What is a "compact" chainset

iamisotope

Can anyone explain to me what is meant by compact, in clear and simple terms?

fat lad in lycra

2 rings on front....one is big one is really small....the compact helps you to get up hills

Pseudonym

'compact' is typically 50/34 gearing, as opposed to 52/39 for a 'standard' chainset.

rake

if you look at the bolt holes on the so called spider that bolt the chain rings on, you should notice that you cant put a chainring on that has bolt holes of a smaller diameter. this limits how small an inside ring you can fix on there, which on a standard chainset is a 39 tooth ring. but this may not be small enough for steep hills. a compact crankset has a smaller diameter bolt hole radius (pcd pitch circle diameter) of 110mm enabling you to put say a 34tooth chain ring on there. everything else is the same.

Monty Dog

Double chainset with inner chainring of 34 or 36 teeth and typically matched with a 50 tooth outer.

Cleat Eastwood

All of the above and...

The purpose of a compact is to offer a similar range of lower gear ratios (the ones that make it easy to climb) to a triple but without the added weight of a third ring/triple shifters etc.

Wacky Racer

Agree with all of the above. Very few OTP bikes are being fitted with triples now, and most bike shops I have spoken with claim that the number of customers buying triples is falling all the time, and is now at around 10% tops. Those who are buying triples tend to be "old school" riders who don't want to change. With a compact you do lose a few gears, and when changing on the front rings you do need to change twice sometimes to get the right gear, but you get used to it. If you are more unfit and struggle on climbs, or if you regularly have very steep climbs you may wish to use a triple, but I reckon a compact will suffice the vast majority. Plus you save a bit of weight. I dare say some people will disagree with some of my comments and tell you why you might need a triple, I can only give you my opinion.

I asked this question before I bought my new road bike, and I'm glad I went for the compact, it climbs all the hills I need it to and more.

Berk Bonebonce

Wacky Racer wrote:

With a compact you do lose a few gears, and when changing on the front rings you do need to change twice sometimes to get the right gear, but you get used to it. .

Summed compacts up nicely: They almost give you the range of a triple but with so few gears you spend a lot of time on your buike trying to find the right gear.

But ... according to the above, you do get used to not being able to find the right gear.

rolf_f

Berk Bonebonce wrote:

Summed compacts up nicely: They almost give you the range of a triple but with so few gears you spend a lot of time on your buike trying to find the right gear.

But ... according to the above, you do get used to not being able to find the right gear.

You've never ridden a compact have you? Basically, for example, drop down on the chainring and up one on the sprocket and that's all you need to do. Generally works perfectly well. It's not hard

Wacky Racer

Summed compacts up nicely: They almost give you the range of a triple but with so few gears you spend a lot of time on your buike trying to find the right gear.

But ... according to the above, you do get used to not being able to find the right gear.

This is off the mark, and definitely not what I said. As the poster above says, the "double change" is easily completed with a change at the front and the back. It becomes second nature very quickly, it took me my first ride out to get used to it, and I wouldn't swap back to a triple.

desweller

Berk Bonebonce wrote:

Wacky Racer wrote:

With a compact you do lose a few gears, and when changing on the front rings you do need to change twice sometimes to get the right gear, but you get used to it. .

Summed compacts up nicely: They almost give you the range of a triple but with so few gears you spend a lot of time on your buike trying to find the right gear.

But ... according to the above, you do get used to not being able to find the right gear.

I'm with BB on this. My old triple allowed me to have close ratios and a wide gear range. With my compact I am stuck with either one or the other, and with three or four 1-in-4 climbs in my local vicinity it is an annoyance not being able to use a comfortable cadence.

CRAIGO5000

I agree with the double vs triple. I went from a triple to a double and soon found that a double shift was required in some instances to select the required ratio. It became second nature in around 5 mins of riding.

Triples to me look really over complicated now and I never used the granny ring to start with so it was pointless having it really.

The old school rider as mentioned above is probably of the school of "more is best". Most triple riders on here even say "I don't really ever use the granny ring but it's nice to know it's there should I need it"

When I was a kid, more gears on your bike = more kudos, I'm a grown up now though.

John.T

The triple usually gives you one higher gear and one lower gear with a lot more duplicated ones in between. Whether you find this easier to use or not depends on how you use your gears. The now more common triple 50/40/30 with a 12/27 gives one lower gear and no higher ones. It does cover up for not having an 18 sprocket. Using it with a 12/23 gives more duplicated gears and no lower one. The only downside I have found with a compact is you cross chain more. (and there is no 74" gear other than 34/12)

niblue

I've had road bikes with triples, compact and normal chainsets in the past but based on my experience I can't see me ever using anything other than a compact again (although I'd consider a triple on a tourer). The missing gears is a total non issue for me, and I occasionally change rear cassettes to reflect the sort of riding I'm doing (my Roubaix currently sports an 11:32 and a mountain bike mech as I'm thinking about my first 100 mile day soon and wanted a low gear for near the end of the ride when I'm knackered).

Normal for me is a 20 speed set-up with a compact up front and an 11:28 on the back, and that works great pretty much everywhere.

oldwelshman

As I posted before I use compact to race and use 11 straight through on the back. Not sure where al; the lost gears quoted com from, must be using a different mthod to calulate than I do
I only ever do one double shift if I get to a steep hiill in a race but this is no problem.

greasedscotsman

Cleat Eastwood wrote:

All of the above and...

The purpose of a compact is to offer a similar range of lower gear ratios (the ones that make it easy to climb) to a triple but without the added weight of a third ring/triple shifters etc.

I thought a compact was for people who weren't strong enough for a standard chainset!

oldwelshman

greasedscotsman wrote:

Cleat Eastwood wrote:

All of the above and...

The purpose of a compact is to offer a similar range of lower gear ratios (the ones that make it easy to climb) to a triple but without the added weight of a third ring/triple shifters etc.

I thought a compact was for people who weren't strong enough for a standard chainset!

Is yours a 42/52 then ?

greasedscotsman

oldwelshman wrote:

Is yours a 42/52 then ?

Nope, 53/39/30 :oops:

dave_mallard

greasedscotsman wrote:

Cleat Eastwood wrote:

All of the above and...

The purpose of a compact is to offer a similar range of lower gear ratios (the ones that make it easy to climb) to a triple but without the added weight of a third ring/triple shifters etc.

I thought a compact was for people who weren't strong enough for a standard chainset!

Agreed - I use a 50/34 and 12-24 on my commuter road bike. It's all you need for busy roads with some smallish hills. Currently building a touring bike with 44/32/22 and 11-34......gonna be carrying a lot of gear for 12 months cycling though so I guess that's acceptable :oops:

Mikey23

When I were a nipper a sturmey archer 3 speed was state of the art. I think the gear ratios were small, medium and large...

rick_chasey

Similarly I ride a standard and thus will be fitting a 12-30 cassette on my bike when I go ride the Tour of Flanders.

Pross

Anyone else find it odd when a thread comes back from the dead with no real reason? You read back through and think 'haven't seen them post in ages' then realise it is 3 years old!

zx6man

I will answer in Jan 2017....

greasedscotsman

Pross wrote:

Anyone else find it odd when a thread comes back from the dead with no real reason? You read back through and think 'haven't seen them post in ages' then realise it is 3 years old!

Or you read through it and wonder what idiot posted that comment. And it was you! :oops:

(I mean myself there Pross, not you, obviously...)

TheLoneCyclist

How have I only seen a mention of the BCD once?

Standard= 130mm
Compact= 110mm to accommodate smaller rings due to less teeth

Manc33

Triple inner is 74 BCD don't forget. :P

I kept looking for old Dura-Ace shifters in 8-speed with a triple left shifter and they are nearly impossible to find.

One day... because its still probably cheaper and arguably better to do that than go full cheap to mid range 10 or 11 speed, costing a fortune and ending up with shifters way inferior to DA.