Stock 17" Wheels/Tires?

[1lowufo]

Can't figure this out...the stock 17" tire is a 205/50. How come
the plus sizing shows 225/45??? I have 16s and what to go to 17s, what tire size?
205/50
215/50
225/45

[CREWZIN]

I'm pretty sure all those you mentioned will work well and keep the speedometer and Odometer almost correct. Not sure of the exact science but the 205 (normal) and 215 (just a tab wider) will keep everything the same, but when you get bigger (225) it messes up the equation and you need to go to a smaller ratio (45) to keep it all equal. [:I]

[2step]

What you want to do is keep the diameter (and circumference) of the tire/wheel the same whenever you change sizes. Changes to the diameter will effect the final drive ratio which effects the speedo, milage, power output, etc.

Here's a link to a tire size calculator to compare different sizes.

http://www.miata.net/garage/tirecalc.html

Simply put in the numbers of the stock/starting tire and the "new" preposed size. If you want a wider tire, put in the desired width and try a few different ratios to check out what happens to the diameter. You want to stay close to stock diameter.

[SteelBlueGT]

Remember the stock 17's are very narrow (6") so 205's are as wide as you can go with those wheels.[8)]

[ElectricBlueGT]

quote:Originally posted by SteelBlueGT

Remember the stock 17's are very narrow (6") so 205's are as wide as you can go with those wheels.[8)]

Actually, 215/50/17 fit just fine. Yokohama and other tire manufacturers also show 215 wide tires as acceptable to mount on 6" wide wheels.

Scott

[MichaelDay]

quote:Originally posted by ElectricBlueGT

Actually, 215/50/17 fit just fine. Yokohama and other tire manufacturers also show 215 wide tires as acceptable to mount on 6" wide wheels.

Scott

The 215/50-17 will fit on the 6" rims but there will be a small increase in rolling radius, thus changing the parameters the engine/transmission is expecting to see. You will actually be going faster than the speedometer indicates (1 mph at 60), traveling more miles than the odometer indicates (1.6%), and slightly reducing your acceleration. All of these are within acceptable limits of a 3% change.

[SteelBlueGT]

My Bad, of course you can upgrade to 215's that is what I did!! But the point I was trying to make is that you cant go to plus 1 or plus 2 sizing with those skinny wheels. So there is no upgrade available as far as going to a lower aspect ratio. Lost the forest cause of all those trees again. Sorry! [:I]

[1lowufo]

Thanks alot for all the info. I think I got it. Tell me if this is right...
The stock 17" wheel is 6" wide and rolls on 205/50-17s. If I go to a 7" or 7 1/2" wheel I should roll on 215/50-17s of 225/45-17s !

[SteelBlueGT]

Here is my idea go with 225/45/17 with 7" wheel width. You will gain handling with the extra width and lower aspect ratio and also stay within a .5% of the stock 17" wheel\tire rolling diameter. Depending on the tire, comfort should be pretty good too!! I feel that if you are going to buy other wheels why not get a big benefit in handling too for your money??

[2step]

I was once one of those that thought 225/45-17's were too wide for the 6" wide stock wheel. Here's a shot of that combo.....

There is only a half inch of "bulge" at the sidewall and that is a nice cushion to protect the wheels from curb rash. I also had the opportunity to measure the actual width which is 6 1/4".


Make that WHEEL WIDTH = 6 1/4"