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    tire sizing question...

    I have been thinking about tires for my coupe and was hoping you guys might have some input! So my 99 Z3 has the 17" wheels, which according to tirerack has OEM sizes of 225/45 and 245/40.

    The original owner had put on 235/40 and 255/40; they're on the car now.

    If I were to keep to the wider sizes, I have significantly fewer choices than if I were to go with the OEM sizes. But as the car has been lowered (a bit more in the front than rear), would going back to a 45 profile tire up front possibly cause rubbing? Here's a pic I have, I can get a closer one if needed... http://farm1.static.flickr.com/33/67704607_f712cd8bac_o.jpg

    What are my options here with sizing? Sorry if I'm asking dumb questions here.


    Thanks in advance,
    Dan


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    Section width is your concern ...

    No problem on the rears as they'll take up to a 275/40 with no clearance problems. I'm sure you're concerned about the front clearance from tire to strut. I checked TireRack for specs on a 225/45 vs. a 235/40 (used Bridgestone Potenza RE-01R) and the 225/45 has a section width of 8.9" ... the 235/40's is 9.5". So, if your question is "Would you have clearance going back to the 225/45?" ... Yes, you'd actually have MORE clearance. BTW, I have 235/45 up front and 265/40's out back; their diameters are identical at 25.3"; clearance is no problem, but I have not lowered my Coupe. I love this tire size combo since it gives more wheel rim protection and also makes the speedo "gnat's on". I'd recommend that you stay with the 235/40 and 255/40 that the original owner installed ... that's a great tire combo, better than stock, IMHO. You wouldn't go wrong with a set of Goodyear Eagle F1 GS-D3. There's even a $50 rebate offered by GoodYear.

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    The Eagle F1 GS-D3s are the ones I'd like to get

    ...but they don't run in 235/40 and 255/40, at least not at tire rack? I guess I should look around... that size combination has pretty limited choices, it seems.

    Thanks for your help

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    Eagle F1 GS-D3s are great tires.

    I have them on my S54 M in 225/40/18 front, 265/35/18 rear. I can't help you with your size search, but if you can find them in a size that works for you, they're a great tire. Very high total grip, very predictable and forgiving, absolutely awesome in the wet (think 80mph in a thunderstorm downpour with no hydroplaning at all :-) The only issue I have with them is that they do tend to take a double-set on turn in. The tread pattern allows a bit of shifting as the side load is first applied before the tire is set in steady-state cornering. It took some getting used to, and I wish it wasn't there, but once you get used to it, it's not really a problem. That's actually a big part of its forgiveness and predictability in breaking loose. Overall, a great tire.


    Kevin 368s #19


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    But the 225/45 would have a taller sidewall

    The strut clearance is paramount as well. But if the car has been lowered, part of the question on the 225/45 stock sizing is whether the slightly taller sidewall height will hit the wheel well (Take 235mm and multiply that by 40% to get the sidewall height, and compare that to the same calc with the stock.. 225 x .45). From the pic, I'd say no. 7.25mm higher. Might hit, but looks like it wont. Need more pics from different angles to be sure. btw.. was that a cop car in the back ground??

    The other two consideration factors for me on the front sizing would be that the 235mm tire will be slightly harder to steer, unless it is pumped up to at least 34 all the time (So, for me, the 235 would be less desirable from that perspective). Cornering wise.. the 235 would be better.

    Secondly, because the 235/40 is a shorter sidewall height, it looks cooler. Slightly shorter height than a stock 245/40 rear. To add context, I mean.. look at a stock 17" tire sized Coupe. The amount of rear sidewall height on the rear looks like an 18 almost. Nice. The fronts though, look tall and juuust slightly too high.

    My recommendation would be that if the steering response is not an issue, go with the sizing you have for looks, traction, and cornering. Or, stick with the front sizing you have, but go back to stock on the rear and add 1" H&R spacers. I stayed with stock front and rear and added the spacers to the rear. For me, steering response is important, plus I want to keep the tires light with less rubber for quicker spin up. I don't track the car, so I don't need the added higher speed traction. The rear spacers make the car look extremely fat arsed without adding weight.


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    should be ok, more pics inside










    Couple of different angles. Looks like at the narrowest, there's a 3cm clearance.

    So I think I'm okay going back to a 45 profile tire, but my preference is to keep the sizes I have now. Unfortunately, there really only are a handful of tire choices at that size. Basically I'd be choosing between ContiSport 3's, or else Yokohama S.drives.

    Staying at 235/40 for the front doesn't help; that's the problematic tire size. (well really, it's the combo of those two sizes that tirerack for some reason can't deal with). I could do a 235/45 and 255/40, and get some choices I'd be happier with... now I'm thinking if that's not the way to go? BLEH.

    (BTW, yeah it that first photo that car in the background is a park ranger... :) I was taking photos near Sutro Heights, in San Francisco. Here are a couple more

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    225/45 will easily clear then..

    Thanks for the extra pics. Even if your current springs and shock compression ratio were on the "moderate" side (as opposed to firm), the extra side wall height with the stock 225/45 size should easily clear while cornering hard. I would predict, you'll still have about 3/16" more wheel gap than my Coupe with the stock size. I'm using the TCK Koni kit with the single adjustable shocks, and 400# springs. They are mid range for stiffness (not that stiff). If I corner super hard I might juuust baaarely scrub the wheel well liner. I think you'd be fine.

    The set up you have looks cooler than stock. I really like that sidewall height, and it would be enough for me to not pine after 18" rims. As it is, I live with the fact that the stock rear sizing height looks perfect, and the fronts look.. just slightly too high. But, that's ok. I really like my stock wheels and don't want to change.

    Not trying to talk you into the 235/40, but, don't necessarily trust TireRack. They do not stock every tire size made. Pick out a few tire makes you like and hit their Web sites. Also make calls. It could be that for this size, TR has all that is available.. just sayin'.. I've found sizes for my X5 that TR didn't have.

    Also, when considering size changes, always perform the sidewall height calc. It tells you, on paper, a great deal about what your tires will look like on the rim. Tire width (in mm) X profile number as a decimal = Your tire sidewall height in mm. (i.e. 225mm x .45 = 101.25mm.

    225/45 = 101.25 mm (Stock sidewall profile look)
    235/40 = 94 mm (What you have. Ooooo cooool)
    235/45 = 105.75 mm (Alternative sizing. Whoa.. taller than stock!)


    Sutro Heights? Ok, had to Google Earth it. Cool. Just north of Golden Gate Park.
    Hey dk, do you happen to live in one of the houses / apartments in those blocks? Or, any of those west side blocks? I've got some questions about how those blocks are designed. I'm really curious about the backyard common space within the center of each block. There are hundreds of blocks designed with that large common space, but you cannot see it from the street. Only from Google Earth / ariel. Nice. Would love to see inside some of them. Seems kinda like a "New York" concept.






    '02 Z3 Coupe 3.0i [Hellröt II - Walnuß]
    '03 X5 3.0i [GrauGrün - Beige]
    '01 Z3 Roadster 3.0i [AlpenWeiß - TraumRöt]

  8. #8
    dk
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    OT: urban planning

    Thanks for spelling it out for me, it hadn't occurred to me that the 45 profile on the 235 width would be greater than stock!


    Huh, I've never lived in any other kind of house that wasn't a ring around enclosed backyards...? Growing up in the outer boroughs of NYC, where we had yards, that's how it worked too.

    I don't live out there (that far west is the more suburban parts of SF), but where I live in the Haight Ashbury, it's similar. Yards a bit smaller... Here's a couple pics of my backyard

    So from space it looks like a common area, but they are in actuality divided and attached to each building.

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    Re: OT: urban planning

    Awe man.. I was picturing it all .. like some kind of giant common area. A hidden private park space. haha..

    Hey, you should start a new social cultural movement.. and take them fences down. Live the park dream!

    I'm kidding. It would probly only half way work. People wanting their own space and all.

    Hey DK, you're really lucky to live in SF. It is such a great city. We visit as often as we can. Headin' down there in April as a matter of fact. A few years ago we discovered this awesome band playing on Market street, at the bank across from Virgin Records; Sinclair. Great sound. I need to pick up more of their CD's.

    Enjoy that town!





    '02 Z3 Coupe 3.0i [Hellröt II - Walnuß]
    '03 X5 3.0i [GrauGrün - Beige]
    '01 Z3 Roadster 3.0i [AlpenWeiß - TraumRöt]

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    thank you everyone for the info! I'm learning too


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