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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Tracking, Autocrossing, Dragstrip, Driving Techniques > Why sedan instead of coupe



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      11-23-2010, 06:58 AM   #1
BuckyE93
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Why sedan instead of coupe

Hello everyone, i was just wondering why are there more 3 series sedans used in professional racing than 3 series coupes? even turner motorsport uses sedans instead of coupes. i was just curious as two what advantages it may have. thank you and im sorry if this has been posted before.
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      11-23-2010, 10:25 AM   #2
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The sedan chassis is marginally stiffer due to the B-pillar I believe. I may be wrong.
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      11-23-2010, 10:46 AM   #3
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I also think the Sedan is a bit stiffer. The coupe is far sexier though.
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      11-23-2010, 10:51 AM   #4
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rules require a 4dr
http://admin.grand-am.com/assets/Det...201013docx.pdf
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      11-23-2010, 08:51 PM   #5
BuckyE93
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i guess its that, i dont think its the stiffness, because for the m3 the coupe is used instead of the sedan, thank you.
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      11-24-2010, 03:04 PM   #6
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I've read that the rear subframe in the e90 sedans is a better set up for handling as well. Seems like I remember the 335i sedan putting down a slightly quicker lap time to the 335i coupe in the C&D Lightening Lap a few years back.
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      11-30-2010, 07:53 AM   #7
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There's also a balance reason. The sedan's weight is so perfectly balanced for track use,
that when designing the car, the engineers even counted the number of bolts they used in the front vs back of the vehicle.

Until I found this out, I thought their whole "ultimate driving machine" thing was just a marketing gimmick. But as it turns out, they're no joke about their precision and performance, bordering on obsessive type-a personality disorders.
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      11-30-2010, 08:02 AM   #8
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Quote:
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There's also a balance reason. The sedan's weight is so perfectly balanced for track use,
that when designing the car, the engineers even counted the number of bolts they used in the front vs back of the vehicle.
Umm, the Coupe has better weight distribution than the Sedan. (51.2/48.8 vs 51.5/48.5). Secondly the whole "engineer's counting the number of bolts front vs back" is nonsense.
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      11-30-2010, 08:25 AM   #9
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Quote:
Originally Posted by jaguar36 View Post
Umm, the Coupe has better weight distribution than the Sedan. (51.2/48.8 vs 51.5/48.5). Secondly the whole "engineer's counting the number of bolts front vs back" is nonsense.
Despite what you say, BMW cares about weight distribution, and they do pay attention to how their parts are distributed. Counting bolts may be a euphemism, but they do in fact take weight distribution extremely seriously, up to a ridiculous point.

I refuse to believe that bmw doesn't care about their engineering. They don't get that 50/50 balance by ignoring such things.
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      11-30-2010, 09:27 AM   #10
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Right... they don't actually get a 50/50 balance. Still better than alot of manufactures though.

I'm not sure what you mean by a ridiculous point... although I would assume if they took it to a ridiculous point they would get it to 50/50.

Regardless a 50/50 weight balance is not the be all end all of handling... they could do alot more by just making the car lighter than by trying to rearrange all the weight (which is going to be screwed up anyway as soon as you put some people or gear in the car)
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      11-30-2010, 12:59 PM   #11
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Regardless a 50/50 weight balance is not the be all end all of handling...
Exactly. There are a plenty of Porsche drivers that would love to argue this.
Regardless, arguing the less than 1% distribution between the coupe and the sedan is ridiculous. The weight of the driver is going to make more difference than that. Not to mention other factors like tire size choice and alignment.
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      11-30-2010, 04:22 PM   #12
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Exactly. There are a plenty of Porsche drivers that would love to argue this.
Regardless, arguing the less than 1% distribution between the coupe and the sedan is ridiculous. The weight of the driver is going to make more difference than that. Not to mention other factors like tire size choice and alignment.
Plus almost ALL race cars, even in club racing level, are all corner balanced so the slight difference front to back is inconsequential. Having the CROSS weight equal is far more important than having the front and rear weigh the same.

And the pinnacle of street sports cars, the Ferrari F458, has a F42/R58 distribution.
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      12-01-2010, 08:58 PM   #13
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Cause it;s a less cheaper?
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      12-02-2010, 12:34 PM   #14
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Quote:
Originally Posted by gunsekun View Post
Cause it;s a less cheaper?
When the operating budget for a decent professional race-team usually runs in the $100,000 A YEAR range outside of the cost of the car, I don't think a few thousand dollars difference in the base car means jack.
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No way I'd ever take my BMW to the track.
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Then why do you have $3,000 worth of suspension mods on your car?
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      12-02-2010, 06:55 PM   #15
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Lol... it was a joke....
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      12-03-2010, 02:20 AM   #16
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Because sedans have fo dos fo mo hoes.
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      12-03-2010, 01:21 PM   #17
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Because sedans have fo dos fo mo hoes.
LMFAOOO
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      12-03-2010, 01:25 PM   #18
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well it turns out it is because of the rules. but when it comes to the m3, coupes are being used instead of sedans. another thing i found out is that unlike the e36 or e46. the e9X cars were designed separately, meaning they didnt get a e90 and subtract two doors like they did in the previous models. the coupes are designed from ground up, it is longer and if im not mistaken its narrower. but as far as stiffness its just as stiff if not stiffer. it just comes down to the rules of the class.
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      12-04-2010, 11:12 PM   #19
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There are a few reasons I suspect. Its been noted that the sedans are stiffer than the coupes. I don't think this is true with the e90/e92 generation but was true with the older 3 series (e36).

A few other posters noted the weight distribution. Well needless to say the weight distribution changes when you take a few hundred pounds out of the car for race purposes. So I'm not sure you can completely conclude that just because they start at about 50-50 from the factory that they would be that way when stripped down to only essential parts. The weight distribution side to side being equal makes sense though. I would guess that the sedan once stripped may have a better weight distribution (read as more weight in the rear).

And lastly, I believe the sedan has a slightly wider track.

So on top of the rules... that's my 2 cents.
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      12-05-2010, 11:52 PM   #20
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I'm pretty sure the sedans can fit more aggressive/wider wheels and tires, but that's probably something that would be modified to allow for anyways.
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      12-05-2010, 11:57 PM   #21
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Interesting thread...coming from e46 world where m3 didn't exist as sedans, I wonder if it was the same case.
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      01-12-2011, 08:14 PM   #22
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Think it also has to do with class of car
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