lacing a motor hub, spokes and watch outs

[Jean.Petr]

Hi All, newbie here!

I'm sure this topic has been well discussed elsewhere on this forum so maybe someone can send me the thread, wheel lacing!

I'm getting a MAC front motor (12T) and intend to get it laced into a 26" rim for my mountain bike. I won't try this myself (beyond my skill set!) and going to pass it to my local bike shop. However eBike conversions relatively recent this side of the pond and just wondering are there any tips I should pass on to the wheel builder, e.g. spoke gauge, tensions etc?

Thanks, JP

 

[emco5]

With a MAC, thicker 13G spokes would be a good idea [14G is the norm]. Two-cross lacing is common. Choose a quality double-wall rim. After 500 miles, have the spoke tension checked.

Some MAC specs and info are here https://em3ev.com/shop/mac-5001000w-motor/

 

[JRA]

Good advice above but here is a bit more.

Spoke length calculator: http://www.ebikes.ca/tools/spoke-calc.html

As said above a good double wall rim and wider the better up to a point of course. Depends on what size tire you plan on using in the end. Personally I would go tubeless as I am having terrific luck with it but 36h tubeless rims are hard to spec. Velocity does make some which also work well with tubes btw.

Spokes:

Sapim Strong's are generally recognized by e bike wheel builders as the best option and are readily available world wide, more or less.

http://www.sapim.be/spokes/butted/strong

I have them on two hub motors and they are problem free. One I had to use washers also though because the hub spoke holes were just a little too big for comfort and have been fine as a result.

Otherwise a good wheel builder should be able to build and tension the wheel as per usual. Also as mentioned with any wheel check it or have it checked after a few hundred miles and it gets a chance to get seated in then it should be good.

 

[Robie]

JP, See if this helps --
ypedal.com
Lacing E bike motors
Clk--Projects
Clk-- wheel building

 

[Jean.Petr]

Thanks guys, some great information here. I agree the Sapim 'strong' looks like the spokes to go with, they do reference suitability for ebikes on their site, "Strong is developed for specific and heavy usage such as tandem, e-bikes or heavy load use.." They too also have a spoke calculator tool http://www.sapim.be/spoke-calculator
On spoke tension is checking by hand pointless or is a meter the only sure way?
Are there any advantages for radial lacing or is cross the only way to go for front hub?
Finally, just wondering does anyone in the forum have experience with buying pre-made wheels with motors from overseas? Most of the suppliers state that they make 'quality' wheels but I read elsewhere that invariably these cheaper kits have poor quality built wheels.
My logic is that of all the parts of your newly converted ebike the drive wheel is the most important, so paying a few dollars more for a strongly built wheel that can handle the torques seems like money well spent! Or have I got my priorities wrong?

 

[JRA]

There is no way to calculate proper spoke tension for any given build, only guidelines. As I said any good wheel builder can feel the right amount and get it right using either feel or a tensionometer.

I would not use a radial lacing on any hub motor. The tangental aspect of a cross pattern gives a lot of strength to the drive forces of the wheel.

If you think about it all the manufactured bikes out there have pre-made wheels. So obviously there is some amount of success, but also you see people complaining about breaking spokes too. Parts make the wheel and skimping there can cause problems later. Use the best quality components you can afford and have it built by a pro. Then take care of it and it should last you many miles, or km's as the case may be.

This is the last front hub wheel that I built, Sapim Strong spokes (half black and half silver just for fun), 1x, 700c WTB i25 tubeless rim and a Grin All Axle 1000w motor. It has about a thousand miles on it now running tubeless 40c tires with no flats or wobbles.

 

[flymeaway]

and intend to get it laced into a 26" rim for my mountain bike

The only rim I'd recommend is the Ryde Andra 30 and Sapim Race spokes. Use a 2 cross lace pattern and a spoke tension between 1000-1200nm. I have built a large number of wheels and can assure you that using poor quality materials or poor building technique will lead to broken spokes. Also, make certain the spoke tension is uniform on all the spokes. Mismatched spoke tension is a sure way to promote spoke failure.

Court J.

PS...if you're buying the motor from Paul you can have him provide the entire wheel assembled. Although I'm not sure you can spec the Andra 30 rim??