SoloRacer

Read this thread

https://www.rx7club.com/vforums/show...threadid=22287

Does anyone know what would cause the right rear brake to lock up like that? My car has ABS and I was going in a straight line when I hit the brakes. I could understand if I was in a corner and slammed on the brakes that the nose would dive taking weight off the rear and that the inside rear tire would have the least amount of weight on it due to body roll to the outside. Assuming all four wheels get equal brake pressure the one wheel with the least resistance would stop first and that would be the one on the inside. Everyone follow me so far? Does this sound accurate? I just turned a corner but was well into the straight stretch when I had to hit the brakes so was it just a coincidence that the tire that was the inside rear locked up? I had my back wheels lock up before in a straight line earlier back in town when braking fairly heavily. It could very well have been the same wheel I don't know. I'm wondering if it's a mechanical failure of either the ABS, pads, rotors or calipers. This week I'm going to have to do some slow speed rapid stops to test my ABS but until then does anyone have any ideas?

Thanks.

Icemark

When you pulled the wheels off and checked the calipers what did you find?

I would be leaning towards something jamming the P brake cable, or a broken/cracked pad.

hard to say without it opened up though.

Thaniel

The caliper could be stuck or the ABS is not working.

Mykl

I notice that if I get on my brakes hard, in a progressively way, not just jump on them real hard, that the rear tires will lock up but the front ones will continue to grip.

Of course it could be a problem with the caliper itself, but I would try to bleed all the lines first and see where that leaves you.

Mykl

Oh, and I don't have ABS, thank GOD.

vaughnc

I know I need some work done on my TII's brake system. Had the "pedal sinking to the floor" problem fixed, but it does fishtail and if I really slammed down I think I would lose control.

The ABS does work though - no tire screetching.

C. Ludwig

iTrader: (27)

When you brake very hard weight is transfered to the front tires which gives them more grip. Wieght comes off the rears and allows less grip. Rears will lock before fronts if all other things are equal. Bias adjuster, factory or aftermarket, and ABS should prevent this. But there are alot of other factors as well. Condition of the brakes themselves has been brought up, but what about the condition of shocks, suspension busings, alignment, and tires? Worn shocks will allows weight to transfer more quickly and create handling and braking problems. Worn bushings can create alignment and binding problems. Cars that are lowered and don't have the camber corrected in the rear will lock the brakes more easily at that end due to less rubber on the road. Old, rock hard tires, or a grippy tire in the front and a lesser brand in the rear can cause problems too. Also note, that even though the RX7 has near perfect front to rear weight balance in a static condition, dynamic loads (even how many passengers or stuff-stereo equipment) is in the car will effect the dynamic handling.

The moral is that if it's not a tire screaching full blow lock in a straight line under mderate braking there might not be anything wrong with the brakes. If the ABS is pumping the brakes and just that one wheel is wanting to lock but the ABS won't let it, it is probably just the most lightly loaded wheel on the car.

Chris

vaughnc

C. Ludwig (chris),

How about springs, when do they need replacing normally?

I know with my 92/91 TII the shocks need replacing (boing boing) and I'm not sure if the suspension bushings would help that much. Of course I've never driven a TII with good ones either so I don't know what they feel like.

Great info, thanks.

C. Ludwig

iTrader: (27)

Well springs shouldn't really be part of the equation. Springs don't really lose rate over time. They will tend to sag, but the rate remains very close to original. A common trick among Showroom Stock racers is to find old "wore out" springs that have sagged in order to lower their cars but maintain the same rate.

Chris

Thaniel

I had problems with the rears locking and it turned out to be the fronts weren't getting enough bite. Found that out when fixed up the rear brakes and the problem got WORSE. Did the fronts and now everything is back they way it should be.