hypothesis I've got is that somehow, there is more shoe to drum surface area contact on the driver's side at a given pressure than the passenger side, resulting in more braking on the driver's side. I'll pull the drums and see how much of the shoe circumference has been contacting the drum.

Along the lines of gunk in the brake line, can different springs really make a difference given the hydraulic pressure involved?
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Uneven Rear Braking

Post by Amskeptic » Tue Jul 02, 2013 9:29 am

vwlover77 wrote:The only hypothesis I've got is that somehow, there is more shoe to drum surface area contact on the driver's side at a given pressure than the passenger side, resulting in more braking on the driver's side. I'll pull the drums and see how much of the shoe circumference has been contacting the drum.
If you do not have this resolved by October, you ARE inviting me there to slay this dragon and I will too, with a money-back guarantee.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Mon Aug 05, 2013 5:00 pm

Well, the dragon slaying attempts continue........

I've actually found the exact opposite of my previous hypothesis. The leading shoes on both sides show wear over nearly their entire length. The trailing shoe on the passenger side shows wear on nearly half its length, while all wear on the driver's side trailing shoe is concentrated near the wheel cylinder. So why does the driver's side generate more braking force?
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Uneven Rear Braking

Post by Amskeptic » Tue Aug 06, 2013 7:04 am

vwlover77 wrote:Well, the dragon slaying attempts continue........

I've actually found the exact opposite of my previous hypothesis. The leading shoes on both sides show wear over nearly their entire length. The trailing shoe on the passenger side shows wear on nearly half its length, while all wear on the driver's side trailing shoe is concentrated near the wheel cylinder. So why does the driver's side generate more braking force?
Let's first focus on the uneveness . . . is the driver's side trailing shoe adjuster not sticking out as far as the leading side? It is our responsibility to make sure that the adjusters are even from the first day.

If the "thread count" is even on both adjusters but you have this differential wear, then things are a bit bolloxed. I would then look at:
a) ebrake cable adjustment off? (look at equalizer bar up front)
b) ebrake cable damaged at spring plate area? (sticking inside sheath)
c) ebrake lever not in correct hole of brake shoe web?

This is fascinating to watch unfold . . . :geek:
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: Uneven Rear Braking

Post by vwlover77 » Wed Oct 23, 2013 9:35 am

On Colin's Canton fly-by visit, we made further changes in an attempt to solve the uneven rear braking:

1. Swapped the rear drums
2. Fixed the improperly installed upper spring on the driver's side.
3. Reversed the orientation of the lower springs so that the springs are on the back side of the shoes instead of the front
4. Loosened the parking brake cable adjuster nuts by 2 turns each side to assure that the parking brake actuation is not interfering with the wheel cylinders or star adjusters.

I finally had the opportunity last night to do some panic braking tests on an empty (new) road with no passengers.

Unfortunately, the behavior is exactly the same as before. Slewing to the left with lockup of the left rear wheel. :pukeright:

Colin, I hope I mentioned to you that I had pulled the drums a couple of times to look at the contact areas on the shoes and sanded the "high spots" to try to get more uniform contact across the length of the shoes. Maybe I've fubarred the shoes and should just start over with a new set???
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Uneven Rear Braking

Post by Amskeptic » Thu Oct 24, 2013 8:08 am

vwlover77 wrote:On Colin's Canton fly-by visit, we made further changes in an attempt to solve the uneven rear braking:

1. Swapped the rear drums
2. Fixed the improperly installed upper spring on the driver's side.
3. Reversed the orientation of the lower springs so that the springs are on the back side of the shoes instead of the front
4. Loosened the parking brake cable adjuster nuts by 2 turns each side to assure that the parking brake actuation is not interfering with the wheel cylinders or star adjusters.

I finally had the opportunity last night to do some panic braking tests on an empty (new) road with no passengers.

Unfortunately, the behavior is exactly the same as before. Slewing to the left with lockup of the left rear wheel. :pukeright:

Colin, I hope I mentioned to you that I had pulled the drums a couple of times to look at the contact areas on the shoes and sanded the "high spots" to try to get more uniform contact across the length of the shoes. Maybe I've fubarred the shoes and should just start over with a new set???
Quit stopping so hard . . . :cyclopsani: Problem solved . . . :flower:


Well, now that I have seen the brakes myself, I have run out of options.

Advanced Diagnostics

Pressure gauges on each rear brake line. Have someone apply brake pedal while you read them. Stomp brakes and LOOK at actual pressure rise rates for each.

Replace all rear brake componentry with German-sourced parts.

Test again. If symptoms recur, sell car . . . after mashing the right rear brake line a little flattish.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Thu Nov 14, 2013 6:20 am

The mystery continues. Latest activity:

1. Disconnnected the passenger side brake lines at the wheel cylinder and the tee, blew air through it myself to verify that the line is free and clear.
2. Removed tee and inspected it. The passage from the incoming line to the passenger side line is wide open.
3. Swapped all brake hardware side to side (wheel cylinders, shoes, springs, spreader bar, parking brake levers). The drums were already swapped when Colin visited.

End result? NO DIFFERENCE!!!!!

I can only conclude at this point that the rear wheel alignment is off (possibly from my spring plate bushing replacement a couple of years back) and the rear wheels are steering the car left under hard braking. (?????)
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Uneven Rear Braking

Post by Amskeptic » Thu Nov 14, 2013 10:24 am

vwlover77 wrote:The mystery continues.
Swapped all brake hardware side to side
End result? NO DIFFERENCE!!!!!

I can only conclude at this point that the rear wheel alignment is off (possibly from my spring plate bushing replacement a couple of years back) and the rear wheels are steering the car left under hard braking. (?????)
Naaah . . .

A) Get up to speed. Pre-load the rear brakes with the e-brake. Now apply footbrakes firmly.
Any better? If so, you have a differential in ebrake cables that maybe favoring apply on left side.

B) Back off ebrake cable adjustments by six to eight turns until cables are floppy. Pull each flex cable under the spring plates to release residual tension. Go test.
Any better? If so, you may have an e-brake cable sticking.

C ) Call priest. Perform exorcism. Test.
Any better? If so, you may have an evil spirit lurking in a brake drum.
Colin :geek:
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Thu Nov 14, 2013 5:42 pm

I can already comment on suggestion "B":
I previously removed and lubed the parking brake cables so I know they slide freely and do not stick.

I shall try "A" but I believe only "C" may be effective!
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Amskeptic
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Re: Uneven Rear Braking

Post by Amskeptic » Fri Nov 15, 2013 12:09 pm

vwlover77 wrote:I can already comment on suggestion "B":
I previously removed and lubed the parking brake cables so I know they slide freely and do not stick.

I shall try "A" but I believe only "C" may be effective!
Somehow, all the televangelists here on Florida AM radio know that I have uttered blasphemy. They ALL are promising me personally that I am going to hell.

You ARE going to check "B" Mr. Confidence Himself, by the following:

Have assistant pull ebrake handle while you look at the equalizer bar. See if it "pivots" upon application.
If it does, tell me which side is stretching longer . . .

We thank you in the name of the wholly spirited blessing amen,
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Mon Nov 18, 2013 7:27 pm

OK, so here is a photo of the equalizer bar with the parking brake released....
Image

And here it is with the parking brake handle pulled as far back as I can...
Image

Very little pivoting going on.
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Re: Uneven Rear Braking

Post by Amskeptic » Wed Nov 20, 2013 10:24 am

vwlover77 wrote:OK,

Very little pivoting going on.
Left cable is "healthier" than right cable, it has a shorter travel. I must say, the relaxed position of the equalizer bar looks pretty good.

I am Officially Out Of Ideas. I promised myself that I would retire if ever I found myself clueless in the realm of air-cooled Volkswagens.

Man, what to do next . . . ?
ColinStillClueless
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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vwlover77
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Re: Uneven Rear Braking

Post by vwlover77 » Wed Nov 20, 2013 5:52 pm

I'm still not ready to give up on the rear wheel alignment hypothesis..... :-)
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

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Amskeptic
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Re: Uneven Rear Braking

Post by Amskeptic » Thu Nov 21, 2013 12:49 pm

vwlover77 wrote:I'm still not ready to give up on the rear wheel alignment hypothesis..... :-)
Well. What? I have seen gruesomely gross toe and camber and I cannot imagine that they would affect BRAKING FORCES.

Run it down to Meineke or whoever and get a print-out of your four wheel alignment specs.
Publish . . . here.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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