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Old 03-18-10, 06:41 AM   #1
Derailed
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DH-3N80 for Touring?

Anyone using Shimano's DH-3N80 light-weight hub generator? I'm willing to pay the 30% premium in price over the DH-3N72 to save the weight, but not if the weight savings comes at the cost of durability.

Also, are 32 spokes sufficient for a front wheel for loaded touring? It looks like I'd need to order from overseas to get the 36 hole version.
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Old 03-18-10, 10:45 AM   #2
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How long of a tour? I've got at least 6000 miles on a DH3n72 and it's still running great. The only potential problem with that hub, and I think the DH3N80 is that the bearings can't be serviced. So if your bearings go in the field you are a bit screwed. For a really long tour it is probably worth it to get a SON hub. They have a reputation for a very very long life. That's what I'm doing for my Panam trip.
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Old 03-18-10, 11:54 AM   #3
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As for which hub is more durable, I cannot comment.

I wouldn't worry about 32 spokes for a front wheel, since the flanges are wide and the wheel isn't dished. Rohloff says a wheel built on a Rohloff hub (available only with 32 H drilling, even for a tandem), since it doesn't have to be dished, is as strong as a dished wheel built on any hub with more spokes, be it 36, 40 or 48.

I have a standard grade Shimano dynamo hub on my commuter bike (HB NX-30) that now, with 9 years and over 10,000 hard miles on it, is showing no perceptible signs of wear. I wouldn't hesitate to take it on a long tour in its present condition.
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Old 03-18-10, 12:08 PM   #4
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RMH - so if I understand what you're saying (and please correct me if I don't), the spoke count is far more critical for the back rim than the front. Also...if the front is stronger, wouldn't that mean it would be the better area to put the majority of weight?

It seems like every question that gets asked here is extremely relevant to the build I'm contemplating...I was looking at this hub earlier today wondering if I should get the 36 spoke 72. Harris Cyclery had some good deals on these hubs.
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Old 03-18-10, 12:38 PM   #5
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Originally Posted by pasopia View Post
How long of a tour? I've got at least 6000 miles on a DH3n72 and it's still running great. The only potential problem with that hub, and I think the DH3N80 is that the bearings can't be serviced. So if your bearings go in the field you are a bit screwed. For a really long tour it is probably worth it to get a SON hub. They have a reputation for a very very long life. That's what I'm doing for my Panam trip.
I'm doing the Northern Tier starting in early July (~4300 miles). I currently have a DH-3N71 that I built up several years ago. I've used it for light touring and hard commuting and have been very happy with it. However, both the hub and the rim are near the 9,000 mile mark, and I'm nervous about touring with it. If I had to bet, I'd say it would make it, but I'm going solo and don't want to risk it. At the least I should swap out the rim, but am currently leaning toward replacing everything (I'm already building up a completely new bike for this tour). I would then just keeping the 3N71 on my commuter.

I've also considered the SON, but the price just seems so incredibly high.
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Old 03-18-10, 01:02 PM   #6
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RMH - so if I understand what you're saying (and please correct me if I don't), the spoke count is far more critical for the back rim than the front.
Hah, you know, I hadn't thought of it on those terms; but yes, I believe that's true. If you built a front wheel and a back wheel with the same rim and the same spokes and the same spoke number, but the front one has wide flanges and no dish while the rear one has the flanges closer together and the rim dished to one side, the front wheel will be the stronger of the two.

Widely spaced hub flanges are able to exert much more side-to-side force on the rim than narrow ones; rear wheels, especially with a cluster of five to ten cogs attached at one side, have much narrower flanges. Furthermore, the way they are dished means the drive side spokes can exert sideways pressure on the rim only under extreme tension. You can overcome that deficiency by increasing the number of spokes; but on the front wheel, where that deficiency doesn't really exist, you don't need to.


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Also...if the front is stronger, wouldn't that mean it would be the better area to put the majority of weight?
If wheel strength is your only concern, then yes. But more weight on the front wheel is going to change how the bike handles, and I'd consider bicycle handling a higher priority than wheel durability. Most bikes are designed to carry more more weight on the back wheel than the front, but it's a matter of balance that you can play with a bit to find what works best for you and your bicycle. There certainly are bikes that are built to carry more on the front wheel.

I wouldn't be shy about putting weight on the front wheel, just don't be stupid about it. A big half-empty bottle of water, for example, would be a dumb thing to carry on the front wheel. Evenly balanced and stable weight, on the other hand, should be okay. Experiment!
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Old 03-18-10, 01:41 PM   #7
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Hah, you know, I hadn't thought of it on those terms; but yes, I believe that's true. If you built a front wheel and a back wheel with the same rim and the same spokes and the same spoke number, but the front one has wide flanges and no dish while the rear one has the flanges closer together and the rim dished to one side, the front wheel will be the stronger of the two.

Widely spaced hub flanges are able to exert much more side-to-side force on the rim than narrow ones; rear wheels, especially with a cluster of five to ten cogs attached at one side, have much narrower flanges. Furthermore, the way they are dished means the drive side spokes can exert sideways pressure on the rim only under extreme tension. You can overcome that deficiency by increasing the number of spokes; but on the front wheel, where that deficiency doesn't really exist, you don't need to.


If wheel strength is your only concern, then yes. But more weight on the front wheel is going to change how the bike handles, and I'd consider bicycle handling a higher priority than wheel durability. Most bikes are designed to carry more more weight on the back wheel than the front, but it's a matter of balance that you can play with a bit to find what works best for you and your bicycle. There certainly are bikes that are built to carry more on the front wheel.

I wouldn't be shy about putting weight on the front wheel, just don't be stupid about it. A big half-empty bottle of water, for example, would be a dumb thing to carry on the front wheel. Evenly balanced and stable weight, on the other hand, should be okay. Experiment!
That sounds like excellent advice. My current plan is to go with a more randonneur style and place more weight on the front. The bike was an expedition style bike, so it's probably best ridden with pretty even distribution.
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