138mm in 135mm Aluminum dropout?

[MikeSSS]

Wife's Townie is 7 speed freewheel hub in the rear 135mm dropout, the frame is aluminum.

The Bafang G310 rear hubmotor has OLD spacing of 138mm, 138mm is about 2.2% wider than 135mm.

I'm thinking this small percentage of spreading will not cause problems for the aluminum frame, especially since it won't be spread and unspread very many times. It won't have a lot of spreading and unspreading cycles.

Typical use for this bike will be around 100 miles a year, expected use life is about 8 years.

What do you think?

Thanks, Mike S

 

[cheapcookie]

"Axle OLD: The rear G310 motor has a 138mm rather than 135mm axle OLD. Spreading a 135mm standard bike dropout to 138mm is generally no problem, that's just just 1.5mm on either side and can stretch by hand with minimal force " https://www.ebikes.ca/product-info/geared.html
If you need more info I would contact them.

 

[999zip999]

Just stretch it by hand or if you want to complicate it now go get a scissor car jack put it between the two dropouts and expand it that way.
Do put a torque arm on one or both sides.

 

[mystryda]

Just stretch it by hand or if you want to complicate it now go get a scissor car jack put it between the two dropouts and expand it that way.

Since the frame is aluminum, DO NOT attempt to "cold set" the dropouts by spreading them wide until they relax to the width you want. This is a technique that can be done with steel but not aluminum.

Handspreading a 126mm frame to accommodate a 130mm hub is common in cycling, and this is less of a difference than that. Just gently spread the frame when you mount the axle and you'll be fine.

 

[MikeSSS]

I won't cold set an aluminum frame.

I did have a 130mm steel frame that I used with 135mm hubs, it needed a little hand spreading every time I inserted a 135mm hub but that was never a problem, just a minor annoyance. I never bothered to cold set that frame, even though the bike was ridden a lot of miles and had many tube and tire changes requiring the hub to be removed and installed many times.

The plan here was to hand spread the Townie frame to insert the 138mm hub. The 3mm difference is a bit less than 1/8", just under 1/16" per side, so hand spreading should be easy. This is my wife's bike, chances are she may never have a flat during the life of the bike. She does not ride places having radial tire wire, thorns and glass on the ground. So the frame will have very few spread and unspread cycles.

Yep, the Townie frame is aluminum, the G310 will have anti torque tabs on both sides. Electra Townie Go bikes have the same frame or so it looks, and have either a mid drive or a rear hub motor. There are no external torque arms on their rear hub motors, it appears they use torque tabs. This factory method should work well for my wife's use.

I should have asked the question explaining it that way and asked if board members thought hand spreading the aluminum frame from 135mm to 138mm was OK. My bad for asking around the real question and not asking it directly.

The Townies low seat position has been a big help for my wife, it allows her to have both feet well on the ground when stopped. Today I looked at a men's Townie to see if it would have enough space for a Thudbuster long travel seatpost and still give me solid footing when stopped. It would be a bit better than the rigid bike and the full suspension bike I ride most of the time, but only a bit better. Planning the next ebike is a lot of fun, no wonder many people build several.

Have fun, Mike S

 

[MadRhino]

You know that your alu frame is good to spread, when it does return to its original width after the wheel is removed. If it does, it will last without any damage. Yet, spreading a frame dropouts does make a slight angle in disc brake fitting, that might need to be corrected with a spacer between the front of the IS mount and the brake bracket. I would fit torque arms each side, for it would help the spread to keep equal each side.

 

[MikeSSS]

The bike has rim brakes, but a disc may be added to make the hub motor less obvious.

I'm thinking the 138mm hub will be no problem.