Stert

whats the difference. obviously the triple has 3 rings. doe the third ring give you a bigger gear or a smaller one. who uses them and why.

and what does compact mean and who would be buying them?

VanceMac

The search function is your friend.

Wiki is usually your best friend (at least for a jumping off point):

Compact crankset
A recent trend is a compromise between the standard road double crankset (with a 39 tooth and a 52 tooth chainrings) and the road triple (with 52, 42, and 30 tooth chainrings). The compact crankset has just two chainrings and a different spider that allows the smaller chainring to have as few as 33 teeth. This provides nearly the same low-end as a triple but without the added weight of a third chainring.

markw

What he said. Compact double lets you still look manly, while enjoying lower gearing for the climbs. I'm old enough now to appreciate a nice triple.

irablumberg

You can get an idea of what each of these looks like by going to the Performance website (or any other online bike shop).

Triples are typically used on touring bikes that may be heavily loaded and by older folks like me with tired knees who need easier gears for climbing hills. A triple these days often has the standard chain rings 53 and 39, plus a "granny" ring which is usually a 30 tooth ring for the extra low gears. Road triples usually use a 130 mm bolt circle for the two big rings (just like a standard double) and a smaller bolt circle for the granny ring (I don't recall the size off hand).

Standard double cranks use a 130 mm bolt circle. This restricts the small ring to being no smaller than 38 teeth. Most standard doubles today ship with 53 and 39 tooth rings.

A compact crank is one that takes 2 chain rings, but uses a 110 mm bolt circle so that it can take rings as small as 33 teeth, although most compacts ship with either a 34 or 36 tooth small ring. Almost all compacts also ship with a 50 tooth big ring. Thus, compared to the standard double, you give up 3 teeth on the big ring. You can do the math yourself to determine how this affects gear inches, but for me, for example, I never pedal fast enough to need more than a 50x12 gear (if I am going faster than 35 MPH, I will always coast ;-)

The advantage of a triple is that it provides the widest range of gears and can be set up so that the middle ring covers a wide range of useful gears, thus requiring use of the big or small rings only occassionally and cutting down on front shifts. The disadvantages of a triple are (1) a bit of added weight; (2) many triples entail a larger Q factor (your feet are farther apart to make room for the extra gear) which some find less comfortable; (3) front shifting is a bit less snappy and precise because of the extra ring and associated hardware compromises; and (4) bike snobs will often sneer at riders using a triple (they feel such riders are not "man enough" to ride a normal double.

The advantage of a compact is that it provides a gear range almost as wide as that of a triple without the small added weight penalty or the reduction in shift performance associated with a triple. Also, for those who already own bikes with standard doubles, the cost of switching to a compact is less than the cost of a triple. Converting to a triple often requires a new front brake/shift lever and almost always requires a new front deraileur and may also require a new bottom bracket (for those without the new outboard BBs). Converting to a compact typically does not require a new front deraileur and does not require a new shifter.

The disadvantages of a compact are: (1) there is a larger gap between the number of teeth on the rings than on a standard double, this leads to two issues (a) you shift rings much more often with a compact than with a standard double and (b) you frequently need to shift both front and rear simultaneously to make the gear switch comfortable; (2) some compacts shift less well than standard doubles, but others are just fine (a compact that shifts really well is the Shimano R700); (3) triples typically give one gear lower and one gear higher than a compact, so if you want/need the extra gear on the top or bottom, the compact won't get you there; (4) bike snobs will often sneer at riders using a compact (they feel such riders are not "man enough" to ride a normal double.

Hope this helps,
Ira

CycleFreakLS

A compact actually allows for a more usable spread of gears. I find that I need less chainring switching to find the gear I want with my FSA 50-34. A 50-34 with an 11-23 has a higher high and lower low than the standard issue 53-39 and 12-25.

FizzyPop

I have 105 9-Speed with a triple and have thought about switching to a double. What kind of options do I have? Can I go to a compact without switching out the FD and RD?

edit: sorry to kinda hijack

Phoible

Why would you want to switch from a triple to a compact double? You won't save that much weight, and the triple gives you more range than any double.

michaelmc

Two reasons:
1. Better/smoother shifting.
2. Tighter gear ratios for better cadence maintenance.

msheron

I like the compact double................nothing about looking manly while having only two rings to me. It's sensible for those who don't have to kill themselves on a double traditional to look manly and so one does not have to worry about shifting twice to get to the small ring like in a triple!

Riding smart beats the hell out of riding dumb!

Little Darwin

I can be convinced of the value of #1...

What is the basis for #2?

If tightness of gearing is the concern a 48/38/28 mountain/touring triple seems to give a lot more gear choices in the usable range than a 50/36 compact double...

michaelmc

The average difference in gear ratio between adjacent gears on the same ring for a 53/39 with a 12-27 cassette is .2160; for a 50/36 with the same cassette is .2212. Standard deviation is approximately the same (.054 vs .056). The percentage difference of average, however, is 6.7%, which is significantly high. With a 50/34, it's even higher, 9.1%.

To rephrase, the average difference in gear ratio between adjacent rings of a 50/36 compact on a 12-27 cassette is 6.7% less (read:tighter) than the average difference in gear ratio of a 53/39 crankset on the same cassette, and the average difference of a 50/34 compact is 9.1% less than that of the 53/39.

Consider, too, that one would probably want to run a 12-25 cassette on the compact, rather than a 12-27. Those ratios of a 50/36 compact with a 12-25 are 13.3% tighter than a 53/39 with a 12-27, and the ratios of a 50/34 with a 12-25 are 15.7% tighter than a 53/39 with a 12-27.

It makes sense. For an ideally low average difference, the chainring should be in the middle of the cassette. So a 17-tooth ring with a 12-27 cassette has an average difference between ratios of adjacent rings of .0874, far less than either examined above. Of course this is unusable in road cycling, but it illustrates the fact that as ring size approaches cassette size, decreasing from the 53/39 standard, the ratios do become tighter. By sticking with a double, we keep the shifting quality sufficiently high.

msheron

Sounds good to me!

michaelmc

One more thing I thought of in the shower: the reasons to not go to a 48/38/28 are that it is, again, a triple, with poorer (even if marginally) shifting. It wouldn't make much sense to go with a 48/38, either, because you're sacrificing much of your top speed (more than a 50/something compact, even). That's fine if you're touring, but most of us are straight road riders, and want some zip. Dropping to a compact lets us have a 50, or 48, big ring, and a small ring that's reasonable for climbing even with a closer-spaced cassette (witness the 12-25 vs 12-27 difference above).

Little Darwin

Nice data for standard double versus compact double... Now, if it only addressed the original question comparing a triple to a compact double...

I agreed with the previous poster that a double shifts better than a triple, I just don't believe that a compact double provides closer gearing than a triple could deliver, if that were the intent of a triple. I actually think most people use a triple for the lower gearing and not closer ratios, but I think the side effect is likely to be smaller gaps between gears... even if many of them would require a double shift.

The statistical analysis is interesting... thanks for sharing!

DrPete 

The "tighter ratio" thing is a myth. Just picking a random gear, going from a 50/15 to a 50/17 is a smaller jump ratio-wise than going from a 53-15 to a 53-17. Sure, if you change out cassettes you can get fewer 2T jumps, but it has nothing to do with the cranks and chainrings.

I will agree, though, that a double, compact or otherwise, is more reliable in terms of shifting, at least in my experience.

But if you want the widest range of gears, smaller gaps between gears, and the lowest possible low gear, get a triple.

michaelmc

If we compare a standard triple (52/39/30) to a 50/34 compact double with 12-27 cassettes, here's what we get:

triple average: .1990
compact average: .2022
difference: triple is 1.6% tighter, though the standard deviation is 4.1% greater.

It's not a huge difference, much less than between standard double and compact double, but indeed the triple is tighter. I wonder how much one would notice the difference in standard deviation (effectively, this means that some differences between adjacent gears are greater and some smaller, and this variation is greater than on the compact by 4.1%). Probably not much, but it's still something to consider.

If one doesn't need the extra high and low gears, I think the compact is still the smarter choice (weight savings, still-tight gear ratios, better shifting), but that said, triples aren't all that bad.

michaelmc

Did you completely miss my numerical analysis of this above, which showed that there is actually a significant difference?

big john

I just got a new Ultegra 10 triple set-up and it shifts great. It shifts better than the 9 speed triple I had before. The thing shifts so good, I don't see how you could complain about it at all.

bigbossman 

+1.

My Ultegra triple shifts very well, and I know lots of folks that complain about how crappy their compact double shifts because of the large tooth difference between the rings. Besides - with a triple, you're in the middle or outer chainring most of the time, and shifting between those two is very smooth.

I think the "triples shift poorly" mantra is hooey.

A compact crank is a compromise, and almost but not quite as good as a triple. If you live in a flat area or race, a double (compact or otherwise) makes sense.

Basscycle

Same here but, what I'm finding is that the 50 combined the 12-25 10 speed provides more than enough gears so that I hardly ever have to go to the 34.

FizzyPop

Weight saving didnt enter my mind. Smoother shifting that others alluded to, did. Where I live there are too many climbs for me to use a straight double. A compact double gives me better options for lower gears. Also, if I slack off and dont ride for a couple of weeks, I wont kill myself like i would with the straight double For me, the range of the triple isnt that useful, I find myself not using alot of gears and am willing to sacrifice that in order to get smoother shifting.

So, with my 105 9-Speed Triple, what are my options for switching to a compact?

bbattle

Gear chart using MPH @ 90 RPM
For 700 X 23 / 23-622 tire with 170 mm cranks
With 10-speed 12-13-14-15-16-17-19-21-23-25 Cassette

52-39-30 triple



Gear chart using MPH @ 90 RPM
For 700 X 23 / 23-622 tire with 170 mm cranks
With 10-speed 12-13-14-15-16-17-19-21-23-25 Cassette

50-34 compact

You can of course see what a traditional double looks like by ignoring the small ring of the triple. Compact gives up 1.2mph on the high side but gains two lower gears over the double. The triple gives you another gear or so on the low end over the compact.

A case made for the compact: https://www.slowtwitch.com/mainheadin...r/gearing.html

Nobody says a compact must have nothing bigger than a 50T chainring, either. https://sheldonbrown.com/harris/chainrings/110.html

irablumberg

If you have the Shimano outboard bottom bracket, your easiest choice is the Shimano R700 crank. It should fit the bottom bracket. You would likely need to remove a few chain links to account for the switch from a 53 tooth to a 50 tooth big ring. No other hardware would be required. You would need to move your front der. down a bit also due to the smaller big ring and re-adjust your front der. stops to deal with having only 2 rings instead of 3. You might want to get a new front der. designed for a double, but you can wait and see how your triple front der. works first.

If you don't have an outboard bottom bracket, you likely have an Octalink bottom bracket axle, in which case you could purchase the Ritchey WCS compact or new carbon compact. You would also likely need a shorter bottom bracket axle since the triple bottom bracket axle is longer than the axle for a double.

Ira

ks1g

Disclaimer: I have Ultegra 9 speed triple on my bike and have been thinking about this as well. This is based on a lot of reading but no 1st-hand experience. You need a new crank and probably a new bottom bracket. I've seen a few compact cranks (I think Ritchey makes one) that work with the Octalink spindle. But make sure it's the right Octalink - there's a V1 and V2 and I don't recall which one 105 9speed uses or which one the Ritchey uses. Your chainline will be off (spindle on the triple BB is too long) but it *might* work. Your rear derailluer has enough range to handle the 16 tooth difference up front. You will have to adjust the upper and lower limits on the front deralluer and probbably lower it a little as the 50 tooth chainring is slightly smaller than the 52 or 53 you have now. The front brifter will work but you'll have 2 "trim" positions between high and low.

There's a good chance you will need to replace the BB as well, though.

OTOH, why bother? A properly adjusted triple will shift quite well and as I'm not racing crits, I don't need lightning fast shift response up front. Check the Parktool website for excellent step-by-step instructions on front derailluer adjustment.

Basscycle

How do those numbers change w/172.5 cranks?