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I'm getting close to being finished with my Trek 520 frame-up build (with custom drivetrain). The only thing that remains is cabling the front and rear derailleurs, setting the limit screws and indexing properly and installing the shift levers. The derailleurs themselves are installed already.

For this bike I have a triple in the front, 9 speed in the back. Indexed rear and friction front bar-end shifters.

What order makes the most sense to set these up, given that this is a brand new system with neither front nor rear derailleurs set up yet?

I've had success following the Park tool videos on derailleur adjustment in the past (on other bikes) but these require you to shift the front in order to adjust the rear and to shift the rear in order to adjust the front. So there is a catch-22 if neither of them are set up.

Should I start with the rear and simply "shift" the front by hand (manually moving the chain) while setting up the rear derailleur? Or is it better to start with the front and manually "shift" the rear in this same way?

Thanks!

Referenced Park tool videos:

https://www.parktool.com/en-us/blog/repair-help/rear-derailleur-adjustment
https://www.parktool.com/en-us/blog/repair-help/front-derailleur-adjustment

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2 Answers 2

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The most logical order of operations when starting from nothing is:

  1. Install rear wheel and cassette

  2. Install RD and set the limits based on the pulley centerline to the appropriate positions on the cassette, moving it by hand

  3. Install the RD cable and set the tension so the guide pulley is coplanar with each cog at each position

  4. Attach and position the fd.

  5. Install the chain, manually putting it on the large ring for sizing if needed.

  6. Set the RD b-gap

  7. Finish installing and adjusting the FD.

  8. Go through all the gear combinations and make any adjustments needed to rear shifting. (Which should typically only need to be minor, because while the front ring position does have some bearing on how far away the guide pulley is from the cogs on an offset-guide-pulley RD, this has little if any impact on optimal shifting adjustment in most cases.)

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  • In step 2, you mean that I would set the limit screw based on the pulley centerline to the largest cog (for low limit) and smallest cog (for high limit)?
    – Dan
    Commented Feb 12 at 1:20
  • In step 3, what do you mean the guide pulley being coplanar? Does this mean it lines up with each cog?
    – Dan
    Commented Feb 12 at 1:21
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    @Dan most RD/shifters (Shimano and others) work best when the pulley centerline is centered with the large cog teeth at the low end and the surface of the small cog face at the high end. Yes, coplanar = in the same plane, sharing the same center line (other than the smallest cog, as above). You don't need to remove your FD no.
    – Nathan Knutson
    Commented Feb 12 at 4:17
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    Yes. As for why the difference, that's just how most derailleurs are designed, and you'll see the distinction in every Shimano dealer manual for example. This is a tangent but supposedly it has to do with the return spring tension being at its most minimal on that end, so it's allowed to overshoot slightly. In other words if it was designed to target dead center as in the other cogs, it would sometimes have a hard time getting all the way there. The why isn't really important in this case though.
    – Nathan Knutson
    Commented Feb 12 at 17:29
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    The typical by the book sizing method involves putting the chain in large-large. To do that without fighting the fd and with no cable installed, typically you can just put the fd low limit screw all the way in so that the cage is over the big ring. In practice, small-small is a good way of sizing the chain for most RDs, exceptions being the modern 1x-specific ones. The chain should always be in place when the fd limit screws are set "for real."
    – Nathan Knutson
    Commented Mar 21 at 16:09
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I have stands that hold the bike's rear tyre just off the ground. It really helps with stability while faffing with gears.

My order would be:

  1. Install tyre/tube and cassette on wheel, and put wheel into frame.
  2. Fit both derailleurs to bike
  3. Install chain on "big:big" and feed it through rear derailleur to get a chain length. Cut chain with an extra link over where you think it is (ie, err on the side of caution when cutting)
  4. Add inner-cables to both derailleurs with housing etc
  5. Wind the RD barrel adjuster mostly in, along with any downtube or inline adjusters. New inner cable always stretches/bedds in.
  6. Set chain on second smallest rear cog and click the shifter so is at the smallest cog (yes this is a mismatch intentionally)
  7. Pull the RD inner cable through as much as possible by hand and clamp down with the RD pinch bolt. Trim and cap inner cable.
  8. Hand-pedal cranks and check rear-indexing. Adjust barrel as required.
  9. Check/adjust the lower and upper limit screws on the RD. The upper one should just barely allow the chain onto the biggest cog, to minimise chance of jumping over.
  10. Once the rear is sorted, move to the FD.

Front Derailleurs are hard - they have two extra degrees of adjustment above the RD's options (twist around seattube and height above chainrings) as well as how far it pushes/pulls chain.

Additionally, the FD is working on the section of chain that is under tension. By comparison, the chain tension at the RD is far lower.

A double chainring is easier than a triple/quad. Given you have a friction front shifter, then I'd aim to have the "resting" position to be perfect for the smallest chainring by setting the lower stop. This means the cable is not under tension when in the smallest chainring and its less likely to drop off to the inside and hit frame.
Then set the upper stop last. That lets you throw the lever in either direction and hit the right spot. To get the middle ring, you have to use your ears and pedal lightly for a moment.

Finish by working through all gear combinations. If small-small or big-big are a little noisy, that may be necessary. Your regular gear combinations should be as smooth and quiet as possible.

Then adjust your brakes to make sure they are all functional still. It is easy to overlook this in the rush to test the new transmission changes.

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    In step 4, you mean no housing? If so, why not? Also, by resting position of the front shifter, you mean where it is pointing straight back? Finally, why would this affect the adjustment of the brakes?
    – Dan
    Commented Feb 12 at 1:23
  • @dan er - definitely with housing. Resting poistition meaning where it is when the cable tension is off, so the limit screw holds it in the right place as opposed to depending on the cable all the time. And confirming that your brakes work is easily overlooked, should not be forgotten when you're keen to test your transmission changes.
    – Criggie ♦
    Commented Feb 12 at 1:37
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    OK, I assumed since you said "inner cables" you meant no housing.
    – Dan
    Commented Feb 12 at 1:40
  • @Dan fair point - I've just done this on a road bike, and the outers were in place already so didn't need consideration.
    – Criggie ♦
    Commented Feb 12 at 1:43

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