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Discussion Starter · #1 ·
I did some searches through past posts but couldn't find the definitive answer. What is the widest rear tire that can safely fit on the stock SRT-8 wheels (car is a 2009 SRT)? It looked like 295/40/20 may have worked for a few people but wanted to check.

Would like to keep the 245's up front and go with wider rear tires than the 255's on there now. Anyone done this and have any feedback? Did it affect ride quality dramatically? Would you recommend doing it or should I just stick with the OEM 255 size for the rears? Thanks.
 

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The SRT Engineers have stated that 295 on the rear is the widest you can use. On the front you can go 275.
 

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I did some searches through past posts but couldn't find the definitive answer. What is the widest rear tire that can safely fit on the stock SRT-8 wheels (car is a 2009 SRT)? It looked like 295/40/20 may have worked for a few people but wanted to check.

Would like to keep the 245's up front and go with wider rear tires than the 255's on there now. Anyone done this and have any feedback? Did it affect ride quality dramatically? Would you recommend doing it or should I just stick with the OEM 255 size for the rears? Thanks.
And there are plenty of folks that have 305 and 315s on stock rims with no issues to date
I run a pair of Nitto NT05R 315/35 on my factory 20" SRT8 wheels. I also have a friend with a pair of the same and his car has been lowered one inch. Neither of us have any issues and that tire made a big difference for me.
 

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It is not advisable to run anything wider than a 275 on a 9" rim. Although you can squeeze a larger tire on a 9" rim, it will not perform properly. A 10" wide wheel is required for anything 295 or wider.

Correct rim width ensures flex at the designed flex point in a tire sidewall for optimum tire performance. If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, as well as cupping, which reduces tire life and could result in failure.

Also, the SRT engineers have stated that they do not recommend anything wider than a 245 tire in the front in order to avoid front-end clerarance problems during hard cornering. When my tires need replacement, I will go for the staggered "retro look" with 245s on the front and 275s on the rear.

If you mount 295 or wider tires, I would buy mud flaps because you will get a lot more rear fender paint chips.
 

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Discussion Starter · #6 ·
Thanks for the replies. For any of you running the wider tires - how do they feel compared to the stock 255's? Better ride, worse ride? Any noticeable difference in handling or traction/launch? I have a set of Kumho 305's on the rear of my Cobra and they've always felt really good and ride nicely.

Any recommendations on tires? Looks like tirerack.com has some BF Goodrich in the sizes I need for a good price. Tread rating on the BFG's is not much better than the original Goodyears though and those have lasted all of 13k miles. Thanks again.
 

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I don't think I have compromised the ride any with the 315s. As far as launch goes, yes, much better. And judging from the tracks, I am getting a great contact patch. There isn't anything wrong with the handling either. I'm not doing any road racing so I can't answer to anything but going straight. I can tell you that the back end doesn't get squirrelly nearly as much as it used to.
 

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Discussion Starter · #8 ·
That's good to hear. Mine is definitely squirrelly especially when accelerating out of a turn from slow speeds. Thanks again for the info. Still trying to decide which tires to go with.
 

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what is the width of the 2011 SRT rear wheels? for some reason I thought they are 10" wide wheels.
 

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One thing to consider when going wider is tire buldge and how it could effect your car's handling. Each tire manufacturer makes their tires a bit different from the other... sidewall thickness being one area to investigate.

If you have some tire buldge over the lip of the wheel and your sidewall isn't extra thick, you'll end up with "roll" when cornering... a slight-to-very noticeable feeling of being on a boat, so to speak.

This can lead to tire failure, so choose your poison carefully.

275's on a stock SRT8 wheel are just about ideal. You still maintain traction with excellent contact AND there's ZERO concern about the buldge.
 

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The SRT Engineers have stated that 295 on the rear is the widest you can use. On the front you can go 275.
Just letting you know that I have Continetals 325s on my 09 SRT and I couldn't say a negative thing about them and If you sell me your wheels I plan to put my tires on them!

I also had a pair of 18" centerlines wheels made and have a set of 325 M&H DRs
Tires mounted on them. Gives me about one half inch clearence both inner and outer and with my Auto and a 392 Rearend I have no problem getting Traction.
Now you and Hemi Sam are the only ones that I have told ..
So far no broken axels, when I do break one I plan to go with stranges 9in Ford Rear-end, At that time I will have some more Mopar Parts for sale.:bigthumb:
 

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Correction on Tire size

Just letting you know that I have Continetals 325s on my 09 SRT and I couldn't say a negative thing about them and If you sell me your wheels I plan to put my tires on them!

I also had a pair of 18" centerlines wheels made and have a set of 325 M&H DRs
Tires mounted on them. Gives me about one half inch clearence both inner and outer and with my Auto and a 392 Rearend I have no problem getting Traction.
Now you and Hemi Sam are the only ones that I have told ..
So far no broken axels, when I do break one I plan to go with stranges 9in Ford Rear-end, At that time I will have some more Mopar Parts for sale.:bigthumb:
I stand to be corrected. I have 295s on the car and 325s:sleep: on my drag wheels.. Sorry about that!
 

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The SRT Engineers have stated that 295 on the rear is the widest you can use. On the front you can go 275.
I asked this question at one of the SRT Chat Sessions. The engineers stated that a 245 is the max for the front in order to avoid front suspension clearance problems during hard cornering. I don't recall them saying anything different on other sessions.
 

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I asked this question at one of the SRT Chat Sessions. The engineers stated that a 245 is the max for the front in order to avoid front suspension clearance problems during hard cornering. I don't recall them saying anything different on other sessions.
I don't doubt the SRT boys know their stuff, but my 275s up front have had not problems what so ever. I'd like to think I corner fairly hard!:browsmiley:
 

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Discussion Starter · #16 ·
One other question on this - I noticed the stock tires on my car have a 45 sidewall height (255/45/20) but a number of people have mentioned running a 40 sidewall height such as a 285/40/20. Is there any reason to choose a 40 over a 45 sidewall height? Should I stick with the stock height? I need to pull the trigger in the next day or two since my front tires are worn down dangerously and just want to make sure I buy the right tires. Thanks again.
 

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One other question on this - I noticed the stock tires on my car have a 45 sidewall height (255/45/20) but a number of people have mentioned running a 40 sidewall height such as a 285/40/20. Is there any reason to choose a 40 over a 45 sidewall height? Should I stick with the stock height? I need to pull the trigger in the next day or two since my front tires are worn down dangerously and just want to make sure I buy the right tires. Thanks again.
That is the aspect ratio (I think that's what it called). From my understanding it's a percent in which you multiply the width (1st number) by to get your true side wall height. Which is why 245/45/20s are pretty much the same height as 275/40/20 or 315/35/20s
 

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Go here and calculate the tire size you want to use vs. what you have on the car as a stock tire. Make sure you stay within the Speedo percentage difference. You should stay under 2%.

Tire Size Calculator - tire & wheel plus sizing
 

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Discussion Starter · #19 ·
Thanks. I did that and it looks like the stock combo has a circumference difference of 1.12 inches. The difference between 245/45/20 up front and 275/40/20 in rear is 0.06" and the difference between 245/45/20 and 285/40/20 is 0.93". The 285/40 in the rear with the 245/45 up front seems to be the closest to the stock ratio and is probably the widest I'm willing to go with the stock rims although I know technically they can take a wider tire. Looks like I'm going to go with the 245/45/20 up front and the 285/40/20 in the rear. Thanks for the help.
 

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It is not advisable to run anything wider than a 275 on a 9" rim. Although you can squeeze a larger tire on a 9" rim, it will not perform properly. A 10" wide wheel is required for anything 295 or wider.

Correct rim width ensures flex at the designed flex point in a tire sidewall for optimum tire performance. If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, as well as cupping, which reduces tire life and could result in failure.

Also, the SRT engineers have stated that they do not recommend anything wider than a 245 tire in the front in order to avoid front-end clerarance problems during hard cornering. When my tires need replacement, I will go for the staggered "retro look" with 245s on the front and 275s on the rear.

If you mount 295 or wider tires, I would buy mud flaps because you will get a lot more rear fender paint chips.
Cuda-

I agree you and the SRT boys are technically correct. That being said, I have no front clearance issues, no cupping issues, and no rear fender chips one year in.

This is another one of those things - ala the Mustang Cobra with the wrong bolt pattern wheels being used for drag radial usage - where technically you shouldn't do it, but it has worked for many with no ill effects.

To your point, when you deviate from the spec, you take your chances.

YMMV
 
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