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Yeah, the"sermon" and "reverand" parts convey a little passion that I had not intended. Edited to add a smile. He is correct, there's a lot that a newbie needs to work on before they start tweaking the car, and the big gains at that stage start between your ears.
zcct - while track tires have to deal with higher lateral loads and generally flex more than street rubber due to the lower pressures, they are constructed differently and do not need to protect your rim from pothole damage, be able to eliminate water at the same rate as a street tire or be perfectly safe at both 40F in the wet and a scorching 100F dry environment without you having to adjust the pressures, so what the nominal "all-around all-weather all-temperature street driving" tire pressure recommendations are on the fuel filler door has little to do with what you'd run on a dry track without raised or sunk manhole covers.
At autocross events you're not going to get them anywhere near the speeds that you would at a track and thus they won't heat up nearly as much by themselves while you repeatedly exceed 140 mph, so you need to start with a much higher pressure to begin with especially on a heavier car. At a road track on the other hand, you are setting the pressures for that particular track and those particular conditions on that particular day, and the trick (especially with R-comps) is to find the sweet spot at which they give you the best grip without you rolling them over too much. If you're driving in the wet, you need to add 8-10 psi from your baseline and have the full 6/32s of tread just to eliminate the water. If you're driving on a fast, sweeping course like Mosport on a dry and sunny day, you may need to drop the pressures by an extra 4 psi from the baseline to get them at their ideal temperature and grip levels after they warm up. If you're then also going to drive on the same tires at legal speeds on public roads on the way back home (so on R-somps well below the temperatures at which they're made to work), you need to add pressure to bring them back up and drive very carefully even in the dry as R-comps have about as much grip at those temperatures as a bucket of wet eels. In other words, the recommened pressures for street tires are realy for the "jack of all trades - master of none" tires and scenario, whereas your R-comps are the most brilliant and best single-puprose tools but only perform well within a very small window, which is different for any set of specific circumstances.
Diabolis,
Thanks for the earlier feedback. Dropping cold pressures into the low 30's allowed me to run with track pressures just under 40, and I was surprised how little rollover wear there was on the edges. Grip was good and tire was still responsive. . . . and I still have enough tread left for another event this weekend!
Glad to hear you got it sorted out. Were you running the PSS or did you end up getting another set of tires?
The track (and 'track-ish') tires I've looked at don't get very warm feedback as street tires, and I only have one set of wheels, so I'm still on MPSS. If you run across someone wanting to get rid of a set of twin-spoke OEM 18's, let me know!
For what it is worth - I dropped pressures to the low 30s cold during my last track day at NCM. I still ran around 40 hot as a result and on the fronts the tread markers are gone - heck, the entire outside shoulder is gone with close to no tread left there (255/35/19 Michelin Sport Cup 2s). Left is worse than right (as expected on a clockwise track).
I could still drive them forever on the road, as the rest of the tire still has plenty of tread left, but for the next track day I need a new set with shoulder tread or I will not make it through even one day.
I have them for a bit over a month now, maybe 1,500 miles and 1 day (5 x 25 minutes) on the track. I am getting K-Mac camber plates installed Tuesday to increase camber. Hopefully that will help equalizing the wear and make the shoulders live longer.
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
You've got to shed off more of the speed in a straight line before you turn in, roll off the brakes a litte earlier while trail-braking and then balance the car with the throttle. Despite all the wizardry from Affalterbach, there's no hiding the 4,000 lbs (most of which is over the front). And, it also depends on the track itself - it's a very good car around a longer track with fast sweeping corners, but it's still a pig on a short track with tight turns no matter how much camber you give it or what you bump up the tire pressures to. An Ariel Atom it ain't.
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
Originally Posted by zcct04
It's really painful to have to start measuring tire life in hours of track time instead of thousands of road miles. :-(
<snip>
Well, it is but it shouldn't be. Sure, it hurts when I have to buy three sets of tires a year (four including street and winter rubber ever other year), but we are indeed very fortunate that we can afford the luxury of measuring tire life in hours of track time.
You've got to shed off more of the speed in a straight line before you turn in, roll off the brakes a litte earlier while trail-braking and then balance the car with the throttle. Despite all the wizardry from Affalterbach, there's no hiding the 4,000 lbs (most of which is over the front). And, it also depends on the track itself - it's a very good car around a longer track with fast sweeping corners, but it's still a pig on a short track with tight turns no matter how much camber you give it or what you bump up the tire pressures to. An Ariel Atom it ain't.
LOL - well put, Diabolis. An Ariel Atom it ain't.
Yes, I know I tend to overdrive the car and need to become rounder, gentler. Still, more camber will directionally help (at least I hope).
we are indeed very fortunate that we can afford the luxury of measuring tire life in hours of track time.
What he said!
I don't remember who was describing how they'd had to learn a different driving style with this car, but I'm in total agreement. I've just finished my second track day inside of a week and expected the outside edge of my front tires to be shredded. Instead, I quit coming in so hot, quit diving in so deep before braking, quit using brakes and steering at the same time to scrub the speed down. Doing the majority of my braking in a straight line has given me more control and lots longer tire life.
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
Originally Posted by Wobble64
LOL - well put, Diabolis. An Ariel Atom it ain't.
Yes, I know I tend to overdrive the car and need to become rounder, gentler. Still, more camber will directionally help (at least I hope).
More camber will certainly help in the corners at the track. But, that bring up another question - what will it do to the handling and feel of the car when you're driving it on the road? It will likely tramline like crazy and you'll wear out the inside edges of the front tires in a third of the time - that's the trade-off...
I don't remember who was describing how they'd had to learn a different driving style with this car, but I'm in total agreement. I've just finished my second track day inside of a week and expected the outside edge of my front tires to be shredded. Instead, I quit coming in so hot, quit diving in so deep before braking, quit using brakes and steering at the same time to scrub the speed down. Doing the majority of my braking in a straight line has given me more control and lots longer tire life.
What did that do to your lap times? Did you keep track of that using something like Harry 's Lap Timer or similar?
For info, here is a map showing the computer simulated ideal line of a Porsche Gt3 at Mid-Ohio. You will see, there is no 'checkmark' style cornering, as needed for a heavier car with lots of front weight. Instead, the fastest line is holding it in tight. So I expect doing what you describe above is costing time, and significantly so.
More camber will certainly help in the corners at the track. But, that bring up another question - what will it do to the handling and feel of the car when you're driving it on the road? It will likely tramline like crazy and you'll wear out the inside edges of the front tires in a third of the time - that's the trade-off...
I don't think the tramlining should be an issue, as I will get a full race alignment to go with it. The K-mac kit also enables to dial in more caster if needed. And toe will obviously get adjusted.
That said, yes, inner edge wear vs outer edge wear will be a compromise and which side will go first will depend on the ratio of street driving vs. track.
The K-Mac kit will not give an outlandish angle. Maybe 3 degrees. I will find out and can adjust as needed.
What did that do to your lap times? Did you keep track of that using something like Harry 's Lap Timer or similar?
I've not been back out on the same course since I began making the shift in driving style so I don't have a good way to compare times. More relevant is that I was so bad when I started, lap times had nowhere to go but down. Gut feel is that separating the braking from the turning allows greater speed through the turn because the tire only needs to generate turning forces, not both turning and braking. It also gives greater control through the apex which allows acceleration to begin sooner, and I feel like I'm seeing higher exit speeds. I'm not yet a good judge, but I think it's faster.
I started using RaceChrono a couple events back. It's pretty easy to set up and gives you very visible lap times on-course, but finding things after the session is not at all intuitive. Have you been happy with Harry's?
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
You can try Track Addict - http://racerender.com/TrackAddict/Features.html. Even the free version will allow you to record in 720p from your smartphone, and I find the GPS is very accurate (well within a 10th of a second).
I am sure there are alternatives, but Harry's Laptimer is pretty amazing. It has 700+ tracks included, and does video with data overlay from the phone (g-forces, speed, GPS position and position on track)as well as OBD data overlay like rpm, gear and throttle position, if you have an OBD dongle. It also can remote control several additional camera, e.g. goPros, via WiFi.
Does way more than I can leverage.
You can also add an external high accuracy/high speed GPS via Bluetooth, if you want.
I devoured another set of MPSS over the last 3 or 4 track days, and I'm puzzled about the failure mode. The rears were worn pretty evenly with a bit more rubber depth outside than inside. About 10 laps into my third session I started noticing more oversteer and pitted to find chunks peeling off the outer shoulder and tread surface (see below).
This is the second time I've had an MPSS do this. Any ideas about what might be causing it?
I'm running stock alignment. Weather was mild (70F). I did a gentle warmup lap, pressures were about 40 once the tires got warmed up.
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
Yup - you chunked them. That happens when the surface of the tire is hot enough to grip, but the rest of the tire (the carcass) is still too cold and the rubber is brittle instead of being soft and elastic throughout, and it breaks off. You need a longer warm-up time - say, another 3 or 4 laps - before you start to push hard. That's all. I gather ambient temps were lower - not 35C...
regarding the track tire part of this thread, at 2 events at Road America this year, a couple of the GTR guys, another heavier car like our C63, did not care for their Toyo R888 tires at all, same or slower lap times than their previous tires, including stock run flats and all seasons.....
So after riding with and working on cars with these guys, it somewhat eliminated that tire from consideration for me. And they ran the 2nd and 3rd fastest lap times of the weekend out of approx 70cars. So any of the C63 crowd here have experience with the Nitto NT01 tires for track?
At this point, I'm not wanting to go Hoosier R6, etc, as I still want gradual break away communication while I learn this particular car in that environment.
I'll start by pointing out that I don't have a C63 .... unfortunately. The best air pressure depends on many factors. If all the bushings are stock you'll find it difficult to get even tire wear no matter what you do. I always ran with high-ish air pressure with stock bushings but it didn't help much because the bushings deform and allow lots of camber change. Accept that the track will eat your tires and play with pressures. My car was best starting at 32.5 psi front and 34 rear. Hot pressures ended up at 39 to 40. This applies to Kumho XS, Yokohama AD08, Hankook RS3, Hankook Z214 and Hoosier R6. If you have poly bushings and camber adjustment available you can lower the air pressures to 26 psi cold with Hoosiers or Z214's. The track surface will come into play as well. Old and slick or new and sticky for example. The local noise on the R888's is that they don't like heat or weight. Better on light cars and cool days. I really liked the Yokos but they will give up some grip when they get real hot. The Kumho's and Hankooks (RS-3) are similar and good. I've heard good things about the Dunlops but have no experience with them. If I was going back to a dual purpose tire I'd use the Yokos. I'm using Hoosiers currently because it's the only tire I know I can get when I need them. The others have real supply problems, at least in my sizes, and are frequently on back order.
W204 C63 Coupe, W166 ML350 BlueTEC, 928GT, C5 Z06 & IS300 race cars, EQE 4Matic+ on order
All other things being equal - if anyone on any car experiences slower lap times on any R-comp tire than their OEM run-flats or all-seasons, I'd say they are doing something *VERY* wrong - unless the temperature is below the freezing mark or there's snow on the ground. "A couple of the GTR guys..." pretty much sums it up.
Are the R888s the best R-comps out there? Certainy not. In terms of sizing and load capacity however, they are pretty much the only choice for a C63 though (I tried the Trofeo Rs and killed the sidewall in two sessions) so I am afraid they are the only sensible choice - but I'm all ears if you have a better suggestion). Are they stickier than "street-grade" tires? Around Mosport they're easily worth 4 seconds a lap over (wider) PSS if you get the pressures right. Unless you have a GTR, apparently.
E55K, Black on Black. C63, Black on Black. SRT-10 NightRunner 363of400
Somebody earlier was asking about the NT01's. I like them and have been using them relatively exclusively all summer. I've run bunches of R888's and PSS as well and here are my thoughts. There is a lot of evidence out there that the PSS are probably one of the best street tires available for these cars. Good cold traction, great wet capabilities and they are whisper quiet. However you get them on the track and they come unglued. They get greasy quick and they squeal like school girls at a Bieber concert. If they survive a hard day at the track they turn into these stale hard donuts that aren't worth anything the next time you try to heat cycle them. Keep them on the street. Period.
I like the R888's a lot. They are great on the track. Sticky, predictable and they seem to last a fair amount. However, they have their draw backs. On the road they buzz and humm like crazy. Also, they are directional. So you can't just swap the fronts side to side for multiple day track events. They have to be taken off the rims and swapped and then mounted back on the rims. Not ideal. However, their wet traction is much better than the NT01's.
That being said, you run the NTs for a good session or two and there is two continuous grooves in them and that's it. Slicks. I get more life out of them than the 888's hands down. They aren't as loud as the 888's and they get sticky relatively quickly without getting prematurely greasy. You get a little water on the pavement though and you might as well have on ice skates. The weight rating for them is not quite enough for these cars but I've never had a problem, knock on wood.
I know guys like Wobble prefer data over opinion, but my experience with them is nearly as good!! Especially seeing as I'm beating on them at the track a couple of times a month!
07-23-2015, 05:01 PM
