Ok, you know i know how long a chain should be but I figured i'd show you the very simple 'miamijim' way of determining chain length.

This thread came about due to a very unfortunate and somewhat emabarassing transaction I had with fellow C&V member. The bike I sent him had a too short chain....my mistake for not catching it.

What I do is make my chains as long as possible. Longer chains put less stress and strain on the drivetrain and they last longer because wear is distributed amongst a greater number of links.

1. Shift into the small/small combo
2. Remove just enough links so that the rear most pully is below the front most pulley and so that there's an air gap between the chain and pullry cage/derailleur body..

If, after doing this you cant shift into the big/big combo something is wrong with your setup. Either you need a longer cage derailleur or you have an ultra wide gear combo like a 54/38 with an 11/34 freewheel.

Whats interesting about the pics below is that its the same chain!!! Pic 1 is 'new' and pic 2 'stretched'.

I usually start with it just long enough for the big/big combo, even though I wouldn't ride there.

WITHOUT routing it through the rear derailleur, I route the chain over the big-big gear combo, and add two links.
Then I route through the DR and secure the chain.
(Works for me.)

If you mean two half links, that's exactly the way I do it and it always works perfectly for me. Why make it more complicated than that?

Sheldon advocated using the same method:

"The best technique for setting chain length is to thread the chain onto the large/large combination, without running it through the rear derailer. Mesh the two ends on to the large chainwheel so that one complete link (one inch, -- one inner and one outer half-link) overlaps. In almost all cases, this will give the optimum length."

+1 on the large/large plus two half-links--works just fine for me every time.

agreed.

ive used this on road doubles, compact setups, triples, and 1x9 mtb setups.

Miamijim,
I like the idea of slower chain and drivetrain wear. I would consider this method if it is truly different than the big/big w/links method.
When you set up with the small/small; what do you end up with when you take that same chain and wrap the big/big? Is it more/same/less than the big/big?

I've used Jim's method since day #1. Always works like a charm, though some RDs - such as the Campag NR - might require the pulley to sit a bit lower than shown here for a dropped parallelogram RD.

-Kurt

I was taught both methods, big-big no RD/small-small through RD back in the mid '60s. Either works fine, but I prefer the small-small procedure for no reason other than habit.

Brad

I've always used Sheldon's method. It has severed me well 100% of the time.

I used sheldon's method with a mountech rd and it came out too short. never was quite sure why.

I think it may have something to do with that extra pulley.

I set up a bike with a Mountech RD two weeks ago using Sheldon's method. It had a super long cage, but only two pulleys. I know the Suntour XC RDs have three pulleys, but I didn't know there was a three pulley Mountech.

I must have been thinking of LePree.

https://velobase.com/ViewComponent.as...=108&AbsPos=37

No, I think you were basically correct. I think the XC is the second generation of the Mountech derailleurs, but I don't think it was labeled "Mountech". I think you're right in that the reason Sheldon's method didn't work with the Mountech is because of that RD's atypical design (really long cage).

yeah it was 2 pulley. i had a thread w/pics asking for help. adding chain solved the issue.

https://www.bikeforums.net/showthread...ion&highlight=

I use the small/small method because it was the quickest and easiest method when I was working in a busy shop. The big/big method works on the asumption you have the proper RD while the small/small method takes into account the RD cage length.

To be honest, I never took a small/small sized chain and compared it to a big/big sized chain. The advantage of the small/small method is that your chain is always at its longest length thus there's no need to make it shorter. A disadvantage of the big/big method is that you can have chain sag or rub on the RD when in the small/small combo but as i mentioned earlier, if you run into either of those issues your setup is off. Either you need a longer cage RD or you have a very extreme drivetrian setup i.e. a 53/3X/24 triple with an 11/34 cassette/freewheel.

Refer to this pic for proper RD angle:

I had a chain sag issue the other night on the small-small after setting up the chain using the big-big method. The upper pulley was also hitting the big cog. That's when I discovered that you have to set the upper spring tension when you mount a Simplex SX610 on a claw. There's no way to do that when you mount one on an integral hanger. The tension is preset and non-adjustable. I suppose the same holds true for a lot of Simplex derailers.