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Need to be educated

Old 08-17-20, 10:09 AM
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lhill 
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Need to be educated

My vintage bike has a Shimano 105 Biopace 52/42 crankset with a 12-28 cassette. I love the way it feels when I pedal, the biopace chainrings are great, for me. The 52/42 combination is fine for where I live and ride here in the Houston area, but I intend to spend all of next summer in southern Maine where it is much more hilly, my lowest gear of 42-28t will kill me. I wonder if it would be possible to purchase a used Biopace 48-38-28 triple and somehow convert it to a 48-28 double. Would anyone suggest what some options to a few lower gears might be? Thanks for any help!
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Old 08-17-20, 11:04 AM
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Your best bet is probably to look for a biopace triple crankset on ebay. You could run your outer ring on the middle position and the small ring in its proper place if you want a 48/28 double or similar, or you could run the triple and get a slightly longer spindle. As is the case with conversions like this, you'll need to think about bottom bracket spindle length to manage the chain line, chain length, and a long cage rear derailleur.
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Old 08-17-20, 11:17 AM
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Thanks a lot for your info....food for thought
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Old 08-17-20, 11:54 AM
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https://velo-orange.com/collections/...-crankset-mkii

$200 gets you a new 46/30 square taper crankset.
VeloOrange always have a Winter sale, usually between Thanksgiving and Xmas.

I bought mine for $100 (maybe $125) on sale ~3 years ago.

But that was before all the price increases from US' anti-trade policies were enacted by traitor drumpft.
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Old 08-17-20, 12:35 PM
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You'll have to look closely at the bio pace triples on eBay. Most of them, and really most bio pace from the 80's-90's came on Mountain bikes so most of the cranks are 175's, not 170 like most road cranks of the day. I had no problems with whatever when younger but I have found lately even 172.5's cause knee issues for me so look at your existing cranks and what you may bid on to make sure the length is something you can use.
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Old 08-17-20, 01:05 PM
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Another option is if you have a Bike co-op in your area they may have used mountain triples that you could get for less than ebay.... also I just put a FSA Vero 50/34 crank on my 89 Allez to get better hill gears. And I was able to get it for about $50. Not biopace but it will be hill Friendly also depending on your # of speeds (6 7 8) and gear type (cassette or Freewheel. You might be able to find a gear cluster with 30 tooth big ring set of gears. You can go to Velo base or Disraeli gears to find out the max teeth your particular rear derailleur can handle and if you really want to geek out check the Sheldon Brown gear calculator low gears are your friend
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Old 08-17-20, 02:01 PM
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Originally Posted by lhill View Post
I wonder if it would be possible to purchase a used Biopace 48-38-28 triple and somehow convert it to a 48-28 double.
This webpage shows the smallest chainring you can use for your double crankset's bolt circle diameter (bcd):

https://www.sheldonbrown.com/cribsheet-bcd.html

Your current setup might work if you have a long cage derailleur and a 32t big rear cog. Changing the rear cluster has a much greater impact on gearing than chainrings. Try playing around with an online gear calculator.
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Old 08-17-20, 05:32 PM
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Considering the smallest chainring for a 110mm BCD "compact" double is in the low 30s, the cheapest solution is probably that. There should be compact doubles falling from the trees on Ebay (not to mention in the ISO/trade subforum here), and getting the exact chainrings you want should not be a big problem (e.g. https://www.ebay.com/itm/Camapgnolo-...AAOSwdd9e-jXt) unless you're really stuck on Biopace.
In that case I suggest you purchase a complete Biopace triple and get it rigged for your bike. In my experience of converting from double to triple, the FD is a bigger issue than the spindle, i.e. the original spindle has worked just fine most of the time, but often I've needed to get an FD with wider range, because a triple crank typically moves the outer chainring further out than a double, at least in my experience.
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Old 08-17-20, 08:16 PM
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Everyone, many thanks for all your valuable info. I have lots of time to get the gearing better for climbs and you’ve all given me many options. Thanks again!
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