15'' vs 16'' BBS RG-F Wheels

[JovialToast82]

Hey all,

Long time lurker - first time poster. I have read most of Mystikal's wheel/tire fitment threads here, which have been super helpful. For my 1989 BMW 325i coupe (with Bilstein B8s and H&R Sport Springs), I'm looking to replace my 14'' bottlecaps either with 15'' or 16'' BBS RG-F wheels:

• 15'' BBS RG-F Wheels
• 16'' BBS RG-F Wheels

It looks like both of these wheels will fit on my E30 with hubcentric rings (to get to 57.1 center bore) + spacers. The 15'' BBS RG-F wheels likely will require 10mm spacers (though may fit without), and the 16'' BBS RG-F wheels will likely require 15mm spacers to accommodate the offsets.

I'm now trying to determine if the aesthetic/looks advantage of 16'' wheels is worth any degradation in performance and driving fun-factor. I've been told that 16'' wheels will make the steering feel heavy and not as good, and I've heard that 16'' wheels will slow acceleration (though seems like the difference would be negligible for a street-only car that I only use for spirited/fun drives on weekends). In terms of unsprung weight, I should add that both sizes of BBS RG-Fs are incredibly light. The 15'' are 10.8 lbs. The 16'' are 12.8 lbs, so both are lighter than my current 14'' bottlecap wheels (which are 14.8 lbs).

For those of you who have run both 15'' and 16'' wheels on E30s, what has been your experience in terms of drive-ability/handling/fun-factor, and what would you recommend between the two? Also, anyone running these BBS RG-F wheels here? If so, would love to see more pics in this thread.

[packratbimmer]

If you can keep the weight down, 16" rims are the better option because the availability of 15" tire is practically nil. I just bought 225/50r15 Kumhos as options are few for my basket weaves.

[JovialToast82]

If you can keep the weight down, 16" rims are the better option because the availability of 15" tire is practically nil. I just bought 225/50r15 Kumhos as options are few for my basket weaves.

Thanks. I do still see several 205/50/15 tires on TireRack (though 205/55/15s are getting scarce...I haven't looked for 225/50/15s because I'm not sure if I want a beefier tire). If you've driven both, how would you compare driving experience and performance (again, for street-only spirited driving) between 15'' vs. 16'' wheels? I do love how responsive and zippy my E30 is at the moment with my 14'' wheels/tires, but have never driven a 15'' or 16'' E30 so don't know how different it will feel.

[packratbimmer]

I think the straight 325i can handle the added weight depending on your differential ratio. I noticed a difference on two cars when I ran heavier wheels/tires: My M10 powered 318i and my 325iX. Keep in mind that you can feel a difference with the spare tire out on the M10 318i - HAHA. I think your query is interesting and overlooked. Added wheel weight is work that the engine must do before the fun can start. What I have found with my 325i cars over the years is that as compression drops off from age, there is a noticeable difference in performance especially if one prefers taller than stock (3.73) gears out back. The 325i is a car that just has enough power to make one feel like they have a fast car - when you need a valve job the loss of compression is apparent. Funny that you asked about the 225/50R15 tires as a new set is sitting mounted in my driveway as we speak - I've not tried that size, but I can feel that they are heavier than 205/55R15 though I have not weighed them. I'll let you know how they feel with 3.45 gears after the last snow melts. I still drive E30 cars rain, snow or shine!

[Digitalwave]

Go with whatever is more aesthetically pleasing for you. For street-only use, a ~2-3lbs difference in the wheel setup is not going to be dramatic.

Tire variety sucks in both 15" and 16", at least for 24" diameter tires. For 23" diameter its a little better, but still not great.

[JovialToast82]

Thanks for the feedback here.

I did a bit more research and learned that my current tires (BFGoodrich Touring T/A 195/65/14) weigh 18 pounds each. The 16'' tires I'm looking at are Continental ExtremeContact DWS 06 Plus (205/50/16) which weigh 20 pounds each. Since the 16'' BBS wheels I'm looking at are actually 2 pounds lighter than the stock 14'' bottlecaps, the net unsprung weight difference should actually be zero, which is good. The only thing I'm not factoring in here is added weight from 15'' spacers + hub-centric rings, but I'm hoping those are minor/negligible for a street-only car.

[Digitalwave]

Hubcentric rings are about 1oz. Spacers can add up, but for average thickness aluminum spacers, they may add up to 1.5-2lbs total (for all 4 of them).

I think you're overthinking the choice. Pick whichever you think will look better.

[packratbimmer]

You are going to be fine with the 16" on a 325i. There might be a slight decrease in MPG depending on several variables including tire weight. Handling is going to improve dramatically and tire selection is where it needs to be. Since you are really thinking into this, which is great, keep in mind that wheels are big "flywheels" and it matters where the weight is on a flywheel. In other words, more weight around the circumference of any flywheel will require more torque to initially spin it up. This is why 318i cars don't work with big wheels and tires. For example, I immediately feel the difference in my E36 318ti when I put my heavier 225/45R17 winter treads on in the fall. I have to shift differently and always think I need to switch from 3.45 gears to 3.64 gears for the winter (which never happens because I don't have the will to swap diffs. that often).

[Digitalwave]

You are going to be fine with the 16" on a 325i. There might be a slight decrease in MPG depending on several variables including tire weight. Handling is going to improve dramatically and tire selection is where it needs to be. Since you are really thinking into this, which is great, keep in mind that wheels are big "flywheels" and it matters where the weight is on a flywheel. In other words, more weight around the circumference of any flywheel will require more torque to initially spin it up. This is why 318i cars don't work with big wheels and tires. For example, I immediately feel the difference in my E36 318ti when I put my heavier 225/45R17 winter treads on in the fall. I have to shift differently and always think I need to switch from 3.45 gears to 3.64 gears for the winter (which never happens because I don't have the will to swap diffs. that often).

If you have to shift differently it's not because of the weight, it's because of a different diameter tire.

[packratbimmer]

The diameter is the same. Correct - its a heavier spinning weight. Try to think dynamically.