Are coupes and 3 doors noticeably stiffer?

[Pentoman]

Does anyone else think that when they drive a coupe it seems to have a better 'seat of the pants' feel than a comparable saloon or 5 door hatch? I can't decide if it's psychological or a genuine noticeable feeling so am just wondering what other people have noticed. For a while I didn't think Coupes and 3 doors had any purpose at all compared to 4/5 door cars but am beginning to change my mind.

Secondly, what ways are there to give a 4/5 door that same stiff feeling of a coupe? Do strut braces do anything for feel? Roll cage? Welded doors!?

[John D.]

The E36 M3 coupe is not. Rare saloon version is supposed to be better steer because of this. (If what I recall reading in EVO is correct.)

[Frik]

John D. said:

The E36 M3 coupe is not. Rare saloon version is supposed to be better steer because of this. (If what I recall reading in EVO is correct.)

I'd love to see figures on this because I've always thought it was an urban myth. Two holes vs four slightly smaller holes?

[NiceCupOfTea]

It's all to do with torsional rigidity isn't it? Saab 900 2 doors are much stiffer than 3 doors because of the huge hatch.

You can put a brace between the top of the rear suspension turrets which should help.

[John D.]

Frik said:

John D. said:

The E36 M3 coupe is not. Rare saloon version is supposed to be better steer because of this. (If what I recall reading in EVO is correct.)

I'd love to see figures on this because I've always thought it was an urban myth. Two holes vs four slightly smaller holes?

I agree. Although I don't know what is built around those holes so could be true, who knows?

Only reason I mentioned it was as a strange exception to the rule.

[NickXX]

There was some data I saw floating about on the internet which suggested that the above was true, I cannot find it though!

For the e46, it was something along the lines of:

Standard Coupe
Standard Saloon
M3 Coupe

With the M3 Coupe being the stiffest. I think the M3 has various extra bracing including within the C Pillar.

There was a big difference between standard saloon with folding seats and standard saloon without too.

[MarJay]

NickXX said:

There was some data I saw floating about on the internet which suggested that the above was true, I cannot find it though!

For the e46, it was something along the lines of:

Standard Coupe
Standard Saloon
M3 Coupe

With the M3 Coupe being the stiffest. I think the M3 has various extra bracing including within the C Pillar.

There was a big difference between standard saloon with folding seats and standard saloon without too.

My E36 325i saloon has a huuuge thick brace behind the seats which does not allow for the seats to be folded. I too have heard that the E36 M3 saloon is stiffer than the coupe. The coupe is pretty similar to the saloon, apart from folding rear seats...

[Frik]

MarJay said:

The coupe is pretty similar to the saloon, apart from folding rear seats...

The saloons don't have them then? Then the myth might not be a myth after all.

[NickXX]

Oh - here we go guys: http://www.germancarforum.com/test-data/12334-list...

germancarforum.com said:

BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg

Higher is better.

Edited by NickXX on Tuesday 27th April 22:02

[g3org3y]

Frik said:

MarJay said:

The coupe is pretty similar to the saloon, apart from folding rear seats...

The saloons don't have them then? Then the myth might not be a myth after all.

That was my impression also, the E36 saloon being stiffer than the coupe owing to the large metal panel behind the rear seats.

Is this higher level of stiffness something you'd notice in day to day driving - perhaps not.

In the olden days of the E36, coupes came with sports suspension as standard, on saloons it was an option. As such, back to back I'd have thought the coupe would 'feel' sportier/stiffer however.

[Urban Sports]

I suppose it depends on the car.

This isn't exactly a scientific test, but there is not much in it!



http://www.youtube.com/watch?v=_fshWGQfeHQ

ETA: The saloon is marginally quicker during the timed laps.

Edited by Urban Sports on Tuesday 27th April 22:31

[Ozzie Osmond]

Strut brace - except in the most unusual circumstances these are a purely cosmetic addition. Typically they are either (a) not necessary, or (b) not stiff enough to have any useful effect.

Depending how a car has been designed there may or may not be a significant stiffness difference between 2-door and 4-door. For instance, a car whose rear seats don't fold down will often have a metal panel the full width of the car right behind the rear seat. Similarly the shape of the boot lid (more particularly the shape of car it closes onto) can make a big difference.

[checkmate91]

I'm sure I've read that two doors on each side as opposed to one creates a more torsionally stiff shell as the centre pillar has to provide for door closing (front door) and hinge strength (rear door) plus the pillar over the rear wheel arch on the multi-door example requires door closing strength.

However, my 2006 Ford Fiesta ST, which I believe had a factory specially prepped seam-welded body was absolutely silent over rough terrain, my current 3-door focus (2009 RS) creaks and groans over the same terrain.

[Jesus TF Christ]

Frik said:

MarJay said:

The coupe is pretty similar to the saloon, apart from folding rear seats...

The saloons don't have them then? Then the myth might not be a myth after all.

I recall the Accord Type R does not have folding seats (unlike lesser models) due to them being used as one big brace.

[fatboy b]

Pentoman said:

Does anyone else think that when they drive a coupe it seems to have a better 'seat of the pants' feel than a comparable saloon or 5 door hatch? I can't decide if it's psychological or a genuine noticeable feeling so am just wondering what other people have noticed. For a while I didn't think Coupes and 3 doors had any purpose at all compared to 4/5 door cars but am beginning to change my mind.

Secondly, what ways are there to give a 4/5 door that same stiff feeling of a coupe? Do strut braces do anything for feel? Roll cage? Welded doors!?

You can get 4-door coupes too.