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  • Wheel sizes

    Topic originally created by JBishop on April 5, 2006 8:10 PM and viewed 1882 times in the old forum.

  • #2
    Originally posted by JBishop on April 5, 2006 8:10 PM
    Hi guys I am toying with the idea of putting more modern lower profile tyres on the C4. I have seen plenty of Daytona with 15x9 wheels on the rear. I am thinking of going for 16x9 on the rear and 16x7.5 on the front with 225 tyre width on the rear and 215 on the front with a 55 or 60 profile to give the same tyre diameter as the original 15 inch 215 70 profile tyres. Does anyone have experience with this proposed set up? Will the tyres fit OK under the guards? Any comments appreciated. Thanks John

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    • #3
      Originally posted by Les on April 7, 2006 7:13 AM
      Hi John, If you go to the gallery and look at mine (15215) you will get an idea of what wider and more modern tires might look like on a C/4. In these photos you will find 235/60-15 (front), and 245/60-15 (rear) Michelin XGT's. These are mounted to the stock 7.5x15 wheels. It would help to note that Ferraries of this period utilized a rather wide wheel/narrow tire filament. A Goodyear tire engineer I know suggested to me this might have been in an attempt to stiffen the sidewall's roll stiffness, and/or in anticipation of wider tire sizes that were coming into market. Anyway, every tire to wheel sizing reference I have looked at have made the 215's the absolute minimum tire width for a 7.5 wheel, so there is a great margin for going wider on the stock wheels. The front was rather interesting in a couple of areas. The inside sidewall on the 235/60 wants to rub lightly when the wheels are turned to the stops. I think it was on the anti roll bar (I'll have to check). Of course the stops are adjustable. It was at the outside corner of the tread that was more of a challenge. It's sweep as the wheel is steered has it brushing real close to the front surface of the forward wheel-house. To go wider I had to decrease the tire's diameter slightly, hence the /60. The real limiting factor on the rear of a C/4 is the rear wheel-house out side surface (just inside of the quarter panel), it is much more enclosed than lets say a Daytona. The 245/60 is almost a dead ringer for a 215/70 in rolling diameter, and is the absolute max width that will fit in the back without rubbing during full suspension compression. Again, this is on a 7.5 wheel. I went through considerable trouble to make sure these would clear. I have not checked yet, but I really doubt the nines will go in there without issues. The steering is not quite as crisp as with stretched-out 215's, but the increased cornering limits more than make up the difference. As this old gray mare is a bit of the hot-rod in C/4 circles, it worked out rather nicely. A note to the purists please: Generally I prefer the original look. But my XTX's were shot, and these were a take-off from a Daytona, so they were a cheap experiment. Hope this helps, Les

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      • #4
        Originally posted by Michael Bayer on April 7, 2006 9:49 PM
        When I bought my C/4 out of Pat Hart's collection it had 9" Borranis on the rear and the stock 7 1/2s on the front. The car looked terrific and very aggressive, as do similarly shoed Daytonas. However, there is very little clearance between the tire and the inner sheet metal within the wheel wells, though with a bit of tinkering you could attain the internal clearances necessary, without altering the external pain and body panels. I elected to return to 7 1/2s on the rear, if you are interested I still have the 2 9" Borranis, they are in perfect shape, Pat died before he had the chance to drive the car with them on it. Michael Bayer

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        • #5
          Originally posted by Les on April 8, 2006 12:18 AM
          Very interesting Michael, I really had my doubts about the nines, nice to hear it has been done. Out of curiosity, what size tires were/are on the wheels? Les BTW: I saw your car last year, the body colored front bumper is just awesome.

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          • #6
            Originally posted by JBishop on April 8, 2006 2:14 PM
            Thanks Les I am surprised that the 7.5 inch rims can handle the 245 wide tyres. I might go that way instead of the 9 inch route. Thanks for the very detailed response. It gives me another option. I had a look at your car photos and the tyres do not look like they are 345 at the rear. They look like they belong on the car. I was a little worried that it might make the car look like a drag car. Michael The Daytona do look more agressive with the 9 inch rims. I might take you up on your offer of the 9 inch Boranis. Please let me know what you want for them. I would also need a pair of 7.5 inch rims for the front. My car currently has the mag wheels. Thanks Again

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            • #7
              Originally posted by Aaron on April 25, 2006 11:51 AM
              Just thought I would throw my 2 bits in on the tire discussion - I ran 235/60 15s on stock mags for a couple of years. There were AVSs. The cornering increase was really significant, very impressive for me, a non-racer type. Anyway, as stated earlier, they rubbed in the front somewhere when cranked to one side and a bump was negotiated. The other issue was the reduction in ground clearance – just enough to require caution when crossing speed bumps, but not really a big deal. I may go back to 235s in the future. Aaron

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