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Wheel/Tire Size Versus Car Handling

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Old 10-21-02, 12:40 AM   #1
markmaz
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Question Wheel/Tire Size Versus Car Handling

I'm thinking about trading cars with my wife. My car is a 99 CL 3.0, hers a 93 SC 300. I like my CL, just can't stand the Bose radio, it stinks.

Anyway, although I'm not into racing, I do want to improve the way the car looks by taking off the stock 15" rims and going to
either a 16" or most likely a 17" rim. Sorry, but I do not plan to
do any lowering.

My question for you experts is this: How will the handling of the car change if I go from:

15" tires that have a 25" diameter, 7" tread width on 6" wide wheels

and switch to:

17" tires which have a 25.6" diameter (to fill the gap some), have
8" wide tread and 8" wide wheels.

Any suggestions for the best size 17" tire that would look good with out any drop on the car? Thanks
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Old 10-21-02, 03:17 AM   #2
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First of all let's get the wheel and tire sizes straightened out. Wheels have two "basic" measurements: diameter and width both measured in inches (IE: 17-inches in diameter by 8.5-inches in width). Tires have three "basic" measurements: width of the tire tread in millimeters, diameter of the wheel it is mounted on, and percentage of the tread width the sidewall amounts to (IE 255mm wide mounted on a 17 inch wheel with 40% of 255mm in sidewall). So when you say 8 inch wide tires, you are saying ~205mm wide tires, which is thinner than stock tread width (215mm).

But to answer your question, a larger wheel with wider tires and thinner sidewall will improve your car's handling. Small wheels with thin tires and huge sidewall will not grab the road as well when you're cornering hard and are more likely to give out resulting in a slide out.

I know you don't want to, but I would suggest you lower the car also about an inch around. This isn't an extreme change to your car, but it does offer some major benefits. Lowering springs will improve the car's handling and give it a more aggressive stance on the road. Just ask RalAedigus about that. She installed springs and struts on her stock SC300 and seems to enjoy them.

And my final recommendation is to go no lower than a 17-inch wheel and look more at 18 and 19 inch wheels instead. They fill the wheel wells the best without having to upsize the overall diameter. Also note that increasing the overall diameter in order to fill fender gap is a bad idea. You start messing with the speedometer calibration, odometer calibration, and anti-lock braking system. Try to stay as close to stock diameter as possible by reducing tire diameter when increasing wheel diameter. This scaling improves handling at the expensive of "floatiness" and "cushiness".
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Old 10-21-02, 09:06 AM   #3
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Thanks Lex400sc for all of that info.

To clarify something, I was looking at tire sizes (tread width and diameter) using the "specs" section of TireRack.com and in thinking about going with a 17" wheel was looking real hard for
a tire size that does not decrease the diameter because it would make the "gap" only appear bigger.

At the same time, I figured since most 17" wheels are wider than the 15" wheels, going with a tire size that has 1" or so more tread width would give me a little better handling/cornering.

Regarding lowering the car 1", what would be the most cost effective way to do that, and since I'm not a do it yourself'er, what kind of shop should I look for to install whatever you suggest? Thanks
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Old 10-21-02, 09:24 PM   #4
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Width can really vary on wheels. In your case, your 15"s are 7.5 inches wide. There are a number of cheapo 20"s that come in 7 inch wide sizes. Thin wheels restrict tire width (and traction) and you can end up with very funny-looking setups on your car. On the flipside, wide wheels lower fuel efficiency very slightly and very wide wheels can slow your car down. If I were you, I'd stay in the 245-265mm range for the rears and probably 225-235 on the front, which is a staggered setup (can't do tire rotations). This ends up being 8.5-9 inch wide rear wheels and 8-8.5 in front wheels. A uniform setup would be something like four 245mm tires on four 8.5 inch wheels.

You'll have to do some shopping around for a garage that installs aftermarket springs, but that shouldn't be a problem in Atlanta. Stay away from the dealerships because they will probably price rape you on something like this. You may have to make a few calls before you find a shop that'll do it for around the mean $150-250 labor. Depending on the market, you might find install labor as low as $100. The springs themselves depending on what brand and model you want can be $220-350. Online shopping will most likely be your best value. Make sure you get your car re-aligned a few days after the new springs have had time to set too. Not too critical a matter, you can actually wait for your car's next scheduled alignment if you want or time them to coincide.

Last edited by lex400sc; 10-21-02 at 09:29 PM..
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Old 10-21-02, 09:38 PM   #5
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Mark, give my friend at Wheels Direct a call.

He can give you the best prices if you tell him I sent you.

Anthony
770.474.6661

I will be getting my 19's from his shop.
Also, he owned an SC so he knows his stuff.

I agree with Lex...besides, 1" is VERY VERY conservative, yet offers improved handling while maintaining OEM Quality ride (had the Eibach setup on my Legend coupe 2 years ago.

hope this helps
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Old 10-21-02, 11:25 PM   #6
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lex400sc, his wheels are 6.5" wide, not 7.5", other than that a very informative and detailed post....
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Old 10-21-02, 11:41 PM   #7
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Hey Lex, so the SC300s have 6.5 inch wide wheels? Hrmm, time to update the FAQ Thanks!!
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Old 10-22-02, 12:04 AM   #8
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No problem brother, 6.5" for SC3 and 7.5" for SC4. Ethan asked me a couple times to get with you on the FAQ, i've been meaning to do that, been real busy lately, we're getting in an '03 SRT-10 in Graphite in a couple days and you can't buy them unless you have the certificate that you already own a Viper, long story short we bought a certificate from a customer that had two Vipers, so things have been a little hectic while guys try and get their hands on it, but business is looking better again, so the timeframe for Luthor v2.0 may be back on track after all. Anyway, let me know if you need any help on the FAQ, and if I can manage some time i'll do what I can.
- Jon
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'95 SC400 - 18's, '00 front, 6ch dolby, etc..sold
'99 SC300 Turbo - tt block w/ vvti head, sp63 .81 A/R 4" inlet, hks, aem, volk, sp, tt brakes f&r, 6ch dolby, 585rwhp..sold
'91 NSX - nsx-r trans, rm racing, jun, cm, tein, volk, carbing, ww, 6ch dolby, etc..sold
'97 NSX-T 3.2 6spd #298 - nsx-r conversion, volk, comptech, arc, taitec, downforce, cantrell, etc..sold
'09 S5 - 19's, carbon fiber, nav, tech pkg, bang & olufsen..sold
E55 AMG - pano roof, vent seats, nav, keyless go, lighting pkg
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Old 10-26-02, 10:47 AM   #9
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I went to 17" wheels on my SC400 (from the orig 16")

the first set of tires were "low profile" and rode hard, prone to blowouts and looked stupid.

We figured out the correct "rise", "profile" or sidewall height to get back to the original outside tire diameter.

The wheels look great ! (I got Lexus wheels on Ebay) and the handling is noticably better but not harsh.

I think they'd really look good in place of your 15 inchers!
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Old 10-26-02, 03:33 PM   #10
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Yeah, make sure you stay away from those rubberband tires (25-series). When you upsize, check the load rating on the tires too. The thinner your sidewall, the more air pressure you'll need to fill your tires with to ride safely. I'm not talking a lot of extra psi, usually like 2-5 psi more.
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Old 10-29-02, 11:02 AM   #11
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Think twice about the lowering on your car if you want better handling. I was also very skeptical about doing any king of drop, but now that I understand it more and see that lowering your car doesn't do much except decrease body roll/incrase general handling and that annoying "fly forward in your seat when braking" I'm actually thinking of a 1" drop.

Any more and of course ride quality gets worse, more bumpy and you incrase the chances of rattles forming in the interior. If you do lower, make sure your bump stops are in good condition.
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Old 10-29-02, 11:02 AM
 
 
 
 
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