Interview with Michael Wimbeck - BMW M3/M4 Project Leader

[bradleyland]

Originally Posted by BhamDavid

That finned diff probably isn't a good jacking point for the rear end. I hope there is another point that can be used.

Yes, I know the diff is not designed on any car for this, but I've used it for years on many cars without issues.

The M3/4 has specific jack points underneath.

[BhamDavid]

Yes, there is for jacking to change tires. BMW usually has a jack point under the front end for jacking both front tires at the same time which is useful for oil changes. At the rear I've used the diff to jack both rear tires at the same time for diff fluid changes and suspension work. The fins will not be a good jacking point for the rear.

Or are you saying that there is a rear jacking point that I'm not aware of?

[bradleyland]

Originally Posted by BhamDavid

Yes, there is for jacking to change tires. BMW usually has a jack point under the front end for jacking both front tires at the same time which is useful for oil changes. At the rear I've used the diff to jack both rear tires at the same time for diff fluid changes and suspension work. The fins will not be a good jacking point for the rear.

Or are you saying that there is a rear jacking point that I'm not aware of?

I don't know about a center jack point for the rear, but yes, I'm referring to the dedicated jack points. In general, you shouldn't jack up a unibody car by any area that isn't specifically designed to be load bearing. The differential is not designed to support the car, especially with independent rear suspension. All the load is supported on the sub-frame, wheel carriers, and struts. I wouldn't risk jacking my car by the diff, fins or no. Again, plenty of people get away with it, but I wouldn't risk it.

The rear sub-frame on the F8x is steel, so there should be a safe enough jack point somewhere back there, but I don't think the car comes with a dedicated center jack point in the rear.

[Fun of it]

Great video with plenty of technical details. Certainly defines just how advanced the F80 has become from prior M models. Loved the differential cooler.

Thanks for sharing.

[M3ryder55]

The solution for jacking up the car, even using the bmw specific jacking points, is to use a floor jack and put a hockey puck in-between. The reason for this, as I learned, even the bmw jacking points, will get damaged (those plastic gaps) from any floor jack (mine did) they eventually start getting deformed over time from the floor jack digging into it, the damage doesn't compromise the integrity or anything but hockey puck works wonders.

I never jacked up the car from the diff before, but I don't see why you can't, and if u fear damage to the fins just use a nice little hockey puck.

[Thurman Murch]

Did the e92m not have cooling vanes on the diff?

I give props to the CFRP driveshaft and directly bolted rear subframe and more rigid structure to provide better road feel and steering feedback

But how did this add or subtract to the nvh characteristics?

I also wonder it the active sound grows on your or becomes annoying... Nonetheless it sounds pretty cool and how it pairs of the exhaust from the cabin

[Exterminador]

It's great to see all of the engineering and planning they take on every single aspect of the car to create the total package! Very cool

[SYT_Shadow]

Are people surprised to see cooling fins on the diff?

The E46 M3 has those as well as the E9X M3. It's a trademark M feature

[bradleyland]

Originally Posted by M3ryder55

I never jacked up the car from the diff before, but I don't see why you can't, and if u fear damage to the fins just use a nice little hockey puck.

Just because you can doesn't mean you should. There are guys who can pull a semi with their teeth, but that doesn't mean you should.

While the diff is attached to the rear sub-frame, but it's not engineered to support the load of the car. With an independent rear suspension, the downward load of the car's weight is primarily transferred up through the shock supports from the wheel carriers and to the sub-frame through suspension members. The diff is attached by some pretty serious hardware, but it's still not engineered as a load bearing member, so it's best to avoid it when jacking the car up.

[bradleyland]

Originally Posted by Thurman Murch

Did the e92m not have cooling vanes on the diff?

Yep. Pretty much any car with a clutch based LSD will have some kind of cooling; usually fins on the diff.

[mashimarho]

A very good video!

[tooch]

Originally Posted by alpinweiss 335i

Curious as to how that would relevant.

He said they made the car much stiffer in the front for better steering feel and feedback. New axle carrier helped with the extra anchor points. He just didn't wanna say how much stiffer it would be than a regular series.I think its relevant because I wanna have a stiffer and more communicative chassis in an ///M than you get in the regular one

[GregW / Oregon]

Originally Posted by SYT_Shadow

Are people surprised to see cooling fins on the diff?

The E46 M3 has those as well as the E9X M3. It's a trademark M feature

Here are the E90/2 ones.

[jonasaurus]

Originally Posted by bradleyland

Man those components are beautiful. Interesting remarks, yet again, in how similar the coupe and sedan are from a performance standpoint. I wonder how this will affect sales of the two variants. How bizarre would it be to have the sedan outsell the coupe by a wide margin?

I also find it interesting that automotive journalists seem to favor the sedan. At the end when they discussed torsional rigidity, the interviewer remarked that "he could tell" [that the sedan was more rigid], yet the M spokesperson claimed that the difference is very small. I wonder what it is about the sedan that is enchanting so many journalists?

Performance wise the difference between the E92 and E90 M3 was marginal but I'd find it hard to see the F80 outselling the F82 despite the seemingly added attention its getting. Agree with you though that it would be bizarre if the sedan did outsell the coupe.