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17"wheels for 308 GTSi

Discussion in 'Technical Q&A' started by Ernie Taylor, Mar 29, 2004.

  1. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    I just finished installing some really nice looking 17" wheels on my 308 GTSi. The rears are 9" and have 275 40's. Looks great! Problem is, that's all they are, just really nice looking! Rear tires rub on the fenders over bumps and in the corners. I have stock koni's, looks like I need to upgrade the shocks if I want to add performance to looks? I see a couple of threads discussing suspension upgrades and possible locations to purchase parts. I think that's probably the direction I need to take. Any other thoughts before I look into shock upgrades? Are any Koni's adjustable? Thanks for any help
     
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  3. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
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    Your problem is that your rear tire is WAAYY to tall. A 275/35 is the way you should have gone.

    Your current setup has a 110 sidewall height. Running a 275/35 you will have a 96.25 sidewall height.

    My question is, why the wide rears? A 255/40-17 rear would be optimal. Any wider and you lose performance from too wide tires. I once recall someone telling me that the best width tire was one that was moderately wider then you needed for straightline grip. 275 is a bit much.

    Personally, I think that the best bet to gain performance would be to use a 225-255 tire in the rear if its a 308GTSi. (thats what I will use on my 328) The best to look aggressive would be a 275 though.

    But then again I am a hipocrite since I have 255 fronts/275 rears on my BMW....:) But I will say that I noticed its a bit more sluggish off the line.
     
  4. WILLIAM H

    WILLIAM H Three Time F1 World Champ

    Nov 1, 2003
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    Make Sure you replace the rear stub axles with race units. 308 stub axles are nototrious for failing & leaving you with a 3 wheel Ferrari when you add modern rubber or bigger wheels
     
  5. Auraraptor

    Auraraptor F1 World Champ
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    Sep 25, 2002
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    Will, is that a problem for 328s as well?

    And back to the thread, Mule uses 17s on this car with a taller then stock rear wheel, he thoughts will be valuable too.
     
  6. PSk

    PSk F1 World Champ

    Nov 20, 2002
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    The other danger of over wide tyres is poor grip in the wet, or more danger of acquaplaning (sp?).

    Acquaplaning is caused (I read this in a technical document once) by the tread surface deflecting due to the force of the water. This deflection allows high volumes of water to get under the tyre ... and then it is all on.

    Thus a wide tyre is more likely to acquaplane.

    Also it is advisable to INCREASE tyre pressures in a very wet race for this reason, ie. to help support the tread surface ...

    Ofcourse the other problem is all that extra unsprung weight ... and extra stresses, etc.

    Pete
     
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  8. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    I like the look of the wider tire not to mention this size was suggested when I purchased the wheels. It's funny you mention 35's, could have sworn I was told that size wasn't available. The difference in size might solve the problem, not sure if lower profile tires in the rear (40's in the front) would look odd or cause some handling anomalies?
     
  9. Auraraptor

    Auraraptor F1 World Champ
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    Sep 25, 2002
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    It depends what your fronts are. If you can give me more details on the fronts and rear tires, as well as what size rims are used, I can help you more.

    PS POST PICTURES :)
     
  10. Ferrari_UK

    Ferrari_UK Formula 3

    Dec 6, 2002
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    Jeff Howe
    Just as an aside, I believe non-ABS 328 rims have been fitted to 308 before (especially at around £150 each) :)
     
  11. tele013

    tele013 Formula Junior

    Nov 19, 2003
    760
    Malaga, Spain
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    jesus
    Hi Omar,
    I´m interesting in change the wheels in my 328, and the tires of course. I´m thinking in 355 wheels ¿ what do you think about?.
    You have 225-255 tire in your 328, I think is the correct size, ¿can you post pics of your car?
    Regards, Jesus.
     
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  13. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    Ernie,
    Can you see marks where the tir is rubbing? Is it the outside of the inside? I fitted 18x9 to my car a couple years ago and found there was only about 1/4" clearance to the spring on the inside, so the extra width would need to go to the outside. But if I did that (and it sounds like you did), the tire would rub the fender. The solution is to replace the large diameter (about 3.5" ID)stock springs with aftermarket 2.5" ID spring, then move the wheel in 1/2", that should fix your problem. The smaller springs can be fitted to the stock shocks, but custom loer perches are required and the upper perch on the shock needs to be cut off and a smaller OD one welded on, I used a piece of exhasut tubing I found theat was the right size......then when I got it all done and drove it a little I decided the konis were still not very good shocks, and bought a set Ohlins shocks that are made for 2.5" ID spring. I now have 18x10.5" (anything ove about 9 or maybe 9.5 requires moving the lower shock mount) rears with 285-35 tires and I think that is about all that can be put in the stock wheel well. Agian I kept the outside edge of the tire within 1/2" of the stock location and let the extra width come to the inside, but I did have to put a coule zip tires on the inner wheel well to hold it off the tire in a couple spots.
     
  14. WILLIAM H

    WILLIAM H Three Time F1 World Champ

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    I think it is. If you dont track your car or take corners fast it probably wont be an issue though. It seems to happen under high loads bcus of a faulty design of the original stub axle. Strange Engineering which makes a lot of Hot rod & race parts made some race stub axles for me
     
  15. Mule

    Mule F1 Rookie
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    Jun 25, 2003
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    I have 255/45R17 and 225/45R17. The 45 profile on the rear works, since it is a 255, not 275. It is 3/4 inch taller than stock. The fronts are the same height as stock, but a little wider. This is on a 328, not a 308.

    Lots of pics:

    http://ferrarichat.com/forum/showthread.php?t=6017
     
  16. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    I haven't taken any pictures yet of my new wheels but see yours are just what I bought, looks like my offset is on the outside and yours goes in. My tires are rubbing on the outside. When I first got the wheels they hit on the knoi's so I sent them back and had 1/2" removed from the inside. Wish I would have asked a few questions before. The rears are 9" and clear the koni by 3/8....max.
     
  17. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    You're right, I did go to the outside. There is about 3/8" between the wheel and the knoi now, with a 9" wheel. Tires are rubbing on the outer 1/2". I think now that I'm leaning towards replacement shocks and leaving the tire outboard of the fender. There is about 3" of clearance in the wheel well at a stand still, seems like that's enough travel (not sure) if the shock was good? I did try a shorter tire but it bowed inward and looked odd.
     
  18. brent Lachelt

    brent Lachelt Formula 3
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    Ernie I recently put on 17" Compomotive wheels and 225/45/17 fronts and 255/40/17 rears. I had new stock koni shocks and had no problems with rubbing. I recently lowered my 308 with QA1 shocks(see showroom thread lowered 308). I still have no problem with rubbing. Total cost about $850.
     
  19. Dave

    Dave F1 Rookie

    Apr 15, 2001
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    offset should be around +11.5mm

    Hey Brent, which size wheels, 17x__ front and rear did you get?
     
  20. brent Lachelt

    brent Lachelt Formula 3
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    Dave the fronts were 17x8 and 17x9 on the rears
     
  21. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    I can certianly use help, the fronts are 17x8 with 235 40's and the rears are 17x9 with 275 40's. Currently the rears clear the koni's by about 3/8". I'm thinking that this is going to require more than just tires before I'm happy?
     
  22. PeterS

    PeterS Three Time F1 World Champ
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    Ernie..Just seeing if you may have the original 16" 5-stars for sale. I need a set cheap!

    Peter
     
  23. Auraraptor

    Auraraptor F1 World Champ
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    Sep 25, 2002
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    Erine with a 255/40 rear your setup will should work, and you will sell have the optimal slightly higher rear then front sidewall promoting understeer.
     
  24. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    Peter, I have the aftermaket look alikes that came from Lyle Tanners in CA. Nice looking wheels, I considered selling but looks like may be using them while trying to fix my current problem.
     
  25. Ernie Taylor

    Ernie Taylor Rookie

    Nov 12, 2003
    27
    That sounds like the best fix. I'm wondering if I'll not like the additional clearance and end up investing in shocks that would allow me to bring it back down? Appreciate the feedback.
     
  26. Auraraptor

    Auraraptor F1 World Champ
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    Check on Tirereack.com for the tire you want. If you go the specs page, you can see the actual width of tires at 275 and at 255. That way you can compare and see if you gain a bit of clearance or not. You should I estimate that you will gain 10mm-12mm of clearance, but you will be able to see yourself and know.
     
  27. Mule

    Mule F1 Rookie
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    Jun 25, 2003
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    Remember that mine are on a 1989 328, so they came with the convex wheels (ABS) originally, that is why the wheel surface is farther out and the wheel does not have as deep a "dish".

    Between my rear wheel/tire and the shock is almost two inches.
     
  28. brent Lachelt

    brent Lachelt Formula 3
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    Ernie, Omar is right I have the same wheels as you and had 255/40/17 on the rears with the stock koni shocks (for about 4 weeks before I switched shocks) and had no problems. Just change the rear tires.

    Brent
     

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