tire sizes?

[Black_Havoc]

I'm wondering if 225/45/ZR16's will fit on stock rims, without rubbing the fenders under full turning. They should right? There not any taller, but slightly wider. I have 205/50/16's on now, but want something a little more sticky in the corners. What brand does everyone reccomend? I have Eagle GT II 's on it now. Thanks

 

[SlowSpyder]

I think those are too wide for the stock 6" wide wheels. Id go with 215/55/16s max on the stock wheels. But if you really wanna use wider tires on the stock wheels use 225/50/16 because it matches the rolling diameter of the stock wheel/tire where as the 225/45/16 are almost an inch shorter in rolling diameter than the stock wheel/tire combo and that will mess up your speedo abit

 

[deyja6]

i have 225/50/16 tires on my stock rims. works just fine.

 

[jtmcinder]

Yeah, a 225/50/16 probably won't pop off a 16x6 wheel, but you sure are wasting a lot of potential lateral grip. Moving those tires onto 16x7s or 16x7.5s would probably up the grip by at least 10%. Maybe even as much as 20%. More important, on those wheels, 215/50/16s or possibly 205/55/16s might have more actual lateral grip than your 225s.

Seriously.

- Jtoby

 

[Black_Havoc]

I used this link to deduce 225/45/16 will work, going from 205/50/16's. http://www.miata.net/garage/tirecalc.html according to that, SlowSpyder, the tire is identicall in sidewall height, identicall in diamater, 1 tenth less in radius, and 3 tenths less in circumference, and only 3 revs more per mile. So that makes the speedo fast by .4% Now if I used 225/50/16, like the deyja6, the speedo is slow by 3.3%. Deyja6 if your 50's work, then the 45's definatley will. All I really wanted to know was if they rubbed anywhere.

I had 195/70/14's on my Fiero and went to 225/60/14's. I noticed no lateral "Slop" it actually gave me better times in the slallom, coming from the TALL&SKINNY 195/70's to a little shorter and a LOT wider 225/60's gave more grip, allthough the bulge from the side was a little wider due to the lack of width in the rims. the 225's were under 1 tenth from normal size in sidewall, diamater, radius, and 3 tenths under in circumference, speedo fast by .5%. With the 195's I could pull two tire burnouts for 15 feet, now with the 225's I'm lucky to get 4 or 5 feet. But thats all good, the less tire slipage, the better.

With those sticky tires I beat an older 260Z. Whats amazing about that is My Fiero is the 2.5 L4 with 98BHP upped to 115 though. ;-) Grip and P/W ratios are all that matter. For exapmle my Fiero weighs in at 2500 lbs, 2500/115 gives me a 21.7:1 P/W ratio, 260's weigh in the 2665lb range with 139 or so hp that gives him a 19.1:1 p/w ratio, but he spun his tires for 10 feet, proving my grip point. To put that in to perspective, a 2G makes 210, with 3100 lbs to push, that gives them a 14.7:1 p/w ratio with AWD, Thus spanking BOTH the Fiero and the 260Z ;-) yet another reason to go buy a DSM! Off topic now, later all.

 

[jtmcinder]

You said that you wanted something more sticky at the corners, which said to me that you wanted more grip. What I was trying to tell you is that wedging wider tires onto a given wheel can actually lower grip, if you go way outside the correct width for the wheel. You have 6"-wide wheels. Some 225/45s will have less lateral grip on this wheel than 205/50s made from the same compound. This general rule is especially true as profiles get lower. The fact that widening the tires on your Fiero helped is not surprising, because you went from a 70 to a 60. Here you are talking about 50 to 45, which is where wheel width becomes crucial.

- Jtoby

 

[deyja6]

i don't claim to be an expert in this area but i thought that having sidewall flex actually increases grip. however, it also lowers response time so the car isn't as nimble. the way i see it, it's best to put the widest tire possible on a given wheel and when when you need the car to be more responsive, just increase the tire pressure.

 

[Black_Havoc]

Ahh I see, weel width with low profile tires is a bigger concern in the 45-50 catergory. With the 70-60 switch its probably not as important. Looks like its off to ebay, see if I can't find some TSW Blade's, or Sport Edition Fox 5 (gotta be split 5 spoke). I think they come in either 16X6.5 or 17X7.

 

[jtmcinder]

Please note that I've been careful to specify that I'm talking about lateral grip. Whether or not skinny wheels and/or flexing sidewalls are better for launching I leave to someone who drag-races. My guess is that the answer is yes, partly to keep your drivetrain from grenading.

The reason that sidewall flex usually lowers lateral grip is that it allows the tire to "roll over" (i.e., the car drives on the outside sidewall, instead of the tread), which, inter alia, lifts the inside edge of the tire off the ground, reducing the size of the contact patch. You want the sidewalls stiff enough to avoid rollover. As long as you have this, you are correct that softer is better. But on 99% of all street tires, the problem is that they are too soft (no matter the air pressure), so you must have wheels that are wide enough.

- Jtoby

ps. that missing 1% is called Falken Azenis