Is a 24-36-50 chainset feasible?

Manc33

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?

mercia_man

You can normally push mechs beyond their stated capacity. I have successfully used a 48/40/24 chainset with a Campag triple FD, stated capacity 22 teeth. I reckon I could probably have got a 50 tooth outer ring to work. Sheldon Brown is right. The gap between little ring and middle is not generally an issue. Am currently using 46/39/24. In the old days, I have also used a 46/42/24 "half step plus granny" set up with a double FD with a stated capacity of something like 14.

mercia_man

Here's some more thoughts about wide range triples.

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.

mercia_man

My final thought! Just read on the CTC forum a post from a chap who can't get a new Ultegra triple FD to work with a 10 tooth difference between middle and outer rings because of fouling. Apparently Shimano state it should be a 13T difference. Older mechs with shallower backplates have more leeway.

Manc33

I think that is the difference between the FD-R443 and FD-R453. The R443 has a more shallow inner plate in comparison. Although the R453 would appear to be slightly better (or newer) due to the numbering, I think its probably just the R443 is 8-speed and the R453 is 9-speed.

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.

BenderRodriguez

Manc33 wrote:

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.

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.

Manc33

Right now it is a 24-34-46 and changes well so I will probably leave it. Its just not that important to have bigger big rings, I don't fly down enough hills to need it. Not sure what 46x11 @ 90 RPM equates to in speed, but I don't go much faster than that.

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.

de_sisti

I run Stronglight Impact triple on my 3 bikes with the following combinations:

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.

de_sisti

BenderRodriguez wrote:

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.

With a Stronglight Impact Triple it'd be ok.

lesfirth

Diverting away from the original post. What size cassettes are you guys using with these 24t chainsets?

de_sisti

I customise my cassettes:

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

Manc33

I got an 11-32T on. That 11T can be useful and save using the big chainring sometimes.

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

Bordersroadie

Manc33 wrote:

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.

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.

Manc33

I think the best bet would be 24-36-48 to keep the overall difference to 24 and stop the shifting from middle to big becoming sloppy by keeping that difference at no more than 12. I do like a snappy shift from middle to big. Expecting to squeeze it to a 26 difference is probably not worth it considering I wouldn't spin out a 50x11.