Rear Brake Adjustment?

[J. Huber]

Not really sure I need this but I had a couple questions. First off, what has me investigating is, you may recall I have a high-high pitch chirp once in while that seems to emanate from the rear. It happens when I tap the brakes -- and what's more disconcerting -- sometime when I am merely cruising along. I have been here before with this: many have suggested wheel bearings. It may be but it is not a low pitch or groan, its a dog whistle. And there is no play whatsoever in the rear. Anyway, thought I'd rule out that maybe my brakes were binding or something...

So, I read through the MB CD, and it mentions that rear wheels should rotate freely (when elevated). How free is freely? I checked mine -- they turn but its not like they "keep turning" They go a few inches on each spin...make sense? When I apply the hand brake the driver's side doesn't move at all. So that was good. So how difficult is it to adjust the brakes to ensure freely is freely?

James
63 230SL

[jsaylor]

James,

Have you checked the shoes and drums for wear?  Could be worn out or maybe break fluid has contaminated them.  I'd check them first and if OK then do an adjustment.  I believe that they shouldn't spin to freely.  I would have to have them in front of me to give you a step by step on adjusting.  Pretty simple though.

Good luck.

Jim Saylor
Kauai, Hawaii
'65 230SL

[Benz Dr.]

They should spin freely and similar to the front wheels. Since you will be turning everything inside of the rear axel and possibly the drive shaft it won't turn as long as a front wheel. What you're looking for is no major draging or friction.
When you move the adjusters you will feel the brake shoes start to hit the brake drums. Move each adjuster one at a time in the opposite directon a small amount until the wheel turns freely and leave it there. Too much friction will cause the brakes to get hot which you can check by feeling the rim after driving for a few miles. Sometimes the E brake cables are siezed so check for both brakes coming on and releasing by using the hand brake. This job has to be done whith the wheels on the car.
This only works for 230SL's. 250 and 280 use a different E brake system which can also be adjusted although the procedure is done differently.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[waltklatt]

James, you didn't mention if you had put the car in neutral when turning the rear wheels.  If the tranny is in gear and the engine off, the other wheel will spin in the opposite direction.
Walter
1967 220SL-diesel

[J. Huber]

Thanks all. Yes Walt, had it in neutral. Dr. Benz, very good info. I have to say they are spinning relatively freely -- and not heating up at all. And Aloha Jim. The brakes were completely gone over in '03 or '04. New shoes from Dan, new rear cylinders, hoses, e-brake cable and pulleys, and the drums turned. I think all is still good -- just wanted to confirm there was no binding.


James
63 230SL

[waltklatt]

James,
Also can you describe the situation when the chirp occurs?  Are you braking hard or lightly when the chirp sounds?  Maybe the rubbers are squeaking?  Might try some WD-40 on the rubber joints.
Walter
1967 220SL-diesel

[J. Huber]

Hi Walt. Two situations that result in high frequency chirp. First is fairly common, the moment I tap the brakes at higher speeds... It's not steady -- and goes away if I actually am braking to a stop.

The other: same sound, very intermittent. At cruising speeds (40ish), I will hear the chirp as a bit more steady -- right side. It does seem to happen as I am veering. Goes away on correction. That leads most to suggest wheel bearings. Could be. But not sure.
Which rubber parts would I target?

James
63 230SL

[waqas]

Hi James,

Did you ever get to the bottom of this high-frequency 'chirp' issue?

[J. Huber]

Hey Waqas. Well, honestly, I did nothing (but drive!). I think the brief "chirp" as I tap the brakes down a hill still happens sometimes. The side to side high-pitcher I have not heard in a while. Of course, now that you brought it back to my attention...