16 vs 17 track/street wheels
09-04-2011, 07:20 AM
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16 vs 17 track/street wheels
I want to make a set of street/track wheels using R888s tires and I have 2 opportunities to start from:
- Design 92 original wheels (6x16 front and 8x16 rear)
- Mille Miglia Cup1 (7,5x17 front and 9x17 rear)
Design 92s are much lighter (about 3 kg each) but they can receive thinner tires with taller side-walls. (205/55 front and 225/50 rear).
Cup1s can provide more rubber (225/45 front and 255/40 rear) and more precision.
The tires difference will also add a considerable difference in unsprung mass...
Given the R888s have pretty stiff side-walls, would you go the weight route, or would you give more importance to the quantity of rubber and flex?
Ciao
- Design 92 original wheels (6x16 front and 8x16 rear)
- Mille Miglia Cup1 (7,5x17 front and 9x17 rear)
Design 92s are much lighter (about 3 kg each) but they can receive thinner tires with taller side-walls. (205/55 front and 225/50 rear).
Cup1s can provide more rubber (225/45 front and 255/40 rear) and more precision.
The tires difference will also add a considerable difference in unsprung mass...
Given the R888s have pretty stiff side-walls, would you go the weight route, or would you give more importance to the quantity of rubber and flex?
Ciao
Last edited by anto1150; 09-04-2011 at 02:07 PM. Reason: route instead of way
09-04-2011, 08:49 AM
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Caro Anto:
All 964-993s in our country Time trials competitions use 17 wheels and tires, I am not an expert but I think the width available plus the less flexible sides make them the better choices for the double duty, take note that getting good tires for our cars in 16 sizes is getting harder every year
All 964-993s in our country Time trials competitions use 17 wheels and tires, I am not an expert but I think the width available plus the less flexible sides make them the better choices for the double duty, take note that getting good tires for our cars in 16 sizes is getting harder every year
09-04-2011, 11:52 AM
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09-04-2011, 12:31 PM
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Earlydays,
This is interesting! Though I hate understeer and I would take some rubber off the back...
245 rears would have been perfect if I had the chance of going 225 front.
This is interesting! Though I hate understeer and I would take some rubber off the back...
245 rears would have been perfect if I had the chance of going 225 front.
09-04-2011, 12:44 PM
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You will get the usual amount of full lock rubbing in front, but you will not have an understeer problem. You also can equalize wear since you will then be able to rotate front to back.
Note that I only ran that set-up for rack and autocross. The 245's in front make the car a handful on uneven pavement.
Brian
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09-04-2011, 06:21 PM
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In fact, I bought the pair of 16x8's from the former owner of this very forum. He sent them to me, and just said to send him whatever I thought was a fair price. You can't beat that. For aesthetic reasons, I would much prefer to have gone with 16" Cups, but decided to settle for the D90's.
I should probably also clarify that I used this set-up all most exclusively for US style autocross. It may not be optimum for use on a proper track.
Good luck.
Brian
09-04-2011, 07:39 PM
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I am actually autocrossing a Cayman S now, but have been thinking about returning the 911 to competition. It is a very different car than a Cayman but in many ways, I much prefer the 911.
Brian
09-04-2011, 07:53 PM
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I probably know what you mean... The Cayman is an sample of how a car should handle: neutral, reactive and easy to drive to the very limit.
911s, though, have SOUL...!
911s, though, have SOUL...!
Last edited by anto1150; 09-23-2011 at 11:13 AM. Reason: Sample instead of example... Italian influence
09-23-2011, 08:45 AM
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I thought this could be of some interest:
during the past few days I've made a simple test: acceleration in III gear from 2000 to 5000 rpm (no gear changes that could introduce extra variables, same road, same fuel, same weather etc.)
- Mille Miglia Cup1 7,5x17 and 9x17 with Bridgestone S02a 205/50 fronts and 255/40 rears: took 7,9 seconds
- Design 92 6x16 and 8x16 equipped with Pirelli P-Zero 205/55 fronts and 225/50 rears: took 7,5 seconds
0,4 sec. is 5%... significant difference! BUT the feeling at the wheel was much better on 17s... probably also due to tire difference? (Pirellis are 90%, 4 years old stored in a dark room; Bridgestones are 40% 2 years old, regularely used).
There was no speed diffrence at 5000 rpm, so I assume they are same cirmunference (same gear ratio).
during the past few days I've made a simple test: acceleration in III gear from 2000 to 5000 rpm (no gear changes that could introduce extra variables, same road, same fuel, same weather etc.)
- Mille Miglia Cup1 7,5x17 and 9x17 with Bridgestone S02a 205/50 fronts and 255/40 rears: took 7,9 seconds
- Design 92 6x16 and 8x16 equipped with Pirelli P-Zero 205/55 fronts and 225/50 rears: took 7,5 seconds
0,4 sec. is 5%... significant difference! BUT the feeling at the wheel was much better on 17s... probably also due to tire difference? (Pirellis are 90%, 4 years old stored in a dark room; Bridgestones are 40% 2 years old, regularely used).
There was no speed diffrence at 5000 rpm, so I assume they are same cirmunference (same gear ratio).
