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      11-21-2018, 07:34 AM   #1
landapanda
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18" vs 19" setup for track

I wanted to post my thoughts on this topic that I have given a lot of thought recently and get everyone's input.

Assumptions:
- Camber plates, big brake kits, pads and fluids are out of scope of this discussion.
- I am focused on attaining an ideal track day setup, not a racing one as I wanted to keep compliance with club racing rules out of scope.
- Wheel budget is limited to $2,000 for a set of 4 wheels
- Tire budget is limited to to $1,200 for a set of 4 tires

I have couple of concerns/questions regarding the proper function of the electronic and mechanical systems. Then there are subsequent decisions driven mainly by cost, performance, practicality, weight and aesthetics in descending order:

1a. How much can tier diameter deviate from OEM setup before ability of electronic systems to function as designed is impacted - abs, traction control, stability control? Does this matter with DCS and ESC turned off?
1b. How much can tier diameter deviate from OEM setup before ability of mechanical systems to function as designed and their longevity is impacted - rear differential is the only one that comes to mind.

Cost:
2a - assuming comparison of same make/model or across manufacturers looking at similar material and build process, 18" wheels are cheaper. Same can be said for tires.
2b - 18" square setup will give you the ability to rotate tires front to back, saving you money. Arguably, this is true for a 19" setup.
2c - a square setup with the right tires will also allow you to flip those tires (run them backwards - counter to their intended rotation), giving you additional days of track time on the same tires, assuming there is usable rubber left.
2d - you can buy a set of takeoffs for ~$500-$600; you will usually have 2/3 of the heat cycles left in them. Similar tire setup will run at least $1,000-$1,200 new, but your selection will be limited to the offering of the reseller.

Performance
3. I think this one is a wash. Many competitive teams, including the Pirelli World Challenge M235iR cars run 18" square setup. Some may argue that 19" tires have a superior wall stiffness, resulting in less tire roll. There may be other arguments and I am interested in hearing those.

Practicality
4. If you invested in a big brake kit or are considering one, tour wheel choice may be impacted based on which BBK manufacturer you chose. However, most manufacturers kits are by design compatible with 18" wheels.

5. Weight - 18" vs 19" wheel/tire combo will generally save 2.5-5 pounds of rotational weight per wheel, 10-25 pounds total, which translates to roughly 20-50 pounds weight savings of sprung weight (assuming 1:2 ratio of sprung to unsprung weight for argument's sake - meaning a weight saving of one pound on a sprung component is an equivalent of saving two pounds on an unsprung component). Of course, one can buy expensive 19" wheels made of exotic materials that can be significantly lighter than 18" wheels, but I am assuming a budget of roughly $500/wheel, and not $2000/wheel or more. I created a spreadsheet to track a variety of tire 18" and 19" Bridgestone RE71R tire sizes and dimensions, including contact patch and weight, as well as sample wheel weight (I used APEX wheels as an example) - https://docs.google.com/spreadsheets...it?usp=sharing

6. Aesthetics - least, but somewhat important, as you will live with tour buying decision for months and years to come. 18" wheels are arguably still more popular for racing purposes, and there is a great, if not better, selection of competition wheels in this size that are pleasing to the eye.

Thanks for reading and I look forward to your input!

Last edited by landapanda; 11-21-2018 at 08:56 AM. Reason: URL Added
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      11-21-2018, 05:40 PM   #2
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I’ve run a lot of different 18” & 19” combos.

1. I’ve never noticed an impact to running different diameters with MDM on or DSC completely off. Altho, the general rule is you should not run a shorter diameter in the rear vs the front.

2. My 19” VMR V710FF’s were cheaper than my 18” Apex EX-7s. 19” tires are a little more expensive, but you’re usually buying more rubber and width to go with it. If you’re driving the car in a balanced manner (not plowing, using throttle to turn), I’ve found the front & rear tires on a 19” staggered setup wear quite evenly. I don’t find take offs worth it, as you’re spending time/paying for mount & balance more often.

3. Most any square setup on a car with decent hp, whether for DE or racing, is purely for cost savings. The speed of our cars is rear traction limited bc of all the torque we can generate. Larger rear width vs the front will always be faster. My 19” staggered setups on similar rubber were 1-2sec quicker on a track.

4. Plenty of good BBK’s that fit both 18” & 19” wheels.

5. I find this completely overblown unless you’re a top tier driver in a sprint race. Few of us have the skill to maximize the performance of the car lap after lap to make up for the few tenths of a second any additional weight would add.

6. I like the way 19’s fill the wheel well more than 18’s. No wrong choice here, tho.
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      11-21-2018, 07:09 PM   #3
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One thing to consider is if you end up trading your 2018 and earlier M2 on a 2019 comp (or the CS that's coming) a 18 inch wheel won't fit over the brakes.
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      11-22-2018, 01:12 PM   #4
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Quote:
Originally Posted by ChrisM2 View Post
One thing to consider is if you end up trading your 2018 and earlier M2 on a 2019 comp (or the CS that's coming) a 18 inch wheel won't fit over the brakes.
Wheel and tire selection is more limited in 19 (at least for now). If I had a choice, Id go with 18.
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      11-22-2018, 02:48 PM   #5
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Quote:
Originally Posted by ZM2 View Post
I’ve run a lot of different 18” & 19” combos.

1. I’ve never noticed an impact to running different diameters with MDM on or DSC completely off. Altho, the general rule is you should not run a shorter diameter in the rear vs the front.

2. My 19” VMR V710FF’s were cheaper than my 18” Apex EX-7s. 19” tires are a little more expensive, but you’re usually buying more rubber and width to go with it. If you’re driving the car in a balanced manner (not plowing, using throttle to turn), I’ve found the front & rear tires on a 19” staggered setup wear quite evenly. I don’t find take offs worth it, as you’re spending time/paying for mount & balance more often.
What different 19" have you tried, can you list a few for the m2c guys? Im struggling..
Offsets, wheel and tire specs and spacers used please.

I see from another thread you had 265/30/19 & 295/30/19 Trofeo R’s on the VMR V710FF, did you use spacers? what were the offsets

Last edited by Proctor750; 11-22-2018 at 02:54 PM.
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      11-22-2018, 04:44 PM   #6
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Quote:
Originally Posted by Proctor750 View Post
What different 19" have you tried, can you list a few for the m2c guys? Im struggling..
Offsets, wheel and tire specs and spacers used please.

I see from another thread you had 265/30/19 & 295/30/19 Trofeo Rs on the VMR V710FF, did you use spacers? what were the offsets
The Max Rubber thread has all the specs. Check it out there so I dont muddy the 18 vs 19 question by the OP.

As for 19 tires, Trofeo R, Hoosier R7, R888R, PSC2, RE-71R are all options. The best performance bang for the buck is 255/35/19 & 285/35/19 RE-71R on the stock rims. No one will have more grip unless theyre running R7s.
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      11-22-2018, 10:55 PM   #7
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Quote:
Originally Posted by ZM2 View Post
The Max Rubber thread has all the specs. Check it out there so I dont muddy the 18 vs 19 question by the OP.

As for 19 tires, Trofeo R, Hoosier R7, R888R, PSC2, RE-71R are all options. The best performance bang for the buck is 255/35/19 & 285/35/19 RE-71R on the stock rims. No one will have more grip unless theyre running R7s.

I love the RE71 although they can't take the abuse like the rs4 on the e30.
I guess ill end up staggered which I hoped to avoid but the torque just won't allow square setup. No shot at stock wheels, the width and weight isn't going to work.
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      11-23-2018, 07:32 AM   #8
landapanda
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Look at my spreadsheet at the top of the thread. You can get to the wider tires with stock OEMs rims, but you will sacrifice little bit of thread width this way. Ideally you are going to 9.5 and 10.5(or 11) rim width, but don't have to if you don't want to buy another set of rims.
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      11-23-2018, 01:02 PM   #9
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Quote:
Originally Posted by Proctor750 View Post
I love the RE71 although they can't take the abuse like the rs4 on the e30.
I guess ill end up staggered which I hoped to avoid but the torque just won't allow square setup. No shot at stock wheels, the width and weight isn't going to work.
Yeah, RE-71R doesnt last as long as the RS4, but the grip!

Im going to try 265/35 & 305/30 RE-71R as my next round of tires on my VMRs. Well see if the rear fits and how to car handles. I dont think you need that much tire in the rear with stock power, but Im now running the DINAN Stage 4 setup, so more helps.
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      11-23-2018, 02:56 PM   #10
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Quote:
Originally Posted by ZM2 View Post
Quote:
Originally Posted by Proctor750 View Post
I love the RE71 although they can't take the abuse like the rs4 on the e30.
I guess ill end up staggered which I hoped to avoid but the torque just won't allow square setup. No shot at stock wheels, the width and weight isn't going to work.
Yeah, RE-71R doesn’t last as long as the RS4, but the grip!

I’m going to try 265/35 & 305/30 RE-71R as my next round of tires on my VMR’s. We’ll see if the rear fits and how to car handles. I don’t think you need that much tire in the rear with stock power, but I’m now running the DINAN Stage 4 setup, so more helps.
Would love to hear how that setup works. RE71Rs don't come in 295/35/19, so next step down is 285/35.
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      12-06-2018, 07:30 PM   #11
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Have you considered OEM base F80/82 style 513m wheels? Same width and offset as the OEM M2 19's, but in a lighter (and more attractive IMO) 18" forged wheel. I bought my set used on the F8x forum for $1500 shipped with good tread MPSS.

If you wanted to run a square setup you could probably pick up 2 sets and run all 4 rear wheels with a bunch of camber in the front, and sell the remaining 4 front wheels to someone with a narrow body 3 or 2 series.
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      12-07-2018, 08:20 PM   #12
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Quote:
Originally Posted by dubzz24 View Post
Have you considered OEM base F80/82 style 513m wheels? Same width and offset as the OEM M2 19's, but in a lighter (and more attractive IMO) 18" forged wheel. I bought my set used on the F8x forum for $1500 shipped with good tread MPSS.

If you wanted to run a square setup you could probably pick up 2 sets and run all 4 rear wheels with a bunch of camber in the front, and sell the remaining 4 front wheels to someone with a narrow body 3 or 2 series.
Appreciate the post. Will take a look at those wheels.
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