another rim width question.
 

I researched rim width, but never found an answer. will running the same size tire on a wider rim lower the heighth of the tire. if that is the case, a wider rim should lower mpg. my crx has 4" wide rims, but one of them looks like it has been replaced. I haven't determined if it is 4", or 4.5". it is on the front. . I am thinking I should switch it to the rear until I can determine the width, or find a replacement rim. Am I worrying about nothing because of the small difference?

Depends on the situation.
Ideally the sidewall is near vertical, and the tyre isn't stretched out or pinched in to fit the rim.

If I look at my own tires, 205/55R16, these may be fitted on 5.5 to 7.5 in wheels according to Tire Size Calculator - tire & wheel plus sizing so that's 5 rim widths.

Even though the fitment might be totally fine, a wide rim will angle the sidewalls out , while a narrow rim angles the sidewalls in, both giving a marginally lower sidewall height (when measured vertically).


Starting with a pinched-in situation, a wider rim might pull the sides more vertical.

Not enough to worry about.

What about the aerodynamic effect. Shouldnt you also try to get same 10 degree "kammback" shape on to the tire to lower their aerodynamic resistance?

That I will try to test this summer also on my Lupo. Try to stretch the rubebr to 10 degree angle.

I agree that effect to diameter does not have measurable effect, but what about the aero?.

I have my own eco tire designed for less aerodynamic drag wise plus some other tricks, but Nokian Tyres did not see that that kind of tire would fill their requirements for tires they have.

I can send the file to any tire maker who is willing to make the first tire to my lupo size spec ;).

It is obvious this is bothering you, so move that wheel to the rear.

You KNOW you will sleep better. Now, in your dreams, count the left, and right sweepers,
and sharper corners you take in your travels. Picture yourself coasting rapidly down those mountain roads when the pavement is wet.

Now you know which side of the back to put it on for a little extra insurance of control!

(you know I'm partly teasing here; right?)

my main concern was difference in diameter between the two drive wheels. but if they are close enough to not make a difference, I am not going to worry about it. thanks for the info

I wonder if a potential difference in weight/drag could affect the driveline? It's probably inconsequential too, though.

okay, I kept looking at that front tire, and how it looked so much wider than the other tire. I pulled it off ,and weighed it. 29lbs. pulled the corresponding rear tire and weighed it. 26lbs. I put the wider rim on the rear. It seems to steer easier, and it is probably my imagination, but it seems to have more power. my stock rims are 4.5", I located another 4.5" rim , and am replacing the 175 70 13 tires with 165 70 13 tires monday. the larger rim was only .5" wider, but it sure looked out of place compared to the other rims.

So strange... I'm guessing the person couldn't find a stock replacement?

I can feel the weight increase through the powersteering when I put my heavier summer tires on.
It's no imagination.