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Which tire size for 17s?
#1

Hi there,



I have a 94 midnight blue coupe, with stock 16s (and 205s up front and 225s in back). I am about to buy a set of 17" C2 turbo wheels.



http://www.wheelenhancement.com/index.php?...etail&id=31



The local seller has a set of used Michelin Pilot SX 235-45s that he said I can put on the front (for only 100 bucks), and go with 255-40s on the rears. We both understand the more normal setup is 225s with 255s. What I get a little more oversteer with the 235s up front? The seller is a true 968 expert/lover…he current owns 4 cabs and has owned a few coupes.



Thanks!
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#2

Are you getting 7.5" rims up front or the 7's.
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Current:
2016 Cayman S
Former:
94 968 Cab 6 Spd. Black/Cashmere D1R SC
86.5 928 Garnet Red Metallic
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#3

I put 245 45 17 front



275 40 17 rear



Seems towork fine
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#4

wow - that's a tall tire - 25.7" - that's a full 3% off on the speedo, and the gearing - probably helps a bit on the mileage, but costs a bit on accelleration - probably rides pretty danged smoothly though with the extra sidewall area
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#5

[quote name='flash' post='40606' date='Aug 30 2007, 07:21 AM']wow - that's a tall tire - 25.7" - that's a full 3% off on the speedo, and the gearing - probably helps a bit on the mileage, but costs a bit on accelleration - probably rides pretty danged smoothly though with the extra sidewall area[/quote]



Flash,

I assume you are referring 968crazy's 245/275 setup. How much would acceleration be decreased?



So 235/255 should be ok?
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#6

yeah - a 235/45 won't be too big - there are a few people who have gone to that - while not the end of the world, i would not recommend it on a 7" rim, but on a 7.5 it would be ok - it will throw the speedo off a bit, but not too bad



255/40 is standard on a 9" rim, so, no worries there
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#7

Thanks guys, I will go with the 235/255 combo as the wheels are 7.5 & 9.
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#8

Flash:



Like ender, I also have 16's on my 95 coupe. I found a used set of 7.5 and 9 inch C2 Cup wheels that the seller says are off of a 993. Will these wheels fit on the 968? No hub problems? Also, you mentioned that the 235/45 tire would be ok on a 7.5 inch rim but the speedo would be a little off. Is there a tire size that you would prefer to see on a 7.5 inch rim? What was standard? Is there a tire size would keep the speedo in check?



Thanks.
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#9

[quote name='aventuragrun metallic' post='40651' date='Sep 1 2007, 12:02 AM']Flash:



Like ender, I also have 16's on my 95 coupe. I found a used set of 7.5 and 9 inch C2 Cup wheels that the seller says are off of a 993. Will these wheels fit on the 968? No hub problems? Also, you mentioned that the 235/45 tire would be ok on a 7.5 inch rim but the speedo would be a little off. Is there a tire size that you would prefer to see on a 7.5 inch rim? What was standard? Is there a tire size would keep the speedo in check?



Thanks.[/quote]



According to the manual, the stock tire size for the 17" 7.5 and 9 inch rims are 225/45 front and 255/40 rear.
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Current:
2016 Cayman S
Former:
94 968 Cab 6 Spd. Black/Cashmere D1R SC
86.5 928 Garnet Red Metallic
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#10

correct



as for the wheels actually fitting, i would need to know the offsets - are they C2 Turbo or Cup? that might determine the offset
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#11

Got the 17s with 235/45s and 255/40s put on yesterday. Looks great and drives better than before! Thanks guys!
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#12

The car does feel a tiny bit slower off the line. How much do you think the extra weight between stock 16s and the C2 Turbo 17s costs in terms of 0-60 acceleration? I understand additional weight at the wheels is about 4X weight elsewhere.



Also, the psi is 36 for all four. If I want a bit softer ride (living in san francisco with some non comfy roads), should I try reducing the rears by 2-3 psi?
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#13

could be a tenth or two on the 0-60, depending on the tire friction



a couple of pounds will soften the ride - depending on the tire, it can either improve or degrade handling - what did you put on?
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#14

[quote name='flash' post='41485' date='Sep 20 2007, 01:36 PM']could be a tenth or two on the 0-60, depending on the tire friction



a couple of pounds will soften the ride - depending on the tire, it can either improve or degrade handling - what did you put on?[/quote]



Thanks Flash! 255-40-17 Bridgestone Potenza RE-750s on the rears. The fronts are 235-45-17 Michelin Pilot SX.
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#15

I like the 255/40-17 on 9x17's all around for track duty. Works great with my KWs.



Street, 245/40-17 on 7.5x9/255/40-17 on 9x17s. I'll like move to 255's in the front on 9x17 for my next set.



Autocross, 245/40-17 on 8x17/ 275/40-17 on 9.5x17. Realize, I need to adjust the rear bar heavily between the configurations, it would plow in this configuration.
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