New adventures in indexing

A 1984 Suntour ARX pre-index shifting rear mech. A 7 speed Shimano SIS freewheel. An 8 speed Shimano Ultegra bar end shifter. These things are not fated for a happy menage a trois when drivetrains are concerned. And yet I have today discovered that they work. And pretty darned well.

Back in 1984 – apart from Shimano’s ill-fated Positron indexing system, SIS gears were the stuff of whimsy and friction shifting ruled.

arx

Suntour’s patented slant parallelogram derailleurs were still the sweetest shifting mechs on the block but Shimano was making rapid progress.

The ARX was at the tipping point, designed as a response to Shimano’s 600AX futurism – and to replace the ageing yet brilliant VX range. However it was still a fine piece of kit, especially for a mid range derailleur.

I’ve wanted to have the option of indexing for a while, having ridden for a few years on a positively ascetic friction-only setup.

Furtive searching of Sheldon Brown’s site confirmed that 8 speed shifters will work across a 7 speed block because the difference in cog spacing is minimal (4.8mm for 8 speed and 5mm for 7 speed according to the mighty SB).

The question was, would my achingly lovely Suntour ARX generate the correct amount of mech movement for a given amount of shifter cable movement? This was a question that Sheldon and a host of bike forum-o-nauts couldn’t readily answer.

There was only one thing for it – to get the bike in the stand and see if it worked.

It was with much trepidation that I snugged up the 4mm Allen bolt holding the cable and tentatively spun the pedals and worked the bar end shifter. Especially as the setup currently has no barrel adjuster to finesse the cable tension.

So one can imagine my surprise and delight when the chain sprang willingly from one cog to another and back again with very little complaint.

For me this experience is potential proof of a number of things:

  1. There may indeed be a benevolent and omnipotent God
  2. I may be a mechanical genius
  3. The strict laws of product compatibility may not be all that

Here endeth the lesson. Happy shifting and amen.

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8 thoughts on “New adventures in indexing

  1. Greetings, I’m new to your blog. Glad I came across it.

    I love older bikes and have 11 and counting. 1993 is my newest, 1974, the oldest. Nothing too exotic. Sadly, i have never had similar love for new bikes. All the marketing and brand exhibition leaves me cold.

    A question…Did you keep the old cable or change to compressionless cable? I wonder if there would be a difference.

    1. theeverydaycyclist

      Hi John – firstly thanks for the kind words about the blog and welcome!

      New bikes do nothing for me but I am a fan of sympathetic upgrades to old bikes to make them safer and more enjoyable to ride – hence the bizarre combination described above.

      I wanted to retain the look of classic components but gain indexed shifting.

      The old Suntour derailleur is so elegant and can be polished with Autosol or suchlike, unlike the new stuff which is bloaty, anodised and painted ephemera as far as I’m concerned.

      Now the cables – this bit will make you laugh. Because I was running friction before, cable type and quality is almost an irrelevance and I’d used 5mm brake outer and it still shifts sweetly, without a barrel adjuster too. I must have hit a the sweetspot first time.

      It’s all down to getting your high limit screw set so your chain runs sweetly on the smallest rear sprocket, before you’ve even got a cable in.

      Then all you have to do is pull the cable tight, snug up the bolt, run through the gears a few times, undo the bolt, snug up again and you should be within a gnat’s of perfect!

      1. I agree with your philosophy. Nothing is sacred but the aesthetic. I polished out a first generation Deore XT RD to remove the graphics as a replacement for a newer plasticy “aero” look RD.

        I will absolutely try this adjusting procedure. Did you remove the barrel adjuster on the RD as well?

        Peace

    1. theeverydaycyclist

      It’s maiden voyage was an evening spin to my Mum’s house and I’m happy to report that it’s sweet as a nut!

      The action of shimano bar end shifters is so positive – I tried a friends bike with STI shifters and they just feel so sloppy. That and their complexity and bulkiness just turns me off.

      Happy riding Chris.

  2. Hi there, found this blog while searching for an answer for my question, but since I cant find any contact form I will go wild-and-crazy and just ask my question here.;)
    Its very simple, my intention is to buy a old frame/friction gear bike, its 6 speed now, but Ive got a pair of 8 speed wheels in good condition, I would like to use, is it possible just to change them wheels and then just ride? Yeah I know about the 126mm vs 130mm spacing, but if you cold set to 130mm?

    kind regards
    max

    Great blog btw.

  3. mitchj68

    G’day mate – Greetings from Down Under!

    I came across your blog a few months ago & have since been working my way through your site from the start. It has made for very interesting reading – the story’s of winter riding & having to put on multiple layers of clothing made me feel cold just reading them! It’s really interesting to get completely different perspective on the challenges of dealing with weather I couldn’t imagine having to deal with. Watching your different bikes evolve over time has been good too. Keep up the good work!

    Here are a couple of blogs you & your readers might be interested in. One is “A new Recyclist” at http://www.rustybikebell.wordpress.com – a great site about rebuilding old neglected bicycles with nice pics & story’s of the blokes local bike tracks. Well worth looking at.
    The other one is mine, called “My Riverland Bicycle Life” at http://www.mybikesmj.wordpress.com – I’m hoping to run it along similar lines but it’s still early days yet (so don’t expect too much ha ha!).
    Anyway, great site mate – I look forward to the next instalment!

    Cheers, Mitch

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