Have you checked your tire pressure lately?

Aebous said:
So yeah, when does the light activate?
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When one tire has significantly different pressure than the other 3. The ABS sensors relay the RPM's of all 4 tires which are compared against one another. If there's a flat tire it's going to spin at a different rate.
 
Aebous said:
That's what the trunk is for.


On that note, for an 03 at what PSI difference does the warning light come on? Is it based off the 32/36 psi or is it based on the last time you hit the reset button?

Reason I ask is the other day following the track day when it was cold outside I drove to work, went to class and checked it on lunch. My front left was sitting at 26psi and pretty much all the tires were down about 5-6psi. So yeah, when does the light activate?
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Welcome to the backside of a track event. All that hard work on the tires during the lapping sessions that has you frantically bleeding off pressure during the day means drastically low pressures the next morning. Before I got smart and bought a cheapie lighter driven air compressor to take along with me I carried a bicycle pump to an event at Thunderhill on a hot summer day (long before I had a Z4). I had bled off enough air during the day that my tires were radically low the next morning. Getting them back up to highway worthiness in Willows with a hand pump was definitely a character building experience.

I have been surprised at what it really takes to activate the warning light. I had a pretty nasty spike in a tire about a year ago where we had to put the tire back on while waiting for a replacement. I discovered the spike after seeing the warning light and noted air pressure in one tire that was about 6psi below the other tires. I reinflated it after seeing the piece of metal hanging out and went in to a tire place later on at lunch where we found out that the spike was larger than 1/4" and could not be patched. I ordered a new tire and drove the car for 2 days while we waited for the replacement. The leak was slow but I saw that the light would come back on every time the tire got about 6psi below the others. I not am not certain but there did seem to be a threshold for triggering the alarm that was possibly based on the pressure differential to the other tires.
 
Yeah going along that route, there wasn't a significant difference between the tires.
On a totally unrelated side note, I was talking about the event an whatnot with my bud, and for whatever reason he looked at my brakes, turns out my left front rotor has grooves in it :headbang: :headbang: they aren't deep grooves, you have to use your fingernail to feel them, but they are there. So I guess when I get the rear's changed I will get that one turned. The right front is pretty damn smooth. I guess when I dipped the left side off the track some pebbles got stuck :(
 
Quite often the grooving in a brake disc/rotor is caused by the variety of compounds within a brake pad wearing different areas at a different rate. It's quite natural and actually increases the overall surface contact area between the pad and rotor.
 
Curtis said:
Quite often the grooving in a brake disc/rotor is caused by the variety of compounds within a brake pad wearing different areas at a different rate. It's quite natural and actually increases the overall surface contact area between the pad and rotor.
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So that's ok then? It doesn't seem overly bad to me, that'd be great.
 
Don't get your rotors turned... not in this car... just replace them when you replace the pads. It's a little more expensive, but will ensure proper handling and reduce the risk of long term squeaking and shimmering.
 
Aebous said:
Curtis said:
Quite often the grooving in a brake disc/rotor is caused by the variety of compounds within a brake pad wearing different areas at a different rate. It's quite natural and actually increases the overall surface contact area between the pad and rotor.
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So that's ok then? It doesn't seem overly bad to me, that'd be great.
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Yup, perfectly natural!
 
Sweet. Ok, to derail this thread even more and :hijacked:

Is there a seperate procedure for bedding in rear brake pads/rotors from zeckenhouse or is it the same as the front brake?

On the flip side I'm fairly certain the writeup on how they want you to bed in the pads/rotors is based ona full brake rotor/pad swap, but i'd like to hear it from ya'll too. Mind you i'm planning on swapping the lines to steel braided....
 
Bedding the rears is identical to bedding the fronts and the process is identical whether you have replaced the rotors or not. I used to swap out my brake pads for track pads for every event and then go back to street pads after the event was over. Since the goal is to leave a deposit of the brake pad material on the surface of the rotor you actually have to re-bed the pads each time you swap them because the materials in each of those pads is different.

Stoptech has a collection of White Papers in the subject of braking that is one of the best sources of info on the internet:

http://www.stoptech.com/tech_info/tech_white_papers.shtml
 
AlanL, is there a way you could put in a post in the How-to section labeled brake pad bedding procedure etc., for reference purposes? This is really helpful info you post here.


Greg
 
Greg - good call. I just posted a list of references in the Hot-to section for anyone who want lots of bedtime reading materials on braking systems. :thumbsup:
 
It's listed on the door jamb driver's side (I assume they put it there in Britain--in US that's the left side). What size tires/wheels are you running and are they runflats?
 
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