Hoosier Tire Wear on Outside Edge at the Glen
 

Hi,

Wondering if I can get some input on some tire wear issues I experienced at the glen. Great weekend overall but my outside tire wear is much greater than the inside which is baffling me since I ran a decent bit of camber. Setup listed below as well to give info.

Car: 1999 NB1 Mazda Miata
Tires: Hoosier SM7 / 205/50-15
Wheels: 949 6UL 15x9
Tire Pressures (hot): 38 front / 36 rear
Mods: Coilovers, RB sway bars, derlin & poly bushings on the whole thing, Wilwood little BBK w/ gloc R12 front & gloc R8 rear... no power adders or engine mods (yet) :party:
Camber: -3.4 front / -2.2 rear
Lap time: 2:31 (pretty consistently getting this outside of heavy traffic laps)

https://cimg5.ibsrv.net/gimg/www.mia...e50742b882.jpg
https://cimg8.ibsrv.net/gimg/www.mia...b553271e72.jpg

Thanks,

Chris

Car weight?
Spring rate?
Pyrometer temps?
In car video?

Car weight?
Stock is like 2,400 and I added some things like the little bbk, rollbar, chassis stiffening components, etc. So I'd venture to guess it's around 2,600 with a that junk and fuel and me.

Spring rate?
10kg front / 8kg rear

Pyrometer temps?
I don't currently have one.

In car video?

Heavy car, (really)soft springs, sticky tires.

You need more camber.

Gotcha. That's a good call out. Do you recommend something specific or just go with the typical race alignment from 949 to start?

Looks like 949 is recommending spring rates at 1,000 lb/in / 500 lb/in so I'm way off there as well since mine translate to 550 lb/in / 450 lb/in. I'd venture to guess if I toss that much spring at the BC coilovers I have, they are going to be too much spring for the shock so I'll need to upgrade there as well. lol, guessing this is going to really suck on the street if I run that spring rate but that seems like a reasonable trade off since my goal is to do better on the track.

So for the springs... should I bother upgrading the springs on BC coilovers (they came on the car when I bought it) or just cut bait and go to Ohlins or Xidas or something along those lines? Scope would be that I do drive it on the street but I do HPDE events with it so I am willing to sacrifice a lot of street-ability for track use as long as I retain A/C :-D

SuperMiata Race Alignment (reference provided by 949 Racing):
4.25"~ 4.75" front pinch weld height.
Zero rake with driver and fuel
Front camber: -3.2° ~ 4.2° depending on pyrometer readings
Caster: ~ 4.0° or max available once you reach camber targets
Front total toe: 0
Rear camber : -2.8°
Rear total toe: +1/16 for <200whp

On the XIDAs you'll be surprised how decent the street ride quality is on 1000 lb spring rates. It's no cadillac, can't be with those rates... but I'd wager you may actually not give up anything in ride quality compared to the BCs you're on now with half the spring rate.

BC Coils are OK for street driving, but the dampers are not worth a shit on the track, bite the bullet and buy Xida's, they are well worth the cost.

Moved a buddy's car on XIDAs through an extremely bumpy and uneven service road and it was far better than my car on Koni Sports/600-400lbs setup lol. Would have no hesitation street driving it.

On another note, I'd probably try going for a more slippery tyre in all honesty, something like RS4, or at most a NT01/RC1 if you really want a track-only setup.

560lb front on a 205 SM7 means the car is rolling over onto the outside edge of the tire. I doubt you could run enough camber to combat the issue. You need a lot more front roll stiffness.

Also, 38psi is likely way too high for a 205 Hoosier on a 9, but ask your local pyrometer for the most up to date advice

Thanks for the heads up guys. Sounds like I should stop screwing around and go with Xidas. Good to hear they aren't going to be horrible on the street at the higher spring rate... that's ideal since I do street drive it a bunch. I love track days but if I don't have to make my passenger suffer as much, that's a win. I can get beefier springs for the BC coilovers but I'm concerned that I will overspring the setup so the writing is on the wall there for that setup I guess.

@Leveq I do run RS4s on the street currently. They work great as a street tire. I started tracking on them too be fore I moved up to Hoosiers. I moved right to those b/c it's a known quanity since I used to run those on my RX-7 before I joined team Miata.

@Savington for running more camber, I think I can get more out of it. I have Bauer ELBJ's on the car as well. And I'm at nearly the minimum amount of camber now with those and the ride height and such. So I can dial that up a bit. I currently only have a surface temp infrared) gauge so I'll need to upgrade that to get readings off the tire and go from there. I'll add that to the list b/c it's been on my short list for a really long time anyway. I had good success running 38 psi hot when I ran at NJMP without all the excessive outside wear but I think a part of it was that I wasn't pushing it hard enough. But you raise a good point and I need to re-do my alignment anyway to get more camber out of it so I will need to evaluate. Do you have any suggestions for the pressure? I tried lower and I was able to get better lap times w/ the higher pressure so that's why I went there.

I suggest you buy a pyrometer :party: That pressure may be correct but you don't know for sure until you measure the temps. 3.4deg should be in the ballpark for proper front camber on that combo, assuming you have something approaching correct spring rates, so I would do that first (springs) and then re-evaluate.

lol, fair enough. Already have one in my Amazon cart so I'll get that knocked out.

OP,

You are a long way from set up properly. As Dan and Andrew mentioned, step #1 is a pyrometer.
As a guess (not 100% set in stone): Assuming roughly 2650# with a full tank, I'd start with 1000/500 springs, 54103 (1.125" x .125 wall) FSB, 14mm rear. Make sure it's not bottoming, which your BC's at the heavy compressions of the Glen, probably are.
Start at around 25psi cold. Let tires come up to temp then bleed down if needed according to pyrometer.
-3.4° probably close. Certainly not far enough off to destroy shoulders like your pics.
You will need more spring rate as you lower the car. If BC's are bottoming, consider raising it a bit.
Pretty sure the BC's will run out of low speed rebound damping at those rates, if they have't already.

Ok good deal. I'll start down that journey.

Order placed for some Xidas :-D

[QUOTE=GotBoost;1543475]Car weight?
Stock is like 2,400 and I added some things like the little bbk, rollbar, chassis stiffening components, etc. So I'd venture to guess it's around 2,600 with a that junk and fuel and me.

Sounds like more then 2600 to me

lol, could be. Pulled some stuff off the car too so lost some weight there. I've gotta weigh the car when I corner balance it and that's up next once I get the car back on the ground.