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MG MGB Technical - Brakes

The brakes on my GT are pulling a bit to the left on the first sharp press of the pedal. The car pulls up straight if you let up then press again. I'm reluctant to rush in and change the caliper as it was rebuilt less than a year ago (new hoses at the same time), but it seems the obvious thing. Any ideas for alternative culprits before I rush in? If not, I think I'll try stainless pistons this time as the calipers seem to give me problems rather too frequently.
Steve Postins

Your assessment is probably correct (many of our callipers are getting on now) but don't rule out the rear adjustment - incorrect adjustment can have a similar effect.
Roger
RMW

There's a distinct possibility that this is not caused by brakes at all but by the rear axle U-Bolts being slack and allowing one side of the axle to move forward and rear steer the car. Certainly worth a check before you go out and spend money on new pistons
Iain MacKintosh

Also check that the pads have their cutouts aligned properly. That can cause all sorts of stranges effects.
Miles Banister

Thanks guys. I've alreaady adjusted the rear brakes and will check the other two options. The rear axle idea in particular made me think - I'm sure the MoT tester made a comment about one of the springs last time around.
Steve Postins

When I first bought my GT, I noticed it was pulling to one side. Thankfully I didn't ignore this and inspected the brakes and to my horror found that the spring clips hadn't been fitted one of the front calipers and the pads had twisted, bearly beening held in by the pins.
S Longstaff

Could this be air or moisture in the system on the one side, which may explain why a rapid second pump doesn't pull to the one side?

The second pump tracking straight could also explain one rear brake being out of adjustment compared to the other, as RMW points out. When my rear shoes have worn down somewhat, I start to notice that on the first pump, the pedal goes down quite far, and with a quick second press on the pedal its right near the top again - I imagine that if one adjuster is loose, the effect would be less grab on that side initially. Of course now that I've re-read your second post, you've already checked this!

Iain - if the U-bolts are loose on one side, would the car track straight on the second pump, or keep pulling to one side?

Have many people had caliper problems? Mine have been ultra reliable since I first bought my MGB in 1986 (I say that hoping I won't discover a siezed one tomorrow!)

Erick
Erick Vesterback

Car would still pull to one side on the second pump if the U-Bolts were slack but I have a feeling that once you compensate for this on the first pump you won't feel it anyway the second time as you are already braced for it happening.
Iain MacKintosh

Thanks everyone,
I've checked the U-bolts and they are all tight but I'm going to have to get new rear springs soon as a binding has broken on the one, meaning the leaves are pushing apart. Not sure if this accounts for the issue at hand but it can't be helping anything. I'll have a close look at the calipers next. Iain, you have a point about the second press. It certainly feels straight but then the car is going slower too. I'll conduct a couple more emergency stops when I'm passenger-free and see what happens.
Steve Postins

Just to update, having been unable to decide whether the problem was front or rear, I decided to get an answer the quick way and paid a visit to my local garage's brake test rollers. Unfortunately, there was nothing to report, with good even braking front and rear.

On the road the left pull was still there on the way to the garage, seemed to have cleared on the way back, then after a few emergency stops it returned, only this time pulling to the right! I can see this is going to be "one of those", but I'll probably target the rear springs as they are overtly tired and a little voice is reminding me to fix the things you can see are broken before all the others.

Thanks all
Steve Postins

If the brakes are showing to pull evenly on the rollers then it must be a problem in the rear springs/mountings. If the U-bolts are tight is there a broken leaf in one of the springs as your car seems to be showing the effects of rear end steer.
Iain MacKintosh

Cheers Iain, I'll get them ordered.
Steve Postins

Steve,

I recently had rear steer problems which were sorted out by rebushing the rear suspension. I was really noticing it when I floored the throttle or suddenly lifted. The car would lurch one way and then the other. The springs seemed fine and were reused. I found three problems, which probably all contributed.
1. One rear damper bolt was a touch loose which i think allowed a small amount of movement.
2. Very worn rear shackle bushes (all the way through!).
3. One of the locating plates for the rear spring pads had ovalled holes.
I made some notes about the work I did and took some pics in my blog on mgbclub.com. Have a look at http://www.mgbclub.com/cgi-bin/mb_blog.pl?uid=2&bno=1 and the entries at the end of Jan.

Iain
67 BGT

PS My car pretty much braked in a straight line.
I D Cameron

Great stuff and you've inspired me to take a few pics as I go. Were the Superflex bushes worth the money?
Steve Postins

Steve,

"Were the Superflex bushes worth the money?"

It's difficult to say!! Rubber bushes are a few pence each. Superflex are quite a lot more! (About £50 for the rear end including front spring eye bush (x2), rear shackle bushes (x8) and rear spring pads (x4), rubber would have been about £10-£15 I think). I'm sure the new rubber would have had a similar effect for a while, but the superflex should last much much longer. As I do 150-200 miles a week I thought it worthwhile. It has stiffened the rear end up a bit. Still a decent ride, but more understeer in the wet and when it goes at the back it is a bit sharper and less progressive! However, the front needs rebuilt and I have superflex bushes for that as well. I think once that is done the balance should be restored! I've always been told that you want to stiffen the front and leave the rear soft on a B. As I have done the rear first this is the wrong way round, but due to the rear steer I had no choice but to do the rear!

Iain
I D Cameron

One other thing. Have you checked the fluid level in the rear dampers? Very easy to do via the plastic grommits over the rear wheel arch. If one has leaked then that is another possible cause.

Iain
I D Cameron

Hmmm... I do a similar mielage and have got red polyurethanes all around, although they are about 10 years old. I might give standard rubber a try and see how it rides. The dampers are Konis but good point. I'll be having a good look at those too.

Steve
Steve Postins

Hey Steve,

You might check to see if your 4 front cross member studs are tight, or the rubber pads between the body and the cross member are in good shape. This happened to me years back. Over the years, as my pads crushed down from age, it loosened up the cross member and created the kind of issue you are talking about. If that cross member is not anchored, any movement in it due to applying the breaks would cause a funny twitch in the cars attitude, and it might not always be consistent to one side or the other.

Gregg Hanks
73 MGB SC
63 MGB
69 MGC GT
70 E-Type 2+2
g hanks

Sounds nasty! Thanks, I'll add it to the other checks, at the top.
Steve Postins

Steve

If you still have the correct ride height in the back don't be in too big a hurry to replace those springs. You say that "a binding has broken" If this is one of the steel clamp around the spring replacements are available from any good shop that deals in leaf spring suspensions (hot rod, truck etc.).

FWIW

Larry

Larry Hallanger

This thread was discussed between 22/02/2007 and 28/02/2007

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