front drivers side brake locking

[rsiwicki]

I am wondering now if something is possible an early warning sign of cailper failure. I could not resist a nice wide open freeway yesterday so I wound the speedo up to 125mph and then hit the brakes at about 75% force to see how straight with no hint of any fade. The brakes had never done that before when I had 15" and OEM rotors/pads and I am somewhat surprised that they would do all the way down to 25mph. I have not done this really since I got the new 18" rubber, pad, rotors. Interestingly enough the front drivers side locked for a split second causing a poof of white smoke while I could not detect the passenger side locking at all. The car stopped nice and straight without any fade. I would have thought it would not do this with the more unsprung weight rotating around and stickier tires versus my 15" OEM setup for which I have stomped on the brakes several times from very high speeds and never had any lock up like this. Also I don't recall feeling any ABS kicking in through the pedal, but my attention was on the poof of white smoke as it really surprised me.

Then again on the way home tonight I had to hit the brakes hard at 70mph as an Escalade almost ran me off the road doing a lane change and the front drivers side did the same thing locking for a split second but no smoke this time...just a slight tire squeal.

I have checked the tire and there does not appear to be any flat spotting and the car is still smooth with no vibrations.

Is this normal or is something not functioning correctly?

btw....here is my setup

Powerslot Rotors/Axxis MM/SS Line/Valvoline Fully Synthetic Fluid Fully Flushed & Clear

[driverdriver]

Is there a burning smell........that's how I figured out my calipers where locking on an old Ford I use to own some years ago. That along with a sudden bump while driving at low speed-the calipers would suddenly release.

[rsiwicki]

no burning smell and I forgot to mention that the rotors spins freely with the rim removed. I am concerned that somehow the caliper is acting differently under pressure when brakes applied versus the other calipers and am thinking that maybe air in the lines would cause this?

[AZhitman]

Hmmmmm, weird.

Rotor shouldn't spin "freely", there should be an ever-so-slight bit of drag on it.

Sounds like a bigger issue than that though...

[rsiwicki]

well it doesn't really spin freely as there is some resistance, but I was trying to say the calper is not stuck on their either. All seems to be operating normally except for that very first split second of locking on the drivers side. I am hoping it is just somehow an air pocket in the line causing maybe a slight initial pressurre difference or maybe the tire on the drivers side just likes to grip more than the others. If it is tires, then that will not be a problem as by August the car will need new rubber. After the timing bumped up to 17 degrees the rear end spins freely now like it use to with the 15" tires when I was at 15 degrees.

[DrewQ45]

"I am wondering now if something is possible an early warning sign of cailper failure. I could not resist a nice wide open freeway yesterday so I wound the speedo up to 125mph and then hit the brakes at about 75% force to see how straight with no hint of any fade."

Rsiwicki.... Not meaning to rain on your brake test or anything (Lord knows I'm glad I tested mine while standing still... see "Q45 Brake failure" in the post list).... but hitting the brakes that hard unnecessarily at 125mph is asking for more brake problems which can come in the form of rotor warpage. I've taken my Q up to 155 MPH but made sure I coasted back down from that ungodly speed to a more sane rate of velocity before I needed the brakes. Now if you routinely race your Q, then please ignore this. That said, your theory on the cause sounds logical... I would definately try bleeding the lines at all 4 points and while you're at it, grease the slide pins all around.

...Drew....

[texasoil]

sounds like the guide pins need cleaning and re-lubing. --the right side ones too. Usually air in a line will cause unevenquick apply(stab the brakes and see if one side jerks first--other has air in it.. I think you're lucky not to ruin a set of pads and warp rotors from max effort stop from 125. Rotors were probably hot enough to glow pretty brightly. I hope you drove around some to cool them off before shutdown. Here in Houston, LOTS of brakes warped from heavy braking in wet conditions(stop and go-dragging brakes and then a splash through a cold water puddle.)

[rsiwicki]

somebody has got to put these damn cyrogenetic (sp?) frozen rotors to a test as I hear from other SCCA forums that they do work very well in preventing rotor warpage ...besides I said about 75% pressure, not anywhere near full out braking and I do know to let them cool off driving around before shutting the beast down for the night. And for the record...if you "routinely racing the Q" is qualified as at the 1/4 drag strip at least 5 times per year and 40+ runs not to mention my temporary street runs then I am one happily guilty person. If you note one of my signatures....I use to race extensively in SCCA with a modified Accord and then tried it in the Q, but at that time it was too heavy. Now with the mods it is time to find another SCCA club to run around for 60 secs.

I also just put to shame a 98 4 door M3 from a dude who just moved into my building and thought his little thing was the **** trash talking my car saying how it was all bark and no bite and that his little heavily modded M3 did low 13's in the 1/4. I asked him when was the last time he was at Moroso (being that he just moved down here from WestPalm where Moroso is located at) and he goes....what the hell is Moroso? (clue #1) and then I asked him about his big heavy chrome 18" wheels and how they slowed down the car and he gives me a funny look like I don't know what the hell he is talking about (clue #2).....anyway we went at it three times with two times from a light running all the way to 90 & 75 each time with the beast taking the lead each time but not by much and then we went at it on the freeway after pulling to the side to wait for traffic to clear....well he now knows that my car has one mean nasty bite as I let him have me from 80 till 105 and then I hammered it all the way moving my front bumper from the rear of his car to side by side and then left him wishing he had not run his mouth so much that he did not even bother to slow down after I let off at 145mph and he kept flying pass me not answering any cell calls to ask him what's up....sore loser. The valet guys in my condo loved every single bit of it seeing that I returned with a smile on my face with the other dude no where to be found.

Modified by rsiwicki at 7:25 PM 4/26/2005
Modified by rsiwicki at 7:27 PM 4/26/2005

[maxnix]

What fluid are you using? Did the ABS unit get bled also? The pins are a good place to R&R with some high temperature lube.

Your tire failed to rotate while the others were rotating. Hence, it is flat spotted. The question is by how much. You could probably measure it with a dial gauge.

Nice disciplining of the BMW owner.
Modified by maxnix at 9:44 PM 4/26/2005

[lfootmatt]

I just got done rebuilding all 4 calipers on my J and it was really easy. Joe at Scottsdale has the factory kits for ~$25 each. One kit covers the front 2 and the other the back 2. Front kit might have been more, but was still very reasonable.

They had all the seals, boots, assembly grease and rubber grease.

Easy, easy, easy, job.

Be sure to order the crush washers for the brake line to caliper connection. Stupidly, the kits don't have them.

Enjoy,

Matt

[jamesmost]

Rob sweet spanking , i chewed a little on a Hemi Magnum this morning