Agreed, and don't get me wrong, I am sure many have had good luck with using torque arms, AND aluminum forks, but I just wanted to point this out again.dogman wrote:Welll, as the saying goes it depends. An experienced guy with a good appreciation of the forces involved can run a 1000 w motor safely on alloy suspension forks. But a careless type, with an ignored warning is going to bust his ass, as your friend did. No torque arms, and no C washers, garanteed fail. There's a problem but it aint the fork.
I now have around 6-7000 miles on front hubs, using either cheap steel forks or alloy. Never screwed it up, and never had a problem. People thought I was crazy running a front hub on solid cromo forks at 3000 w. It worked great. At about 4000w though, things got shall we say, a bit touchy, and I crashed out of the race. The forks are still solid and good as new though, because I made proper use of the torque arms.
I really have no worries about my install of a front hub with 1200w on alloy, but I can't help but worry about anybody else doing it if they don't have lots of experience with hubmotors.
The execption to the rule is lame 250 watt motors, that would be unlikely to have a problem.
The key thing is this, don't span a cup in the forks with an oversize washer. You MUST have a spacer washer, such as a C washer, or the nut will put spreading force on the dropout, cracking it. This is why Justin made the C washers.
I wish I did read this message a week ago. I started to use 2 years ago a 180W motor on my aluminion fork MTB. After a year a changed to a 250W motor and a week ago to a 500W Bafang BPM (with controller giving ~1500W). I just had 30 seconds to test drive this 3rd motor 500W Bafang BPM!! It just broke the aluminium fork dropouts and luckly it as just after a start so I were at no more than maybe 10km/h.LI-ghtcycle wrote:A friend of mine forgot that both suspension and aluminum front forks are a bad thing with front hub motor and learned the hard way!
That was exactly what I did on the only first 30 seconds I had the bicycle with me - I lift a bit the front wheel because it was funny to get it skidding, and when the wheel got to the ground/road, the wheel/motor went ahead and left me and the rest of bicycle to behind -- well, in reality I did jumped over the handlebars.dogman wrote:Something to think about, whether the motor is front or rear. Say you pop a small jump, the motor starts spinning faster in the air. Then when you land, that's going to be a serious spike of torque.
What do you guys thing of this?Assuming the battery is located at the rear of the bike, you get a better weight distribution (as opposed to a typical front wheel drive).
Also, practically you get a two wheel drive (rear wheel pedaling and front wheel motor assistance). A two wheel drive is better for use on slippery surface because you get better handling (Just like a four wheel drive automobile). Another thing is that the front wheel motor assistance won't cause any unintended wheelies on sudden acceleration.
For that, I agree. Yet, steep climbing doesn't benefit at all of a front motor, for it has no significant traction on 15% incline and up. The only advantage of a 2 WD is to share the heat, so it could climb longer before bust, and that is only if the climb is not too steep to let the front motor help at all. For climbing steep, nothing can beat high power on the rear wheel, and sharing the power with a front motor only steal some off where it is needed, along with adding weight in a discipline where it is so important to be light.motomech wrote:...
2WD drive definately has it's place, I.M.O.
For low-powered assist riding, my FWD has been great, no control problems at all.