Autobild on the 1 Series M Coupe - CF roof optional?

[meganon]

Is there also a DCT as an option? It was rumoured also by a German paper!

[Pete_vB]

I know a little about carbon roofs; I added one to my '69 911.

In that case the savings was 8 lbs.
We calculated the stiffness as the same or slightly better vs a steel roof.
The CG height of that car was reduced by a bit more than 3mm, or about 1/8". This has a similar effect in the corners to increasing track width by just under .5", as increasing track width and reducing CG height both reduce lateral weight-transfer in corners.

Since the 1M weighs more than my 911 the effect is somewhat less, more like .1"/ 2.5mm of CG height difference, or the equivalent of about .35" wider track width.
You can debate amongst yourselves if you can feel that difference in cornering, but either way it is dwarfed by the over 3" increase in track the the 1M has been given. This I think puts the CF roof in proper perspective- the extra track reduces roughly 10x the weight transfer in cornering that a carbon roof would.

Originally Posted by formula M

Your weight is already below the center of gravity, even if you have a 40lbs brick in your shirt pocket, that weight is resting on your lower back and seat, thus it's weight is transfered there...

This is not correct, FYI. When a person is in the car they are effectively attached to it. Unless they go straight when the car turns of course (which is only possible for a short period unless the window is open).

Once something is attached to the car it doesn't matter where it is attached, it's weight is calculated from its center of mass. IE the seats might be bolted to the floorboards, but you can't then assume that 40 lbs is *at* the floorboards, instead it acts a the center of mass of the seat itself. So yes, a taller driver or adding a 40 lb brick to your shirt pocket is going to raise the center of mass. Even adding a helmet to the driver and passenger nearly cancel out the effect of a CF roof.

On a competition car a CF roof is nice to have. On a street car I'd want to see what the option cost- I'd probably rather have a few sets of sticky tires personally.

[EmmDrei]

If I remember correctly, they gave us a bucket of screws to hold at the M3 (e92) presentation and told us, that that was the difference of the tin to the carbon roof. 10kg (22lbs) if I am not mistaken. But there is no tin roof. It's either sun roof or CF. Roll the windows down on an M392 and I am pretty sure your center of gravity will have been lowered more than effect of the 8lbs or even 22lbs on the roof.

Just try driving a BMW e93 on track. Roof up, roof down. You'll notice the additional weight behind the rear axle, when the roof is down but it's not the lowered center of gravity you notice. The car is faster with the roof up and that's not only due to aerodynamics.

It's a very minute effect. Something that makes sense to squeeze the last tenth out of a car. 99.99% of all drivers would NEVER be able to tell the difference driving cars back to back and will NEVER be able to make it stick in order to actually record it. The reason the M392 has it... imho just show. It's a symbol of technical excellence. Lift one of the front seats in an M392 and then tell me that the CF roof is there for performance reasons. BS!

[crzy4135i]

Originally Posted by Haywood

Don't want to add anymore fuel to the fire, but you need to argue the point about the weight. It's not just 8lbs, it's about 45lbs. less when you take OFF the sunroof. This does have a significant difference on the center of gravity.

But, as I posted an article from Top Gear, it would have to be added to other parts being substituted such as hood, trunk, etc.

Kurt, I hear your argument about not having proof, but I think you're not being realistic. Every car high-performance manufacturer is looking to reduce weight and will use lighter materials as CF and other metals. You can't say that an all steel Corvette will be the same on a track as a fiberglass version? It's just common sense.

You can buy aftermarket hoods and trunk lids. The carbon roof isn't something easy to install after you buy the car.

[Alpine*]

Originally Posted by crzy4135i

You can buy aftermarket hoods and trunk lids. The carbon roof isn't something easy to install after you buy the car.

Agreed.

But I think we must all be honest here, Fark it looks good if nothing else

Further, if, like the E92, it is a N/C option versus having a sunny roof, I'll take the CF.

[aus135i]

Originally Posted by AlpineM3E92

Agreed.

Further, if, like the E92, it is a N/C option versus having a sunny roof, I'll take the CF.

+1