arty dave

Hi,

I'm having trouble understanding gearing calculators so I would love some advice from those who are using these hubs. I'm currently riding a 3 x 7 exterior geared 26" wheel mtb set up as a commuter - I'm riding 90% bike paths/roads, 10% gravel/dirt paths. I ride around Canberra (capital city of Australia) where my commute is maybe 50% medium - medium hard hills, 50% flat. I'm almost never in my lowest 2 gears and rarely get into the biggest ring on the cranks. I want to put the hub onto this same bike - it's a '97 Giant Iguana. The original rims are becoming ...'untrustworthy'

What would you recommend as a front crankset for this hub? (I know I can't expect the same range as what I have currently)

Cheers,
Dave.

dabac

Tell me the tooth counts you're using now, and I'll look into it. IE, what are your chain rings? what are the tooth counts on the sprockets that you do use?

tcs

Is that hub an XRD5 or an XRD5(W)?

Dan Burkhart 

38 tooth is a pretty good happy medium. Given your wheel size and an 18 tooth sprocket, it would give you a gear inch range of 34.2 to 87.6.
You can easily tweak this up or down by changing the rear sprocket.
For example, by swapping in a 22 tooth sprocket, your gear inch range would be 28.0 to 71.7. Just about right for a commuter.
One caution here. I have read that the new wide range models don't stand up to hard mashing on hills. I have the old ball lock model and it's been working fine for several years.

arty dave

Thanks for the replies! Yes it's a (w), I hope it'll be OK up hills - but I'm a kinda light-weight guy so I probably wouldn't be mashing as hard as some. Thanks Dan that's pretty much what I wanted to hear 'Just about right for a commuter'. I'll post my current teeth set-up when I get home for dabacs advice.

So it sounds like it's fairly easy to get roughly the right sized front chainring (38T) and then play with 2 or 3 different sized rear cogs until I get the happy medium I want.

I'm excited about this hub!

I am a total internal hub gear noob though - and I've realised there are other things about setting up the hub gears that I dont know.

For instance should I use a SA crankset or will any brand do?
What thickness and type of chain should I use? - from the SA specs for this hub they talk about chainline for 1/8' and 3/32" chains - I'm guessing this must also correspond to the different thicknesses of chainrings?

Ummmmmmm I think thats all for now.

dabac

Not quite any crankset. First, you need to match the chainline. The sideways position of the sprocket needs to line up about right with the sideways position of the chainring. Offset sprockets can be flipped, chainrings can be mounted on inside or outside of the spider, different axle length bottom brackets can be used.
Then there's chain width. Least hassle is if you can match it all, sprocket width, chain width and chainring width. You get a tad better durability if you can run 1/8" through and through. Running a 1/8" chain on a 3/32" chainwheel is supposed to be a non-issue, but I've seen one example of a sprocket not accepting anything but the "right" chain - despite the pitch of the chains supposedly being the same.

fietsbob

26" wheel what cog is on the hub? NB:
The Hub cog is not fixed on the hub, you can change the size of it as well
13 to 22 tooth.. [mostly 1/8" thk]

the math:
SA 5 speed IG hub the middle gear is 1:1,
flanked by 2 reduction gears, 0.62, & 0.75:1

and 2 overdrive gears 1.33 & 1.6:1.. the inverse fraction.