OK, let's get a list going of the pros and cons to 18" over the stock 17" wheels.

Con: acceleration suffers

Acceleration doesn't necessarily have to suffer if you get a light weight 18 from a good company. On a similar note, if you get an aftermarket 17 of the same construction, of course it will be lighter.

17's are generally lighter and the tires that fit them WILL be lighter.

so you save weight two ways right there.

if you figure in the overall tire diamter then you're going to be essentially changing your final gearing again.

with a 235/40/17 tire it is 525.8mm tall.


with a 235/40/18 tire is is 551.2mm tall.

if you want to use narrower tire (sacrificing grip) you can choose to use a 225/40/18 tire and it is 547.2mm tall.

you are losing a significant performance aspect right there, it's similiar to changing your 3.23 rear diff to a 3.15 - you'll lose in acceleration by an amount equal to the percentage of the difference in the gearing change.

Bottom line, I hung up my 18's and I'm running 235/40/17's all around.

-Ron

Also, Im not sure if this is just my car but if you slap on 18's and dont change the suspension, your handling wil suffer. Mine feels pretty bad(body roll) compared to when it was on the stock wheels. Im going back to 17's because of that and the performance issue. To me the looks dont offset the downsides.

Mikey has another point, throw on heavier wheels and tires and you're going to give your suspension an extra work out. that's generally a bad thing, your brakes will suffer as well!

Originally posted by themadhatter
17's are generally lighter and the tires that fit them WILL be lighter.


is this true? since the tires are going to be roughly the same overall diameter, won't the 18" tires have a shorter sidewall and therefore less weight?

anyway, you also get a better selection of tires (and better prices) for 17".

DSK,

figure from the extra 30mm of aluminum and rubber/steel for the 18" wheel/tire combo you really aren't going to be saving anything.

Compare your wheels for example:

the 17x8 SSR Comp weighs 14.3lbs each
the 18x8 SSR Comp weighs 15.0lbs each

that's 11.2 ounces more per wheel. work this into a wider SSR Comp and you're looking at over 1lb more per wheel. Granted this isn't even a 1lb difference on this example but use a different wheel all togethar and you're looking at several pounds difference per wheel size.

then when you add the tires such as S-03's (not the lightest tire on the block), increasing it's diameter is going quickly bring up the total weight of the combo.

I hope that made sense. :)

i heard somewhere that the theoretical best handling of the E36 is achieved with 17's anything more and handling potential goes down.

Ben

I noticed a slight difference going from 17' BBS RK's to 18' Borbet TD's, but if performance isn't a big deal (like in my case :rolleyes: ) then it's all about preference after that....

But Ron has brought up some great issues of the advantages of having 17's over 18's....(have you made up your mind yet Ron ;))

yup!

ASA FR1 17x8 Forged 18lbs each. :buttrock

Sweet, thats what I like to hear! :D

I'm wearing 18's right now, and on my way back to 17's.

Originally posted by themadhatter
yup!

ASA FR1 17x8 Forged 18lbs each. :buttrock

Excellent choice. Thats what I'm going with also.

Originally posted by 96cosmosM3
Excellent choice. Thats what I'm going with also.

Hey!, no fair...that's what I want too....hehe:D

it's a very nice wheel and the fact that it is forged is a little known fact. I just hope it fits my bbk properly, if not....spacers here I come!

-Ron

17" - Sporty/enthusiest looking
18" - Ghetto/punk looking

Your call.

not at all Kramer.

17" sporty
18" flashy

any and all chrome = Ghetto/punk looking

(oh, oh...I have 17" BBS RK in the polished finish , not painted or chrome. Where does that fit?)
I'm not digging anyone here, everyone has their own tastes. No biggie to me.
"It's all good."

One point - even if the weight of the 17" and 18" wheel/tire combo is the same, the 18's are going to be slower. This is because most of the rotational mass(the actual rim of the wheel) is further out from the center and is heavier(it has to be to have a 1" larger diameter)

Yes, 18" tires do weigh more than their 17" counterpart for a given width. Check out the specs.

18's can be faster(around corners) on some cars though. Stock Boxsters come to mind...

Bill

.........ok way of topic, ...but which size would be best for E30?? I'm thinking 17, it seems that this thread "certainly" prefers them, compared to 18's(which i would'nt do anyways), but any suggestions/comments would help........

Currently looking at these....
http://www.geocities.com/st3alth0ne/847.jpg

Whadda think?

I'm not sure on an e30, or what the offset requirement is on those. They look great for an e36 though. M3 wheels for an e36. On an e30, I definitely wouldn't go w/ 18's. That's all I can say here, I'n not an e30 expert, but. I'd look into some e30 M3 wheels. Can't go wrong there.
Good luck.

Mike
'98 328iC
Nashville

I think the e30 offset is 20mm.

My $.02, Ron this is what I noticed. I picked up Kevin's wheels last night (one had a flat,lol) and I felt that the 18inch wheels felt better than the 17 inch ltw wheels I had on before. The 18inch wheels are about 2-3 lbs lighter per wheel than the ltw wheels. IMHO, I think the 18inch wheels ride much better on my car. I was affraid to jump to 18 but it seems to be a great move thus far. Aslo maybe someone can answer this for me. I heard for every one lb of rotatioan mass gain you loose the equivalent of .5 hp

I'm thinking about running BBS RCs on my car (not RC-J) and it looks like these wheels are pretty light for 18s at only 18.1 lbs (according to http://home.pacbell.net/dkippen/bbs_wheel_weights.xls). I'm pretty sure my contours weigh 22.3lbs front and 23.4lbs rear. There would be more rotational diameter but they would still be a hell of a lot lighter overall. Now I would still have to address the suspension issue.... (more of an excuse for a suspension upgrade :D)

I would think a stock ///M3 susp would handle 18 wheels just fine, IMHO

Compact6 - you're correct.

the lighter BBS RC's are a great upgrade and also consider you may have a lighter tire mounted as well.

Basically, the lighter wheel and tire makes the suspension work easier - it has less weight that it has to tame.

the shorter sidewall in most cases also gives a better feel in aggresive driving but some of us (me) want to maintain the 17" diameter to keep the gearing benifits of the car and if we stick with a lighter wheel (SSR Comp, ASA FR1, Superleggera, BBS RK & RC etc) we gain even more then the typical 18" wheel and tire combo.

Post pics in the bimmer rides section when you get the rims on! :)

Is it just me or are the RCs extremely light for not being forged... How much less do the RC-Js (forged) weigh?

This thread scared me away from 18s at first but then I looked at the weights and saw that RCs were so much lighter than Contours. I'll probably go with a set of S-03s too which, like you said before, arent the lightest tires.

Nite,

the RC's are very light - they are also very soft too. :(

BBS RC - 18x8" 19.5lbs
BBS RCJ- 18x8" 17.9lbs

not too much of a difference but much stronger.

Really? RCs are soft?

The table I posted above has the Cast version 18x8.5 listed as 18.1 lbs each.

Nite, my table show's 18.7 so go figure. my guess is that either of our tables don't include the offset which can be a HUGE chunk of metal.

either way, I used the 18x8 to compare apples to apples as best as possible.

:dunno Dunno... I know for sure its lighter than my chunky M Contours. I'll probably go with a set of 18x8.5 silver finish RCs (I was hoping for polished but apparently they're no longer produced in that size). What tire sizes would be optimal? 225/40 all around or 225/40 in front and 245/40 rear?

225/40/18 with the shorter sidewall would provide better response then the a 235/40/18.

the extra 10mm of the contact area will not be missed.

edit: I haven't run staggared 18's so I really can't comment on that though.

I would be running 18x8.5 all around so I guess 225/40 is what I would go with.