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tires

Discussion in 'E30 (1984-1993)' started by ricco39, Jul 27, 2009.

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    ricco39 guest

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    looking to buy tires and whels for my 90 325is i was looking at 205/40/17 but have opened up to 15 or 16's what size in 15's or what size in 16's would give me the same width and height as the 17's and what am i gaining or losing by not going with the 17's? all info will be helpful. i love my e30 and love to drive it and when i want to crank it up i dont want to lose grip on the road thanks for all help and opinions
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    az3579

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    This has been covered quite a few times on the forum. Smaller diameter wheels will be better overall. I think the sweet spot would be 15's, preferably 15x7, with 205-55-15 tires on. Personally I'm considering going down a notch to 205-50-15's, partly because I like the look and partly because... well, it kind of makes the 15's look small with 55 ratio height. :)
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    MGarrison

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    Brian A

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    They are for autocross, but I recently bought Team Dynamics Pro Race 1.3 - 15x7, E30 wheels from Bimmerworld and Kumho Ecsta XS 205/50R15 tires from Tire Rack. Bimmerworld got in a shipment of the wheels earlier this month and they have had them on sale for $99 each. They fit my 1991 318i without rolling fenders or using spacers.

    The wheel & tire combination is a whopping 4.8 lbs lighter PER CORNER compared to my stock 14 inch bottlecaps with 205/60R14 BFGoodrich Traction T/As! There is a substantial difference in the way they ride. I expected the ride to get worse with the lower profile wheels, but it has actually improved. (Bottlecaps are light wheels BTW.)

    I've not yet autocrossed them yet, so cannot comment on grip but the Kumhos are highly regarded and not too bad for price ($88 each).
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    az3579

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    +1 on the Kumho Ecsta XS tires. I have a set dedicated to autocross and not once have I been able to make them squeal. The grip is UNBELIEVABLE! And for the price, it just can't be beat. The pic in my sig is actually my first day with the XS tires on the course. :D



    They are 180 treadwear though, so I wouldn't really bother buying a set for daily driving...
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    granthr

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    I would stay away from 17s on an E30. IMHO they just don't look right on them. They are heavier too as mentioned already. To stay with the factory overall diameter here are your tire sizes.

    205/55-15
    225/45-16 (will probably have rubbing issues on a non-M E30)

    I run the 205/55-15s on my 318i and 325ix on my M3 I run the 225/45-16. I have Kumho esta 712s on my 318i and Yokohamas AVS ES 100s on my M3. The tires on my ix are pos Kellys. They will be replaced over the winter when I have studded snow boots on it. Those are 185/70-14 on steels rims.

    +2 for checking out www.tirerack.com. They will give you plenty of options on what will fit your car. After checking out there website don't be afraid to call them up and get more advise. Their phone reps have a wealth of knowledge and will direct you in the right direction.

    z31maniac guest

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    You bunch of nancies. 17s and 40series tires look great on E30s. :D

    The car just has to be lowered, you can't monster truck it on big wheels and get away with it like you can on small wheels.
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    CRKrieger

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    All those "nancies" will suck the headlights out of your 275-40/17-shod Poseur Mobile© on a track or in the twisties ... :p

    z31maniac guest

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    The same driver in the 318 with 205s will be faster then the 332is with GC suspension and 235/40/17 Star Specs?

    Rrriiiiiiiiiiiiiiggghhtt.

    ;)
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    granthr

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    Just an fyi, my 318i weights in at a whooping 2,360 lbs! H&R suspension and sways and 325 brakes all around. :D It can handle the curves. :cool:

    z31maniac guest

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    While that is true, the extra 350lbs or so that my car is carrying is definitely made up for with the extra 110HP and 100+ ft/tq!

    Oh and 225/45/16 on proper offset wheels shouldn't have a rubbing problem unless the car is scrapping the ground low. An et25-30 shouldn't have a problem running that size. It's what was on my SSR's before I sold them.

    And OP, 215/40/17 is closer to stock OD. Some 215/40s on Kopi rep 17 x 7.5s are always a classy choice with a decent drop.
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    MGarrison

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    How to increase track width on an E30 and bypass rubbing issues altogether -

    Start with some wheel spacers. Wide ones. You'll never get past the rubbing issue until you get those wheels completely outside those peskily constraining fenders and fender wells. Some foot wide wheel spacers should do the trick. Don't forget, you'll now need some lug bolts that are now also about a foot long.

    Now that you're outside the fenders, your only constraint on wheel and tire width is the width of your standard lane to remain street legal which is what... eight or ten feet? Let's go with eight... the car's about 5' wide, so that leaves 3 feet, you'll want a wheel and tire combination that's 1.5' wide, or an 18" wide wheel. I know, sounds small, but if you want to be rollin' on the street without causing accidents, and having every Tom, Dick & Harry crashing into your wheels, then you gotta do what you gotta do.

    Without the constraints of the fender wells overall diameter is no longer an issue, so get some nice big wheels on there. 36 inches. Maybe 46" - don't let yourself be held back now. If you make them big enough diameter you'll never have to worry about them getting hot and the tires overheating, as by the time one spot on the tire hits the ground and comes back around again, it'll have had plenty of time to cool back down to ambient temperature and be ready to go again. Certainly would help to eliminate that pesky problem of slip angles.

    Make sure the wheels are nice and heavy too - strenghtened lead alloy, 200 or 300 lbs. per wheel or more, then you'll never have to worry about a wheel losing contact with the road surface; nice and pretty too - get 'em chrome plated 600 times, and make sure they're spinners. You can never have too much useless extraneous crap on your wheels. Don't forget the deep-dish look you'll want too, get 'em with that 228mm negative offset.

    So, onto tires - nobody needs sidewalls and you probably never have to worry about bending a wheel now anyway, so perhaps just have a tire maker mold some rubber directly to the wheels. You probably don't need much more than half a centimeter in sidewall height, so some 457/.109-46's should be the fitment you're looking for. Hire an artist to custom create your tread pattern too, shouldn't add too much extra expense - make sure they'll be nice and loud when running, you can't make a statement unless your tires generate at least 205db. And since you want them to last, get the tire maker to boil 'em up real hard. A treadwear rating of 10,000 should be about right, with temperature and traction negative ZZ to the 10th power.

    That would HAVE to make any E30 waaay faster! :p

    z31maniac guest

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    You're right 235 may not be wide enough. I haven't bought my new tires yet, I'll probably wait til spring since Auto-X season is almost over and it will still be 2-4 weeks until we have the car running.

    I'm also considering going to 245/35/17 Toyo R1Rs, stock OD and WIDE.
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    granthr

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    Sorry to disappoint, but 15s and 16s are just about right for an E30, IMHO and I think others here too. No? Back when these cars were designed anything bigger was supercar territory. Even the mighty M5 and M1 only came with 16s. So to keep that period look you can't go over 16.

    Good luck to you. But you are at a point of diminishing returns.

    Oh and if I cared about straight line speed I would be driving an American V8.
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    granthr

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    When I say M5, I am referring to the E28.
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    CRKrieger

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    No. You are in a discussion forum about the E30.

    Any given E30 will accelerate faster and handle better on 14" or 15" 205/60-14 or -15 tires than an identical E30 with 235/40-17 tires of the same model.

    Now, you may continue with your argument ...

    z31maniac guest

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    What is "handle better?"

    Are you suggesting that a 205/50/15 will produce more outright grip than a 235 or 245/40/17? Remember I am using lightweigh 17 x 8s, that have only a few pounds on most 15 x 7 inch wheels.

    Is the extra weight and rotating mass going to slow acceleration and braking? Yes.
    Is it going to have the overly exaggerated effect that you all claim it will? No.

    I don't have the empirical evidence to back it up, and neither do any of you, buy I would suspect the weight/gearing disadvantage would maybe make a .1-.2 sec difference on a 0-60 run. If I had another set of wheels, when I get done with the swap I'd be happy to test it but I don't.

    But then again, in my case that is easily overcome with an extra 100hp at the wheels. I was calling my car a 332is since it will have an S52, so I was still talking about an E30 senor.
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    Brian A

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    Clarifying my prior pointless post

    Tire quality/design is the dominant factor in keeping traction. It's usually a direct relationship: the softer/grippier the tire, the quicker it wears. If you are still running 14 inch wheels, you'll likely have to change to a larger diameter wheel to get the grippiest tires since good tires in 205/60R14 are rapidly going extinct. I had to do that to upgrade my autocross tires to what Tirerack refers to as "Extreme Performance" summer tires. Last, you want the widest tires you can fit and no one with authority seems to know what that is for an E30.


    MGarrison posted a link to a circumference calculator a couple of weeks ago; look in the posts he listed above. Use it to calculate which profiles are appropriate for which wheel diameter. Alternatively, if you look at any wheel with Tirerack, they recommend the correct tire size.

    Maybe no, maybe yes. It depends on how forward your extra 350 lbs is. If it's a technical autocross course with carrousels and hairpins, the 318 just might spank your bottom. 0-60? Well, okay.


    MGarrison, you are always such a font of wisdom. This is brilliant. I had wanted to put on Formula 1 wheels on my E30 (Formula 1 runs on 13" rims) but was worried about rubbing because they are probably wider than stock E30 width. I hadn't thought about it as inventively as you have.


    An added benefit to your idea is that there would be a natural sag to the wheels from the foot wide spacers. This would substantially increase negative camber which would actually INCREASE the harder you cornered the car. Genius!

    17" Alpina Kopi replicas are 21 lbs each. Even BBS-LMs are 18.8 lbs each. 15" BBS-RG-Fs are 10.8 lbs each and 15" Team Dynamics 1.3s are 13.2 lbs each.

    z31maniac guest

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    What a bunch of uppity purists! Is anyone in this thread besides me and Botond under the age of 40? :p

    Yes compound is the dominant factor, but in my example, I'm assuming both cars are on the same tire say a 205/50/15 vs 245/40/17 Kumho XS, the added weight and rotational inertia are overcome by the vast increase in section width, for my usage.

    Possibly on a very tight course the stock-ish 318 would be faster with the same driver, but not on track during HPDE's (which my car will also see) or blasting down your favorite back road.

    Wheel weights: Enkei RPF1s in 15 x7 are 9.9lbs and SSR Comps are 8.8, what's your point? My Work wheels are around 17.5 IIRC, not bad for a 17 x 8. The lighter wheel doesn't overcome the smaller tire. (Not even taking into account lack of tire choice in 15" sizes with the exception of R-Comps and slicks.)


    Not to mention if this is the guys street only car these small % differences you guys are clamoring over are going to be barely noticeable.
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    az3579

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    And THAT is the big +1.
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