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Wheels | Tires | Spacers | Hub -- Sponsored by The Tire Rack Specific topics relating to wheels and tires.


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Old 12-04-2019, 02:25 AM   #29
86MLR
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Give me a narrower tyre with better compound.

I'm at 270hp-280nm running 235 RE003 (Indy 500) on a 8" rim.

I had better grip with a 215 RS4 on the 8".

The Indy 500's are slightly better in the wet than the RS4's, and I got them on sale, BUT, it was an unfortunate compromise which I won't do again.

Next will be 225/45 or maybe 235/45 Hankook RS4, you cannot beat them for a bang for your buck tyre.
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Old 12-04-2019, 09:57 AM   #30
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My personal, subjective experience is:

when you reduce unsprung weight by about 6lb (per corner), the perceived gain in performance (acceleration, ride quality, handling, etc) is slight but noticeable; and

when you increase unsprung weight by about 6lb (per corner), the perceived loss in performance is much bigger and intolerable.

As my wife would say:this is not the car I have known all along.
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Old 12-04-2019, 02:12 PM   #31
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Originally Posted by gtengr View Post
My take is that wheel weight loss is nearly equivalent to static weight loss because the angular acceleration rate is so low compared to the flywheel. Less weight is also easier for the shock to control. As noted earlier, stiffness is also a factor, but at the same time not really an actionable one since wheel stiffness data is not easily obtained.
I have experience designing wheels for motorcycles, designed up a car wheel in CAD and I came up with a factor of 1.25 for effective weight reduction accounting for mass and polar moment of inertia. So wheels that are 6 lb. lighter each, 24 lb. overall, should improve acceleration as if 30 lb. had been lost. I.e., not a detectable difference in acceleration...

Even flywheel mass reduction isn't all that effective as far as outright acceleration goes. Bigger difference is in shifting
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Old 12-04-2019, 03:33 PM   #32
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https://grassrootsmotorsports.com/ar...really-better/

Interesting article. The gist is the lighter the vehicle and the slower the speed the more weight reduction and especially rotational weight reduction makes a bigger difference as the force required to rotate the mass becomes a larger percentage of overall force needed to accelerate, and same goes for lower hp cars, the force needed to rotate the mass becomes a larger percentage of available force output.

So rotational weight reduction on a 2000lbs car with 150hp accelerating from 20-60mph will have a substantially bigger difference then a 4000lbs car with 300hp accelerating from 60-100mph.
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Old 12-04-2019, 05:23 PM   #33
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Wheel rigidity > wheel weight.

Also, lose weight on your tires if you're concerned about weight!

Wheel design can change inertia without changing weight, and inertia is what you're really fighting!
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Old 12-04-2019, 05:47 PM   #34
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Wheel rigidity > wheel weight.
Wheel rigidity is super important and constantly overlooked.

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Old 12-04-2019, 05:59 PM   #35
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Quote:
Originally Posted by CSG Mike View Post
Wheel rigidity > wheel weight.

Also, lose weight on your tires if you're concerned about weight!

Wheel design can change inertia without changing weight, and inertia is what you're really fighting!
Related to that, I'm always blown away by the difference in weight of a full tread tire versus the same tire shaved or worn down.
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Old 12-04-2019, 06:24 PM   #36
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Originally Posted by CSG Mike View Post

Also, lose weight on your tires if you're concerned about weight!
I'm always scratching my head about this. People spend top dollar to buy the lightest wheel (tc105 or whatever it's called) and then slap a great big fat 255 section tire on it. Doesn't that pretty much negate the weight loss and add to rotational inertia?

If they were going to always put a HEAVY tire on it... oh well.
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Last edited by CSG Mike; 12-05-2019 at 02:42 AM.
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Old 12-05-2019, 03:17 AM   #37
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Quote:
Originally Posted by ZDan View Post
I have experience designing wheels for motorcycles, designed up a car wheel in CAD and I came up with a factor of 1.25 for effective weight reduction accounting for mass and polar moment of inertia. So wheels that are 6 lb. lighter each, 24 lb. overall, should improve acceleration as if 30 lb. had been lost. I.e., not a detectable difference in acceleration...
I arrived at a smaller effect. I calculated the hp required to accelerate a stock wheel/tire (41 lbs, all conservatively assumed to be in the tire) in 1st gear to be less than 3 hp (all 4 corners included). The difference with 35 lbs wheel/tire at each corner is ~0.35 hp total. Using the old 10 hp = 100 lbs, 0.35 hp is about 3.5 lbs, which equates to 0.875 lbs per corner, or a factor of 1.15. And that maximum effect is only in 1st gear using favorable assumptions. The effect is less in the taller gears due to the slower acceleration.


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Wheel rigidity is super important and constantly overlooked.

- Andrew
I think it's overlooked because the data is mostly unavailable.
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Old 12-05-2019, 03:32 PM   #38
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Originally Posted by Leonardo View Post
18x10 527F XXR are 20.2 lbs each. They have a 5x100 (only) bolt pattern and are +40 offset.

+1 Konigs...

I currently have 18x9 Konig oversteer wheels that weigh almost exactly the same.

I would NEVER consider 29lbs wheels. For our cars. (got them on my truck, lol)
the xxr 527F was actually a really good suggestion(if it wasnt apparent enough that i want gold 10 spokes). its light, and at 18x10+25, its not far off what im aiming for: a 18x10.5+20. however, for the pricepoint of 1500, thats enkei money
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