TR5

[JRCWeedon]

Not being used to servo equipped TRs I would appreciate some advice.

I have replaced the following on my competition TR5 rear wheel cylinders, linings, front discs rebuilt calipers (from an E type) and green stuff pads.

All works well apart from the pedal travel - should the pedal operate at the top of the travel or is some play acceptable - if not what is causing it the servo?

All contributions gratefully received

Regards

John

[Richard Crawley]

Hi John

Pedal travel should not be excessive at all, have you checked the clevis pins & associated holes are not worn; the servo won’t cause it. I’ve no experience with competition mods so the unknown entity for me are the E type callipers, is this a recognised mod, I thought twin pot Princess callipers were the ones normally fitted! Have they only just been fitted? Was it OK before? Are the servo & master cylinder in good condition.

[JRCWeedon]

Hi Richard

The calipers came on the car they are the 3 piston sort 1 large, 2 smaller.

I most admit I haven't checked the clevis pins I had better do that. The master cyl was replaced about 18 months ago before I bought it. I have replaced the fluid so it is always possible there is some air in the system somewhere otherwise I am a bit stumped.

Regards

John

[Richard Crawley]

Hi Richard

The calipers came on the car they are the 3 piston sort 1 large, 2 smaller.

John

Are you sure it's not those 6 caliper pistons that are causing the problem! It may be that the piston diameter of the standard master cylinder is not sufficient to shift the required amount of fluid, hence the long pedal throw. That's why I asked if it had been OK previously!

[jean]

Richard is probably spot on, the well known Toyota caliper modification seriously increases the pedal travel.

So there are good chances that, as mentioned by Richard, the relation between m/c and caliper is causing the problem

jean

Edited June 28, 2006 by jean

[JRCWeedon]

Thanks Guys.

The pedal travel is no worse than when I got the car which I then put down to fag paper thickness of friction material on the pads.

I have bled the system again and the clevis pin etc is fine so I think you are probably right. I can live with the travel I was just concerned that something might fail at 130mph approaching Woodcote Corner at Goodwood ( particularly if my son was driving it! ).

Thanks for your help

Regards

John

[Richard Crawley]

Thanks Guys.

The pedal travel is no worse than when I got the car which I then put down to fag paper thickness of friction material on the pads.

John

It doesn't matter how thin the pads are, it won't affect the pedal travel. As they wear down they always remain a gnat’s wotsit from the disc. The fluid level in the master cylinder gets lower as there is more of it inside the caliper pistons but you should never routinely top it up, as long as the fluid level is above the minimum it’s OK. Top up to the max line only when you’ve fitted new pads, otherwise you’ll end up with fluid everywhere on the bulkhead when you push the caliper pistons back in to fit the new pads.

[marvmul]

John, if I understand you correctly, the pedal is only starting to pump brake fluid when the pedal has already travelled over some distance. This shouldn't be so : it means that the piston in the master brake cylinder doesn't return far enough : a spring in the mastercylinder makes the piston return fully, allowing fluid from the reservoir entering the cylinder. There is also a small valve, operated by a washer like spring : this is shutting off the entrance to the reservoir and opens it when the pedal is released. Perhaps the master cylinders components should be compared with an explosion drawing in a Moss cataloghe or workshop manual?

It is possible to check if the piston is returning fully by removing the rubber sealing cap of the mastercylinder, on the pushrod side of the cylinder : if it does, the pushrod or pedal should be adjusted.

Edited June 29, 2006 by marvmul