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Dr. JDM
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Discussion Starter · #1 ·
1) If you have a LSD and you run two different size wheels on each side, what happens? Is there extra wear on the LSD?

2) If you have the tire rotating against the direction of the arrow, what are the consequences?
 

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I believe you have extra wear on the tire not the lsd. I've heard people say that running a directional in the wrong direction leads to premature or uneven tire wear but I'm pretty sure directionals are made that way more as a way to push water to the outside of the tread in rain. Running it backwards could cause the car to hydroplane easier. Someone correct me if I'm wrong.
 

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Dr. JDM
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Discussion Starter · #4 ·
so if you have a spare tire on your rear wheel, it's not good? what exactly happens?
 

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so if you have a spare tire on your rear wheel, it's not good? what exactly happens?
The tires rotate at different rates since they're different sizes, this kills the limited slip part of the diff fairly quickly as, far as it can tell, your wheels are constantly slipping.

Assuming your wheels are all 4 the same size if you blow a rear and your spare is NOT the same overall diameter as the other rear you should swap a front wheel to the back and put the spare on the front.
 

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Dr. JDM
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Discussion Starter · #6 ·
problem is, the full size spare won't fit in the front due to the bbk. and the rotation would be wrong for the tires. so i've been running the spare for a week now in the back, 17" OEM wheel with 18x8 225/40/18 on the other side. how can i tell if my lsd is shot? crap
 

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Chado, Wheel size is a moot point. It all boils down to the actual circumference of the tire. You can have 16" wheel on one side and 18 on the other but as long as the tires have the same circumference no ill effects will be had. NOW If you do not have tires that are very super close in circumference you can (at an extreme difference) boil the diff fluid and cause failure with in the diff as parts seize or break apart.

With the directional comment, as far as I have ever gathered, it would just be a tire wear/wet weather performance issue. Day to day dry driving shouldnt much really be affected though.
 

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Dr. JDM
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Discussion Starter · #8 ·
^^ that's what i was thinking, the taller tire on the spare wheel kinda makes up for the smaller rim. just haven't measured it but it seems close. oh well..

the spare is going backwards rotation wise anyway, after i checked yesterday while putting more air into it
 

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225/40/18 vs 215/45/17 = Diameter = 25. 1" vs 24.6"
= 1.9% difference

Tire size calculator

This isn't a drastic difference but I wouldn't run this for any longer than is absolutely necessary.

The tire rotating in the opposite direction will cause you to hydroplane like crazy so avoid the wet.
 
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Dr. JDM
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Discussion Starter · #10 ·
225/40/18 vs 215/45/17 = Diameter = 25. 1" vs 24.6"
= 1.9% difference

Tire size calculator

This isn't a drastic difference but I wouldn't run this for any longer than is absolutely necessary.

The tire rotating in the opposite direction will cause you to hydroplane like crazy so avoid the wet.
thanks. new wheels should be in within the next 2 weeks. that means a little over a month on this setup. haven't smelled anything burn up..
 
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Different tread pattern can cause your car to not drive straight. Like wise, if you have all four same tires, but their directional is backward, you will drive like you need an alignment.
 
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