325 2 door vs 4 door

[moggy]

Hi

A friend and I are looking to buy a cheap track day car to get us started.

To narrow down the search we have mainly been looking at E36 328 coupes. However there is a E30 325 4 door for sale neare my home for reasonable money.

Can anyone explain the difference, in terms of track use, of a 2 door vs 4 door? I am guessing they have the same floor plan, but is the 2 door structurally superior for example? Many thanks

[oldroydsr4]

There will be next to no difference in the structual regidity of the shells and even if there was 99% of drivers would never tell the difference.

+ for a trackday car it wouldn't really matter if there was.

Nowadays both will probably have f*cked bushes in the rear beam which makes them sloppy anyway.

[pnd]

two door will be marginally more rigid and more importantly lighter. But a 4 door would be fine especially if its a pre88 car with the high compression engine.

[moggy]

thanks

[SHAKEELE30]

A 4 door all day long, incase you smash the car at least you can climb out the back....

[northloop]

two door will be marginally more rigid and more importantly lighter. But a 4 door would be fine especially if its a pre88 car with the high compression engine.

How much lighter is a 2 door than a 4 door and why is a 2 door more rigid?

Mine is a 4 door and it seems to do ok for itself.

[Paynts]

Where did you get pics of that 23rd Feb Bedford day? I have been looking for a gallery

[northloop]

Extreme sports photography were the official photographers on the day. Plus Louise over on Northloop took around 2000 pics. The one above is one of hers.

[moggy]

Nice photo

Car is now bought-picked up this morning.

The first job is done-I spent all day getting rid of 20 years worth of muck from the inside of the car and from the engine bay.

second job is to change the shat 18's that are sat on each corner. Then it's going to need an alignment doing as the rear passenger side wheel is way out-at a guess 10 deg pointing outwards.

2rd job will be to get the car checked over and to change the brake fluid and engine oil.

Then hopefully ready for its first track day...

[BMracing]

How much lighter is a 2 door than a 4 door and why is a 2 door more rigid?

A lot of 4 door cars are more rigid than their 2 door equivalents, and I believe the e30 is one of them.
There's probably not a lot in it but I think its important to know that you shouldn't dismiss 4 doors thinking the 2 door will perform better.
Our 4 door is also intended for track use although we haven't got round to doing many yet.
Also the 4 door only weighs about 15 kgs more than a 2 door equivalent iirc.

[Yaninnya]

How much lighter is a 2 door than a 4 door and why is a 2 door more rigid?

BMW publicise 20 kg between two and four door. And why is more rigid? Imagine the bare shells of both (without doors) and it shoud answer your question.
Jan

[Yaninnya]

A lot of 4 door cars are more rigid than their 2 door equivalents, and I believe the e30 is one of them.

Where you get such a piffling informations? I'm 38 years old and for over 25 years I never heard about any car which was more rigid in four door version.
Jan

[BMracing]

Just word of mouth really, its not something i'm really going to able to prove! I'm imagining the bare shells and i'm guessing its because a 4 door has 2 small door frames on each side which could be stronger than having 2 larger frames on each side. But obviously this depends on how the chassis is designed where the back doors would be on the 2 door.
Like I said it won't make a lot of difference on an e30 anyway because the 2 and 4 door are so similar, unlike say the e36/e46.
From what i've heard though, the e36 chassis is more rigid in 4 door form.
Some people share this view on these threads:

http://www.dtmpower.net/forum/e46-m3/47 ... -door.html

http://forums.bimmerforums.com/forum/sh ... edan+coupe

[Yaninnya]

O.K. as I have car oriented educational background I will try to explain.
Try to reckon the car shell as cage. As more bars you are puting in to that cage it is going to be more rigid. That is why roll cages in racing and rallye cars are more and more complex. Any "hole" in that cage is a potential weaknes of it. And any door is a hole in structure of shell "cage". That is the reason why car producers start to glue screens to the body. I hope that it is not a double Dutch.
And notice that all comments in that links are "they also say 4 doors handle better because they are a more rigid chassis", "i always thought the reason they use 4 drs in motorsport is because the roof and door frames are stiffer than in a 2 dr. makes sense when you look at it", etc. Just guessing, nothing else.
Jan

[northloop]

All interesting stuff, but it will mean the tidy part of nothing to the humble track day goer

[1an]

Nice photo

Car is now bought-picked up this morning.

The first job is done-I spent all day getting rid of 20 years worth of muck from the inside of the car and from the engine bay.

second job is to change the shat 18's that are sat on each corner. Then it's going to need an alignment doing as the rear passenger side wheel is way out-at a guess 10 deg pointing outwards.

2rd job will be to get the car checked over and to change the brake fluid and engine oil.

Then hopefully ready for its first track day...

i take it you realise that the rear suspension isnt adjustable?

[moggy]

I'm not changing the suspension?

[1an]

thre is no adjustability in the rear trailing arms, so if one side is toe-ing out by 10degs liek you say there is something wrong,

[moggy]

Thanks-actually 10 deg was a gross overstatement. More like 1 deg toe out.

Will obviously need to sort before it goes near a track.

[1an]

most likely the bushes have been anialated,

[moggy]

I wouldn't disagree.

[Yaninnya]

All interesting stuff, but it will mean the tidy part of nothing to the humble track day goer

Sorry mate, but english is not my first language. What it means in more dictionary style language?
Jan

[Theo]

Jan, he means that any difference that may exist between the shells, is not significant enough to be noticed by your average trackday user.

Basically exactly what was said in the very first reply, but 6 days later.

[Yaninnya]

Totally agree. In my last post I just took a a crack to explain a lot of BS with rigid of car shell.
Just for track day car more important is lack of rust (as many other zoners mentioned it before).
Jan

[bss325i]

E46 and E36 saloons have a bulkhead/fire wall between the luggage compartment and cabin. The equivilant coupes do not as the rear seats fold flat to reveal an appature between these two sections of the body. This will effect rigidity.

[ric325i]

Just for track day car more important is lack of rust

with rust comes less metal = less weight joke.


me and jaffro are going to be building a 325i trackday goer and its a 4 door just because we have the spare shell.

for use the extra 20kg is bad but lets face it we are building a fun car not a professional race car.

for PBMW racing it would be best to have a 2door shell without a sunroof.
but thats for compertitions