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      08-20-2013, 01:29 PM   #23
SergioK
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Originally Posted by David@ApexRaceParts View Post
Upon reading this thread we saw a few comments regarding tire sizes in regards to rubbing and would like to chime in with information regarding the F30 wheel and tire fitments.

The OEM F30 Sportline wheel is 18x8" ET34, and the EC-7's are 18x9.0" ET42. The EC-7's extends an additional 5mm on the fender side, while it takes up an additional 21mm of clearance on the strut side in comparison to the Sportline wheels. Also, since the EC-7's are an inch wider, this means that they are approximately 12.5mm wider per side of the wheel (half an inch wider per side of the wheel) than the OEM Sportline wheels. What this means is that using the same tire on the two different wheels will have different results, as the sidewall characteristics of the same tires will be different between the different width wheels. This may be the reason why some have not experienced rubbing issues with the 245/40/18 tire size.

Using the 245/40/18 tire on the 18x8" ET34 wheel is oversized, and due to the tires being ballooned with a narrower wheel, the tires effectively become ~240/40/18 since the tread is pulled in as the tire bead is pulled in. This happens when a tire is mounted on a wheel that is too narrow. Additionally, there would be less sidewall support from a wheel that is too narrow creating sloppier sidewalls, which in turn causes steering response to be less nimble and makes it more difficult to drive a tire at its limits. For street use this may not be an issue, but if one is looking for performance we do recommend the proper tire size and wheel width combination.
Thank you, that is very informative!

One follow-up question. Do you know if the EC-7's clear the BMW //M Performance 4 wheel BBK brake calipers?
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      10-15-2013, 12:34 PM   #24
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Lots of good info here regarding wheel/tire choices, etc - but I haven't seen any info on tire pressures.

What PSI front/rear are you guys running at the track? I think I had my stock Conti RFTs a little too high yesterday, and they got a bit greasy by the end of the second session...
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      10-17-2013, 10:09 AM   #25
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Quote:
Originally Posted by DVC View Post
Lots of good info here regarding wheel/tire choices, etc - but I haven't seen any info on tire pressures.

What PSI front/rear are you guys running at the track? I think I had my stock Conti RFTs a little too high yesterday, and they got a bit greasy by the end of the second session...
Right tire pressure's a complicated question - different pressures work for different tires and different surfaces. Then you might want to tune the pressure to adjust balance.

So, to caveat, this is what I've learned from my 245/40/18 RE-11A's on 8" rims

Over this summer where I live (ambient temps ~70-107F) and where I autocross usually, I've run my fastest times with 38-39 psi in the tires (hot). Above that the grip falls off, below that and the tires roll over too much.

The surface is heavily graveled asphault, old WWII era - which is very grippy. If the surface you're running on has less grip, I'd drop the pressure down a few PSI. If you find somewhere that somehow has more grip, you'll need to up it to keep the tires from rolling.

Re-iterate - these are hot pressures - if it's autocross and you're cool with bleeding your tires between runs you could start there. If not you'll need to figure out the cold tire pressure that'll get your tires to the hot pressure you're looking for. For me right now ~35 cold pressure gets me there when hot, and that all depends on the air type and moisture content in the tires, wet air expands more, dry air less, bottle nitrogen even less.

Again this is my car, my tires, my setup, my alignment, my driving style, on my surface, in my conditions - what works for me. Lots of variables

I think the two best things you can do are

1) code your car so the tire display shows temperature and pressure - you can't imagine how helpful it is to be aware of the tire's core temperature and pressure as you're going. It's also a great indicator of balance and whether you're driving right or not. If the car's balanced, and you're doing it right, the temps should be about even front to back - braking too late, causing corner entry understeer, front tires will get a lot hotter b/c you're doing it wrong. Granted if you're running staggered, this likely isn't accurate

2) chalk your tires. Make 3 very visible marks from the tread up the side wall on each tire. Make your run then check the marks. If the chalk is rubbed off above where you think the road should be touching the tires, add air. If the chalk isn't rubbed off to the edge of the tread, let some out. Ideally you would do this on a 200' skid-pad of the exact surface that your running on in the exact conditions - but that's likely never possible. One good run with the tires at your target temperature should let you know if you're in the ball-park

If you want to get really into it, get a pyrometer and go to town
Here's an old video covering the subject - pretty good IMO

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      10-17-2013, 11:56 AM   #26
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Thanks UT - good info
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      10-18-2013, 03:15 PM   #27
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Quote:
Originally Posted by SergioK View Post
Thank you, that is very informative!

One follow-up question. Do you know if the EC-7's clear the BMW //M Performance 4 wheel BBK brake calipers?
Unfortunately we have not been able to source a car with the M Performance BBK. However, we have tested the Base and M Sport brakes, both of which clear the EC-7 with room to spare. While we haven’t been able to get our hands on the actual M Performance brake setup, we are sure they will fit from our testing. Despite being larger in dimension than the M Sport brakes, they fit behind the same OEM Style 400 M Sport wheels, which have less brake clearance than an EC-7.

Here are photos of the wheels with the M Sport brakes:





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      10-18-2013, 08:34 PM   #28
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Quote:
Originally Posted by David@ApexRaceParts View Post
Unfortunately we have not been able to source a car with the M Performance BBK. However, we have tested the Base and M Sport brakes, both of which clear the EC-7 with room to spare. While we havenít been able to get our hands on the actual M Performance brake setup, we are sure they will fit from our testing. Despite being larger in dimension than the M Sport brakes, they fit behind the same OEM Style 400 M Sport wheels, which have less brake clearance than an EC-7.
FWIW, my MP BBK clears Arc-8's 18x8.5 just fine.
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      10-18-2013, 08:38 PM   #29
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Quote:
Originally Posted by DVC View Post
Lots of good info here regarding wheel/tire choices, etc - but I haven't seen any info on tire pressures.

What PSI front/rear are you guys running at the track? I think I had my stock Conti RFTs a little too high yesterday, and they got a bit greasy by the end of the second session...
I run 40psi hot (160-170* w/pyrometer probe), but that's on PSS's.
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      10-21-2013, 12:23 PM   #30
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Quote:
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FWIW, my MP BBK clears Arc-8's 18x8.5 just fine.
That's great to hear, thank you for your feedback!
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      11-13-2013, 01:48 PM   #31
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has anyone tried to go wider than 245 up front yet? i would like to run a 9.5 square setup with 265's all around. I will be running camber plates. However im not sure with what offset this will be most doable. Anyone have any advice? Thanks
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      11-13-2013, 03:04 PM   #32
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Originally Posted by Ih8usrnms View Post
has anyone tried to go wider than 245 up front yet? i would like to run a 9.5 square setup with 265's all around. I will be running camber plates. However im not sure with what offset this will be most doable. Anyone have any advice? Thanks
You'd need some serious camber and/or a bit of fender modding to squeeze that much in up front. I have 9" wheels with 245 rubber up front (granted, the tires are Michelin Pilot Sport A/S 3s, which are exceptionally wide); I only have about 3.25mm of clearance from the inside of tire to the strut, and just a few mm of clearance inside the fender to keep from rubbing at full compression.
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      11-13-2013, 09:36 PM   #33
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Quote:
Originally Posted by DVC View Post
You'd need some serious camber and/or a bit of fender modding to squeeze that much in up front. I have 9" wheels with 245 rubber up front (granted, the tires are Michelin Pilot Sport A/S 3s, which are exceptionally wide); I only have about 3.25mm of clearance from the inside of tire to the strut, and just a few mm of clearance inside the fender to keep from rubbing at full compression.
thanks, what suspension are you on and also whats the offset on your wheels?
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      11-13-2013, 10:20 PM   #34
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thanks, what suspension are you on and also whats the offset on your wheels?
I have the stock Adaptive M suspension (M Sport w/ DHP) at the moment, but I did replace my stock wheel carriers with OEM BMW -30min "swivel bearing" carriers, which add 0.5 degrees of negative camber. My wheels are Apex ARC-8s (ET42 front and rear). Normally this wheel/offset would be fine, but with my camber bearings (which add negative camber at the wheel w/o changing the strut angle... therefore, they actually bring the inside/top of the tire closer to the strut), I needed to add 5mm spacers to get enough clearance at the strut for my wheel/tire setup.

Note - with these wheels/tires, without additional camber, a 5mm spacer might get the tire too close to the fender at full compression
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      11-13-2013, 10:56 PM   #35
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Quote:
Originally Posted by DVC View Post
I have the stock Adaptive M suspension (M Sport w/ DHP) at the moment, but I did replace my stock wheel carriers with OEM BMW -30min "swivel bearing" carriers, which add 0.5 degrees of negative camber. My wheels are Apex ARC-8s (ET42 front and rear). Normally this wheel/offset would be fine, but with my camber bearings (which add negative camber at the wheel w/o changing the strut angle... therefore, they actually bring the inside/top of the tire closer to the strut), I needed to add 5mm spacers to get enough clearance at the strut for my wheel/tire setup.

Note - with these wheels/tires, without additional camber, a 5mm spacer might get the tire too close to the fender at full compression
I see, thanks a lot for the info. Im thinking with more camber the 265's are possible but i will really have to get the offsets dialed in.
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      12-17-2013, 09:30 AM   #36
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Any thoughts on running 400m staggered rear wheels all around for summer/HPDEs? 18x8.5 et 47 thinking 15mm spacer front and rear and 245-40-18s. Car will be lowered on HR sports/Bilstein B8s. Anyone see issues with this setup? Kind of leery about running spacers on the track and whether the 32 offset in the front will clear. Afaik the rears need 15mm minimum spacer width trying to keep it consistent front and rear.
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      12-17-2013, 12:46 PM   #37
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Any thoughts on running 400m staggered rear wheels all around for summer/HPDEs? 18x8.5 et 47 thinking 15mm spacer front and rear and 245-40-18s. Car will be lowered on HR sports/Bilstein B8s. Anyone see issues with this setup? Kind of leery about running spacers on the track and whether the 32 offset in the front will clear. Afaik the rears need 15mm minimum spacer width trying to keep it consistent front and rear.
I have thought about doing this too... swapping my 8" staggered wheels for 8.5", and running a square setup. Being that I already bought the Apex 18x9 wheels, I would actually consider running 18x8 all around for a winter setup... Are you looking to trade your 18x8s?

By my quick calcs, you should just barely be clear of the fenders with that setup. If you wanted a little margin of error, you could go with a 12mm spacer.

Spacers are fine for the track.
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      12-17-2013, 03:34 PM   #38
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My car is coming with staggered summer setup and I bought another set of staggered wheels for it. Planning on using the 8s for winter and the 8.5s for summer. Much cheaper than buying a set of aftermarket wheels and I prefer the stock look. Thanks for the help I may try 12mm front and 15mm rear thinking about it the 3mm shouldn't have any real effect on how the car drives.
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      12-17-2013, 10:18 PM   #39
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Quote:
Originally Posted by ronin951 View Post
FWIW, my MP BBK clears Arc-8's 18x8.5 just fine.
What offsets are you running and out of curiosity what tire sizes? Trying to decide what track setup I am going to do.
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      12-18-2013, 10:31 AM   #40
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What offsets are you running and out of curiosity what tire sizes? Trying to decide what track setup I am going to do.
I have Apex ARC-8s as well, which clear my M-Sport BBK without issue. Mine are 18x9 ET 42, 245/40-18 tires; I am running 5mm spacers, but they are not necessary for brake clearance.
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      06-25-2014, 06:12 PM   #41
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Those looking to run 275 square (RS3's) setup, yes it's possible.

These are on a set of 18x9.5 with an offset of 45 with a 10mm spacer up front. No spacer is required in the rear. Dinan springs.
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      06-25-2014, 09:45 PM   #42
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Those looking to run 275 square (RS3's) setup, yes it's possible.

These are on a set of 18x9.5 with an offset of 45 with a 10mm spacer up front. No spacer is required in the rear. Dinan springs.
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      06-26-2014, 12:19 PM   #43
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Quote:
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Those looking to run 275 square (RS3's) setup, yes it's possible.

These are on a set of 18x9.5 with an offset of 45 with a 10mm spacer up front. No spacer is required in the rear. Dinan springs.
Amazing! What were your alignment specifications to fit these up front?
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      06-26-2014, 03:54 PM   #44
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Amazing! What were your alignment specifications to fit these up front?
I know Bill's got some camber plates up front, not sure what they're set at here, but I don't

I have 265/35R18 RS3's on 18x9 ET42 Apex Arc8's on the front and rear
5mm spacer in front, none in rear

H&R Sport springs, no other alteration to the suspension

They don't rub at all

Here's the car leaned over under trail braking at COTA - suspension here is pretty much as compressed as it gets

DSC_8434 by UT Enigma, on Flickr
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