Do I need a Torque arm for steel front forks, too?

[Bohh]

Hi guys,

Purchasing a Ampedbikes kit and am wondering if I'll need a torque arm for the front fork if it's steel? Will be a mountain bike fork if that makes any difference. Also, if I do need a torque arm, do I need one for each side or just one? Planning on using this on a Steel Giant Boulder with front suspension fork.

Thanks!

 

[recumbent]

One of the highest powered ebikes on this forum never used torque arms on his steel bike.
Make sure you have the motor installed correctly and snugly, after the first few rides check front nuts, or just carry a wrench.
I use a 10mm wrench clamped to the fork for my torque arm and worked flawless for 3,000 km's. However there are a few good torque arms on the market now and i ended buying one of them for complete security. I will install it this winter for the next season of ebiking.

If you have a lower power unit, like 36-48volts, you do not need one, but it's advised for obvious reasons of twisting your spindle and wrecking your motor and controler, all for the savings of $20.
Just not a smart way to save money.

 

[dogman dan]

I've got 1400 miles on a similar powered motor with no torque arms. I run 36v on WE brushed motor on the cheap steel suspension forks. Some of the really big motors can do some damage though. The MAIN thing is to get nice flat contact on the washers and snug em up. Not 100 foot pounds though, so you don't strip one like I did. On some forks, a cup like shape will not fit the oversise hubmotor washers. Some file down, some use a lockwasher, whatever works to get a good flat contact for the washers and nuts. Cheap bikes seem to not have the problem as much as bikes with quick release hubs.

 

[Lessss]

YES, if you want piece of mind and safety. You wanna roll the dice every time you start your motor then no.

 

[John in CR]

YES, if you want piece of mind and safety. You wanna roll the dice every time you start your motor then no.

Ditto.

Those dropouts aren't designed to take any rotational torque at all, so why expect them to handle significant torque? Twisting and breaking a wiring harness is the least of the problems that can occur. Once it spins the axle can easily climb right out of those shallow dropouts. Imagine sitting on the saddle and your front wheel comes off, what happens regardless of speed? What if it falls off while crossing an intersection?

 

[rguy56]

You may not need a torque arm, but think about how you might find out that you do.

I rolled around a corner on my bike a few months ago, and the front wheel went straight. The low speed crash has given me a lot of pain that I wish I had avoided (torn rotator cuff).

Enjoy the motor.

Bob

 

[Lessss]

Same goes for spoked wheel or mag wheel. I prefer mag as I know spokes are not designed for rotational torque. In fact I believe most spoke failures on all bikes are likely caused by lateral forces not compressive forces.

 

[Mark_A_W]

I would have thought the forks on a Boulder would be Aluminium, even if the bike frame is Steel/Cro Moly.

 

[Bohh]

Thank you for all the replies. I've found out that it is Aluminum. Can I use it with a torque arm or is that a bad idea? Did it matter that it was a suspension fork?

 

[John in CR]

Thank you for all the replies. I've found out that it is Aluminum. Can I use it with a torque arm or is that a bad idea? Did it matter that it was a suspension fork?

I have AL suspension forks on my bike. I made it less than 10ft before both dropouts snapped right off, and that was with what proved to be improper torque arms. At least they held the wheel on, so all I lost was the wiring harness, and no face plant into the asphalt. The torque arms I initially had were a very strong stainless steel, but it was too thin. The torque arms didn't give, but instead cut grooves into the axle, allowing it to spin. I still use the forks, but made torque sleeves that slide right over the shock tubes and clamp on. At the base of the sleeves are steel dropouts cut into 1/2" thick steel plate, so they pose 0 risk.

John

 

[Bohh]

Thanks for the reply. I'd rather not risk anything then. Would this be sufficient? I will be using 36v. http://www.nashbar.com/profile.cfm?category=&subcategory=&brand=&sku=13284&storetype=&estoreid=&pagename=Show%20All%20Products