Chump/Lemons tire choices/insight/experiences

[GillesBigCowboy]

Doing first Chump race in November (twin 7r enduros), but already dreaming about fresh track rubber! .... I have no experience with any of the tires used in these races.

Of course, I am thinking about maybe the Rivals, the Z2s or the 615s in 205-50-15 (in this size, I might just choose the Z2s because of the symmetric tread which would allow flipping and longer life), but then I saw the Rivals also came in 225-45-15, and I am guessing these might work well...?

Anyway, I figured some other crapcan e30 racers might have some experiences with one or more of these Chump/Lemons legal tires. I am guessing that the differences between tires will not be really significant, but any insight would be appreciated, especially info on ideal pressures (hot or cold).

[kingston]

GillesBigCowboy,

On our E30 Chump Car racers, we ran Z2s last year. LOVE those tires! I'm going to burn through a set of Toyo R1As I have for my track car, and then put some Z2s on that as well. They seemed to warm up pretty quickly, stick like glue and wear very well.

We were shooting for 38psi hot. Started at 32psi cold.

You're going to have SOOOO much fun!

[jlevie]

Nitto NT01's

[kronus]

we've been running star specs and ZIIs when those were discontinued, but pretty much the best lemons-legal tire you can get in an e30-appropriate size is the 225/45r15 hankook rs3

[Bimmerman325i]

RS3s are being phased out soon. Rumor has it the RS4 will be out soon.

ZII are really good, Rivals are also good. Falken 615s suck, 615K aren't any less expensive than the good tires and don't perform as well in all the tests that have been done.

[gills]

Although my team doesn't run an e30 in lemons/chump (because everyone and their mother runs one ;)), we run an s13 240sx, the rivals are the best dry, warm/hot day tire, bar none. Forgiving, predictable, take a beating, and have tremendous grip at the expense of some side wall stiffness and response, but still not like rs3 squishiness.

I also have experience with falken 615k in an Alfa Romeo milano and they aren't too shabby either. Definitely less outright grip but they performed fairly well. I also got stuck on them in the rain and was surprised at how well they worked. They also wear very well.

[GillesBigCowboy]

Tires are so critical to our momentum racecars, and I love to contemplate them. I am already driving these new race rubbers in my Ross Bentley visualizations.

For me, essentially all I have driven on track has been Toyos: Ra1s, R888s, and RRs. Very nice/hot/sticky stuff, but also significantly more dollars than the 200 (or is it 180?) treadwear LemC minimum. Most of my street tires have been cheap or all season, but Bitsy did come with some 225-50-15 Khumos that I used a few times on track and road. Not sure what the treadwear was on those Khumos, but they seemed very predictable on track.

NT01s and rs3s treadwear ratings look too low to be legal, thankfully! because they were also relatively expensive.

I am definitely leaning towards the 225-45-15 Rivals based on all of my research, lurking, and this feedback (the Z2 is only available at 205-50-15). I just remember years back when GRM did a test and the results were the narrower tire being measurably faster than a wider version of the same tire, but that test was autocross, not road course in an endurance race. Could 205 be faster than 225 in a 7hr race on a twisty road course?

Overall, if size were not an issue, I would likely choose Z2 over Rival, but that wider size is enticing.

Has anyone ever compared lap times using 225-45-15s vs. 205-50-15s of the same tire?

[Wanganstyle]

we have 615k, Z1, Rs3 for our e30.

RS3 seems to be the best lap time out of the bunch, star spec seems a bit more stable when hot.

[tinkerputzer]

Has anyone ever compared lap times using 225-45-15s vs. 205-50-15s of the same tire?

Latest grm tire test at harris hill

[GillesBigCowboy]

Nice data, Tinkerputzer.
The pressures seem a little low.., Did they do one timed lap at a time, or did they do multi-lap runs?
Internet hearsay is that the ZIIs handle the heat and long runs very well.
And look at that! On the 8 inch rims, Rivals were faster in 205 than 225, but then on the retest 205 are slower...?
The rim width seems to matter, but my 7in. are paid for...

[Wanganstyle]

Nice data, Tinkerputzer.
The pressures seem a little low.., Did they do one timed lap at a time, or did they do multi-lap runs?
Internet hearsay is that the ZIIs handle the heat and long runs very well.
And look at that! On the 8 inch rims, Rivals were faster in 205 than 225, but then on the retest 205 are slower...?
The rim width seems to matter, but my 7in. are paid for...

Do you have enough RWHP to need 225mm?

Our e30 is about 180rwhp and torque and have no wheel spin with the 215mm z1 star spec.

With 154rwhp (stock m20) 215mm rt615k was more than enough corner exit traction.

In endurance racing fuel economy is pretty key................

Sent from my SAMSUNG-SGH-I337 using Tapatalk

[GillesBigCowboy]

Do you have enough RWHP to need 225mm?

Our e30 is about 180rwhp and torque and have no wheel spin with the 215mm z1 star spec.

With 154rwhp (stock m20) 215mm rt615k was more than enough corner exit traction.

In endurance racing fuel economy is pretty key................

Sent from my SAMSUNG-SGH-I337 using Tapatalk

Rwhp is probably 140s.
Adhesion limits pushed harder in corners and braking, but yes, the narrower would in theory have lower rolling resistance... but could 225s at 38.5 psi lap faster for longer than 205s at 38 psi?

225 45s have smaller diameter, which should be a gearing advantage at most tracks, maybe.
205 is the safer, majority choice, probably for good reason,... still have a few months to contemplate.

[Wanganstyle]

Rwhp is probably 140s.
Adhesion limits pushed harder in corners and braking, but yes, the narrower would in theory have lower rolling resistance... but could 225s at 38.5 psi lap faster for longer than 205s at 38 psi?

225 45s have smaller diameter, which should be a gearing advantage at most tracks, maybe.
205 is the safer, majority choice, probably for good reason,... still have a few months to contemplate.

Change your final drive and solve it the proper way (if possible). BS at lemons won't check the final.

Our 2500 lb e30 at 154rwhp did not ever overheat 205mm 615k.

Z1 was about 2 sec faster
Hankook rs about .75 sec faster than those.

Lighter narrower tires = better accel and mpg given traction not overcome. Obviously corner weight it.