Wheel Size - 17 or 18

[gtiboy2001]

Hi Everyone,

Just wondering which wheel size is better for time attack/lapping. I was always under the impression that 17 would be lighter/better. But wanted to get some opinions on this before I order new wheels. I've got an E36 BMW that has OEM 15" rims right now, so looking for an upgrade

Thanks!

[MEANMCHN]

Re: Wheel Size - 17 or 18

Depends on the tire in my opinion, I like 17s with R-compounds. They give the right type of feel without being super harsh because of the stiffer sidewall of the R-compound. They also provide a bit more protection from potentially damaging a wheel on the curbing or an accidental off.

[haikara2308]

Re: Wheel Size - 17 or 18

I'm running 17s on my E36 same as other people I know. 18s are heavier and you may have more fitment issues if you plan to run wider rubber, also tires for 18s cost more than 17s.

[gtiboy2001]

Re: Wheel Size - 17 or 18

Thanks for the replies.

Haikara2308, What width do you run on your E36? I just put on an H&R cup kit and wasn't too sure what would fit without rubbing. I was thinking about either going 17x8 with a 40mm offset or 17x7.5 with a 38mm offset. Does the .5" really make that much difference?

Also, what wheel weight is considered to be decent?

Sorry for all the questions, new to all of this! Thanks for everyone's help!

[haikara2308]

Re: Wheel Size - 17 or 18

I'm running 17x9 apex arc 8 42mm offset with 245/40/17 AD08 tires. I need to run spacers though in the front to make it fit without rubbing. Its hard to say what would fit/ wouldn't fit, you have to factor in your alignment and the size tires you are planning to run.

The .5" difference matters depending on how wide a tires you plan to run. 17-18lbs per rim would be considered light. Depending on your budget, you could look at Apex Arc 8, Kosei K1 and D-Force LTW as rim options if you want them to be light.

[3wheeler]

Re: Wheel Size - 17 or 18

I recommend you go with the exact same wheels as Spencer(haikara2308). Kosei's are another option but they bend quite easily and you end up paying more than the cost of the ARC8's....ask me how I know.

To run these wheels, you will need at least 10-15mm spacers and I highly suggest you switch to wheel studs instead of the stock wheel bolts - they are much less frustrating to work with. Lastly, stick with 245 tire on a 9" wheel as you will maximize the contact patch with this combination.

As for wheel weight, anything from 16.5-17.5 is considered light. The Kosei's are the lightest(16.8lbs) out of the three you mentioned but again, I would not recommend them. The ARC8's are heavier at around 17.2lbs, but you are getting a much stronger wheel.

Oh, and expect to roll your fenders if you have not already!

[wparsons]

Re: Wheel Size - 17 or 18

My 17x8's weigh 15.5lbs each, 17x9's are about 16lbs in the same wheel (Enkei RPF1).

[3wheeler]

Re: Wheel Size - 17 or 18

My 17x8's weigh 15.5lbs each, 17x9's are about 16lbs in the same wheel (Enkei RPF1).

Us E36 folk can't use RPF1's as there is no 17", 5x120. Not that it bothers me, seeing as how my BBK would get in the way.

[wparsons]

Re: Wheel Size - 17 or 18

Us E36 folk can't use RPF1's as there is no 17", 5x120. Not that it bothers me, seeing as how my BBK would get in the way.

Well I'm no help then I personally really like the Kosei K1's on almost any car, and they seem to be really popular on BMW's.

[3wheeler]

Re: Wheel Size - 17 or 18

Well I'm no help then I personally really like the Kosei K1's on almost any car, and they seem to be really popular on BMW's.

I've used them for two seasons and I like everything about them other than how weak they are(went through 3 wheels). Having said that, if you don't mind giving up tenths or seconds by not using the curbing, then they are a great wheel.

[Saj5DJ]

Re: Wheel Size - 17 or 18

If Miatas can bend them no problem, you probably don't want em on a Bimmer.

[Carguy]

Re: Wheel Size - 17 or 18

Consider the wheel and tire weights also. Lighter is better for sure, but so is sidewall stiffness, contact patch size, suspension setup, etc - not to mention what wheels and tires are available that will fit your car. I used the table below to decide on 17x9 Enkei RPF1. My tire choice was made on the fact that I wanted to try the Rivals and their stiff sidewall construction (compared to RS3s) so as to compensate somewhat for the compliant stock suspension on my BRZ.

What I wanted to do was find a wheel that fit my car, and then optimize overall weight, stiffness, and contact patch. Of course I also wanted to keep the cost as low as possible. The first thing I did was eliminate wheel sizes that don't have the correct PCD (Subaru BRZ requires 5x100). Next I checked that the wheel width and offset could actually fit my car (forums are good for that). Finally I made sure the tire diameter was correct for the BRZ and I calculated sidewall stiffness using the tire's aspect ratio in relation to the tire's width. Here I guesstimated that a higher sidewall would be less stiff than a shorter sidewall. The contact patch is simply based on tire width.

It was relatively easy to choose the 17x9 +45 wheel with 245/40-17 tires. The results on track were better than I expected since at the OTA school during the May 3/4 weekend I got virtually no sidewall roll over. We'll see what higher temps and competition brings this season however I am quite satisfied with the setup so far.

[haikara2308]

Re: Wheel Size - 17 or 18

Just realized that the Rivals are lighter than the RS3, AD08 and ZIIs in 245/40/17. Never really thought about tire weight before this.

AD08-26lbs
Z2- 26lbs
RS3 ver 2-25lbs
Rivals- 24.4lbs
PSS-23lbs

[3wheeler]

Re: Wheel Size - 17 or 18

Just realized that the Rivals are lighter than the RS3, AD08 and ZIIs in 245/40/17. Never really thought about tire weight before this.

AD08-26lbs
Z2- 26lbs
RS3 ver 2-25lbs
Rivals- 24.4lbs
PSS-23lbs

While less weight is almost always better, it does not make up for a poor performing tire, so do not make a decision based on that information alone. And I know some don't want to hear this, but the Rivals are one of those tires...IMO(and many others)


Now, back to wheels..

[Saj5DJ]

Re: Wheel Size - 17 or 18

Choosing tires based on their weight is like choosing a method of contraception based on it's flavor.

It's not going to result in an ideal solution...