Hi, We have a 2006 Dawes Discovery Tandem, which we use as regularly as possible, and are very pleased with. The only problem is that the gear chain doesen’t last many miles, we have had the tandem from new and it was fitted with a KMC Z51 chain, and a Shimino HG30 cassette. but within 250 miles the chain was starting to jump, the chain is always kept well lubricated, I replaced the chain but the replacement started jumping even sooner, so then I replaced both the chain & cassette, which was fine until around the 300 mile mark, when the same problem occurred, we cover about 1500 miles per year so this becomes quite a costly exercise, by contrast the primary chain is still the original and has only ever needed slight adjustment to take up the slack. If anyone can offer any advice it would be much appreciated, or is it just the case Tandems are more demanding of the gear chain. I have tried a number of different makes of chain, but have always kept with Shimino Cassettes or be it higher quality ones.
I am no expert on these matters,but when you say “jump” do you mean that it doesn’t change gear properly at the rear and tries to “jump” either up or down the cassette ?
If so it could perhaps be the rear indexing wants adjusting slightly either up or down depending on what it’s doing.If the chain is trying to move to the next larger sprocket but can’t then turn the barrell adjuster at the rear about a quarter turn anti-clockwise ( from the rear ).If it won’t move down to a smaller sprocket then turn the barrell adjuster a quarter turn clockwise ( from the rear ).
I can’t see it being a chain problem at 300 miles or so.We don’t do anywhere near your mileage but have never had a problem in round about 1000 miles,we also use a Shimano cassette but with a Sram chain but I imagine a Shimano chain shouldn’t be a problem.Why it should be OK for a couple of hundred miles or so I don’t know,unless you have some cable movement somewhere.
If however you mean “jump” in the sense that the pedals suddenly slip forward it could be a problematic freewheel that is slipping.I don’t think these can be repaired but I could be wrong.
Apologies if this is “teaching your grandmother to suck eggs”,but when you say you replaced the chain and cassette you don’t say whether you did it yourself or a shop did it,you may well be an expert mechanic.
If the above doesn’t help may i suggest a trip to the Tandem Club site ( http://www.tandem-club.org.uk/ ) where I am sure someone who knows a lot more than me will be able to assist.You don’t have to join to use the Discussion Board,but it’s only £10 per couple per year if you do.
Hi, Many thanks for your help and advice, maybe I didn’t explain very well, by “Jump” I meant the chain is skipping over the cog, I can assure you the indexing is working fine. when it begins it is usually only on the smallest chain ring, and smallest rear cassette cog, (which I know as 8th gear). as soon as you begin to climb up the cassette the skipping will go, no matter how much pedal pressure is applied, which I assume means the freewheel is ok. As I said before I usually end up changing the chain around the 300 to 400 miles to try and make the cassette last longer.
I have always done my own maintenance over the years, (with the exception of wheel straighting) buying any specialist tools needed along the way. so I feel fairly confident that the tandem is well set up.
The only thing that springs to mind from your description is the fact that when the jumping is at its worst the chain is at its most acute angle ( small cog to small ring ).There is a thread on the CTC forum at the minute posted by someone who is having much the same problem as you except his chains are wearing rapidly on a solo.
One of the suggestions in this thread ( and there are quite a few ) is that using this combination ( small to small ) frequently, accelerates chain wear considerably which leads to jumping..
Sorry I can’t be of more assistance but as I said in my original post someone on the Tandem Club ( or CTC ) forums will surely be able to help.
Hi Ian, Thanks again for your help, I did check the link you gave me, and after reading the sugestions have come to the conclusion that it is not a good idea to to use that combination of gears to often due to the chain tension, and angle etc. in future I will try to minimise that combination and see if the milage improves.
I have also been told that despite keeping the chain well lubricated, the fact that 50% of our milage is on off road cycle tracks grit and dirt may also be adding to the problem, so I am also going to buy a good chain cleaner.
Ian is correct and has given you some really good advice. There could be other causes, bent rear hanger? Damaged tooth on one of the chain rings? Do you have a good bike shop to double check some of these things?
MTBing on a tandem is always going to put it under duress, but after 300 or so miles things should be bedding in, not wearing out.
Hi Ruth, Many thanks for you advice also I think prehaps it would be better to have the gears checked over by a good cycle shop. We have a good tandem dealer within 20 miles of us so will get them to check it out.
Peter
