205 or 225 which is faster?

[GThomas]

Hey fellers. So I've been doing some research and a lot of the Miata folks tend to think that 205/50 is faster than a 225/45 on 15x8's. I've had 225/45 Rivals on 15x8's last season but there doesn't seem to be to many tire options right now. I really want to run the Star Spec Direzza's again which are available super cheap in 205/50 on the 15x8's. Also noticed that Tirerack has a few cool looking new 15x8's coming out.

Anyways what are your guys thoughts. I think the Miata folks tend to think that although the 225/45 has a larger contact patch, the slight stretch on the 205/50 makes contact patch much more stable on turn in etc.

Thoughts?

[lcoleman]

Track or autox?

Obviously 225 on a 9 is the best of both worlds, but I've yet to find a light, cheap 15x9 that fits e30s without a massive spacer.

Pure speculation: I'm thinking that (assuming the same tire/compound) a 225 on an 8 will have more ultimate grip, but the 205 on an 8 will be slightly stiffer and therefore "feel" better. Probably down to personal preference, and tbh I doubt you're competing for a national title in an e30 anyway. I'd buy what's cheap and go have fun.

[Bglad]

205 on 8, 225 on 9. I would look at the new Hankook V2.

[GThomas]

Track or autox?

Obviously 225 on a 9 is the best of both worlds, but I've yet to find a light, cheap 15x9 that fits e30s without a massive spacer.

Pure speculation: I'm thinking that (assuming the same tire/compound) a 225 on an 8 will have more ultimate grip, but the 205 on an 8 will be slightly stiffer and therefore "feel" better. Probably down to personal preference, and tbh I doubt you're competing for a national title in an e30 anyway. I'd buy what's cheap and go have fun.

Just Autocross for now, and not really competing for any titles, just trying to win my class in BMWCCA and progress in SCCA and some Porsche days. I may try the 205/50 Star Spec 2's as they are only about 100 bucks a piece.

[nando]

miatas are lighter than E30s. keep that in mind.

[nrubenstein]

miatas are lighter than E30s. keep that in mind.

Yep. The other factor is getting heat into the tires. (Also, to a much lesser degree, carcass weight.)

Really, though, the tire matters a lot more than a small change in width. You're generally better off taking the best tire in a size that works, than taking a worse tire in the optimal size.

[djjerme]

+I don't know about in Autox speeds, but the Rivals on the track (Chumpcar) are a smidge faster than the StarSpec's. I have run 205/50's, 225/45's and 225/50's on 15x7 Konigs for the past several season, and I actually preferred the 205's. Of course, these were all in Toyo RA1's. The 205 I think had the slight benefit of lower rolling resistance down the straights, and so I averaged a very slight faster top speed. In low speed like AutoX, you might not experience this, and the wider footprint of the 225 may actually benefit you.

[reelizmpro]

I'm not surprised. I see a lot of practical advantages to running the small tire. Those not mentioned yet are cost, less weight, less drag, and gearing (if the OD is larger on the bigger tire).

[Delta]

I think there was a comparison done by Grassroots motorsports that showed (on a miata) the difference between a 205 and a 225 was marginal at best. Stick with the 205, it has it's advantages.

[Don Stevens]

I agree with 205 from the pure physics argument (less weight, rolling resistance).

If you want to win at autocross you need the best combination of stickiest compound and heat up quickly that you can find. That also assumes thta you have a second set of wheels for autocross / track only.

If you only have one set of rims you need to consider what is most important to you. tenths of s econd, cost, or even the way the car looks. 225s on 8s is a meaner look for the street.

Don

[nrubenstein]

Well, for autox, as a rule, more is better. These are not Miatas and they want more tire. There's a reason why the few folks who are serious about E30s are running 275s.

[Delta]

On an 8" wide wheel either will be fine. The few running 275s aren't running on 8s or street tires for that matter.

The only thing with the 225 will be tire selection and getting heat into them on colder or rainy days depending on where you live. Vehicle weight plays a role in the decision too (4 vs 6 cyl, weight reduction, etc)