Crankset Advice needed for noob

[LeadLegs]

Hi all, first post here, great looking forum! It seems my mid thirties body is not putting up with motocross like it used to (and the surgeons bills are starting to get some raised eyebrows with my health insurance company). So I have bought a 2nd hand road bike - a Specialized Roubaix which is fricking awesome. Its time for a freshen up in the drive train so I am going to replace chain rings, chain and cassette.
Chain and cassette aren't a prob the prices in NZ seem to be pretty good compared to a lot of places overseas when postage is considered (happy to be corrected there). I have an issue with the chain rings; the guy who owned the bike before me has put some carbon pedal cranks on it which are cool, it is a compound set (110mm BCD). This seems to limit my options for chain rings and the large ring seems to be a bit pricey.
Ideally I would like to keep the carbon cranks (admittedly mainly cos they look uber cool!) but am now considering going to more mainstream sized crankset to open up some more gearing options. The larger sizes seem to be a lot cheaper than a 50T 110mm chain ring.
Do I bite the bullet and replace the existing 50T ring or scrap the whole lot and find a decent priced 2nd hand crankset? Am I being a bit of a girly spongy pud having a compound crankset /img/vbsmilies/smilies/smile.gif?
The gearing feels pretty good where it is at the mo, I am sure as hell no Bradley Wiggins so can't make it too much taller.
Anyone recommend best sites / places to get the parts from? I am in Akl in NZ.

Any comments appreciated.

Cheers

 

[alienator]

If the gearing is about right where it is now, why change? All that matters is the gearing. Whether you get the desired gear range from a standard (130mm BCD) crankset or from a compact (110mm crankset), the end result is the same. Again, the only thing that matters is the gearing, i.e. the gear ratios produced. As for the cost between 130mm BCD and 110mm BCD chainrings, there shouldn't really be any difference. One of my best friends lives in Auckland and has been buggering sheep and corgis there his whole life. From having purchased in the US, the UK, and other places, he says that people in the Antipodes get buggered on bicycle kit pricing. If he orders, he tends to order from the UK. You can also probably get pretty good pricing from Taiwan. I would avoid any place that is located in Malaysia or Indonesia, right now, as those countries are home to a great number of fake bike internet businesses set up to steal people's money. What is the brand of crank set that you have? Also, it's only polite to post pictures of your bike.

 

[LeadLegs]

Thanks Alienator, some handy advice. Interesting to hear re Malaysia or Indonesia. Your friend is right, not about buggering sheep and corgis (damned aussies giving us a bad name) but about the price of parts. If you get them from the shops they are big dollars, there are some good sites in NZ that have cropped up over the last few years that are well priced. Ordering in from the US or UK is often cheaper at first glance but the postage usually kills it. Strong NZ$ at the mo is really helping overseas purchases. Chain reaction has free postage for orders over a certain amount to NZ.
You are right about the gearing but I was kind of thinking that moving forwards should I want to change ratios in future it would be easier to do with a standard sized crankset. More options available(?). Given that I need chainrings now, thought it might be good time to look at a complete crankset. The price isn't that much different for 2 rings compared to a complete Ultegra crankset.
The cassette is an Ultegra 12/27 which I believe is now obsolete. Looks like I will need to need to change gear ratios (if only slightly) regardless.
Not sure about the brand of crankset currently on the bike but the actual pedal cranks have Specialized written on them.
Will try and get some photos up, the bike is nothing flash to look a though, the thing that slows it down is the red faced, sweaty dude puffing and panting away on top of it. My last one was a chromoly framed mountain bike with slicks for commuting on. The Roubaix feels like getting into a race car after driving a farm hack in comparison.

Cheers

 

[CAMPYBOB]

Given that I need chainrings now, thought it might be good time to look at a complete crankset. The price isn't that much different for 2 rings compared to a complete Ultegra crankset.

You are on the right track. You will be dollars ahead to but a complete crankset. You may even want to change lengths to a 172.5 or 175. arm while you are at it. Might as well replace the bottom bracket while you are in there with your tools.

Mot-X? Save up for the future knee replacements! A few of my ex-cross buds that cycled with me for years are now having new hardware installed in their knees...I hope you never need it!

It looks like 12-23, 12-25 and 12-30 are the current Ultegra cassette offerings (10-speed). The 11-28 may be close to what you are looking for in ratios?

 

[alienator]

You know, you haven't said what is wrong with the current chain rings. Also, what is wrong with the current gearing? As I suggested before, going with a standard crank instead of a compact crank doesn't offer more useful gearing options. It only offers different gearing options on the front and perhaps slightly higher gearing ratios on the back. I'd highly recommend not buying a new crank until you figure out exactly what sort of gearing you actually need. If nothing is physically wrong with the current chain rings, leave 'em on. Without being able to figure out what gearing you actually need, you run the risk of buying something that doesn't mesh well with your abilities or the way you ride. I understand that the hills in the Auckland area can be quite punchy, i.e. steep and short-ish (The Race of 6 Friends) is not for the faint of heart. I understand that there are a fair number of rides over metal roads. Big, tall gears may not work so well for you on steep climbs or climbing, metal roads. FWIW, you can find new chain rings at dirt cheap prices on eBay. FYI, you don't have to confine yourself to Ultegra cassettes. You can also use 105 and Dura Ace cassettes, as well as SRAM cassettes. Use whatever gives you the gear ratio you need. You don't gain anything, though, by going to, say, a Dura Ace or Ultegra 11-25 over a 105 11-25 except for a small decrease in weight and a potentially shorter lifespan.

 

[LeadLegs]

Ok so based on your guys advice I thought I would get the bike down to my LBS for a professional opinion of what bits I should be replacing. The guy at the shop agreed with what I thought which was good - cassette, chain and chain rings. Alienator to answer your question re what is wrong with the rings - its wear and tear. The tooth profiles aren't what they should be. The guy at the shop said it is a good time to look at doing the crankset due to the cost being similar for rings vs a complete crankset. The shifters, derailers and cables all look sweet so hopefully a quick freshen up will have it shifting mint.
The guy at the shop said it didn't take him long to check it over so there was no labour charge, even when I said I was more than happy paying for his time. Anyway, my wife picked up the bike, when I got home I notice it now has 2 nice sized dings out of the top frame tube paint. /img/vbsmilies/smilies/mad.gif I am going to start another thread with pictures. Will call the shop again today and see what they are going to do about it. Maybe they insisted on no labour fee as a get-out-clause(?) Gutted, the frame was mint before this.

Now to hijack my own thread - Re the gearing, it currently has 34/50 on the front and 12-27 on the rear. I am happy going slightly taller than this, how will a 39/52 11-28 affect things? Is there a rule of thumb for say x number of teeth on chain ring is equal to x number of teeth on cassette in terms of gearing. E.g. On a motorbike you work roughly on about 1 tooth on front sprocket = about 3.5 teeth on the rear - i.e. going from 12T front sprocket and 48T rear is the same as running a 14/55.

Cheers

 

[daveryanwyoming]

Originally Posted by LeadLegs .

...Now to hijack my own thread - Re the gearing, it currently has 34/50 on the front and 12-27 on the rear. I am happy going slightly taller than this, how will a 39/52 11-28 affect things? Is there a rule of thumb for say x number of teeth on chain ring is equal to x number of teeth on cassette in terms of gearing. E.g. On a motorbike you work roughly on about 1 tooth on front sprocket = about 3.5 teeth on the rear - i.e. going from 12T front sprocket and 48T rear is the same as running a 14/55.

Your rule of thumb is pretty good for bicycles as well, but most folks either look at gear ratios as in chainring_teeth/cog_teeth or many cyclists (especially folks who've ridden and raced track bikes on velodromes) work in 'gear inches' or the equivalent wheel diameter of a direct drive high wheeler bicycle which is given as:

Chainring_teeth/cog_teeth*wheel_diameter (usually taken to be 27" even though that's not exact for most actual wheels and tires)

Lot's of good online gear inch calculators out there like: http://sheldonbrown.com/gears/

But a quick comparison of your high and low gears now vs. the change you're thinking about:

34/27*27 = 34 gear inches low gear (now)
39/28*27 = 37.6 gear inches with change (you'll lose a bit of low end gearing for climbing steeper hills)

50/12*27 = 112.5 gear inches (now)
52/11*27 = 127.6 gear inches (quite a bit of added top end but really only useful if you're currently winding out a lot on descents or perhaps with big tailwinds)

Personally if your local riding includes a lot of climbing on steeper grades I'd stick with the compact and perhaps switch to the 11-28 cassette which will extend both the high and low gears relative to what you have now. If your riding terrain is flatter then the 52(or 53)/39 crankset either with the same cassette or perhaps with an 11-26,27,28 or whatever you like for your uphills would make sense.

-Dave