45t capacity rear derailleur - worth the change?

[mikeymo]

I built up a bike when the frame became available cheap. Basically a Ridgeback Panorama Deluxe.

It's Sora shifters, FD and RD. With chainrings 48,38,28 and 11-34 cassette. That gives me 22 to 118 gear inches according to Sheldon's calculator.

Around the Outer Hebrides and the streets of West Yorkshire it's generally fine, certainly better than the similarly framed Alfine 8 I had before.

I've got up every hill I've tried using 28 chainring to 34 sprocket. But a couple of times I thought, "if this were any longer, or I had any weight on, I wouldn't make it".

On the other hand I've never spun out using 48 to 11. And even when I've used it I've easily gone as fast as I feel happy, at a fairly slow cadence. Anything much past 27 mph I start to get nervous.

The Sora RD has a capacity of 43t. But I've seen there's a Simano XT (I think), that has a capacity of 45t. So I was thinking of changing and putting 48,36,26 on the front.

It gains me only a little, and part of me thinks that if I'm going somewhere with lots of hills, the best thing might be to just put a different set of chainrings on - maybe 44, 34, 24.

Will there be any drawbacks with a wider capacity RD? Will it be harder to set up? I didn't have any problems with the RD, but the FD took a lot of fiddling to get right. Will it be harder to adjust with a wider range of chainrings?

Many thanks.

[irc]

Biggest XT cassette I see is an 11-42. There are 45t rings but that may give too big a jump between gears.

Is your bike 11 speed?

Ideally if you don't use your highest gears then getting lower gears is best achieved by smaller chainrings. It lowers gearing without increasing the gaps between gears. The downside of just increasing the size of the rear cassette is bigger gaps between gears. I don't even like the 17-20 gap on a 9 speed 11-34 and have made custom cassettes to go 12-14-16-18 -20 rather than the 11-34s 11-13-15-17-20.

My low gear is 22-34 for loaded touring. Any higher would be too high. But it's all personal choice and with Sora gears there will be a limit to how small a chainring you can use.

[mikeymo]

Biggest XT cassette I see is an 11-42. There are 45t rings but that may give too big a jump between gears.

Is your bike 11 speed?

Ideally if you don't use your highest gears then getting lower gears is best achieved by smaller chainrings. It lowers gearing without increasing the gaps between gears. The downside of just increasing the size of the rear cassette is bigger gaps between gears. I don't even like the 17-20 gap on a 9 speed 11-34 and have made custom cassettes to go 12-14-16-18 -20 rather than the 11-34s 11-13-15-17-20.

My low gear is 22-34 for loaded touring. Any higher would be too high. But it's all personal choice and with Sora gears there will be a limit to how small a chainring you can use.

Sorry, maybe I wasn't clear. The bike is 9 speed cassette plus 3 chainrings. I'm considering replacing the rear derailleur. The Sora that's on at the moment has a capacity of 43. With my current cassette of 11-34 and front chainrings of 48-38-28, I'm right on that capacity (crankset range of 20 + cassette range of 23 = 43).

But there is a Shimano 9 speed rear derailleur available - the XT RD-M771-SGS which has a capacity of 45. Which would allow me to put a smaller small chainring of, say 26 teeth on. As as per the current Panorama:

https://www.biketart.com/bikes-c1/road-bikes-c35/ridgeback-panorama-2018-p43706/s120992?utm_source=google&utm_medium=cpc&utm_term=ridgeback-panorama-2018-m-size-m-size-m-rbc72md&utm_campaign=product%2Blisting%2Bads&gclid=EAIaIQobChMIs4OGv5Cu3QIV5pXtCh38rQWJEAYYAiABEgJbVfD_BwE

Or even drop to 46,34,24.

Or some combination of that with a different cassette. But I'll want to stay with 9 speed.

My main concern was whether very long cage rear derailleurs generate other problems.

[mikeymo]

Interestingly, Ridgeback seem to have built up the Panorama outside Shimano's specs. Here's the bike:

https://www.ridgeback.co.uk/bikes/touring/world/panorama

With a gap of 22 teeth between the biggest and smallest chainrings

And here's Shimano's spec for that front derailleur, which gives a 'capacity' of 20 teeth.

https://bike.shimano.com/en-EU/product/component/sora-r3000/FD-R3030-F.html

[JakobW]

Try sucking it and seeing with the current RD? Shimano are generally conservative WRT capacity, so it might work with what you've got (though it might be a bit more temperamental). Because of their geometry, long-cage derailers are supposed to give less precise shifting, but if you're not racing I'm not sure you'll notice the difference.

[mikeymo]

Try sucking it and seeing with the current RD? Shimano are generally conservative WRT capacity, so it might work with what you've got (though it might be a bit more temperamental). Because of their geometry, long-cage derailers are supposed to give less precise shifting, but if you're not racing I'm not sure you'll notice the difference.

Yes, I suppose what I need to do is load the bike up with touring kit, then find a nice long steep hill to go up. When I was in Scotland there was a hill nearby that had some 15% sections which I just about got up, but it was more bloody-minded determination and a lot of swearing than actual fitness.

[RickH]

I'd be inclined to just try a 26T or even 24T inner ring, assuming you can get one to fit the chainset, with the existing setup.

It will probably work OK. You'll probably need to do a double shift (up a couple of gears at the rear), if you don't already, & the chain may go a bit slack on the smallest one or two sprockets when using the small chainrings (they'll probably still work, but you shouldn't really be using those gears anyway).

[Mick F]

Capacity = (big ring - small ring) + (big sprocket - small sprocket)

For my Mercian it's (53-28) + (30-12) = (25+18) = 43.
This is with a Campag Comp rear mech.

Moulton is (61-34) + (28-11) = (27+17) = 44.
This is with a Shimano Deore XT rear mech.

Both are working well within capacity. Big/Big is easy, and Small/Small doesn't have a slack chain on either bike.

In due course, I plan of fitting a custom 12-32 to Mercian as well as swapping the 28t to a 26t inner ring.
This will make it (53-26) + (32-12) = (27+20) = 47 and I have no doubt whatsoever that it'll be fine.

[Cugel]

I built up a bike when the frame became available cheap. Basically a Ridgeback Panorama Deluxe.

It's Sora shifters, FD and RD. With chainrings 48,38,28 and 11-34 cassette. That gives me 22 to 118 gear inches according to Sheldon's calculator.

Around the Outer Hebrides and the streets of West Yorkshire it's generally fine, certainly better than the similarly framed Alfine 8 I had before.

I've got up every hill I've tried using 28 chainring to 34 sprocket. But a couple of times I thought, "if this were any longer, or I had any weight on, I wouldn't make it".

On the other hand I've never spun out using 48 to 11. And even when I've used it I've easily gone as fast as I feel happy, at a fairly slow cadence. Anything much past 27 mph I start to get nervous.

The Sora RD has a capacity of 43t. But I've seen there's a Simano XT (I think), that has a capacity of 45t. So I was thinking of changing and putting 48,36,26 on the front.

It gains me only a little, and part of me thinks that if I'm going somewhere with lots of hills, the best thing might be to just put a different set of chainrings on - maybe 44, 34, 24.

Will there be any drawbacks with a wider capacity RD? Will it be harder to set up? I didn't have any problems with the RD, but the FD took a lot of fiddling to get right. Will it be harder to adjust with a wider range of chainrings?

Many thanks.

One must be careful with wide-range triples, especially those with tiny rings, as it can be difficult to get the front changer to work well or even to clear the frame. Personally I try to use Shimano front chainsets of the 52-39-30 variety with a cassette configured to give the required highest and lowest gears.

The problem, as you will know, then becomes the capacity of the rear mech. (And perhaps too many big gaps in the ratios). 9-speed MTB Shimano mechs do seem to cope with big ranges and big sprockets too. You might find it wise or necessary to avoid riding in big-big or small-small, as you can have either too much derailleur stretch (big-big) or a floppy chain which also rubs on the mech (small-small). But you wouldn't ride those combinations or anywhere near them anyway, if you have a triple.

Currently I have 14-32 11-speed cassette with a 10-speed 30-39-52 Ultegra triple on the winter bike. A long-arm 105 rear derailleur copes with this. The front changer has to be an Ultegra 6703, which matches the curve of the 52 ring and has enough travel for a triple. Big-big and small-small are no-nos. Otherwise, all is fine.

I'm tempted to cannibalise some 11-speed cassettes to get 14-36. This might require a rear mech with greater capacity. Will an 11-speed MTB mech work with 11-speed 105 STI levers and this increased range? I don't know ... yet.

Notice the 14 smallest sprockets in all this. No one needs 11, 12 or even 13 really - not unless their big ring isn't so big or they're Geraint The Helmet. Starting at 14 gives you lesser jumps in the fast ratios. 14-15-16-17-18-19-21-24-28-32-36 would be my ideal.

Cugel

[Mick F]

Disagree entirely.

12t and a 53t is a nice high 115" gear. I use it lots, and would have an even higher one perhaps. I ain't no Geriant, but a 66 year old beer-loving average slightly overweight bloke.

[Cyril Haearn]

Disagree entirely.

12t and a 53t is a nice high 115" gear. I use it lots, and would have an even higher one perhaps. I ain't no Geriant, but a 66 year old beer-loving average slightly overweight bloke.

How fast do you turn it?

I dunno why anyone wants a gear over 78"

[Mick F]

Long-term average cadence (when I used to measure it) was 67rpm.

We have long hills, some of them not so steep. Rather than freewheeling at 15mph, I'd rather pedal and be at 25mph.
Also, on the flat, I can turn the cranks in top gear at 10mph. Nice and relaxing. Often do it in town.
10mph at 115" is a cadence of 29rpm.

[NetworkMan]

You are in a roughly similar position to me and I think and the simplest thing to do is to replace the 28T inner ring with a 24T. the smallest that you can fit on the 74 BCD of the Spa XD2/TD2 I think you have. That is what I did although mine is 8 speed not 9. You don't need to change the larger two rings, cassette or FD unless you want to. I believe you have a friction shifter for the FD, not STI is that correct?
It does mean that the inner ring will only be usable for hilly ground and you'll likely spin out on level ground. That's life with such a small ring.
You may well find that the chain goes slack in the two highest gears 11T and 13T on the 24T inner ring, but you probably shouldn't be using those anyway since the cross chaining is so bad. Gear 3 is 15T so you need a capacity of (34-15) + (48-24) = 43T which is just what you have already.

Before doing this you need to check that the 24T won't make the chain hit the (edit) bottom of the cage. To do this select the 28T inner ring and the smallest rear sprocket you'll be using - gear 3 in this case. Now measure the distance between the chain and the bottom of the FD cage. You need a clearance of 2 mm for each 1T you are gong to change by, in this case 4T, so you need 8 mm. This assumes that you are not moving the FD or changing the other two rings.

Is there a downside with the large gap between 38T and 24T? I don't believe that shifting is an issue using a friction shifter. Going down you knock the chain off the middle ring and it lands on whatever is there. Going up you press the chain against the middle ring and it climbs up onto it. I've used this ring combination on two bikes now with no real trouble. You need to be happy with the shift up and down between 24T and 38T. Highest on 24T will be (24/15)*27 = 43 inches (I call that a bit hilly, YMMV). Middle ring gear 8 is (38/30)*27 or 34 inches. That's OK there is plenty of overlap and gear 6 (23T) will give you 45 inches, about the same.

Of course the 11T top sprocket is too small and the 48/11 is just too high, for me anyway, but the only way to get something more sane while keeping the 34T is to make a hybrid cassette. That is just what 531colin did - viewtopic.php?f=5&t=54328.

Edit
Don't know what cadence you prefer but MickF above probably prefers higher gear/lower cadence than most people on here.

Another edit
The Sora is intended for 50/39 so if you depart further from this than your 48/38 you may well have more problems. Hard to be sure but CJ in Cycle reckoned that 4T was the max so maybe 46/36. I have no experience of going smaller than 48/38. CJ writing in Cycle said that the small ring is not an issue, if you do the check I've described above.

[mikeymo]

You are in a roughly similar position to me and I think and the simplest thing to do is to replace the 28T inner ring with a 24T. the smallest that you can fit on the 74 BCD of the Spa XD2/TD2 I think you have. That is what I did although mine is 8 speed not 9. You don't need to change the larger two rings, cassette or FD unless you want to. I believe you have a friction shifter for the FD, not STI is that correct?
It does mean that the inner ring will only be usable for hilly ground and you'll likely spin out on level ground. That's life with such a small ring.
You may well find that the chain goes slack in the two highest gears 11T and 13T on the 24T inner ring, but you probably shouldn't be using those anyway since the cross chaining is so bad. Gear 3 is 15T so you need a capacity of (34-15) + (48-24) = 43T which is just what you have already.

Before doing this you need to check that the 24T won't make the chain hit the (edit) bottom of the cage. To do this select the 28T inner ring and the smallest rear sprocket you'll be using - gear 3 in this case. Now measure the distance between the chain and the bottom of the FD cage. You need a clearance of 2 mm for each 1T you are gong to change by, in this case 4T, so you need 8 mm. This assumes that you are not moving the FD or changing the other two rings.

Is there a downside with the large gap between 38T and 24T? I don't believe that shifting is an issue using a friction shifter. Going down you knock the chain off the middle ring and it lands on whatever is there. Going up you press the chain against the middle ring and it climbs up onto it. I've used this ring combination on two bikes now with no real trouble. You need to be happy with the shift up and down between 24T and 38T. Highest on 24T will be (24/15)*27 = 43 inches (I call that a bit hilly, YMMV). Middle ring gear 8 is (38/30)*27 or 34 inches. That's OK there is plenty of overlap and gear 6 (23T) will give you 45 inches, about the same.

Of course the 11T top sprocket is too small and the 48/11 is just too high, for me anyway, but the only way to get something more sane while keeping the 34T is to make a hybrid cassette. That is just what 531colin did - viewtopic.php?f=5&t=54328.

Edit
Don't know what cadence you prefer but MickF above probably prefers higher gear/lower cadence than most people on here.

Another edit
The Sora is intended for 50/39 so if you depart further from this than your 48/38 you may well have more problems. Hard to be sure but CJ in Cycle reckoned that 4T was the max so maybe 46/36. I have no experience of going smaller than 48/38. CJ writing in Cycle said that the small ring is not an issue, if you do the check I've described above.

Thanks for all that. I've got Sora STIs and it's a triple crankset. In fact here's a picture of the whole fing wot I built myself:



It seems fairly clear that I can go outside Shimano's limits, as that seems to be what Ridgeback have done, by 2 teeth. The top gear of 118 gear inches is fine, but only marginally useful. Whereas the bottom of 22 gear inches might sometimes not be low enough. I know there's no shame in getting off the bike and pushing, but I'd rather not. If the trade off is not being able to go fast down hills, or pedalling faster to do so, I'd rather have that, but still be able to get up steep hills. And as I said, even with good disc brakes, much past 27 miles an hour I start to get nervous.

I had a bit of a nightmare getting the FD set up. Admittedly it's my first attempt, but if a wider range on the crankset is going to make it even harder, I'd rather not bother, and just put a whole new crankset on, with the same range, but all a bit lower. Though I do really like the middle ring of this arrangement, it does pretty much everything, with the big and small being "granny" and "let's see how fast I can go" rings.

I could see me ending up with two cranksets - my "everyday" one and my "touring anywhere" one.

Like I say, I really need to test it on a steep hill with some load on.

[Brucey]

if you run out of total capacity in the RD then then you can accept that the chain will run slack in the small-small gears, but since you never use these anyway (or shouldn't need to) this isn't much of a problem.

FWIW I have build up cassettes that go 14 to 'something big' by creating a custom cassette. This may solve your problems, since the total capacity isn't necessarily increased this way. If you have a long gear hanger (or an extender, cost peanuts on ebay BTW) then you may be able to go to a 36 or 38T sprocket.

In fact in my workshop right now I have a wheel with a modified 7s freehub which is fitted with a 14-42T 10s cassette, which I have created by modifying an 11s one. This should give a 28" to 100" gear range using a 42-52T chainset, which is enough for unladen riding.

cheers