OSF Brake lock up Update

[Martin S.]

I’ve been doing some work on my brakes and am now getting premature OSF lock up. When I think back it also did this with the old set up but don’t remember it being as bad. It’s not happening very early just when on the limit it’s always that one that locks first.

 

I’ve got brand new (solid) front discs with Pagid RS15’s fitted to standard callipers and Caterham (Lockhead) high friction rear pads which seems to give a good front to rear balance. The car has been corner weighted using Peter C’s balancing trick method (although it was last year) and the calliper pistons are nice and free. My friendly local MOT garage is going to put it on his brake testing rollers on Saturday to see if that shows anything up and if not I will re-test the corner weighting using scales.

 

There are quite a few posts in the archives where this seems for some odd reason to be a fairly common problem. Did anyone that previously had this ever solve it?

 

 

Class 4 Zetec ....nearly there

 

Edited by - martin s. on 12 Apr 2008 23:17:33

[neil.cavanagh]

Martin,

Sounds like you need to eat more pies to even up the left/right balance of the car.... Or 50kg of lead in the boot (right corner) should do it to.

 

I'm happy to help with this if required... 😬 😬 😬

[susser]

Mine generally locks up OSF first, all other things being equal. I find it's easier for threshold braking when I've only got one wheel to monitor.

[Martin S.]

Neil, the full breakfast nudger is on order as per usual Friday morning ritual 😬

[Martin S.]

Thought I'd post an update as there's been a few people with this promblem.

 

I've now had it on the brake tester and the braking force goes up evenly on both wheels, however on increasing pedal pressure to lock up point the OSF locked up slightly before the NSF. So that's it I thought, must be less weight on the OSF all I need to do is set up the corner weights. Not so!....the fronts are within a couple of kg's with in fact slightly more weight on the OSF which shold mean the NSF locks first. So while I had the car level (on my DIY scale system) I checked the camber which showed the NSF at 3.5deg neg and the OSF at 2deg neg. Corrected that and hey presto I think it's done the trick. Now I really wouldn't have expected the camber to effect braking and I can't work out why it should but I guess it could be something to do with the geometry changing differently on each side

 

 

[Richard Price]

Martin,

Are you sure about those camber angles?

Normally, the more negative the camber is, the less braking (or traction off the line) you'll get.

The flatter the tyre sits on the road, the better the grip.

If you'd said that the OSF was -3.5° and it was locking up before the NSF at -2° then that would sound more sensible.

 

Edited by - Richard Price on 13 Apr 2008 06:33:28

[Martin S.]

Hi Richard, Yep I'm sure, I checked and double checked because like you It's not what I was expecting . Maybe it's another factor coming in, perhaps the pads/disks are bedding in some more and have evened things up. The true test will be next week on the IoM hills.