# Alfine8 vs. 8-speed cassette gear ratios



## _CJ (May 1, 2014)

Over the course of building up my Alfine8 bike, I looked pretty hard at gear ratios. There seems to be a lot of people who have have a default answer as to why an IGH hub won't work for them....not enough gear for "serious climing".

So I calculated out final drive ratios of the traditionally geared 8-speed combination, and the final drive ratios of the Alfine8 I'm running for comparison.

Cogs on the rear are shown in parenthesis for the traditional 8-speed, and the equivalent for the Alfine8 assuming a 32 tooth front.

Traditional 8-speed with 32 front and 11-32 rear:

1st: 1.000:1 (32)
2nd: 1.143:1 (28)
3rd: 1.333:1 (24)
4th: 1.524:1 (21)
5th: 1.778:1 (18)
6th: 2.133:1 (15)
7th: 2.462:1 (13)
8th: 2.909:1 (11)

Alfine8 with 39x24 primary ratio (1.625:1):

1st: 0.856:1 (37)
2nd: 1.047:1 (31)
3rd: 1.215:1 (26)
4th: 1.383:1 (23)
5th: 1.625:1 (20)
6th: 1.987:1 (16)
7th: 2.306:1 (14)
8th: 2.624:1 (12)

Relative to the question of whether or not the Alfine8 has enough gear for "serious climbing", I have personally climbed Pikes Peak (14,114 ft, 11.2% average gradient) with a 24F/28R, which was the gold standard for many years in mountain biking. Ratio fo 24F/28R? .857:1, which is pretty damn close to an Alfine8 with a 39x24 primary drive.


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## PlutonicPlague (Jan 19, 2014)

I've got my Pugs set up with a 26 chainring and 20 cog. that's a 1.3 input ratio, and it has my 1st gear at 0.689, and 8th gear is at 2.093. This seems a little low. I originally had a 26/18 setup (1.444 input), but then 1st felt a little bit high (0.765) because I was still weak and recovering from my heart attack. Now that I'm stronger, the 26/20 setup feels too low! I'd rather just get off and push my bike uphill than have to spin too fast in 1st!
I'm going to try 26/19, (1.37 input) and see if that feels like the happy medium.


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## longroadhome (Aug 27, 2014)

I'm in the process of building my fatbike with an Alfine 8. This post is very helpful but the big question remains: cog / chainring size....grrrr. I had in my mind (purely arbitrarily) of using a 32/18. How does one go about this exactly and what does Shimano say on the subject??


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## _CJ (May 1, 2014)

longroadhome said:


> I'm in the process of building my fatbike with an Alfine 8. This post is very helpful but the big question remains: cog / chainring size....grrrr. I had in my mind (purely arbitrarily) of using a 32/18. How does one go about this exactly and what does Shimano say on the subject??


The Alfine8 has a minimum input ratio of 1.43:1, so as long as you stay above that, you should be fine.

My primary ratio is 1.625:1, and I've had no issues so far. I'm a big guy (200+lbs), and according to Strava I'm laying down some pretty big power numbers, so the hub is definitely able to handle some serious abuse at 1.625:1.

My best advise is to figure out what you want your lowest gear to be, and set your primary gearing based on that.

My gearing is based on a 26" wheel with a standard 2.1 tire. With the added OD of a fatbike tire, you might want to step the input ratio down a bit. My low gear is effectively 22.25 gear inches, so with a 29" OD tire, you'll need a .767 low gear ratio for the same 22.25 gear inches, which would be a 32 front with 24 rear....giving you a primary input ratio of 1.33:1, which is below the 1.43:1 minimum, but still within their 22.2 gear inch minimum, so maybe try a 32/22 and see how that works?

Relative to HOW to figure out the individual gear ratios, just multiply the hub ratio for each gear by the input ratio.

A8 Ratios:
https://en.wikipedia.org/wiki/Shimano_Alfine


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## Rob_E (Nov 22, 2010)

_CJ said:


> The Alfine8 has a minimum input ratio of 1.43:1, so as long as you stay above that, you should be fine.


Where does this info come from? I tried to find the "legal" cog/chainring combos and came up empty. I've heard other people mention a Shimano-specified minimum, but I haven't found it in the Shimano documentation yet.

I'm currently running 34/18, I think, so 1.78. Should be fine, and for commuting, it's right where I need it to be. But I plan on moving from a 700c wheel to a 26", so I might want to drop that ratio to compensate (although the 26" wheels will be a lot wider, so I might be pretty close). But for touring or off-road riding, I might want to go a little lower. I just can never find the published minimum ratio.


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## _CJ (May 1, 2014)

Rob_E said:


> Where does this info come from? I tried to find the "legal" cog/chainring combos and came up empty. I've heard other people mention a Shimano-specified minimum, but I haven't found it in the Shimano documentation yet.
> 
> I'm currently running 34/18, I think, so 1.78. Should be fine, and for commuting, it's right where I need it to be. But I plan on moving from a 700c wheel to a 26", so I might want to drop that ratio to compensate (although the 26" wheels will be a lot wider, so I might be pretty close). But for touring or off-road riding, I might want to go a little lower. I just can never find the published minimum ratio.


Not sure where you would find it in "official Shimano literature", but a quick Google search will lead you to many sources. 
Like this one --> https://phatdivide.wordpress.com/2011/09/22/internally-geared-hubs/

As for 700c vs 26"....a 26x2.1 is roughly the same outside diameter as a 700x20c, so there's probably not going to be a big difference unless you're talking fatbike.


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## Rob_E (Nov 22, 2010)

_CJ said:


> Not sure where you would find it in "official Shimano literature", but a quick Google search will lead you to many sources.
> Like this one --> https://phatdivide.wordpress.com/2011/09/22/internally-geared-hubs/


That's the problem I have. If it doesn't come from the official literature, then where does it come from? I've found many such references to what is and is not "allowed" as an input ratio for an Alfine 8, but I have never found that info on Shimano's site. And not for lack of looking. Prior to the Alfine 8, I used a Nuvinci hub and could always refer to the documentation to find what the approved ratio was. It's weird to me that
1) I can't find the published info for that hub
2) I can find many unofficial sources supplying the information, but never providing the source.

Probably doesn't matter since I seem to be higher than what people _think_ is the minimum, but it's still strange to me that I can't confirm a piece of information that should have been included with my hub.



_CJ said:


> As for 700c vs 26"....a 26x2.1 is roughly the same outside diameter as a 700x20c, so there's probably not going to be a big difference unless you're talking fatbike.


Not a fatbike. My 700s are 40mm, so a little wider than the 20 used for camparison, but the tires I'm thinking of using are also a little bigger, 2.3, so it will likely all work out. Still, I'd like to pick up a flat cog for the hub to replace the dished one, so I might go up a tooth or two just to make sure my low end is there when I need it.


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## PlutonicPlague (Jan 19, 2014)

I can't find any definite answer to this question, but there seems to be enough experienced opinion on the subject to make one cautious about setting the gearing up too low.
My 26/20 setup (1.3 input ratio) on my Pugsley actually felt too low in 1st gear. Currently, its at 26/19, which raised the input ratio to 1.368.
This still feels almost bit too low, even for crawling thru the dunes. Note that I said, "almost." A younger and stronger rider might want to be geared a bit higher.

I have my 29+ gearing setup at nearly the same ratio on my Krampugs (different bike) at 30/22. This feels too low, and I'm going to order a 21t cog to see what it feels like with an input ratio of 1.428. If that still feels too low, I have a 34t chainring and a 23t cog to try next. That would give me 1.478, which I suspect might be as high as I would want to go for this bike.

(edit): I can easily check out an input ratio of 1.5 by trying 30/20 on the Krampugs. (I have a 20t cog). The R wheel is now placed as forward as I could get it in the dropouts, so I might not even have to mess with the chain length. That would definitely give me a better feel for higher gearing than I've already tried.

Another bike that I have with an A-8 hub (older sg-s 500) is a Giant TranSend. Its rolling 700c x 40mm Continental Tour Rides. It was set up by Giant with 33/20, giving it an input ratio of 1.65. That feels about right for this bike.

Again, I'm an old fart of 65, and not as strong a rider as I used to be when I was in my 30's.


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## 1spd1way (Jun 30, 2006)

I have hauled my fat ass around for about five years on my Pug with a 30/23...love the hub. No issues or failures at all.


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## PlutonicPlague (Jan 19, 2014)

I suggest a chainring/cog combo that results in an input ratio of anywhere from 1.36 to as high as 1.5 for an A-8 equipped Pugs. I have tried 1.444, 1.30, and now am at 1.368 (26/19) on one of my Pugs. At 1.30 it felt too low in 1st gear, like I was spinning out at med/slow walking speed. 1.368 feels good for beach riding and crawling thru the dunes and woods.
My SS Pugs, aka "Graped Ape," is now a Krampugs with an A-8, 29+ Rabbit Hole rims, and Bombolonis. I have a 30t chainring and 22t cog on it now (1.364 input ratio), but I'm going to a 21t cog to get 1.428, which I feel will give me slightly higher top-end gearing for gravel grinding, without sacrificing any needed climbing ability. I'm fine-tuning my gearing for my own preferences, etc.

Another combo that looks really good for an A-8 equipped fat bike is 32/23, which is a ratio of 1.39 (I think that is the one that vikb said he liked on his Pugs).



longroadhome said:


> I'm in the process of building my fatbike with an Alfine 8. This post is very helpful but the big question remains: cog / chainring size....grrrr. I had in my mind (purely arbitrarily) of using a 32/18. How does one go about this exactly and what does Shimano say on the subject??


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## pursuiter (May 28, 2008)

_CJ said:


> Not sure where you would find it in "official Shimano literature", but a quick Google search will lead you to many sources.
> Like this one --> https://phatdivide.wordpress.com/2011/09/22/internally-geared-hubs/


That link leads to a poor soul that listen to Aaron Goss, Aaron is clueless. One of Aaron's classic statements is that you can't stand up on the pedals for any Shimano IGH. Aaron freaked when he heard some of us are running primary gear ratios as low as 1.13 without issues. He was run off of this sub-forum a few years ago and now he hides on on the Yahoo IGH group.


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