What have you done to your Miata today?

[psyco-joe]

that is some good information, pretty similar to the other reviews I saw. Being how they don't do well in the head and racing at willow springs in the cali desert pretty much means a hot track temps all day it would be a poor choice for me.

While I know rs-3s are fast, they tend to be good for only several laps then the grip begins to drop off quickly after that. At least that is what I hear from many of the people who run them at willow. That is one thing I liked about the 615ks, they were really consistent throughout the day but they simply don't have as much grip as those other tires.

 

[WillD]

That surprises me regarding the RS-3. They are supposedly the best in terms of high heat tolerance. My experience with them is limited to autocross though.

 

[brandini]

Sounds more like they're heat cycling out...

 

[aMaff]

The 949Racing clutch, slave cyl, bearings & clutch line came in today. Very excite

Compare to the 18lb 4oz stocker:

Install TBA

 

[WillD]

Sounds more like they're heat cycling out...

Overheating is more likely. Street tires, even the extreme performance category, are very tolerant when it comes to number of heat cycles unlike true R-compound tires.

Sweet new clutch btw aMaff!

 

[chiefmg]

Maff, are you sure you can handle so much goodness?

Tires showed up yesterday so dropped the wheels off this morning. Those Rivals look beefy.

 

[aMaff]

Maff, are you sure you can handle so much goodness?

Only one way to find out...

 

[JamesCH]

-derp double post-

 

[JamesCH]

aMaff, that is awesome *thumbs up*

Also, what WillD said about street tires. I've heard of RS3/StarSpecs and the like doing hundreds of heat cycles through autox runs without large performance losses.

Overheating an RS3 is quite challenging... perhaps driver style and/or car setup isn't playing nice with the tires.

 

[princess peach]

might be as simple as using the wrong tire pressure for his particular setup

 

[WillD]

might be as simple as using the wrong tire pressure for his particular setup

Good thought

 

[JamesCH]

might be as simple as using the wrong tire pressure for his particular setup

Indeed, very good point. After using a tire pyrometer once I have been thoroughly convinced that they are magical devices that everyone at the track should use. I can easily see the tires heating up after a few laps and becoming over-inflated.

What I did to my Miata:

A few pics of my COP conversion. Here is the aluminum plate I made to bolt the coils down to. 1.5inx0.25in. I drilled clearance holes for the coils, through-holes for the three valve cover bolts I grabbed, and tapped holes to bolt the coils down to. I swapped out the valve cover bolts for studs.

I tried a sample of both a brushed finish and engine turning. The engine turning turned out (hah!) pretty well, but I figured it would look weird with only a swirl or two showing at any given point. The sample bit is on the left, and the un-finished coil mounting bracket is on the right.

The plate, as installed, with a partly complete wiring harness and the stock coils/wires still there.

The ECU bits, I replaced two resistors that were out of spec per newer MS1 guidelines, and a transistor that had failed.

Two pictures of the final install. I can't put my strut bar in anymore, but I think I can make a new one, or modify my current one, to work.

Before:

After:

 

[aMaff]

Indeed, very good point. After using a tire pyrometer once I have been thoroughly convinced that they are magical devices that everyone at the track should use.

For radial tires, yes. For bias plys, you're almost better off guessing (well, testing at least).

 

[JamesCH]

For radial tires, yes. For bias plys, you're almost better off guessing (well, testing at least).

What makes you say that?

The tires I used a pyrometer with were Hoosier R25Bs. I saw a spike in center temperature on the front tires coupled with bad understeer, I dropped the front tire pressure from 12psi down to 9psi after a few adjustments. The understeer problem went away and the temps were right where they should be.

 

[aMaff]

What makes you say that?

The tires I used a pyrometer with were Hoosier R25Bs. I saw a spike in center temperature on the front tires coupled with bad understeer, I dropped the front tire pressure from 12psi down to 9psi after a few adjustments. The understeer problem went away and the temps were right where they should be.

During my testing, having the temperatures even across the tread is not necessarily the fastest setup on Bias tires. If you have a big spike in 1 spot then yeah, you've got a problem, but about the only way I've found (between GoodYears and Avons, and other bias ply racers I know) to really get bias plys dialed in, is test test test test.

 

[JamesCH]

During my testing, having the temperatures even across the tread is not necessarily the fastest setup on Bias tires. If you have a big spike in 1 spot then yeah, you've got a problem, but about the only way I've found (between GoodYears and Avons, and other bias ply racers I know) to really get bias plys dialed in, is test test test test.

Ah, I wasn't assuming that even across the tread was best. 949 suggests looking for 5-10deg increases in temperature from outside to middle to inside, and that sort of temperature gradient is what I shot for when setting up the R25Bs.

http://949racing.com/using-a-tire-pyrometer-949-racing.aspx

Much smartness to be had in that write-up.

 

[princess peach]

Good read, might get a pyrometer and play with settings.

 

[WillD]

That 949 article is a good one that's for sure.

For autocrossing I will direct you to Andy Hollis's Facebook page. He knows a thing or two about testing tires for autocross.
https://www.facebook.com/notes/hollis-racing/how-to-do-skid-pad-testing/417124891704816

 

[JamesCH]

Andy's procedure is basically what I was using to help my old FSAE team setup their new car with the R25Bs. We used a figure-8 skid pad per FSAE skid pad event specs. I like it a little better than a standard O skid pad, you can help make sure that the car is even in left vs right and you aren't totally screwing up the transient response without stopping and doing another drill.

 

[princess peach]

I feel edumacated