I see a lot of people are running 245/40/18. I was thinking of going with the 255/40/18 instead. After checking out the miata tire size calculator, it seems the 255's are closer to OEM in every way than the 245's are. Does anyone have any input on the 255.

Also, I was debating between the Goodyear Eagle GT and the Goodyear Eagle F1 All Season . Anyone have any input on these tires?

I don't track the car, but I do enjoy spirited driving. I need a tire with a high tread wear as well, due to my 65 mile one way drive to work each day.

Thanks.

 

I found I didn't like 245s, subjectively speaking, on 8" rims. You are squeezing too much tire on too little rim, and the tires get a little soft on turn-in. I'd think 255s would be even worse.

This is based on Toyo T1-Rs. Liked 'em better on 8.5s. With the Dunlop Star Spec 245s, which run wider than the Toyos for any given size, I think 8.5" is even too narrow. 9" would be better.

How wide are your rims?

 

The rims were on my car already when I bought it, but the 225's (Dunlop Direzza DZ101) on them right now seem to be a bit stretched, so I am thinking probably at least an 8.5

 

Interesting. I suspect that if you pull one of the wheels off, the size will be cast into the wheel on the inside, in the hub area. Or at least a model number that would let you figure out the size.

Of course, if you are not overly worried about subjective impressions, then the wider tire will proabably give more grip than the narrower one, all other things being equal. But if you want nice, crisp turn-in it helps to match the tire size to the rim width.

 

Remember, your gas mileage will suffer (due to the increase in friction) with a wider tire. The reason the 245/40's are used is because the circumference of the tire is closest of that to the OEM. Going to a larger tire (255) would make your speedometer read lower than the actual speed.
I like the Eagle F1 All Season tire. It will be the one I get next for my car. But, your in central Texas. Why do you need an all season tire? The Eagle GT may be better suited for your purposes.

 

the stock wheel is only 8" wide; anything more than a 245 and you'll have really soft sidewalls. For ex. I have 255 on a 9" rim and wouldnt go any wider (maybe it's just personal taste) but I HATE a soft sidewall

 

Toxic doesn't have stock wheels, he has a set of aftermarkets that were on the car when he bought it.

Dan, I ran 245/40s for the longest time on stock wheels at plenty of track events and suffered no ill fate. As you know I'm running 275/35s on 9" wheels and absolutely love them! I think the 255s will suit your wheels just fine.

-Nic

 

Yeah 245's are max on the stock wheel. Or even for the ones you have. Im guessing the 255's will fit, but the handling might be worse due to the soft sidewall. I hate soft sidewalls too, doesn't make the car feel so awesome if you know what I mean :P But seriously, go with 245's, you'll be happy with it. Also, this car doesn't need past 245's as there isn't much torque and power compared to other cars. If anything, it's a bit of a waste.

 

Dan, those HPR5's you have came in a 18x8 and 18x9. If they're 8" go with the 245/40s, you can run the 245s on a 9" also.

 

Sure, you can run them, it's just a question of what the OP is after. Max grip and/or fastest lap times, well then feel-be-dammed and get as much tire on the rim as you can, within reason. Autocrossers & track day addicts know this well. But that wings-bolted-to-your-arms feeling (to quote one noted race car driver) that makes the car so much fun on the street can easily be tainted with an innapropriate match betwen the wheel and tire. In my experience, anyway.

 

Thanks Nic, I love the look of yours.

@Ross, I guess I should have pointed out that the wheels are not stock, but the info is in my sig. Most likely overlooked as most sigs usually are.

@ alneilsen, I understand the MPG issue, but really what are we talking here? 1/2 a mile a gallon? I figuered the F1 would be better due to the rains we can get at times around here. The treadwear is just slightly higher as well. Also the carbon fiber reinforced sidewalls on the F1's I thought might prevent the soft sidewall issue (if any) more so than the GT's. You also said the circumference of the 245/40 is closest to OEM, but the miata tire size calc actually says;

STOCK 225/45/18
sidewall 4.0 in
radius 13.0 in
diameter 26.0 in
circumference 81.6 in
revs/mile 777



245/40/18
sidewall 3.9
radius 12.9
diameter 25.7
circumference 80.8
revs/mile 784

with a speedo reading of 60 you are actually going 59.4



255/40/18
sidewall 4.0
radius 13.0
diameter 26.0
circumference 81.8
revs/mile 775

with a speedo reading of 60 you are actually going 60.1



So as you can see the 255's are actually closer in size to OEM than the 245's are, (not including the width). Also with more revs per mile on the 245's you would actually rack up mileage on your car that you really are not traveling. (does that make sense, I think I explained it correctly?) I bet the 245/40's are more popular around here just because they fit so well on the stock rims.



Hmmm, I just found on Goodyear's site the approved rim width for each tire is different. That is strange because they are the same size tires. The Eagle GT says the approved rim width is 7.5" - 9.0" for the 255's and the F1's are 8.5" - 10" I guess I need to find out the width of my rims first huh? Oh well, back to the drawing board for now. I'm in Dallas without my car for another week anyway.

Thanks for all the responses everyone.....I love this site.

Dan

 

Sweet, thanks for the info. BTW where did you manage to dig up that info. I have been unable to locate anything like that. I guess the HPR5's are no longer available.

 

When I look at tire specs, I look at what is listed for the exact tire rather than the Miata table. You can go to the Tire Rack site and get the exact size to compare against the OEM Bridgestone/Dunlop tires that came with the car. I don't remember the exact diameter/circumference of the tire, but it is 800-805 revolutions per mile.

 

Very interesting, thanks for that info. I was going off of Discount's site also and their size calc does the same thing as the miata one. I'll have to check out Tire Rack. I never knew there were so many differences in something that was marked as being the same size, even within the same brand as I found with the Goodyears that I have been comparing.

 

Dan, I use this tire calculator. It actually displays a wheel diagram of the wheels and tires you want to compare. http://wheelsmaster.com/rt_specs.jsp

 

I think one of the main reasons so few people run a 255/40 is because of tire selection. There are plenty of 245/40-18 performance tires, but for some reason very few 255/40-18s. In the Extreme Performance (SCCA ST class) classification, only the Advan Neovas offer a 255/40-18, but everyone else offers a 245/40-18.

 

@ alneilsen, you are right about Tire Rack. You can find out a lot more about the specific tire. Damn, now it's even more confusing. Thanks again.

 

I run 255-40-18 PS2's on 18X8 wheels as my street tires.