Large to Compact Campgnolo Chainrings - Stronglight?

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Large to Compact Campgnolo Chainrings - Stronglight?

Postby rangersac » Fri Nov 09, 2012 10:11 am

Hi all, I've recently acquired a lovely second hand De Rosa road bike, kitted out with around 2004 vintage Centaur Groupset (ultratorque 172.5mm cranks). It has 53/39 chainrings on the front, and whilst they are magic on the flats, for hilly 'ole Tas I'm thinking of getting some compact chainrings so that the aim of getting up Mt Wellington doesn't look so daunting. Whilst I've done fairly basic bike mechanics (derailleur adjustment, brakes etc.) I've never attempted to change chainrings or cassettes, however now seems like a good a time as any. So the first question is can I just remove the current set and replace with a 50/34 on the spider, lower the front derailleur and shorten the chain or is there more to it than that? Also has anyone used stronglight chainrings on campy cranks, and if so how did they go?
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by BNA » Fri Nov 09, 2012 11:27 am

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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby RonK » Fri Nov 09, 2012 11:27 am

No, you will have to replace the crankset. This is because a 36t or 34t chainring has a smaller bolt centre diameter (BCD) than a 39t chainring.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby rangersac » Fri Nov 09, 2012 11:49 am

RonK wrote:This is because a 36t or 34t chainring has a smaller bolt centre diameter (BCD) than a 39t chainring.


Thought this was the case. Bummer, might just have to harden up for a bit.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby elantra » Fri Nov 09, 2012 11:50 am

RonK wrote:No, you will have to replace the crankset. This is because a 36t or 34t chainring has a smaller bolt centre diameter (BCD) than a 39t chainring.

+ 1
Dont touch the Crankset !

Get a replacement cassette, something like 13-28.
You can sell or swap a slightly worn cassette on this forum if you really want to
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby rangersac » Fri Nov 09, 2012 12:09 pm

elantra wrote:Get a replacement cassette, something like 13-28.


Thanks. Will the 28 make that much of a difference in the climbs? I've got a 12-25 at the moment. As an aside I was a bit surprised at how quickly I ran out of gears on my inaugural trip last weekend. I wasn't climbing anything massive, and the steepest gradient I attempted probably only touched 10%. My fitness should be reasonable considering I commute 60km a day with about 600m of climbing, and average 28-29kmh. I do this on a flat bar Shimano 2200 triple setup on which I rarely use the bottom chainring.

As I said before maybe I just to harden up and stop being precious! The groupset runs superbly so seems a shame to touch it.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby Ross » Fri Nov 09, 2012 12:18 pm

I haven't ridden it, only driven up, there but Mt Wellington is pretty tough, goes for just over 11km and varies in gradient between 7% and 15% in areas so a 28 tooth cassette would come in pretty handy I reckon.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby RonK » Fri Nov 09, 2012 12:51 pm

rangersac wrote:The groupset runs superbly so seems a shame to touch it.

Of course it does - it's Campy.

Ultratorque Centaur would be much later than 2004, probably circa 2009, so it would be easy enough, albeit somewhat expensive to buy a compact chainset. But this really is the best solution if you are not a natural climber.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby LG » Fri Nov 09, 2012 2:16 pm

you will notice a diference with a 28 cog compared to 25.

And Ross, you make it sound short at only 11km, from the city it's more like 20km all up hill :wink:. It's about 11km from the turnoff near Ferntree.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby warthog1 » Fri Nov 09, 2012 4:14 pm

LG wrote:you will notice a diference with a 28 cog compared to 25.


+1
I am not a natural climber either and have gone to a 28-11 cluster and 53-39 set up, having previously had 25-12 and 34-50.
There is not much difference between 34/25 bottom gear at 35.8 gear inches and 39/28 at 36.6 gear inches. Try that first and see how you go. The speeds you are maintaining on a flat bar commuter would indicate your fitness is there, It will just be harder if you are >90 kg, I am 82.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby rangersac » Fri Nov 09, 2012 7:52 pm

LG wrote: It will just be harder if you are >90 kg, I am 82.


That's me unfortunately, 188cm and about 95kg at the moment. Even in absolutely fighting fit trim I've never got below about 88kg. Guess I should think about being a sprinter rather than a climber, but having a Cat 1 climb on your doorstep is too tempting!
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby warthog1 » Sat Nov 10, 2012 9:29 am

Go for the 28t cluster and give it a crack, it's a fair bit lower gear than what you have. You could always get a cheap shim tiagra compact and some bearing cups if that is not low enough. Should be able to source that for <$200
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby AndrewBurns » Sat Nov 10, 2012 9:38 am

If you're running Campy get their 13-29 cassette. I have that on one of my wheelsets for my road bike which has Veloce, the standard RD handles it fine and with the 29 on the back you can tackle pretty much everything. You will spin out above high 50 kph speeds though.
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby warthog1 » Sat Nov 10, 2012 12:26 pm

AndrewBurns wrote:If you're running Campy get their 13-29 cassette. I have that on one of my wheelsets for my road bike which has Veloce, the standard RD handles it fine and with the 29 on the back you can tackle pretty much everything. You will spin out above high 50 kph speeds though.

That is a great option that you dont have with shimano std cage derailleur. 39/29 = 35.2 gear inches, lower than 34/25 :)
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby rangersac » Sat Nov 10, 2012 9:07 pm

AndrewBurns wrote:If you're running Campy get their 13-29 cassette

warthog1 wrote:Go for the 28t cluster and give it a crack, it's a fair bit lower gear than what you have. You could always get a cheap shim tiagra compact and some bearing cups if that is not low enough. Should be able to source that for <$200


Decisions, decisions, so many choices! Actually it's been a few years since I've ridden a proper roadie so getting used to the change in posture should improve things. I'm not planning to attack the mountain tomorrow! Thanks for the advice.

AndrewBurns wrote:You will spin out above high 50 kph speeds though


Shame that, I do like going fast!
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Re: Large to Compact Campgnolo Chainrings - Stronglight?

Postby AndrewBurns » Sat Nov 10, 2012 9:22 pm

Well it's more of a problem for me because I have both a compact crankset AND the 13-29 cassette. It doesn't happen super-often though because generally if I'm going faster than ~55 kph I'm going down a hill in which case I can get much faster without pedaling anyway. The only time I really found it an issue was going down a very long very gradual slope with a very fast group, I fell off the back because I wasn't able to sustain such high continuous speeds.
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