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Why larger diameter wheels in rear?

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Old 04-15-2008, 10:25 AM   #1
Dominic Toretto
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Default Why larger diameter wheels in rear?

I guess this is just a general automotive question. I have noticed this for years but never bothered asking, but in sports cars such as the Corvette why don't they come standard with the same diameter wheel in the front? I understand the use for wider wheels in the rear for bigger tires for better traction but what's the deal with the smaller diameter wheel in the front? Why not 18s all around?

-Alex
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Old 04-15-2008, 10:35 AM   #2
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Rotating mass is the biggest killer of HP. The smaller the diameter, the more the weight is centered with the axle; therefore, the weight rotates less. The lighter the wheel/tire and the smaller the diameter, the better translation to HP. Take a look at a dragster.

Speed
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Old 04-15-2008, 11:59 AM   #3
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okay so why not then 17s all around?

-Alex
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Old 04-15-2008, 12:01 PM   #4
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Perhaps it was a cosmetic decision.
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Old 04-15-2008, 12:07 PM   #5
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cosmetic/ better areodynamics with the nose down
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Old 04-15-2008, 12:11 PM   #6
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Perhaps it was a cosmetic decision.
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Old 04-15-2008, 12:49 PM   #7
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Quote:
Originally Posted by AlexSmith View Post
...for bigger tires for better traction...

-Alex
Also ^

HP/aerodynamics/etc related, it is nearly always a compromise of some sort.

Speed
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Old 04-15-2008, 12:57 PM   #8
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Originally Posted by Speeed-Racer View Post
Rotating mass is the biggest killer of HP. The smaller the diameter, the more the weight is centered with the axle; therefore, the weight rotates less. The lighter the wheel/tire and the smaller the diameter, the better translation to HP. Take a look at a dragster.

Speed
I'm by far not an engineer, but out of curiousity wouldn't this only have an effect on the drive wheels??
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Old 04-15-2008, 01:11 PM   #9
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Originally Posted by rcarl View Post
I'm by far not an engineer, but out of curiosity wouldn't this only have an effect on the drive wheels??
[Not that I am an engineer either, but] The mass on the front still has to be overcome by the HP and it still rotates, therefore not just the rears killing it here.

nice, recent thread on the subject

Look for mqqn at post #9 and AU N GEL at post #14 for a deeper explanation.

Speed
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Old 04-15-2008, 01:28 PM   #10
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Here's why. If you take a wider wheel in the rear and pair it with a narrower wheel in the front of the same diameter, the front wheel looks like it's larger diameter than the rear. It's an illusion but it does look like the fronts are bigger. I hate Vettes with same diameter wheels all around. In fact my Charger STR8 suffered from the same problem. I used to have a GTO and everyone was doing same diameter wheels front and back but with deep rims on the back. The fronts always looked bigger. I have attached a picture of my GTO two different diameter wheels and they look like they are the same sizes.

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Old 04-15-2008, 01:31 PM   #11
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I assume, and I wasn't on the design team, that they did that so that they could run a taller tire in the rear and have the same size sidewall.
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Old 04-15-2008, 04:02 PM   #12
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read All Corvettes Are Red. Joe Spielman and John Carafo decided the car looked better with larger rear wheels. Spielman was the boss hog developing the C5. what the larger rears lost in cD and weight made up for in aesthetics.

guys, read the book. it's worth the effort....... you will be surprised

.

.
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Old 04-15-2008, 04:16 PM   #13
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Originally Posted by 10U 99 View Post
read All Corvettes Are Red. Joe Spielman and John Carafo decided the car looked better with larger rear wheels. Spielman was the boss hog developing the C5. what the larger rears lost in cD and weight made up for in aesthetics.

guys, read the book. it's worth the effort....... you will be surprised

.

.
Great read
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Old 04-15-2008, 05:34 PM   #14
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Originally Posted by jak112460 View Post
Here's why. If you take a wider wheel in the rear and pair it with a narrower wheel in the front of the same diameter, the front wheel looks like it's larger diameter than the rear. It's an illusion but it does look like the fronts are bigger. I hate Vettes with same diameter wheels all around. In fact my Charger STR8 suffered from the same problem. I used to have a GTO and everyone was doing same diameter wheels front and back but with deep rims on the back. The fronts always looked bigger. I have attached a picture of my GTO two different diameter wheels and they look like they are the same sizes.
Beck looks way bigger
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Old 04-15-2008, 05:39 PM   #15
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If you look at the wheels specifically on a C5 it's way obvious the fronts are smaller.
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Old 04-15-2008, 08:13 PM   #16
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Originally Posted by Kamil D. View Post
Beck looks way bigger
The beck does not look way bigger. Only wider. LOL
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