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Discussion Starter #1 (Edited)
I'm thinking about throwing some 275/40/20s on the back of my R/T. Would this be a noticeable traction improvement compared to the stock size 245/45/20? Everything I've read so far says 275's are no problem on the stock chrome clads. I'm just really wondering if the $400 two new rear tires are going to cost me is worth it? Or will the traction improvement be so small that I should keep my $400? I'm looking at the Firestone firehawks so they somewhat match the stock Firestone's on the front. Tirerack reviews say dry traction is pretty good on the Firestone's and they are only like $173 a tire in 275/40 size. Anyone have any experience or thoughts?

The 5,000 mile treadlife of some of the better dry traction tires won't cut it for me. I need tires that have decent dry traction and still last 35,000-40,000 miles at least.

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Traction will improve slightly. All depends on what tire you get. I have went through two sets of nittos and they are far superior than anything lower in class. If you don't do burn outs and dift every corner than the nt05 or 555 is a long lasting tire. Deff not 40k miles though. Are you after launch traction or corning or longevity?
 

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depends not on width but on tire compound; the friction coefficient will be increase but with that the weight per wheel will spread over a greater surface (width) thus the pounds per square inch of weight will be less; hence why the rubber compound is so important;

as another member also explained, the fact you have more weight per square inch makes the tire heat up more quickly which is in autocross a desired effect but not so much on road course; on the strip you are looking for maximum stickiness in a few seconds so you can hook right in the green light leave the camaro behind; road course tires can be a lot wider but then you are also increasing un sprung weight and rotational mass

for the street is the frequency at which you are willing to replace your tires, how many wheel sets you have, the region where you live and what kind of weather you have year round as well as driving style

you can get more horsepower by keeping the weight down with a 245 and choose to have a 200 rubber rating such as a summer performance; that will not carry you through 20000 miles but your tires will get sticky and will give the assurance in street cornering while keeping the horse power

if you like the look of a 275 on a 9" then go for it, but you will be slightly less efficient as more tire mass will rob horse power and 275 on a 9" is not optimum for cornering; it's good but does not yield the results; i tried that, so i know

my street 275, 315 is for looks and just for that;

after learning and experiencing, for the light track/street use it is back to 245 (9") front, and 275 rear on 10.5 inch rim with sticky compound 200/300

for the track optimum set up, 10.5 on 18's with 295 slicks Hoosier all around, that should do the trick.

hope this helps

ODP
 

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Hmmm. Not much out there with both of those worlds. Maybe someone else can chime in. Its alot about rubber compound. A softer tire can stick to the ground better but obviously wont last as long. Id out a search on ebay for 275 40 20 and see what pops up them search each one for reviews. Thats what I do. So my recommendation stays the same as 05 or NT555
 

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The 245/45s you remove from the rear can eventually be placed in the front. Therefore it's not really a waste of $400 to upgrade to the 275/40s for the rear. I say go for it. Our Challengers really should have come with a 275/40 rear from the factory IMO. The Camaros do, and they're a smaller car comparatively.
 

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Discussion Starter #8
That's was exactly what I planned to do. I agree with you those 245s just look so skinny from behind, 275s should have been on there from the factory from an appearance stand point alone much less performance.

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R/T's come with 8"rim not recomended for 275/40/20...minimum rim is 9" on most....SRT rims are 9"
 

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Not much of a difference!

IMO, these is very little difference, if any between the two sizes but what did amaze me when I went to the SRT Track Experience, was just how good the 245s were I thought that we would be sliding all over the place but the 245's kept the cars glued to the track (with traction control on) I do know that for the drag strip, the gloves are off, you need alot more traction than a 275 can provide, more tire required for damn sure.
 

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275 width tires offer 1.2 more inches of contact area per tire ... so 2.4" total more contact width than a 245 - so it's gotta give a bit more grip.

...now mounting them on an 8" width wheel may "curve" the outer edges of the tire face in a bit to accommodate for being sucked in by the narrower rim...so maybe 2" more total width?
 

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Right ... once you break them loose...but you've got 2+ inches trying to prevent that from happening with 275's on the rear !
 

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They can "try" all they can..........

Lets not make this any harder than it has to be, alright!
What an SRT needs especially on a 6 speed and for racing, is not the difference between a 245 vs 275 you'll need even more that street radials, you need some "good American slicks" end of story otherwise, you'll just be "spinning your wheels" LOL:icon_wink:

So what was the question?????
 

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Lol - I give !

...but the OP wanted to know if you could notice a traction difference. I'm only surmising that you can drop the clutch at "x" rpms more without spinning them off the line with 2+ inches more surface contact width.

What "x" is - I don't know. could be 100 rpms higher - could be 500 higher. I really don't know. plus it is dependent on so many other factors. Tire compound, pressure, temperature etc...
 

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I too, give!

I know what you mean too! and my last word on this is: 2 inches on a street tire does not mean squat! I was so pissed off when I decided to buy some "bigger" rear tires for my new Challenger while I was changed the wheels and I thought that the 275's were pretty wide, but when I got home I realized that my 2007 300 with a whopping 250 HP, had the 275 all around.....boy was I disapointed .
 

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I gotcha! To the OP - we don't know!

Buy them and do some formal testing for us!
 

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Wider tires = more grip.

To what degree? That is debatable, however it's certainly some.

If not, we should all just mount the narrowest rubber available and be done with it lol.
 

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My hoosier SLICKS wont stick to the asphalt on the street. You need rubber to rubber contact with a soft compound to get the full traction and still then you can break loose. Js
 

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When I replaced the rears with Firestone Indy500s (275/40) on the rear with 9" wheels traction gains were very noticeable. Keep in mind these are summer tires and very soft. Not good for cold climates. I use to spin the OEM tires easy, now it takes work to spin them!

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