1sp conversion - chain skips

[kgreene10]

I converted a vertical dropout road frame using a Surly cog, an old 7800 RD, a 9sp chain, and a 42T FSA chainring on a SRAM 2x 130bcd crank. It works fine except under heavy load. If I’m really pushing it to get up a steeper hill, the chain skips.

What’s the most likely culprit? Need more chain tension, need a narrow-wide chainring, keep fiddling with chainline?

[dustyrider]

I’ve had better luck flipping the spring around and having the chain tensioner push up instead of down with the surly tensioner. I also preferred an 8sp chain over 9sp. I’m not sure those things will help with your specific issue, but good luck!
Reread: I have no clue about the 7800 rear derailleur...

[Louis]

How many miles on the chain vs the cog? Both new?

[kgreene10]

Originally Posted by Louis

How many miles on the chain vs the cog? Both new?

Yes, both new.

I suppose I could take out more chain links to make it more taut. Might that help?

[tigoat]

Is this a single speed conversion with a multi speed RD? That Shimano RD might be the problem. There might be too much chain slag. Also with a single speed setup, the chain-ring teeth must be straight to lock the chain in place.

[p nut]

How did you center the RD over the cog? Pictures?

I’m betting it’s the chain line. How did you figure the chain line?

https://forums.mtbr.com/singlespeed/...th-738755.html

[kgreene10]

Originally Posted by tigoat

Is this a single speed conversion with a multi speed RD? That Shimano RD might be the problem. There might be too much chain slag. Also with a single speed setup, the chain-ring teeth must be straight to lock the chain in place.

That’s correct. So a dedicated chain tensioner would be the ticket?

[benb]

Probably a better chain tensioner is the answer.

Single speed bikes have absolutely no need for things like narrow-wide chainrings.

Make sure you get this locked down.. if it's skipping on the cog there is a pretty nasty failure condition where the chain skips off the cog and wraps around the hub locking the rear wheel up. If it skips off the chainring it's likely to do it when you're out of the saddle and you crash down to the bottom of the pedal stroke.. might or might not make you crash, even if you don't crash it's easy to jam a knee or ankle when it happens.

If either happens on a downhill as Jeremy Clarkson or Richard Hammond might say, "A little poop will come out".

[kgreene10]

Thanks for the link. Sensible math!

Originally Posted by p nut

How did you center the RD over the cog? Pictures?

I’m betting it’s the chain line. How did you figure the chain line?

https://forums.mtbr.com/singlespeed/...th-738755.html

[kgreene10]

Most votes so far for “get a better chain tensioner” and “make the chainline straight”. On the former, can I go cheap with Shimano Afine ($15) or do I need the Surly or similar ($50)?

[oldpotatoe]

Originally Posted by kgreene10

Most votes so far for “get a better chain tensioner” and “make the chainline straight”. On the former, can I go cheap with Shimano Afine ($15) or do I need the Surly or similar ($50)?

Alfine works really well..I have sold a bunch of them..BUT chainline....

[p nut]

Originally Posted by kgreene10

Most votes so far for “get a better chain tensioner” and “make the chainline straight”. On the former, can I go cheap with Shimano Afine ($15) or do I need the Surly or similar ($50)?

I really don't think you need a tensioner. Derailers work just fine. You just need to get it centered right and make sure chainline is dialed in.

I'm just curious how you centered the RD. Either a long B screw or I would just use a little piece of cable to get it in the vicinity and fine tune it with the barrel adjuster.

[fmradio516]

+1 for above. I think the derailleur will work better than a tensioner. I know when I had a tensioner bike, it was SO noisy.

[tigoat]

Originally Posted by kgreene10

Most votes so far for “get a better chain tensioner” and “make the chainline straight”. On the former, can I go cheap with Shimano Afine ($15) or do I need the Surly or similar ($50)?

It depends on your chainstay length and the single speed gear ratio/chain length, you might be able to not use any tensioner at all. All of my single speed bikes do not have a tensioner, the chain is tensioned naturally by matching the chainstay and the chain length with a gear ratio that works for me.

[Mark McM]

Originally Posted by tigoat

It depends on your chainstay length and the single speed gear ratio/chain length, you might be able to not use any tensioner at all. All of my single speed bikes do not have a tensioner, the chain is tensioned naturally by matching the chainstay and the chain length with a gear ratio that works for me.

This is why they make half-links - they allow you to fine tune the chain length even further.