Why not more camber?
09-21-2018, 04:15 PM
#11
30f 28r is a very common pressure for RE71Rs on STR prepped cars. I actually run 28f and 28r and get no shoulder wear with about -3.5 or so in the front. On my ES Miata, I was also running similarly low pressures on the Bridgestones. The sidewall on these tires is incredibly stiff. I tend to forget to add pressure after autocross events so I'm frequently ~22psi on the street and you'd never know.
09-21-2018, 09:14 PM
#12
If the issue is racetrack performance, what counts is the performance in the turns, under braking, and on traction limited acceleration (all braking and turning are traction limited). The tire temps in the pits is a surrogate, but taking the residual carcass temp. This has been used for over 50 years and is a good proxy.
However, it is now possible to get dynamic tire surface temps throughout the lap. That is really more relevant since the tread temp, not the carcass affects traction. That way settings can be optimized for the turns that count most. Speed and lat/lng acceleration can be used as a proxy, but it often too coarse a measurement for fine-tuning.
One story related by a credible source (his car won the first SCCA Spec Miata Runoffs National Championship) said the limit on camber came when it adversely affected braking. On the track, the outside shoulder is usually part that wears first. Whether wear or performance is more important depends on the driver's/owner's objectives and budget. A look at F1 cars shows fairly extreme front camber. Hoosier recommends -4° for Spec Racer Ford.
Other than having a bit more split front/rear they seem in the middle of what most appear to be running. The shocks are better than most (although not my first choice). The Karcepts bars are works of art, a bit stiffer than most here seem to be running on the track. If Brian said that was a good package for your application it undoubtedly is. He combines keen knowledge, extensive experience, and is very smart.
However, it is now possible to get dynamic tire surface temps throughout the lap. That is really more relevant since the tread temp, not the carcass affects traction. That way settings can be optimized for the turns that count most. Speed and lat/lng acceleration can be used as a proxy, but it often too coarse a measurement for fine-tuning.
One story related by a credible source (his car won the first SCCA Spec Miata Runoffs National Championship) said the limit on camber came when it adversely affected braking. On the track, the outside shoulder is usually part that wears first. Whether wear or performance is more important depends on the driver's/owner's objectives and budget. A look at F1 cars shows fairly extreme front camber. Hoosier recommends -4° for Spec Racer Ford.
Other than having a bit more split front/rear they seem in the middle of what most appear to be running. The shocks are better than most (although not my first choice). The Karcepts bars are works of art, a bit stiffer than most here seem to be running on the track. If Brian said that was a good package for your application it undoubtedly is. He combines keen knowledge, extensive experience, and is very smart.
09-21-2018, 09:45 PM
#13
Yeah, the setup has been really good. The primary goal has been to maximize performance in STR, and that's what Brian's suggestions were based on—and they've been spot on. I've been doing a lot of track days as well though, and that's where most of my tire wear is coming from. The car is still really good, especially given the lack of aero, but as I mentioned the tire temps and wear just don't seem as good as they could be. It's possible the -3.5, -2.5 I have now is optimal for autocross, but a bit more would be ideal for track—where there is a higher ratio of cornering to braking time, I think. (You get a lot of sweeping corners on the track, whereas autocross has some of those, but a lot more transitions and quick stabs of the brakes.)
I haven't yet looked at temperatures during an autocross, so I'm planning to do that next before making changes. Assuming it shows the same higher on the outside pattern as I've seen at the track, I'll plan on adding a bit more camber. If it doesn't, we'll see. Might try it anyway and see if I can get a bit better wear without sacrificing performance.
Do you have any specific recommendations for real-time tire temp monitoring? If it's something wireless that I could just add for a track day and then remove, and not too expensive, I might give it a try. Somehow I expect cheap, convenient, and effective is likely too much to ask though...
I haven't yet looked at temperatures during an autocross, so I'm planning to do that next before making changes. Assuming it shows the same higher on the outside pattern as I've seen at the track, I'll plan on adding a bit more camber. If it doesn't, we'll see. Might try it anyway and see if I can get a bit better wear without sacrificing performance.
Do you have any specific recommendations for real-time tire temp monitoring? If it's something wireless that I could just add for a track day and then remove, and not too expensive, I might give it a try. Somehow I expect cheap, convenient, and effective is likely too much to ask though...
09-21-2018, 10:18 PM
#14
Data logging can get expensive.
Izze Racing would be my choice for sensors, you will still need a logger. Tire Infrared Temperature Sensors. Caleb is another very smart and clever fellow...and he has an S2000.
Izze Racing would be my choice for sensors, you will still need a logger. Tire Infrared Temperature Sensors. Caleb is another very smart and clever fellow...and he has an S2000.
09-21-2018, 10:53 PM
#15
Definitely more involved than I want to get, but the video on that page was interesting!
(Especially the real-time data starting at 1:00.)
(Especially the real-time data starting at 1:00.)
09-28-2018, 01:42 PM
#16
^ I think that also shows how much a corner balance could help as well. The rear left is obviously getting much hotter than the rest of the tires. I want to get my car balanced because I bought coils and they were WAY more difficult to get even than I thought. It's just one more variable in the voodoo magic suspension equation.
10-20-2018, 09:35 PM
#17
do you still have the oe bushings?
had a similar issue on a str car i codrove. the only difference between this car and the other two other str cars i codrove where this wasnt an issue was they had polybushes throughout
all three cars had more than neg three in front
car 1 04 with outer tire wear issue had comptech bar with motons 750lb front springs
car 2 08 cr no wear issue had gendron bar w penskes and 750lb front springs and poly bushes
car 3 04 no wear issue had karcepts bar w jrz and 750lb front springs and poly bushes
maybe a red herring but something to consider
i felt car 1 although quick was a little inconsistent at the limit.
good luck
had a similar issue on a str car i codrove. the only difference between this car and the other two other str cars i codrove where this wasnt an issue was they had polybushes throughout
all three cars had more than neg three in front
car 1 04 with outer tire wear issue had comptech bar with motons 750lb front springs
car 2 08 cr no wear issue had gendron bar w penskes and 750lb front springs and poly bushes
car 3 04 no wear issue had karcepts bar w jrz and 750lb front springs and poly bushes
maybe a red herring but something to consider
i felt car 1 although quick was a little inconsistent at the limit.
good luck
10-20-2018, 09:52 PM
#18
do you still have the oe bushings?
had a similar issue on a str car i codrove. the only difference between this car and the other two other str cars i codrove where this wasnt an issue was they had polybushes throughout
all three cars had more than neg three in front
car 1 04 with outer tire wear issue had comptech bar with motons 750lb front springs
car 2 08 cr no wear issue had gendron bar w penskes and 750lb front springs and poly bushes
car 3 04 no wear issue had karcepts bar w jrz and 750lb front springs and poly bushes
maybe a red herring but something to consider
i felt car 1 although quick was a little inconsistent at the limit.
good luck
had a similar issue on a str car i codrove. the only difference between this car and the other two other str cars i codrove where this wasnt an issue was they had polybushes throughout
all three cars had more than neg three in front
car 1 04 with outer tire wear issue had comptech bar with motons 750lb front springs
car 2 08 cr no wear issue had gendron bar w penskes and 750lb front springs and poly bushes
car 3 04 no wear issue had karcepts bar w jrz and 750lb front springs and poly bushes
maybe a red herring but something to consider
i felt car 1 although quick was a little inconsistent at the limit.
good luck
When you say two of the cars had no wear issues, what does that mean exactly? Like, you know the middle tread strip on the RE-71R? I've never seen a car where that doesn't wear at an angle. Was that still the case on those cars, or did it actually wear flat?
10-20-2018, 09:59 PM
#19
That is interesting. You don't know their exact front cambers? I am on the OE bushings. (And will probably remain that way for now; really not into the cost nor hassle of installing and then maintaining poly bushes...
When you say two of the cars had no wear issues, what does that mean exactly? Like, you know the middle tread strip on the RE-71R? I've never seen a car where that doesn't wear at an angle. Was that still the case on those cars, or did it actually wear flat?
When you say two of the cars had no wear issues, what does that mean exactly? Like, you know the middle tread strip on the RE-71R? I've never seen a car where that doesn't wear at an angle. Was that still the case on those cars, or did it actually wear flat?
the middle band is always worn on the re71
the cars varied from 3.0-3.3 negative
10-20-2018, 10:23 PM
#20
OK, but there was no difference in wear between inner and outer shoulders? Many people, even in STR, write about flipping their REs to maximize wear, so it must be fairly common for the outside shoulder to wear faster. Those cars had none of that? (And they were driven competitively I assume?)