Compact vs Standard?

GGBiker

Ai_1 wrote:

Bozabyka wrote:

So where is the advantage of a double?

Only three potential advantages I can think of:

1. Higher top end speed in the unlikely event that 50/11 or 52/11 isn't enough.
2. Your typical cruise speed/cadence is more conveniently positioned on the chainrings/cassette meaning less frequent chainring shifts (can't see this being a dealbreaker myself)
3. Machismo/Tradition. If these are your reasons for using a standard then surely you should use 6 or 7 speed cassettes too!

I may be wrong but I suspect "advantage" #3 is the main reason many people use standard doubles and I think it's a very bad reason. There seems to be a lot of snobbery and machismo in cycling, unless it's just on the forums, and these are fairly incompatible with common sense. So, it's often difficult to know what advice to take seriously and what advice should be ignored.

For me reason 2 is the most important, if you are riding on rolling terrain with a compact you end up shifting a lot more between chainrings. This is made worse if riding/racing in a group, if most are using 53/39 then you will be changing gear at a different time than others which causes you to slow momentarily and disrupts the group.

Subtle but real irritations!

bails1310

Slightly digressing, I was just about to push the button on a new Ultegra chainset from CRC, but noticed a '110mm BoltCircle' option, with no others available.

What does this mean, and is there another option of bolt hole that's just isn't visible that may be better/more suitable?

Moonbiker

I think that is the BCD the size they nearly all come in now until they decide to change it again :roll:

So don't worry about the BCD its only a problem if like me you have an old bike & you need to replace individual chainrings. But if you want to know about it read:

http://sheldonbrown.com/cribsheet-bcd.html



I can't source small 39t chainrings the right 116 BCD size for my crank anymore. :x

Will have to run a 53 - 42 or bin it

ai_1

bails1310 wrote:

Slightly digressing, I was just about to push the button on a new Ultegra chainset from CRC, but noticed a '110mm BoltCircle' option, with no others available.

What does this mean, and is there another option of bolt hole that's just isn't visible that may be better/more suitable?

BCD = Bolt Circle Diameter
It refers to the spacing of the bolts used to attach the chainrings to the spider/crank. If I'm not mistaken there are two current standard BCDs in use 110mm and 130mm. 110mm is always used for compact chainrings. The 130mm is used for some 53/39 chainrings but according to others earlier in this thread Shimano have moved to 110mm for all chainrings including 53/39 on Dura-Ace and Ultegra. I'm no expert so that's about as much as I can tell you. Better check this info is correct for yourself before proceeding.

cyclingDoc

On the latest dura ace 9000 and ultegra 6800 they have indeed gone to just one BCD so you can use standard or compact chainrings on them.