Front wheel traction on steep hills with front hub motor

[frank9755]

I've just been out for a very pleasant, leisurely ride on my wife's Tongxin bike, partly to test it out a bit more and partly because it was so nice out. I sought out the steepest hills I know of near to me in west London, which are in Harrow.

I measured the steepest of the hills - a road called Roxborough Park and then a path which continues on to the church at the top of Harrow on the Hill, if anyone knows it - as 35m of ascent in 250m, which 14% or 1:7. However, the last section is steeper, so possibly a 1 in 6 or even 5 - ie pretty steep.

The bike (175rpm motor in a 700c wheel) coped with even this hill. I put it in bottom gear and backed the motor power off slightly and it made it up comfortably at 5mph with me pedalling steadily but not breaking sweat. This was a hill which had completely defeated my wife's old Powacycle, and which my old Powabyke had only just got up.

I found that the limiting factor appeared to be not the power required to climb but the front wheel starting to lose traction from the incline shifting my weight back. Now this section has a fairly rough surface and goes through a dense covering of trees, so there was a fair covering of damp leaves, neither of which helped matters, but I could feel the front wheel lifting off and had to make a real effort to lean forward to get more weight over it.

I've discussed this before as a reason for preferring a rear wheel motor but not actually experienced it. Perhaps I could have backed the power off a bit more, but I didn't think of it at the time. The lightness of the Tongxin motor compared to say the Powabyke one doesn't help in this respect either.

Anyone else experienced loss of traction on steep hills?
If so, how steep was the hill when it became a problem?

 

[flecc]

Yes indeed Frank, and its something I've often remarked on as a potential disadvantage. I've experienced slippage on loose surfaces, gritty and muddy steep lanes and on wet autumn leaves on slopes over 12% usually.

This is worst of all on folders, their geometry leaving a rider's weight over the back wheel and very little weight on the front wheel, geometry very like the old Raleigh Choppers of years ago which kids gleefully wheelied all the time. In fact they can be bad even when rear motored, my Q bike when taking off on a short 1 in 4.5 (22%) test hill is very difficult to keep down and I have to stand on the pedals and lean forward over the handlebars. With a front motor it wouldn't be able to take off on that hill.

Another time when a front motor is very likely to create wheel spin on a steep or poor surface is when towing which I often do, the extra rear load and drag the cause.

And yet another is with heavily loaded rear pannier bags on a steep hill since the load is behind the rear wheel spindle and already wanting to lift the front wheel.

As I've often said in here, I much prefer rear hub motors despite the gearing disadvantages and both my bikes are rear motored. In fact as you know I converted the Torq 1 to rear motor by swapping the wheels to make the T-bike.
.

 

[AndyOfTheSouth]

That sounds like pretty good hill-climbing, Frank. Isn't the Tongxin motor supposed to be relatively weak?

You don't normally wear a polka dot jersey, do you?!?

 

[wurly]

You need traction control Frank

Yes i have had the front slip but it's usually on damp ground. It's never been bad enough to alarm me. I have also had the rollers slip when i wound the throttle open at low speed, (you can hear this horrible grinding noise) i don't do this any more!!

JohnP told me he has traveled over 4000miles on a tongxin powered bike. So they can't be that bad.

From what i can gather, some tongxins failed because of the way they were fitted initially to the forks e.g. forks were too narrow to fit the motor, so they were stretched. When the hub was tightened up the spindles were forced in opposite directions causing excess force on the outer drive ring.

Anything has a point where it will fail, maybe the tongxin hubs are somewhat lower than others? i guess if fitted properly and treated with a due respect they should last many miles.
(i hope).
I am liking them very much.

Mel