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[GuyBoden]

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[Ian H]

You might as well use your 24" gear. It's foolproof and doesn't wear the chain out.

 

[All uphill]

I've got a 30 chainring and a 40 at the back and a sora rd with an extender from Spa works fine.

I'm shocked how often I use that lowest gear and wouldn't mind a 42 when it's time to change cassette!

 

[T4tomo]

Assuming its 11-42 then you need a capacity of 51 teeth. which you wont find. Even the new deore, set up for massive rear sprockets, only accept 41T diff and a max front diff of 10T if running a double

2nd point: WHY? Just why?

are you towing a caravan?

11-42 is generally for use with a single ring. 24-42 is a stupidly low gear, you'll be going so slow, even at high cadence, you'll probably fall off.

 

[Twilkes]

Assuming its 11-42 then you need a capacity of 51 teeth. which you wont find. Even the new deore, set up for massive rear sprockets, only accept 41T diff and a max front diff of 10T if running a double

2nd point: WHY? Just why?

are you towing a caravan?

11-42 is generally for use with a single ring. 24-42 is a stupidly low gear, you'll be going so slow, even at high cadence, you'll probably fall off.

You're not kidding, 24/42 is almost half the speed of a 34/32 at the same cadence, 4.5 mph at 100rpm.

 

[presta]

Edit: I've just ordered a gold RD extender to match the gold 42T sprocket, I have two 42T sprockets in gold.

Edit: And two matching gold jockey wheels............................nice.

It doesn't matter what colour they are, you're problem is that the total capacity of the derailleur won't accommodate a chainring difference plus sprocket difference as high as 51 teeth. The extender increases the size of the largest sprocket it will accommodate, it doesn't increase the total capacity.

 

[fossyant]

Because I have a 42T.

Edit: I've just ordered a gold RD extender to match the gold 42T sprocket, I have two 42T sprockets in gold.

Edit: And two matching gold jockey wheels............................nice.

What needs a 42T in Warrington ?

 

[fossyant]

I doubt it would work with your triple - you'll struggle with any mech and chain length to cope.

 

[Ming the Merciless]

I doubt it would work with your triple - you'll struggle with any mech and chain length to cope.

It’d work but they’d be certain combinations that would break the derailleur and likely chain. It can handle 44 front / 24 rear, 24 front / 42 rear you’ve got pretty much same take up. You just can’t have 44 front / 42 rear as things would break very rapidly possibly followed by the rider breaking as they hit the ground.

Thus while you’ve exceeded its capacity (most long cage rear capacities are around 42-45t capacity), that’s just means it doesn’t have the capacity to handle the full range of cog combinations.

 

[Tigerbiten]

On a recumbent trike you tend to push derailleur right to limit of their capacity.
So I've run a 9 speed derailleur setup with a 51t difference on mine in the past, 48-34-22 front and 9-34 back.
You must make sure it will safely run big-big just in case you shift into that combo by mistake.
If you cannot then things will break if you do shift to that combo by mistake.
Then just accept that you may not be able to use the smallest sprockets when on the small ring due to either the chain going to slack or it rubbing on itself due to how wrapped up he rear derailleur is.

Luck ............

 

[fossyant]

It’d work but they’d be certain combinations that would break the derailleur and likely chain. It can handle 44 front / 24 rear, 24 front / 42 rear you’ve got pretty much same take up. You just can’t have 44 front / 42 rear as things would break very rapidly possibly followed by the rider breaking as they hit the ground.

Thus while you’ve exceeded its capacity (most long cage rear capacities are around 42-45t capacity), that’s just means it doesn’t have the capacity to handle the full range of cog combinations.

I said that in one line... 👅 It will work one end, not the other....

 

[ColinJ]

You're not kidding, 24/42 is almost half the speed of a 34/32 at the same cadence, 4.5 mph at 100rpm.

Still a bit overgeared then!

(I would have to be producing about 550 W to climb a 25% ramp at 4.5 mph and Guy must be around my weight?)

 

[ColinJ]

What needs a 42T in Warrington ?

Guy has a standing invitation to come over here for some climbing pain!

 

[Steeler]

Not as low geared as your requirement but this uses a 30/46T chainset and an 11-42 cassette with gearing by Microshift so it might be worth looking at some of their derailleurs.
https://www.bombtrack.com/complete-bikes/arise-tour

 

[fossyant]

Runcorn has a dry Ski slope.
View attachment 636994

Looks flat...