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      09-22-2021, 10:46 AM   #45
msendit
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Originally Posted by Jamesjedi View Post
Did you have an optimal ride height? As measured from centre of wheel hub to fender.
Don't have a measurement at the moment. Plus, it will be very different on my car that's running probably close to 2x the spring rates of a typical street coilover kit.

This chassis tends to be limited by clearance in the front wheel well. I'd set the front as low as it goes without causing problems at full compression (put the wheel on and stick a jack under it to test). Then set the rear a few mm higher. Once you've driven a few times on track, adjust the rear to taste to dial the balance.

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Also, 1mm in size sway bar - noticeable?
It was bundled with a few other big changes -- shocks, springs, weight. The combo was definitely noticeable.
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      09-22-2021, 02:00 PM   #46
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Terrific information. Thanks for the reply.

I'm running b14 Bilsteins with 18x9 255 square.

Interesting that you say low as possible, as that will change suspension geometry.

I think my front sway is 25mm, rear I'm not sure.
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      09-22-2021, 04:41 PM   #47
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Interesting that you say low as possible, as that will change suspension geometry.
Yeah, I've never particularly felt the need for roll-center correction on this car, after lowering. No idea the actual reason -- maybe long control arms, or just there's not that much opportunity to lower it before running out of fender clearance. For comparison, my other strut-based car gets pretty diabolical without bumpsteer correction. Shrug, if it ain't broke...
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      09-22-2021, 07:06 PM   #48
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That is interesting. Yes, the change in geometry should make it twitchy on rough surfaces.

Control arm angle is important. You are saying it did not become jerky on the bumps.

A stiffer rear sway should give it less under steer. Wow are the bars a big deal to replace.
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      11-03-2021, 09:00 AM   #49
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... I'd definitely do many things differently (and probably not start with the F22 platform). But all in good time.
What would you have started with instead?

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      11-03-2021, 09:31 AM   #50
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Originally Posted by 35etrgsd View Post
What would you have started with instead?

msendit
For just a fun track day car in a similar price range -- probably a Supra. Pretty much every parameter that matters is better than the F22 from the factory -- tire space, weight, power, brakes, track width, etc. Not to mention aftermarket support.

For racing, very different story, depending on rulebook / which class. I actually did decide to bite the bullet and race the M240 in NASA ST4 next season, so pretty excited about that. But the easy choice in that class seems to be either a E36 or E46.
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      11-03-2021, 06:35 PM   #51
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Quote:
Originally Posted by 35etrgsd View Post
What would you have started with instead?
As F22 owners, I think that in the context of going faster on the track the answer is always going to be: a (much) lighter car with a more capable braking system.

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Originally Posted by msendit View Post
For just a fun track day car in a similar price range -- probably a Supra. Pretty much every parameter that matters is better than the F22 from the factory -- tire space, weight, power, brakes, track width, etc. Not to mention aftermarket support.

For racing, very different story, depending on rulebook / which class. I actually did decide to bite the bullet and race the M240 in NASA ST4 next season, so pretty excited about that. But the easy choice in that class seems to be either a E36 or E46.
Yeah.

As nice as our cars are when classed as street/track cars, when they're pure track/race cars my take is that it's an entirely different ball game. Turning heavy cars at racing speeds is a severe limitation, and our cars are heavy.

I look forward with great anticipation to your experiences and, hopefully, great results in ST4 next year; if you do share those with us, please include videos!

I would also find it interesting to see the absolute # and HP values of your car and those of any of your competitors.

I just took a quick glance at NASA's ST4 calculator and am wondering: is your car close to the #/HP limit for the class?
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      11-03-2021, 08:24 PM   #52
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Thanks dradernh and msendit for the feedback.

Thanks both and great builds.

Please reply either of you provide me with a reply in this thread for a different yet follow-up to my inquiry here?

https://www.2addicts.com/forums/show....php?t=1871541
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      11-03-2021, 10:31 PM   #53
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Quote:
Originally Posted by dradernh View Post
I look forward with great anticipation to your experiences and, hopefully, great results in ST4 next year; if you do share those with us, please include videos!

I would also find it interesting to see the absolute # and HP values of your car and those of any of your competitors.

I just took a quick glance at NASA's ST4 calculator and am wondering: is your car close to the #/HP limit for the class?
Hah, absolutely, will share videos. Though I'm not sure how open I can keep being about car development -- it won't be my ideas to share, but the race shop's.

As for P/W numbers, the NASA database is public here -- you can browse the competition all day. At least in NorCal, 2700-2800 lbs is a pretty typical min weight. The rulebook also has a nice bump in allowed tire width at 3000 lbs and some cars in other regions have done well just a bit above that weight.

Before the offseason, my car sits at 3400 min weight and 315 avg whp. With some (not competitive) tires, that's enough to barely skate in ST4. I've been testing lots of more aggressive tires lately (and really not doing serious competition with it), so I just ran it one class above in TT3. In broad strokes, the offseason plan is simple: lose some weight without going too crazy, detune to keep it in class with Hoosiers / Hankook DOT tires, max out the allowed aero, and see where that gets us. Will be interesting for sure.
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      12-14-2021, 11:25 PM   #54
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Quote:
Originally Posted by msendit View Post
Before the offseason, my car sits at 3400 min weight and 315 avg whp. With some (not competitive) tires, that's enough to barely skate in ST4. I've been testing lots of more aggressive tires lately (and really not doing serious competition with it), so I just ran it one class above in TT3. In broad strokes, the offseason plan is simple: lose some weight without going too crazy, detune to keep it in class with Hoosiers / Hankook DOT tires, max out the allowed aero, and see where that gets us. Will be interesting for sure.
It'll be nice to have more ST4 cars out there! What are you using to detune? BM3?

Looking forward to seeing how light you can get that chassis. You'll definitely have the most modern suspension design compared to the rest of the field!
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      12-15-2021, 10:01 AM   #55
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Quote:
Originally Posted by ScottSmith View Post
It'll be nice to have more ST4 cars out there! What are you using to detune? BM3?

Looking forward to seeing how light you can get that chassis. You'll definitely have the most modern suspension design compared to the rest of the field!
Absolutely! Excited to jump in on all the fun. Is your car back to life after the Sonoma shunt already?

About tuning platform, not sure. Randy at Epic is doing that. They have their own interface for the older cars, but not sure what his plans are for something newer.

And speaking of "modern XXX design", I'm not very happy about the 2022 rule changes. The new transmission and throttle body rules will cost me an extra 0.5... See, I'm already piling up the excuses 3 months before the seasons start!
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      12-15-2021, 10:57 AM   #56
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Quote:
Originally Posted by msendit View Post
Absolutely! Excited to jump in on all the fun. Is your car back to life after the Sonoma shunt already?

About tuning platform, not sure. Randy at Epic is doing that. They have their own interface for the older cars, but not sure what his plans are for something newer.

And speaking of "modern XXX design", I'm not very happy about the 2022 rule changes. The new transmission and throttle body rules will cost me an extra 0.5... See, I'm already piling up the excuses 3 months before the seasons start!
Working on it... motor looked like this inside: https://f30.bimmerpost.com/forums/sh....php?t=1882868

The throttle body change is an interesting one; you'd think that effect would be captured by sampling multiple datapoints on the power curve. On the plus side, most of the cars in our region already have electronic throttle so you won't be an outlier there.

The automatic hit is a bit high. Yes an automatic or DCT is an advantage over a manual on a turbo car, since it does a better job of keeping the turbo spooled on shifts. But shift times with an S54 and a manual ZF 5 speed are very fast; it's not much of an advantage there to have an auto. So really, having an auto/DCT on a turbo car is just making a turbo engine have similar performance to an N/A motor.
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      03-01-2022, 11:32 AM   #57
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Originally Posted by msendit View Post
And speaking of "modern XXX design", I'm not very happy about the 2022 rule changes. The new transmission and throttle body rules will cost me an extra 0.5... See, I'm already piling up the excuses 3 months before the seasons start!
I saw your new car missed the race last weekend. Is it close to being race ready?

I'm hoping to make the March Sonoma race.
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      03-01-2022, 12:44 PM   #58
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I saw your new car missed the race last weekend. Is it close to being race ready?

I'm hoping to make the March Sonoma race.
Yeah, I had to last-minute revive my ST5 car for this weekend. It wasn't great, by far -- ended up debugging engine control stuff all weekend to figure out why it suddenly pulled worse than the spec miatas, and in the end, might have damaged the engine. Oh well...

My current plan is to make the March race with the M240 as well. Certainly looks like the class pace has picked up, should be fun to try and chase.
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      03-15-2022, 03:53 PM   #59
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I love this!
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      03-23-2022, 11:24 AM   #60
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Quote:
Originally Posted by msendit View Post
Stage 5: M240iR

End track-hours: ~120
End Laguna Seca time: 1:44.0

End parts/specs:
M235iR fender flares from Flossman
Calipers: Brembo Club Race F, Brembo GT R
Rotors: 355x35 mm F, 345x28 mm R
Pads: RaceTechnologies RE10
Wheels: Apex FL-5 / SM-10 18x10" ET25
12 -> 15 -> 20 mm spacer front
Tires: RE71-r 285/30/18 square
occasional "drift setup": Hankook RS4 285/35 R only
Springs: 90 N/m 200 mm F, 150 N/m 200mm R
-3 camber, 1/16 toe out F, -2.2 camber 2/16 toe in R
many alignment variations between (-3;-3.5) F, (-2; -2.5) R

All the braking issues I described earlier made me realize the difference between a car that can do a few "hero" laps on track, and a sorted racecar with consistent performance every day. There's a massive step in between and the F22 weight isn't exactly helping it. Add in all the issues from damaging the bodywork and it seemed like the right time to try and step in the latter category. This would mean at the very least bumping up tires and brakes to match the car's weight.

Like many folks here, I'd salivated over the few bodykits for our chassis. I was leaning toward Manhart, but then I saw a set of cup car flares from a shop in Germany for what looked like a good price, so I jumped in. In hindsight, it was definitely not worth the trouble -- after taxes, duties, freight shipping, and a customs broker fee the cost was pretty much the same as getting them from Bimmerworld. Oh well, now I know...

I knew that the cup cars run 265/660 slicks at VLN. In the DOT sizes we're used to, that's about 285/35. There aren't that many sticky tires in 285/35/18, so I was choosing between 275/35 (very popular, many compounds) and the rare 285/30 (pretty much just RE71-r and Hoosiers). Decided to go for the 285/30 so I can still use the RE71-rs I was used to (I'd later find out that 275/35 actually needs a fair bit more work to fit in the well). A 10" wheel seems about right for that, with as low offset as possible -- there should be plenty of room to push them out with the flares and I was expecting the biggest problem would be clearing the suspension at the front.

I was already overwhelming the brakes with 245 tires -- adding this much more grip without better brakes wouldn't be smart. At that point I was thinking a Stoptech BBK with some ducting, similar to what I've been mocking out at home. Also, a big bump in grip under braking would probably need stiffer springs too -- my previous setup was already diving a lot in braking zones. Problem is, I had no idea what the effective rate of the progressive spring in my KW V3 was. I cursed the shop that sold me the V3 again for good measure (not that I'm holding a grudge or anything), and figured 90 N/m might be a good starting point (based on the Clubsport rates).

With that, I felt like I'd done enough of my homework to start talking to the race shop that was actually doing the work. The plan changed a bit after talking to them -- they'd spec out a brake kit with Brembo (Club Race calipers front and GT calipers rear) and ditch the brake ducts (unless we really need them). I still don't trailer the car and drive it to the track and back -- brake ducts would probably get destroyed in that process. Plus, they had had very good experience competing with the Brembo brakes (including in the 25 hours of Thunderhill), so it was a known solid piece of kit to go with. There isn't that much choice in race pads for this caliper shape -- I'd rather not use a sprint compound on a car that still sees the street, which left us with the enduro RE10. On some other (admittedly much lighter) cars, they'd lasted more than half-distance in the 25-hours, which sounded pretty promising.



Fitting the fender flares went without much trouble. Of course, we needed to trim the original fender lips -- that's the whole purpose of doing this. The front flares have a convenient lip on the inside with mounting holes, so we could just bolt them in. The big rear panels actually had bolts laid into the fiber and sticking out, but we ended up not using them -- that would've required taking out all the interior panels (that was probably a mistake -- I should've just gutted the interior and stopped pretending this is a street car any more). Instead we riveted them. Also riveted the front bumper extensions. The point was never to optimize for looks, so rivets didn't bother me -- plus a livery would mostly cover them anyway. For the most part the new panels fit ok -- the front bumper extensions needed a tiny trim to clear my air dam, and the driver-side rear panel had a bit of a kink near the tail light, but really nothing major. Here's a few closeups on fitment (for Dylan86 ).

No problems with fitting the wheels and tires at the rear, there's plenty of space there -- if I had to guess probably enough even to fit a 305 tire on a 11" wheel. The front, on the other hand... much more painful. To clear the suspension, we started with a 12mm spacer. It was still a pretty tight fit -- maybe 2-3 mm clearance from the spring perch. The low-profile 285/30 tires barely brushed the fender liners (which we kept, because why not) once you add a lot of steering lock -- both at the front and at the back of the wheel well. Not enough to cause trouble yet, but it meant that pushing the wheel out even more would start rubbing harder (and at less steering lock). It would also mean running /35 tires would be much harder without more drastic changes.



All that said and done, it was time to start testing. First, the good. The increase in front-end grip is pretty drastic. The car actually wants to rotate on entry now instead of only pushing, so I had to unlearn some of my deep trailbraking habits. Also, braking distances are way shorter now. In fact, the first thing anyone notices riding along on track is "Holy cow, these brakes!". Even after ~30 hours with this config, I'm still not completely used to it and tend to overbrake into corners. They seem to cool adequately without brake ducts too -- for now at least, I'd be curious to see if that's still the case during the summer. The spring rates we ended up with actually turned out OK too -- I was worried they might bring back some snappy behaviors, but slides are still very predictable.

The bad -- these 285/30 tires. First test day out with this setup, the inside sidewall of the loaded tire caught the suspension and tore. I didn't think too much of it -- there was barely 2-3 mm clearance, the tires expand a bit when you push them, plus the sidewall can flex a little. So, I just swapped the 12mm spacers with 15mm and decided to live with a little more fender liner rubbing for the time being.

A couple of days later, similar story. Inside sidewall of the loaded tire caught the suspension again and tore. More worried now, but went to a 20mm spacer with heaps of suspension clearance (and a pretty bad rub in the frame once you add steering lock). More testing (and more failed tires) revealed the root cause of the issue -- the sidewall was failing and buldging out and only then catching the suspension (example). Kinda like runflats against potholes -- but I wouldn't expect that from stiff sidewall tires like the RE71-r. Over the next few test days, I tried out many theories about what could be causing this -- too much camber, too much toe out, pushing too hard on cold tires, etc. None of them seemed to pan out. After 7 tires failing this way (as if the running costs of this car weren't already absurd) and trying to make the /30 tire work, I decided I've had enough and the simplest explanation was probably enough -- just too little sidewall to support the car's (massive) weight when leaning in a corner. Which would mean making even more changes to try and fit a /35-profile tire.

Hey Dude.

Hopefully you want to help a brother out a bit. I own a BMW F21 M135i, which is built for trackdays just like yours.
I just received my M240iR carbon widebody a few days ago, and i want to ask if you want to take some pictures for me, mostly of your rear wheel arches.
The reason for this, is i cant somehow figure out what to do with the existing wheels arch, i know it needs to be cut, but i cant figure out how much should be taken away, also, did you managed to fit bolts into the rear panels, in the arch lining? I see there is like 4 5mm nuts molded into the panels.

I appreciate what ever help you can provide to me.
Thanks mate.

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      03-23-2022, 08:36 PM   #61
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Hopefully you want to help a brother out a bit. I own a BMW F21 M135i, which is built for trackdays just like yours.
I just received my M240iR carbon widebody a few days ago, and i want to ask if you want to take some pictures for me, mostly of your rear wheel arches.
The reason for this, is i cant somehow figure out what to do with the existing wheels arch, i know it needs to be cut, but i cant figure out how much should be taken away, also, did you managed to fit bolts into the rear panels, in the arch lining? I see there is like 4 5mm nuts molded into the panels.
No problem, I can take a closer peek at the arches this weekend when my car's out of storage.

Interesting your panels have nuts molded in -- mine were the same, but with bolts. We ended up just cutting the bolts out and riveting the panels to the OEM bodywork. At the time I still had rear interior and taking that apart just to bolt on the fenders seemed like a hassle.

Last edited by msendit; 03-23-2022 at 11:37 PM..
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      03-24-2022, 12:48 AM   #62
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Thank you!
I've attached Photos of my current state of my project with the arches.
Mines bought directly from BMW dealer.

Well, as you said, yours came with bolts, mine also did that, in the top of the panels. Down in the wheel arch they molded in nuts, and somehow a bolt should come through a panel there or something. Maybe i can tell what to do, when i see some pictures of yours
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      04-06-2022, 05:05 AM   #63
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Hey, so did you manage to get some pictures for me? :-)
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      04-24-2022, 08:09 AM   #64
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Hey, so did you manage to get some pictures for me? :-)
Better late than never?

Yeah, there's two cap head screws holding the overfender to the sheet metal on the bottom side: photos.
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      04-24-2022, 10:55 PM   #65
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True, and thank you.
I see you dont have the carbon inner fenders/Wheel barrels glued into the bodywork itself.
I am actually going to the Nürburgring on Friday to meet some local racing companies who is used to work with the M235iR cars, curious to see how much things will set me back. But I do expect it wont be cheap nonetheless.
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      12-08-2022, 12:51 AM   #66
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Haven't updated this thread in a while.

But the fine folks at NASA Speed News just wrote an article about my car that covers its 2022 woes pretty well.

I'm a bit biased, but I think it's a good read:
https://nasaspeed.news/cool-rides/bl...a-bmw-chassis/
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