Help! Giant DH Team/V2 Cromotor.

Obiwan007

1 kW
Joined
Dec 16, 2012
Messages
332
Location
Northern California
Hey, all. I am getting into the meat and bones of my current build and need some advice. The project is a Giant DH Team/V2 Cromotor/18s2p 16ah. So I was aware of the asymetrical swing arm of the Giant DH Team but when I first saw this frame the amount of offset seemed relatively small. I decided to try to measure it exactly the other day and used this procedure. I drew a straight line on a long piece of paper and set the bike on top of it. I then put the exact center of the bottom bracket on the center of the line. I then used a plumb bob off the center of the head tube an lined it up on the same line. So this gave me a straight line that passed from the center of the head tube, through the center of the bottom bracket and extending to the rear of the bike past the drop-outs. I then measured from the drop-outs to this center line on each side. I took these measurements with the Kiwi adapters installed so the left dropout distance becomes a little less. So I got a measurement of 50mm from the left drop-out to the center line and 82.5 mm from the right drop-out to the center line. So an off-set of 32.5mm!! That seems HUGE! To make things worse, the V2 Cromotor is apparently a centered motor configuration. My current problem for getting this completely figured out is that the Cromotor is apart on my bench right now so I can't take accurate measurements until I get it back together (have to replace two shattered magnets and am still waiting for the replacements). But if the motor is centered, as the liturature I have read says, then that means I have to make up 32.5mm in dish on the wheel build right? Using the various spoke calculators, 15mm was about the max dish I could get and that made the left side spokes almost verticle. I subpose I could put all spokes through the hub from one side to gain a few extra mm but that still leaves me pretty far from centered. So has anyone dealt with this issue? I can't be the first to use a V2 Cromotor on a Giant DH comp/team frame can I? When looking at the frame even now it sure does not look like that much off-set. I wanted to get a head start and order the spokes for the wheel build but now I feel like I need to get the motor back together and mounted to really get a good look at how it will center between the chainstays. I talked this over with GCinDC a little and he is running into the same issue with the H4080 motor he plans to install (apparently it is also a centered motor configuration). If anyone has any experience in this area I would sure like to hear about your experience. Obiwan
 
Ok, I think I just had a revelation about this issue and I am hoping that the list can check me on my thinking here. So in the above method of measuring the rear swing arm off-set I came up with a difference of 32.5mm between the measurement from right drop-out to center line and left drop-out to center line. This means simply that the right drop-out is 32.5mm further away from centerline than the left...correct? Here is the revelation part, if my hub motor is mounted between drop-outs and I adjust the dish to move it 1mm leftward toward the center line then it would have moved 1mm AWAY from the right drop out and 1mm CLOSER to the left drop-out. This is, in effect, a 2mm swing in the measurement. So as an example, if my rim were to be built with 16.25mm of dish toward the left side, the 32.5mm of swing-arm off-set should be eliminated and the tire should run on the center line of the frame. Do, I have this straight?
 
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