Bike keeps shifting by itself!

cougie

I really don't think you've tried much if you say you can't ride it 100 yards. How many gears does it shift ? Is it constantly up and down in this 100 yards ?

As I've said before sometimes a new chain does need to bed in if the block is slightly worn.

bungle73

@apreading Yes.

@Cougle I can't work out if you're trying to have laugh or what? What are you on about I haven't "tried"? Yes I have! The bike is unridable. Not only that it is DANGEROUS to boot.

I'm not sure why you want me to ruin a perfectly good chain by forcing it to work with manky old worn cassette, and at the same time cause me annoyance and risk, when I could just as easily wait for the brand new cassette to come which I have already ordered!

mamba80

I read about this idea of riding until the new chain beds into the part worn cassette and i did once try it, all that happened was i ruined a good chain, which wore out very quickly, as it wore unevenly and never quite shifted well across the cassette.
if the cassette is worn that a new chain skips about, swap out the cassette too and change the chain more frequently or run the drive chain into the ground!

cougie

Well it's worked for me in the past. I just can't understand how a block has worn so much in just 1000 miles. I get loads more than that from mine.

bungle73

Neither do I, but that seems to be the way that it is. I did ride through some pretty crappy conditions over the winter though.

Actually it's a little more than that as I'm going by what it says on Garmin Connect, and I bought the Garmin in the July, but the bike in June.

apreading

Can I just check - how did you know the old chain needed changing?

Chains should last more than 1000 miles too. But abuse can wear the whole drivetrain much quicker. I dont necessarily mean abuse as in you treating it badly - you head about one ride wearing out drivetrains and brakes at Swinley Forest when its wet because of all the grit that gets in it.

If you rode through crappy conditions in the winter, in paricularly on salted roads, and then didnt clean the drivetrain then everything will wear more quickly and if this is why the chain is gone already then it sounds like it did for the cassette too. Worst case, it may have worn your front chainrings too.

bungle73

apreading wrote:

Can I just check - how did you know the old chain needed changing?

Chains should last more than 1000 miles too. But abuse can wear the whole drivetrain much quicker. I dont necessarily mean abuse as in you treating it badly - you head about one ride wearing out drivetrains and brakes at Swinley Forest when its wet because of all the grit that gets in it.

If you rode through crappy conditions in the winter, in paricularly on salted roads, and then didnt clean the drivetrain then everything will wear more quickly and if this is why the chain is gone already then it sounds like it did for the cassette too. Worst case, it may have worn your front chainrings too.

With a chain checker.

When the bike is getting covered in crap every single ride, and particularly when I've been out for twice as long as expected because I was having to deal with weekly punctures, it was hard to keep on top of it; but I cleaned it now and then. Besides it didn't seem to affect the MTB the previous winter so I didn't think too much about it.

apreading

How stretched did the chain checker say the old one was?

redvision

Bungle73 wrote:

With a chain checker.

When the bike is getting covered in crap every single ride, and particularly when I've been out for twice as long as expected because I was having to deal with weekly punctures, it was hard to keep on top of it; but I cleaned it now and then.

You only have to wipe the chain with a rag after a ride in bad conditions and it will prolong the life of it.
Literally takes a couple of seconds.
Suggest you start doing this.

Reading through this thread, I would suggest getting your bike you the lbs for a service. Sounds like it needs it and they will give you maintenance tips and advice.

bungle73

apreading wrote:

How stretched did the chain checker say the old one was?

When I checked a few months ago it was fine, then I checked it fairly recently and it had gone to 0.75%, so I thought I'd better think about replacement, but didn't have the money to do right away. Then I checked it week or two ago and it had suddenly jumped to 1%, so I thought I'd better replace it right away

bungle73

redvision wrote:

Bungle73 wrote:

With a chain checker.

When the bike is getting covered in crap every single ride, and particularly when I've been out for twice as long as expected because I was having to deal with weekly punctures, it was hard to keep on top of it; but I cleaned it now and then.

You only have to wipe the chain with a rag after a ride in bad conditions and it will prolong the life of it.
Literally takes a couple of seconds.
Suggest you start doing this.

Reading through this thread, I would suggest getting your bike you the lbs for a service. Sounds like it needs it and they will give you maintenance tips and advice.

As I said, I don't have a lbs. And I don't think I need to as I know how to do most things myself. And what I don't know I find out. The only things I don't touch are the wheels as that is too much of a dark art, but they're fine atm.

apreading

If you see that much stretch then guarantee the cassette will need doing.

This is the problem - your 'economy' ultimately ended up costing you more money. If you had changed the chain back then your cassette wouldnt have needed doing until the next chain wore out - it might even have lasted longer than that, especially if you had done it at 0.5%.

If you get 1% then dont even think about keeping the cassette IMO. You might even find your chainrings are worn although they are generally a bit more hardy - I wouldnt be hugely surprised if there is a problem there too.

bungle73

Well is it normal for a chain to suddenly start wearing that fast? I certainly didn't expect it to. I'm talking what must be probably less than a month ago that it was at 0.75%, and when I checked in the spring it was fine then.

And when I changed the chain on my MTB which was also extremely worn (it had been on there since I bought it, but it hadn't been used for a long time), I just slapped a new chain on there and I was good to go.

apreading

Yeah - but as said above, your chain probably wore more quickly because it was working on a worn cassette. Always change at 0.75% 0.5 might be a bit overkill but some people do it then and it is certainly a sign to keep checking more regularly.

Something was happening - you must have had grit in the rollers of the chain and/or not been cleaning and lubing it so it was wearing quickly. Generally I get 3000 miles or so from a chain and I am not over the top but if I ever hear it needing maintenance I give it a 'thorough' clean to get any grinding paste or grit out.

bungle73

apreading wrote:

Yeah - but as said above, your chain probably wore more quickly because it was working on a worn cassette. Always change at 0.75% 0.5 might be a bit overkill but some people do it then and it is certainly a sign to keep checking more regularly.

Something was happening - you must have had grit in the rollers of the chain and/or not been cleaning and lubing it so it was wearing quickly. Generally I get 3000 miles or so from a chain and I am not over the top but if I ever hear it needing maintenance I give it a 'thorough' clean to get any grinding paste or grit out.

My checker doesn't show 0.5% though, only 0.75% and 1%, and according to the instructions that came with it 0.75% only means the chain needs replacing "soon", so I didn't think it was that urgent.

And I thought it was the chain that wears the cassette and not the other way around?

apreading

If the links in the chain are at different spacing to the cogs on the cassette/chainring then both surfaces will be under greater tension than normal and both will wear each other. Hence why some poster above talked about 'breaking in the chain' and the discrepancy going away after a while - well YES because you have stretched the new chain very quickly!

My park tools chain checker ONLY does 0.5 and 0.75 - it doesnt measure any further than that as you are entering risky territory at that point.

bungle73

I see. Thanks. I got mine from Halfords.

svetty

Veronese68 wrote:

Bungle73 wrote:

I've a box of tools, yes. But I've never needed the ones necessary for removing a cassette.

You will need a cassette tool and a chain whip. Rather than a conventional chain whip the tool from Decathlon gets very good reviews, that would seem to be the way to go. I don't have one as I have a chain whip I've had for about 30 years, but I will be getting one. This is what you want:

It's probably a cool tool but my concern would be that it's only using 3 teeth on the sprockets to resist the turning moment. If the cassette is tightly torqued up as it should be, it might require a fair bit of force to undo it - a chain-whip spreads this load over more teeth.