Tires.....A Pictoral Size Comparison, 18" Wheel Guys Have a look-see Options

[Fastbird]

Ok, knowing there's been some discussions on what size tires for what size 18" wheel that have been started by yours truly, I bit the bullet and spent some money to physically mock up some tires.

We all know that a 215/35-18 tire is as close to stock as it gets, but this leaves a lot to be desired in the ride quality and sidewall height, not to mention that a 215 is a narrow tire for most of the 18" wheels out there. This is what I had on our Celica before and a rim paid a very dear price because of this.

So.....Two sizes came to mind for a new tire. The often talked about 225/40-18 and a tire of my own conjuring, a 245/35-18. Of these, the 225/40 is much more common and quite a bit less expensive, but it also offers a greater inaccuracy of the stock speedometer than the 245/35 does.

Here I have pictures of two different tires mounted on my 18x8 HP Design Wheels HPR5's. They are 215/35-18 and 225/40-18. I managed to find a deal on a couple of used 225/40's to try out, but I haven't found a 245/35-18 to give a shot yet. Anyway, here's the pics and some commentary:

THis pic shows the overall tread width of the two (215 is low, 225 is high. For 10mm of tread with difference, the 225 sure looks wider.


Overall size differences: Yes, the 225 is a noticably larger tire. Speedo is going to be about 5.1% off from stock meaning a speedo reading of 60 when you're doing 63 MPH.



But here's the meat of the issue. Sidewall height and stretch. The 215 on the right/top has a noticeable sidewall stretch, severely exposing the wheel lip to all kinds of damages from things like New Jersey potholes (a moment of silence for my one trashed rim) or curbs or such. The 225 however, is nearly a flush line with the wheel lip with hardly any sidewall stretch. It IS still there though as I noticed when I laid my wheel down it was resting on the lip and not the tire.



Here's some numbers to chew on:

205/55-15 -- 4.4" sidewall, 75.0" circumference, baseline
215/35-18 -- 3.0" sidewall, 75.2" circumference, 0.2% slow, 60 MPH speedo = 60.1 real MPH
225/40-18 -- 3.5" sidewall, 78.8" circumference, 5.1% slow, 60 MPH speedo = 63.0 real MPH
245/35-18 -- 3.4" sidewall, 77.8" circumference, 3.7% slow, 60 MPH speedo = 62.2 real MPH

Now, looking at the 225 and how wide it looks, I don't think the 245 will fit in the wheel well very well without some massaging and clearance work. Yes, it's overall diameter and circumference will be smaller, but the width will cause problems I think. Another size that readily comes to mind is a 235/235 or a 225/35 as broken down below:

225/35-18 -- 3.1" sidewall, 76.0" circumference, 1.4% slow, 60 MPH speedo = 60.8 real MPH
235/35-18 -- 3.2" sidewall, 76.9" circumference, 2.5% slow, 60 MPH speedo = 61.5 real MPH

The problem with these is that the short sidewall will again cost ride quality and not offer a bunch of protection against sharp impacts like a pothole or something.

The 235/35-18 unfortunately isn't a common size at all, and the absolute cheapest tire in that size is going to run about $200 per tire, whereas the 225/40 can be had in a decent tire for a very reasonable $100-125 per tire. The 245/35 will cost about $160-200 for a decent tire.

My personal feelings are that a 235 width is going to be about perfect for an 8" wide wheel to just get the tire to extend out past the lip of the wheel, but to keep things sane in the overall size department you'd need to stick with a 35 aspect ratio as the 40 would be too big overall. I am trying to locate a 245/35-18 tire to test fit and see how it looks. The 225/40 looks great, but I'm not sure how the larger size is going to make the car look. Right now my inclination is going to be to go with the 225/40-18 because I was very surprised about how wonderfully the tire fits the wheel. I'm going to still actively look for a 245/35 but if I don't find one by the time I get the wheels back from being refinished, then I'll stop at that point.

Hopefully this helps people out. I've done a lot of searching on here for how different size tires look without finding good shots of how the tire actually looks on the wheel. That sidewall stretched euro look is absolutely silly in my book and aside from looking ridiculous, it puts your hard earned rims at risk. This post was meant to show how the size will realistically affect how the tire looks on the wheel and to offer a bit of education and help in choosing a tire size for you 18's.

[Batman722]

that 215 on the 18" wheel is tiny, is the wheel 18x8 or 8.5 ?