BRAKES PEDAL TRAVEL

[Roger H]

I have experienced this quirk consistently since the rebuild and have checked things over (and over) but can't figure it out

 

After reversing out of the driveway the brakes are applied to stop the car.

 

The next time the brakes are applied (in forward motion), the pedal travel is slightly longer than usual. (enough to put my heart in mouth the first time, as I was near the bottom of a hill approacing a T junction!) A second application of the brakes cures it immediately.

 

I recently read the following (by Chris Witor) which makes sense:

 

"Calipers with large piston area are more susceptible to effects of ‘pad knockout’ - a long pedal caused by any play in the hub, especially due to recess wear in stub axle(s), which pushes the pistons back into the caliper(s). This is most noticeable after using a lot of steering lock, therefore normally occurs at low speed after making a manoeuvre like a 3 point turn, after which the brake pedal will initially travel further than normal."

 

This describes my 'quirk' exactly, but in my case the stub axles (and bearings) are fine.  I also thought the rear shoes may have been installed the wrong way around, but they are fine also.

 

Any ideas??

 

Roger

[Andy Moltu]

It's not just down to wear in the stub axle - the play in the wheel bearing is responsible too. Some people have tried solid spacers for the front wheel bearings to reduce the pads being pushed back by the extremes of the free movement usually when turning from lock to lock. Perhaps compression of the flexible hoses may contribute too?

[Guest P Cobbold]

In my experience nipping up the end float on the wheel bearing (s) invariably cures this symptom.

[Richard Crawley]

Roger,

all I can add is that if it's that noticeable, there is almost certainly something wrong, I have never had such a problem on my car!

[Roger H]

Thanks guys - I've checked the bearing float and taken it to an uncomfortable tightness before easing off a bit and the problem persists.  

 

Andy - I had considered the hoses being the source and braided hoses will probably be my next step (they weren't street legal at the time of the re-build but have since been approved here (West Aust). I don't know how this would cure the problem but I'll do it anyway. If there is an improvement, I let you know. At the risk of sounding a bit thick, where would the solid spacers go?

 

Cheers

 

Roger

[simon tr6]

I had the same problem 21 years ago,i tightened up the wheel bearing (far too much!) And guess what?

The stub axle sheared off, fortunately for me at a very low speed. The ignorance of youth!

 

Simon

[marvmul]

The solid spacers are actually a length of steel tubes + shimms to adjust the end float. The tube fitts between the  inner rings of the bearings . The nut on the stub axle is tightened firmly. The tube helps to prevent the stub axle of bending when cornering hard and the bearings can be fitted almost without any free play.

Brake pads wear out more on the leading end than on the trailing end : perhaps there is soms tilting of the pads and pistons when reversing the car : Roger,did you try interchanging the two pads on each caliper, or new pads?

[Guest P Cobbold]

Are you sure the end float is still OK? Mine can open up within a couple hundred miles or so. The reason is a poor fit of the outer race of the inner bearing within the hub. I'm hoping green Loctite will cure the problem....

The play is easily felt by pulling in/out on the top of the tyre.

[Roger H]

I think you've hit on something Peter - I can vaguely recall when I first fitted the bearings that the race to hub fit was easier than I was expecting (pushed in with fingers, no tools - is this normal?). That being said, the only way I've checked the 'end float' is by grabbing the top & bottom of the tyre and rocking it. When there is no discernable play (and free rotation starts to be affected), I ease off the castellated nut to the first position where the split pin can be inserted.

 

Marv - I have tried changing pads (new - same result), but not upside down. I'll have a look this weekend at what's involved with spacers. Just going from memory though, I can't see what effect the spacer would have as the distance between them is fixed by the hub itself (?)

 

I've been thinking about it a bit more, (and testing!) and the reality is, that it IS the turning of the wheels that is causing the problem, not the braking action in reverse. I got it into my mind early and just kept presuming it was that! Now with my mind out of the straight-jacket, I can get on to solving it (with appreciation of help received!!!)

 

Cheers

Roger