Slack track chains

[Wendy]

Interesting to see the slackness of the chains on the world champs - too tight obv. isn't so good for efficiency.

[rogerzilla]

Keirin riders run pretty slack chains too.  Of course, trackies ride short distances (except the six-day lot) and also don't have to worry about road rash or that dirty great Hanson aggregates lorry behind them.

[Chris S]

No going downhill where their chains might be alternating between taught at the top and taught at the bottom (encourages derailment).

Besides - they are Hardcore cyclists who only ever keep their chains Taught at the Top; how much they dangle doesn't matter much.

[Wendy]

Yes, I already understand why.  It's just interesting how slackness equates to better efficiency.

[andygates]

Well, tightness and grobble are all energy saps.   

[Frenchie]

In my club, the best fixed TT riders also run a slightly slack chain.

[rogerzilla]

Yes, I already understand why.  It's just interesting how slackness equates to better efficiency.

The last test I saw suggested it doesn't; a tight chain is better, presumably because energy is lost in the extra movement of the links when it's slack.

There is certainly more frictional loss in a tight chain if you spin the cranks with the bike upside-down, but that's not necessarily a good test; during riding there's (hopefully) constant power going in and the top run is always tight as a drum.

[border-rider]

With good quality stuff it's possible to have a reasonably tight chain and no binding.

[токамак]

When I was buying parts for my fixed wheel bike at JD Whiskers the guys there (probably the most experienced bike techies I know of) advised me it wasn't necessary to have a really taught chain. I'm wondering if the reason has something to do with high tension chains being more likely to pull the rear wheel forward or out of line. I personally do like to have the chain quite tight - a bit of up and down movement but no sag, it saddens me to see a drooping chain on a fixed wheel! Actually I was on an audax a few weeks ago and a guy went past me on a track bike - I noticed his chain was quite slack and whilst I was riding along side the chain actually jumped off and locked up his wheel - big skid.

[border-rider]

Mmmm

I think a tight(ish) chain is far more important on audax than on the track.  What makes it jump is crazy cadences and bumps.  Not usually a problem on the track

[токамак]

I totally agree - when I'm out and I can feel that the wheel has crept forward and the chain is getting slack it makes me really nervous!

[simonali]

They interviewed Chris Boardman about the bikes and he emphasised how the bikes are tweaked and tested to the teeniest margins, so maybe a taut chain isn't the most efficient?

[bobb]

Yeah, from what Chris was saying - they leave no stone unturned when it comes to getting the most out of the bikes. I would imagine they've tested and tested and tested to find the optimum amount of slackness for the chains

[hubner]

Or maybe it doesn't make any difference, it's just easier and quicker to fit the wheel so that the chain's bit slack.

When you're pedalling, does it really make any difference in efficiency if the bottom of the chain is tightish with no droop, slightly slack, a bit slack, or quite slack but not enough for the chain to come off? It's the top half that transmit force from the ring to the sprocket.

[Wendy]

The last test I saw suggested it doesn't; a tight chain is better, presumably because energy is lost in the extra movement of the links when it's slack.

There is certainly more frictional loss in a tight chain if you spin the cranks with the bike upside-down, but that's not necessarily a good test; during riding there's (hopefully) constant power going in and the top run is always tight as a drum.

If that were true, then you can be certain the chains would all be tight, and they aren't. 

[PeterM]

when I'm out and I can feel that the wheel has crept forward and the chain is getting slack it makes me really nervous!

Yes indeed.  The sudden appearance of slop in a taut drivetrain is very disconcerting.

[Ian H]

Dedicated track bikes with eighth chain, sprockets, and rings will be far less prone to unshipping than anything running a 3/32nd chain, which is designed to run easily off a sprocket. Larger sprockets and rings will also make it more secure.