Why Compact?

[winkybiker]

I was in a "fight" with someone on another (non-cycling) forum about the benefits of compact chainring set-ups. She'd advised someone else that a benefit was that you could spend more time in the big ring. I called her on it.

I don't really see that as a benefit (even if it was actually true - surely also depends on the cassette?). My view is that you just want to be in the right gear ratio for the speed you're going, be it on the big ring or small ring. Avoid the "cross-chain" extremes and there you are.

Does anyone here think that (for a given speed and cadence) being in the large chainring is some sort of advantage? Lower friction? Something else?

 

[Master50]

I believe small cogs cause the chain to wrap tighter and have a small increase in chain friction so big cogs don't cause the chain to bend as much. someone has measured it but how significant that is? to use 2 extremes as examples a 12 / 12 or a 53 /53 are the same gear with a 1 to 1 ratio. the 53 53 is the lowest chain loss to friction. Of course neither of those combinations are probable. An MTB might have a 32/32.
In real world we use the gears to match our strength and terrain. who wins your argument?

 

[stutue]

The point of a compact is to give you a spread of gears approaching that of a triple, but sacrificing the top gears that are rarely used.

I believe big rings are more efficient.

 

[avanti]

...............
Avoid the "cross-chain" extremes and there you are.
..................

In my former club there were two big guys who almost always rode their big chain ring even on fairly steep hills resulting in extreme cross chain. A couple of times a year they each broke their chains (they carried a chain tool and rivets to on-ride repairs). I tried to explain they were bending the chain sideways which stresses one side of the chain to a greater extent than the other side and increases friction but to no effect.

 

[stutue]

I expect they wore their chainrings too.

Has anyone else noticed that 36/52 is being offered by Shimano now that their new 4 arm design has the same BCD for all chainring sizes?

Seems a good compromise.

 

[winkybiker]

The point of a compact is to give you a spread of gears approaching that of a triple, but sacrificing the top gears that are rarely used.

I believe big rings are more efficient.

Yeah, the biggest reason for compact is so your low gear is lower than you could reasonably achieve with a 39t up front. At the top end, with 11t rear now common, you don't give up anything compared to a 52 x 12. OK, a 52 x 11 is even higher, but I don't care much about that, really.

With 10 or 11 cogs on the back, gaps between gears are now so small that a wide spread of ratios isn't nearly the compromise it used to be.

I don't know about friction. When in the big ring, your top chain tension is lower for a given power but your bottom chain tension is higher (compared to an identical ratio in the small ring). The big-ring set-up might be slightly lower friction but not by much. Maybe offset by the fact that your big ring isn't as big?

I think the real reason that woman on the other thread liked being in the big ring more often was that it made her FEEL faster.

Neither of my road bikes have compact rings. I only occasionally wish otherwise. I'll put them on for a trip to the Pyrenees (or some such), though.

 

[stutue]

Only my race bike has 53/39. Its light as a feather. Round here you get a lot of 20-25+% hills so the lightness really helps me get away with higher gearing.

I have a Pinarello Ti bike which is pretty nippy but it has a compact on. This gets used for long rides where tired legs mean a steep hill can be a real struggle.

 

[winkybiker]

Only my race bike has 53/39. Its light as a feather. Round here you get a lot of 20-25+% hills so the lightness really helps me get away with higher gearing.

I have a Pinarello Ti bike which is pretty nippy but it has a compact on. This gets used for long rides where tired legs mean a steep hill can be a real struggle.

20% - 25% grades! Christ, where do you live!?

 

[stutue]

In a valley

British road building practice wasnt to ascend via switchbacks, but build the road in a straight line up to the top ....

 

[42x16ss]

I expect they wore their chainrings too.

Has anyone else noticed that 36/52 is being offered by Shimano now that their new 4 arm design has the same BCD for all chainring sizes?

Seems a good compromise.

52/36 is a GREAT compromise. I swapped out my full compact FSA 50/34's for 110 BCD TA 52/36's and never looked back. Not quite as smooth shifting as Shimano but a lot better than SRAM or FSA and nowhere near as soft or fast wearing.

 

[stutue]

Good to hear that. I'll be opting for it next ring change.

 

[Bustedknuckle]

I was in a "fight" with someone on another (non-cycling) forum about the benefits of compact chainring set-ups. She'd advised someone else that a benefit was that you could spend more time in the big ring. I called her on it.

I don't really see that as a benefit (even if it was actually true - surely also depends on the cassette?). My view is that you just want to be in the right gear ratio for the speed you're going, be it on the big ring or small ring. Avoid the "cross-chain" extremes and there you are.

Does anyone here think that (for a given speed and cadence) being in the large chainring is some sort of advantage? Lower friction? Something else?

No..gear ratio is gear ratio..whether big ring and a cog or small ring and a cog...if it's a severe cross chain thing, then you are going to wear stuff out faster but no other 'other'.

 

[Bustedknuckle]

I expect they wore their chainrings too.

Has anyone else noticed that 36/52 is being offered by Shimano now that their new 4 arm design has the same BCD for all chainring sizes?

Seems a good compromise.

Campagnolo also, for about 2 years. 'Mid compact'..

 

[winkybiker]

In a valley

British road building practice wasnt to ascend via switchbacks, but build the road in a straight line up to the top ....

Respect.

Actually, I lived in the UK for a few years and saw some of that. A road up onto the Mendips went up pretty sharp-like, and another one out of the Severn to the plateau at the eastern end of the Cotswolds. I don't think either were 30% though. There were also a couple of steep pitches in Bristol itself.

 

[JayKosta]

Being able to stay on a single front ring makes shifting easier because it avoids the need to make combination front & rear changes.

If the terrain is such that cross-chaining is not needed, then staying in a single front ring is useful because the 'shift pattern' with the rear is simple.

With compact chainrings, the difference between small and large is so much that changing the rear is commonly required when the front is changed.

Compact chainrings (and index shifters) make riding easier for many people.
They avoid the complexity (and weight) of triple-rings, and they retain the wide range of gear options.

The technoloy of index shifting, 'brifters', clipless pedals, and compact gearing has make riding much easier (and safer) for many people. 'Old techonoly' required a much greater amount of 'mechanical' ability and willingness to make riding enjoyable.

Jay Kosta
Endwell NY USAay Kosta
Endwell NY USA

 

[Benotti69]

If it is any use to you to know that Greg LeMond regurlarly rides a triple chainset. Covers all bases.

 

[stutue]

Respect.

Actually, I lived in the UK for a few years and saw some of that. A road up onto the Mendips went up pretty sharp-like, and another one out of the Severn to the plateau at the eastern end of the Cotswolds. I don't think either were 30% though. There were also a couple of steep pitches in Bristol itself.

If you go a bit further south into Devon you'll see some crazy hills by the coast. Nice riding in the Cotswolds though...did you ever ride up to the Somerset Monument?

 

[stutue]

Being able to stay on a single front ring makes shifting easier because it avoids the need to make combination front & rear changes.

If the terrain is such that cross-chaining is not needed, then staying in a single front ring is useful because the 'shift pattern' with the rear is simple.

With compact chainrings, the difference between small and large is so much that changing the rear is commonly required when the front is changed.

Compact chainrings (and index shifters) make riding easier for many people.
They avoid the complexity (and weight) of triple-rings, and they retain the wide range of gear options.

The technoloy of index shifting, 'brifters', clipless pedals, and compact gearing has make riding much easier (and safer) for many people. 'Old techonoly' required a much greater amount of 'mechanical' ability and willingness to make riding enjoyable.

Jay Kosta
Endwell NY USAay Kosta
Endwell NY USA

To be honest.... as soon as rear cassettes started hitting 9 or 10 gears then down tube shifters were dead in the water. Stis were a game changer.....and a long time coming after decades of little innovation and change.

What next I wonder.....

 

[King Boonen]

To be honest.... as soon as rear cassettes started hitting 9 or 10 gears then down tube shifters were dead in the water. Stis were a game changer.....and a long time coming after decades of little innovation and change.

What next I wonder.....

Thread under this one...

 

[stutue]

Road discs are already with us....with or without UCI!

I think the Shimano offerings will stay DI2, so that rules me out for a while.

 

[stutue]

If it is any use to you to know that Greg LeMond regurlarly rides a triple chainset. Covers all bases.

Shhhh

The grown ups are talking

 

[winkybiker]

Being able to stay on a single front ring makes shifting easier because it avoids the need to make combination front & rear changes.


Jay Kosta
Endwell NY USAay Kosta
Endwell NY USA

Interesting, but I don't know I'd necessarily agree. I could say the same about being able to stay on the small ring.The need to shift at the front is more dictated by the range of your cassette, the terrain and your strength. On the small ring, I can actually use all the cogs at the back. The negative effect of cross chaining small-to-small seems much less than the big-to-big cross chaining (which is rough and noisy on most bikes I've ridden).

But you might be right. I actually think I probably do shift more at the front on a regular crankset than on a compact. Front shifts aren't as slick with a compact, though. (EPS/Di2 riders wouldn't notice, I guess)

 

[stutue]

Really, gear choice comes down to rider power and fitness, and bike weight, coupled with how extreme the gradients you ride are.

 

[Aapjes]

Really, gear choice comes down to rider power and fitness, and bike weight, coupled with how extreme the gradients you ride are.

And the preferred cadence.

 

[winkybiker]

And the preferred cadence.

Yep, I agree. It is mostly about how low you want to go for your lowest gear.

I think the "spend more time in the big ring" is a bogus "benefit". Only poseurs need apply.