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Dodge Challenger RT Classic
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Discussion Starter · #1 ·
Hi folks,

Sorry if this is a repost, I wasn't really sure how to word the search for this question. I want to know if there is a change in the over all diameter of the wheel when alternating between 20''s and 18''s. If the over all size of the wheel doesn't change then I don't have to worry about affecting the gear ratio or speedo. Correct? My goal is to ride on the 18''s for winter and the 20''s for summer. Suggestions? I wanna pick up an RT classic in Blackberry pearl and trade in the bimmer. Help me go American!
 

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2009 Challenger R/T
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It'll depend on the tire size, but if I remember correctly, I believe the 18s with 235/55/18s have a diameter of 28.2 or somethign similar to that while the 20s with 245/45/20s have a diameter of 28.7. So when going down to an 18" wheel your speedometer will be reading higher than what your actually going (and putting more miles on your car than your actually traveling).
 

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The key to keeping your speedo accurate is to maintain the overall diameter of your original wheel/tire combo. You can play around with the tire width and the aspect ratio, using the following tire sizing tool, to come close to what you need.

For example these combinations are close:

245/45/20= 28.68 dia., 725.2 revs per mi.
255/50/18= 28.03 dia., 742 revs per mi.
245/60/18= 29.33 dia., 703.4 revs per mi.

Tire Size Calculator - tire & wheel plus sizing
 

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Hi folks,

Sorry if this is a repost, I wasn't really sure how to word the search for this question. I want to know if there is a change in the over all diameter of the wheel when alternating between 20''s and 18''s. If the over all size of the wheel doesn't change then I don't have to worry about affecting the gear ratio or speedo. Correct? My goal is to ride on the 18''s for winter and the 20''s for summer. Suggestions? I wanna pick up an RT classic in Blackberry pearl and trade in the bimmer. Help me go American!

I am not an expert on this, but to say when they upgraded the wheel pkg on the classic, you may get different brakes and rotors. Not sure.
If they are, then the 18" may not fit.

If you are only changing tires for winter, why not stay with a 20" rim with snow tires already mounted. (guess I am reading between the lines)

Just more things to consider.
 

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2009 Challenger R/T
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2,991 Posts
You can fit 17" rims on Brembos, so he won't have a problem putting 18s on the R/Ts brakes
 

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Premium Member
Dodge Challenger RT Classic
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46 Posts
Discussion Starter · #6 ·
I've heard that 20'' snows are really not the way to go, and Tire Rack offers limited to no selection at all and what they might offer doesn't get good ratings. Has anybody run with 20'' snows on a new Chally? can you recommend a good brand? I really wanna get the super track pack, but I also need good snow tires. If I need to, is there an easy way to configure the system to compensate for smaller wheels (adjust the speedo and such)?
 
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