Optimal Wheel size for HPDEs? Specifics inside

[phenryiv1]

So I want to establish the scenario so that I get the most applicable responses.

This is my rallycross car but I want to take it to HPDEs on a different wheel/tire/pad setup, just for fun. I might do 2-4 a year, if I am lucky. The ONLY track(s) where it will go are the various circuits at Summit Point in WV.

So the car:

• Car is running a stock M20B25. Assume that no power adders (a chip/injectors at best) will be consequential, no swaps, etc.
• 3.73 LSD
• Stripped, caged, harnessed, etc.
• With this wheel/tire setup I will be doing HPDEs only. Autocross only if I am really bored.
• Suspension is fairly basic: H&R OE Sport springs, Bilstein HDs, all new tophats, new solid & offset CABs, rear strut tower bar.
• Before the first HPDE, it will get: a urethane diff bushing, new tie rods, new stock subframe bushings, new RTABs, SS brake lines.
• Pads will be something track-specific. I had XP-8 pads on my WRX and loved them. Something in that line of performance is the goal.

What I am looking for is a recommendation on both tire and wheel specifications: size (15/16?), tread width (205, 225?) and profile? Wheel width (7/7.5/8?), offset, etc.

A lot of recommendations that I found through search are based on a specific series and the associated regulations. Because I am just doing this for fun, I don't have the limitations. I'd like something that is a good bang for the buck and that my stock M20B25 can properly utilize. I just don't see a stock B25 needing more than a 205 or a 225 width or justifying a wheel size over 15-16" but that is why I am posting up here.

My initial thoughts are maybe a 205/50/15 on a 15x7" wheel. I could be swayed to a 16" or a wider 15" if there is a benefit and if the cost is not too much more than it is for a 15x7" setup. With the SpecE30 wheels out there, it was hard to justify the idea of going larger for the wheels but 15" tires are not exactly widespread. Of course, the only tires that I need are the 1 set that works for me.

So please feel free to comment and suggest what might be the "best" setup for my situation.

Thanks!

[kts]

I'd stick with 15s for more tire options vs 16", plus the cost savings.

15x7 Team Dynamics or 15x7 or 15x8 TRM C1s are always great affordable lightweight options that look good on an E30 too.

I think 205/50R15 is plenty fine, for HDPE. I'm a little dated in my tire knowledge but the only 225 that's not an R Comp I might consider running is the Hankook RS3 but I really only know how that tire performs at an autox and not at a track day.

Kuhmo XS has worked well on my E30 and Star Specs seem to be the dominant tire at lemons events which you'll often see E30 out there. They wear well and keep sticky.

If you go with the TRM C1s I'd probably just go with the 15x8 since it's $10 more than the 15x7 version and will let you go to wider tires should you decide to try something wider than a 205 later on.

[Danny]

Whatever is cheap and a decent summer tire. I would to 205-50-15 due to cost.

[z31maniac]

There is also the new BFG Rival coming out in 225/45/15, it and the 205/50 are a bit short compared to the factory OD" on the car, but it's alright.

I might suggest a set of camber plates.

I'm running the Carbotech XP10 front and XP8 rear on my Miata, great great pads.

[nrubenstein]

Realistically, 205/50-15 on a 15x7 is adequate. And more to the point, it's one of the cheapest out there. Could you try to cram in more tire? Sure. 275/35-15 on a 10+" wheel might be optimal. But it won't be cheap or easy.

[Wh33lhop]

205 on a 15x7 is "enough", but why not go with 15x8 and 225s.. just a bit more. $440 for 15x8 C1s and it's like $500 for a set of Rivals or RS3s.

[phenryiv1]

This may seem like a stupid question, but can a stock M20B25 produce enough power to justify a 225? My WRX could not really overpower a good 245 on the track, but I have never tracked a RWD car so I don't quite know the dynamics.

The cost difference between a 15x8 & 225 setup and a 15x7 & 205 setup is not much, so I don't want that cost to be the deciding factor.

I just don't want the extra inch of tread (resistance), added weight, and other factors that I can't identify to be a waste or a detriment.

So far, strongly leaning toward a 15x7 with a 205/50 or a 15x8 with a 225/45.

[Earendil]

205 on a 15x7 is "enough", but why not go with 15x8 and 225s.. just a bit more. $440 for 15x8 C1s and it's like $500 for a set of Rivals or RS3s.

Perhaps because with a 15" wheel there are more 205 options than 225. And if he's not dead set on spending the cash on just choosing a single tire for the next number of years, why not go 7" and have all the options available?

I'm running 15x7 Team Dynamic wheels (not flashy, light and cheap, look good) with Dunlop ZII 205/50. This setup is perfect for my light HPDE needs. Wheels are light and didn't break the bank. Tire options are great (I was torn between 4 great tires this year) and when looking at 15" wheels the tire options are far cheaper than their 16" and 17" brothers.

[Wh33lhop]

This may seem like a stupid question, but can a stock M20B25 produce enough power to justify a 225? My WRX could not really overpower a good 245 on the track, but I have never tracked a RWD car so I don't quite know the dynamics.

The cost difference between a 15x8 & 225 setup and a 15x7 & 205 setup is not much, so I don't want that cost to be the deciding factor.

I just don't want the extra inch of tread (resistance), added weight, and other factors that I can't identify to be a waste or a detriment.

So far, strongly leaning toward a 15x7 with a 205/50 or a 15x8 with a 225/45.

Perhaps because with a 15" wheel there are more 205 options than 225. And if he's not dead set on spending the cash on just choosing a single tire for the next number of years, why not go 7" and have all the options available?

I'm running 15x7 Team Dynamic wheels (not flashy, light and cheap, look good) with Dunlop ZII 205/50. This setup is perfect for my light HPDE needs. Wheels are light and didn't break the bank. Tire options are great (I was torn between 4 great tires this year) and when looking at 15" wheels the tire options are far cheaper than their 16" and 17" brothers.

You guys are overlooking a big part here... and that is that you can easily slap a 205 on an 8 (I've done it), but you can't really run a 225 on a 7. It's ten bucks more for a 15x8 C1 than a 15x7 C1. So you are actually limiting your options by going 15x7, unless you plan on racing in a class that prohibits them. Moreover a 205 will actually be FASTER on a 15x8 as it will put down more contact patch on a mild stretch. No, I am not a stancefag, but the tire will behave better when it is slightly stretched than when it's square.

If it were me, right now, I'd get the 15x8s and 225/45 Rivals. They won't slow you down unless maybe you are on a really high speed track.. which probably isn't a good idea with an E30 anyway. And you will downright giggle at the amount of grip you will get. If for whatever reason you want a 205 later, just get a set and put it on.

[djjerme]

To "win" your run group, totally go 15". When they switch to open passing you may be able to stomp the hell out of some vette's..

[jlevie]

This may seem like a stupid question, but can a stock M20B25 produce enough power to justify a 225? My WRX could not really overpower a good 245 on the track, but I have never tracked a RWD car so I don't quite know the dynamics.

The engine power is only one aspect. Braking and cornering are usually more important and the larger contact patch of a wider tire wins.

[phenryiv1]

Liking the info so far. Thanks!

[unevolved]

I'd definitely agree with the 205/50/15 as the tire size to choose, you've got lots of cheap, good choices in that size all across the spectrum.

There are some valid points in the 15x8 vs. 15x7 argument, though. I run 15x7s, but 15x8s may not be a bad call.

[FLG]

Set of D-Force rims would prob be perfect. Cheap and light...last time they were on sale at UUC for like 365 for a set, guten also had them for about the same price.

[kts]

You guys are overlooking a big part here... and that is that you can easily slap a 205 on an 8 (I've done it), but you can't really run a 225 on a 7. It's ten bucks more for a 15x8 C1 than a 15x7 C1. So you are actually limiting your options by going 15x7, unless you plan on racing in a class that prohibits them. Moreover a 205 will actually be FASTER on a 15x8 as it will put down more contact patch on a mild stretch. No, I am not a stancefag, but the tire will behave better when it is slightly stretched than when it's square.

If it were me, right now, I'd get the 15x8s and 225/45 Rivals. They won't slow you down unless maybe you are on a really high speed track.. which probably isn't a good idea with an E30 anyway. And you will downright giggle at the amount of grip you will get. If for whatever reason you want a 205 later, just get a set and put it on.

+1

My car came with my 15x7 Team Dynamics but if I ever pick up another set of 15" wheels I'll get the 15x8 TRMs so I have options for 205 or 225s. For $10/wheel more it makes sense to get the 15x8s.