I just purchassed a set of RT Wheels with tires. My current tires are P215/65R17 and the new tires are P255/55R18. I'm thinking the overall diameter is larger so will probably slow my speedo down. How can I get it recalibrated?

 

There are 2 ways, one and least recommended is, there should be a shop in your area that does that sort of thing, I know in Calgary, there is one, and they do that, but I have never checked the pricing. Second and best but it is quite expensive $400+, is buy a Superchips programmer. It lets you alter the wheel sizes as well as just about everything else with the car. After every mod you do, you can reprogram it into the superchips, and it will help optimize your car. Thats the way I would go.

 

The only problem is Superchips doesn't make a programmer for the Magnum SXT with the 3.5L engine.

And while I have someones attention. I noticed that the front tires are only about 1/4 from the bottom of the top balljoint stud. This looks too close to me. Will the tire grow at high speed enough to touch and cut the tires? My Magnum is a '06 SRT and came with 17" wheels. These are the Optional wheel that were available. The tires are huge compaired to what was on it. The guy I got them from has a '05 Magnum RT and ran them for 10,000 miles with no problems. Was the frame/front suspension different on his Magnum?

 

well Danny I really cant help you there, I have an RT as well, I cant see they would make that much of a difference. Check and see the tire profile it should be a bit lower than the tires on the 17s. If they are the same, then that would certainly affect the height as the rims is bigger. Maybe post another thread so someone more knowledgeable can help you here.

 

I got the RT wheels and tires and put them on. They work fine but are about 1 1/2 inch taller. I took it to the dealer where I purchassed the SXT and they reset the speedo but stated they only could set it for P235 tires. I didn't question them but I'm thinking if they set it for P235/65R18 that should be pretty close to a P255/55R18. Not sure what the difference between the RT Magnum and the SXT are, other than the engine but it seems there is some limitations on what can be done or what is available for it.

I would think the body is the same but the front upper ball joint stud is only 1/4" from the tire. I was told by the guy that sold me the wheels and tires that he went to P295/55R20 and they were a little taller. I believe they would rub on my car.

Can anyone verify any differece in the 2006 Magnum SXT and a 2005 Magnum RT?

 

Danny, I have 255x45x20 on the front of my R/T and have the same 1/4" clearence you have. I may be way off but with street tires I do not think there is any height growth at our driving speeds. My front tires are the same height as 255x55x18 and have had the Magnum to 120 without any problems. You are about 3.5% slower at 60, which means if you are running 60 mph you are really doing 62.2. The dealer should be able to put the stock R/T size in and you would only be 1.5% off. So at 60 you would be doing 60.9.

 

Do you guys know if recalibrating the speedo at the dealer will void the warranty?

 

it really shouldnt, as it isnt really doing anything to effect the vehicle itself. it should just be a cpu mod, and if the dealer does it, it should be warrantied for the work they did.