Square Roadstar Setup (Z3 M RDSTR)

[jbrannon7]

My understanding is the Hard Dog bar interferes with the hard top mounting points.

[z3papa]

Joe is correct. Harddog does not work with hard top. The now unobtainium HMS roll bar will work but good luck finding it.

[cutthegordian]

Still looking for 17x9's - crossing fingers for a summer group buy .

Meanwhile, i've spotted a used square setup for 18x9 and 18x10 (more popular on e36's). Anyone comments or links on this setup? 255's or 245's? etc.

Thanks there.

[dudabubba]

I have a 99 Z3 M Coupe. I wanted a square set-up for the track. Here's what I got:
-Apex wheels, model EC-7, 18"x9" ET31 offset.
-25mm spacer on rear hubs
-Falken Azenis RT615K+ tires, 245/40/ZR18
-Ground Control Sport camber plates up front with about 3 degrees negative.
-Bilstein Sport (not-coilovers) and H&R springs. Car sits about 1.5" lower than stock.
I just put these wheels/tires on this week and am still figuring it out. There's no issue in the rear. The fronts are rubbing a section of the plastic wheel well. I don't see that the front wheels/tires are hitting anything else (fender, shocks, brakes...). The section they are rubbing only occurs as the wheels start to turn about 5 degrees in. There is a plastic section in the wheel well which bumps out a little. If standing at the drivers side wheel, it's located at about 10 o'clock and just a couple inches in from the fender.
I hope this is all the issues I'll encounter. I've got some track days in a couple weeks so I'll learn how this set-up really performs.
I was in love with the EC-7 wheels and they don't come in 17". I also want to settle on Falken Azenis as my track tires. These are a great deal at less than $200 each.
In retrospect, a good option may have been Apex ARC-8 in 17" and Azenis 255/40 all around. This wheel/tire would be .5" smaller diameter. But this may have had other issues in the front width being .5" wider.

[PbFut]

I have a 99 Z3 M Coupe. I wanted a square set-up for the track. Here's what I got:
-Apex wheels, model EC-7, 18"x9" ET31 offset.
-25mm spacer on rear hubs
-Falken Azenis RT615K+ tires, 245/40/ZR18
-Ground Control Sport camber plates up front with about 3 degrees negative.
-Bilstein Sport (not-coilovers) and H&R springs. Car sits about 1.5" lower than stock.
I just put these wheels/tires on this week and am still figuring it out. There's no issue in the rear. The fronts are rubbing a section of the plastic wheel well. I don't see that the front wheels/tires are hitting anything else (fender, shocks, brakes...). The section they are rubbing only occurs as the wheels start to turn about 5 degrees in. There is a plastic section in the wheel well which bumps out a little. If standing at the drivers side wheel, it's located at about 10 o'clock and just a couple inches in from the fender.
I hope this is all the issues I'll encounter. I've got some track days in a couple weeks so I'll learn how this set-up really performs.
I was in love with the EC-7 wheels and they don't come in 17". I also want to settle on Falken Azenis as my track tires. These are a great deal at less than $200 each.
In retrospect, a good option may have been Apex ARC-8 in 17" and Azenis 255/40 all around. This wheel/tire would be .5" smaller diameter. But this may have had other issues in the front width being .5" wider.

The rub you are describing is common and normally does not affect any other areas. I would buy a set of liners while still available to replace in the future just in case you return the car to OEM. They use to be cheap. You should be able to fit a 255 in there as well if you have adjustable camber. Space so the wheel/tire just misses the strut housing and run about -3 to -3.5 degrees camber. Others say 275 will fit if the profile is low enough but you get too much rub for my comfort level. I run 275 square on 10" wheels with net 10 to zero offset but the front is now flared out about 1.5 inches.
255 square is the best for an OEM motor. Best balance between weight and horse power. If you up the HP to ~400 and your speed rises, you need the bigger 275 tire to keep from over heating the rubber.

[TurboBimmer]

The rub you are describing is common and normally does not affect any other areas. I would buy a set of liners while still available to replace in the future just in case you return the car to OEM. They use to be cheap. You should be able to fit a 255 in there as well if you have adjustable camber. Space so the wheel/tire just misses the strut housing and run about -3 to -3.5 degrees camber. Others say 275 will fit if the profile is low enough but you get too much rub for my comfort level. I run 275 square on 10" wheels with net 10 to zero offset but the front is now flared out about 1.5 inches.
255 square is the best for an OEM motor. Best balance between weight and horse power. If you up the HP to ~400 and your speed rises, you need the bigger 275 tire to keep from over heating the rubber.

Good information PbFut.
I'm planning on modding my Z3 and putting it on the track with higher HP. Do you know if the front fenders can be rolled to clear 275s without going to racing fiberglass hood?
Yours is flared, do you mean rolled?
And of course, I want to see pictures of your car :-)

[PbFut]

Don't do 275 unless you really need the heat management. 275 is a lot heavier and the energy to spin up or slow down the wheel is noticable on track to a point that the 255 tire is often faster per lap. Even with 400/400 rear wheel power I feel the difference. My problem is that a 255 tire is too small and heats up too much most of the time otherwise I'd run 255. Also, if you measure a hoosier 255/35/18 it is almost the same width as the 275. There are tricks to get past some of the classing rules.
My build is 15 yrs old, so aftermarket stuff was easier to find. I used a fiberglass hood sourced local so no shipping at a cost of 300 bucks and sold the metal OEM hood for 850. Dropped a small amount of weight and made flaring the wheel opening very easy working the fiberglass. So Cal surfboard experience. I can't recall 100% for sure, but I don't think I needed to roll anything with 255. Also, you need to take into account tire cost. Buying 5 or 6 sets a year adds up when the tires are 20 or 30 bucks a unit more.
Rolling the fender is pretty easy if you see cuts on the tire. Wait for a very hot day. work metal pipe around the lip using the tire as a pry point. Go slow to avoid cracking or chipping off the paint.
Pics of car are everywhere but in my possession. Some really old build info on the LS swap at PbFut.com There's also an old walk-around video on you tube. I have know idea where.

[TurboBimmer]

Don't do 275 unless you really need the heat management. 275 is a lot heavier and the energy to spin up or slow down the wheel is noticable on track to a point that the 255 tire is often faster per lap. Even with 400/400 rear wheel power I feel the difference. My problem is that a 255 tire is too small and heats up too much most of the time otherwise I'd run 255. Also, if you measure a hoosier 255/35/18 it is almost the same width as the 275. There are tricks to get past some of the classing rules.
My build is 15 yrs old, so aftermarket stuff was easier to find. I used a fiberglass hood sourced local so no shipping at a cost of 300 bucks and sold the metal OEM hood for 850. Dropped a small amount of weight and made flaring the wheel opening very easy working the fiberglass. So Cal surfboard experience. I can't recall 100% for sure, but I don't think I needed to roll anything with 255. Also, you need to take into account tire cost. Buying 5 or 6 sets a year adds up when the tires are 20 or 30 bucks a unit more.
Rolling the fender is pretty easy if you see cuts on the tire. Wait for a very hot day. work metal pipe around the lip using the tire as a pry point. Go slow to avoid cracking or chipping off the paint.
Pics of car are everywhere but in my possession. Some really old build info on the LS swap at PbFut.com There's also an old walk-around video on you tube. I have know idea where.

Thank you for the info.
I see what you mean with the weight of the 275 vs 255s. I experienced the same on my turbocharged E30. I lost in straight line, but gained in curves. The Z3 won't be modified as much as the E30, I want to keep some street manners and creature comfort. I will go with 255s square, but with added power, may be the rear will need wider to put power to the ground. I'm planning running NT01.

I found pictures of your build on your website. It's a nice project, congrats.

[mercedesc63]

So I’ve been down this road was going to pull the trigger on a set of BBS CHR 18” 18x8.5 ET 38 i believe.. i was going to run a 255/35 all around (perfect fit for 9” but not such a good fit 8.5). I decided against it because it was going to require like 30mm spacers rear which is a joke and somewhat risky. On the Z3/Z3Ms they have a really sunken in rear axel so low offset in rear is normal but makes hard to find wheels. OEM roadstar square setup wont work and will look funny so take that off your list.

for reference my car is a 2002 bmw m coupe and i run a staggered setup hre 445r 18x8.5 et 41 245f/285r 18x10 et 20 . Looks better and drives about the same with the big front tire minus the rotating advantage of square setup. A good alignment can be your tiresaver as that really is what wears them down anyways.

[solimans]

Thank you for the info.
I see what you mean with the weight of the 275 vs 255s. I experienced the same on my turbocharged E30. I lost in straight line, but gained in curves. The Z3 won't be modified as much as the E30, I want to keep some street manners and creature comfort. I will go with 255s square, but with added power, may be the rear will need wider to put power to the ground. I'm planning running NT01.

I found pictures of your build on your website. It's a nice project, congrats.

Hi sir, bit off topic question if I may...love the exhaust (tips) on your e30. What exhaust is that!?

[solimans]

With fitment issues (when I was looking for rims) I found it helpful to calculate “front spacing”. U see back spacing and offset all the time but not front spacing.

If u know offset and the width of the rim...


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[TheDrip]

"Front spacing" is sometimes referred to as "poke". You will never see it in wheel manufacturer's specs, but often see it on fitment calculators.

[dudabubba]

So I had my track weekend and wouldn't rave about my 18" set up (as far as fitment). It felt great! Car handles fabulously but my front fender liners are a mess. As a reminder, I have a square Apex EC-7 (et31) 18"x9" with Faulken Azenis 245/40 all around. The plastic bump in my wheel well liner (at 10 o'clock) was completely rubbed down to expose a headlight connection. The upper outside edges of the liners were worn down soo much the wheel was actually leaving marks on the underside of my hood where it covers the wheel well.
My springs are pretty stiff but I'm sure not the stiffest. Coil-overs and race springs could certainly help, but overall, I would recommend anyone looking for a square track set-up on an M coupe to stick to a 17" wheel.
Just my luck, I slammed into a pothole on a county road with these wheels. Dented passenger front and rear. Rear was soo bad the tire wouldn't hold pressure. This happened as I came back from dinner on HPDE day 1. Cost me day 2.
I'll probably get these wheels repaired, sell them and get 17". Sure costs a lot of money to pretend your a race car driver!