change a triple to compact

[MacB]

Good observations well said MacB. I wonder if you meant having a 11-25 block rather than 12-25 cassette?

.

I did actually mean 12-25 cassette, but that's just me and the exact makeup would depend on the rider. A lot of these musings are based on my experience of a 30/42/52 with 12-26 cassette.....apart from checking it worked I never used the 52t ring. But I'm a bit of a chicken where downhill and speed are concerned, group rides generally see all and sundry passing me on the way down....if I've not handily placed myself at the back to begin with.

But I agree with your assessment that an 11t does open options up quite a bit. Funnily enough I've now moved to triple from my homemade super compact, but only because I had moved to STIs. Though the triple is 24/36/46 currently with an 11-28 but I have a 12-25 waiting in the wings.

 

[RecordAceFromNew]

+1, sigh, and with freewheels one can't have cogs smaller than 13T, iirc.

Just for completeness, and as we remember those 52/42 chainset everybody had, a 52/13 is no different to a 44/11, and the only way to go fast with them was to spin!

 

[zigzag]

my commute is very dynamic, stop and go, traffic, 27 lights etc. my speed changes very often, so for me it's very handy to have bigger gaps between gears. i usually start in 59" gear, spin out standing, sit down, two clicks up and i cruise in 79" gear at 20-22mph. if i need to stop, then i press front brake, push gear leaver for two gears down (one longer push) while braking and i'm in my preferred 59"gear in no time ready for another start.

i agree about the advantages of other systems (double, compact, triple, hub gears, fixed etc.), but everyone chooses what works best for them (if they are knowledgeable and care enough to choose, that is).

 

[yello]

I really like the way this thread has progressed. WAY more interesting than my original question!

 

[asterix]

On my rather windy, hilly sportive I was using a slightly lower bottom gear than usual. My main problem was not the gearing but my leg muscles. They were strong enough to get me up all the hills but I couldn't get the speed up. Lack of practice at that sort of ride which no change of gear range or configuration would have fixed. I need to get out more!

 

[alecstilleyedye]

I really like the way this thread has progressed. WAY more interesting than my original question!

all i can say is that jimboalee isn't here to further murk the waters

 

[Ian H]

As above, people who complain of the 'big jumps' seem to forget the terrain required a 'jump' in gears to keep the momentum. An example is if I am approaching an incline, say a short 7% hill, then knocking down one cog at the rear wont make any difference. I tend to drop down a few so if I had this close ratio it would only be getting bypassed for the preferred gear.

Eh?

 

[Garz]

Eh?

Eh to the eh?

 

[MacB]

Eh?

he means that he can often hit terrain where he needs to shift more than one cog at a time so bigger spaces might be easier for that type of riding.

I suppose, for some, the ultimate would be a sort of loss free CVT(continuous variable transmission) but, as it stands, a close ratio cassette and STI/Ergo/Double Tap shifting is the best in that direction. There is the Nuvinci CVT hub but, though admitting they do know them, they steadfastly refuse to publish transmission efficiency data. Which leads one to suspect that the losses are scarily large compared to other hub gears and even more so compared to derailleur systems.

But you can see a 'hybrid' solution coming up, the Dura Ace Di2, some sort of power tap and the ability to program in a power level or tempo, or something. Then off you go and the bike handles the gear changes keeping you at the workrate you desire.

There is a much cheaper version of this already available, it's called singlespeed, I suppose you could count fixed as well

 

[BigTone0777]

Though the triple is 24/36/46 currently with an 11-28 but I have a 12-25 waiting in the wings.

This sounds like the ideal setup for me, nice close ratio with the 12-25 and plenty of options with the 24/36/46. Like you I'm not so "bothered" about blistering decents lol

 

[Ian H]

he means that he can often hit terrain where he needs to shift more than one cog at a time so bigger spaces might be easier for that type of riding.

Well, yes. But I don't see how occasionally needing to shift more than one gear obviates the usefulness of close ratio gears.

There is a much cheaper version of this already available, it's called singlespeed, I suppose you could count fixed as well

Very true. I do a bit of fixed riding myself, including one Paris-Brest.

 

[BigTone0777]

Well, yes. But I don't see how occasionally needing to shift more than one gear obviates the usefulness of close ratio gears.


It's personal preference, what suits 1 rider isn't going to always suit the next

 

[brockers]

they steadfastly refuse to publish transmission efficiency data. Which leads one to suspect that the losses are scarily large compared to other hub gears and even more so compared to derailleur systems.

As a matter of interest, does anybody have rough figures for efficiency losses for derailleur and hub systems compared to fixed or free?

 

[zigzag]

As a matter of interest, does anybody have rough figures for efficiency losses for derailleur and hub systems compared to fixed or free?

in my experience hub gears have "noticeable" drag, derailleur setups "little" drag and fixed/free no drag. it's hard to draw exact numbers as there are many variables - types of gear hubs and individual gears in them, bearings in derailleur jockeys etc.

 

[MacB]

There's loss in any system, you would expect the least from fixed, then SS, then derailleur and finally hub gear. As far as my reading has taken me then they all exceed 90% efficiency, though there are claims around the Rohloff in particular being less efficient in certain gears. But I'd take those with a pinch of salt as I think there's a lot of 'hate' for the Rohloff because it's expensive and German.

The most common sort of numbers I've seen are around the 99% mark for fixed/SS, 97% for a derailleur(clean and decent spec) and 93/94% for hub gears, the better ones. Rohloff claim 95-99% depending on which gear but I don't think anyone but Rohloff quite believes those numbers.

If your derailleur is all clagged up, poor chainline, or another issue, I have no idea what sort of increase that would make to losses. For example a lot of MTBers running hub gears claim that, by the end of a run, their gearing is more efficient than their friends derailleurs...but that's purely anecdotal. If you look after a derailleur system then I doubt the difference between that and fixed/SS is enough to bother with, say 1-2%. The 'drag' from hub gears will bother some and not others - I generally work on assumption that I'm losing 3% against a derailleur in ok nick.