Limerock with BFG R1s in the dry = not so Fail!

[8INTO3=M]

Consider the SRF and the SS lines. I find them helpful -- and fairly cost effective. Sounds like a great day at the track!

BTW, I thought your write up was quite lucid!

[lucid]

Originally Posted by 03SG///M3

Sounds like you had a great time. I look forward to getting to LRP this season after i take delivery of my E90 (I just ordered yesterday). Sounds like some good times considering your car is mostly stock. I was running around 2 minutes flat in my E46 (it had a lot of suspension work + rcomps)

I take it that you mean 1 minute flat, or 1:02?

Originally Posted by 03SG///M3

As for the seats, I completely agree with you - Not enough support. With my E46 M3 I just had to replace the seats with Recaros. I might have to do the same with the E90. There is way too much movement when pushing the car on the track. I really wish the M3 came equiped with Recaro's from the factory.

Couldn't agree more. Better/lighter seats could at least come as an option. I would have paid for them. I looked into Pole Positions, and they didn't fit me (shoulder harness opening too low). I tried the SPGs, and they fit me really well.

[lucid]

Originally Posted by 8INTO3=M

Consider the SRF and the SS lines.

Yes, I'll go for these before doing anything else...

[Ryan239]

Spending money on the lines is not going to help so save the cash for another set of pads or fluid. If you had a mushy pedal all the time, then yeah maybe your rubber lines are flexing and causing poor pedal feel, but that's not what you described.

"It's not as if I had a serious problem stopping the car or anything, but in the last session, the pedal feel was not good at all, and I "felt" like I had to plant it lower. I also "felt" my braking distance was reduced. After the last session in the paddock, I measured front brake rotor temp of 460C (280C in the rear). So, the rotor probably had a little over 5 minutes to cool down a bit. The CoF vs temp data for RS19s indicate that CoF starts to drop right around 500C. Also, the 4 sessions were only 40 minutes apart from each other, and there probably was some residual temp at the beginning of the 4th session. The numbers indicate that I might have indeed experienced real brake fade toward the end of the 4th session. I don't know about why I felt like the pedal dropped though. I do have proper fluid in there, and Turner told me steel lines would not make a difference, so I didn't mess with the lines."

Brake fade is a generic term but there are really two things that typically occur to cause this.

If your pedal travel and feel changed, you boiled the fluid and got fade from the fluid boiling. SRF will help fix the symptom, but I still think you are braking too much as the cause

If your pedal travel didn't change, but you were braking less when you applied the brakes, than your pads were fading (that's the issue I had at the Glen). In that case, upgrading your pads will again help to address the symptom, but the root cause is not being addressed.

It's your money, so spend it as you wish, but I am betting if you drive the same, even with upgraded fluid and pads the net result will be the same, all you will do is perhaps delay the onset of symptoms. I went through this entire routine when I was running my STI, so I know exactly what you're going through.

BTW, what's a ballpark for the annual track insurance cost if you don't mind sharing? Does your regular insurance company mind the track usage? I tried to get plates and insurance on my race car so I could drive it to the alignment shop, but my regular insurance company refused to insure the car on the street because I take it to the race track... those bastids! I probably shouldn't have mentioned that it was a race car, but the lady was just asking me why I had the car for 3 years and hadn't ever bothered to register it, and I was honest.

[swamp2]

Originally Posted by lucid

Yes, thermal capacity is the key variable here together with pad compound. We haven't exactly seen detailed weight data on rotors of aftermarket kits, but what has been posted so far seems to indicate that rotor weights are not significantly different. However, I am wondering if that is because the aftermarket hats are lighter than stock, and the rotors actually weigh more than stock. Are the stock hats steel? How much do they weigh?

OEM hats are aluminum. There is no way to measure hat weight vs. cast iron part. They are formed together with the pins that allow the float. Heavier cast iron parts would indeed be a benefit.

Originally Posted by lucid

The other reason for thinking about aftermarket rotors would be material characteristics. I haven't done any research in this area, but one would think the better systems would be more durable than the stock rotors when used with more aggresive pads.

Certainly all cast iron is not created equal and I suspect you are right here.

Originally Posted by lucid

I've thought of cooling ducts as well. I might have something to report on that front later this summer. A friend of mine does CFD for a living. He's run simulations for Nascar teams. We are thinking about a redesigned bumper that does cooling and more...

Now that is exciting.

[Dascamel]

+1

on the bumper for more cooling!

[lucid]

Originally Posted by Ryan239

Spending money on the lines is not going to help so save the cash for another set of pads or fluid. If you had a mushy pedal all the time, then yeah maybe your rubber lines are flexing and causing poor pedal feel, but that's not what you described.

"It's not as if I had a serious problem stopping the car or anything, but in the last session, the pedal feel was not good at all, and I "felt" like I had to plant it lower. I also "felt" my braking distance was reduced. After the last session in the paddock, I measured front brake rotor temp of 460C (280C in the rear). So, the rotor probably had a little over 5 minutes to cool down a bit. The CoF vs temp data for RS19s indicate that CoF starts to drop right around 500C. Also, the 4 sessions were only 40 minutes apart from each other, and there probably was some residual temp at the beginning of the 4th session. The numbers indicate that I might have indeed experienced real brake fade toward the end of the 4th session. I don't know about why I felt like the pedal dropped though. I do have proper fluid in there, and Turner told me steel lines would not make a difference, so I didn't mess with the lines."

Brake fade is a generic term but there are really two things that typically occur to cause this.

If your pedal travel and feel changed, you boiled the fluid and got fade from the fluid boiling. SRF will help fix the symptom, but I still think you are braking too much as the cause

If your pedal travel didn't change, but you were braking less when you applied the brakes, than your pads were fading (that's the issue I had at the Glen). In that case, upgrading your pads will again help to address the symptom, but the root cause is not being addressed.

It's your money, so spend it as you wish, but I am betting if you drive the same, even with upgraded fluid and pads the net result will be the same, all you will do is perhaps delay the onset of symptoms. I went through this entire routine when I was running my STI, so I know exactly what you're going through.

BTW, what's a ballpark for the annual track insurance cost if you don't mind sharing? Does your regular insurance company mind the track usage? I tried to get plates and insurance on my race car so I could drive it to the alignment shop, but my regular insurance company refused to insure the car on the street because I take it to the race track... those bastids! I probably shouldn't have mentioned that it was a race car, but the lady was just asking me why I had the car for 3 years and hadn't ever bothered to register it, and I was honest.

I understand there are two separate issues here. One is simply high rotor temps. When the rotor temps exceeds the temp the pad delivers peak friction, you have fade. The other is pedal feel/travel. They are ultimately linked to the same thermal issue, but can be addressed via different means.

The high rotor temps are real. There is objective evidence to support they are at the border of running too hot for the RS-19s (unless the infrared thermometer produced faulty readings, but I doubt that). You are saying that's because I am braking early and not hard enough. I am saying that behavior--and I don't think I am exhibiting it to begin with--can't explain hot rotor temps. Technically, that is not the explanation.

However, I agree that I might be using the brakes more than I need to overall (bleeding more speed than I need to). For instance, I think that one should be able to merely tap the brakes down the hill as opposed to slowing down significantly before turning onto the straight. I am probably somewhere in the middle there. I'd buy that kind of thinking, and there is probably much for me to learn in that department.

The pedal feel/travel problem should indeed respond to better fluid than the ATE fluid I currently have in there if the fluid is boiling. There are different taks on the SS lines. I must assume the rubber lines flex more when the fluid gets hot, but I don't know how tangible that is. They don't cost that much, so I don't have much to lose there. If nothing else, they should be stronger than the rubber lines.

I have no intention of rushing to an aftermarket kit before understanding more about what's going on. I don't think it is necessary for me to spend $7k on a Performance Friction kit or anything, and I suspect upgrading from the RS19s to higher temp pads (when my current set wears out) would deal with any fade issues associated with rotor temps.

One thing to keep in mind is that it sounds like you ran 2-3 hot laps on your stock brakes with the stock tires. That puts a cap on how much heat you could have generated. I'd be interested in seeing if your thoughts change once you put some slicks and high temp/friction pads on and put in 10+ consecutive fast laps at LRP per session with limited time in between sessions--if your brakes still hold up well. This is a heavy car. The ultimate comparison would be for us to measure the rotor temps of our M3s at the same track. If you end up going faster while keeping significantly lower rotor temps, then I am clearly braking more than necessary. I have no doubt you will be faster, but I doubt that we would see a significant temperature difference (say 100C).

The annual HPDE insurance is 3.5% of the agreed value for up to 10 events, and 4% of the agreed value for 10-15 events. An event that has multiple days still count as one event. I was told they have a different product with higher rates for people who want to do time trials and open lapping days.

I don't tell my regular insurance company anything about track driving. I told my previous insurance company, and they freaked out for no reason. I know my current regular insurance company will not cover anything on the track for sure. For me, the HPDE insurance cost is worth the peace of mind. They told me they paid out 3 GT3s last year in full...

[lucid]

Originally Posted by Dascamel

+1

on the bumper for more cooling!

I'll keep you guys posted...

[FStop7]

Not for nothing but don't forget that another way to improve braking is to add lightness.

[Ryan239]

Originally Posted by lucid

For instance, I think that one should be able to merely tap the brakes down the hill as opposed to slowing down significantly before turning onto the straight. I am probably somewhere in the middle there. I'd buy that kind of thinking, and there is probably much for me to learn in that department.

The pedal feel/travel problem should indeed respond to better fluid than the ATE fluid I currently have in there if the fluid is boiling. There are different taks on the SS lines. I must assume the rubber lines flex more when the fluid gets hot, but I don't know how tangible that is. They don't cost that much, so I don't have much to lose there. If nothing else, they should be stronger than the rubber lines.

I have no intention of rushing to an aftermarket kit before understanding more about what's going on. I don't think it is necessary for me to spend $7k on a Performance Friction kit or anything, and I suspect upgrading from the RS19s to higher temp pads (when my current set wears out) would deal with any fade issues associated with rotor temps.

One thing to keep in mind is that it sounds like you ran 2-3 hot laps on your stock brakes with the stock tires. That puts a cap on how much heat you could have generated. I'd be interested in seeing if your thoughts change once you put some slicks and high temp/friction pads on and put in 10+ consecutive fast laps at LRP per session with limited time in between sessions--if your brakes still hold up well. This is a heavy car. The ultimate comparison would be for us to measure the rotor temps of our M3s at the same track. If you end up going faster while keeping significantly lower rotor temps, then I am clearly braking more than necessary. I have no doubt you will be faster, but I doubt that we would see a significant temperature difference (say 100C).

The annual HPDE insurance is 3.5% of the agreed value for up to 10 events, and 4% of the agreed value for 10-15 events. An event that has multiple days still count as one event. I was told they have a different product with higher rates for people who want to do time trials and open lapping days.

I don't tell my regular insurance company anything about track driving. I told my previous insurance company, and they freaked out for no reason. I know my current regular insurance company will not cover anything on the track for sure. For me, the HPDE insurance cost is worth the peace of mind. They told me they paid out 3 GT3s last year in full...

Wait, you're braking for the downhill? That's part of the problem right there! That should be a lift at best. It's a puckering change, but I picked up half a second a lap or so just by changing from a tap on the brakes to a lift last time I was there, since you wind up carrying a couple more mph into the straight.

I was running more than 2-3 hot laps during my practice sessions but the pad fade would set in after a couple laps if I had light traffic and good speed into the bus stop. I was out for 20-30 minutes at a time and the pad fade was manageable, as I mentioned, but taking it easy for a few turns. I don't plan on race rubber for this car, nor do I plan on race pads, since I have a dedicated race car with those bits already purchased. I also don't care about wadding up the race car nearly as much as I care about wadding up the M.

The insurance cost seems fairly reasonable, so I am assuming about $2k depending on what you settle on for a replacement value. If you run a lot of events that is cheaper than the one I linked above. Of course, that is also a season's worth of race rubber, fuel, brake pads and tow vehicle fuel cost for my race car heheh, but it's a nice piece of mind nonetheless.

[lucid]

Originally Posted by Ryan239

Wait, you're braking for the downhill? That's part of the problem right there! That should be a lift at best. It's a puckering change, but I picked up half a second a lap or so just by changing from a tap on the brakes to a lift last time I was there, since you wind up carrying a couple more mph into the straight.

Yeah, I've been working on that. I think I got it down to more of a tap, but I'm sure there is more to be gained there. That was kind of annoying in my run group; pretty much everyone was really braking there. However, I don't know that you can just get away with a lift with this car if you build up speed up to that point. If you take your car to LRP, I'd be interested in learning what you can get away with on a stock E92 M3. But the thing is the extra momentum you can maintain there will eventually be turned into heat when you brake down the straight anyway, so I don't know that it makes a huge difference in the end in terms of rotor temps.

Originally Posted by Ryan239

The insurance cost seems fairly reasonable, so I am assuming about $2k depending on what you settle on for a replacement value. If you run a lot of events that is cheaper than the one I linked above. Of course, that is also a season's worth of race rubber, fuel, brake pads and tow vehicle fuel cost for my race car heheh, but it's a nice piece of mind nonetheless.

Yep, it is a good deal if you know you will put in a good amount of track time. If I had space for a trailer, truck and a second car, I'd go for a dedicated car as well.

Do you instruct with any other club than COM? Maybe I can pick up a few things from you that way...

[03SG///M3]

Originally Posted by lucid

I take it that you mean 1 minute flat, or 1:02?



Couldn't agree more. Better/lighter seats could at least come as an option. I would have paid for them. I looked into Pole Positions, and they didn't fit me (shoulder harness opening too low). I tried the SPGs, and they fit me really well.

Yes I meant 1 minute flat. Not sure why I wrote 2 min. SPG's are very nice. That's the seat I am considering for my E90.

[lucid]

Originally Posted by 03SG///M3

Yes I meant 1 minute flat. Not sure why I wrote 2 min. SPG's are very nice. That's the seat I am considering for my E90.

What are your thoughts on a harness bar?

I'd like to have a roll-bar installed, but I don't have much confidence in a bolt-in solution, and don't want to weld plates in.

One option for a harness bar is to use the stock seatbelt mounting holes on the pillars. I was at HMS the other day, and they showed some pics of such a bar that was done for a Porsche.

[03SG///M3]

Originally Posted by lucid

What are your thoughts on a harness bar?

I'd like to have a roll-bar installed, but I don't have much confidence in a bolt-in solution, and don't want to weld plates in.

One option for a harness bar is to use the stock seatbelt mounting holes on the pillars. I was at HMS the other day, and they showed some pics of such a bar that was done for a Porsche.

A harness bar is nice although not the safest solution which worries me. I was in the same situation with my E46 which was that I wanted a roll bar but I also wanted to retain the ability to have it street driven - welding in a roll bar pretty much makes it unsafe to drive on the street. I've seen numerous harness bars on P cars too. I guess i would consider one for the M3 if it was able to be extremely cleanly installed and was able to be removed with out much modification even though its not the safest solution (I really don't like moving around a lot in the car while driving). For me as I'm getting an E90, it would eliminate the use of the rear seats. I might try getting a Recaro SPG and a CG lock before I went ahead and installed a harness bar.

[lucid]

Originally Posted by 03SG///M3

I might try getting a Recaro SPG and a CG lock before I went ahead and installed a harness bar.

Wouldn't this result in the seat supporting the vertical loads from the belts? My undestanding is that Recaros are not designed to support that kind of loading?

[03SG///M3]

Originally Posted by lucid

Wouldn't this result in the seat supporting the vertical loads from the belts? My undestanding is that Recaros are not designed to support that kind of loading?

I suppose yes if you didn't route the belts through the belt holes.

The other seat I might consider is the Recaro Sportster RS (same as the BMW performance seat although without the side airbag). This would be essentially the same as stock (reclining) but with more support and a CG lock.

[lucid]

Originally Posted by 03SG///M3

I suppose yes if you didn't route the belts through the belt holes.

The guys at HMS told me the Recaros would not be able to deal with the vertical belt loads at the belt contact points even if the belts were routed through the holes. They said the stock seats are a different story since they have extra structure. I haven't seen any evidence supporting either claim.

[03SG///M3]

Originally Posted by lucid

The guys at HMS told me the Recaros would not be able to deal with the vertical belt loads at the belt contact points even if the belts were routed through the holes. They said the stock seats are a different story since they have extra structure. I haven't seen any evidence supporting either claim.

That's interesting as I've never heard that before.

[von_zoom]

I noted your comments about pushing the rev limiter, and apparently that has been a small issue for another E92 I am aware of. I run mostly at VIR, and one of the guys who runs in my group (A) was have the same problem at VIR, being between gears often. He change gearing in the rear end, however I do not know what they changed to, but it cured his problem. At VIR you do not need as much top in, never can get there, and the changes they made helped him a lot. The change was not all that easy, took a lot more labor time than forecasted. Just a thought.
vz

[lucid]

This probably is a track specific issue. I'll be at WGI on Monday, so I'll see how things work out there. Haven't had problems with gearing at NHMS last year, but I can see this being a problem at one point there: before the hairpin (3rd gear used to just top out there, and I would most likely hit the limiter with this setup).