Time to change my chain on my bike – T-130 – but I reckon the existing chain might be too long, completely based on how the mech looks in the gears. New chain so an opportunity to remove a few links, but what is the best way to work out the minimum + 2 links length? Actually would be minimum + 4 links as I’m not wanting it so short that there is a risk of something snapping.

Thanks.

Deflate shock and compress to full amount. Wrap chain around front ring, rear biggest cog and through the mech.

I usually push the mech to what looks about right then check the chain length.

I did consider that then wondered if that would be the longest stretch needed…I’ve no idea what ‘path’ the suspension movement makes…however, as someone else has suggested that then I’ll go with it.

Look at No.5

https://www.parktool.com/blog/repair-help/chain-length-sizing#article-section-5

“Deflate shock and compress to full amount”

Full compression isn’t necessarily the longest point though. Usually is, but it’s worth sweeping it through the range while you’re at it. You don’t need to know the longest point, you just need to know that it works OK.

Honestly OP there are rules of thumb and other bodges but it’s so easy to just check it on the bike and that’s 100% accurate and foolproof so I’ve no clue why anyone would do anything else.

Editing my moan as I’ve now read that Park page and I’m lost! I think it suggest putting the chain round the biggest rear cog and the largest front ring without threading the chain through the mech…so I’m assuming you then get the chain to be as straight as possible and then add in an extra 2 full links, then thread it through the mech and join the chain – is that right?

This used to be so much easier when it was all just hardtails!

I’d personally take the same number of links to start from, unless you’ve noticed problems shifting or losing the chain. It’s possible that chain ‘stretch’ due to wear has made it look slightly slacker than it was when originally fitted.

Editing my moan as I’ve now read that Park page and I’m lost! I think it suggest putting the chain round the biggest rear cog and the largest front ring without threading the chain through the mech…so I’m assuming you then get the chain to be as straight as possible and then add in an extra 2 full links, then thread it through the mech and join the chain – is that right?

That would be the method for a HT, you may need more links for a FS.

When you say the mech looks wrong to you, are you looking at it off the bike? When you’re sitting on it and the rear suspension sags, in most cases the mech will move slightly forward.

This is pretty obvious, but if in doubt, make it longer. I bought a used bike with a chain that was fractionally too short – it was fine until one day I cross shifted big-big while bottoming out the suspension and it pulled the rear mech into the wheel and destroyed both 🙁

Lessons were learned that day, especially about trusting bikes built by someone else (even if they were Hope themselves!)

Interesting issue. And see where the potential risk is…

Possible that I use the wrong method – but I do like this (2×10 Deore, 130/130 bike and 150/150 bike):

chain on smallest chain ring front (24T) and smallest (11T) rear cog.

And then I shorten the chain in such a way that there is “some free space” between rear mech / jockey wheels and chain (rear mech not touching the “free chain”).

And then…- chain on biggest chain ring front (34T) and biggest (42T) rear cog. And in this position I push the rear mech/ jockey wheels by hand a bit to the front to check if there is enough spring/clearance for chain movement. There is always plenty clearance…- means I don’t do any suspension compression check or so.

Means: maybe I don’t bike the shortest chain possible. But with the “clutch” there is nearly no chain slapping any more – or?

Do you have problems with the “long chain”. Do I maybe run into problems with it …? “Short” chain is more risky – or?

then add in an extra 2 full links, then thread it through the mech and join the chain – is that right?

This used to be so much easier when it was all just hardtails!

I’m pretty sure that rule of thumb predates its use on FS bikes.  The only difference is that you apply it with the suspension compressed on a FS bike.  All it does is make sure that when the chain is taking its longest possible path (biggest chainring, biggest sprocket, and on FS, max extension) you’ve still got a reasonable amount of slack for the derailleur to sit “comfortably”.

BTW the article says you add 2 rivets ( = 1 full link ) unless it’s SRAM 1x on a hardtail.

I’m with andreasrhoen on this.

I start small/small then do big/big and then test if fs bike. Doing  this way means the chain is always a bit long to start. You can always remove links after to fine tune. You can’t put them back in.

<span>Always done all my bikes big-big +2 through the Mechs, no issues.  Sheldon Brown says: https://www.sheldonbrown.com/derailer-adjustment.html#chain</span>

When I did the chains our bikes, I got the wife, with a fabric tape measure, to measure between the bottom bracket and rear axle as I compressed the suspension. As it compressed, it pulled a bit of the tape through her fingers. This then allowed us to figure out the maximum chain stay length.

I then used to park tool simple equation.

Some common sense needs to be applied though. For example, on a 3×9, there’s a good chance you could go big/big and full compression. However, on a 1×11, that’s less likely as it’s the slowly winching up steep stuff gear.

Some common sense needs to be applied though. For example, on a 3×9, there’s a good chance you could go big/big and full compression. However, on a 1×11, that’s less likely as it’s the slowly winching up steep stuff gear.

I would be really careful here and it would be a braver person than me that would intentionally fit a chain that was too short for a specific combination of gears / suspension travel. It’s surprising how much an unlocked bike can bob under climbing, so I would certainly be ensuring that there is adequate chain length for full suspension travel when in the largest rear sprocket. Anything else and you’ll end up needing a new mech / hanger / wheel before you know it…

This looks a useful sort of thing:
http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html

(Implementation of the calculations from Park’s website)

I’m not suggesting anyone run with a short chain but if max chain stay length is at max travel, while the severity is the same, the likelihood is less.