Chim Brake Effort

[the dodger]

Had my MOT on Saturday - last minute booking where I usually go and they fitted me in during the afternoon. Anyway, labour a bit thin on the ground and it ended up wih the Owner (nice chap - 50-odd, petrolhead with a few classic cars) doing it with MY assistance! Great, I though, no problem. When it came to checking the brakes I had to almost put my foot through the floor to attain an acceptable reading. Balance wasn't too bad (9% I believe) but the effort - I'm sure would be more than the fitter would exert. Pads are OK, new ones on rear last Oct. but were std Ford from local motor factor.

Fact is, they don't work very well on the road either!Any ideas?

[dannyboyo]

Is this on the front wheels or the rear? I heard that the limited slip diff buggers up the readings on those MOT brake checkers, or is it they the checker buggers up the LSD, can't remember!?!

Also, being that you've got an L reg I think the front brakes are quite small, same as mine were on my N reg, but the previous owner burnt the discs out on a track day and had them upgraded to the larger 280mm discs I think. Maybe that makes a difference.

Other than that, get the master cylinder checked out i guess, change the brake fluid, put different discs on..... etc

[xain]

I did the same thing and I noticed that I got a higher reading on the rears from teh handbrake than I did from teh foot brake. I think there's a valve to cut the power to the rear brakes, or proportion it better to the fronts to prevent the rears locking up.

[the dodger]

Cheers both. I'm not sure if it's the rears or fronts - or both! Subjectively the handbrake seems to work OK - but even that required monster effort to get the dial round a bit. Maybe I'll try new front pads and a fluid change first. When the weather warms up a bit.

[GreenV8S]

Hope you had the engine running, if not that's your problem right there. Otherwise, if you have hard pads they may not work very well at low speed from stone cold, but should work better if you get a little heat in them before turning up at the MOT station.

[the dodger]

Yes Pete, engine running. The week before I tried a bit of a test on a country lane and the first time it took about 500yds to stop from about 40mph! Next time it got a little better, next time I actually managed to lock a wheel! This was pressing as HARD as I could!

[shpub]

Standard Ford pads UGHHHHHH

Probably glazed over so need throwing away. If they were new it could be they need bedding in. Could also be sticking callipers. Could be a fluid leak or contamination. Could be a duff servo so you aren't getting the normal force applied.

[5ltr-chim]

Needles ?? - You should NEVER let them test the rear brakes on the rolling road - it can damage you limited sip diff!! - they need to use either a technometer or a decelerometer. Not that it helps you in real world braking though.

[alex.mcintosh]

Depends who you talk to about rolling roads damaging the LSD...some say it does, others it doesn't...

[the dodger]

Ref to dyno brake test I mentioned this to the owner. He ought to know (he has a few cars with LSD). The only problem would be if you tried to drive one wheel whilst restraining the other. This is not the case with this equipment and he assured me it was OK. I've used this place for about 10 years and they are generally competant and know about cars. And they do a proper test! 5Ltr-Chim - what's "needles" about?

Yes Steve, they were all I could get at 4.45pm on a Saturday. I thought they would be OK as they are only on the rear and the worse to happen would be they wore out quick. May try a few more emerg. stops to bed them in. Callipers are are OK and not binding and discs look good, not scored. He tested the vac. actuation of the servo on start-up but this would only be a guide to effectiveness.

[shpub]

OK 4.45 on a Sat Afternoon is an acceptable excuse. Please reduce the UGHHHHH to ughh

I am wondering if the master cylinder is on its way out. Had this at the weekend on the 520 where it would stick and lock the brakes up or stick so there was no or little braking at all. Had to chnage the MC in the end. Easy on the Wedge, swine on the Chimaera.

[taylormj4]

Have a look at your discs - get under the car and check how shiny they are after you've driven around a bit. If they're not shiny over the full conatct width of the pad, the pad isn't making full contact with all of the disc.
This seems to be a problem on Sunday-only TVRs as the discs get wet (washing car or rain) and then the car gets put away in the garage for the discs to corrode.

When I bought mine only the inner half of the pad was touching the disc as the outer half had corroded erroded away from the pad.

Matt