# Shimano Alfine primary gear ratio range?



## pursuiter (May 28, 2008)

The SRAM i-Motion 9 hub has a restriction on the primary gear ratio, 1.7 to 1.9 (frt chainring divided by rear cog). For example, with a 20T rear cog, the frt chain ring can be 34T (34/20=1.7), 36T (36/20=1.8), or 38T (38/20=1.9). I assume this is to prevent the internal planetary gears from being driven too hard. 

- Is there any similar restriction on the Shimano Alfine hub?


----------



## pursuiter (May 28, 2008)

Bump: Alfine/Nexus users, what primary gear ratio are you running?


----------



## rockyuphill (Nov 28, 2004)

All internal hubs have a torque multiplication limit. The Alfine hub is designed to be used with a 39 or 45T front ring and a range of rear cogs from 16-23T, so that would bracket the safe operating range for the Alfine. You can always try pushing it further, but as Shimano would say "you're on your own".

The hub also has a narrow chainline, only 42mm on a 135mm wide hub.

Bike Magic has a review on an Alfine equipped MTB


----------



## EGF168 (Aug 13, 2007)

Depending on what size rings you go for it will have the range of a 11-34T cassette which is basically what I will get with a 32T on the front and 18T on the back. I've ordered one for my Giant Trance, hopefully that will be more than enough gears for me.


----------



## pursuiter (May 28, 2008)

rockyuphill said:


> All internal hubs have a torque multiplication limit...designed to be used with a 39 or 45T front ring and a range of rear cogs from 16-23T, so that would bracket the safe operating range for the Alfine. You can always try pushing it further, but as Shimano would say "you're on your own".


I don't see any restriction in the instructions, all they say is you need to constrain the rear cog between 16-23. Taking your numbers, it would constrain the primary ratio from 1.7 to 2.9.

- Does the final wheel size effect this? I don't understand why the restriction is independant of wheel size.



EGF168 said:


> Depending on what size rings you go for it will have the range of a 11-34T cassette which is basically what I will get with a 32T on the front and 18T on the back. I've ordered one for my Giant Trance, hopefully that will be more than enough gears for me.


If the lower limit is 1.7, you could run a 32/19 to get a little lower gear.


----------



## pursuiter (May 28, 2008)

bumping this thread, any real world experience?


----------



## EGF168 (Aug 13, 2007)

pursuiter said:


> If the lower limit is 1.7, you could run a 32/19 to get a little lower gear.


You know it's against official posting guidelines to bump threads up right?  Anyway I tried the Genesis IO ID a while back with the Alfine and thought the 32/18 combo was fine for my type of riding but I'll find out soon if standing up and hammering it up the climbs will get me to the top of the steep bits.


----------



## pursuiter (May 28, 2008)

Here's my real motive: I want to run a 32/20 or even 32/22 and I want someone to tell me it's OK, they've got a million miles without any failures, most of them climbing a 25% grade in 1 gear  

Lacking any backing or understanding of the issues involved, I am going to run my Alfine with 32/20 on my HT 29er. As they say, "Ignorance is bliss"...I'll let you know how it works out


----------



## rockyuphill (Nov 28, 2004)

Destructive testing and evaluation has a long and vaunted tradition in mountain bike development. If things explode, take pictures. :skep:


----------



## juscruzin (Nov 22, 2007)

I run a 32-18 which gives me a lowest final drive of close to 1:1 on a 29er.
I am 150lbs and a strong climber and can ride anything that I ride with a conventional geared MTB.


----------



## bikeisbetter (Aug 15, 2009)

*The Alfine or Nexus primary ratio limit is 2.1?*

Shimano have been very specific about allowed minimum primary ratio for the Nexus 8 hub. The limit is 2.1

The reference can be found in their "Nexus trouble shooting manual", on page 11.

_Please check the gear ratio and add the grease to the brake shoe.
Shimano recommendation gear ratio (F/R) is 2.1_

Source:
http://www.ridesaint.com/publish/co...e.html/11) 8 Speed Trouble Shooting Guide.pdf

If this link no longer works, try googling a copy of the document:
http://www.google.de/search?q=nexus+8+trouble+shooting+manual

Since Alfine and Nexus 8 hubs are nearly identical, it makes sense to assume the limit stays the same as well.

Please note also, that almost any standard bike coming with either Nexus or Alfine, complies with this limit.

Still, a lot of people ride this hub set up with some 32 teeth chain wheel and 20+ teeth sprocket, yielding the ratio of 1.6 or even less, way below the limit, also asking for trouble. And yet few complained they had destroyed the hub with excessive torque. Why is that?

I believe this happens due to tolerance margins engineered into the hub. The manual provides the minimum allowed ratio but makes no assumptions about rider weight or whether she/he is using clipless pedals or not. Heavier riders generate significantly more torque at the crank, so do those using clipless pedals, especially when standing and pedaling. Both situation can also come together and the hub has to withstand such conditions. So, probably, riders of average weight, especially when not using clipless pedals, can go below the limit and the hub still does fine, up to certain point, especially if they don't pedal really hard.


----------



## anthony.delorenzo (Aug 17, 2006)

I phoned Shimano tech support with that question and was told no limits on gear ratio, go ahead and run what I want. 

My setup is 33x22, with 190mm cranks and a strong, 6'6" rider pushing the pedals. I don't think my hub is very happy but it has made it through two years now.


----------



## itsdoable (Jan 6, 2004)

bikeisbetter said:


> Shimano have been very specific about allowed minimum primary ratio for the Nexus 8 hub. The limit is 2.1
> 
> The reference can be found in their "Nexus trouble shooting manual", on page 11.
> 
> ...


Old thread!

Page 11 is in reference to trouble shooting your coaster brake, specifically "_Braking force is too strong_" - the lower your ratio, the stronger your coaster brake.

It also is a "recommended" ratio, not a limit.

As far as I know, there are no posted lower limits to the Alfine and Nexus hub ratios.

SRAM, Sturmy & Rohloff post a specific lower limit.


----------



## pursuiter (May 28, 2008)

bikeisbetter said:


> ....So, probably, riders of average weight, especially when not using clipless pedals, can go below the limit and the hub still does fine, up to certain point, especially if they don't pedal really hard.


Who you calling average? I'm running ~300lbs of rider/gear/bike through a 32x23 for two full seasons (clipless pedals, no less), what more do you need?


----------



## john_dalhart (Nov 6, 2009)

Because the input from various riders can and does vary, I'm skeptical of "sacred" input ratios.

I believe that since SunRace took over Sturmey-Archer they have discontinued recomending minimum input ratios.

Shimano sez of the latest SG-8R36 and SG-S501 8-speed hubs: "There is also a new torque limiter which will make it harder to damage the hub with too much pressure from the pedals."

JD


----------



## Surly29 (Jun 8, 2009)

*26 x 20*

I've been running a 26 x 20 setup on my Karate Monkey for over a year. I've been slowly adding overnight gear to the bike also with no problems. Pulled a 50 lb. trailer with it, the solid axle was very nice.


----------



## famicodo (May 8, 2010)

*Alfine dreaming...*

Hi all, newbie here.

have spent a happy tinkerers day on the Alfine SG-501.The task? OIL BATH and exploratory 'pandora' style survey.Actually nothing remotely like avator or blue weirdo's, but any ways it's late and I m unsuccessfully not being funny.

Thanks very much to the information from MTBR and it's constituents, I was made able to get the job done in hours, not days. The whole tool business thing can be quite a trap, but if you are willing to look outside the square for safe alternatives...

The process of fuel swishing and transmission oiling went well and there is an unmistakeable odour about transmission oil dont you think?!
The job was going real well until I went to reconnect the gear cable. For some now known reason, it was slack and unresponsive from 4th to 1st.I think I undid and redid the plan down to the split ring 3 times thinking I had not reset the many parts *bows to japanese extreme toy tendency* and Finally realized that the video I had watched on alfine wheel removal/punc. repair on youtube, had the secret.You have to toggle the little aperture with the hole in it, so that the yellow markers line up IE: 4th gear.At that point you reinsert the correct length cable and voila. I have ultimate stealth commuter.Well almost. I had originally designed to change out the 18T rear cog with a 16T, and since it was 11 AM on a fine and clear Saturday morning, The bath became a reality.

The instructions were a little oversimplified but provided you use initiative and patience it becomes clear. The feeling of riding round my block on a faster,smoother alfine hub was emotional. It is now so quiet, I laughed a little and scared myself.Thats how quiet it is people.*nods like it's a big big deal*

The cone wrench thing can be exchanged for ring spanners, provided you file the rounded 3mm on the first locking nut.This makes a flat linear surface like the next nut below it and gives ample 'bite' for the spanner. And I will not forget my trusty Vice. That made the job a breeze. I think I will be going ahead with plan to use 200W elec motor on this bike.It appears that the torque issue is in parralel to a MTB or roadie. Torque still must travel through crank/chainring/cogs/chain. So for my money the stresses are within limits no matter what style of hub when i think of it. Thats the current theory. Any one is welcome with cold hard facts to topple it's beauty.....

Just waiting on hollowtech spanner now so that 39t/18T becomes 44T/16T. Sheldon 'we must never forget' Brown has put on his website all you need to know about ratio's with his calculators and advice and I sure am grateful he was so obsessed with bicycles. I don't know how many times I have visited his site for answers. 
Okay. thats it, it's 20 after midnight.Pumpkin anyone?


----------



## famicodo (May 8, 2010)

*Alfine*

I'm running 44t and 16t respectively on 700C X 38 Alfine 501 with recent oil bath. It's smooth and quick shifting. The Schwalbe marathon plus at 100PSI is not bumpy either.Quite happy with following that advice too!!! As per numerous other posts, The ratio between 5 and 6th gear are a little off putting. i have a fave part of road for speed test, and found that 8th gear was a little too low even with a 200W motor doing me favours!! I think the gear inches are something like 120 with my current cog set... I may have to go back to the 18T rear cog.Thats the one with fancy black plastic sheath on both sides. The transmission oil bath I gave the hub has NOTICEABLY increased performance, but beware, it does void the warranty that a LBS gives with it when you buy it. I guess I didn't buy the darn thing to just ride round the block on....:thumbsup:

And today it rained real hard and that Hub proves it's worth. Shiny and silver and smooth. If only I could afford a Roll-it-off....you know what I mean.


----------

