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I've recently become the proud new owner of a lovely late 90's steel road bike with some not so lovely "old school" gearing (53/39 chainrings and 11-25 8 speed cassette). As someone who both loves her knees and naturally keeps a relatively high cadence I am looking to change my bike have the option of lower gear inches. I know from my experience riding around on my touring bike that my ideal lowest gear inch option would be about 30 inches (using this to help calculate gear inches). I am including the different options I can think of with the relevant research I've already done below. I would love to hear what would be the easiest, cheapest way of achieving this and if there is some option I am overlooking.

Option 1. Get a cassette with larger cogs. The first issue I would worry about here is the rear derailleur which I believe is this one. The listed max cog size is 28t though I know Shimano recommendations tend to be a little conservative. Judging from the gear inch calculator I would probably need 32t or even 34t to get the desired minimum gear inches. If I needed to replace the rear derailleur would I be able to do that and still use the 8-speed Shimano brifters that are currently on the bike?

Option 2. Get smaller chainrings. The issue here is that the crankset on the bike has a 130 BCD so I think the 39t chainring is basically as small as is possible to fit on them (Sheldon's sheet suggests that the minimum for 130 BCD is 38t). So I'd need a new crankset and hope to find something that avoids other compatability issues (with e.g. the bottom bracket or the front brifters). Unfortunately, calculations suggest that even a 50/34 wouldn't quite give the desired minimum gear inches with the 11-25 cassette.

Option 3. Some combination of a larger cogs on the cassette and smaller chainrings. This option seems to require more work than either Option 1 or Option 2 and I'd guess it would be more expensive but I am not sure.

Option 4. Put a new groupset on and just make sure the new chainrings and cassette will provide the desired gearings. This one is definitely the most expensive and requires the most work but I am including it for completeness.

For reference, I plan on doing most/all the work at a local free "Open shop" run by a non-profit dedicated to teaching people how to take care of bikes but if anything is very technical/hard/requires special skills I may go to a LBS for that.

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    Changing your crankset I bet will be easier than you suspect. Late 90's road bike means you have pretty good odds of a square taper BB, which means there are roughly a gazillion crankset options you can order through your LBS. Only compatibility concern would be moving the front derailleur if it's a braze on type, but you might be just fine as is.
    – whatsisname
    Commented Feb 1, 2021 at 23:37
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    @whatsisname Yep it is a JIS square taper BB so that is good to know, would you be willing to write this as an answer?
    – GageMartin
    Commented Feb 2, 2021 at 0:36

2 Answers 2

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You seem to have a good handle on your options.

A wider-range cassette, and a derailleur with a long cage, will probably give you the most bang for your buck. Switching from a 39t small ring to a 34t small ring is comparable to switching out your 25t big sprocket in back for a 29t sprocket. This is a good tool for playing around with gear ratios.

If you do go with option 4, you have more options. I recently built up a new bike with 46/30 in front and 11-30 in back. This gives a high enough top gear for me (46x11 is plenty fast for the kind of riding I do), and a 1:1 ratio at the low end, with tight spacing in between. Shimano, FSA, and some of the more exotic brands offer cranks with 46/30 chainrings.

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  • Thanks Adam, just to confirm do i need to worry about the compatibility between the new derailleur and my current shifters?
    – GageMartin
    Commented Feb 2, 2021 at 0:52
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    Compatibility is a question. The key parameter you need to worry about is the cable pull ratio. I think that, looking only at current derailleurs, a Shimano Sora or Claris medium-cage would work; some Microsoft derailleurs also might work.
    – Adam Rice
    Commented Feb 2, 2021 at 1:20
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    To correct autocorrect: not Microsoft but Microshift.
    – Adam Rice
    Commented Feb 2, 2021 at 18:45
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Depends how much originality matters.

If I were you I'd look around for a donor bike and see how many useful parts you can get off it. Ideally, a triple front crank would be great, letting you use the 11-28 sized cassette and will give a low-low gear ratio without loosing the 53-11 needed for High Speed tailwinds and downhills.

If looks are important to you, a silver/chrome groupset would be ideal. Black groupsets look too modern.

You may also have preferences about shifters, whether downtube, stem, or STI brifters suit you. Personally I prefer brifters, but have stem friction shifters on the retro road bike. Tempted to fit a 7 speed right-hand Shimano RSX brifter, but then I loose the sissy brake lever which adds significantly to the retro look.

Your other unstated option is to simply put up with it as-is. Hills will be harder, but the added effort you have to put in may make you faster. Its counterintuitive, but I went up a steepish climb faster on a bike with a double than I do on a bike with a triple... though it was unpleasant and hard on the knees.

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  • I probably should have said i don’t really want a triple for a few reasons (some probably less good than others) but I am upvoting for anyone else who stumbles upon this.
    – GageMartin
    Commented Feb 2, 2021 at 0:43
  • Also a previous owner wore out the chainrings and replaced them with black rings which is an ... interesting look when combined with the silver cranks
    – GageMartin
    Commented Feb 2, 2021 at 2:14

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