Cog sizes and the point of it all

Inquitus

Posts moved from Bargain Alerts thread, could do with a thread of it's own

Is 12T to big on a compact, I need a new cassette but I am worried I'll spin out racing, currently have an 11T?

Harrybelafonte

Inquitus wrote: »

Is 12T to big on a compact, this is defo a bargain and I need a new cassette but I am worried I'll spin out racing, currently have an 11T?

Same boat as yourself, I think 12-27 is too bif fir racing on a compact. Seems to be tougher to find 11-25s though.

mirv

Depends on your leg speed; taken from the calculator at http://www.machars.net/bikecalc.htm

Harrybelafonte

It's more the 27 Vs 25 I think than 11 vs 12, mind you 110rpm at 50x11 is the best I can manage.

I've always like how that claculator won't go higher than 120 anymore (it does for some, but not the bigger ones)

mirv

34 x 27 in a race?

Harrybelafonte

That's my point, you wouldn't need 34x27 or 50x27 in a race? Unless it's a real hilly course which we don't really have that often.

Harrybelafonte

dave_o_brien wrote: »

http://www.chainreactioncycles.com/Models.aspx?ModelID=67228

Tiagra, jeez whaddaya like, that'd weigh a tonne.

colm_gti

Harrybelafonte wrote: »

That's my point, you wouldn't need 34x27 or 50x27 in a race? Unless it's a real hilly course which we don't really have that often.

You'd never ever need a 27t in a race I don't think, it would want to be a vicious hill to need that, and you'd probably go backwards through the bunch trying to twiddle that small a gear up it anyway.

FWIW I use an 11-23 with my 53/39 and only really wish I had a 25t when the gradient goes over 10% for extended periods of time...I'll be putting an 11-25 on my new wheels...

Harrybelafonte

colm_gti wrote: »

You'd never ever need a 27t in a race I don't think, it would want to be a vicious hill to need that, and you'd probably go backwards through the bunch trying to twiddle that small a gear up it anyway.

FWIW I use an 11-23 with my 53/39 and only really wish I had a 25t when the gradient goes over 10% for extended periods of time...I'll be putting an 11-25 on my new wheels...

Hmm, me, Des Hanlon so, til the Commissare roared at me to drop a cog. :rolleyes: It worked. I did wish I had a 27 on that race though in fairness.

CramCycle

I always had a fairly wide range of gears, usually 11-27 or even broader, I have noticed that in racing the jumps are slightly too much and I lose the guy in front of me on occasion if I drop down to sharply.

Beasty

Check out this thread started by 12 sprocket

If the juniors can tan our hides on 53x14 I don't think anyone is really missing out on being "limited" to 50x12 - they can only ride a maximum gear that is nearly 10% "lower" than the rest of us

Hmmzis

The 50x11 combo is only realy useful when going down a hill, drafting large vehicles and maybe in a fast bunch gallop to the line though the few gallops I've done so far have been in the 13 or 14 cog.

petethedrummer

Buy 2 cheaper cassettes. One for hilly races and one for flat races.

2 Wheels Good

I'd also take into consideration what average cadence a person does. If you typically have a high cadence then using a 12-27 or similar should be fine, if you're slower with more power than speed then the closer the ratios the better I would think. (I'm sure there's a science behind all this somewhere)

Slo_Rida

Hey all
I asked Cram to start this thread as it's a curious one for me.
I'm on a 50 34 up front, fairly common now even among stronger cyclists AFAICS. Now on the back (hold your laughter lads) I have a 28-11 :eek:
Is anybody else on something like this?
It's just that it seems to be greeted with the same reaction as a triple chainring...or stabilisers! I find I use the 50-28 regularly (I prefer not to shift the front derailleur where possible) and the 34-28 sometimes. I've spun away on my 34-28 in a couple of A4 races now and stayed with the bunch so I'm not really "ashamed" of it.
Just wondering what peoples opinions on casette/cog/chainring combo's are.
Slo

youtheman

Slo_Rida wrote: »

Hey all
I asked Cram to start this thread as it's a curious one for me.
I'm on a 50 34 up front, fairly common now even among stronger cyclists AFAICS. Now on the back (hold your laughter lads) I have a 28-11 :eek:
Is anybody else on something like this?
It's just that it seems to be greeted with the same reaction as a triple chainring...or stabilisers! I find I use the 50-28 regularly (I prefer not to shift the front derailleur where possible) and the 34-28 sometimes. I've spun away on my 34-28 in a couple of A4 races now and stayed with the bunch so I'm not really "ashamed" of it.
Just wondering what peoples opinions on casette/cog/chainring combo's are.
Slo

I have this exact same combination 50/34 and 11/28 (and I'm a MAMIL Sportive rider). The reason I chose it is because it gives me the exact same top and bottom gear ratios as a standard triple. I try stay in the big cog (50) and much as I can, as I work down the cassette. When I reach the 50 (front) and 28 (back) and I need to change down then I change down on the front (from 50 to 34) and up three in the back (from 28 to whatever that is). This gets me in the exact same gear ration as I was in (to my feel, anyway). Then I have three more gears to do down. So in reality I only ever use about 13 gears (no need for that triple namby pamby 27 gear wimp crap for me).

dited

youtheman wrote: »

When I reach the 50 (front) and 28 (back) and I need to change down then I change down on the front ...

Slo_Rida wrote: »

I find I use the 50-28 regularly ...

Cross-chaining is bad, mmm-kay. Try to avoid the gears that make the chain cross over at an extreme angle, i.e. big chainring + big sprocket (eg 50-28) or small chainring + small sprocket. It's unnecessary and puts the chain under stress at greater angles than it's designed to cope with. You can achieve the same gearing by downshifting the front derailleur earlier.

ford2600

Do ye just crosschain while racing? I.e 50/28

The amount of lads I see doing this on 2/3k bikes on sportives is hard to figure out

Beasty

ford2600 wrote: »

Do ye just crosschain while racing? I.e 50/28

The amount of lads I see doing this on 2/3k bikes on sportives is hard to figure out

I try and avoid it when racing (and always avoid it when not) but sometimes don't realise I'm on the largest cog, or will do it for a short time if I'm about to crest a hill

Lumen

Better to crosschain than to drop a chain under pressure.

Plastik

You've used the 34/28 in a race? It must have been a whopper of a hill.

I raced a lot of last year on a 50/34 11-23 and found that even with the 11-23 the pace was never slow enough to need the 34, so straight away you're limiting yourself to racing in 10 gears alone. You might cross chain on the odd hill, but it was preferable to dropping to the 34 and going down 3-5 gears on the cassette.

I've since changed to 53/39 and still use the 11-23 on the race wheels, 12-25 day-to-day.

dited

Lumen wrote: »

Better to crosschain than to drop a chain under pressure.

Indeed, but in general, and particularly outside a race scenario, it's avoidable with a bit of foresight.

ford2600

dited wrote: »

Indeed, but in general, and particularly outside a race scenario, it's avoidable with a bit of foresight.

When racing is understandable, hard to prioritise drivetrain lifespan at 180bpm!

Lumen

dited wrote: »

Indeed, but in general, and particularly outside a race scenario, it's avoidable with a bit of foresight.

Sure, if it's not a race it doesn't matter anyway.

The problem is that on a compact there is a big jump between front cogs, so you generally have to change up a few gears at the back before dropping the front. This creates all sorts of nasty dynamics in the drivetrain which makes dropping a chain more likely.

The absolutely worst place to drop a chain is when the bunch hits the bottom of a climb, and that's exactly where you're likely to want to swap front ring. Been there, done that, got dropped.

Raam

Lumen wrote: »

Sure, if it's not a race it doesn't matter anyway.

The problem is that on a compact there is a big jump between front cogs, so you generally have to change up a few gears at the back before dropping the front. This creates all sorts of nasty dynamics in the drivetrain which makes dropping a chain more likely.

The absolutely worst place to drop a chain is when the bunch hits the bottom of a climb, and that's exactly where you're likely to want to swap front ring. Been there, done that, got dropped.

Do you use a chain keeper?

Lumen

Raam wrote: »

Do you use a chain keeper?

Yes. It's happened even with that. It's probably my mechanical incompetence, or lack of shifting finesse, or SRAM.

fat and slow

I've had problems with my first road bike, it was a triple, especially swapping the front mech from big ring to middle ring and accidentally going to small ring and then dropping the chain. Since I've got my double chainset bike i've never dropped a chain. It's a standard 53-39 and a 12-27. Like the posters have said cross chaining can happen in races especially when you hit the bottom of the hill at speed, and then the speed drops and before you know it your in a 53-27 gear, with a decision to hang on or try a gear change. The lack of gears has not been a problem so far for me. But I'm only racing the interclub league which is flat. With the exception of one hill climb tt and one hill climb finish race

Slo_Rida

Lumen wrote: »

The absolutely worst place to drop a chain is when the bunch hits the bottom of a climb, and that's exactly where you're likely to want to swap front ring. Been there, done that, got dropped.

I pushed my chain out over the big ring after cresting a "hill" once. I was eye-balls out and that may have contributed to the poor change but if I had had a 28 or even a 27 I would have big-ringed the hill and avoided any front changing.
I don't mind cross chaining between 50 and 28 and I would never have the issue of crossing between 34 and 11. A few minutes cross chaining a few times a year won't cause any problems IMO.

Slo_Rida

dited wrote: »

Indeed, but in general, and particularly outside a race scenario, it's avoidable with a bit of foresight.

I would never cross chain outside of racing...

dited

Slo_Rida wrote: »

I would never cross chain outside of racing...

My bad, didn't get that from your original post.

CramCycle

I use a triple, theres no shame in it, I rarely use the small but it's there if I need it,

NeedMoreGears

ford2600 wrote: »

When racing is understandable, hard to prioritise drivetrain lifespan at 180bpm!

At 180bpm a plastic drivetrain would last a lot longer than me!

Slo_Rida

NeedMoreGears wrote: »

At 180bpm a plastic drivetrain would last a lot longer than me!

Can you get them in a compact?

mirv

No racing experience myself but I've got a 52-39 and a 13-26 cassette. I'm rarely looking for a 11t or even 12t. Can spin up to around 60kph (120rpm in 52x13) if the wind and gradient allows it. Although I'm a bit of a lightweight so I tend to have lower terminal speeds on descents regardless of power.

I'd imagine if you can spin out a 12t cog on a descent you'd either be better off tucking, or you really need to work on your leg speed. Sprints might be different as you can't maintain as high a cadence while standing and mashing I guess.

IM0

Beasty wrote: »

[about the big chainring x big cog combination.........] I try and avoid it when racing (and always avoid it when not) but sometimes don't realise I'm on the largest cog, or will do it for a short time if I'm about to crest a hill

does the noise not remind you no

Razleavy

IM0 wrote: »

does the noise not remind you no

The wonder of Di2