Chain Route - Idler, Tie Rod Clearance? Under/Over?

edited May 2016 in Rambler
Hi folks, 

I just picked up a used, 2013 Rambler, 24-speed. Notice a cautionary note in the manual that the chain must be routed BENEATH the tie-rod, but that note accompanies a diagram of the 8-speed setup. There is no likewise note for other models, so I'm not sure if the BENEATH instruction applies exclusively to the 8-speed or all models. Right now, I've got the chain on the Rambler routed beneath the tie-rod, but I've seen photos that appear to run the chain above the tie-rod. Which is correct?

Also, how much clearance should I expect between the chain and the tie-rod? My set-up right now (BENEATH) allows almost next to no clearance. All I can reason is that I've left the chain too short and that the result is insufficient sag. I've also tried the chain ABOVE the tie-rod, but then chain rubs on tie-rod as if chain sag is excessive. No good. Scratching my head. 

Also, 'L' bracket purpose and position?  Is its purpose to keep the chain from leaping out of the idler? Which is the optimal position?  12 o'clock? 2 o'clock?  11 o'clock? 

Any input on these questions much appreciated!



  • edited May 2016
    Thanks Jamesr for weighing in on your various chain management setups.  I have no issues with stock chain tube.  It's the return chain routing I'm struggling to get right. 

    You don't mention whether your return chain route travels above or beneath your tie-rod. I'd hope to establish which route is the intended design so I can eliminate that variable.

    I also have a sneaking suspicion that once I get that correct, I'll still have the chain length to get right. On my diamond frame bikes I measure chain length with "small-small" (chainring/cog) method with just enough tension on the rear derailleur such that the chain clears the jockey wheel by a few millimeters. This method works just fine.

    Others subscribe to the "big-big plus 2 links" method.  

    I'm wondering if determining proper chain length is complicated in any way by factors which do not apply on a regular diamond frame bike, such as the addition of the idler, the sheer long length of the chain itself, chain tube, the various angles or number of angle changes a chain follows on a trike. I wouldn't think it would make much, if any, difference, but I might be missing something with that assumption.   

  • Thanks for sharing your experiences with chain management, Elrique. I've tried routing the return chain above and below the tie rod, but neither are satisfactory, for as you suggest, different chainring/cog combos have an effect. 

    The longer chain may hold advantages like accommodating chain management gizmos, but it seems to me that an optimal goal would be the shortest possible chain, mainly to optimize clean, crisp shifting. That said, the short chain goal may be trivial if it only means a few links over the total length of 10 or 12 feet of chain. 

    Your tie-rod spacer solution appears to be clean and simple. What did you use for spacers? 

    It puzzles me, however, that if I'm not the only one who has experienced chain rub on the tie rod whether this ought to be attributed to incorrect user setup or a deficiency of original design. Given the hard time I've had finding others (except you!) with the same issue, I'm much more inclined to blame myself for setup shortcomings. 

    It also puzzles me when I try to imagine that return chain routing above or below the tie rod on the derailleur models wouldn't matter at all to the original designers. Certainly, with the internal geared hub model Terratrike takes pains to clearly specify chain routing underneath the tie rod. 

    Flexibility, however, must be built into the Rambler idler location design since it moves fore and aft quite a distance with the full range of seat adjustments. 


  • Something else to realize is that the straightest route is always possible, especially with long chain runs.

    The weight of the chain itself causes some sagging. Any attempt to force it straighter just adds more force to overriding whatever spring tension the derailleur(s) have. In some cases *adding* chain will make the chain ride higher off the ground.

    - PaulNM 
  • Thanks for the observations and tips on chain management, Elrique, Paul, James. I think I'll start by experimenting with the easiest stuff first, like various seat/boom positions and chain lengths. I'll take some photos, too. 

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