E92 M3 ZCP in SCCA Solo F Street

[z3papa]

Originally Posted by CSBM5

What you're thinking about here is running 275/35-18 front and 305/30-19 rears?

I'm guessing he's talking about using 275/35-19 with stock ZCP fronts as 18's would make a much smaller diameter. I just know that when I still had my ZCP wheels, the difference in acceleration out of corners was very noticeable and even more so when I use my set of 285/30's over 275/35. One thing you give up though with 285's which is often overlooked beyond top speed in 2nd is sidewall compliance of the taller sidewall. On rough surfaces, it translates more surface imperfections through the wheel to the suspension.

[CSBM5]

Originally Posted by z3papa

I'm guessing he's talking about using 275/35-19 with stock ZCP fronts as 18's would make a much smaller diameter. I just know that when I still had my ZCP wheels, the difference in acceleration out of corners was very noticeable and even more so when I use my set of 285/30's over 275/35. One thing you give up though with 285's which is often overlooked beyond top speed in 2nd is sidewall compliance of the taller sidewall. On rough surfaces, it translates more surface imperfections through the wheel to the suspension.

Don't think the 275/35-19 will fit up front as the diameter is too large. I run 255/35-19 (one step larger than OE) up front on my street tires, and it's already tight to the fender liner. The 275/35-18 is exactly the OE diameter (i.e. identical to the 245/40-18).

[z3papa]

Originally Posted by CSBM5

Don't think the 275/35-19 will fit up front as the diameter is too large. I run 255/35-19 (one step larger than OE) up front on my street tires, and it's already tight to the fender liner. The 275/35-18 is exactly the OE diameter (i.e. identical to the 245/40-18).

Ah I see that. Terrible to think I bookmark the specs page for RE71R's.

[z3papa]

Update -- well you can get 285's on a 9" wheel but it's a major PITA for the installer who you better be prepared to give gratuities for if they encounter what mine did. It took 2 hours to do the fronts, and 30 minutes for the rears. Pics will follow.

[dnoble37]

Originally Posted by z3papa

Update -- well you can get 285's on a 9" wheel but it's a major PITA for the installer who you better be prepared to give gratuities for if they encounter what mine did. It took 2 hours to do the fronts, and 30 minutes for the rears. Pics will follow.

Yessss. You are talking about a re71r 285/30r18 right?

Who did the install for you?

Then I guess the magic question is, how does it perform in AX conditions? Report back after your next event.

[z3papa]

Originally Posted by dnoble37

Yessss. You are talking about a re71r 285/30r18 right?

Who did the install for you?

Then I guess the magic question is, how does it perform in AX conditions? Report back after your next event.

yes RE71R. Install was done by Peoria Tire and Vulcanizing although they might not ever want me back despite many prior purchases after today. My plan is at the next Chicago SCCA event where Jeff Cashmore (I don't accurately know how many DM Nat'l jackets) and Sam Karp will be running (good comparables), I'll test the 265 vs. 285 front with 285 rears to get a decent comparison. Only downfall is they run a 3+3 format which means afternoon runs especially if you are running 1/3 vs. 2/4 will be a bit skewed. I have a TNT the day before which will give me a better appreciation of the difference or lack thereof. For the record, the't ey were supposed to mount another set of 265's on another pair of fronts but didn't. Not sure why but didn't press them as they seemed a bit irritated as they top tire guy wasn't there. As such, I had separated wheels/tires for the ride home, and no shenanigans. The fronts seemed really responsive even with the standard mold release. Very tight turn in at speeds.

[Richbot]

Originally Posted by CSBM5

Don't think the 275/35-19 will fit up front as the diameter is too large. I run 255/35-19 (one step larger than OE) up front on my street tires, and it's already tight to the fender liner. The 275/35-18 is exactly the OE diameter (i.e. identical to the 245/40-18).

The sidewall issue with the 285 is exactly what got me thinking "why not both" with diameters on an FS M3 that and national courses routinely peaking above 70mph means the 285 could have you making a few too many 2-3 shifts right at the moment when the M3 is finally accelerating as hard or harder than anything else in the class (7500+rpm in 2nd). So what chuck was saying about the sidewalks on the 285's is wahat I was getting at and yeah the extra width is nice on the 305/30-19 but you also get a tire that can put ALL the power down ALL the time

Just not sure if getting the balance right would be possible with all that meat back there

[Rassilon]

Anybody has experience with the difference lightweight wheels like arc-8 make compared to stock ones?

[z3papa]

Originally Posted by edwardgtxy

Anybody has experience with the difference lightweight wheels like arc-8 make compared to stock ones?

What would you like to know? Presently I have two sets of Apex ARC8's (one for my car and one for my wife's but have owned several sets from my prior STR build) and one set of EC7's (after selling a second set). Both wheel sets are substantial lighter than the 359's.

[Rassilon]

Originally Posted by z3papa

What would you like to know? Presently I have two sets of Apex ARC8's (one for my car and one for my wife's but have owned several sets from my prior STR build) and one set of EC7's (after selling a second set). Both wheel sets are substantial lighter than the 359's.

Cool, the ARC8 are 7lbs lighter than stock per wheel right? That looks like a big difference on paper. I am curious if there is any measurable benefit in time for these lightweight wheels? Or they are more like a feel mod that improves responsiveness but would not have much impact on time. I am getting a new set of tires and am wondering whether these apex wheels are worth it.

[FS71]

Hey Guys, I have been co driving a 2011 M3 ZCP this year. I spent a year and a half driving a 335i pretty competitively locally. I made the last trophy spot (3rd) in FS at the College Station Tour. I had second in my grasp but I botched my last run Sunday. Just wanted to introduce myself. I'm hoping to make it to Nationals this year.

To respond to the issue of 7lbs lighter a wheel, that is huge. It's rotational and unsprung mass. I dropped over a second just changing to lighter wheels on my 335i for reference, thats having re71r's on my stock wheels and then my on my aftermarket wheel. F=MA. less mass, with the same force = more acceleration.

[z3papa]

Originally Posted by edwardgtxy

Cool, the ARC8 are 7lbs lighter than stock per wheel right? That looks like a big difference on paper. I am curious if there is any measurable benefit in time for these lightweight wheels? Or they are more like a feel mod that improves responsiveness but would not have much impact on time. I am getting a new set of tires and am wondering whether these apex wheels are worth it.

While I loved the look of my ZCP wheels, 7# is a lot of unsprung weight not just in acceleration but also braking, and 19" tires are more expensive consumables. Hell I'd go to 17x9/17x10 wheels if they had the top tier tires in the sizes I want and the offsets were legal but you can't drop 2" in diameter. It's a no brainer in my mind.

[Rassilon]

Originally Posted by FS71

Hey Guys, I have been co driving a 2011 M3 ZCP this year. I spent a year and a half driving a 335i pretty competitively locally. I made the last trophy spot (3rd) in FS at the College Station Tour. I had second in my grasp but I botched my last run Sunday. Just wanted to introduce myself. I'm hoping to make it to Nationals this year.

To respond to the issue of 7lbs lighter a wheel, that is huge. It's rotational and unsprung mass. I dropped over a second just changing to lighter wheels on my 335i for reference, thats having re71r's on my stock wheels and then my on my aftermarket wheel. F=MA. less mass, with the same force = more acceleration.

Wow a second is huge. Same tire size?

Welcome, how would you compare 335i with m3? I got owned by a 335i with dws in freezing rain and when I rode his car it felt very similar to a M3 and the turbo engine with a tune has really good torque.

[FS71]

Originally Posted by edwardgtxy

Wow a second is huge. Same tire size?

Exact same tires, dismounted from my stock wheels and moved over.

[Rassilon]

Originally Posted by FS71

Exact same tires, dismounted from my stock wheels and moved over.

My mind is blown.. which wheel do you have?

[FS71]

Originally Posted by edwardgtxy

My mind is blown.. which wheel do you have?

It really shouldn't be that big of a surprise. I went from stock style 162's to the Enkei Raijin. For the M3 just get the Apex ARC8 and be done with it.

[z3papa]

Originally Posted by edwardgtxy

Wow a second is huge. Same tire size?

Welcome, how would you compare 335i with m3? I got owned by a 335i with dws in freezing rain and when I rode his car it felt very similar to a M3 and the turbo engine with a tune has really good torque.

I'd be surprised if it makes a second difference, but every bit helps and you don't want to be left wondering.

As for 335 v. M3 -- I own both and can't ever see the 335i being competitive. It starts with the front chassis, the cars have different wheel allowances, and the NA is fair more linear. Obviously, the DWS are a tremendous wet/colder tire, and that could tip some scales but otherwise, no way.

[Rassilon]

Originally Posted by z3papa

I'd be surprised if it makes a second difference, but every bit helps and you don't want to be left wondering.

As for 335 v. M3 -- I own both and can't ever see the 335i being competitive. It starts with the front chassis, the cars have different wheel allowances, and the NA is fair more linear. Obviously, the DWS are a tremendous wet/colder tire, and that could tip some scales but otherwise, no way.

Maybe the width of wheel changed which give better support for the side walls?

Makes sense. I am sure in dry m3 would dominate with tire width advantage alone, but at 38f ambient and freezing rain, my stock size 4year old pss and m3's stiffer suspension felt like sking on ice, compare to the 335i with dws. Its softer suspension also helps under limited traction and low-G? Maybe I should have tried edc in comfort.

Btw do wide tire actually help in wet? I thought narrower tire help to put more pressure to break the layer of water. For you guys competing on the national level do you use 265/275 square dws06 for rain tires?

[The Nebulizer]

Originally Posted by edwardgtxy

Btw do wide tire actually help in wet? I thought narrower tire help to put more pressure to break the layer of water. For you guys competing on the national level do you use 265/275 square dws06 for rain tires?

There is debate on what is best in the rain. It likely depends on a lot of variables so you probably won't hear a consistent message. For me, my best result ever was in heavy rain (standing water everywhere) on concrete on brand new RE71Rs. I've never run a tire specifically for the rain - but I was amazed at my grip with those tires under horrendous conditions. Tread depth is the key for that tire though.

Wheels matter - 7lbs is huge. There is a rule of thumb that says, I believe, every lb. of wheel (sprung weight) is equivalent to 4 lbs. of unsprung weight. So that is 112lbs. Plus the benefits listed above of faster throttle & braking response and lighter, more responsive turning and even improved contact with the pavement. I'd think 1 second is on the optimistic side though.

[z3papa]

Originally Posted by edwardgtxy

Maybe the width of wheel changed which give better support for the side walls?

Makes sense. I am sure in dry m3 would dominate with tire width advantage alone, but at 38f ambient and freezing rain, my stock size 4year old pss and m3's stiffer suspension felt like sking on ice, compare to the 335i with dws. Its softer suspension also helps under limited traction and low-G? Maybe I should have tried edc in comfort.

Btw do wide tire actually help in wet? I thought narrower tire help to put more pressure to break the layer of water. For you guys competing on the national level do you use 265/275 square dws06 for rain tires?

Honestly, when it comes to rain tires I probably adopt the minority position of using the RE71R's even when it is really wet over Conti DW or now the Conti Extreme Sports. Four years ago, when I was still in STR I bought into the Koolade of getting Pilot Super Sports which was billed as the droid for wet traction. When to the Peru Tour, Sunday morning they have a ark inciting deluge which ended at 7:15~ with huge standing water everywhere. I had brought RS3 and the Pilot SS. My co-driver and I opted for the Pilots with STR running first car off at 8:00. Sun comes out, gets toasty, wind really starts blowing and by mid 2nd runs, there is this miraculous dry line and we were toast. I'd rather put my money on having a tire which is alright to good in the wet and great in the dry than worry about tire flips. This is resounding reinforced for anything non-Nat'l. For the record, I've driven in very heavy, standing rain on the RE71R's and was stunned at their grip levels as long as they are early in life.

[FS71]

Originally Posted by z3papa

Honestly, when it comes to rain tires I probably adopt the minority position of using the RE71R's even when it is really wet over Conti DW or now the Conti Extreme Sports. Four years ago, when I was still in STR I bought into the Koolade of getting Pilot Super Sports which was billed as the droid for wet traction. When to the Peru Tour, Sunday morning they have a ark inciting deluge which ended at 7:15~ with huge standing water everywhere. I had brought RS3 and the Pilot SS. My co-driver and I opted for the Pilots with STR running first car off at 8:00. Sun comes out, gets toasty, wind really starts blowing and by mid 2nd runs, there is this miraculous dry line and we were toast. I'd rather put my money on having a tire which is alright to good in the wet and great in the dry than worry about tire flips. This is resounding reinforced for anything non-Nat'l. For the record, I've driven in very heavy, standing rain on the RE71R's and was stunned at their grip levels as long as they are early in life.

I will second the fact the RE71r will actually do very well in the wet. Here is a video of a local event will continuous water. The tires had about 30 runs on them before this event. We have multiple National Champions and Trophy winners in our area if your wonder about how that local PAX stands up.

youtu.be/05qxw1iq5TM

[Richbot]

Under 50 degrees? Was it sunny yesterday? Run the RE71R's if they have tread. Under 50 degrees and ground's still cold, or under 40 degrees? Run a Conti DW, PSS, or whatever true street tire Unless it's really wet and lots of standing water the faster tire in the dry is probably going to be faster in the wet too. Your mileage may vary, but odds are good this will work.

See also, when to switch to slicks question. If you can drive, the earlier the better if there's no standing water

Unless you're autocrossing in <20 degree temps, using all-seasons as a rain tire just means you're going to be slower in most situations. The DWS is good for an all-season, but they call them no-seasons for a reason