Chainsets

get on your bike

why are all new bikes fitted with compact chainsets these days. I Hav a standard one and thinking of changing to compact for a very hilly 200 k in June. Would I be best of sticking to my standard and if I did change would I go slower as top gearing is lower. Appreciate your thoughts as I wrecking my head a bit

Cheers

Ollieda

shouldn't the big ring be the same as the big ring on a double? I always thought that the difference in a compact was that the small ring was a mid way between your normal small on a double and a small on a tripple?

Never really paid enough attention, hence I'm always struggling towards the top on my double!

desweller

Compact will be ~50/34 and a double is ~53/40. A lot depends on your cassette.

get on your bike

Think my cassette is 24 12. Would it make a big difference changing to 28 one

Chrissz

DesWeller wrote:

Compact will be ~50/34 and a double is ~53/40. A lot depends on your cassette.

or 53/39

desweller

Chrissz wrote:

DesWeller wrote:

Compact will be ~50/34 and a double is ~53/40. A lot depends on your cassette.

or 53/39

'~' means approximately ;-)

Yossie

And whats the score with compact frames? I've never been able to understand the rationale behind them - any enlightenment on both of the above very welcome.

Pross

You won't go slower with a compact despite what some people will tell you about "spinning out" on 50 x 11 when what they really mean is they can't pedal fast enough, the difference between that and 53 x 11 isn't great and 50 x 11 is a bigger gear than 53 x 12. I think a lot of new bikes are aimed at the sportive market hence the lower gearing.

As for compact frames, I think it just means the main triangle is smaller as a result of the seat tube extending above the top tube (not a great explanation sorry). I assume the idea is that it makes the frame stiffer and as there is slightly less frame it should also be lighter.

get on your bike

Good explanation. I'm going to keep the standard and get a 28 11 cassette should do the job nicely. Although I do like the look of the ultegra one

daviesee

I have a 11/25 at the back (although on a 50/34 at the front) and if I was going for a lower gearing for climbing I would go for a 28(27)/12 and lose the 11 to keep the gears closer.
I think I would rather spin out (unlikely - that's coasting time 8) ) than be jumping between gears to find a "nice" ratio going uphill. Just my tuppence

jedster

I assume the idea is that it makes the frame stiffer and as there is slightly less frame it should also be lighter.

Being a tad cynical here, I reckon the main driver behind compact frames is to allow a wider range of saddle heights and so cover the whole size range with fewer frame sizes - reduces stocks and costs for manufacturers and retailers...

Oh and also fashion - the compact design came from MTB.

Stiffness and weight are the excuses that they use!

redrobbo

jedster wrote:

I assume the idea is that it makes the frame stiffer and as there is slightly less frame it should also be lighter.

Being a tad cynical here, I reckon the main driver behind compact frames is to allow a wider range of saddle heights and so cover the whole size range with fewer frame sizes - reduces stocks and costs for manufacturers and retailers...

Oh and also fashion - the compact design came from MTB.

Stiffness and weight are the excuses that they use!

You could well be right, altho I have a custom compact frame from a few years ago and it makes me look like a much better grimpeur than I really am. I love the way the frame has hardly any BB flex unlike its predecessor, a standard frame that used to bend quite a bit in that way. MTB technology indeed.

Slack

get on your bike wrote:

why are all new bikes fitted with compact chainsets these days. I Hav a standard one and thinking of changing to compact for a very hilly 200 k in June. Would I be best of sticking to my standard and if I did change would I go slower as top gearing is lower. Appreciate your thoughts as I wrecking my head a bit

Cheers

In respect of speed, no, you would not go alot slower. For example I have a std double, most other club riders have compacts, and there is no virtually difference in real world speeds.

I'm talking about Dartmoor here, where it's not unusual to amass 5000ft plus of climbing within 60 miles.

My bottom gear is 39x27. When riding beside mates with 34x27 they are much more relaxed and seated, whilst I'm out of the saddle and mashing. Out of saddle equates to higher heart rate, thus more energy useage. Mashing takes more of the legs than spinning lightly!

The compacts give the advantage of using a lighter gear/higher cadence on the steeper and longer hills, thus when climbing, you use more aerobic power and less muslce power, ergo less energy. I suffer with a std chainset on the longer rides (70miles plus) when there are several stiff long climbs.

I have 12-27 cassette, and the gap between ratios is acceptable. I think the ratio spread of a 11-28 would be awful. If I could afford to buy a compact chainset, I would.

dgstewart

I have the SRAM 11-28 cassette on my Tarmac, with 53/39 up front and it's not that big a difference. You're only losing one extra bottom gear vs. the compact. Granted on very steep hills (say 10%+ to 15%+, depending on length) then you might want lower, but in "normal" use it makes no difference whatsoever - you just find the right gear.

The 11-28 cassette does have some larger gaps, but again it's no big deal to me. Either spin a (little) bit faster or push a (little) bit harder. I've not yet managed to understand why some people seem overly concerned at not getting just the "perfect" gear at all times - the way some people go on I bet they would like 1/2 tooth increments if possible! I've never found a road that doesn't change gradient a bit very few 100 yds anyway, so you can't always be in the "perfect" gear.

stonehouse

A lot of it will come down to the terrain you are riding over. If you have gradients over 12-15% to deal with, especially if they are not short hills you will be happy to have gearing that will help you spin up the grade.

I struggled for my first year with a 53/39 12/25 thinking that I'd get stronger and cope, all I did was destroy my knees, something I now have to live with.

I now ride with 50/34 28/11 and although yes, the gear gaps are less than ideal on the flat, I can get up the hills without hurting my knees, and, as a result am getting stronger. I might entertain say a 27/12 later in the year, but will keep the 50/34. A younger stronger rider will no doubt have a different take on things though......

simonaspinall

stonehouse wrote:

A lot of it will come down to the terrain you are riding over. If you have gradients over 12-15% to deal with, especially if they are not short hills you will be happy to have gearing that will help you spin up the grade.

I struggled for my first year with a 53/39 12/25 thinking that I'd get stronger and cope, all I did was destroy my knees, something I now have to live with.

I now ride with 50/34 28/11 and although yes, the gear gaps are less than ideal on the flat, I can get up the hills without hurting my knees, and, as a result am getting stronger. I might entertain say a 27/12 later in the year, but will keep the 50/34. A younger stronger rider will no doubt have a different take on things though......

I'd agree with the comments on the flat - I find a 39T ring a great 'cruising' gear - I'd top out too quickly with the 34T and the 42T was a tad too big. Do those who use the compact set-up tend to find themselves going to the 50T when on the flat?

daviesee

simonaspinall wrote:

Do those who use the compact set-up tend to find themselves going to the 50T when on the flat?

On the flat with no headwind and feeling good then I will probably be on the 50 and somewhere around 13 at the back. Unless I want to go fast.
I am quite often on 50/11 on the flat. Living in a hilly area it depends on whether I have come down a hill (50/11) or preparing to go up a hill (50/13).

Did that make any sense? :?

rake

unless climbing i ride on the 50 at all times. anything lower than 17t and im not trying.

Mike67

Mine's a triple

(Start watch and see how long it takes to be called a wuss )

desweller

Mike67 wrote:

Mine's a triple

(Start watch and see how long it takes to be called a wuss )

I'm not gonna do it. After passing a pile of riders ascending things like Bushcombe Lane and Symonds Yat Rock I have to say, I Love My Triple!

Of course, all those riders then pass me on the flat bits.

petemadoc

I have a compact 50/34 with an 11-28 cassette

On the flat I'm always on the big ring (50) at the front unless there's a nasty headwind. Not sure what I'm on at the back but I think it's the 4th cog from the biggest (if that makes sense), usually travelling between 18-21mph

@ Daviesee I don't know how anyone can use 50 - 11 on the flat. You're either superman or you're grrrrrrriiiiiiinding at 3 revs a minute :?

morstar

simonaspinall wrote:

I'd agree with the comments on the flat - I find a 39T ring a great 'cruising' gear - I'd top out too quickly with the 34T and the 42T was a tad too big. Do those who use the compact set-up tend to find themselves going to the 50T when on the flat?

Slack has it right above. I am a recent convert to a compact chainset and living in a hilly area it has been a godsend. With a standard on a long ride, you can power up anything for a while but eventually you just run out of gas far earlier in the ride than you do with a compact.

Having been riding an old fashioned 42,52 chainset I really wondered how I would get on with 34 and 50. In answer, I find the 50 to be a really useful gear on the flat. I very rarely used the 52 on the old bike and yet am frequently in the big ring now.

daviesee

PeteMadoc wrote:

@ Daviesee I don't know how anyone can use 50 - 11 on the flat. You're either superman or you're grrrrrrriiiiiiinding at 3 revs a minute :?

I have to agree :oops: to a point.

My previous post was done in a figment of my imagination while sat in the office.

Here are my findings after taking the scenic road home tonight.

A nice cruising gear for me is 50/15 . Note that I cruise at around 75-80 rpm which is slower than some. A ratio of 3.3333 which means close to a 34/11 but I prefer not to cross gears. Or 53/16, or 48/14, or 42/12-13 (crossing again).

I seem to remember that back in the day they used to ride a 48/14 so that would make sense.

Pete:- On the ride home today I did use the 50/11 on the flat but there was a tail wind at that point. Using the wonders of Garmin playback I can tell you that I was doing 24.7 mph @ 77 rpm with a heart rate of 146 - I did say I had a tail wind . On club runs during the finishing straight (flat) the last mile build up to the sprint easily goes over 30 mph and sometimes over 35 mph so I have to be in the 50/11. I like the idea of being Superman though but I'll never live up to it :oops:

petemadoc

A full on sprint 30+ mph then 50 - 11 yes but I'd never spin out on the flat

With a decent tail wind just cruising, maybe 23-26mph I think I'd be on 50 and somewhere in the middle or slightly nearer the smaller rings of the cassette. No idea what each ring is other than 11 top, 28 bottom :oops:

But a headwind doing maybe 15-17 mph. This is where I find things tricky with a compact. On the small front ring (34) I find myself too near the small rings on the cassette and it doesn't feel right. The I try the big ring front (50) but end up on the 28 or one down at the back which again doesn't feel right.

What to do?

daviesee

Note that I have slightly edited my post while you were typing.

I don't actually make the sprint as I am not that good, I am just trying to stay in the bunch but I do take my turn at the front.
Cruising for me is 16-20 mph on 50/15 so I must have a lower cadence than you as shown above. Maybe?
Into a headwind on my compact I will be on the 34, probably at 15 on the back and working down ratio/up teeth numbers depending on strength.

34/11 = 3.1 and 50/28 = 1.8. A middle ground would be a ratio of 2.5 so 34/13-14 or 50/20.
Trying to keep the chain as straight as possible would suggest the 50/20.

Then again, I would do it by feel and not over analyse it anyway 8)

petemadoc

I don't usually tend to analyse it this much either, but

The headwind thing is the only time I don't feel happy with the gearing I have available as it seems impossible to keep the chain straight. I think I rev at about 80-85 . . . maybe, my cadence sensor disappeared some time ago.

I think the 39 ring would suit much better in this situation but at my level a compact is better in pretty much every other situation so I'll live.

Pross

Since moving to a 9 speed set up and 53/39 chainring I have found myself using the big ring a lot in training using about 53 x 19 or 53 x 21. Used to use the 42t about 90% of the time on my old 7 speed set up where I only went up to a 21 on the back