Converted SS - chain or freehub skipping - help please

[Watchman]

I took an old mid-90s alloy MTB frame and forks and converted it to a single-speed but I can't stop it from "skipping" when I'm pedalling.

Now, I'm quite a spanner-friendly person but I can't work out what I'm doing wrong. The bits I'm working with are:

1. Shimano freehub on a 26" wheel - from the original bike
2. New Shimano crank arms and a new Velosolo single speed chainring
3. New steel sprocket
4. A new spring-loaded tensioner
5. A new KMC 6/7/8 speed chain

I've tried the chainring on both the outside and inside of the crank arm spider, and the sprocket along the length of the freehub, all to no avail. I am considering that the skipping may be nothing to do with position (that I have it right). My thoughts are turning to things I can't easily tell/measure, such as:

1. Could it be the derailleur hanger out of alignment? When the bike had the original sprocket "pack" it didn't skip like this.
2. Could the tensioner be too weak? The spring feels similar to that from the original derailleur.
3. Could the tensioner be positioned such that the chain isn't wrapped around enough of the sprocket? Picture below.
4. Could the freehub be skipping? It didn't used to but I haven't had it apart to service it.

I'm rather stuck. I'd prefer to sort this myself but I am running out of ideas. I favour simple solutions like the chain alignment but I'm working up to thinking it might be the freehub skipping. Before I pull it apart, I thought I'd seek advice which will be gratefully received.

[Watchman]

Maybe worth noting, I can't replicate this when the bike's on the bench. My arms aren't strong enough to cause the skipping. And I can't see what's happening when I'm riding it.

Might also be worth noting, the bike had been stored outside for at least 2 years without any cover. I've junked everything that was steel on the bike, and have regreased the hubs (which were fine anyway). I have not looked at the freehub at all but I concede that it could be kernackered. It just didn't display this skipping when I rode it before I stripped it, and the major change was turning it into a SS.

[Mark Wibble]

Personally I'd put money on 4). My own SS is just starting to do the same.

3 is possible, there's a lot of slack there.
2 is possible, especially if it's combined with 3.

I would say it's not 1 as poor alignment will most likely cause the chain to fall off, not skip. However, it can create a sensation and sound not unlike skipping when the chain tries to engage with a bit of metal it shouldn't and then pops into its proper location.

5. One other thing is you're using a wide chain- if the link gaps are wide compared with the cog teeth, the chain is free to move sideways which can cause issues which may feel like skipping at times.

However, always start off with the cheapest and easiest things you can check or fix, so my advice would be...

A) Get a good alignment first regardless- even though it's almost certainly not the problem here, it'll help prevent future mechanicals!
B) Are you sure you can't take another link out, as there's an awful lot of slack, it helps a lot if the chain is as short as it can be. It also reduces the effects of your possible causes 2 & 3.

Try them first as they're free, if it still happens then...

C) Fit a new freehub, assuming it's by far the oldest part, it'll need doing soon anyway.
D) Fit a narrower chain, providing it's still compatible with both cogs.

If it still happens, it's related to chain tension and wrap.

E) If you have a spare rear mech lying around you could test this out (if the chain will fit through the cage). If that fixes it then a permanent solution is a double-pulley tensioner (looks like a simple rear mech without a cable)

F) Try a different ring/cog setup- if you add a single tooth front or rear it'll have the same effect as removing half a chain link, but won't change the ratio much. So if you haven't been able to remove a full link, it'll help with tensioning.

Z) You could have a look to see if you can install a half-link in place of a full-link. However IMHO they're more hassle than they're worth, and it'll become the weak point of the chain.

Hope that helps...

Mark

[Mark Wibble]

Just read your minor update- I'd put even more money on it being the freehub!

Riding singlespeed puts more tension on the chain, unless you rode everywhere out of the saddle and in top gear anyway, so if your freehub is on the way out it'll show it when you switch to SS...

I find SSers need a bit more effort to get set up right, then they're great!

Also, I found converting a geared frame was great to get me into it, but I fairly soon switched to a true SS frame.

[donfisher]

I’m not sure if this will be any help or if it just highlights an issue with my own bike but…

A couple of times I’ve adjusted the RD to get it to index properly again, nothing special, just via the barrel adjusters. This has happened when I’ve done it while the bike was up on the stand. I’ve set it so it goes up and down the cassette perfectly. I’ve then found that it will require another .25 or .5 turn on the barrel adjuster when I come to use the bike normally on the road.

If you set the tensioner up while on the stand, maybe when the tensioner is actually being used under normal load it’s slightly out and trying to move the chain up/down?

[Watchman]

Mark Wibble said:

Personally I'd put money on 4). My own SS is just starting to do the same.

Thanks Mark. The bike hasn't had much use but it has stood outside in all weathers for 2+ years.

Mark Wibble said:

3 is possible, there's a lot of slack there.
2 is possible, especially if it's combined with 3.

With reference to your advice about shortening the chain below, I'll give that a go, although I *think* I already have as short as poss.

Mark Wibble said:

I would say it's not 1 as poor alignment will most likely cause the chain to fall off, not skip. However, it can create a sensation and sound not unlike skipping when the chain tries to engage with a bit of metal it shouldn't and then pops into its proper location.

Yes, like when a chain isn't quite sitting right on a derailleur pack. It's not like that here. It sounds like it's engaging well (no grinding) but then every time I press on the pedals, it jumps.

Mark Wibble said:

5. One other thing is you're using a wide chain- if the link gaps are wide compared with the cog teeth, the chain is free to move sideways which can cause issues which may feel like skipping at times.

I bought this lot a while back but I bought the sprocket first and discovered it requires this type of chain, which subsequently drove me to look at single speed chainrings because they are usually happy with wider chains too.

Mark Wibble said:

However, always start off with the cheapest and easiest things you can check or fix, so my advice would be...

A) Get a good alignment first regardless- even though it's almost certainly not the problem here, it'll help prevent future mechanicals!

In light of there being other suspects in this, I am now more confident with my alignment. Thanks.

Mark Wibble said:

B) Are you sure you can't take another link out, as there's an awful lot of slack, it helps a lot if the chain is as short as it can be. It also reduces the effects of your possible causes 2 & 3.

Yes, I totally agree. I will look at this again.

Mark Wibble said:

Try them first as they're free, if it still happens then...

C) Fit a new freehub, assuming it's by far the oldest part, it'll need doing soon anyway.
D) Fit a narrower chain, providing it's still compatible with both cogs.

If it still happens, it's related to chain tension and wrap.

Agreed.

Mark Wibble said:

E) If you have a spare rear mech lying around you could test this out (if the chain will fit through the cage). If that fixes it then a permanent solution is a double-pulley tensioner (looks like a simple rear mech without a cable)

Yes, I can see how that would improve the "wrap".

Mark Wibble said:

F) Try a different ring/cog setup- if you add a single tooth front or rear it'll have the same effect as removing half a chain link, but won't change the ratio much. So if you haven't been able to remove a full link, it'll help with tensioning.

I think I can lay my hands on a 20T sprocket instead of the 18T I've got now. I've deliberately built it "slow" so I can encourage other people to come riding with us.

Mark Wibble said:

Z) You could have a look to see if you can install a half-link in place of a full-link. However IMHO they're more hassle than they're worth, and it'll become the weak point of the chain.

Hope that helps...

Mark

It really does help. Very many thanks for that.

[Watchman]

donfisher said:

I’m not sure if this will be any help or if it just highlights an issue with my own bike but…

A couple of times I’ve adjusted the RD to get it to index properly again, nothing special, just via the barrel adjusters. This has happened when I’ve done it while the bike was up on the stand. I’ve set it so it goes up and down the cassette perfectly. I’ve then found that it will require another .25 or .5 turn on the barrel adjuster when I come to use the bike normally on the road.

If you set the tensioner up while on the stand, maybe when the tensioner is actually being used under normal load it’s slightly out and trying to move the chain up/down?

I understand exactly what you mean here, and agree with you about how the derailleur's position changes between the stand and the road. In this instance though I am not getting the sound you get when you're slightly out of index-alignment - that grinding/ticking noise. I'm literally getting a *jump* as if the chain has skipped. I'll look at chain-wrap around the sprocket but I'm now more inclined to believe the freehub is at fault because, even with limited wrap, it doesn't take much effort to cause the jump AND the sprocket does have quite tall teeth (being a SS sprocket).

[Watchman]

Mark Wibble said:

Just read your minor update- I'd put even more money on it being the freehub!

Yeah, I'm definitely working up to stripping it. I'll try fixing it but a new one isn't terribly expensive. I like repairing rather than replacing where possible. It's fun.

Mark Wibble said:

Also, I found converting a geared frame was great to get me into it, but I fairly soon switched to a true SS frame.

Oh I am desperate to buy one of these... but it costs more than my old car :

[Fourmotion]

99 times of out 100 it is because there is too much slack in the chain. You won't be able to see it, but it will be skipping about and under tension it can slip quite easily.

I'd suggest taking out as many links as possible, and have that tensioner set pretty taut. Don't spend any money on the freehub until you have tried that.

I eventually gave up peeing about with a tensioner and just ran it tight, and then I swapped to a SS frame with slot dropouts. It made a world of difference.

[gazza285]

Watchman said:

h I am desperate to buy one of these... but it costs more than my old car :

Nice. My mate has an orange one, it weighs nothing.

[Watchman]

Shortened the chain and THAT DID IT..!!

Brilliant. Can't thank you all enough. Despite this bike being several hundred £££ cheaper than my normal bikes, I love it... partly because I built it, and partly because it's so quiet without the chain slapping.

I'm definitely a convert. Might even try a hub gear next.

[uncinquesei]

Apologies if I've missed it, but what is the gearing on that? I'm assuming from the road tyres it'll be used for commuting or similar. I ride a converted s/s road bike with 700c wheels on a 48:18 and would like an alternative using my old marin nail trail.

[Justin S]

Damn too late. Chain is too long LOL. I had the same problem with mine last week, when I built it. Sounded like a gattling gun riding it to work.

[Watchman]

uncinquesei said:

Apologies if I've missed it, but what is the gearing on that? I'm assuming from the road tyres it'll be used for commuting or similar. I ride a converted s/s road bike with 700c wheels on a 48:18 and would like an alternative using my old marin nail trail.

Oh it's geared really slow. I built it because I often get people telling me they'd love to come cycling with me (and the group we go in - a family bunch - typical circuit ~10 - 15 miles) but they don't have a bike. As I tow a TagAlong and sometimes even a trailer on the back of that, you can imagine I don't set any speed records, so rather than make the single speed hard work for the lendee (is that even a word?), I geared it low. Still, it rolls lovely. and you can get it up to wind-in-the-hair speeds with some exuberant pedalling.

It's something like 32/18 on 26" wheels. As I said, sloooow.