I know you aren't supposed to used a spare tire that is smaller on a car with an lsd, but what about both wheels? Say I have an lsd equipped rear wheel drive car with 20 inch factory wheels. Would it cause any harm changing all the wheels to 18s? If all the wheels are downsized it should not cause damage correct?

 

what car are you thinking of doing this on?

just asking if it's a hypothetical question? or you're really planning on downsizing?

 

because, if it's hypothetical, we could use the TL as an example, as the 6MT TL has an LSD

 

and there are SOOOO many different types of LSD's

 

My cousin got a new charger this year and it has the 6.4L with the lsd. He has a set of 18 inch wheels with blizzaks on them he used on his old charger (without an lsd), and we were wondering if it would mess anything up if we put them on his new car.

 

your cousin will be fine moving down to 18's for the winter.
not sure what kind of LSD the charger has, and I'm too lazy too look it up.

but if all 4 corners are the same diameter, i cant see it hurting it.
well, if the Blizzak tires dont match OEM's specs, the speedometer might be off a few miles per hour

 

Oh, it's that type of differential. Thought you meant differential equations.

 

As the crab has said, I think the issue is more with differing circumference of the 2 tires, not necessarily the diameter of the actual wheels.

I think the issue is in having the 2 wheels turning at different speeds, if you have different size tires on it.

 

I don't see an issue with putting different sized wheels with a car that has LSD as long as they match on both hubs?

Not relevant to your question, but I got a flat on the rear driverside and had to nurse my S2000 (LSD equipped) on the itty bitty spare paired with a 255 sized tire on the passenger side.

Car drove all sorts of funny, would not do it again unless I had to

 

It'll be fine. Charger owners do this all the time. The only issue he'll face is the speedometer and odometer will be off if the 18" tires are shorter or taller in overall height than the 20" tires.

 

Yes, it will be fine.

If you have a non-fullsize spare, and you get a flat on the rear of an LSD-equipped car, then swap a front wheel to the back, and put the spare in front.

 

Noted.

I'm not teh smartz, I blame public schools

 

Thanks guys I will let him know. He may have scraping trouble though with smaller wheels, he already ripped the splash guard off on something.

 

How much smaller are the winter tires compared to the factory size?

 

They must be way smaller if they're ripping slash guards off. Why didn't he go with a tire height similar to the OEM 20s??

 

sounds like he already had the wheels and tires and didnt bother changing tires....
wanted a quick solution, instead of doing it right

 

Changing size is fine as long as they are the same diameter on both sides. For winters most people do a -1 or -2 change. His 20's are probably low profile, so when he goes to an 18'' rim he'll want to add an inch or two of sidewall, this will help maintain ride height, speedometer accuracy and offer some additional suspension cushion for those nasty winter pot holes.