Sticky Pro Connect Gears

[tillson]

Pro Connect gears sticking.

On the way to work this morning, after about 5 miles, (-4.7 deg C) I found that I could not select a gear lower than 5th. The change cable went slack as I changed to a gear lower than 5th.

When I arrived at work, I examined the mechanism on the rear hub and found that the cam on which the gear change cable pulls was very stiff. It was reasonably free at the point where the cable is at full tension (8th gear) but as the tension was released (changing down) the cam gradually stiffened up until upon reaching 5th, the spring would not move it any further.

I left the bike in the hangar near a heater for an hour and when I went back to it, the gear change had freed up and worked perfectly.

I can only think that whatever lubricant is used inside the hub had become more viscous due to the cold weather to the point that things started to become sticky. Is this a reasonable explanation? Has anyone else experienced anything like this?

Dirt ingress was not the cause, I keep the bike meticulously clean and lubricated.

 

[flecc]

I can only think that whatever lubricant is used inside the hub had become more viscous due to the cold weather to the point that things started to become sticky. Is this a reasonable explanation? Has anyone else experienced anything like this?

They are greased in manufacture and the grease will harden in extreme cold, so that's almost certainly the problem. Hopefully we won't get too much more of this extreme cold, but with time and use the grease tends to break down and lose some of it's structure so next winter could be ok, even if very cold. In addition, the routine degree of wear on the moving parts will allow more tolerance.
.

 

[tillson]

It all seems to point to the cold weather and the thickening of the lubricant. Although I have done 1400 miles now so I would have thought that things may be starting to free up. The bike has been inside a heated hangar for 10 hours today and I did a couple of laps indoors before setting off home this evening and the gears worked without a problem.

I had only been on the road for about ten minutes when the sticking started again. I was surprised how quickly this happened. I would have thought that with the thermal mass of the hub mechanism and the grease it would have taken longer to cool than it did. But having said that, it was -4.7 and with an airflow of between 15 to 20 mph over the hub I suppose it will cool quickly.

I tried turning the cam by hand when I arrived home and it is very very tight. Hopefully it will have freed off by morning as my garage is heated to +15. I'll keep an eye on it.

It looks like it will be pretty icy for the next few days!

 

[wotwozere]

Hi Tilson

wow you do laps in your garage and keep it heated at 15 that must be one great garage. My bike stays in the hallway on top of newspapers. Not sure it reaches 15 inside.

thx

Bob

 

[tillson]

No problems at all this morning (-1 deg) This is certainly a cold weather thing and -3 deg or below seems to be the temperature where the problems start. It's a bit of an irritation when it is stuck in a high gear, particularly when going up a few of the climbs that I encounter. I think I'll live with it and hopefully by next winter it will have freed off a bit.

I would be interested to know if anyone else has experienced anything like this at low temperatures with the 8 Speed hub gear.

 

[JamesC]

No problems at all this morning (-1 deg) This is certainly a cold weather thing and -3 deg or below seems to be the temperature where the problems start. It's a bit of an irritation when it is stuck in a high gear, particularly when going up a few of the climbs that I encounter. I think I'll live with it and hopefully by next winter it will have freed off a bit.

I would be interested to know if anyone else has experienced anything like this at low temperatures with the 8 Speed hub gear.

Tom
There is some good information on the Nexus 8 hub gear posted on the Dahon forum by Steveroot. Well worth joining their forum to be able to see all of the data.

The information on overhaul and maintenance is largely based on the SG-8R25 hub which uses the same internal parts as the WH-8R25 wheel assembly that is standard on the 2008 ProConnect.

Various members in the colder parts of the US write of the same experience that you have had in temperatures below -3 or -4 degC.

It appears that Shimano have never made a clear statement on the best maintenance procedure for the hub internals, the options being EITHER to cleandown and replace the hubgear white grease (item 38) OR cleandown and soke in the hubgear oil (item 40).

The grease is considered by some to be a little too hard for low temperature use; meanwhile the oil is considered to be a little too thin for warmer temperatures, keeping in mind that the hub is NOT a fully sealed unit on the drive side.

Certainly the grease should be limited to a very slight smear and can induce quite a lot of drag if used too liberally. Possibly best to degrease the hub thoroughly, soke in oil and allow to drain thoroughly, then finally apply a small amount of grease to the bearings.

Hopefully here in the UK, the occasions of very low temperature will be few and far between, so "standard hubgear white grease" which is so sticky at low temperature will serve well for the majority.


My own experience is limited to -1 degC using the SG-8R36 hub with no problems. The internals are slightly different, particularly the use of rollers rather than pawls in the freewheel section. Some of the differences are shown here.

It would be good to hear from members who have had the courage to venture inside the hubs.

James

 

[Danny-K]

Bear in mind though that Steve Root is a, (very), highly experienced Dahon owner and due to his knowledge, enjoys the same status on the Dahon Site as Flecc does on here. Personally I'd be too much of a scaredy cat to start pulling apart a fairly new Nexus 8 for overhaul; I'd chicken-out and pay the bike shop to overhaul it.

 

[tillson]

Thanks for pointing me in the direction of the forum James. That will be worth a look.

Hopefully this will be a very occasional problem because I don’t fancy stripping the hub down. I always end up with a few spare springs and washers when I dismantle anything like that!

 

[flecc]

I always end up with a few spare springs and washers when I dismantle anything like that!

No shortage of opportunities for that.

 

[JamesC]

Bear in mind though that Steve Root is a, (very), highly experienced Dahon owner and due to his knowledge, enjoys the same status on the Dahon Site as Flecc does on here. Personally I'd be too much of a scaredy cat to start pulling apart a fairly new Nexus 8 for overhaul; I'd chicken-out and pay the bike shop to overhaul it.

I appreciate that Steve Root is a hugely knowledgeable expert on the Dahon forum, and his work on the Nexus hubs is just one of many very interesting threads.

I am not a Dahon owner, and I can't say for how long the Nexus hubs have played a big role with the Dahon marque.

With the advent of the Kalkhoff range of ebikes, internal hub gears, in particular the Shimano Nexus/Alfine range, are set to play an important role on this forum.

The recent announcement that Wisper will have a bike out next year using an Alfine hub and a front wheel hub motor adds further interest.

At this stage, I think that you are right to warn members off from the innards of these things. For the next little while, most hubs in use are under warranty anyway.

But in time, there may be one or two members who gain proficiency and its always good to hear of their experience.

As always, the ebike market is only a small segment of bicycle sales. Standard mechanical bits such as hub gears will be discussed widely in other forums.

James