I've noticed that many of you w/ 8" rims are running 235 x 40's instead of 245 x 40 size tires.
I almost did the same but when I checked the overall dia. change I found that the error for 235's is 1.8 and the error for 245's was only .5 on the same rims.
I was less concerened about speedo error than I was with adding more fender gap by using the 235. After all I just dropped the car to reduce fender gap.
Master of all things rubber are you out there.

 

bump

 

Hrmm like most people I read the recommneded tire width which was 235 Of course once I saw it on I realized the error that was made......

Like you I could also care less about the odo error I just wish more people talked about the width that looks the best.....

 

Plus it seems strange that a tire with the same aspect ratio in a wider foot print would also produce a greater dia.

 

Same thing here, got them b/c they were the recommended tire.. But if I could take it back I would have gotten 240's or 245's...

 

What I mean is thank you for being here and sharing your experiences good or not so good.I guess that is what this board is all about.

 

Aspect ratio is a percentage of the width. a 35 series tire that is 335mm wide is still going to have a "decent" amount of sidewall compared to a 35 series 245 tires.

 

Bump

 

I run 245s on my 18x8s I wouldnt really trip about running 235s... 235s arent bad cheaper more available tires in that size... I run 245/40s so my speedo is a lil bit off... thats about it

 

That's one of the points is that speedo error is less with 245's x 40 than with 235 x 40

 

wat about 18 x 7.5 wheels? 235?

charlie

 

There are a few reasons:

1. 235/40/18's are a lot more readily available than the 245's thus making them a bit cheaper

2. 235's will have a better ride

3. Some people think that the 245's have too big of a sidewall and look too "balloon like"

4. Most of the 18 inch wheels are only a 7.5" width which can't safely accomodate the 245

5. And most importantly - the 245's will rub on the rear fenders on many of the offsets available. My wheels are 18x8.5 +37 and I had to roll my fenders 3 times and they STILL rub sometimes.

Either way, you can't really go wrong.

 

so would 19x8.5 inch rims with a 245 tire and a 40 mm offset rub?

 

shouldn't. There are other people out there with the same setup as me that don't rub, just take it as word of caution.

 

Thats my setup, and I dont rub at all .

 

Little confused here. My stock tire size is 215/55/16. On the tire calculator I use, it tells me 235/40/18 is closer to stock size than 245/40/18. So, if you are concerned about speedo/odo error, wouldn't you want to 235/40/18?

Mike

 

This is a good illustration of mods for appearance vs mods for technical or performance reasons ending up with different results.

The effect of speedo/odo error may slightly depend on whether you're upgrading from 215/55-16's or 225/50-17's.

From a crispness of handling perspective, a wider rim relative to a given tire size usually improves things. The converse is to use a narrower tire of the same profile on a given rim width for a sharper feel (assuming adequate capacity, of course). The 245 width tire would actually prefer to work on a wheel that's about 1/2" wider than what you'd use for a 235.

Norm