Alfine 11 speed Sprockets \ Gearing

[StuWW]

I've recently received my nice shiny new On-One Pompetamine Alfine Urban 11 Speed.


Pictures on Flickr


It came with a 48t front and a 20t rear sprocket fitted, after my initial test ride it was obvious that the gearing had too many high gears and not enough low ones!

Excuse my technical ignorance hear but would fitting a smaller front cog push the range of gears more in favour of the low gears. I appreciate the spread of gears would be the same but currently I get to 9th gear and would be happy if that was 11th giving me two gears that I may be able to gain on the other end of the range to assist when loaded for touring.

Hope that makes sense and isn't to much of a dumb ar*e question!

As for the hub, it shifts beautifully and having owned a Rohloff before, I'm tempted to say there is not much in it. Give me a months riding and correct ratio's before I make a final decision, but it certainly feels like a well made bit of kit!

Thanks in advance for any ones advice.

Stu

 

[rualexander]

Yes a smaller chainring would reduce your gearing. You could also put a larger sprocket on at the hub but changing the chainring would probably be easiest. A 48 tooth chainring seems way too big to me. I would change it for something like a 38 tooth ring, or even smaller, but I like to have a low gear for killer hills.

 

[Saundie]

I'm assuming your Pompetamine has this track chainset, rather than the Shimano S500 chainset that they list currently on the Pompetamine Alfine 11 page? I make this assumption based on my own Pompetamine, which came with that chainset and an 18t sprocket. If this is the case, you'll be limited to a low of 41t on the chainring, as that's the smallest available with a BCD of 144mm. Going down to 41t would still make a huge difference, though it's up to you to decide if it's worth the hassle.

As for the sprocket, assuming that the 11 speed is the same as the 8 speed, you can use a 22t or 23t Nexus sprocket. It's a frustrating job changing that sprocket though, so I'd go for changing the chainring first.

 

[StuWW]

Thanks for the comments guys...


The bike has an F Giomondi chainset.


If On-One are now speccing it with a 39 > 18 set up, how does that compares to the 48 > 20 on mine.


I'll be a bit gutted if I'm limited to a low of 41t on the chainring, because of the BCD of 144mm, as if I do need to go to say a 39 then I'll have to buy a new chainset.


I'll give On-One a shout and see what they say...

 

[Baggy]

39/18 would defintely give much lower gears.
If you've owned a bike with a triple before - 48 is like the big ring and 39 is like the middle ring, so will give you much better gearing for hills/twiddling.
Hopefully On One will just swap it round for you - if not, you won't have any problem selling the Giomondi chainset - they're beautiful!

 

[StuWW]

Thanks Baggy... looking forward to the Exodus this year, my fave ride. Missed last years as I was cycling across America and we all remember the year before!!! THE DELUGE!!

Lets hope I get these gears sorted else I'll be doing 90mph down Cheddar Gorge!

Stu

 

[Baggy]

Thanks Baggy... looking forward to the Exodus this year, my fave ride. Missed last years as I was cycling across America and we all remember the year before!!! THE DELUGE!!

Lets hope I get these gears sorted else I'll be doing 90mph down Cheddar Gorge!

Stu

We'll put the tea van across the road to help you stop!
It's August 13th this year so hope you can definitely make it. Hope you had a great time in the USA.

 

[MacB]

An easier way to compare is via chainring to cog ratio so 48/20 is 2.4 and 39/18 is 2.17, the higher the number the higher the gearing and vice versa. The Alfine 11 is a bit strange in the way it's been sold on complete bikes, I've seen more than one example of crazy high gearing:-

48/20 - about 34 to 140 gear inches
39/18 - about 31 to 126 gear inches

I compared the top 4 hub gears, Rohloff, Alfine 8 & 11 and SRAM I-9, interestingly, however you set up the ratios, you got very similar gearing in the main riding range. Off the top of my head it was 6 gears for the 8 and 9 speed and 7 gears for the 11 and 14 speed. Assuming the main riding range is 40 to 90 gear inches then:-

SRAM I-9 using a 1.7 ratio(the minimum) gives 6 gears from 40 to 85 inches, the other 3 are below 40 with a low of 25
Alfine 8 using a 1.9 ratio(the minimum recommended by Shimano on the Alfine 11, not so sure on the 8 as many seem to run lower than this for offroading) gives 6 gears from 40 to 83 inches, the other 2 are lower with a low of 27 inches
Alfine 11 using a 1.9 ratio gives 7 gears from 40 to 86 inches with 2 below and a low of 27 inches and 2 above at 97 and 111 inches
Rohloff using a 3 ratio gives 7 gears from 40 to 92 inches with 5 below and a low of 22 inches and 2 above at 105 and 119 inches

The Rohloff will go lower than the others, if you set it with a top gear of about 100 inches for touring use then it takes you down to 19 inches, but you still get 7 gears in the 40 to 90 range, just more little ones. Say a 40/16, or 2.5, gives 19 to 99 inches and places gear 11(direct drive) at 68 inches. This is where the Rohloff does really well as you then have a lot of low gears for touring. If you're not doing laden stuff then the Rohloff isn't so hot, unladen who needs 5 gears from 19 to 31 inches?

Personally I'd reckon on a ratio of 1.7 to 1.8 being the best mix for the Alfine 11 but I'll wait until others have used it at these levels before giving it a whirl myself, I know some have already gone with a 1.6 ratio which gives 23 to 93 gear inches. If you stick to no less than the 1.9 ratio then you get the same low gear from the 8 speed as the 11, the 11 just gives you two more high gears and you gain 1 gear in the general riding range. Just for reference a 1.7 ratio would give you 24 to 99 inches with 3 evenly spaced gears below 40 inches at 35, 31 and 24.

Obviously this is all just off the top of my head and I'm sure there's more detailed analysis available

 

[StuWW]

Thanks for everyone's input on this thread.

On-One picked the bike up and returned it a week later (today) fitted with an Alfine 39 t front chainset.

After a quick 10 miler today I can happily report the gears seem great, a far more usable range without the over gearing problem I had with the previously specced 48 t.

Now it's time to put this Alfine 11 to the test, will it be the ultimate do everything bike I've been after?

We shall see!

Stuart