what are the benefits of a compact chainset?

Karl72

Hi,
I am just wandering what benefits I would get if i got my chainset upgraded to a compact chainset. My current set up is 39/53 front & 12/27 rearwhich was the original that came with the bike, If i upgraded to a 34/50 front & 12/25 rear would i get any advantages/disadvantages with this set up?
Cheers

Karl

siobhansdad

I went from a 53/39 to a 50/34 just to avoid changing the chainset for the mountains as I realy do need a 34 on them

I had some problems with my new compact after a few weeks and put the 53/39 back on

For day to day riding I much prefer this

I find on the compact I tended to stay on the 50 ring which led to groin strain as riding on the 34 is too low for me genarally

I think the 50/34 is great for mountainous rides but not all the time , I guess it depends if you do not mind swapping as the need arises

Very personal , though, try one out before you buy if you can

redddraggon

I'm currently using a 50/36 (not34) compact with a 12-23 rear, Would I notice much difference going to a 53/39 with a 12-27 rear?

maddog 2

you can change the rings you know

just because it comes with 34/50 doesn't mean you have to stick with it

36/50

34/48

36/48

hell you could run 38/52 if you wanted.

Compact just gives you more flexibility than standard, in terms of the low gears.
And a tad less weight.

wildmoustache

reddragon/karl 72

one of my bikes has 53/39 and 12-27 on it ... the standard shimano climbers' set-up.

the other one has 50/36 and 11-25 on it (campag).

I far prefer the latter, and can't really see any argument in favour of the former. Unless you are more or less only going to ride in flat areas, I don't see why amateurs would be better off with 53/39 for their road bikes (TT is different, but you wouldn't want 12-27 there...)

Advantages of 50/36 with 11-25:

Overlaps in both directions compared to 53/39 with 12-27 (lower lower gear, higher higher gear)

Smooth changes between front chainrings compared to 50/34, and also less shifting at the back required when you shift at the front.

Allows for much more time to be spent in the big ring. 50 tooth big ring allows you to get up some climbs that you'd never manage on a 53.

Lighter

It all depends on how strong you are and where you're riding etc., but i've used this set-up in sportifs (including etape and gran fondos), club rides, and even triathlons (50x11 is still a big old gear, if not enough for all TTs).

Give it a try!

John.T

Karl. There is no point in going compact and then changing from 12/27 to 12/25. You loose nearly all of the low gear gain. Stay with the 27. I run 50/34 with 12/27 for everything except racing when I use a 12/23 for closer ratios. If I was fitter I would go to an 11 cog. I have found that with the compact set up I use nearly all the gear combinations at some time. On flatter rides I tend to stay on the big ring while in more hilly areas I use the small one much more. Most of my riding is done on 34 - 13 to 15 or 50 - 19 and 21. These ratios overlap so I base the ring used on which way I am most likely to change gears. With 53/39 I hardly ever used the 53 ring. I just wore out the 39 ring and the 15 and 16 cogs.
The compact is not a perfect solution but if you need lower gearing then it is a good option.
Have a play on this site to compare gear ratios. http://sheldonbrown.com/gears/

maddog 2

I run 34/48 and a 12-25 and use the 48 for everything except proper hills.

I don't miss the top end - proper top speed is a function of the hill anyway. I've hit 60 coming off various hills so it's irrelevant.

As you say John, on 39/53 you just wear out the 39 ring, without the benefit of any really low gears.

I look at it this way, imagine we all used compacts and someine came along and said "here, look at this 39/53 chainset..." No decent low gears and loads of high ones, which you'll use only occasionally, and when you're going downhill anyway.

"D'ya think it'll selll?"

peanut

this is a facinating topic for me . I spend hours working out imaginary gearing solutions for my bikes and rides.
I find it really useful to draw up a full gear table of all the possible ooptions I am likely to use and then I can see the benefits in inches at every combination. This has the added advantage of showing up any potential problems for front ring changing. Some of the jumps shown in red are large ie 22-23" which is not ideal but is ok if you don't spend a lot of time shifting between the two front rings when you are riding .

The bigger the jump in inches at the front the more you will need to immediately adjust the smaller sprockets to compensate. not ideal .

I use a 38t with a 53 and an 8spd 11-25t which gives me a huge range . The terrain where I live range from long straights and downhills to numerous short steep climbs. I am just about to upgrade to 10spd and will probably go with 11-25t giving me a smoother transission
http://i130.photobucket.com/albums/p261 ... rtable.jpg

Garry71

redddraggon wrote:

I'm currently using a 50/36 (not34) compact with a 12-23 rear,...

Is that what came with your Carrera Virtuoso? I've got the same bike, but I haven't counted the teeth on it yet.

Thanks
Garry

aracer

maddog 2 wrote:

I don't miss the top end - proper top speed is a function of the hill anyway. I've hit 60 coming off various hills so it's irrelevant.

As you say John, on 39/53 you just wear out the 39 ring, without the benefit of any really low gears.

Like all things, YMMV. Personally with a 53/39 I spend most of my time in the 53. Having said that I'm getting a compact, as I like the idea of being able to have close ratios yet still having that low bail out gear for the steep climbs they like to put on sportifs (might mean I'd ride the really steep ones round here more often too).

Proper top speed might be a function of the hill, but personally I can go faster down some less steep hills with a 53/12 than with a 53/13 (would go even slower tucking and coasting), hence I've got an 11 sprocket to go with my compact!

redddraggon

Garry71 wrote:

redddraggon wrote:

I'm currently using a 50/36 (not34) compact with a 12-23 rear,...

Is that what came with your Carrera Virtuoso? I've got the same bike, but I haven't counted the teeth on it yet.

Thanks
Garry

Yeh, it is, I haven't counted either though, it's what the Specs say on the internet say, so I could be saying a load of rubbish that its a 36

bahzob

Triple is the way to go. 53/39/30 on front, 11-23 on the back for me (12-27 if you want to be certain to get up every hill without getting off).

(53x11 is not used often but when it is (on long gradual descents usually) it's a lot of fun)

hamstercp

I agree, but run 30/39/48 with a 12-23 as:
a) I'm only 5'7" and cannot push a bigger ring round (and 48-12 is the same as 52-13 anyway)
b) You can just get away with a short cage rear mech (Campag setup)

The bottom gear is slightly lower than a 34-25 setup, but the big advantage is that there are no horrible jumps when shifting the rings - 34 to 50 is a big jump that interrupts my flow, and the cassette is again a closely spaced one.

..and if you feel really prissy you can take the inner ring off except when you hit the hills!

wildmoustache

hamstercp wrote:

I agree, but run 30/39/48 with a 12-23 as:
a) I'm only 5'7" and cannot push a bigger ring round (and 48-12 is the same as 52-13 anyway)
b) You can just get away with a short cage rear mech (Campag setup)

The bottom gear is slightly lower than a 34-25 setup, but the big advantage is that there are no horrible jumps when shifting the rings - 34 to 50 is a big jump that interrupts my flow, and the cassette is again a closely spaced one.

..and if you feel really prissy you can take the inner ring off except when you hit the hills!

you're right on the big jumps with 34-50, and the solution is 36-50 or even 34-48! If you mate that to a 12-27 at the back, or even a 29 if you're on campag, then you have some pretty low gears available.

i've always found triples don't shift very smoothly, are harder to index and clean and maintain. And they're heavier!

hamstercp

I'd agree with that, the problem is that I'm on pre 2001 Campag stuff and longer cage mechs are extremely hard to find secondhand (post 2001 shifters don't pull the right amount of cable - so the indexing is squiffy)

However I don't tlike the jumps of a wider spaced cassette. For me the best option if I ever wanted a real crawler gear is to fit a smaller inner chainring - down to 24T fits.

Eat My Dust

I changed from a 53/39 to a triple (not sure of the ratio) but I couldn't get used to all the changing on the front rings, I then changed to a 50/34 compact which I find a lot more comfortable, although I miss the 53 on some downhill bits, but I can still hit 40mph, so it's not that big a deal.

Steven Martin

I think the main benefit is the closer spacing on the lower gearing when using the compact.

ie The jump from 34-23 to 34-25 is smoother than 39-24 to 39-27, the change in cadence for the former is just over 8, and for the latter it is just under 11 at 20km/h.
(If you have a custom cassette this is irrelevant).

In repsonse to the gear combos that suit, you can look at some cadence calculators online to determine if your selection will be suitable.

eg 40 km/h at c100 cadence would put you on 50-17 (94 cadence) or 50-19 (106 cadence) or 53-19 (100 cadence).

Note that 34-25 is a slightly smaller gear than a 39-27 (36 vs 38 inches).

stuxmann

hi to all...i have a standard double 53/39 chainset with 11-25 cassette. Having tried my mates compact (50/34 12-27) i know this is where i want to be, having found the hills so much easier. My question is can I just change the chainrings without having to change everything else?? ( i will leave the rear cassette 11-25 for now)..it may be a stupid question but i really have no idea whether its as easy as just buying 2 new chainrings, or if problems arise with this. i appreciate the chain may have to be altered or a new one bought but does anything have to be compatible in some way or will most chainrings for the same make i have be ok?, many thanks for your advice

wildmoustache

stuxmann wrote:

hi to all...i have a standard double 53/39 chainset with 11-25 cassette. Having tried my mates compact (50/34 12-27) i know this is where i want to be, having found the hills so much easier. My question is can I just change the chainrings without having to change everything else?? ( i will leave the rear cassette 11-25 for now)..it may be a stupid question but i really have no idea whether its as easy as just buying 2 new chainrings, or if problems arise with this. i appreciate the chain may have to be altered or a new one bought but does anything have to be compatible in some way or will most chainrings for the same make i have be ok?, many thanks for your advice

afraid not. The issue is the "Bolt Circle Diameter" ... i.e. the diameter of the circle of bolts that bolt your crank arms to your chainrings. On a compact this diameter is smaller than on a 53-39. You have to change the cranks also if you want to fit a compact, and depending on make also the bottom bracket.

Cost and convenience wise I'd recommend buying a chainset. The shimano ones are great value for money (start at about £35 ex. BB), if a little heavy. Campag are lovely but more expensive (will work with shimano gears and chains fine.

hamstercp

Sadly probably not.

The min size of rings for a Shimano is 38, for Campagnolo 39. This is because the bolt holes are too far apart and th ring would be smaller than the circle of bolt holes.

You will need a smaller crankset spider, bolt circle 110mm (called a Compact)

Garybee

peanut wrote:

this is a facinating topic for me . I spend hours working out imaginary gearing solutions for my bikes and rides.

C'mon, less maths, more pedaling. That way you may arrive at a hill you didn't know about with a 42/23 bottom gear, but all that extra training will mean you'll rocket up it.

McBain_v1

I have just put a 34/50 Shimano compact chainset onto my winter bike (Olmo Giro ChrMo frame - very heavy) and it has really made a difference to my enjoyment of riding this bike. Having developed a slight problem with my left knee I found that the lower gearing really helped me to pootle along. I have no problem with keeping a cadence of about 95rpm to drifting along in the small ring.

Having swapped from a classic 52/42 set up I thought that I might get caught out when changing from the big ring to the little one, but you don't, once you know you are likely to have to pedal a bit faster I find that you just automatically do.

I have a 12/25 cassette (8spd) on the back and haven't had any problems with ghost shifting or the like. I need to adjust the front derailleur to eliminate a bit of chain rub when in bottom gear, but other than that it has been problem free and has added a lot to my enjoyment.

If you have a heavy bike, go compact

Smokin Joe

Both my bikes run compacts, 48/34 and 50/36. I would never advise anyone to get 50/34, I absolutely hated it. The jump between rings is savage, you go from grinding to spinning like a nutter everytime you change down. Keep the smaller jump between the rings and fit a larger sprocket at the back if you need a low gear. Big jumps between ratios don't matter at that end of the cassette.

dennisn

I switched to a compact because I needed a new crankset. 50X34 & 11X21 suit me just
fine here in the flatlands although I may go to a 50X36. If I do go on a climbing tour
I switch to a 50X33 & 12X27. Works for me.

Dennis Noward