does alignment cause brake lock up?

[kepperly]

rebuilt the brakes,(rotors,pads, new caliper seals,and stainless
lines) last spring and have been driving the car once a week since then so I'm sure I have the pads broken in.Last Saturday on a high speed blast to about 120+ a dirt road farmer pulled out from
a side road without looking on to the two lane country black top
I was making my blast on. I immediatly applied brakes and had the right front lock up breifly. I am in need of an alignment but didn't think about that possibly causeing the lock up. what the groups thoughts on this. 87 slant nose turbo look cabriolet.love
leather seats, so easy to clean the after freak out "paste" from.

thanks keith

[Zeke]

Tough question. You might have hit a little dust on the road allowing the RF ot lock up briefly. You might try a couple of hard braking senarios on a different road to see if you can produce the same results. Done any suspension work lately?

[billwagnon]

with good alignment and poor corner balance, your "light" wheels will lock up first

[masraum]

could be car out of balance (corner balance) or it could be that things aren't bled evenly or on of the calipers is somehow different than the other (stiffer or something) I have heard of the new seals being so tight and stiff that they pull the piston back slightly when you let off of the brakes. If one was doing this and the other wasn't that could cause weirdness. Before you worry about any of this I would try some stopping exercises above to check things and be sure it wasn't a fluke or a result of the road conditions instead of the car's condition.

[Tyson Schmidt]

Seems like it's always the R/F that locks up on 911's. This is due, I think to two things.

Porsche (and everyone else for that matter.) builds in a lot of front brake bias so that the car will understeer in panic brake-lock situations. A lot of Track guys dial a lot of this out for better car control. The front always gets more brake bias due to the fact that weight is transferred forward during braking, so the front has more load, and is doing more of the work. But, a little more than is needed is given to the fronts to make sure the car won't spin when the brakes are aggressively applied. (Which is what would happen if the rears locked up before the fronts.)

I think the right front locks up before the left since the driver is adding weight to the left side.

Since the 911 is so light in the front, it's important to transfer the weight forward before fully applying the brakes. There's a method for threshhold braking that involves tapping the brakes to transfer weight forward to load the front tires, then applying more pressure to the pedal once the front is loaded.

If you suddenly nail the brakes, you can be giving them 70% of the braking force while they momentarily only have 40% of the cars weight on them. They haven't had time to load up from weight transfer.

[kepperly]

Really apreciate the response and insight from the board.
I was certain the brakes were ok and haven't had a chance to try to recreate the event . ( hard to try to treshold brake on snow) so
as soon as the roads are dry I will try a hard brake exercise.

Thanks again

Keith

[masraum]

For some reason the right front caliper often siezes as well. Mine did, and since it was fresh in my mind I have noticed several other posts that indicated the same.

[Slider79SC]

I had this same problem. I rebuilt, bled, put on new pads and the problem remained. I took the car in to my local race shop and they recommended a corner balance. We performed the corner balance with me in the car and the problem has never returned. A nice side affect to corner balancing is that the car turns with very equal balance now, both on the street and the track.