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What is the impact of tire diameter on vehicle performance?

Discussion in 'Autocross' started by Brian A, Jun 19, 2009.

    • Member

    granthr

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    Brian

    I am a little late to the party here. On my E30 M3 I am running 225/45-16s on 16x8 BBS RS rims. I have no rubbing issues whats so ever. Now I realize the M3 has boy racer fender flares. BUT those fenders still have lips on the inside. Taking this into consideration, they don't really stick out further than the small fenders on the regular E30. It is really just more of the fender that sticks out. When I had 205/55-15s on my M3 the space between the tire and the fender was about the same as my 318i which also has 205/55-15s.

    Here is a few photos of my M3s fenders with the stock 15 wheel w/ 205/55 and then the 16x8s with 225/45s. I don't know if this really any help b/c I know the M3 is different. But I thought I would share. :)
    • Member

    granthr

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    Some more photos of the fenders.
    • Member

    CRKrieger

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    I'm a big Tire Rack fan, but I've also stumbled across some screamin' deals on race tires occasionally. Kind of depends on who you know.
    Didn't think you were. But IIRC, you're just beginning. I don't think I had much of a clue before 2 seasons - and that time period also included a lot of HPDE instructor training.
    I know. But it's easier to give you a hard time by exaggerating. ;)
    Look; E30 14" wheels are a dime a dozen. You don't need a 'choice' of tires, you need one. Tire Rack has three I'd consider in a 205/60-14:

    Disregarding price, I'd buy the 'Ultra High Performance Summer' Yokohama AVS ES100 at $93 each. I've had no direct experience with this particular model, but I have had previous AVS tires. The biggest complaint I've heard (but not made) is, they're on the noisy side. I found them to have remarkable grip, especially in the wet.

    For 'throwaway' prices, I like the 'High Performance Summer' Sumitomo HTR-200, which I have had - and thrown away because they wear quickly. For half the price, you get half the treadwear. That's a fair tradeoff. But they do stick well. With a set of these and a typical deal on used E30 wheels, you could be sitting on relatively competitive 14" 'Street Tire' rubber for under $500.

    FWIW, the players completely change if you take a look at 195/60-14s. The Yoko is $9 cheaper, there's a very well-respected Bridgestone, and a tempting looking Hankook, all under $85/tire. Then, just for the hell of it, run a search for 205/55-14s and see what turns up. ;)
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    granthr

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    OT Here is a picture of the cool "Classic Car" license plate you use to be able to get in PA. The new ones look like the regular plates, but they have caricature of a Ford Model T on it. It just looks really silly. :eek: Thank goodness if you have an old one you can keep it forever, since it is a lifetime registration! :D
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    Brian A

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    Finally home, where I have better internet access (spent the week in a hotel looking at the internet through a soda straw). Thanks for the pix. Interesting to analyze the fenders but most useful to determine that YOU HAVE A MASSIVELY BEAUTIFUL CAR.
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    granthr

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    Thank you! She is my baby and is treated as such! :D
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    • Technical Service Advisor

    mooseheadm5

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    Grant,
    You can definitely run wider tires on an M3 than you can on a normal E30
    • Member

    granthr

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    Thanks Paul, good to know!
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    Dtireshop.com

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    HI,

    I have a 1989 E30 325i,

    running 15 x 8 Axis wheels ( +25 offset with 12mm front and 12.5mm rear hub centric spacers ), tires are 215/50R15 now, but will get the 225/45R15 Toyo R1R next time,

    rolled fenders on rear, no rubbing issues,

    here are some pictures:

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