Mike C.

My early 85 has stock brakes except for braided ss flex lines and Axxis Metal Master pads all around. It seems in the last few months that my brakes are easier to lock up than I'd ever previously noticed. I really generated some smoke on a stop today in traffic.. No doubt a lot of it came from the fronts. Question is, how would you know if your rear brakes aren't doing thier part? I don't track it anymore and so no convenient observers). I did some searching here and read that if the rear brakes aren't doing much, the fronts will be easier to lock. Tires are Yoko ES100 but are around 4 years old (replaced with winter tires from Nov. thru April). I suppose it could be they are getting a little hard... Do proportioning valves ever go bad?

Spidey944

Some types of brake pad friction material are very sensative to humidity/temp. My brakes on my truck are very touchy in the morning, but once they get a little heat on them, they dont try and lock up anymore. Just a thought.

944CS

the early cars don't have proportioning valves, the size of the piston, rotor, and pad determine the braking torque in relation to the front

AlpharettaRK

To see if all the brakes are doing their part, do a couple of hard stops and immediately measure the temp of the rotors. An infra-red gun is the easiest way but you can use a tire temp guage or anything else that you can get in there quickly. They will cool relatively quickly so you gotta move. There is temp sensing tape, but I don't think it comes in ranges low enough for street use.
The rears don't do as much, so they will be cooler, (maybe 50-100 degreese cooler?) but still hot
Are your front shocks good? Bad shocks can allow wheel hop and increase the chance of locking.
The way you can adjust bias is with more or less agressive pads at one end or the other. I have had problems with my rears locking on the track so I use a more aggressive front pad than rear.
Cheers
Randy

944CS

I see you live in CT. Do you drive the car during the winter? The sliding calipers can get corroded and the calipers will barely slide anymore. This will cause the inside pad to be doing most/all of the braking. Surprisingly this condition is not as noticeable to the driver as you might expect.

pjburges

One of the first things I did to my car was rebuild the sliding calipers - as theyd worn only one side of the rotor b/c they werent sliding.

Mike C.

Well at least I don't have to worry about a proportioning valve... Good idea with the rotor temps, I have a little digital thermometer that might work. Good call on the calipers too. The car was driven for a few years regularly in eastern, CT winters (not much anymore) and I haven't checked the calipers in a long time either.

J Silverman

My money is on the tires. You are locking them up because you are generating more force than the tires can handle.

billthe3

Have you tried not hitting the brakes so hard? Pedal control goes a long way...

Mike C.

The lockups have been in situations where I wasn't focusing well on the traffic at hand and it's like 'oh **** stop!' It isn't like on the track or a fun road where you can anticipate when to apply breaks.. It's where ABS would come in real handy.... Still, they seem to lock up too easily.