Symptoms of pad fade

[Sleeper519]

Originally Posted by dparm

Thanks for the tips. Sounds like the SP pads should be okay since I'm not even maximizing the car's performance on the tires just yet.

My PSS should be toast sometime this summer and I am probably moving to the AD08R in the same size.

Agree with dedicated track pads, especially with BBK. any mid-torque compound should be sufficient on street tires.

As for tracking the PSS, I personally would start at 29-30 cold and shoot for 37-38 hot, bleeding off anything over 38 immediately after each session as the day goes on or else the tires get greasy.

One problem though is the PSS sidewall isn't the stiffest, and low-ish pressures will allow the tire to roll more and shread the outside shoulders quicker, unless you have mucho neg camber, in which case the inside shoulders will wear on the street over time ('tis the tracker's dilemma ).

[YMB_M3]

Originally Posted by dparm

Maybe I didn't phrase my original question well, so I apologize. What I'm trying to understand is the difference between pad fade and fluid fade (boiling).

Is pad fade going to be a firm pedal but greatly reduced stopping power, whereas fluid fade/boiling is where the pedal just goes to the floor/has much more travel?


In the interest of full disclosure, I have some track days scheduled at courses with some very long straight sections. At a previous event at one of those courses, I was doing 110-120 at the end of the straight section and had to bring the car down to about 40mph.

To my understanding:
Pad fade will be a firm pedal feel with reduced stopping power and fluid boiling would be a soft pedal.

[swartzentruber]

Wish I saw this thread content last year. I had that experience of going out on OEM pressures with PSS tires and ending up at ~50psi, so yeah that does happen (my driving level I would rate as lower level advanced).

Keep an eye on your sidewalls, though, assuming you aren't running with camber plates. My fronts started chunking after just a few events; one reason I'm switching to dedicated track tires this year.

This might be obvious, but when you are checking tire pressures as you adjust to a proper hot pressure, make sure you check all 4, and not just 1 or 2 and assume all 4 will be the same. I run Road America a lot, and I think I had to run my right front 1-2 psi lower than the front left (cold pressure), due to the Carousel I would assume.

[M3 Number 86]

Originally Posted by dogbone

The bottom line is we care about your safety! Sorry if we seem a little harsh.

I never tracked a PSS so I can't give you specific numbers. But 5-7 psi down sounds like a reasonable place to start. Remember though, that when you start lower like this, the car can feel mushy initially on the first lap. So, give it a lap of cautious and building speed to warm them up.

PSS doesn't really need a "warm up" lap like race tires as far as grip. They grip right from the start. But, what happens if you leave OEM psi's in there is that, as they heat up, the psi's really increase. And the tires get over-inflated and then don't grip properly in the middle of the session because they're too hard. So the whole thing is a balancing act. You don't care if the car feels mushy on the warm up lap, so go out with them softer, and then as you drive, they'll heat up and increase pressure and psi's will enter a sweet spot that's good for performance in the middle of the session. That's when you want the psi's to be correct.

Anyway, it takes experimentation, and it's affected by how hard you drive, how fast the track is, how warm it is outside. All of us are reducing pressures even further as a day warms up. So there's really no fixed number that you just stick to all the time. These things work in ranges.

Don't be like PERPLEDERPLE

[chamba002]

I don't have BBK but I can tell you what brake fade feels like. The back stretch at COTA is a 140mph plus straight to a sharp 2nd gear left hander. Every 20 min session I would get brake fade after 15mins. The brakes doesn't bite as hard, the brake pedal travel is longer, its like you have to press harder to get the M3 to slow down, and your braking distance increases. You wont hit the limit of OEM brakes unless you are at fast track. With BBK I doubt you will have fade.


A lot of brake dust after a whole day at COTA...
[IMG]Cota-06 by Chamba, on Flickr[/IMG]

[admranger]

Originally Posted by chamba002

I don't have BBK but I can tell you what brake fade feels like. The back stretch at COTA is a 140mph plus straight to a sharp 2nd gear left hander. Every 20 min session I would get brake fade after 15mins. The brakes doesn't bite as hard, the brake pedal travel is longer, its like you have to press harder to get the M3 to slow down, and your braking distance increases. You wont hit the limit of OEM brakes unless you are at fast track. With BBK I doubt you will have fade.


A lot of brake dust after a whole day at COTA...

What pads are you using?

[chamba002]

Originally Posted by admranger

What pads are you using?

Akebono Carbon Ceramic pads. I chose them because less brake dust for street driving then OEM.

[admranger]

Originally Posted by chamba002

Akebono Carbon Ceramic pads. I chose them because less brake dust for street driving then OEM.

Yeah, those aren't track pads so I'm not surprised you experienced a problem... Track pads for the track. Street pads for the street.

[Ggeezer]

Originally Posted by dparm

Fair points. I'm still learning about this stuff, so for now, I've just been focusing on technique and not getting too wrapped up changing lots of variables (it's why I just leave the tires at OEM pressures). The only real reason I went with the BBK was because I needed new brakes anyway and I wanted to have plenty of "reserve capacity" for the faster tracks.

What do you suggest I do with regards to the tire pressures? Drop them by 5psi? 7psi? etc.

We all have to start somewhere, so please go easy on me. :-)

My local BMW Canada club just had its first pre-season event where we discussed tire pressures and alignment so this stuff is fresh in my head.

They recommended around 40psi hot but that we should check pressures after each session to ensure that the tires are not over-inflated.

Basically, the steps were:
- reduce tire pressure the night before event
- check cold psi morning of event
- mark the outer sidewall of each tire with chalk because you want to ensure that after each session, the chalk on the sidewall is still intact, otherwise the tires are underinflated and you are using the sidewall as grip during corners and are wearing out the outer edges when cornering
- check chalk marks at the end of each session and adjust pressures as needed
- verify cold psi morning after event to get a sense of what the cold psi should be on the morning of your event

It was an interesting discussion because I had always thought that we should be running at 3-5psi above street pressures at the track.

[dparm]

So here's a question: I've been running around on the street with the StopTech Street Performance pads for a few hundred miles. Let's say I get on track and don't like those pads.

Is it going to be a big deal with bedding all the time if I want to use track pads like the PFC08? Is there going to be any long-lasting issues caused by using those SP pads and later switching to something more aggressive?

[roastbeef]

Originally Posted by dparm

So here's a question: I've been running around on the street with the StopTech Street Performance pads for a few hundred miles. Let's say I get on track and don't like those pads.

Is it going to be a big deal with bedding all the time if I want to use track pads like the PFC08? Is there going to be any long-lasting issues caused by using those SP pads and later switching to something more aggressive?

i've never heard of any ill effects from swapping pads and multiple beddings on the same rotors. as the pad material is transferring, it may be unpleasant until they are actually "bedded" in (noise, steering wheel shimmy, slightly reduced performance) but that is about it.

[admranger]

You won't have a problem with PFC08's. BTDT w/stock pads on my E90M3.

[bigjae1976]

I wouldn't use the pads that come with the Stoptechs. They will be useless bricks once you overheat them. They aren't hard to overheat even on street tires.

Not all pads act the same when they overheat. The Stoptech Street pads will just not stop the car. If you overheat a Pagid yellow...you won't ever know the difference until you get out of the car and check your pads which are no longer there. PF01s and Stoptech race pads have acted in a similar manner which is a significantly reduced service life.

As far as Castrol SRF. I would not recommend using SRF with the intention of extending bleed intervals to a year. Part of the point of bleeding your brakes often is to keep the moisture out which will shorten the life of your brake system components.

I once ran Castrol SRF for 9 events and 12 months. It came out green, dirty and looked absolutely terrible.

[dparm]

Originally Posted by bigjae1976

I wouldn't use the pads that come with the Stoptechs. They will be useless bricks once you overheat them. They aren't hard to overheat even on street tires.

Not all pads act the same when they overheat. The Stoptech Street pads will just not stop the car. If you overheat a Pagid yellow...you won't ever know the difference until you get out of the car and check your pads which are no longer there. PF01s and Stoptech race pads have acted in a similar manner which is a significantly reduced service life.

As far as Castrol SRF. I would not recommend using SRF with the intention of extending bleed intervals to a year. Part of the point of bleeding your brakes often is to keep the moisture out which will shorten the life of your brake system components.

I once ran Castrol SRF for 9 events and 12 months. It came out green, dirty and looked absolutely terrible.

Thanks. I may try PFC08 or SR34. RS29 and DS1.11 seem to be popular too. Maybe I'll give Dave Zeckhausen a call, he's provided a lot of guidance to me over the years on disc/pad purchases.

[Richbot]

For whatever it's worth my Stoptech STreet Performance pads that shipped with my STR40 front kit have started to come back a bit and feel is improving after about 5,000 street miles since a track day where I stupidly thought they would take a couple laps at 10/10ths. Must have finally worn through the part of the pad closest to the rotor that got well and truly fried? No idea. But it's started to feel less like stepping on a block of wood sitting on top of a mud puddle

[Cloud9blue]

Originally Posted by Richbot

For whatever it's worth my Stoptech STreet Performance pads that shipped with my STR40 front kit have started to come back a bit and feel is improving after about 5,000 street miles since a track day where I stupidly thought they would take a couple laps at 10/10ths. Must have finally worn through the part of the pad closest to the rotor that got well and truly fried? No idea. But it's started to feel less like stepping on a block of wood sitting on top of a mud puddle

You probably worn through the glazed layer.

Anyway, street pads for street, track pads for track, even if you are on BBK. Hybrid pads are useless unless you like taking it easy on the track.