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17" Tire Size advice

 
Old 01-12-2002, 01:46 AM
  #1  
2cati
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Post 17" Tire Size advice

re: 1994 968 Cab with factory 17" C2 wheels
fronts: 7.5"
rears: 9.0"

Gents,

Seriously thinking of going with marginally larger tires. The car will be a daily "summer" driver occasional DE event.

Front: 225/45 -> 235/45
Rear: 255/40 -> 265/45

Decided that I will go with the Bridgestone S03 tires over the Toyo T1S.

Any feed back would be appreciated.
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Old 01-12-2002, 01:50 PM
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ninefiveone
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Here's a data point...

In regards to wheel and tire size, there's an ideal tire size for a given width. Usually a manufacturere will have a range of wheel widths that a given tire will fit but it's the size right in the middle of the range that will work best.

As one goes to wider tires on the same rim width, the tire doesn't "sit" on the pavement as flat as it should. Handling suffers.

There's a lot more to it than my extremely basic explanation but you get the idea.

Hugh
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Old 01-12-2002, 11:52 PM
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andycan
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Check this out http://www.paspeedo.com/calculator.htm and the you can see the difference in the size of the tires.
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Old 01-18-2002, 09:24 AM
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George Stevens
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Can't quite understand why you would want to put wider tyres on your 968.

I have driven a 968 club sport and was really impressed with the directness of the steering.

If anything, if were me, I would put narrower tyres on the front 205/50 and stick to 255/40 on the back so at least on a track you will have neutral handling with a bias towards controlled oversteer
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Old 01-18-2002, 09:28 PM
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2cati
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I have to disagree with the recommendation of the 205/50/17 - bias toward "balanced oversteer".

When I purchased the car with it was equiped with 205/50/17 fronts so the car had a bias to "understeer". Also there was a noticable difference in straight line braking power.

Thanks for the input!

Stock sizes are more than adequate especially with the latest tire technology.

Thanks Again!


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Old 01-19-2002, 05:15 AM
  #6  
George Stevens
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I agree that as tyre technology has advanced braking distances have got shorter.

My 1992 964 RS is fitted with standard 17" rims with Bridgstone SO2's 205/50 on the front and 255/40 on the rear.

Advice from all the respected Porsche specialists here in the UK is just stick with the standard rim and tyre sizes.

If they cope with the 270bhp of my RS surely they are more than adequate for a 968

I just think that the 968 was such a great handling car out of the box why modify it!!!

Interestingly Lotus have just fitted narrower tyres on the new Elise to improve the handling and steering feel!!!!

We will have to agree to disagree
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Old 02-06-2002, 05:31 PM
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MadMax
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This is a very late reply to this post but I must. George, the reason a 205/50-17 is enough for your 911 is due to maximum tire loading NOT width based per se. As you know 911's are very tail heavy and transfer their weight forward to a more balanced weight dist. under hard braking. A 968/944 does not. A 944/968 is amost 50/50 weight dist. sitting still. Porsche mandates the 225/45-17 wheel because of weight baring capability and to minimize front wheel lock up under hard braking as the weight is transfered to the front wheels. That's my $0.02 anyway.

Cheers! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

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