50/34 x 12/??
musto_skiff
Posts: 394
What is the max sprocket on the rear with a standard short cage rear mech, assuming the chain length is correct?
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I believe it's 27 but then I may be wrong. But I don't see why you'd need anything bigger to be honest.0
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I was thinking of going to a 27 just wanted to double check here with the forum guru's0
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Loads of posts on the comapct subject................
Shimno short cage rear mechs will cope with max 27 rear mech (and probably 28 with the chain a bit longer). But I doubt whether you get the chain in 50x27 - maybe 50x24, but the rear mech will be at its extreme.
And please - don't start posting saying 50x12 isn't a big enough gear. It probably isn't for the Cancerallas and Boonens of this world, but for the rest of us it probably is !0 -
itisaboutthebike wrote:And please - don't start posting saying 50x12 isn't a big enough gear. It probably isn't for the Cancerallas and Boonens of this world, but for the rest of us it probably is !
I actually wish I had the 11 on the bike for the big decents!!.............sorry!!0 -
For Shimano it's a 27. Seems like I read Campy Record could handle a 29. Key words being "seems like". In reality what really determines the capacity is the vertical distance from the centerline of the axle to the center of the rear mech hanger. I have an older bike
with horizontal dropouts(actually slightly sloping) that allows my Dura-Ace rear to handle
a 30 tooth rear cog. However, my new bike with vertical dropouts will only allow a 27
with the same mech. This is because the vertical distance is greater on the old bike.
Also, the so called short cage rear mech, which most people use with a double crankset,
has less chain take-up and payout, if you will, than it's longer caged triple and mountain
bike cousins so you are limited in that respect.
Dennis Noward0 -
itisaboutthebike wrote:And please - don't start posting saying 50x12 isn't a big enough gear. It probably isn't for the Cancerallas and Boonens of this world, but for the rest of us it probably is !
I might never even use 50x12 on the flat, but I sure as hell use the 50x11 going downhill. Some people might say "just get aero and you don't need the 11t" but I find it takes ages to accelerate upto speed by freewheeling, so the 11t comes in handy there.
50x12 is a fine gear most of the time - but what's wrong with a bit of extra range?0 -
'Eat My Dust' .......pedallling 50x11 downhill in the Alps.................you probably will be eating dust at some point during your cycling career !0
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I have a 11-28 MTB cassette on my cross bike running a 48/34 compact chainset and a short cage 105 rear mech.I'm only concerned with looking concerned0
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50/34 x 12-27 with a standard short-cage Ultegra 10sp rear mech is fine.
You shouldn't cross the chainline by using 50 x 27 or 34 x 12, but it will do it.
- actually it seems pretty happy 50 x 27, but 34 x 12 makes a noise, think it's the chain catching on the 50t0 -
I have ordered a 12-27.
Thanks for the input all ...0 -
No reason why not given a long enough chain (if you make the chain long enough you could have the rear mech relaxed). Better to do that and have the chain slack in the 34 and the little 2 cogs - which you shouldn't be using anyway.itisaboutthebike wrote:Shimno short cage rear mechs will cope with max 27 rear mech (and probably 28 with the chain a bit longer). But I doubt whether you get the chain in 50x27 - maybe 50x24, but the rear mech will be at its extreme.
I have an 11 with my 50 and use it regularly - on one descent last night I could only get to 33mph tucking, but if I pedaled was doing 37 or 38, and it's fun doing those sort of speeds (also good for training if you're trying to keep your heart rate up on the descents).0 -
redddraggon wrote:itisaboutthebike wrote:And please - don't start posting saying 50x12 isn't a big enough gear. It probably isn't for the Cancerallas and Boonens of this world, but for the rest of us it probably is !
I might never even use 50x12 on the flat, but I sure as hell use the 50x11 going downhill. Some people might say "just get aero and you don't need the 11t" but I find it takes ages to accelerate upto speed by freewheeling, so the 11t comes in handy there.
50x12 is a fine gear most of the time - but what's wrong with a bit of extra range?
I have found that I don't require a 50-11 for downhill runs because the extra body weight that I
carry(and there is a lot of it) gets me moving toward the bottom much faster than pedaling ever could. Overweight does have it's advantages although I have found
that all this extra speed going down doesn't really translate easily back into uphill help.
Dennis Noward0 -
I have a 52/42/30 triple with 11-28 on the back. I love the 52/11 on a big descent. It never ever gets used on the flat of course.0
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I've just put an 11-28 (Sram) cassette on my bike
Ultregra 50-34 short cage setup.
It works fine, with no adjustments or longer chain required.
I think Shimano cassettes change nicer, but the 11-28 range is excellent for the mountains.0 -
I have got a 50/34 and both a 12-27 and an 11-23 rear cassette with a dura ace rear mech. All combinations work (in that the chain will physically run over the 50 front and 27 rear) not that you want to run those chainlines. In fact, I think I may have prematurely stretched my chain from using the 25 or the 21 rear cog on the big ring as a convenient spinning gear, as it still puts a visible strain on it, either way the damn thing is jumping despite several attempts at tuning the rear mech position.0
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I thought I had an 11 on my new bike, but found I was spinning out on my local hills. Checked. It's a 12
My fault I suppose, I accidentally specified an 11-25 which Shimano don't seem to do. Bit annoyed that the shop doing the build didn't ring me, because I would have chosen an 11-23 or a 12-27 to give me a fast, flat choice and a hilly choice. Now I'm stuck with an inbetweeny.0 -
dennisn wrote:redddraggon wrote:itisaboutthebike wrote:And please - don't start posting saying 50x12 isn't a big enough gear. It probably isn't for the Cancerallas and Boonens of this world, but for the rest of us it probably is !
I might never even use 50x12 on the flat, but I sure as hell use the 50x11 going downhill. Some people might say "just get aero and you don't need the 11t" but I find it takes ages to accelerate upto speed by freewheeling, so the 11t comes in handy there.
50x12 is a fine gear most of the time - but what's wrong with a bit of extra range?
I have found that I don't require a 50-11 for downhill runs because the extra body weight that I
carry(and there is a lot of it) gets me moving toward the bottom much faster than pedaling ever could. Overweight does have it's advantages although I have found
that all this extra speed going down doesn't really translate easily back into uphill help.
Dennis Noward
Hi Dennis.
Correct me if I am wrong, but
if we both jumped out of a plane together, we would drop at the same rate of 1g due to the force of gravity? so if this is true, how would you go down hill faster than me because your heavier? presuming you are Funny though as it does appear fat people go down hill faster 
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You're wrong, oldwelshman. That theory only applies in a vacuum. In the real world we have air resistance, which doesn't tend to increase that much for fatter people (at least not until the gut gets so big you can no longer hold a tuck). Since the pull of gravity has increased more than the drag holding them back they will go faster.0
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aracer wrote:You're wrong, oldwelshman. That theory only applies in a vacuum. In the real world we have air resistance, which doesn't tend to increase that much for fatter people (at least not until the gut gets so big you can no longer hold a tuck). Since the pull of gravity has increased more than the drag holding them back they will go faster.
Oldwelshman was right. Mass doesn't matter during descent re the the speed. However the bigger you are the more force you will move with (F=Ma). Momentum will also increase - speed won't.0 -
redddraggon wrote:Momentum will also increase - speed won't.
momentum = mass x velocity so if we assume mass is constant the above is not true ...
I cant recall A level physics but I know from experience that heavy people always get to the bottom of a water slide first or when sledging ....
I have do doubt that the heaviest will always win a freewheeling fest ....0 -
musto_skiff wrote:redddraggon wrote:Momentum will also increase - speed won't.
momentum = mass x velocity so if we assume mass is constant the above is not true ...
Obviously momentum will increase then - mass is not constant from a heavy person to a light person.
If you don't add any power to the pedals, it's all about aerodynamics not mass.
Of course it would be harder to stop a heavier person going at the same speed as a light person - giving the wrong impression that the heavier person is going faster.0 -
itisaboutthebike wrote:'Eat My Dust' .......pedallling 50x11 downhill in the Alps.................you probably will be eating dust at some point during your cycling career !
I've not had the pleasure of the Alps
(yet) but I've found that I can get to 42mph on my commute before I run out of hill. I'm sure that a 11 would add something to that. 0 -
You really should make sure you know what you're talking about before saying I'm wrong, reddragon. You seem not to have read my post properly either - I already explained that it's all down to the retarding aero force not increasing as much as the driving force. F = ma actually has nothing to do with it, as we're not talking about the acceleration but the steady state - after all you only care that Mr Fat goes down the hill 2mph faster than you, not how quickly he gets up to that speed. In the steady state, the driving force is down to gravity: F = mg sin (x) where x is the angle of the slope, so is proportional to the mass. Meanwhile (making the reasonably accurate assumption that air resistance dominates bearing drag) the retarding force is: F = 1/2 p Cd A v^2 where p is the density of air, Cd is the drag coefficient A is the frontal area and v is the speed. Hence v = root (2 mg sin (x) / p Cd A). Our variables here for a given slope are m, Cd and A. As I mentioned earlier, since the product of Cd and A increases less than m does for a fat person, the fat person goes faster.0
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So, in layman's terms, fat people don't need an 11?0
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aracer wrote:You really should make sure you know what you're talking about before saying I'm wrong, reddragon. You seem not to have read my post properly either - I already explained that it's all down to the retarding aero force not increasing as much as the driving force. F = ma actually has nothing to do with it, as we're not talking about the acceleration but the steady state - after all you only care that Mr Fat goes down the hill 2mph faster than you, not how quickly he gets up to that speed. In the steady state, the driving force is down to gravity: F = mg sin (x) where x is the angle of the slope, so is proportional to the mass. Meanwhile (making the reasonably accurate assumption that air resistance dominates bearing drag) the retarding force is: F = 1/2 p Cd A v^2 where p is the density of air, Cd is the drag coefficient A is the frontal area and v is the speed. Hence v = root (2 mg sin (x) / p Cd A). Our variables here for a given slope are m, Cd and A. As I mentioned earlier, since the product of Cd and A increases less than m does for a fat person, the fat person goes faster.
Because the increased force exerted on a heavy cyclist compared to a light one overcomes any increase in aero resistance from a greater frontal area/less aero shape etc? (assuming they are cycling down the same slope in the same conditions). Now if you can mathemtically correct for the increase in rolling resistance from the bike for the heavier rider then I will be impressed
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I was using 50x11 for a good portion of my commute along the Embankment last night.
Does that make me really fat?0 -
aracer wrote:You're wrong, oldwelshman. That theory only applies in a vacuum. In the real world we have air resistance, which doesn't tend to increase that much for fatter people (at least not until the gut gets so big you can no longer hold a tuck). Since the pull of gravity has increased more than the drag holding them back they will go faster.
I could be wrong, but that really doesn't sound right.
The acceleration due to gravity is constant, whether I'm fat or thin or a 10 ton truck. That means my velocity will increase at a constant rate irrespective of my mass.
If you add in wind resistance, a fat or thin rider will be roughly the same but the 10 ton truck will get left behind as it has more drag.
The acceleration provided by a slope is g.sin(x); irrespective of mass.
Wasn't this what Galileo showed when he dropped different masses off the leaning tower of Pisa and they landed at the same time?0 -
simbil1 wrote:aracer wrote:You're wrong, oldwelshman. That theory only applies in a vacuum. In the real world we have air resistance, which doesn't tend to increase that much for fatter people (at least not until the gut gets so big you can no longer hold a tuck). Since the pull of gravity has increased more than the drag holding them back they will go faster.
I could be wrong, but that really doesn't sound right.
The acceleration due to gravity is constant, whether I'm fat or thin or a 10 ton truck. That means my velocity will increase at a constant rate irrespective of my mass.
If you add in wind resistance, a fat or thin rider will be roughly the same but the 10 ton truck will get left behind as it has more drag.
The acceleration provided by a slope is g.sin(x); irrespective of mass.
Wasn't this what Galileo showed when he dropped different masses off the leaning tower of Pisa and they landed at the same time?
Aracer is right, if he was wrong I would have corrected him..........0
