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Discussion Starter #1
I would like to run these up front on an SRT8. I know they will fit but I am wondering about alignment and ABS function. The car is expecting the front tires to roll faster than the rears and is the car going to care or even notice the difference if they are the same as the rears?
Also are the stock alignment specs suitable for the slightly wider tire?

Any thoughts?
 

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You should always try to keep the rolling radius the same front to rear. Our cars are equipped with EBD (electronic brake proportioning front to rear thru the ABS system). This system can detect a difference of as little as 2% front to rear. Pretty easy to calculate rolling radius (width x aspect ratio). The car is not expecting the front to roll different than the rears (SRT's come with both 245 in the rear and 255's depending on the tire pkg and this difference is very small)?? The EBS system is reasonably adaptable but you should try to stay with the same rolling radius front to rear. I am sure there are guys on here that will say they have changed this with no problem and I am sure they have not had issues but if you want optimal performance from your system you should try to stay with these guidelines.

I know the company really well that develops and manufactures the ESP systems for our cars.:)
 

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Discussion Starter #3 (Edited)
The car currently has factory-installed staggered tires so I assume it is currently expecting the fronts rolling faster than the rears and what I want to end up with is the same all the way around.

According to GY the 255 tires are 719 revs per mile and the 245 tires are 729 revs per mile. That would be a difference of ~1.4%
 

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I would be more concerned about front suspension interference. The SRT engineers have said that under hard cornering, a 255/45/20 tire on the front will rub. When my tires wear out, I intend to keep 245s on the front, but go with 275s on the rear for that "old school" staggered look.
 

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You're talking about less than 1/2" more in width for the 255s - so you shouldn't have any issues. I don't think one 20" tire would roll any faster or slower than another 20" tire - 18s would roll faster (more revolutions per MPH compared to a larger diameter tire). As long as your don't have a larger diameter out back you should be fine with both fit and function. You'll obviously want to have the 255s balanced. Other than balancing the 255s, it should be a direct swap.
 

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You're talking about less than 1/2" more in width for the 255s - so you shouldn't have any issues. I don't think one 20" tire would roll any faster or slower than another 20" tire - 18s would roll faster (more revolutions per MPH compared to a larger diameter tire). As long as your don't have a larger diameter out back you should be fine with both fit and function. You'll obviously want to have the 255s balanced. Other than balancing the 255s, it should be a direct swap.
Really, all 20" tires roll the same. Sorry that is absolutely not true, there are huge differences in rolling radius between different size 20" tires with different widths and aspect ratios. As far as 255/45's I have them on the front of my car which is lowered and they are not close to hitting anything.
 

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The car currently has factory-installed staggered tires so I assume it is currently expecting the fronts rolling faster than the rears and what I want to end up with is the same all the way around.

According to GY the 255 tires are 719 revs per mile and the 245 tires are 729 revs per mile. That would be a difference of ~1.4%
That is what I said in my first post. You can get an SRT with 245's all around or 245's on the front and 255's on the rear from the factory. ESP software is the same, system can adapt to small changes. So since it comes with 245's front and rear from the factory I think that answers your first question.
 
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