[cxp213]

Why not just save the MPSS for daily driving and get a new set of wheels for the 71Rs? This is the route that most choose as it saves cost in the long run (having multiple sets).

[TajoMan]

I already have a winter set (17") and I did not want to have another set for Auto X.
I was going to use up the winter tire this coming winter and put RE71r next spring on 17" rims and just put good all season on stock 18".

Now I'm thinking just put Re71r in 17" rim right now (take out winter tires and reinstall it before winter). lol

[icin235]

Good thread.

[Shadowfax028]

Originally Posted by pikcachu

Camber in the front is fixed... you either do plates, lca or there is now some bushing you can use to add a bit of camber....

It's a bit counter intuitive but higher pressure would give better grip...

What can you tell me about those bushings to adjust camber your speaking of.

Where do you get them? How much negative camber can you get

[230iZTR]

This is maybe a silly question, but why is the 128i generally considered to be a reasonably competitive car in STX but the 228i isn't?

As far as I can tell, the weight is about the same, the amount of tire you can fit is about the same, with similar mods they should be at similar power power levels (and the 2.0T may even have an advantage with a wider powerband)?

Does the extra 1" of track width, 2" of length, (approx) 40 lbs higher minimum curb weight, and electronic vs. hydraulic steering really make that much difference?

[bbnks2]

Originally Posted by 230iZTR

This is maybe a silly question, but why is the 128i generally considered to be a reasonably competitive car in STX but the 228i isn't?

As far as I can tell, the weight is about the same, the amount of tire you can fit is about the same, with similar mods they should be at similar power power levels (and the 2.0T may even have an advantage with a wider powerband)?

Does the extra 1" of track width, 2" of length, (approx) 40 lbs higher minimum curb weight, and electronic vs. hydraulic steering really make that much difference?

A car is only as good as its driver and I think most of the better drivers shy away from touring expensive luxury cars lol. Much cheaper to "build" other cars. STX can do quite a bit of modding and the 228i (and the 128i) requires every bit of it to edge out cars that are much more sporty, and cheaper, out of the box vs a luxury car.

[230iZTR]

Originally Posted by bbnks2

the 228i (and the 128i) requires every bit of it to edge out cars that are much more sporty, and cheaper, out of the box vs a luxury car.

I agree completely. The 86 Twins are almost perfect for STX and it takes a very particular kind of course layout with long straights to give the 128i an advantage. I guess I’m just confused about why all the things that make the 128i a course-dependent monster don’t also make the 228i/230i a course-dependent monster as well? Is it really just that no one has bothered to try a proper STX build yet because a stripper of a 2 costs $35k new while a used 128i is half the cost and already has some proven builds?

[bbnks2]

Originally Posted by 230iZTR

I agree completely. The 86 Twins are almost perfect for STX and it takes a very particular kind of course layout with long straights to give the 128i an advantage. I guess I’m just confused about why all the things that make the 128i a course-dependent monster don’t also make the 228i/230i a course-dependent monster as well? Is it really just that no one has bothered to try a proper STX build yet because a stripper of a 2 costs $35k new while a used 128i is half the cost and already has some proven builds?

My personal opinion is same as what you're speculating.

No one has even done a "proper" 128i STX build either lol. The two people that campaigned cars successfully still used stock seats, electronic differentials, and poorly setup suspensions (imo). They ditched their cars because they were "too expensive" to run when both only did minor mods (headers and exhaust tuning). One sold his 128i to another autocrosser who made a ton more changes to the car and took 4th this year in STX. That's the gist of what I remember from the 1addicts threads anyway...

Course dependent? The 128i/228i does have a superior power to weigh ratio so it will win in longer stretches. If you compare track width and wheelbase to other popular cars then on paper there is no reason to belive the car should be "course-dependent" and reliant on its horsepower to edge the competition. BMW has produced great handling cars for decades. There is just a longstanding myth that you can't get a 128i to stop under-steering. Literally every person I have ever had ask me about my 135i talks about how they "heard" that these cars are great but they understeer. It's just not true if you set the suspension up right lol.

Cost is again what I would go back to as the main factor in regard to setting up a 228i. That and the available DME tuning knowledge to do things like linear throttle and 2-step. Launching makes a big difference at nationals since they do 60' drag starts.

I would think the 228i would edge out the 128i. Superior torque and power curve. The 1.x" difference in wheelbase is negligible and the track width difference is non-existent when you factor in that STX cars will be running aftermarket wheels... The cars suspensions are virtually the same. 228i just has electronic steering with poor road feel but I would be willing to bet the variable sport ratios would lead to less hand movement than the abysmally slow 128 steering ratio (16:1).

[230iZTR]

Well...I’m planning on eventually doing most/all the “standard” STX stuff to my car because that’s where I think the sweet spot is for a streetable fast car. I’m definitely not a Nationals caliber driver though and haven’t autoXed since ‘07 on a poor high school student’s budget in an HS Ford Focus. My 230 is a stripper with only the Track Pack and ZF8A trans, so I subconsciously made it an ideal candidate for this sort of thing.

So I guess the first and most critical question is can a 17x9J rim and sticky 265mm tire fit under our tiny fenders?

I’ve seen one 255mm 17x8.5Jet40 setup with a 5mm spacer up front. I’m not certain the rear would fit without poking so badly it limits suspension travel.

I’ve also seen a 265mm square setup, but it was on an off-the-shelf Apex 18x9.5J setup with really goofy offsets and large spacers, maybe et30/F (after 12mm spacers) and et50/R (after 8mm spacers)? That would surely need a custom BC Forged or similar setup to replicate in a 9J without large spacers. It also had both camber plates and modified control arms and tension struts, which definitely would be illegal in STX if my understanding of the rules is correct. And that’s before you deal with the PITA of relocating the lower spring perch and swapping out a shorter main spring to gain inner clearance.

[bbnks2]

Originally Posted by 230iZTR

Well...I’m planning on eventually doing most/all the “standard” STX stuff to my car because that’s where I think the sweet spot is for a streetable fast car. I’m definitely not a Nationals caliber driver though and haven’t autoXed since ‘07 on a poor high school student’s budget in an HS Ford Focus. My 230 is a stripper with only the Track Pack and ZF8A trans, so I subconsciously made it an ideal candidate for this sort of thing.

So I guess the first and most critical question is can a 17x9J rim and sticky 265mm tire fit under our tiny fenders?

I’ve seen one 255mm 17x8.5Jet40 setup with a 5mm spacer up front. I’m not certain the rear would fit without poking so badly it limits suspension travel.

I’ve also seen a 265mm square setup, but it was on an off-the-shelf Apex 18x9.5J setup with really goofy offsets and large spacers, maybe et30/F (after 12mm spacers) and et50/R (after 8mm spacers)? That would surely need a custom BC Forged or similar setup to replicate in a 9J without large spacers. It also had both camber plates and modified control arms and tension struts, which definitely would be illegal in STX if my understanding of the rules is correct. And that’s before you deal with the PITA of relocating the lower spring perch and swapping out a shorter main spring to gain inner clearance.

You can fit 17x9 255/265 but it's going to be with goofy offsets which makes the rear end playful. You need to run a low offset up front to clear the strut and then a high offset in the rear to clear the fender. The front track width ends up being 2" wider than the rear. You don't really want custom offset wheels because then you can't rotate... It's better to buy a high offset wheel like 17x9 ET58 and then use a 20-25mm spacer up front to make them ET38-ET33... You'll need to roll/pull the fenders to get a "true" square setup. Pretty sure that it's legal to roll/pull fenders in STX. If you flare them then you're into street prepared. Replace them and you're into street modified.

Again, not too many people are pulling fenders on their luxury street cars lol

Not sure what caliber of drivers there are in your local region but when I run with nationals level drivers they are top 10 no matter what car they drive lol Just go to events and enjoy the car. It's definitely not slow.

[230iZTR]

Originally Posted by bbnks2

You can fit 17x9 255/265 but it's going to be with goofy offsets which makes the rear end playful.

Would a 17x9et42 and 255mm tire clear without rubbing the strut in front (with a small ~5-12mm spacer and 2.5*+ camber) and clear the fender without poking too much to limit travel in the rear? I’ve read that Apex makes a wheel “for the 1 & 2” in 18x9Jet42 but I can’t seem to find anyone actually running them. Someone in the wheels and tires sub told me the other day that a 17x9Jet45 would work with a front space but his car appeared to be a 1er rather than a 2er.

Originally Posted by bbnks2

You'll need to roll/pull the fenders to get a "true" square setup. Pretty sure that it's legal to roll/pull fenders in STX. If you flare them then you're into street prepared.

The ST* rules say only rolling the fender lips is legal. Any cutting or pulling would bump you out of the class. So I guess a truly square setup is out.

[AKPAB]

I am running a square setup 18x8.5et42 with 255/35/18 RE71. I am using a 12 mm spacer, and have 2.5* camber up front. No rubbing at all, so a 17x9 should fit (with spacer). When I ran Hoosier A7s at 245/35/18, the inside clearance to the strut was only about 3 mm. 255 RE71 is not near as wide. Spacer is key for interior clearance. Also using spacer when running stock staggered setup, as top of front wheels is way tucked in.

[bbnks2]

Originally Posted by 230iZTR

Would a 17x9et42 and 255mm tire clear without rubbing the strut in front (with a small ~5-12mm spacer and 2.5*+ camber) and clear the fender without poking too much to limit travel in the rear? I’ve read that Apex makes a wheel “for the 1 & 2” in 18x9Jet42 but I can’t seem to find anyone actually running them. Someone in the wheels and tires sub told me the other day that a 17x9Jet45 would work with a front space but his car appeared to be a 1er rather than a 2er.

The ST* rules say only rolling the fender lips is legal. Any cutting or pulling would bump you out of the class. So I guess a truly square setup is out.

You really need 235i specific measurements. You SHOULD be able to get that 17x9 to fit up front with a 5mm spacer and a fender roll. In the rear, I have no idea but I imagine the 235i has MORE clearance if anything. So, you should be able to make it work with a good fender roll and the right camber. That would be a decent setup. But what about tire fitments? 18's kind of suck in regard to tire fitment on 9" wheels. 255/35r18 is an odd tire size. 255/40r17 is a very popular size with lots of tire options.

[Shadowfax028]

I'm running Apex 18 x 9.5 et 38 with 5mm spacer with re71r's 255/35/18 on the front. I do get rub but only when the front is really compressed.

For the rear I run Apex 18 x 9.5 et 58 NO SPACERS with 255/35/18's no rubbing at all. This year I will change the rear up a bit . Gonna mount 265/35/18 re71r's with a 8mm spacer.

[230iZTR]

Originally Posted by Shadowfax028

I'm running Apex 18 x 9.5 et 38 with 5mm spacer with re71r's 255/35/18 on the front. I do get rub but only when the front is really compressed.

I’m on Vorshlag plates (2.4-deg/F & 2.0-deg/R) with Swift Spec-R F30 springs (I stupidly didn’t measure the before/after ride height, but I’m assuming it’s around a 1” drop, similar to H&R’s), and m-perf bumpstops.

Shadow, you’re on a similar setup right?

I’ll roll the front fenders, add longer stud conversion, and am open to spacers. I’m not sold on 17” v 18” but the options for 17” wheels are limited with wide tire selection, while 18” wheels are more numerous for offsets but seem to favor taller tires that make me concerned about rubbing.

Apex has awesome wheels, but the announcement that they’re adding a forged line this summer makes me want to wait and really nail the wheel/tire setup.

17/18x9et42 seems to be the sweet spot for biggest with minimal rubbing on a square setup, with enough spacer to get it down to an effective et36-33. 255/35/18 or 255/40/17 is the go to for track work? Or does being lowered require going with a slightly shorter stock height like a 245/35/18?

And if Apex doesn’t end up producing a 17/18x9et42 with a forged wheel, I also saw that Weds is planning to produce the TC105X in an 18x9et45 w/ 5x120 that should be darn near as strong and light as a forged wheel with their new process.Link.

I’m talking sense here right? Any thoughts?

[EstorilM240]

Lots of good experience and advice in this thread.

First time autocrossing the M240i, moderate to severe understeer the entire time, especially on higher speed sweepers. A vanilla M2 was doing quite well for its class and likely eliminated most of the soft handling issues (should have caught a ride). No LSD, Michelin Pilot Sport 4S, using basically stock tire pressures of about 36/40psi cold. Need to run in Sport Plus / possibly DSC off. About 70 degrees outside.

Based on what cxp213 is saying, probably even it out to something like 32/32 or 34/34, but TajoMan implies I should try something more like 40/40. If I'm more serious, I'd start looking into the possible camber adjustments and RE71's after I wear out these tires, but for now and the next 10+ sessions the driver mod will help the most. My past experience has mainly been on very different cars like the S2000 or FWD Hondas.

It is possible to add 1/2 deg. of camber with factory BMW steering knuckle/spindle. You need to use the part number intended for crash repair. It's a factory part intended for the M235i so it may be legal for the stock class, be sure to check the rules.

This also possible on the M240i?

[TajoMan]

With MPSS, front needed to be around 40~45 psig hot. Rear was ok around 35 psig.
PS4S may have stiffer sidewall. you should use chalk to see the wear on the side.

With RE71r, I'm using 35~37 psig front, 32 psig rear when hot.

[MAILIYAT]

Originally Posted by rwalker

Stock, the car pushes and eats front tires. Otherwise it's a blast.

Folks running the stock staggered setup run the front tire pressure a fair bit higher than the rears to counter understeer. I recommend coding for tire pressure and temperature i filezilla uc browser rufus n iDrive so you can watch them live.

The rest of this post covers recommended mods

An LSD helps a bunch to get power down out of corners and will help preserve your rear brake pads. I have a Quaife from HP Autowerks and it's great.

F8x LCAs and/or camber plates are pretty much a must or you will munch the outer shoulders of the fronts in very short order.

Finally, consider a square setup. I run a 255/35r18 square setup and it has served me well.

Let us know how you fare and where you end up with setup.

Anyway, since the car has been out long enough for some of you to run it for a couple of seasons, do you have any advice for someone who will be running a stock car? Any handling traits I should be aware of? Tire pressures that work best? Minor mods that you would recommend?

[rhop101]

For your first event. Make sure the tires are well inflated and use DSC Inactive Mode as the back end is much more controllable and doesn’t cause Sport+ boost cutting.

I’ve run my 2015 M235i AT w/225/245 std staggered at the local BMW CCA events with the stock PSS and I was running 46/44 for pressures on my surface based on the rollover. Could just be surface dependent. Idk how folks get away with low rear pressures as the rear tires end up on the sidewall and donuts ensue. I’ve been pretty close on my 3yr PSS to a 340i running PS4S by half a second or so.

Thinking about getting a set of the new Yokos for the car and just occasionally running it. I do have a street class prepped s2k as well. I’d go for the 37/32 or something on the yokos based on what I’ve seen for the re71s in prior pages of this thread.

Not sure there are really any minor mods you can do besides driver ones. The next place to go is camber plates and going 17x8 square

[230iZTR]

I learned a lot in my first year of AutoX and made huge improvements over 14 days of racing. My region is usually dominated by a guy who has consistently shown well at Nationals in a prepped 350z that won STU twice with a previous owner. I started off utterly uncompetitive (20% off pace) and finished about 10% behind his pax/rdp adjusted pace.

Next season I'll jump from the novice class (not running for seasonal points) to STX. I'll also be on Apex Arc-8R 17x9et42's with a 5mm spacer up front and RE71-R's in 255/40-17 with a light fender roll...but I could be convinced on Yokohama Advan AO52's instead. I might also Bootmod3 flash the ECU and do a muffler delete for less weight. I'm hoping that all those changes will work with the suspension mods I did earlier this year, as well as continuing to improve with AutoX seat time and iRacing practice, to get me another 5-10% in pace to be competitive.

[lufsig]

I don't think we can run any 2 series in STX? From SCCA rule book both 228 and M235 belongs to STU. Assume it's same for 230 and M240.

[230iZTR]

Originally Posted by lufsig

I don't think we can run any 2 series in STX? From SCCA rule book both 228 and M235 belongs to STU. Assume it's same for 230 and M240.

I was under the impression STX was 3.1L to 5.1L for NA and up to 2.0L for forced induction, with wheel/tire size restrictions of 9"/265mm for 2WD and 8"/245mm for AWD. Therefore the 2.0T RWD clearly fits. Not correct? Regional variation maybe?

Edit: After some additional reading I think that's based on the 2017 Catch-all definition for STX ([3.1-5.1L] NA or <2.0L Turbo, 4-seats, non-sportscar). The '17+ 230i wasn't specifically classed at the time I inquired after ordering the car so it makes sense based on the 2017 rules set. The '14-16 228i is classed by name and therefore goes to STU. The '17+ 230i is not otherwise classed by name and therefore falls into the STX catch-all. If they intended the 228/230/235/240 to be inherently similar, they would have used a naming convention similar to the 3-series entries in STX like "3-series (E46 chassis, non-M)".

Edit 2: I guess the confusion I'm having is that I don't understand why the 228/230 is in STU (Catch-all: >5.1L NA or [2.5-3.1L] Turbo, 4-seats, non-sportscar). Shouldn't it be in STH (Catch-all: <2.5L Turbo, 4-seats, non-sportscar)? None of this makes any sense to me.