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Widest tire on stock wheels

13 September 2000
Tulsa, OK
What are the widest tires that will fit on the 15" and 16" wheels?

I am planning on 225 fronts and 245 or 255's on the back. Anyone have experience with these widths?

I would recommend against doing that. They may very well fit, but it will not be safe for any form of aggressive driving and, further, your handling will be unpredictable and unsafe because of excessive roll-over on the sidewalls.

I don't think it will look very good either, if better aesthetics are what you are trying to achieve. Think of a what a bicycle innertube looks like on a mountain bike rim/wheel.
What?? Unsafe driving from using a wider tire? Excessive sidewall rollover from OEM tires? And it doesn't look good if you've got wider tires? You better tell that to those with 275's in the back. Weiki, I don't see your reasoning.

Maybe I'm misunderstanding you.
What I am talking about is putting a wider tire on the same skinny OEM wheel. I run 235/40-17 front and 275/40-17 rear, but I have the proper wheel widths to do so. If you put a larger/wider tire on the same skinny rim, you WILL get sidewall rollover, it WILL look odd, and the WILL be unsafe under aggressive driving conditions, producing unpredictable handling.

Re-read my original post.

For every tire size, there is a recommended range of wheel widths which are determined to be safe for the proper functioning of the tire in question. You cannot put, for example, a 275/40-17 tire on a 17x7.5 rim...it might very well fit, but it will not be safe, it will look stupid, and your handling will suck. This is the point I am trying to get across. If you want wider tires, get the optimal or near optimal wheel size to match. Another example, A 215/40-17 tire will fit on wheels that are between 17x7 and 17x8, though the OPTIMAL width for this tire size is 17x7.5. Every tire has a range of wheel sizes it will fit, but there is still the OPTIMAL recommended wheel size.

[This message has been edited by weiku (edited 06 December 2000).]
Here is some more information.

On your 1991-93 OEM NSX wheels, they wheel sizes are 15x6.5 front and 16x8 rear, with 205/50-15 and 225/50-16 tires.

With the OEM tires, starting with the front, the 205/50-15 tire size will fit on a wheel width range of 15x5.5 to 15x7.5, though the optimal wheel width is 15x6.5, which is what the OEM front wheel is. Now, on a 15x6.5 OEM wheel, you COULD put a 225/50-15 tire on, and it would fit, since for this tire size, the wheel width range is 15x6.0 to 15x8.0 (pretty wide range), but the OPTIMAL wheel width for a 225/50-15 tire is 15x7.0. So, in this case, it would fit, it would work, but it is not optimal. The other thing to consider is that if you switch from a 205/50-15 to a 225/50-15, you will be increasing the rolling diameter by 3.4%, or 0.8", and your sidewall will be 0.4" taller. This will affect handling over the OEM size. Yet another issue is that the OEM tires are corner specific and have an internal bias built it in improve handling and steering response. When you move to a non-OEM spec tire, you automatically lose a bit of handling and response, ceteris paribus. On top of that, continuing this thought, increasing the tire size alone will further take away from handling and response/performance.

You can do the same calculations for the rear wheel/tire if you want. These are just my opinions, most of which are based on experience and common sense.


[This message has been edited by weiku (edited 06 December 2000).]
So how do you determine the best tire width for a given wheel width? Neither of the two methods I can think of seem to work very well.

1) Using a ratio of the tire width to the wheel width. For instance the stock 15" front tire is 205mm wide, while the wheel is 165mm wide, giving a ratio of 205/165=1.24. The rear ratio is 1.11.

2) Using the difference between the tire width and the wheel width. For instance, for the front tire 205-165=40mm. The rear difference is 22mm.

Using either method above, it seems the rear wheel has greater ability to handle a wider tire than the front.

My questions:
What is the correct method?
What is the widest tire for a 6.5" wheel?
What is the widest tire for a 8" wheel?

Bob Butler

There are general ballpark figures for determining tire/wheel fitment, but you want the real answer.

The real answer is that it varies across tire brand/manufacturers and models. You would have to find it out from the tire manufacturer. I was using Toyo Tires figures. However, let's say the Toyo Proxes T1S 215/40-17 will fit on a rim width of 17x7 to 17x8, with an optimal rim width of 17x7.5, you can probably bet that a 215/40-17 Yokohama AVS-i or a Bridgestone S-02 PP in the same size will probably fit as well.

Also, the final tire width will be determined by the rim width you are using, within a certain range (I know, I hate this term too...'certain range'...). If you put a 215/40-17 tire on a 17x7 rim, and put the same 215/40-17 tire on a 17x8 rim...the tire on the 17x8 will actually be wider, because it is spread wider, and even though it is the same tire, though the tread width, which is the important part, will be the same, but be slightly different near the edges in geometry.
My questions:
What is the correct method?
What is the widest tire for a 6.5" wheel?
What is the widest tire for a 8" wheel?

I wouldn't go with the "widest" necessarily, for the reasons I listed before. If you squeeze the widest tire possible on any given rim, it will not be optimal, and your handling will suffer.