Standard vs Compact road cranks.
Saw this article at roadbikerider.com. Thought of sharing.
------------------------
Crankset Considerations
Unless you're in the market for a new crankset, component group or road bike, you may be unaware that a longstanding technical tussle is being decided. It's apparent in what Campagnolo and SRAM are offering in their component groups this year, and in the way many new road rigs are equipped.
The relatively new "compact" double-chainring crankset has supplanted the triple. It's now the most popular lower-gear option for sport road bikes.
Don't get me wrong. Three-chainring cranksets are still available. Shimano offers the option for all their road groups. And triples will never go away. They're needed for loaded touring and by most mountain bikers.
But consider that SRAM offers compact doubles throughout its road line, and it recently introduced the high-end "XX "off-road group with a double-chainring crankset. It has quickly become popular.
Campy, which only a few years ago offered triples in almost every group, has also gone all double. It's your choice -- standard or compact rings. (You can still purchase a Campy triple as a separate component.)
Because spring is a big bike-buying season and you may soon be faced with a crankset decision, let's look at the options.
A standard double crankset has chainrings of 39 and 53 teeth, while the most common compact has 34/50 rings, with 36/50 also available. A typical road triple has rings of 30, 39 and 52 (or 50) teeth.
You want a crankset that provides the appropriate gearing for your terrain and fitness. It should help you make it over the toughest hills, keep up with your friends and be able to cover the distances you like -- all efficiently and comfortably.
Triples are losing favor because, while the third chainring provides very low gears for steep climbs, it comes at the cost of a more complicated and slower shifting sequence. A triple also adds weight and complexity. Special equipment is often necessary -- bottom bracket, front and rear derailleurs, front shift lever -- and a longer chain. Given equal quality, a triple crankset is more expensive than a compact or standard double.
The compact crankset solves all the triple issues. With rings of 34/50 teeth it allows simple and fast shifting. It provides gears almost as low (easy) for climbing. It saves weight even compared to a standard double. Usually, no special parts are required to switch from a standard double to a compact (or back again).
Using a cassette with an 11-28 tooth range, a low gear of 34x28 will make climbing easy for most riders and a 50x11 high gear is plenty for fast descents. Keep in mind that today's bikes are lighter than ever, which helps against gravity.
So, who would want a standard 39/53 double? Mostly performance-oriented riders that are strong enough or have terrain flat enough not to need the low gears coming off a 34-tooth chainring. For them, it's more important to have smaller differences in effort with each shift.
On a standard double, the smaller tooth difference between the small and large chainrings lets the rider shift mostly on the cassette to fine-tune the gearing. Chainring shifts are made only when a large change in the gear range is needed.
To these strong riders, smaller chainrings are a disadvantage because they don't need the lower gearing. But for most other riders, a compact makes lots of sense, and particularly so compared to a triple.
- Login or register to post comments
Email this page
me not strong rider so prefer compact crankset than having triple on a road bike. if penang terrain is flat like singapore probably I' ll use standard crankset 52/39 or 53/39. here got balik pulau, tlk bahang and plenty of short distance hills to climb.
btw, anyone notice any difference between solid and hollowtech crankarms or it is all in the mind? ultegra 6700 already have hollowglide chain ring. currently using R600 crankset (between tiagra & 105 level)
i read some where, the bolt size of standard crankset and compacts is different. is it true? standard crankset has 130mm bolts and compact comes with 110mm bolts.
Ok this is my explanation:
The idea of hollowtech is from the thin shell design, which is also a standard teaching material in Strength of Material in Mechanical/Structure engineering courses. For this design the vendor achives the following using the same building material:
1. Using less material to create something that achieve the same strength.
2. Getting a lighter part.
So we are actually paying more for the same crank that using less material to build since the arms are hollowed out...
my crank gives some "tick-tick..." sound when I pedal on the right side. left side is fine. that' s why am looking into this crank stuff lately. already check the pedals but yet to look at the bottom bracket, need that specific tool to open it.
just looking at the options available for future upgrades, at the moment still can spin and climb hill with the ticking noise.
56XX is facing out soon, heard that 57XX launching in May with 10% cheaper than 56XX. 66XX is not easy to find now and 67XX and 7XXX too costly, better use the money to buy gold.
shimano fan since 18yrs ago, no campy or sram.
BB konked liao lah. Time to change the BB while waiting Shimano 5700 to come out in June.
http://www.cyclingnews.com/features/first-look-new-shimano-105-road-groupset
thanks mate, will look into the BB soon.
yes, that' s the only part I have not check.
the pedals are new and the crank looks pretty solid.
Chicken:
You are referring to BCD, Bolt Circle Diameter.
It is common to compact crank has smaller BCD(110mm) crank spiders compares to the current standard crank set(130mm). I can't find the actually reason why smaller BCD is used. But I think it could be because of:
1. To allow it to use chainring with smaller tooth counts. The original crank cannot accomodate smaller chain ring with 34t and and below.
2. The origin of the compact crank design(it derived from MTB crankset).
Btw, it was common to have standard cranks with 110mm BCD last century too, so it's nothing new.
Info:
http://en.wikipedia.org/wiki/Crankset#Bolt_circle_diameter_.28BCD.29
http://www.sheldonbrown.com/gloss_bo-z.html#bcd
http://www.sheldonbrown.com/gloss_cn-z.html
thanks for the detail info.
does that mean in future if want to upgrade the compact crank with larger chain ring(53/39) it is not possible due to different BCD size.
It can be done as long as you can find chain ring with 110mm BCD. I know few vendors do have chain ring set with 110mm BCD.
for recreational riders in Penang, the compact crank should suffice. I am using Campagnolo (53/39) SR11 on my roadbike and I can hardly climb Tun Sardon with good cadence due to my 85kg body weight. Also, many cyclists thought that it was not macho to have a triple. But, many European pro cyclists are using triple for big climb. The choice of crankset should suit your chosen/routine terrain.
Just my 2C
Cheers
sk