# wheel/tire selection



## dtbaker (Jan 5, 2008)

now that my ev is rolling.... I want it to roll BETTER! I am considering new aluminum wheels (much lighter? ) and good LRR tires. But, I am lost in choices, and so far have not been able to dig up key info for aftermarket wheels like what the offset has to be.

Stock tires on a 1997 suzuki swift were p155/80r13 , which is NOT what is on there now.

I am thinking it is probably NOT a good idea to go for low profile tires because I DONT need a stiffer ride and am not planning hard cornering. 

so..... 
1. how can I find out what the wheel offset should be?
2. If i go with stock width of 155 , should I get 13x5" or 13x6" rims?
3. any good online sources for cheap but still light AL wheels?
4. any specific suggestions for all season LRR tires?


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## Jimdear2 (Oct 12, 2008)

dtbaker said:


> 1. how can I find out what the wheel offset should be?
> 
> Take off a stock wheel
> On the back side, lay a streight edge across the metal edge. Stay off the tire
> ...


Hope you can use this information.


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## madderscience (Jun 28, 2008)

Stay with narrow rims. Narrower tires tend to roll better, all else equal.

Goodyear Integritys, Goodyear invictas, Sumitomo srixon4's and a bunch of other tires are considered good for low rolling resistance and are available in lots of sizes. If all else fails, buy the tire that is rated for the highest PSI you can find (the sumitomos go up to 51psi) and run them at that pressure if not a little more.

After PSI, Buy the narrowest tire you can fit on your rims after finding the highest PSI you can get. the 155 in your tire size example is the section width. 

Ratio of height to section width (the 80) in your example: after the previous two rules, pick the lowest ratio you can. This might help aerodynamic drag a bit by lowering the car a little. It will also slightly increase motor RPM and torque at a given speed since the tires are smaller diameter.

So if there is such a thing as a 145/70R13 that can take 51psi, I would go for it.

As for steel vs. aluminum, if you hill climb a lot the lower weight would be most beneficial. If you drive on the freeway more, alloys or just hub caps with a smooth, minimally spoked profile would allow for a reduction in aerodynamic drag that would probably be more significant that the weight reduction from very light wheels.

Other things to do: get a 4 wheel alignment job. Make sure the brakes do not drag. If any suspension bushings/joints are sloppy, fix them (before the alignment job). If you haven't already, use a lightweight synthetic oil in the transaxle/differential.


Have fun.


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## madderscience (Jun 28, 2008)

Stay with narrow rims. Narrower tires tend to roll better, all else equal.

Goodyear Integritys, Goodyear invictas, Sumitomo srixon4's and a bunch of other tires are considered good for low rolling resistance and are available in lots of sizes. If all else fails, buy the tire that is rated for the highest PSI you can find (the sumitomos go up to 51psi) and run them at that pressure if not a little more.

After PSI, Buy the narrowest tire you can fit on your rims after finding the highest PSI you can get. the 155 in your tire size example is the section width. 

Ratio of height to section width (the 80) in your example: after the previous two rules, pick the lowest ratio you can. This might help aerodynamic drag a bit by lowering the car a little. It will also slightly increase motor RPM and torque at a given speed since the tires are smaller diameter.

So if there is such a thing as a 145/70R13 that can take 51psi, I would go for it.

As for steel vs. aluminum, if you hill climb a lot the lower weight would be most beneficial. If you drive on the freeway more, alloys with a smooth, minimally spoked profile would allow for a reduction in aerodynamic drag that would probably be more significant that the weight reduction from very light wheels.

Have fun.


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## CPLTECH (Sep 14, 2007)

I agree, thinner is best for MPG. For a tire comparison chart, go to this site and fill in the blanks:
http://www.miata.net/garage/tirecalcold.html

It also provides the speedometer differences to expect.
Keep in mind that you often have a heavier vehicle that may require an improved load rating.


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## dtbaker (Jan 5, 2008)

turns out that tire/wheel choices in 13" rim size are pretty limited... almost everything has moved to 14" wheels, probably to allow bigger disc brakes. I settled on the kumho Solus kr21 155/80r13 tires as they come with 85,000 mile warranty and excellent ratings for noise and traction. I found a good price on them at www.performanceplustire.com for $60 ea, plus shipping.

This particular vendor was one of the few where I found 13" aluminum wheels as well. narrowest width is 5.5", which is wider than the 4.5" stock steel wheels, but should be ok for the 155 tire width. The only wheel I found with 13", 4-bolt on 114 dia, 38mm offset was the 'Primax 333', which turns out to weigh a scant 13#.

I am debating whether to order the wheels, or just stick with the stock steel... I don't know what the steel wheels weigh without tires, and I don't know if its really worth doing. 

The AL wheels are probably significantly lighter, but they have a very 'open' spoke design so would be less aero than the stock steel/hubcaps which are pretty smooth. My normal average speed around town is probably only 30-35mph, so aero is probably less important that stop/start inertia.

comments?


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## DavidDymaxion (Dec 1, 2008)

http://www.jegs.com has drag skinnies, wheels and tires. Light weight and low rolling resistance, but I wouldn't want to corner hard on them.


dtbaker said:


> now that my ev is rolling.... I want it to roll BETTER! I am considering new aluminum wheels (much lighter? ) and good LRR tires. But, I am lost in choices, and so far have not been able to dig up key info for aftermarket wheels like what the offset has to be.
> 
> Stock tires on a 1997 suzuki swift were p155/80r13 , which is NOT what is on there now.
> 
> ...


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