Hi.. i'm brand new to this forum and i also don't know much about what is right for my car and i have no one to go to for help.. besides the ppl at my wheel and tire shop.. which i do not always trust.. sooo.. any suggestions would be very helpful.

I drive a '05 coupe with 18"s on the original Michelin tires. I need to get new tires soon and I figured it's a good opportunity to upgrade my wheels at the same time. Can anyone suggest the proper wheel dimensions and tire sizes for 19"s and 20"s? I don't have any modifications and I don't want to do any lowering. Thank you!

 

For the 19" the tire specs are

Front: 225/40/R19
Rear: 240/40/R19

Thes are the OEM specs.

 

for 19's, if you're not lowered... 255/35F 285/35R

For 20's, 245/35F 275/30 or 285/30
-GP-

 

Correction, for coupe 20's, 245/30/20 or 255/30/20 front, 275/30/20 or 285/30/20 rear. A 245/35/20 is taller than a 275/30/20, bad choice IMO

 

OEM height is 26.72"
I don't think 245/30/20 is a good choice since it's .9" shorter than OEM 19" rims, and 275/30/20 is only off by .1" 275/35/20 is .9" taller than OEM.

245/35/20 front 26.7" tall
285/30/20 rear 26.8" tall
each tire brand varies somewhat, but this is pretty close and a good choice for 20's, just check the tire overall diameter before you buy.

 

Maybe you should do your math again, because its WAY off. OEM 225/40/19 is 26.1" tall, 245/30/20 is 25.8" tall, a 1.1% difference. A 245/35/20 is 26.8" tall, a 2.6% difference, and is actually taller than a 275/30/20 by .3". If you went with a 255/30/20, then its 26" tall, and almost spot on for a 225/40/19 stock size. 35 series tires should NOT be used on a coupe in almost any circumstance.

 

according to the web site I was using the size for a 225/40/19 size tire is 26.7" tall. That info could have been wrong so I'll give it the benefit of the dough..

I searched a generic calculator and it states the following:
http://www.miata.net/garage/tirecalc.html

225/40/19 is 26.1" tall
245/40/19 is 26.7" tall.

front
245/35/20 is 26.8” tall a 2.6% difference
245/30/20 is 25.8" tall a 1.1% difference
255/30/20 is 26.0" tall a -.2% difference – very close

rear
275/35/20 is 27.6" tall a 3.2% difference
275/30/20 is 26.5" tall a -.8% difference
285/30/20 is 26.7" tall a .1% difference – very close

based on this new info I would say a 255/30/20 and 285/30/20 is your best bet on a 9” and 10” rim respectively. Like I said each tire varies slightly these numbers might not apply to the brand of tire you get, so ask before you buy.

 

Fixed

 

but still 90% of people here run a 35 series up front on 20's....
-GP-

 

Just because alot of people do something doesn't make it the correct choice. I'll never recommend that size to anyone with a coupe on 20's. It just doesn't make any sense to me

 

Thats probably because the sizes given by manufacturers and distributors are not always the same. Add to that the fact that size varies slightly by brand and you got a big pot full of confusion and misinformation. Some people run 35 series because they want a little more cushion to protect their rims, some do it because that is what the store at time of purchase recommended they use. I know most stores where I live say that 35 series up front is the correct size when you run 20's.

 

i think the reason why is because 35 up front has a much broader tire selection.. at least based on what i've been trying to find...