[rhop101]

Hi 2Addicts,

A momentous occasion has occurred. I've paid off my car!

A 2015 M235i 8-spd ZF RWD Model

Now to start planning modifications

Just kidding. First it's time for attending more Autocross events and getting a real feel for the car.

I've been autocrossing the car on and off since I got it along with my CS-lite prepped S2000, but recently I moved to NYC and that is just not an environment I want to bring an S2000 into plus I would have to pay to park the 2nd car. So I'm likely going to sell the S2000 and "for fun" build an STU-lite M235i. I know its not going to win NATs when E9X Ms can mount 10.5" wheels and 285 tires, but I've seen very few M235i get prepped for STU. I've seen a few 135i get prepped as well and with both cars now being ~$20k cars I figure others maybe looking to mod up their M235i for Autocross so why not start a build thread about it.

I already have a bit of a start. Current Mods are:

• Vorshlag Camber Plates
• Alignment: 0 toe up front dialed to 2.4deg Camber for the Street/AX compromise. Just a little toe in at the back with 2.1deg Camber
• BootMod Stage1 93 tune
• CSF Intercooler
• Evolution Racewerks Charge Pipe
• 225/40/18 RE71RS 200tw tires on Stock Rims

For Next Year's Season going to looking at some upgrades. A lot of research still to do here. For this year I'm really trying to focus on the driving and figuring out what the car needs the most. The above is the order I'll likely make additional improvements to the car in. Ideally I'd do the upgrades all at once, but if not still something to be said for making tweaks gradually and seeing how that changes what the car needs tweaked to keep it balanced.

In approximate order:

• LSD - Probably M-Performance, but I may give Bimmerworld or DiffsOnline a call regarding that though
• Coilovers - maybe Ohlin Road and Track, seen good reviews on the F3X forums about them
• Hotchkiss Front Swaybar
• 17x9 or 18x9 Wheels - Going to be a bit tricky, shooting to get 255 square on the car

Anyway on with the Autocrosses!

Despite not being an M2 the car is quite fun to autocross and I recommend anyone take their M235i and give it a try. The short wheelbase and good torque delivery really make the car pretty nimble for a luxury barge and real fast in more open sections. With stock wheels it is an exercise in patience in the turns, but coming from an S2000 getting on the gas and launching it down the more open straight areas of the course feels amazing. The 200tw tires definitely help with grip levels given the open diff. Here's an event I did recently with Philadelphia SCCA.

I went in the first group so I didn't get much chance to observe other drivers' lines. Between the 1st Turn-around and the 2nd I saw some drivers take a slightly wider entry up the hill just scrapping one of the walls on their way up the hill. That line would have extended the straight a few tenths more. Comparing my 5th run to my 6th I found giving up just 1mph more speed really allowed the car to turn-in slightly earlier and begin the exit onto the straightaway up the hill toward the 2nd turn-around earlier. Definitely feel the car struggling a bit with inside tire grip due to the lot being a bit of an inverse bowl, but using 3rd gear keeps this mostly under control.

[jb-slow]

You could switch to staggered wheels, you can get a lot more tire under there. Also should look into a oil pan baffle or m2 oil pump setup before its too late.

[rhop101]

Thanks for the reminder about the oil pump jb-slow should have this on my radar... I have looked at that in the past and didn't see any non-welded baffle options at the time, but it looks like Turner has come out with one!

https://www.turnermotorsport.com/p-4...ed-sump-plate/

Anyone installed this yet? only $444 cheap by comparison to the M2 Pump Upgrade.

I needed to do an oil pan gasket anyway this winter. So it would be a good opportunity to install this baffle and put the front sway bar in.

If anyone else wants to weigh in on Staggered vs Square I'm all ears. In theory staggered would maximize the grip potential of all 4 corners. Not like I'm used to rotating wheels anyways with either of my cars And since I'm tweaking things in the suspension I can always adjust things and add a larger rear bar if needed.

[dradernh]

Originally Posted by rhop101

If anyone else wants to weigh in on Staggered vs Square I'm all ears. In theory staggered would maximize the grip potential of all 4 corners. Not like I'm used to rotating wheels anyways with either of my cars And since I'm tweaking things in the suspension I can always adjust things and add a larger rear bar if needed.

I can't advise you on what's likely to work best for you, but this is what I did to get almost-square tread widths in the tire I wanted to run on the track.

I ran Apex 17X9 ET42 in front and 18X9½ ET58 in the rear. The latter had 5mm spacers. The tires were R888Rs, 255/40 in front and 255/35 in the rear.

The street/track alignment was Front: -2.6° L&R camber, -0.15 LF/-0.06 RF toe; Rear: -2.3° LR/-2.1 RR camber, -0.11 LR/-0.21 RR toe.

The car had Koni-based coilovers. My understanding is that the wheel and tire combination in front fit not only because of the negative camber and a slight fender roll, but also because the Konis (and some other coilovers, according to one of the vendors here (can't recall which)) take up less space and leave more room for the front tires than do some other coilovers. I had no rubbing under any circumstances.

[rhop101]

Yeaaaa I think Apex has a list and it figures when I just checked it the Olhin Road and Track is on the list 🫠. Well guess I need to add updating the camber plates to the mod list 😂. Means MCS, JRZ, Koni coilovers

Good to know about the staggered setup and that it worked. Guess once you go staggered whatever works 😅. Interesting you went with the 17” wheels up front and 18s in the back. I’ll be looking for 200tw so I assume that would be similar in tread width to the R888s. I’d probably try to squeeze 265 on, but I’ll have to ask Bimmerworld how they go about doing that. They mention it on their site.

[dradernh]

Originally Posted by rhop101

I assume...

A good friend I went to high school with who for many decades owned and operated a very successful four-bay shop in San Francisco had a big sign on the wall behind his desk. It said "Assume Nothing".

That message was for his mechanics, back when cars were still worked-on by mechanics.

[jb-slow]

Originally Posted by rhop101

Thanks for the reminder about the oil pump jb-slow should have this on my radar... I have looked at that in the past and didn't see any non-welded baffle options at the time, but it looks like Turner has come out with one!

https://www.turnermotorsport.com/p-4...ed-sump-plate/

Anyone installed this yet? only $444 cheap by comparison to the M2 Pump Upgrade.

I needed to do an oil pan gasket anyway this winter. So it would be a good opportunity to install this baffle and put the front sway bar in.

I put that baffle in mine, the car hasn't exploded yet so i guess it's working.

[Aspen235]

Originally Posted by dradernh

I can't advise you on what's likely to work best for you, but this is what I did to get almost-square tread widths in the tire I wanted to run on the track.

I ran Apex 17X9 ET42 in front and 18X9½ ET58 in the rear. The latter had 5mm spacers. The tires were R888Rs, 255/40 in front and 255/35 in the rear.

The street/track alignment was Front: -2.6° L&R camber, -0.15 LF/-0.06 RF toe; Rear: -2.3° LR/-2.1 RR camber, -0.11 LR/-0.21 RR toe.

Hi, what's with the asymmetrical toe front and rear? Was that intentional?

[dradernh]

Originally Posted by Aspen235

Hi, what's with the asymmetrical toe front and rear? Was that intentional?

I don't know.

I asked for a street/track alignment at 2K, drove the car for 10K or so on the street, and then had the alignment checked. The latter provided the data I listed; I'm not sure whether or not I have the original alignment data to compare it to.

The shop that checked the alignment is very sharp. I watched while the owner did the work, and he had no comment on the result. He certainly would have spoken up if he thought something was amiss.

I pretty much just drive the car.

[rhop101]

Originally Posted by dradernh

A good friend I went to high school with who for many decades owned and operated a very successful four-bay shop in San Francisco had a big sign on the wall behind his desk. It said "Assume Nothing".

That message was for his mechanics, back when cars were still worked-on by mechanics.

Well guess I’m making a table lol. I looked at 265 RE71RS and its treadwidth was like ~9.5” and 255 R888 is like 10.1” 😂. To include in the table Tread Width, Section Width, Tire Diameter

[rhop101]

I didn’t post much at the end of 2023 I only did 2-3 more events and I had triple camera failure for one of them.

Mostly I just kept driving the car as is and when the tires ran out I just stopped for the year at the end of September. Did fairly well at last year’s O’fest and convinced myself for sure the LSD was a must before anything else after driving an M340i on a wet skidpad (a G-series one). Really amazing how much more stable the rear felt compared to mine.

My Ofest autocross fastest run. Was a really interesting course with a cambered and flat area.

[rhop101]

Onto this year’s updates

Over the winter I purchased and installed the Oil Pan Baffle. With the subframe down to do the pan gasket and baffle I was so so tempted to just put the hotchkiss sway bar in there, but I resisted for now. I’m still on the stock tire sizes and front grip is definitely a handicap for the car and I still actually drive the car on bumpy roads and I’ll probably do coilovers sometime next year.

I also installed the M Performance LSD in my car because ML Performance had such a screaming deal I couldn’t resist. I had to wait 4 weeks for it but was only $2100 for the diff+install. I got it installed in mid-February and I spent a bit of time on backroads breaking it in. I agree with the sentiment that unless you are tracking the car or a launch control junkie on the street there isn’t a ton of point, the stability control is quite good.

On a track-cross course though oh my word is the car so much more what you’d expect from a BMW.

It’s actually throttle steerable on corner exit and the lock on decel doesn’t hurt much.

Front grip is now most clearly the issue. In search of more grip I tried lowering my pressures way down and letting the tires roll over to the bottom of the indicator triangles on the RT660s instead of the top. This brought my pressures down to 35/33 and improved the front grip noticeably while allowing better throttle steering at exit. Going to experiment a bit at the next autocross and to see what reads best on the combined-G plots.

Next mod for sure is a proper wheel and tire package. Probably ARC8 18x9 in the front and 18x9.5 in the back with 255 square tires depending on when these tires croak in the season. Probably not soon enough for the Pro-Solo in Cleveland at the end of next month, besides don’t think I’ll have the mula saved up and I want to enjoy more opportunities to actually drive the car.

[rhop101]

I came up with 2 goals for this next Autocross:
- Experiment with tire pressures
- Compare DSC off and Sport+ and figure out which yields better results now that I have an LSD to back up Sport+

First run of the day showed how gravelly the lot is. If you end up off line it gets so bad. I’m actually really impressed with my aggressive first run and in some areas of the course I ran some of the tightest lines I ran all event.

On my 4th run I changed my tire pressures from 35/33 to 34/32 thinking the lower pressure might improve traction, but I was already about 2/3 down the triangles on the sides of the tire and the lower pressure yielded my fastest run of the morning, with a decent slide mid-run. It actually looks like 34 might be the best front pressure but 32 is too low possible for the rear. The rear suddenly let go and I’m not sure if that was gravel, but my line on entry doesn’t seem that different. I decided to stick with 35/33 for the afternoon because it was more stable.

Now that I know how sport+ is I might be more willing to try 34/33 or something similar in the future. Sport+ really made the car easier to drive with the stiffer shock setting and the lsd really synergizes with the drive mode now. I gradually picked up more speed and my first run in afternoon was matched my best morning run. By my last and fastest run was only 0.65 off a well driven 135 with 245 square tires.

Look forward to experimenting more with rear tire pressures at the next event and getting more used to sport+ mode. I also need to work on my left side cone proximity. I seem to be not driving as close to cones in my left side as I could. I do better with right side cones for whatever reason.

[rhop101]

Another weekend another AX this time in NJ. In my role as M Chapter Governor it’s good for me to go around and support various chapters events. TD Bank Ballpark is certainly an interesting lot. It’s very small maybe 800ft x 200ft wide for the course. It results in courses that has very tight elements that are reused multiple times on a run. Tight is of course is relative but compared to my normal lots it’s much tighter.

It was a great opportunity to play with rear tire pressures though and with 5 morning runs and more in the afternoon, I went at it. After my first run I left the fronts at 35 psi and varied the rear pressures from 32 up to 37 or so. I settled on 35/36 for this low speed technical course and in the afternoon focused on the driving with sport+ engaged for the stiffer shock setting.

My best raw time ended up being a 41.541. The 2nd fastest raw time of the event but still quite a ways behind a cayman. Unfortunately it was dirty because I was a hair too aggressive on apexing the first cone of the course.

My fastest clean run was a 42.166. After I goofed the entry speed on the slalom heading into the finish.

I really didn’t lose much time compared to my fastest raw time in the first 20 seconds, I was more conservative with my braking after the 2nd crossing sweeper and then messed up the entry of the 2nd slalom.

Probably one more event before the 255s get mounted all around.

[rhop101]

Last event in the books with the stock wheels. I am probably going to put on the wheels this weekend.

The well driven modified 135 in our region didn’t show up so FTD was up in the air. So there was a chance for me to go for it. Walking the course there weren’t any massive straights to really take advantage of the power and get up into 3rd gear, but I took my tire pressures from the prior weekend 35/36 and Sport+ and just went with it. The course behind the wheel actually flowed really well and there was more grip than the prior event for whatever reason. With my final run I managed to clench FTD for the event BMW with a 37.581, just beating out a Boxster by .006 seconds 😬. It was close, but I put everything together….

Looking forward to figuring out the 255 square tires. Pretty wild what a 235 can do with 200tw, camber plates and an LSD.

[rhop101]

This weekend will be my first event on 255/35R18s mounted on Apex Arc-8s
Front: 18x9 ET42 w/12mm spacers and longer bolts Rear 18x9.5 ET58s

At the moment I’m still stock suspension with just camber plates and the Mperformance diff.

Certainly at a glance fitment is awesome. It’s basically almost flush front and back.

I found I had to increase front camber a bit more to help the tires tuck in. Rolling the front fenders might be where I end up. Currently:
Front: 3.4-3.5ish
Rear: 1.8

At full compression the fenders justtt imprint but don’t cut the sidewall.

I haven’t been able to hoon the car enough to say if rubbing is going to be a problem and thus require fender rolling.

If anyone wants to chime in on tire pressures they’ve run at Track/AX with 255s on the 235/240 feel free!

I’m going to start with 31 all around and just read the sidewalls and run 2-3 more runs to dial in the pressures based on run times then adjust the pressures front to rear based on any bias changes I want.

I also looked on the M2 forums to see what pressures they were running and 32-34psi seemed to be there. I was talking with some of the Supra guys they run 28/29 but can fit 285s

Before on 225/235 RT660s on stock rims the car seemed to like 35/36 F/R pressures. This was a compromise to maximize front grip then tune the rear pressures for a slight oversteer handling bias

[rhop101]

First time out on the 255s. 31 all wasn’t a bad starting point for honing in on tire pressures. Front grip has improved somewhat relative to rear grip in terms of grip balance, definitely some getting used to with the new wheels and tires.

In sport shock setting using sport+ the tires don’t rub due to the extra stiffness over comfort shock setting.

No FTD this week but a few more fast cars made it out this time including a couple on the the controversial not 200tw 200tw tires.

Here was my fastest run of the day. Funny enough my first tires cold run I the afternoon was my fastest raw time. Probably should have used 3rd for the slalom to the back of the course the front grip especially in transitions like slaloms has improved a lot.

Next time I’m going to try 32/33 on pressures. Then maybe increase the rear by 1 if I feel I need to dial in a smidge more oversteer. Toward the end of the event I found that front grip dropped off a bit at 31/32 even with cooling the tires down. The RE71RSes really are a bit more sensitive to heat. It was also 34C here.

[AmuroRay]

Originally Posted by rhop101

Onto this year’s updates

Over the winter I purchased and installed the Oil Pan Baffle. With the subframe down to do the pan gasket and baffle I was so so tempted to just put the hotchkiss sway bar in there, but I resisted for now. I’m still on the stock tire sizes and front grip is definitely a handicap for the car and I still actually drive the car on bumpy roads and I’ll probably do coilovers sometime next year.

I also installed the M Performance LSD in my car because ML Performance had such a screaming deal I couldn’t resist. I had to wait 4 weeks for it but was only $2100 for the diff+install. I got it installed in mid-February and I spent a bit of time on backroads breaking it in. I agree with the sentiment that unless you are tracking the car or a launch control junkie on the street there isn’t a ton of point, the stability control is quite good.

On a track-cross course though oh my word is the car so much more what you’d expect from a BMW.

It’s actually throttle steerable on corner exit and the lock on decel doesn’t hurt much.

Front grip is now most clearly the issue. In search of more grip I tried lowering my pressures way down and letting the tires roll over to the bottom of the indicator triangles on the RT660s instead of the top. This brought my pressures down to 35/33 and improved the front grip noticeably while allowing better throttle steering at exit. Going to experiment a bit at the next autocross and to see what reads best on the combined-G plots.

Next mod for sure is a proper wheel and tire package. Probably ARC8 18x9 in the front and 18x9.5 in the back with 255 square tires depending on when these tires croak in the season. Probably not soon enough for the Pro-Solo in Cleveland at the end of next month, besides don’t think I’ll have the mula saved up and I want to enjoy more opportunities to actually drive the car.

Log your oil pressure!

[rhop101]

Hi Amuro,

I certainly keep an eye on the oil level and run with the preventative measures except going to the S55 oil pump. I have the MMR baffle installed and make sure the level is at 74mm in bimmerlink before I run the car at events.

I'll see if I can figure out a way without resorting to invading the wiring haha. Unfortunately the apps that record data for track driving don't have the same access as Bimmerlink and others. But then my BLE+bimmerlink has like a 1hz refresh rate which isn't enough to display anything meaningful and lacks context. Guess I'm buying a different OBD reader with a higher refresh rate and see if i can do a work around for the G data to. I'll see if the car has an accelerometer value I could read.

Any recommendations on OBD readers? I see OBDLink MX has the kind of refresh rate I need....

[rhop101]

Finally had another event, Well i experimented and unfortunately even with a higher read rate device BimmerLink only processes the data at 1Hz. So for science I ran one of my runs with the BLE instead of the WiFi one to get an idea of what the oil pressures are like out on course with the MMR baffle. Don’t have a before to compare to sadly.

So nominally oil pressure was around 70psi during the lap. The low was 40psi and right afterward was my peak of 98. The oil pump was obviously compensating for the drop in pressure by requesting full pressure right after being around 40.

Will review the run footage tonight and sync the data up so I can see where on course that was. I suspect it was one of two elements later in the course which involved hard braking

[rhop101]

Here is my run with data from Bimmerlink. Based on the syncing of the footage, looks like the baffle is doing its job with the pressure not dropping below 40psi at any point though the lowest was definitely coming out of sweeping corners @34s and @44s. Shorter braking moments didn't cause pressure to drop at all. But the sweepers did cause the pressure to drop to around 40psi then followed by a spike to max pressure.

[AmuroRay]

Originally Posted by rhop101

Hi Amuro,

I certainly keep an eye on the oil level and run with the preventative measures except going to the S55 oil pump. I have the MMR baffle installed and make sure the level is at 74mm in bimmerlink before I run the car at events.

I'll see if I can figure out a way without resorting to invading the wiring haha. Unfortunately the apps that record data for track driving don't have the same access as Bimmerlink and others. But then my BLE+bimmerlink has like a 1hz refresh rate which isn't enough to display anything meaningful and lacks context. Guess I'm buying a different OBD reader with a higher refresh rate and see if i can do a work around for the G data to. I'll see if the car has an accelerometer value I could read.

Any recommendations on OBD readers? I see OBDLink MX has the kind of refresh rate I need....

I know you can do full parameter logging with BM3 and MHD, which includes oil pressure.