Widest Tire/Wheel Experiment: Anyone have a 5mm Spacer?

[nilfinite]

Just spent an afternoon plugging numbers into a tire and wheel calculator to figure out how to fit the widest tire/wheel on our Z4.

It's pretty clear that the front of the Z4 is the biggest limiting factor. The rear can fit up to a 10" wheel with 275 tires.

After doing extensive calculations comparing a bunch of different wheel/tire configs posted on the forums, I think it's possible to fit a 255 tire in the front.

Compared to the stock wheels, in the front we have about 11mm to the fender. To the shocks, it's somewhere in the mid 20s.

It just so happens that the rear wheel/tires that come stock with the M Sport will fit perfectly in the front with the addition of 5mm spacers. They'll be 9mm closer to the fender and 21mm closer to the shocks. Anyone have 5mm spacers and want to try confirm that 255 won't rub in the front?

[nicknaz]

I think the widest front our community has confirmed so far is 245

http://e89.zpost.com/forums/showpost...3&postcount=18

One semi obvious thought is you might want to measure the tire you are using. The 235/265 dunlop zii I'm using now run more than 10mm wider than the stock 225/255 RFT and at the clearances you are describing, the difference between stated and actual might make a difference

[nilfinite]

So turns out someone has run 255 in the front before.

Got this email from the Apex guys:
"There was a customer that used the EC-7's on their car in the 18x9" ET31 fitment all around with 255/35/18 Hankook RS-3's with maxxed out front negative camber. They told us that there was no rubbing unless going over a very large dip, which is rare, and they believe it's due to the Hankook RS3 running much wider than an average street tire. This would be a great fitment for your car, providing a Profile 2 in the front and the rear. "

http://europeanautosource.com/blog/a...on-e89-z4.html

He had rubbing because he was 13mm closer to the fender. He should have run ET35 instead of ET31.

Another guy ran 245 tires on BBS LM wheels that are 22mm closer to the fender and said he only rubbed on the first day. http://e89.zpost.com/forums/showpost...6&postcount=17

Really good point about measuring the actual tire width. Some tires are much wider than others.

I do feel comfortable that we have at least 15mm of fender clearance with wide tires and the right offset wheels based on the BBS LM guy. (22mm - 2mm to avoid rubbing on first day - 10mm/2 assuming he was using an extra-wide tire = 15mm fender clearance). 9mm should be safe.

[nicknaz]

nice find! Maxed out might mean aftermarket camber plates. I don't have my car's alignment sheet handy but I believe max from the factory is -1 degree only. With the 235 dunlops, it seems like it is getting close to rub when the suspension is fully compressed

Also, for the 275 rear, I think measuring is needed there too.

I checked on the 265 dunlop zii on my car (-1.6 degree rear camber, stock 18s, stock sport suspension) and when the rear is very compressed the tire just barely clears the lip of the fender

post pics when you are done! sounds like you have a really nice setup in the works. 255 square setup would be very nice, although I'm not complaining with the 235/265 setup I have right now, along with less toe in for the rear and the camber settings I mentioned above.

[nilfinite]

Thanks! I'm local to the Apex guys so I'm going to see if they'll let me experiment to find the right fit.

[Nkc]

I run 20's sometime with 245 front and 295 rears. The rears rubs sometime but not to a level that bothers me.

[nilfinite]

Originally Posted by Nkc

I run 20's sometime with 245 front and 295 rears. The rears rubs sometime but not to a level that bothers me.

Cool! Thanks for your input. Mind sharing your wheel and tire specs? I'm curious how much room we have in the rear.

[Nkc]

Originally Posted by nilfinite

Cool! Thanks for your input. Mind sharing your wheel and tire specs? I'm curious how much room we have in the rear.

Wheels are Vossen CV2 20x9 in the front with 245/30/20 Continental Extreme Contact DW
In the rear, 20x10.5 with 295/25/20 same tires.

Not much room in the rear with the Eibach springs. My rear fenders are thoroughly rubbed and shredded but it doesn't bother me.

[Ramjet]

Originally Posted by Nkc

Wheels are Vossen CV2 20x9 in the front with 245/30/20 Continental Extreme Contact DW
In the rear, 20x10.5 with 295/25/20 same tires.

Not much room in the rear with the Eibach springs. My rear fenders are thoroughly rubbed and shredded but it doesn't bother me.

post a picture, would like to see it. I want 295's on my back end but not sure on the fit.

[nilfinite]

Originally Posted by Nkc

Wheels are Vossen CV2 20x9 in the front with 245/30/20 Continental Extreme Contact DW
In the rear, 20x10.5 with 295/25/20 same tires.

Not much room in the rear with the Eibach springs. My rear fenders are thoroughly rubbed and shredded but it doesn't bother me.

Thanks! Do you also by chance have the offsets specs on the wheels?

[nilfinite]

Also, sad news. Was rereading an old thread and saw that someone tried 255 tires with ET43 offset that didn't work.

http://e89.zpost.com/forums/showpost...82&postcount=6

He hit the shock so much that he believes ET35 wouldn't work. I personally believe it would after plugging in the configuration to tire and wheel calculator but its another data point. But I won't be the one to figure out if it works or not unfortunately due to SCCA rules.

I was rereading the SCCA rules and forgot that in street class I can't get a wider wheel than stock. So I'm going to make due with the stock setup and do 8" wheels square on 215/45/17 tires. With AX, it's best to match wheel width with thread width. 8" = 203mm. There aren't any good tires in 205/50/17 or 205/45/18 so I'm going to go with 215 tires.

[Hujan]

Originally Posted by nilfinite

Thanks! I'm local to the Apex guys so I'm going to see if they'll let me experiment to find the right fit.

I think it would be sweet if you headed over there and let them snap some pics of your E89 with different Apex wheels on your car, preferably in 18 inches, preferably in Hyper Silver, preferably Arc-8s.

[Xpuzzle]

Originally Posted by Hujan

I think it would be sweet if you headed over there and let them snap some pics of your E89 with different Apex wheels on your car, preferably in 18 inches, preferably in Hyper Silver, preferably Arc-8s.

+1

[Drew@Sonic MS]

Front I have a 265/30/19 PSS and I'm slammed.

[nicknaz]

Originally Posted by nilfinite

Also, sad news. Was rereading an old thread and saw that someone tried 255 tires with ET43 offset that didn't work.

http://e89.zpost.com/forums/showpost...82&postcount=6

He hit the shock so much that he believes ET35 wouldn't work. I personally believe it would after plugging in the configuration to tire and wheel calculator but its another data point. But I won't be the one to figure out if it works or not unfortunately due to SCCA rules.

I was rereading the SCCA rules and forgot that in street class I can't get a wider wheel than stock. So I'm going to make due with the stock setup and do 8" wheels square on 215/45/17 tires. With AX, it's best to match wheel width with thread width. 8" = 203mm. There aren't any good tires in 205/50/17 or 205/45/18 so I'm going to go with 215 tires.

Why are you going that narrow? 205 wide is narrow that what I would want to run for winter tires

How about just using stock 18" wheels and go with tires that are 235 front and 265 rear in width? That will work for sure and be compliant for the stock class rules.

EDIT: drew do you have camber plates / what are your front camber settings and wheel offset?

[Drew@Sonic MS]

Camber plates - yes and set at -2.5. Running 9.5 + 20 in the fronts.

[nilfinite]

Originally Posted by Drew@Sonic MS

Front I have a 265/30/19 PSS and I'm slammed.

Originally Posted by Drew@Sonic MS

Camber plates - yes and set at -2.5. Running 9.5 + 20 in the fronts.

Niiiccceee. Thanks for letting us know. So it looks like we do have more space before hitting the fender than I thought. The key is getting tires that are close to the same diameter as the originals.

Both of the guys with rubbing got tires that were 20-40mm taller than the stock 19" tires. 265/30/19 is just 6mm taller than the stock 225/40/18 tires.

[nilfinite]

Originally Posted by nicknaz

Why are you going that narrow? 205 wide is narrow that what I would want to run for winter tires

How about just using stock 18" wheels and go with tires that are 235 front and 265 rear in width? That will work for sure and be compliant for the stock class rules.

EDIT: drew do you have camber plates / what are your front camber settings and wheel offset?

Before the street tire changes, the rule of thumb for everyone was to squeeze as much tire on the wheel as you can. This was true when everyone was using R-comps in the stock classes.

Now that everyone is using tires with 200 TW and above, more testing has shown that it's important to match the width of the wheel to the width of the tire thread. Extra tire width is just wasted. But it does depend on the tire. Tires with stiffer sidewalls can handle being squeezed onto smaller wheels better.

Here is a link that summarizes testing done by Andy Hollis. https://m.facebook.com/notes/furrin-...7525144633438/

But one thing I completely forgot... The stock wheels that I have are 18" not 17" lol. So that means I have to go with 225/40/18. No good 205 or 215 tires that fit a 18" wheel. Probably more rubber than I need but it's only option for 18" wheels.

[nicknaz]

Originally Posted by nilfinite

Before the street tire changes, the rule of thumb for everyone was to squeeze as much tire on the wheel as you can. This was true when everyone was using R-comps in the stock classes.

Now that everyone is using tires with 200 TW and above, more testing has shown that it's important to match the width of the wheel to the width of the tire thread. Extra tire width is just wasted. But it does depend on the tire. Tires with stiffer sidewalls can handle being squeezed onto smaller wheels better.

Here is a link that summarizes testing done by Andy Hollis. https://m.facebook.com/notes/furrin-...7525144633438/

But one thing I completely forgot... The stock wheels that I have are 18" not 17" lol. So that means I have to go with 225/40/18. No good 205 or 215 tires that fit a 18" wheel. Probably more rubber than I need but it's only option for 18" wheels.

My take away is that it is not that straight forward to just say "Extra tire width is just wasted". They noted that some tires like the Dunlop ZII are fine for wider tire on narrow wheel, for example. In the comments someone noted the RTA winner used 265 wide tires in a 9" wheel and RTR was 225 wide tires on a 7" wheel, and there was also a comment about a soft/oem suspension vs. stiffer suspension

Which is to say, I still think dunlop ZII 235 wide front and 265 wide rear on the stock 18s is a fine idea

[nilfinite]

Originally Posted by nicknaz

My take away is that it is not that straight forward to just say "Extra tire width is just wasted". They noted that some tires like the Dunlop ZII are fine for wider tire on narrow wheel, for example. In the comments someone noted the RTA winner used 265 wide tires in a 9" wheel and RTR was 225 wide tires on a 7" wheel, and there was also a comment about a soft/oem suspension vs. stiffer suspension

Which is to say, I still think dunlop ZII 235 wide front and 265 wide rear on the stock 18s is a fine idea

Haha you are probably right, but I'd like to try a narrower tire for now and might experiment with more rubber mid-season. Main reason for the same tire size front and back is to decrease grip in the rear and make it easier to oversteer with the throttle when I need it. I'm driving the 28i.

If 225 doesn't work out, I'll be sure to try 235 mid year and see how it works.

Can't wait for the new AX season to start!

[nicknaz]

Originally Posted by nilfinite

Haha you are probably right, but I'd like to try a narrower tire for now and might experiment with more rubber mid-season. Main reason for the same tire size front and back is to decrease grip in the rear and make it easier to oversteer with the throttle when I need it. I'm driving the 28i.

If 225 doesn't work out, I'll be sure to try 235 mid year and see how it works.

Can't wait for the new AX season to start!

I changed the rear toe (closer to zero) and camber (a bit less negative) to achieve something similar with making the rear rotate more. I personally thought it was a better way to go about it since I want the traction for accelerating in a straight line

EDIT: I measured a 265/35/18 dunlop zii today by laying it on the floor and putting a ruler next to it. it was ~290mm from edge to edge of the shoulders.