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Old 08-05-2012, 10:53 PM   #1 (permalink)
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Using Different Rim/Tire Size to Alter Ride Height

This is a bit of a strange idea, and may waste a thread, but I am curious about using different sized tires for a FR vehicle.

If I put 16, or 17s on my front axle, maybe even LRR, would this have any benefit other than from being LRRs? 18 on the rear now.

I would think less air underneath, should be improved downforce, but do any more experience individuals have any ideas? I often think about it. Any lower and I think my chin spoiler will scrape, as I now must back into most curbed spots, but that is a small price to pay.

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Old 08-05-2012, 11:20 PM   #2 (permalink)
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Excuse the ignorance but what is a "FR vehicle"?

Smaller wheels/tires will lower the vehicle but will also lower the effective gear ratio if you make the drive wheels smaller.

If the wheels are 1" smaller in diameter your vehicle will drop 1/2"

Smaller lighter wheels have less inertia and will accelerate quicker.

Make sure the new rims clear the brakes and the tires can handle the weight of the vehicle.
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Old 08-06-2012, 12:41 AM   #3 (permalink)
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I know on my infiniti I have to run the same size all around. there are sensors that can tell the difference.
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Old 08-06-2012, 01:36 AM   #4 (permalink)
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measured the gaps between the inside of the wheels and brake calipers?
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Old 08-06-2012, 07:08 AM   #5 (permalink)
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You want to be careful not to use tires with less load carrying capacity than originally came on the vehicle. That's directionally towards a less safe condition - the increased risk of a tire failure.

That pretty much eliminates using a smaller diameter.
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Old 08-06-2012, 08:08 AM   #6 (permalink)
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Quote:
Originally Posted by 2000mc View Post
measured the gaps between the inside of the wheels and brake calipers?
I know they do fit, I can definitely go down to 15s, and I have the stock 17s laying in the garage, I am just trying to see of there would be any added aero benefit. I don't know too much about the technicl aspects.

Quote:
Originally Posted by CapriRacer View Post
You want to be careful not to use tires with less load carrying capacity than originally came on the vehicle. That's directionally towards a less safe condition - the increased risk of a tire failure.

That pretty much eliminates using a smaller diameter.
thank you for the advice, I try to maintain safety. I will only use appropriate tires, but will the two different sizes make a difference?

Mcrews- I thought you had a 45x, and then that would be important, but just for FR (front rear, front engine rear wheel drive), I wouldn't think it would matter. But then again, in a luxury vehicle, you probably have more tech items than most of us. I heard even your back tires help steer...she is a beautiful vehicle.

S-FR is front engine rear wheel. MR is mid engine, rear wheel, FF front front, AWD is all wheel, 4x4 is Usually FR with optional AWD, RR is 1960s Beetle and 2013 911 lol some are less common than others, my apologies.

I am stock on 17s, switched to 18s, and now thinking about what dropping the fromt end .5 inches will do. As long as the sensors are okay with it, what else may come into play?
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Old 08-06-2012, 09:36 AM   #7 (permalink)
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so the really question is about lowering .......and the best way to do it.
Idid lower my front end w/ spring compressors and believe there was a small gain in mpg.
The was a popular mechanics article a while back the showed that a lowered front might reduce drag.
The draw back was that I did not align the front end and ended up cupping my tires.

My understanding (from a thread here - somewhere-) is that there is an optimal angle. I felt that with my existing slanted nose and IMPUL body kit, that i was able to achieve a desired result.
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Old 08-06-2012, 10:10 AM   #8 (permalink)
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I can't think of any real safety problems with dropping the front and not the rear, but if you've got ABS or any sort of traction control then those systems might not be happy with running multiple tire sizes.

Aero-wise, the only way to find out if it helps is to thoroughly examine what you've got now and what you end up with. Dropping the front but not the rear might only increase your frontal area without giving any corresponding benefit. "Downforce" is just drag and is only useful if you corner at such high speeds that your car would fly off the road if your bodywork weren't sucking it to the road. Since you generally can't turn downforce off, that drag is working against you every moment that it isn't required to keep you from flying off the road. You may also need a belly pan and/or side skirts to actually get the effect you want.
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Old 08-06-2012, 06:17 PM   #9 (permalink)
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angle templates

Quote:
Originally Posted by UltArc View Post
This is a bit of a strange idea, and may waste a thread, but I am curious about using different sized tires for a FR vehicle.

If I put 16, or 17s on my front axle, maybe even LRR, would this have any benefit other than from being LRRs? 18 on the rear now.

I would think less air underneath, should be improved downforce, but do any more experience individuals have any ideas? I often think about it. Any lower and I think my chin spoiler will scrape, as I now must back into most curbed spots, but that is a small price to pay.
If you will make two cardboard templates,one at 16-degrees,and 10-degrees,you can use them to predict proper ground clearance.
The 16'er is for sliding in the front of the front tires.If any bodywork touches the template it will be shredded in ground strikes going up driveway ramps.
The 10'er is for the rear of the front tire and both front and back of the rear.If any part of the car touches,they are also vulnerable to ground strikes.
If you can anticipate the lower ride height with the 15" wheel/tire combo and there is no clearance issue,then your good to go.
Active suspension gives us the best of both worlds but tougher to pull off.
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Old 08-07-2012, 04:11 PM   #10 (permalink)
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ThNks for all the help, guys. So now I need to find the optimal height, and see if I can match it, without going into a bad aero zone or safety zone. I guess I didn't need to ask, I should have been able to figure it out myself.

If anyone tries it, let me know, or has any results or ideas, I'd like to hear. When I try it, I will post any results. The soonest it will be is this coming spring. New 18s for the rear, and hopefully new 17s for the front.

Again, thanks for the input everybody

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