Author Topic: cog change/chainglider  (Read 2670 times)

hendrich

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cog change/chainglider
« on: August 11, 2024, 02:00:56 PM »
The rear chain on our Rohloff tandem was noisy when climbing mountains during our recent tour in Montana. Transmission noises on tour are annoying. When back home I noticed that the Rohloff cog was worn. Here is a pic of our cog at 20,000 miles. Beneath the cog is a new cog to show the significant amount of wear. The cog was flipped at 10,000 miles for the same reason, chain noise when climbing. It was difficult to notice the wear until comparing with a new cog.

I added a chainglider a while back. The chain life was improved by a factor of 2 (4000 rather than 2000 miles for 1/8” stretch). Over this time the timing chain is wearing as previously observed (change at roughly 9,000 miles). I was hoping for better than a factor of 2 for the rear chain with the chainglider. However, the worn cog may have caused faster chain wear. So will see if a new cog with new chain improves the lifetime.

I suspect it is bad practice to simply oil the chain through the hole in the chainglider. When I did this, and when riding on crush stone trails, the chain picked up a significant amount of dust. Probably still better to oil and then wipe off excess chain oil.

martinf

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Re: cog change/chainglider
« Reply #1 on: August 11, 2024, 03:29:34 PM »
20,000 miles for a cog on a tandem! The best I've got from a cog on a solo bike is 9700 kilometers (flipped, so that was wear on both sides), but it was before I starting fitting Chaingliders to my bikes.

I reckon a factor of two for chain wear reduction with a Chainglider is still well worthwhile.

As it is quite easy to unclip the two rear parts of a Chainglider I do that from time to time. Quite often the chain looks like it doesn't need any lubrication and I just refit the rear Chainglider parts. If I think the chain needs oiling and is reasonably clean I oil it and wipe off the excess, if it looks fairly dirty I remove the front of the Chainglider and the dirty chain, wipe the chainring and cog clean, put a clean chain on and refit the Chainglider. I clean the dirty one later. I now run 2 chains for each side of the rear cog and have not yet got to the stage of flipping the cog since I started using Chaingliders.

My initial trial was with a fairly worn transmission and the Chainglider significantly increased the interval between chain maintenance. But I reckon a Chainglider works better if you start with a new chainring, chain and rear cog when you first fit it.

Andre Jute

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Re: cog change/chainglider
« Reply #2 on: August 11, 2024, 08:02:35 PM »
On a solo bike a Chainglider near enough trebled my mileage per chain.The current cog is still on its first side at 11K km, and I see no signs of wear, so I suspect it will make 20K if the wear is symmetrical over mileage.

This is with zero service, as I run my chains to half wear, 0.5mm rather than 0.75mm, without any maintenance, service, or even oiling, operating solely on the factory lube for the life of the chain. I must admit though that I ride on clean roads almost exclusively; my chain is clean when I remove the Chaingilder, and so is the inside of the Chainglider (there's an astonishing photo on the link below); I wipe the outside of the Chainglider off with a cloth once or twice a year. There's a summary thread about my Chainglider experiment and experience by me and other forum members at https://thorncyclesforum.co.uk/index.php?topic=6813.0.

There are some factors with a tandem that obviously make chain and perhaps cog life too more strenuous than on a solo bike, and very likely some more subtle factors that those who do run tandems can list.

in4

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Re: cog change/chainglider
« Reply #3 on: August 11, 2024, 09:37:39 PM »
I'm curious ( comes as no surprise to some!) what's your chainring/sprocket combo Andre?

Andre Jute

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Re: cog change/chainglider
« Reply #4 on: August 12, 2024, 01:51:09 AM »
38x16 without a motor.
38x16 with a slightly underpowered motor.
44x16 with a motor putting out enough torque.

For anyone interested in the decision process:

The cog on my Rohloff bike was 16T throughout; it has been such a success that the spare I laid in is also 16T. Sixteen teeth is Rohloff's default supply unless some other tooth count is specified by the buyer. The 17T cog SJS offered as a default must thus have been a special order.

The first crankset was an Indian Amar 38T steel job, popular as a budget set in Germany, which I ordered to replace the default Utopia Velo arms that I thought aesthetically sub-optimal, while I considered what would really go with my bike. The cheap Amar 38T crankset was in fact on the bike, inside a Utopia Velo Country fully enclosed chain case very much like the Chainglider but considerably more fussy in construction and rather fragile too, for some considerable time. (The Country is described in my tour through the varying chain cases on this forum.) The Amar was replaced when I spotted some rust spots on the back of the cranks at about the same time as I found acceptable cranks; the Amar chainring had hardly any paint worn off it in a couple of thousand miles, partly because of the spot-on chainline and high quality chain (KMC). Almost simultaneously the Country self-destroyed, and I decided to give the Chainglider a go.

The second chainring was the well-known Surly Stainless Steel, also 38T, chosen because it would fit inside the Chainglider and would presumably last forever, because I was already thinking about what was required on a zero or near-zero maintenance bike.

The Surly never got a fair trial. It was unmarked when it was replaced at 3600 or so kilometres because it couldn't be made to fit on my new mid motor when the front motor's electronics "asymptotically fishtailed towards their consummation in the final conflagration" (a description of one of my novels by the late John Blackwell, editorial director at my then London literary publishers of record). I do believe though that the Surly stainless chainring will make tens of thousands of kilometres.

The choice of steel rings after the Surly was exactly one. First of all, the chainring  had to fit over the axle in the integrated bottom bracket by which the Bafang BBxx midmotor mounts into the bottom bracket shell. And, of course, the chainring had to be thin enough to fit the Chainglider, which eliminated the only custom-made chainring available, a thick ali job; presumably there are now more custom options, perhaps even including stainless steel, but I have enough suitable chainrings to see me out and I'm not embarrassed by a plain steel chainring, so I haven't been looking. After my good experience with the Amar plain steel, I had no hesitation in ordering all the Rohloff/Chainglider-capable and -approved tooth options for the Bafang motor with it. There wasn't a 38T option because it couldn't be made to fit the motor. On arrival and fitting and experimentation with the motor's torque curve in the software, after a while the 44T chainring stayed on the bike as the best match to the motor and to my requirements. It has given good service; even though I think expecting stainless steel-like longevity would be unreasonable, I am confident that these steel chainrings will prove to fit into my minimal service/maintenance concept, certainly far better than any aluminium chainring thin enough to fit into a Chainglider.

I keep a few tables of various transmission cog setups with a Rohloff at http://coolmainpress.com/BICYCLINGHebieChainglider.html





hendrich

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Re: cog change/chainglider
« Reply #5 on: August 12, 2024, 10:22:55 PM »
I've learned from this that I should be flipping/changing the cog sooner perhaps at 5000 mi intervals (rather than 10,000 mi). Like without the chainglider, excess oil tends to attract dirt, so good to wipe off chain after oiling. We were in rain on tour, the chainglider kept water off the chain and did not require oil. Whereas the timing chain required oil.

in4

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Re: cog change/chainglider
« Reply #6 on: August 13, 2024, 12:44:57 PM »
Have I been remiss in not flipping mine? I’ve done well over 10,000 kms. Same with my chain ring.

On another maintenance-related point: I’ve spent a bit of time greasing various bolts and nuts. All were easily movable if a little stiff. I reckon it’s a job worth doing as the last thing I want is to contend with a reluctant bolt whilst in the middle of nowhere whilst it’s pouring with rain. I used both copper grease and ‘ordinary’ stuff. Quick wipe down of any excess. Job done. 

hendrich

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Re: cog change/chainglider
« Reply #7 on: August 13, 2024, 03:21:54 PM »
Have I been remiss in not flipping mine? I’ve done well over 10,000 kms. Same with my chain ring.

For us on a heavily loaded tandem, 10,000 mi (16,000 kms) on a cog side is too much. Nothing bad happened, but transmission noise on tour is annoying because I was not sure of the source and I don't wish to break down in the middle of nowhere. My new opinion ... a cog change sooner is a very small price to pay to not have pestering noises on tour.

Regarding reluctant bolts ... agreed, many bolts (and other stuff) gets greased between tours. Perhaps not all each time. I am swimming in grease by the end of the cleaning. Perhaps this thread belongs under "Transmission".
« Last Edit: August 13, 2024, 03:23:49 PM by hendrich »