Mountain Bike Reviews Forum banner
1 - 8 of 8 Posts

·
Church of the Wheel
Joined
·
749 Posts
Discussion Starter · #1 ·
Okay, apologies in advance for asking a question that I'm certain has already been answered here...somewhere. Alas, my search-fu must be weak because I could not find the secret knowledge.

So what I need help with is figuring out a chainring size to go with my new (to me) Alfine 8 speed hub. I'd ideally like a gear range that's similar to a 32 tooth chainring with an 11-34 cassette, or perhaps a bit lower.

I tried to play with Sheldon Brown's gear calculator, but either I'm stoopid (entirely possible) or the calculator doesn't work for IGH's.

Any help is appreciated.
 

·
Registered
Joined
·
56 Posts
Alfine gear ratios are 0.53, 0.64, 0.75, 0.85, 1, 1.22, 1.42 and 1.62 so if you want your low ratio to be 32/34~=0.94 with a 32 teeth chain ring, you're gonna need 0.53*32/18~=0.94 an 18 teeth sprocket.

32/18~=1,77 of primary ratio so you're very close to the safe side of how the hub can be configured. There is no consensus on MTBR (and never will be) on how low can one go, typical Shimano recommendation for their other hubs is 1.9 or 2. I ride 38/21~=1.8 and the hub (Nexus SG-8R36) does not seem to be overtorque'd at all (although it clunks occasionally when powershifted, solution: don't powershift). Others ride 32/22~=1.45 and report the hub alive. Someone apparently blew it at 26/20.
 

·
Registered
Joined
·
81 Posts
mtb143 said:
So what I need help with is figuring out a chainring size to go with my new (to me) Alfine 8 speed hub. I'd ideally like a gear range that's similar to a 32 tooth chainring with an 11-34 cassette, or perhaps a bit lower.

I tried to play with Sheldon Brown's gear calculator, but either I'm stoopid (entirely possible) or the calculator doesn't work for IGH's.

Any help is appreciated.
hi,

Try this excellent gear-calculator.com calculator.
It allows you to compare the different gearing options.
Just click and move the cogs and chainrings.
http://www.gear-calculator.com/#KB=...19,21,23,26,30,34&GT2=DERS&TF=85&UF=2075&SL=2
(Shimano inter8=Alfine)
 

·
Church of the Wheel
Joined
·
749 Posts
Discussion Starter · #4 ·
Thanks, gents!

@irrah, that gear calculator is brilliant!

@bikeisbetter, even better, now I see how to do the maths! Many thanks.
 

·
Master of None
Joined
·
1,462 Posts
I broke my Alfine 8 running 32/20. So guess what? I just built a Alfine 11 and now running 32/22!

Actually I think a brief incident of cable misalignment fatally damaged my Alfine 8. Time will tell how 32/22 lasts but I know that my bad knee thanks me!
 

·
M8 M12 M15 deez nuts
Joined
·
8,584 Posts
presslab said:
I broke my Alfine 8 running 32/20. So guess what? I just built a Alfine 11 and now running 32/22!

Actually I think a brief incident of cable misalignment fatally damaged my Alfine 8. Time will tell how 32/22 lasts but I know that my bad knee thanks me!
Curious, how many miles had you put on it before it broke? I am running a 32/16 and everything seems to have been running smoothly for the last 2000 miles; the previous 900 miles were running a 36/17.
 

·
Master of None
Joined
·
1,462 Posts
I would estimate around 800 miles before it broke. The 2nd gear pawl broke, disabling 2nd and 6th gear. I also had done some creek fording and had water inside the hub twice. The roller clutches would grind when there was water in there.

After removing the broken pawl, I rode it for another 500 miles after that and it is still working now, albeit without 2nd and 6th.
 
1 - 8 of 8 Posts
Top