Hub motor wheel building

[WheezyRider]

I'm looking to replace the rim that came with my rear hub motor kit, as spokes are beginning to fail and it is a very average rim anyway. So I've bought a decent rim, however, I'm finding it difficult to find a shop prepared to do wheel building with hub motors. The last shop I went into the guy said "We don't mess with that Chinese hub motor crap, we only sell mid drive e-bikes...we plug them into the laptop and they sort themselves out..."

I wouldn't mind experimenting with building the wheel myself, it would be a useful exercise as I've never done it before but I don't want to splash out on getting a load of spokes to then find I've calculated the spoke length incorrectly and I've then got to buy another load of the correct length

How successful have people here been in getting their hub motor laced into a wheel? Would anyone here be able to advise on spoke length for a given hub and rim set and spoke pattern?

 

[awol]

Everything you need to know about wheel building is in this excellent book (well worth the cost) and he has a spoke length calculator on the website too.

Wheel Building book for cycle wheels

Wheel Building, by Roger Musson. A complete guide to building and repairing wheels with over 90 color photos and CAD drawings.

www.wheelpro.co.uk

There is also sheldon Brown's great guide.

Wheelbuilding

A tutorial on how to choose parts for, build and true a spoked bicycle wheel

www.sheldonbrown.com

 

[Gavin]

If you decide to go down the professional route, don't let a few lazy bike shops put you off.

Spoked wheels aren't exclusive to pushbikes and there's some very talented wheelbuilders in the world of classic cars and motorbikes with transferrable skills.

 

[Nealh]

You need to input the details in to a spoke calculator.
https://www.wheelpro.co.uk/spokecalc/

You will need to know the rim ERD (effective rim diameter) this is the seat position of the nipple to the opposite side, the hubs spoke hole effective diameter.
For the lacing you will have to opt for 1x or 2x depending on the hub diameter used and the rim size.

A good lacing guide.
Use the same technique for a 1x or 2x, as the spoke length used for the cross determines the right hole it will go in to.

 

[Nealh]

. The last shop I went into the guy said "We don't mess with that Chinese hub motor crap, we only sell mid drive e-bikes...we plug them into the laptop and they sort themselves out..."

That's because they are box sellers and know nothing about ebikes and just sell the Chinese mid drive crap. They think Bosch etc, are built in Germany but all are Far East produced.

 

[Nealh]

[QUOTE="WheezyRider, post: 567242, member: 29386
How successful have people here been in getting their hub motor laced into a wheel? Would anyone here be able to advise on spoke length for a given hub and rim set and spoke pattern?
[/QUOTE]

Self taught here like most probably, my first foray was to dismantle and old wheel to practice on then went for it. You can true the wheel in the drop outs by using a cable tie (cut down) as a pointer, attach it to the chain stay. When done you can simply twist the pointer out of the way.

 

[Nealh]

If the rim ERD isn't specified by the seller two ways to get it.
1. Measure the rim inside in a couple of places to get the correct diameter and add 4 or 5mm for the rim wall thickness.
2. Cut down two old spokes the same length and screwed the nipple fully on, insert them in to the rim. Measure any gap between the two ends and add this plus the two spoke lengths together for the ERD.

 

[sjpt]

Good luck. I'm sure quite a few of us are interested how you get on, do report back.

 

[WheezyRider]

Thanks for your replies. The rim I have is a Ryde Dutch 19R:

Dutch 19 R - Ryde

The Dutch 19 fulfils a double duty as strong city bike rim and as sexy single speeder rim.

www.ryde.nl

The motor is a Bafang RM G020.250.DC 12

The other reason for this build is moving to a cassette rather than the freewheel of my current Bafang SWX, which is limiting me to 7 speeds and a 14 tooth smallest sprocket.

Do you think I will need to dish the wheel?

The current motor/rim combination has a crossing of two, which seems to bend the spokes through quite a bit of an angle at the rim.

My other e-bike has a crossing pattern of just 1 and that seems to give a much better angle at the rim.

 

[Nealh]

ERD is stated as 578mm for the rim.
You will have to measure the spoke hole diameter across the hub.
The spoke calc will give a spoke entry angle so if it need be adjust the cross pattern and recalculate.
CST will likely need some dish but you can do that in the dropouts easily.

Spoke/nipple angle wise yes you want them as straight possible though so likely with the SWX02 hub 2x should be ok, I have the slightly more powerful (180mm) Bafang CST in a 700c rim with 2x on a 594ERD rim.

 

[esuark]

I bought this for my 48v swx02 done 900 miles so far no problem https://www.ebay.co.uk/itm/For-SHIMANO-SRAM-DNP-Mountain-Bike-7Speed-Freewheel-Nickel-Plate-11-28T-Screw-on/164264508036?hash=item263eed7a84:g:W-IAAOSw9CNezyqv

 

[vfr400]

Using 145 mm as the spoke pcd and 42.5 mm between the flanges, my spoke calculator gives 237.8 for 2-cross. Because of the 5.6 mm off-set centre of the hub, you'll most likely have to off-set the rim, which would mean the exact spoke sizes are 238.4 mm and 237.4 mm; however, I always use the same spoke length each side regardless, so I'd go for 238mm spokes. I always use straight 14g, which are the easiest to get.

See if you can get approx measurements for the motor pcd and width to confirm those numbers, which I got from a Bafang drawing. Also, it's always worth measuring the internal rim diameter to validate the ERD, which should be about 5mm more, because I've had some rims where the stated ERDs were way out.

 

[WheezyRider]

Using 145 mm as the spoke pcd and 42.5 mm between the flanges, my spoke calculator gives 237.8 for 2-cross. Because of the 5.6 mm off-set centre of the hub, you'll most likely have to off-set the rim, which would mean the exact spoke sizes are 238.4 mm and 237.4 mm; however, I always use the same spoke length each side regardless, so I'd go for 238mm spokes. I always use straight 14g, which are the easiest to get.

See if you can get approx measurements for the motor pcd and width to confirm those numbers, which I got from a Bafang drawing. Also, it's always worth measuring the internal rim diameter to validate the ERD, which should be about 5mm more, because I've had some rims where the stated ERDs were way out.

Thanks for your calculations. This is the spec sheet for the motor:



Is it ok to use 14g spokes? Aren't they a bit thin for a hub motor? At the moment it has 13g spokes. On my other bike it has 12g spokes and they look nice.

Where I am the roads are awful, a few months back I hit a deep pothole with both wheels at speed and buckled both wheels. I managed to straighten them out enough so they don't foul the brakes, but this has probably accelerated the demise of the spokes! My frame limits me to about 40 mm tyre width, so I need strong wheels that can put up with a lot.

My other bike has 26" wheels, 12g spokes with a crossing of 1 and 50 mm wide tyres and a deep rim on the back. It seems to soak up the punishment without problems so far.

 

[WheezyRider]

I bought this for my 48v swx02 done 900 miles so far no problem https://www.ebay.co.uk/itm/For-SHIMANO-SRAM-DNP-Mountain-Bike-7Speed-Freewheel-Nickel-Plate-11-28T-Screw-on/164264508036?hash=item263eed7a84:g:W-IAAOSw9CNezyqv

Yes, I have one of those. I bought it to go on my other e-bike, but I haven't got around to doing anything with it yet. I have thought about putting it on my main bike. However, the quality looks ok, but not great, not sure how long it will last. I'm juggling projects and motors, and I've got this cassette version motor and anyway, I've bought an 8 cog Shimano 11T to er...quite big? to go on it

 

[WheezyRider]

ERD is stated as 578mm for the rim.
You will have to measure the spoke hole diameter across the hub.
The spoke calc will give a spoke entry angle so if it need be adjust the cross pattern and recalculate.
CST will likely need some dish but you can do that in the dropouts easily.

Spoke/nipple angle wise yes you want them as straight possible though so likely with the SWX02 hub 2x should be ok, I have the slightly more powerful (180mm) Bafang CST in a 700c rim with 2x on a 594ERD rim.

Thanks for that. So you think a crossing of 2 will be fine? I'll have to check the existing wheel again to see why the spoke angle is so severe. Maybe its a crossing of 3 and I'm not looking at it right.

 

[Nealh]

2 x gives a 11.3 degree spoke /nipple angle which is pretty good , 238mm is good for the spoke calc I used, 1 x is 6.4 degree angle.

14g is all I use, for spokes I use 'Spokesfromryan' and use Sapim Strongs a 2mm/14g spoke with a 2.3mm threaded end.

 

[vfr400]

14g spokes give a more comfortable ride, don't break so much and don't come loose. If you don't mind spending money, you can get the butted spokes with 13g ends and 14g down the main length. I've never bothered with them and I haven't had any problems.

Spoke thickness is counter intuitive. It's not a case of the thicker the spokes, the stronger the wheel. This was a mistake the trade made about 10 years ago. They had real problems with broken spokes. Nearly all are using 14g today.

 

[budsy]

I'm looking to replace the rim that came with my rear hub motor kit, as spokes are beginning to fail and it is a very average rim anyway. So I've bought a decent rim, however, I'm finding it difficult to find a shop prepared to do wheel building with hub motors. The last shop I went into the guy said "We don't mess with that Chinese hub motor crap, we only sell mid drive e-bikes...we plug them into the laptop and they sort themselves ou

That's because they are box sellers and know nothing about ebikes and just sell the Chinese mid drive crap. They think Bosch etc, are built in Germany but all are Far East produced.

Alls fine without going e bike route , as far too many problems iv heard re > e-bikes

I much prefer pedal power as then alls always good to go .

 

[Gavin]

Alls fine without going e bike route , as far too many problems iv heard re > e-bikes

I much prefer pedal power as then alls always good to go .

Out of curiosity, why are you on an ebike forum @budsy if you don't like ebikes?

 

[Nealh]

Out of curiosity, why are you on an ebike forum @budsy if you don't like ebikes?

He's been trolling dissing ebikes on the fora for the last couple of weeks, eventually he will get bored and bugger off as many do.