Dishing Wheels, Drilling Rims, and Picking Vendors oh my!

[ihategeeks]

I hit a pot hole(more like sink hole) which bent my stock rear 9C 26'' rim. Also blew up my tire and tube, but that is another issue entirely.
I have the newer 9C with the flat faces. Non-disc, with a 7 speed freewheel.

I have been looking at the Alex DM24 , 36 hole rim in 26" , only problem I see with it is the presta valve hole. Given the frequency with which ebike tires blow up, and the unavailability of cheap presta tubes, I wanted to drill out the hole to put Schrader tubes on it. Does anyone have experiences with this process? Know what size bit I need for the job, tips, warnings etc?

Since I will be lacing the new wheel to the motor, I have a question about dishing. I have the spoke calculator results to work with. My assumption is I am dishing one side shorter, and the other side longer. On this site for a new (flat) 9c I have found that +1mm -1mm is what is suggested, so 18 long, 18 short then?

Also, maybe someone that has bought the highly recommended Alex rim could clear up this for me. On the Alex site the ERD of the rim is listed at 544, but everywhere else where you can actually buy it, it is listed at 547.

Finally, does anyone know of a good american vendor to get 13g spokes from? And should those spokes be single butted?

 

[wesnewell]

I'd suggest going to the DX32 rim if you are going to be using 2" or wider tires. It's a stronger and wider rim. As for spokes, one place of many.
http://holmeshobbies.com/Sapim-Stainless-Custom-Spokes.html

 

[dogman dan]

No dishing needed. Or at most a mm or so. Your spokes should be all the same length on that motor.

Drill the hole, use the old rim to get your size. You could carry a tube or the old rim into the hardware store as well.

Holmes hobby for the spokes. He can very likely do the sizing for you, once you tell him the motor, and the rim erd.

 

[Ykick]

21/64" drill bit will open up Presta stem holes to proper Schrader size.

I'm a fan of 13/14ga single butted stainless Sapim spokes. As DM suggested JRH can fix you up there.

 

[ihategeeks]

Presta tubes are cheap at my LBS, didn't realize that. So I won't be drilling anything.
I'm happy to hear I don't have to deal with different spoke lengths. I kind of figured it wasn't important as I was taking the hub apart today.
Just placed the order for the Dm24. The Dx32 may be too big for my frame and I already and close enough to the max at 2.0 tires I am content to stay at this size on this build.
Got my spoke calculation from justin's site using a 547 ERD single cross in a 9C. = 167.9mm
And I am about to shoot jh an email since to make sure I get the best spokes for my application.

 

[bowlofsalad]

I noticed the same thing about the noted ERD of the alexrim dm24. The way you are supposed to build wheels (based on what I've read) is you should first measure the rim itself and not trust whatever the manufacturer or anyone say, then buy the spokes based on that information. I am wondering if there is some known selection of rims ebikers typically use, pretty much all I've heard of is stock junk and alexrims. I don't know if you've considered other rims, but I assume there are some other options that aren't common knowledge.

 

[Chalo]

Sorry to check in late on this thread.

The ERD for DM24 in 26" is 544. Alex rims can always be checked for ERD at alexrims.com.

Ykick is correct that a 21/64" drill will do the valve hole, but I usually use a tapered hand reamer. The valve body is tapered anyway. Be sure to debur the hole with a countersink, scraper, or utility knife.

Don't use 13ga spokes. Just don't; they don't help. They don't break less often than thinner spokes when correctly built with quality parts, but they are harder on your rims, they loosen chronically, and they are a hassle to lace. 13-14ga spokes are better, if you have huge hub holes to fill. I'd go for 14-15ga spokes, with washers under the heads if necessary. 14ga straight also work fine if you can't get butted spokes in the right length. Get Sapim stainless spokes cut to your specifications for only $0.25 to $0.40 each at danscomp.com. They do any size, which is a huge boon to us with weird hub motors to lace.

For best results, use slightly shorter spokes on the freewheel side. The amount of dish is not automatic, though-- you have to do it yourself by tightening the right side spokes to a higher tension. You can use an in-between size spoke for all of them, and just let the amount that the spokes stick into the nipples vary between one side and the other.

Lace the spokes in a cross-one pattern with all the right side spokes on the outside of the hub flange, and all the left side spokes on the inside of the flange. This reduces the angular offset between one side and the other, and allows you to have more tension on the looser side.

Be sure to lubricate your spoke threads with something. Spoke Prep is made for that, but grease, oil, or PTFE pipe compound are all OK too. I use Spoke Prep on customer spokes, but moly grease on my own spokes. Put a drop of chain lube on each nipple where it passes through the rim, before you tighten the spokes.

If this is all new to you, consider letting a professional build your wheel. Hub motor wheels are advanced projects by wheelbuilding standards, and an experienced builder can come up with a wheel that will last longer and require less maintenance than you can. It would be better for you to learn with an easier wheel, like a normal front wheel with a non-disc brake hub. But if doing it yourself is more important to you than having the best possible wheel, read Jobst Brandt's book or at least Sheldon Brown's wheelbuilding tutorial before you start. Assembling a wheel is easy, but making one that will last takes more than just assembly.

 

[itchynackers]

This is the perfect thread for me, as I just ordered an Alex DM24 26" 36hole rim for relacing my 9c 8x8 (square cover) motor. The factory spokes started snapping (after 3 years of use). The bits of spoke are rattling inside the wheel now. My kid has lost 4 spokes now, and it is becoming hard to align the rim, so I will be relacing my very first motor! I'm just waiting on Johnrobholmes to confirm my spoke lengths. It does appear as the rim is offset a bit on these 9c motors (I have 3).

Thanks for the advice Chalo. I definitely need any help I can get.

Adam

ihategeeks: I'm computing 165.5mm spokes, and 167.5mm spokes. Is that what your are getting?

 

[bowlofsalad]

If this is all new to you, consider letting a professional build your wheel. Hub motor wheels are advanced projects by wheelbuilding standards, and an experienced builder can come up with a wheel that will last longer and require less maintenance than you can. It would be better for you to learn with an easier wheel, like a normal front wheel with a non-disc brake hub. But if doing it yourself is more important to you than having the best possible wheel, read Jobst Brandt's book or at least Sheldon Brown's wheelbuilding tutorial before you start. Assembling a wheel is easy, but making one that will last takes more than just assembly.

Have you read Roger Musson's book on wheel building? If so, how does it stack up to Jobst Brandt's book?

 

[ihategeeks]

ihategeeks: I'm computing 165.5mm spokes, and 167.5mm spokes. Is that what your are getting?

I ordered 168, appears to be working fine. Not sure why vendors say 547 and alex says 544, but I went with the 547 to get 167.9 and just had 168's sent, better to be longer than short.

The lacing process was not as hard as I anticipated. (just very time consuming) This is really one of those things that makes a lot more sense when you are doing it but not while you're reading about it.

Once I figured out how to do the single cross lacing pattern and where to start (past the valve hole) the process went ok. Even though my rim was not offset on the eyelets, it did not cause much problem. I was only a bit off vertical on 2 ends, and half the rim needed to be trued over the freewheel. Truing is very much intuitive, you loosen one side and tighten the other , the tighten side is the direction you want to move the rim. I used dogman's guide (ps dogman you rock) http://www.electricbike.com/lace-hub-motor/. It is not "perfectly" true, there is a small bit of wobble like a mm here and there, but since I am going to have to adjust everything in 50 miles anyway, I am happy with where it is for now, which is probably better than the stock rim ever was. I was honestly anxious about screwing this process up, it is not as bad as it sounds.
I just did a test ride and not a single chirp from the spokes at 45psi. Fresh tire is grippy as hell too. How rarely things go right the first time


So happy to have my bike back on the road. I had already burned through a half tank of gas

 

[Ykick]

Congrats on your 1st motor wheel build! I would dare say it's required learning if you ride a ton of miles.