Easy one: Can I swap out a 2 chainring crankset for a 3 ring crankset without buying a new derailleu



PeteinMA

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Aug 4, 2014
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I have just purchased a used beatiful old American made Cannondale R400, all stock still.
I threw on new tires and tubes and started riding road bikes for the first time ever. (im a "clydesdale" who rode mountain bikes for a long while).

I like the bike very much, and it works for my 270lb powerlifter's frame, BUT, I do not have the endurance I need for cycling yet. (Im much more used to pulling a heavy deadlift or squat!) SO, I hope to shed some lbs and get some endurance from cycling!

The problem is the R400 is a dual chainring bike, and I just dont have the endurance or stamina to make it up any real hills without that smaller chainring that a 3 chainring crankset would allow.
So, can I swap out my dual ring for a 3 ring without needing to drop more $$ on a new derailleur? Can the derailleur be adjusted? For what it's worth, I have SORA shifters on this bike...

Anyone help me out?
 

alfeng

Well-Known Member
Jul 23, 2005
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What Cassette does your bike currently have?

You may be able to simply replace the current Cassette with one whose largest Cog has more teeth + a new/(longer) chain.
chain.
  • if your SORA is 8-speed, then look for an 8-speed SRAM or SunRace Cassette
 

PeteinMA

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Aug 4, 2014
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The crankset is a Truvativ Touro A1 with 30/42/52 teeth with a half-inch by 3/32-inch chain and eight-speed, 12-26 teeth cogs. The Casette is, I believe, a Shimano RX100 Casette.


So, you recommend a larger casette rather than a 3rd sprocket?
 

PeteinMA

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Aug 4, 2014
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And, if I went with the 3rd cog, would the derailleur then become an issue?
confused.png
 

alfeng

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Jul 23, 2005
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A front derailleur which is designed for a DOUBLE Crankset can be used, but you may find that shifting from the Granny to the Middle Chainring will be unsatisfactory-at-best .... Your REAR derailleur should be able to handle a 30t largest Cog ... possibly, a 32t. If it were MY choice, I would look for an 11-30 or 11-32 or 11-34 Cassette, first ... If necessary (that is, if the rear derailleur has a problem with a 32t Cog), then I would install a Shimano MTB rear derailleur ... I would change the Crankset AND front derailleur, last.
 

stevegreer

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Sep 4, 2008
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Do you know what the BCD (bolt circle diameter) of the dual chainring is? If you do, or you can probably find out by doing a Google search for whatever type of crankset it is, probably a Shimano RX100 with 42/52 chainrings, then maybe you could find a smaller chainring with the same BCD and just swap that out. It could very well be much cheaper than replacing an entire cassette. Just from a quick search myself it looks like the BCD is 130mm. So you should be able to find a 39t ring in that BCD pretty easily on eBay
 

oldbobcat

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Aug 31, 2003
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Originally Posted by PeteinMA
I have just purchased a used beatiful old American made Cannondale R400, all stock still.
I threw on new tires and tubes and started riding road bikes for the first time ever. (im a "clydesdale" who rode mountain bikes for a long while).

I like the bike very much, and it works for my 270lb powerlifter's frame, BUT, I do not have the endurance I need for cycling yet. (Im much more used to pulling a heavy deadlift or squat!) SO, I hope to shed some lbs and get some endurance from cycling!

The problem is the R400 is a dual chainring bike, and I just dont have the endurance or stamina to make it up any real hills without that smaller chainring that a 3 chainring crankset would allow.
So, can I swap out my dual ring for a 3 ring without needing to drop more $$ on a new derailleur? Can the derailleur be adjusted? For what it's worth, I have SORA shifters on this bike...

Anyone help me out?
Converting to a triple will mean a new front shifter, too, and I'm afraid that shifting with the old double front derailleur won't very suitable. And your R400 predates compact cranksets, so a smaller inner ring is out of the question.

I go with Alf's advice on a wide-range cassette, plus a Shimano MTB rear derailleur, any current model that's not made for 10-speed. An Acera or Alivio level unit should work fine. And you'll need a longer chain, but the chain on that old bike probably needs replacing anyway.

Actually, there's one more option, and that's to replace the whole crankset with a compact uni. But tthat's probably going to be more work and expense than going the cassette route, and, by itself, it still won't reduce your low end as effectively.
 

PeteinMA

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Aug 4, 2014
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I went with the advice of getting a wider range cassette. SRAM 10-39t I think... whatever it was, I discussed the issue with the bike shop mechanic who advised me to do that.... he said the chain was worn (due to age) and so we put a longer chain on....
Rides MUCH nicer up the hills around the Monadnock Mountain region in New Hampshire, close to where I live...
Thanks very much all. Im sure Ill have MORE questions the more into biking I get!

Thanks
 

oldbobcat

Well-Known Member
Aug 31, 2003
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Originally Posted by PeteinMA
Rides MUCH nicer up the hills around the Monadnock Mountain region in New Hampshire, close to where I live...
Thanks very much all. Im sure Ill have MORE questions the more into biking I get!

Thanks
Good deal.

Say hello to southern NH for me. I seem to remember a ride with the Granite State Wheelmen that passed through Peterborough years (decades) ago. And a few autumn hikes up Mt. Monadnock.