Is a 24-36-50 chainset feasible?
Manc33
Posts: 2,157
I always keep to the 22 tooth difference for the front mech on triple chainsets, but are people really running stuff like a 24-36-50 and getting away with it? I might replace my middle 34T with a 36T and my outer 46T with a 50T.
Sheldon Brown says oddly enough, triples don't care that much about having a small granny ring and a big jump to middle, but from middle to big you have to be careful about the differences.
So a 24-36-50 would give an overall difference of 26 (when Shimano say stick to 22) and it would be a 12T jump from granny to middle, then a 14T jump from middle to big.
Wait for it... "How much money are you throwing at this bike trying to make it work?"
The 2 chainrings will cost £35, but I can't flog the 34T/46T ones until I know the bigger ones will shift.
"You'll still lose money"
I know. :roll:
I have to piss about with it. :P Whats better, a wider gear range, or not a wider gear range? A wider gear range!
I'm not looking to buy this but they do make/sell them.
http://www.amazon.com/Sugino-152mm-24-3 ... B002SR5J1I
(152mm cranks? :? )
Shame it doesn't tell you the most suitable FD to use with it.
Surely if any FD can handle a 26T difference its the R443 I already have on it?
Sheldon Brown says oddly enough, triples don't care that much about having a small granny ring and a big jump to middle, but from middle to big you have to be careful about the differences.
So a 24-36-50 would give an overall difference of 26 (when Shimano say stick to 22) and it would be a 12T jump from granny to middle, then a 14T jump from middle to big.
Wait for it... "How much money are you throwing at this bike trying to make it work?"
The 2 chainrings will cost £35, but I can't flog the 34T/46T ones until I know the bigger ones will shift.
"You'll still lose money"
I know. :roll:
I have to piss about with it. :P Whats better, a wider gear range, or not a wider gear range? A wider gear range!
I'm not looking to buy this but they do make/sell them.
http://www.amazon.com/Sugino-152mm-24-3 ... B002SR5J1I
(152mm cranks? :? )
Shame it doesn't tell you the most suitable FD to use with it.
Surely if any FD can handle a 26T difference its the R443 I already have on it?
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Posts
That currently unavailable Sugino chainset you have linked to on Amazon is available under other names including Stronglight Impact. Spa Cycles have a big range and you can choose what rings you want.
So called "road triples" such as 50/40/30 or 53/39/30 can easily be converted to wide range just by changing the little ring. The inner bolt circle diameter (BCD) is normally 74, the same as touring triples like the Sugino above and older mountain bike five arm chainsets. So all you have to do is take off the chainset and replace the little ring (normally 30 or 32) on road triples and replace with a 24, 26 or 28. They will bolt straight on.
The outer bolt circle on road triples is generally 130 (Shimano type) which limits you to a smallest middle ring of 38, or 135 (Campag type) which limits you to a smallest middle ring of 39. As Sheldon Brown says, having a big difference between little and middle rings is not an issue.
Where you might have an issue is the difference between middle and outer rings. If you have a triple FD with a very deep back plate, it can foul the middle ring if the middle ring is too big. So it is wise to follow the manufacturer's instructions on what the difference should be between middle and outer. I reckon you would be safe with a 10 to 14 tooth difference with any FD.
I need to go down a long hill with a tailwind to really know if I need more than 46x11, but that isn't even that far off what 50x11 is anyway - just over 1/3 of a turn of the back wheel when its spinning more than 4 turns per pedal revolution anyways.
It would be more about having a 36T middle instead of a 34T. Thats just to avoid going to the bigger chainring as much, but its no big deal. On 34F/11R I have got to be going downhill to spin out.
I run a 10 speed Campag triple with 24 - 36 - 48 rings on my off-road / cross bike which works well, but I think that going to a 50 outer ring would be really pushing things. As it is the chain touches the bottom of the front cage when on the 24 ring and the smallest sprocket, not that this matters too much given I don't use this combination because of the excessive crossover. With a bigger outer ring you might have to avoid using the smallest 4 or 5 sprockets with the smallest ring, depending on their size, and shifts from the middle to the big ring might be pretty ropey.
I only ever used 50x11 once or twice and that was on a huge hill and it wasn't really needed, I could have just rolled. I think I would have to be going about 40 MPH to spin out at 50x11, maybe 35 MPH for 46x11. I just hate that 11T because the chain barely even wraps around it and I can see it wearing out really fast. The same can be said for smaller chainrings too of course.
If they had the same BCD I could try my 39T middle with it off my old Prowheel Ounce, but why spoil a brand new chainset with inferior parts.
Not sure what alloy the Prowheel Ounce is made of, but I think it is too cheap to be 7075.
I had a middle aluminium chainring slip on me back in the day (early 1990s yellow Rockhopper) and no one believes me! The teeth ended up like sharks fins, it was Biopace which is I think the reason it slipped. I am sure if it was a circle, that slipping wouldn't have occurred as early on as it did.
Now once again they are using those weird shaped chainrings... on time trials. They are even more out of shape than Biopace was though, that one I saw looked rectangular!
EDIT:
46X11 @ 90 rpm = 29.5 mph
48X11 @ 90 rpm = 30.7 mph
50X11 @ 90 rpm = 32.2 mph
So there is such a small advantage to a 48T I would only be putting a 50T on it if I changed it at all.
One thing was, on a 39T middle I was always having to get on the lowest 2 sprockets going up pretty much any incline and now it has a 36T middle its a lot better, even if I am using the big ring more, thats what its there for. When I had that 50T on I hardly ever used it.
50/34/26
48/34/26
46/34/24
I use Campag 10s Ultrashift levers, 9(& 10)s rear mech, with Shimano 9s cassette.
Excellent shifting.
12 13 15 17 19 21 23 25 28
12 13 15 17 19 21 24 27 30
13 14 15 17 19 21 24 27 30
I think to spin out on 34F/11R I would have to be going over 20 MPH and my average speed is about 12-13. :oops:
Up hills, I use the 2nd and 3rd lowest sprockets (26T and 21T) on that same 34T chainring and generally don't need the 32T sprocket, it would have to be pretty steep, but the 24T granny is there for that if needed.
After more riding, the 34T middle seems perfect for me on the flat with the 11-32T cassette. So my only advantage then would be a bigger large chainring and with a 34T middle, its not even worth doing that lol. I don't fancy a 16T difference between middle and big, although I just know someone will say they are running that and its working. :P
Not sure if this helps your decision-making process, but. . .one of my most used bikes has 52-39-28 with 12-25, 6703 shifters and 5703 front mech. No worries about teeth counts (24 total difference up front) and no rubbing on the FD until I get towards small-small which I never intentionally use anyway.