simple performance upgrade: TIRES
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Joined: May 2005
Posts: 141
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simple performance upgrade: TIRES
I am wondering how much of a estamated 1\4 time would improve by just having wider rims and tires..
the car I am looking to upgrade is an SLK55.. I am not sure how wide the rims in teh rear are but the tire size is PRETTY dang small in my experiance.. they are 245\35\18s.. and my guess is that they are 8inch wide rims.. 8.5 at the most!
this car is already quick in the 1\4 at 12.8... some MB test have provin 0-60 in less then 5sec.. BUT I also hear that the most recent car and driver.. or some other hot car mag claims LOW 4's 0-60..
now I am not an expert on tires.. but a guy I ran into with a Z06.. who claimed his car ran 10s (LOL) had 295's on the rear on 18inch rims..
now I am wondering if I had some 10inch wide rims on the SLK55 how much quicker would it do the 1\4 in? do any of you guys have experiance in this feild?
the car I am looking to upgrade is an SLK55.. I am not sure how wide the rims in teh rear are but the tire size is PRETTY dang small in my experiance.. they are 245\35\18s.. and my guess is that they are 8inch wide rims.. 8.5 at the most!
this car is already quick in the 1\4 at 12.8... some MB test have provin 0-60 in less then 5sec.. BUT I also hear that the most recent car and driver.. or some other hot car mag claims LOW 4's 0-60..
now I am not an expert on tires.. but a guy I ran into with a Z06.. who claimed his car ran 10s (LOL) had 295's on the rear on 18inch rims..
now I am wondering if I had some 10inch wide rims on the SLK55 how much quicker would it do the 1\4 in? do any of you guys have experiance in this feild?
Thread Starter
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Joined: May 2005
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wow.. this was pretty amazing.. but I messed around with the slk55 a little last night.. turning the ESP off and on practicing launches.. (all were in Sport mode) and it did not spin the tires in either mode (ESP on\off).. so I guess stock rim and tire combo get enough traction already.
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From: Atlanta, GA
SLK32
Originally Posted by ricky.agrawal
+1 in diamter? Or width.
If width, how does it not change the contact patch?
If width, how does it not change the contact patch?
Now if you are going to change your spedo gearing to compensate you will be able to increase your contact patch without a negative impact.
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Joined: Nov 2004
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From: Central Florida
1980 928S Porsche, 1965 T-Bird Conv., 2006 C55
430,
Could you please explain the above "The reduction of sidewall height will reduce the angles resulting in a contact patch that is wider but shorter with a 0 net change in size"
I was under the impression that what you are doing is decreasing the sidewall height to make up for the ratio of going wider to get the same outside diameter. Isn't the contact patch a combination of outside diameter and width?
Thank you, Bob
Could you please explain the above "The reduction of sidewall height will reduce the angles resulting in a contact patch that is wider but shorter with a 0 net change in size"
I was under the impression that what you are doing is decreasing the sidewall height to make up for the ratio of going wider to get the same outside diameter. Isn't the contact patch a combination of outside diameter and width?
Thank you, Bob
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Joined: Oct 2002
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From: Atlanta, GA
SLK32
You are correct the decreased sidewall height is needed to keep the ratio the same. The problem is the shorter sidewall reduces the amount of tire that comes in contact with the ground. The shorter sidewalls are stiffer and will deform less than a taller sidewall.
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From: Central Florida
1980 928S Porsche, 1965 T-Bird Conv., 2006 C55
430, Please excuse my ignorance, but since the wheel diameter is the same, and the outside tire diameter is the same due to the increased width and ratio, doesn't that mean that the wall height is the same? I can understand what you are saying if you use the same size tire but change the ratio from a 35 to 30 only. This has been bugging me.lol
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From: Central Florida
1980 928S Porsche, 1965 T-Bird Conv., 2006 C55
Thanks mdp c230k. So on a C55, stock is: front 225/40/18 on a 7.5" wheel. Rear is 245/35/18 on a 8.5 wheel. Tire diameter in front is 25.1" and the rear is 24.8".
Now if I keep the front stock and put 265/35/18 on 9.5" wheels that would make the rear diameter 25.3". Does this sound like a good set-up if you are trying to get more traction for off the line starts? Will it cause any adverse trouble with the esp since it would now be reverse diameters with the front being smaller compared to stock fronts being larger in diameter.
Thanks for the help on this, Bob
Now if I keep the front stock and put 265/35/18 on 9.5" wheels that would make the rear diameter 25.3". Does this sound like a good set-up if you are trying to get more traction for off the line starts? Will it cause any adverse trouble with the esp since it would now be reverse diameters with the front being smaller compared to stock fronts being larger in diameter.
Thanks for the help on this, Bob
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From: Los Angeles
2002 c230k
Try to keep the rolling diameter as close as possible from front to back for the esp to work the best. The width of the wheel is only important in the fact that a wider rim is heavier and as a result it is harder for the engine to spin it. That means slower. The other problem can be unsprung weight, more is bad for handling. A wider tire will have more side-to-side grip on a smooth surface but might suffer over bumps due to the unsprung weight. Tires with higher aspect ratios (like 60s or 65s) will have a longer, front to back, contact patch making them better for straight line acceleration but will suffer around corners due to flexxing sidewalls. There is a happy medium that must be found between the two. The best money spent on rims is not on the largest diameter but on the lightest weight on a rim that is 18" or less. I like go more than show. 
