Alfie gets a new chain tensioner

I have mentioned on previous blog posts the problems that I have with the Sora derailleur on my Alfine-11 trike.

You may, of course, ask: “Why does someone with an internal hub gear need a derailleur anyway?” The reason is that I have a triple chainring at the front of the trike and thus need a chain tensioner to take up the variation in chain length when changing these gears (plus when folding the trike as well).

When the trike was originally supplied, ICE felt that, as the Alfine-specific chain tensioner wasn’t rated for a triple chainset like mine, it would be better to fit a derailleur which could handle the different chain lengths, so they fitted a Sora derailleur.

This is how ICE explained fitting the Sora (when discussing it last week):

We used a Sora because it was a reasonable quality and price with sufficient capacity for the clearance needed (by adjusting the B screw)… Shimano also make chain tensioners for the Alfine but they say that the capacity is only for 16T total difference on the front chainset.

I have a 21 or 22T difference on my front chainset which is why they didn’t go for the Alfine chain tensioner.

However, I’ve had trouble with my Sora derailleur over the time I’ve had the trike. One problem is that the clearance isn’t quite right in some cases so the jockey wheel cage rubs against the plastic chain guard (carrier) that keeps the chain around the hub. You can just see the problem at the bottom of this photo.

8

There was also an appalling tendency, when removing the back wheel, for the jockey wheel cages to grab onto the chain guard and not let go. This was a problem for me when fixing rear wheel punctures or doing other maintenance that necessitated removing the rear wheel.

17

And this was ICE’s comment about the issue of the jockey wheel cage rubbing on the chain guard/carrier:

Normally the position of the top jockey wheel cage is set by the B screw and winding this in would move it away from the contact point (or away from sprockets). The Sora is designed for a largest sprocket of 27T. The plastic chain guard is less than that equivalent so the Sora should clear OK normally. However, that normal capacity is based on the biggest sprocket position on a cassette whereas the Alfine guard is in roughly the position of something like an 18T sprocket so the parallelogram action may be putting the cage too close.

What this means is that, on a normal bike, as you go to the higher gears at the back – the outer edge nearer the derailleur – there are fewer teeth. My alfine has 18 teeth at the back which is a lot more than some of the smaller chainrings at the rear and as the derailleur doesn’t move outward (doesn’t need to) it isn’t able to clear the chain guard/carrier properly. The Sora derailleur works OK but not brilliantly.

But the biggest problem, and the one that caused me to completely change the chain tensioner, was that my Sora derailleur completely seized up. These things, when on a usual bike, will be almost constantly moving, up and down the gears; on Alfie I cycle 95% of the time in the big ring and the other 5% in the middle ring, I don’t use the granny ring at all. This meant that the derailleur moved only a few times per ride. Combining this lack of movement with me cycling all through a snowy winter when our roads were well salted and by early February the derailleur was completely seized. No matter how much we oiled it and leaned on it, it wouldn’t move. The gear hanger that attaches it to the trike started bending ominously, too, and we were unable to separate the derailleur from the hanger, so it became clear I needed to do something about this.

This was the situation earlier today with the Sora derailleur. I have three photographs of its positioning with the front chainring in the large, middle and granny rings. The Sora derailleur should swing to the left of the photo as I ran down the gears – as you can see in the pictures below, it stayed put and the chain just got slacker and slacker. (The jockey wheel cage section did take up some of the change in chain length but could not cope with the full range of variation).

This is the Sora derailleur when the chain is in the big ring at the front
1 Sora in big ring

This in the middle ring
2 Sora in middle ring

And this in the granny ring – the chain hangs very slack to the right of the photo.
3 Sora in granny ring

Here are all three together (click to enlarge):
3 photos Sora

As mentioned above, I contacted ICE when I realised I was going to have to do some major maintenance on the derailleur to see what they suggested. Neil replied:

Not sure about taking it apart at the pivot for service. I think it may not want to come apart and we have never had a close look to see if that is possible. It is a relatively low end unit and may be riveted up for life. Soaking it in oil should free it up if it was going to but sounds like you have tried that.

He suggested that I buy a replacement Sora from any bike parts shop and fit that, taking careful note of how the original Sora was locket out (by ICE) when I bought the trike.

The next day I telephoned to order a replacement gear hanger and spoke to Neil at ICE (who had sent me the email with info about it all) and he had clearly been thinking a bit more about it all and wondered if maybe the Alfine tensioner might work better for me. Knowing that it didn’t have a wide enough range for a triple chainset is less of an issue if I only use two of the three chainrings (big and middle), and am only ever likely to use the granny ring when going up a colossal hill whereupon I would be going so slowly that a slack chain isn’t the end of the world.

We talked for a long time (Neil is excellent like that!) and he gave me lots of information about what to buy (there are two types of Alfine chain tensioner, I need the CT-500 and not the CT-510) and where to get them from (not currently available in the UK but were available from various German bike shops). He said they were just assembling another trike with an Alfine 11 and were putting a Sora derailleur on it but he would be interested to hear how I got on with the Alfine Chain Tensioner.

I ordered the gear hanger from ICE for just over £10 and the next day it arrived. I also ordered the Alfine Chain Tensioner CT-500 from Bike24 in Germany and it arrived two days later. It actually cost less than a replacement Sora Derailleur, 15 Euros.

And here is the chain tensioner – note that it comes with three shims to help align the tensioner to the chainline. I went for black rather than silver in the hope that it doesn’t show the dirt and oil as much!
4 new alfine chain tensioner

Before we started on fitting the chain tensioner I dealt with something that would probably have caused us lots of annoying splinters – a slight fraying of the gear cable on the Alfine 11. You can see a tiny bit of metal sticking up here. It seems impossible to have your hand anywhere near the back of the trike without that thin metal shard puncturing your finger!

5 alfine cable dodgy end

I had bought some smart red ferrules from eBay so, after trimming the spare cable (it was always too long) we put a nice smart red stopper on it.

6 new red ferrule

I had also done a major service of both brakes including cables (which also got smart red ferrules on, although I will need to replace both cables before next winter as they’re pretty grotty inside).

Anyway, time now to remove the old derailleur.

James was on hand to help me with this as I never seem able to undo quicklinks on the chain. He was able to separate the chain very quickly.

Next task was to take off the right hand side axle bolt and washer so that we could get to the gear hanger. The gear hanger is held on with a small screw.

7 removing gear hanger

Fortunately this undid very easily and wasn’t corroded like most other things I am servicing on the trike seem to be at the moment!

8 removing gear hanger

Off it comes, with its permanently-attached Sora derailleur.
9 removed sora

We fitted the new, shiny gear hanger and put the axle bolt back on (it helps hold the hanger in place).

10 new gear hanger

It was a very simple job to screw the alfine tensioner onto the end of the gear hanger. We squinted a bit at it and decided that the narrow shim (probably 1mm wide) might make things line up marginally better so we put that on, tightened everything up and then James started threading the chain through.
11 alfine CT added

James joined the chain back together and we pedalled the trike, going up and down the front chainrings to see how it worked. “Very well” was the answer!

What was nice was that there was no adjustment of the B screw (there isn’t one!) or any other things to line up – it was just a case of attaching it, re-joining the chain and all is done!

Despite Shimano’s recommendation that 16T is the maximum range, this tensioner seemed perfectly able to cope with my 22T range and in fact had even more movement possible at both extremes of its swing. It was also interesting to note that it doesn’t have any springs involved in the top pivot (where it is screwed into the gear hanger), the only springs are on the jockey cages to tighten those up. The pull of the chain is plenty to move the tensioner as necessary and the forces from the jockey cage springs move it if necessary.

Here you can see three photographs of the tensioner position when the chain is on the three chainrings at the front.

This is when the chain is on the big ring.
12 Alfine CT big ring

This is when the chain is on the middle ring.
13 Alfine CT middle ring

And this shows the position with the chain on the granny ring.
14 Alfine CT granny ring

And here are all three positions for the front chainring (click to enlarge):
3 photos Alfine

After another quick task (tightening the friction shifter on my front chainring bar-end shifters which was also looking rather corroded) Alfie’s fettling session was complete!

After a cycle ride of 24 miles I can report that the new chain tensioner works really well! It makes a slight noise when in the big ring (probably related to the fact that the chain is probably a little bit short) but in the middle ring and granny ring it is completely silent. It holds the chain much tauter, which is good, and the shifts all seem to work well. Overall I am really happy with this change and think it was well worth it!

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1 Comment

Filed under Alfie the Trike

One response to “Alfie gets a new chain tensioner

  1. Shimano do like to tell people that certain component’s are not compatible with others when the opposite is usually the case.

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