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Old 10-22-10, 04:53 AM   #1
surreal
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SA IGH off-road?

So, i just saw sixty-fivers 3speed hardtail on a different thread, which got me to thinking:


How does the 3 speed do off-road? I've been thinking about trying such a thing with an x-rd3, if i can get some indication that it can run a 2:1 ratio, offroad, without it getting fried. Obviously, no shifting under load, but i was thinking of using it like a singlespeed, with options. IE, coast, shift to low before a climb, start pedaling. Crest the hill, take a breather for a second, shift into high, cruise down.

Any thoughts?

-rob
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Old 10-22-10, 06:14 AM   #2
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I think the new SA 3-speeds could probably take it, although you'd be better off with the rotary gear selector than with the indicator chain, because a) I think it uses a solid axle, which is presumeably stronger and b) the selector is inboard of the chainstay, so it would be less likely to get broken in a crash. The other issue might be the drum brake, you might want the XL-RD3 (90 mm drum rather than 70) as it's more powerful. There is now an SA three-speed with disc brake mounts on the shell though, you might try that instead.
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Old 10-22-10, 08:54 AM   #3
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I'm pretty sure SA advises against it; not to say it can't be done though.
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Old 10-22-10, 09:31 AM   #4
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The Sturmey guy on Facebook said they don't recomend any of their hubs for off-road.
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Old 10-22-10, 10:35 AM   #5
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Just riding un paved paths, seems not a huge stress, gravel roads , etc. but yea one end of the axle
drive side, is hollow.
bombing down a hill with drops and 'air' under you wheels, might break axles.


Rohloff axle gets a lot thicker in the center as It accommodates gear shifting controls and such

What kind of external ratios ... for chainring and cog may matter..
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Old 10-22-10, 11:13 AM   #6
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Quote:
Originally Posted by fietsbob View Post
Just riding un paved paths, seems not a huge stress, gravel roads , etc. but yea one end of the axle
drive side, is hollow.
bombing down a hill with drops and 'air' under you wheels, might break axles.


Rohloff axle gets a lot thicker in the center as It accommodates gear shifting controls and such

What kind of external ratios ... for chainring and cog may matter..
Another feature of the Rohloff that helps off road durability is the fact it does not have a through axle. The non drive side axle plate provides a bolt on stub, meaning the axle ends inside the hub.This means the axle itself is pretty much impervious to bending. One thing that will cause a gearhub to cease functioning is a bent axle. For this reason, the earlier suggestion of using the 3 speed with the rotary gear changer is a good one, as it has a solid axle.
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Old 10-22-10, 03:18 PM   #7
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rohloffs are awesome. for over a grand, they oughta be.

xrd-3 hubs cost, like, $80, so they fit my budget better. I like everyone's input here. Here are some thoughts that hit me as i read 'em:

I'm a 250lb kind of guy. I've rode 2 different singlespeeds off-road for awhile, with solid, nutted exles. Very nice. I've also ran *lots* of multispeed hubs offroad, typically on full-rigids or hardtails. all of these hubs have hollow quick-release axles. i've never bent an axle; i just have warped some rims on cheaper wheelsets. Now, i realize that the SA hub has a more-hollowed out axle, and i realize that the SA axle has flats for drop-out placement. This might weaken the axle, but i'm not so concerned about that as i am about the internals. I'm thinking (may be wrong) that the trouble comes in when one does a panic downshift during a climb, and all the torque during the shift fries the planetary gears or whatever. If i think of the shifting as more of a "big deal" switch to a different mode, where i may even stop-to-shift, i don't think i'll fry anything. But, I'm not sure.

The idea of the rotary-shifted rx-rd3 hubs is a good'n, although they cost about twice as much. I don't crash a lot, so i'm tempted to be stingy.

I was thinking of rockin' a 36tx18t ratio. This is all highly theoretical, as i've got a few other projects to complete before i start buying anything for this one. And, being as i have no frame yet... and mr.igh says his 8speed alfie runs crazy low gear ratios, and is bulletproof. Still, i like track ends and drum brakes more than track ends and disc breaks or sliding drop-outs. And, i despise EBBs... still, i'm just sort of pondering.

thanks.
-rob
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Old 10-22-10, 04:23 PM   #8
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A 2 to 1 input ratio used to be the minimum recommended by SA in their documentation prior to the sale to Sunrace. Probably still a good idea for all except the 8 speed hub.

People of the Op's size/weight used to both break axles and pawls on 3 speed SA hubs per my understanding, even on pavement if they did high torque style riding rather than spinning. In addition to the axle being hollow it has cutouts for sliding parts to reach from the shifting chain to hub parts outside the axle.
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Old 10-22-10, 04:58 PM   #9
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Hmmm, low mountain drive range, on my folder, is a 1.44:1 as the 54 is a 21.6t
with the planetary reduction gear engaged.
But I'm Old not trying to be a muscle guy. and it is a transportation bike anyhow..

15t is as big as fits in the frame on my old BrommieT

at least If I break something in there, I can always get AW3 parts ..

Last edited by fietsbob; 10-22-10 at 05:10 PM.
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