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Discussion Starter · #1 ·
Hello, I ask this question to this website, because I hea that BMW owners know the most about rims and tires so I would like feedback


Below I posted a pics of the rims and tires. The first pic is of the 2012 Challenger RT with 245/45/20 Firestone Firehawk GT's. The pic below is of the 2010 Challenger RT with 245/45/20 Eagle F1's. Both rims are 20.8 Chrome Clad (the design changed over the two years, but the size and diameter is the same). As you can see in the second pic, the rim is flush and in the first pic, it is really bulging out...

Any comments on if the tire maybe is stretched farther on the Firestone Firehawks because maybe that tire is not a good choice for the rim and is not seated properly.

thanks,









 

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Discussion Starter · #2 ·
guys can you please lend some help

guys, can you please help me with this question. It seems that on my firestones the lip sticks way out: like it would if someone would use stretched tires and the lip sticks out.


could there be an issue, or is that just the lack of curb guard/rim protector/ bead guard/sidewall
 

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Im not an expert, but i know certain tires tend to have a different shape sidewall for instance one might bulge a little more where as another might have more of a square sidewall. If the tire sizes and rim dimensions are in fact identical then the sidewall shape (because of different tire makes is all i could think of). Hope this helps, if not free :bump:
 

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OP don't confuse width with section width. That "245" measurement is with the tire unmounted and sidewall to sidewall as it sits. Section width is from shoulder to shoulder of the tread pattern. Depending on the relationship between these, as well as other factors like ply materials and numbers, and on top of that slight variations in measurements, 2 "identical sized" tires can look quite different on the same rim.

PS the second one has Eagle RS-A's which are a POS IMO
 

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Discussion Starter · #7 · (Edited)
so it is the tire, and i dont need to buy new brand tires and.or re-mount the tires on the rim for fear of it coming off the bead while cornering?

i already have put about 750 miles like this: would something have happened by now?


here are the actual pics from my car

























thanks tire experts
-tommaso
 

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Ignore Gary's jibberish and listen to what I said. If your wheel is between 7.5 and 9 inches wide you are fine.
 

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Discussion Starter · #11 · (Edited)
Gary did have some giberish....







yeah, the wheel is 20x8.0 and the tires are 245/45/20 like the manual said. So the sizes are good for this car, I was just asking if the person mounted them on the car and balanced them correctly before me since the car originally had 235/55/18's on them with an 18x7.5 rims and were upgraded to the 245/45/20 on the 20x8.0. The original offset was 24 and the bolt pattern is 5x115.
 

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Discussion Starter · #12 ·
thanks guys

so my car has a rim protector, or has no rim protector? I though the rim protector was an extra layer of rubber going around the rim so it sits flush and this will allow damage to happen to the tire and not the rim.

if the wheel was to hit a curb, wouldnt it be worse for the rim as it will get scracted since it is sticking out. What is priority when scuffing: protect the rim or tire?
 

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OP don't confuse width with section width. That "245" measurement is with the tire unmounted and sidewall to sidewall as it sits. Section width is from shoulder to shoulder of the tread pattern. Depending on the relationship between these, as well as other factors like ply materials and numbers, and on top of that slight variations in measurements, 2 "identical sized" tires can look quite different on the same rim.

PS the second one has Eagle RS-A's which are a POS IMO
Some of what you stated is incorrect.

The "245" is the "section width". This is shorthand for cross section width, meaning the overall width of the tire from sidewall to sidewall, not counting non-structural protrusions.

The shoulder to shoulder width you're talking about is the tread width.

In addition, tires are not measured unmounted. They're measured mounted on a "measuring rim" of a specified width. The measuring rim width is almost always stated on the tire's spec sheet. A general rule of thumb is that adding or subtracting 1/2" of wheel width will increase or decrease the actual mounted section width of a tire by about 2/10".

I've been out of the business for a bit, but it used to be that DOT required a tire to be within 3% of it's branded size when mounted on a measuring rim.

Read here for good info: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=200

For reference, according to the tech sheets posted on Tire Rack's website:

245/45ZR20 Eagle F1 Supercar has a section width of 9.6" on an 8" measuring rim, a tread width of 8.4", and overall diameter of 28.7".

Some of the specs for the Firehawk GT are blank, but looking at the specs for other tires in the same size, the section widths stay pretty consistent, the primary variance is in the tread width.

Hope this helps.

:thumbsup:
 

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"Proof" of tire sidewalls shape being different brand to brand:

Continental Sport Contact 3 225/45 17

Nokian Z G2 225/45 17


(on 7x17" wheels)
 
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