Over braking at one wheel?

Northof49 · Posted: Tue Jul 29, 2014 10:20 am Post subject: Over braking at one wheel?

I replaced my entire brake system on my 1973 standard beetle (swing axle). I replaced the front with a disc brake setup. New drums and wheel cylinders at the rear. I am experiencing over braking at one or more wheels. I am not sure which wheel it is, but it is squealing and locking up and hindering my braking. The car doesn't stop a rapidly as it should as a consequence. I suspect it is a rear wheel as I feel no pulling in the steering. Any ideas aside from having someone observe me locking up my brakes?
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1958 Karmann Ghia owner

Randy in Maine · Posted: Tue Jul 29, 2014 10:44 am Post subject:

Which ones are hot to the touch?

Northof49 · Posted: Tue Jul 29, 2014 11:03 am Post subject:

It seemed to that the right rear was the hottest. All were hot though. What would cause one wheel to lock up first and so easily? And why a rear?
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1958 Karmann Ghia owner

Cusser · Posted: Tue Jul 29, 2014 11:38 am Post subject:

Air in the other lines, so the one without air locks up first.
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

Northof49 · Posted: Tue Jul 29, 2014 11:43 am Post subject:

That could be it Cusser. I'm surprised and disappointed the front discs don't lock up first though.
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1958 Karmann Ghia owner

Tim Donahoe · Posted: Tue Jul 29, 2014 1:13 pm Post subject:

Could be that you need a new rubber line to the right rear.

Tim

Northof49 · Posted: Tue Jul 29, 2014 1:23 pm Post subject:

It's all new rubber and steel lines. Not an original piece left. I took it for a run and felt the brakes afterwards. I can't discern that one is hotter than the other. I braked real hard in front of our house and heard one tire squeal. I got out, but unfortunately there is no black mark on the concrete. I will get someone to watch me, and I will lock it up and have them tell me which one it is. I believe it is hindering my overall braking. Could it simply be that one set of shoes is adjusted tighter?

This car keeps me busy.
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1958 Karmann Ghia owner

Tim Donahoe · Posted: Tue Jul 29, 2014 8:03 pm Post subject:

Well, if you have a new disc set-up up front, I'd look to the rear drums for your issue, for sure. One side may be adjusted more. Or the slave on one side is funky (albeit new).

You can always back off the rears a lot (not a whole lot--just so you can see some decent space between the drum and shoe) to see if the issue abates. If so, you know for certain that it's the rears.

When I did my rear brakes recently, I also installed new hand-brake cables and adjusted them per Bently--which was 3 clicks up and the wheels should just barely turn. That was wrong for my car, despite Bently (God knows if I have the original paw in the handbrake). Following the manual, I was going down the road with my handbrake partially on. It took 4 clicks to get it right.

Anyway, try backing off the rear brakes. If the problem continues, I guess it's time to suspect the new front discs. I've not heard many issues with new front discs, though. And if it were one front, you'd think the car would pull a lot to one side, anyway.

Tim

DeathTrap · Posted: Wed Jul 30, 2014 2:56 am Post subject:

Dissasemble and inspect for broken or dislodged components.

That means remove the brake drums and look.

Northof49 · Posted: Wed Jul 30, 2014 6:58 am Post subject:

Northof49 · Posted: Sat Aug 02, 2014 5:42 pm Post subject:

I replaced the wheel cylinder, t fitting and brake line on the side that was giving me air when I bled it. No more air in the stream of fluid. Pedal doesn't seem much higher, but the stopping ability at the point of tire squeal seems a lot better. Still not sure if the front or rear is locking up first.

On a side note, the tightest setting of my parking brake cables goes to five clicks of the handle up at max pull. Everything is new. Is this ok?
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1958 Karmann Ghia owner

theKbStockpiler · Posted: Sat Aug 02, 2014 6:11 pm Post subject:

Can you tell if the front or rear is locking up first from over/understeer in a corner?
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My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask. Smile

Northof49 · Posted: Sat Aug 02, 2014 8:09 pm Post subject:

Oh man, I would be afraid to test it that way. I think I will wait until I can recruit a volunteer to observe my straight line braking. I tried looking for skid marks, but there weren't any. These continental tires squeal quite easily. 195/60r15's.
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1958 Karmann Ghia owner

DeathTrap · Posted: Sun Aug 03, 2014 1:29 am Post subject:

skid on a dirt road

different speeds for different lenth marks

theKbStockpiler · Posted: Sun Aug 03, 2014 6:03 am Post subject:

conventional wisdom suggests that it's your front engaging first. Unless you have substantial weight transfer to the front the fronts are barely needed. This possible situation could be exasperated by having air in the rear lines. I think this is a common problem with adding discs to the front so there should be lots of specific threads on this issue. Some include changing the size of the rear wheel cylinders. Drums have built in assist so when you remove them your pedal effort has to increase.
_________________
My beetle is not competing with your beetle. I have the yellow beetle in my town. There is a red one, a green one ......
Use all safety devices including a mask. Smile

DeathTrap · Posted: Sun Aug 03, 2014 11:38 am Post subject:

Northof49 · Posted: Sun Aug 03, 2014 11:45 am Post subject:

Yeah , I replaced the entire brake system, but was getting air when
I bled the left rear, so I re-replaced the t fitting, line and wheel cylinder on that side in an act of overkill. Those parts are cheap anyhow. Now no more air bubbles when I bleed the left rear.

I did not know that I had to fully back off the parking brake cables to adjust the rear star wheel adjusters. It seemed there was no tension on them with the parking lever down.
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1958 Karmann Ghia owner

DeathTrap · Posted: Sun Aug 03, 2014 11:54 am Post subject:

It seems peculiar that the wheel cylinder isn't part of the entire brake system you replaced and perhaps you have more than one.

yes if left in the "adjusted" or shortened lenth position it will effect the brake adjustment.

adjust drum brakes tight really tight
lost of drag equally tight between between adjusters

pump the pedal a couple times and do it again really tight

when after pumping the pedal a couple times it's still tight drive it

come back do it one more time call it good and adjust the parking brake

Northof49 · Posted: Sun Aug 03, 2014 11:57 am Post subject:

Northof49 · Posted: Wed Aug 13, 2014 11:52 am Post subject:

Problem is gone after (re-) replacing the left rear wheel cylinder and adjusting the front wheel bearings. Some play in the front wheel bearings appears to have had an effect on how aggressive the front wheels brake. ???
_________________
1958 Karmann Ghia owner


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