weight vs. width

[MoonieGT]

I've started looking for stickier tires for my 15x7 wheels. I noticed that the 205/50/15 Dunlop Starspecs weigh 3lbs more per tire than the 195/50/15's (according to tire rack). I can't imagine the extra centimeter in width is worth 3 lbs of unsprung tire weight right?

[jrj512]

That is one of the reasons I went with the 195. Gearing was the other.

[sammm]

Don't narrower tires 'spin up' faster? IOW, the car will accelerate a bit faster since there's a smaller contact patch.

[MoonieGT]

If they are lighter, they will have have less inertia. That should help acceleration, braking, and turning. The question is where is the dividing line? Track junkies seem to agree that a 9 inch rim is the way to ultimate grip. 6ULs with fat rubber are several pounds heavier than a light 15x7 wheel and tire combo. I think the 195 vs 205 debate on a 7" rim is a no brainer if you'd be adding 3 lbs of weight. The other issue I'd consider is that tires for 15x9 are much more expensive and so is the initial cost of the wheels. So how much more grip do you get? As I'm not competing against anyone at track days, im thinking I could get more bang for the buck by sticking with a 7" rim...

[sean]

If they are lighter, they will have have less inertia. That should help acceleration, braking, and turning. The question is where is the dividing line?

A few pounds wont make measurable differences in acceleration, braking, or turning.

Track junkies seem to agree that a 9 inch rim is the way to ultimate grip. 6ULs with fat rubber are several pounds heavier than a light 15x7 wheel and tire combo.

The 15x9 6UL + RS-3 is 34.5 lbs
How much do your 15x7's weigh? Unless you go with RPF1's or something very expensive the 15x7/195 package will not be more than 3-4 lbs lighter

The other issue I'd consider is that tires for 15x9 are much more expensive and so is the initial cost of the wheels.

Tires for 15x9 are cheaper. RS-3 = $103 195 star spec = $114

[jrj512]

IMO, a 195 tire is plenty for a naturally aspirated NA Miata. A 225 is too much tire and too much weight. A 205 might not be too much tire, but I think it is not worth the extra weight. YMMV.

[nealb]

A few pounds wont make measurable differences in acceleration, braking, or turning.

There are a lot of guys who would disagree with that. The RPF1 in a 15 x 7 is 9# 10oz. Inexpensive and readily available Spec Miata wheels must weigh 13# minimum. Other wheels are even more than that. A pretty big percentage difference.

[MoonieGT]

I do agree that acceleration, braking, and cornering won't improve much (but the engineer in me says improvement is improvement).

A 195 tire should weigh 18-19 lbs, a 225 tire weighs 24-26+ lbs. That's significant weight...

[SirHustlerEsq]

I'll take the wider tire for Hallett, skinny tire for TWS.

[motorollow]

I believe the 205 Star Spec is "larger" than other 205's. I have Star Spec 205-50-15's mounted on 15 x7 Rota Slipstreams. You are welcome to look at them.

[MoonieGT]

It must be if it's 3 lbs heavier than it's 195 sibling.

[motorollow]

The Star Specs have great wet traction. I daily drive mine and they have never felt like they were going to break loose on wet roads.

[MoonieGT]

Even on a wet MSR :)

[sean]

A 195 tire should weigh 18-19 lbs, NO 225 tire weighs more than 22 pounds. That's insignificant weight in most situations...

FTFY

Your C1M wights 13.6 pounds. thus the 195s will weight ~31.6 pounds

6ULs + 225s will weight ~34.5 lbs (less than a 3lb difference)

Yes RPF-1s + star specs could make the 195 package significantly lighter (over 6lbs) but will cost $100 more than 6UL's + 225s while only being faster in the rain. No cheaper 195 package will be more than 4lbs lighter than 6ULs + 225s.

IMHO. The 225 RS-3 will be faster on your NB given the appropriate 15x9 wheel and the RS-3s are cheaper over the long run. Cheaper tire with better wear characteristics.

[MoonieGT]

I agree with all of that. I know my wheel does not compare favorably from a weight standpoint. I was just getting at that you could put together a very light 15x7 package (which you pointed out up above). I'm just interested in hearing people's takes on the width vs weight argument. 6+ lbs per corner seems like a lot. I wonder if the majority of whatever advantage that gives you would come in the form of better wheel control over broken/bad pavement? Maybe able to use more curb etc? I'd love to see lap time comparisons to see what kind of times each can achieve.

And I don't know if it's accurate, but TR lists the C1M at 13.0 lbs (not that that changes anything).

[Titus]

Sounds like we need to get a low powered Miata with RPF1/195 star specs and a high powered Miata with 15x9 6ul/225 RS-3 out to a track day together and have them trade wheels/tires for a session.

[MoonieGT]

Titus: I'd love to see that happen... any volunteers?

I just looked at TR.com again. Looks like each of the three colors of C1M's have a different listed weight? Not sure what that's about... paint weight?

[sean]

Moonie, you want this for lapping right, not autocross.

There are no non-Rcomp 195's out there that do not go off with multiple laps in Texas heat. With Dunlop 205s at autocross, I could never get back to the first run grip on my NB, no matter how much water I put on them. In 205's the only temperature insensitive tire is the Kumho XS

Here is a reasonable test
http://grassrootsmotorsports.com/articles/top-tires/ On a 7.5 SSR front / 7 RPF1 rear the RS-3's were >.7 seconds faster on a road course than the 205 Dunlops. (In previous testing the 195 dunlop was even more off the pace). RS-3's will be even faster on 15x9's than 15x7.5s of the test.

Even though Andy has these superlight wheels at home, he is taking 15x9 GUL's with RS-3's to one-lap of America.

[MoonieGT]

I'll take a look at that, thanks for the link.

[949Racing]

Width always wins. Sorry to burst your bubble. Once you have chosen the correct wheel and tire width for your intended usage, get the lightest wheels you can afford.

The gains from width= Huge
The gains from reduced weight = small

Yes we want lighter wheels, but not at the expense of grip. Any NB will be faster with the wider wheels. Stockish NA's are sometimes just as fast with 205/50's on 15x8's, particularly on courses that have higher average speeds. On a tight course like MSR, 9's are the way to go regardless of power.