Why can't you tow the SE on a dolly with the front wheels off the ground?

I have no idea, but I do know when people have tried to run the car on dynos it gets really unhappy about putting power to the wheels when the rears aren’t moving even with traction control off. Perhaps a similar problem occurs when the rears are moving and the fronts are stopped? Perhaps made even worse by the car detecting something less than a car length ahead while going freeway speeds?

 

Puppethead and F14Scott (note: the preceding are links) speculate on this topic in the thread on Tow Charging. I'm sure MINI's not worried about scraping the SE's exhaust pipe when towing with the front-end elevated.

 

it's a good question.. the powertrain shouldn't be involved.. only thing I can think of is the weight of the car on two tires creating heat for the hub assembly over time..that is a lot of weight on two tires..*shrugs* good question.

 

I don’t know how to keep the car in neutral when it is turned off. It automatically puts itself in park. I know there is a way to push it when the battery is dead, so there must be some method.

 

There's a car-wash mode that allows the SE to roll, but it lasts for only a few minutes. OTOH, Park prevents the rotation of the front wheels only.

 

Doesn’t “neutral” require the car to be in standby?

 

Really? How is that activated?

 

It could be the parking brake. If you put the car in park on a hill, the parking brake engages automatically. The yaw sensor (or however Mini does it) may detect you are on an incline and put the rear parking brake on when being towed with just the front wheels off the ground.

To overcome that, you put the car in neutral but that means the car is on. Then, you have to deal with the regenerative braking. It engages the rear brakes with one pedal driving. It wouldn't be safe to have 100% of the braking force to be on the front because in wet conditions, the rear end would get very unstable and want to come around. Check your rear wheels for brake dust to see this. My rear wheels always get dirtier than the fronts.

So it is probably the combination of the parking brake and regenerative braking. That is my guess.

 

It makes sense, but I never knew that. If true, the benefit of regen braking is diminished in the interest of safety.

Couldn't the anti-slip braking controller refrain from activating the rear brakes during regen braking unless it detects the front wheels slipping?

 

The back-and-forth here is all very interesting, but if you’ve got a vehicle capable of towing a 3100 pound car, why not just rent a car trailer from U-Haul? I don’t think dolly-towing is advisable behind a motor home.

 

My wheels are equally as dusty so I'm not sure that's conclusive proof it's using rear brakes during regen. When driving with the windows down it's very easy to hear the brakes against the disk and I don't hear anything when using regen (unless the battery is full)

Also, I don't think front brakes cause instability. Sure the rear gets lighter but with no braking force, the rear tires can use the whole traction circle for lateral grip which seems like it would be less likely to spin...

I've heard about too much rear brake causing instability when the rears lock up or trucks with heavy front weight bias hydroplaning in the rear but I've only ever hear of too much front brake causing understeer.

 

I learned the hard way when I was a teenager driving too fast in the snow that you shouldn't downshift to slow down in a FWD car. As soon as I did that, the rear end happily came around on me. This was before the days of stability control too.

Cars have proportioning valves that control how much fluid pressure is applied to the front versus the rear. No stock car just applies the front or the rear brakes so I have to conclude that there is a small amount of rear braking on regenerative braking. Maybe I'm wrong too. I know I would design it to be safer and apply the rear brakes on decel.

 

Agree. It has to be smarter than simply dramatically slowing the fronts, even if the weight distribution isn’t too heavily front-biased on this car.

 

Between DSC and Electronic Brake-force Distribution, there’s always fluid moving to and from each corner of the car at all times.