E92 M3 auto - rolling..

[brianmorrison]

Not sure if anyone else has had a similar issue or not.
Have an E92 M3 coupe with SMG Gearbox.
When stopped at a junction/hill similar and the car stops, it only holds it for about 1 or 2 seconds after braking, then "releases" causing it to roll back. Any ideas/suggestions on what could be the cause?
Thanks

[Schermerhorn]

It's not a conventional automatic with a torque converter. It's a manual gearbox with two clutches.

[brianmorrison]

But should it roll backwards? There doesn't seem any way of holding it -like clutch control or how an auto would?

[zeDuffMan]

brianmorrison said:

But should it roll backwards? There doesn't seem any way of holding it -like clutch control or how an auto would?

Keep your foot on the brake? They do roll backwards, otherwise it's sitting there on the clutch pack for no reason. Keep the brakes applied and the clutch stays disengaged.

[brianmorrison]

OK thanks for that. Just wanted to double check it wasn't a fault while it's still under warranty.
Appreciate the quick replies!

[MajorBeef]

The DCT box only hold the car steady for a second or two, then releases it. After that it's a hand or foot brake job.

[Gruber]

It's not the box that's holding the car. It's the hill-hold brake assist feature. Nothing to do with the gearbox.

[cerb4.5lee]

This used to annoy me in our old TTS S-Tronic and that would roll back as well whereas the ZF6/8 slush gearbox will hold the car and not roll back in the same situation.

[rassi]

cerb4.5lee said:

This used to annoy me in our old TTS S-Tronic and that would roll back as well whereas the ZF6/8 slush gearbox will hold the car and not roll back in the same situation.

A DCT is a manual gearbox (and utterly brilliant), so if treated like such it makes eminent sense that it rolls.

[paulmoonraker]

Gruber said:

It's not the box that's holding the car. It's the hill-hold brake assist feature. Nothing to do with the gearbox.

This. My manual did it.

[jon-]

paulmoonraker said:

Gruber said:

It's not the box that's holding the car. It's the hill-hold brake assist feature. Nothing to do with the gearbox.

This. My manual did it.

My manual m135i does it too.

[api330]

As someone else has already pointed out its the hill start assist working, (Holding brake on,) If you try it on the flat you will see it does not hold the car at all,

[cerb4.5lee]

rassi said:

cerb4.5lee said:

This used to annoy me in our old TTS S-Tronic and that would roll back as well whereas the ZF6/8 slush gearbox will hold the car and not roll back in the same situation.

A DCT is a manual gearbox (and utterly brilliant), so if treated like such it makes eminent sense that it rolls.

The DCT is as far away as you can get from being a manual gearbox for me and not even close as you just flick a paddle and your left foot does absolutely nothing, and I personally prefer a slush auto to a twin clutch auto for the reason mentioned above.

I do appreciate that the DCT is quick shifting and does suit the characteristics of the E92 M3`s engine(low torque/high rev) better than the traditional three pedal and stick set up though but I don't regret sticking to the old fashioned way when I had my M3.

[TheHound]

cerb4.5lee said:

I don't regret sticking to the old fashioned way when I had my M3.

Really, you are always banging on about how you regretted your M3, which had a manual box!!!

[cerb4.5lee]

TheHound said:

cerb4.5lee said:

I don't regret sticking to the old fashioned way when I had my M3.

Really, you are always banging on about how you regretted your M3, which had a manual box!!!

I did wonder if someone would pick me up on that!! the manual gearbox wasn't great as most agree but I wanted to stick to a three pedal set up...the DCT in the M3 is the right way to go though for sure.