Short drop deralier for 20" wheel trike

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UpWrong
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Re: Short drop deralier for 20" wheel trike

Postby UpWrong » 9 Mar 2018, 9:09am

I've not found this to be a problem, particularly if you use a taller tyre. Presumably a medium cage RD would improve clearance. My Metabikes came with a 9-speed medium cage Tiagra RD operating on an 11-28 cassette with 30-39-50 rings up front and I could use all the gears ok. So total capacity of 37 teeth. If that's enough range for you then you might consider it.

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Tigerbiten
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Re: Short drop deralier for 20" wheel trike

Postby Tigerbiten » 9 Mar 2018, 6:12pm

It's not really a problem unless you do a lot of true off road cycling.
Most tracks have a section you can cycle down to keep the derailleur safe.
I also found that to a degree you can work around it with the correct choice of chainring/sprocket.
Some combos will tuck the derailleur up better than a different combo which would give you the same gear inches.

Grass isn't that bad as it just disintegrates, twigs are a lot worse as they don't ..... :lol:

nigelnightmare
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Re: Short drop deralier for 20" wheel trike

Postby nigelnightmare » 3 May 2018, 12:30am

OldBloke wrote:Another thing to be aware of is that Shimano style rear derailleurs (RDs) for road have different shifter requirements to MTB RDs. If you change between road and MTB RDs you will also have to change shifters. I think this applies to 9, 10 and 11 speed RDs, not to 6-8 speed.

As far as I know SRAM derailleurs don't have the same problem.

:)

Ken


AFAIK
All current and recent shimano RD's have the same pull MTB & Road (excluding 11 speed).
Shimano FD's are different, so you can't use "MTB" shifters on "Road" cranks/rings and FD's and vice versa.

This is what I've read and been told (not from personal experience or trial).
==========================
I've also found that crossing the rings (i.e. big front/ small rear & vice versa) doesn't cause the same problems on a recumbent trike as it does on a DF upright bike (the gap between the cranks and rear sprockets is about 3 times the distance or more).

So it is fairly easy to select a gear combination for the desired ratio in which the rear derailleur is not vertical ( thus increasing the gap between the RD and the road).

I run a 55/42/30 front and 9/34 9 speed caprio rear with a Shimano Deore mega range derailleur and the closest to the ground is level with the wheel rim approx 40mm gap and that's in first on the granny ring, about 44mm on the middle ring and 56mm on the big ring. 406/40 tyre
When you start going into higher gears the derailleur moves further from the road surface so the only time you're likely to encounter problems is when you are going at your slowest.
And if you are OFF roading you are more likely to get twigs and things in the spokes more than the rear derailleur as they are almost stationary with the ground at their lowest point i.e. where the tyre makes contact with the ground, at least that's been my experience.
HTH

OldBloke
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Re: Short drop deralier for 20" wheel trike

Postby OldBloke » 3 May 2018, 12:37am

nigelnightmare wrote:AFAIK
All current and recent shimano RD's have the same pull MTB & Road (excluding 11 speed).
Shimano FD's are different, so you can't use "MTB" shifters on "Road" cranks/rings and FD's and vice versa.



10 speed road are definitely different to MTB. When I changed to MTB derailleur I also had to change the shifter.

Ken

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Tigerbiten
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Re: Short drop deralier for 20" wheel trike

Postby Tigerbiten » 3 May 2018, 3:43am

nigelnightmare wrote:And if you are OFF roading you are more likely to get twigs and things in the spokes more than the rear derailleur as they are almost stationary with the ground at their lowest point i.e. where the tyre makes contact with the ground, at least that's been my experience.
HTH

If your in long grass then the back wheel pushes the grass out sideways before the chain feeds it into the lower jockey wheel.
That's been my experience.

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[XAP]Bob
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Re: Short drop deralier for 20" wheel trike

Postby [XAP]Bob » 3 May 2018, 8:55am

Tigerbiten wrote:
nigelnightmare wrote:And if you are OFF roading you are more likely to get twigs and things in the spokes more than the rear derailleur as they are almost stationary with the ground at their lowest point i.e. where the tyre makes contact with the ground, at least that's been my experience.
HTH

If your in long grass then the back wheel pushes the grass out sideways before the chain feeds it into the lower jockey wheel.
That's been my experience.


Yep - you can collect an awful lot of grass very quickly.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

nigelnightmare
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Re: Short drop deralier for 20" wheel trike

Postby nigelnightmare » 4 May 2018, 6:06pm

I tend to avoid riding through long grass for that very reason. :roll:

But a swiss army knife soon sorts it out. :wink:

Even on my other recumbent's with 700c rear wheels the rear derailleur is only 170mm from the ground about 6 3/4" in old money so that long grass at the edge of some cycle paths still catches and gets tangled.

I suppose the main thing with the OP's question is a short cage rear derailleur is only around 15-20mm shorter.

So he won't be gaining much more ground clearance coupled with the restricted gear range that goes with it.

eddiewalkling
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Re: Short drop deralier for 20" wheel trike

Postby eddiewalkling » 19 Jun 2018, 10:50pm

I love to ride my trike off road, not what they were necessarily designed for but tadpoles are very good at it in my experience. I have worried about RD ground clearance with good reason due to running a 36 tooth cassette. In practice it has been little problem. It has restricted tyre choice but not caused reliability issues. I do have to pick out things yes, but that happens in spokes just as often. I'm glad I didn't go for the Rolhoff option for clearance alone, I have a lower gear ratio than possible with their hub gear and can replace my drive chain about 9 more times before reaching its original price tag.

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Tigerbiten
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Re: Short drop deralier for 20" wheel trike

Postby Tigerbiten » 20 Jun 2018, 12:58pm

I looked into how to get ultra low gears with a big range when I had my trike built and they are both easier to get with a Rohloff.
Lowest chainring-sprocket ratio is now 1.9-1 which will give you a around a 10 inch gear with a 20" wheel.
You need a 40t sprocket with a 22t chainring to match it using derailleurs.
A 26-38-50 triple with a 13 sprocket on Rohloff built into a 20" wheel gives you 10.4"-105.4", which is also the biggest easiest built range.
A 30-44-56 triple with a 15 sprocket also works to give you almost the same range.
To get a bigger range means adding another set of gears like a dual drive or a Schlumpf drive.

Tilley
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Re: Short drop deralier for 20" wheel trike

Postby Tilley » 20 Jun 2018, 9:03pm

Well I upgraded my drive train by retaining the 44,32,22 chainset and fitting a Sturmley Archer 3 speed cassette hub with a close ration 12-26 9 speed cassette allowing me to fit a Shimano Sora short drop rear derailleur. I have achieved more ground clearance for the chain but I have also got a much smoother and evenly progressive gear choice. the combination of the cassette and the SA hub gear gives me an equivalent gear range of 9 - 35 However the 12 -26 cassette and chainset combination allow me to ride most of my normal routes without resorting to using the hub gears. So in general I can ride with the hub gear in 2nd which results in a 1:1 drive. The added advantage is that should I make a poor derailleur gear choice I can always switch to the lower hub gear and keep moving and because the hub gears can be selected when stationary I can even do this if I have come to a grinding halt. Ok the hub gear has added almost1.2 kg to the centre of the wheel but on a recumbent trike that isn't really a major concern.

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hoarder
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Re: Short drop deralier for 20" wheel trike

Postby hoarder » 20 Jun 2018, 9:34pm

Can we have some pictures please, Tilley ? I'm sure I'm not the only one who'd like to see what the position of your new rear mech is when the cage is vertical. Do you notice the additional weight - have you found any negatives from making the change ?

For me it'll be useful to see, I'm considering the same upgrade. Why ? Well, I have had to replace my ICE Adventure 20" rear mech hanger twice due to hitting ground obstacles (one time near immobilised me with the lower cage twisting into the spokes :shock: ), and more recently having to strip and clean the whole drivetrain after an off-road ride took me through numerous sandy patches (where the mech and chain tubes got submerged in the sand).

I too like taking my trike off-road, but I'm getting sick of the maintenance required because the clearance is frequently inadequate. :(

eddiewalkling
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Re: Short drop deralier for 20" wheel trike

Postby eddiewalkling » 21 Jun 2018, 3:23pm

[quote="Tigerbiten"]I looked into how to get ultra low gears with a big range when I had my trike built and they are both easier to get with a Rohloff.

Sure, but that would be running it outside of the warranty? I have read that in practice this means little as they are so well made, but it would make me too nervous given the cost. I think max they allowed was 22 32. I like my 20 36 too much to change.

Having said that, when I need a new rear wheel built I will be getting the SA hub for sure. Heard good things about it here.

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Tigerbiten
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Re: Short drop deralier for 20" wheel trike

Postby Tigerbiten » 21 Jun 2018, 8:05pm

If your running a 20 chainring to a 36 sprocket then you've probably got the same first gear as the lowest recommended by Rohloff, very close to two turns of the pedal to one turn of the wheel.
I'm actually running a slightly lower first gear than Rohloff recommended, 1.8:1 chainring:sprocket ratio versus the recommended 1.9:1 ratio, 38/21 vs 40/21.

When I got the trike built by ICE, the whole aim was to maximize the gear range starting from just sub 10".
A standard derailleur setup didn't give me enough of a range.
But with only one hand, the option of a dual drive with a wide triple would have ended up with too many controls on one handlebar.
So I ended up with a Rohloff and a Schlumpf HSD, which I've since added twin chainrings to which helps the transition into the overdrive mode, 9.4" first gear with a 1900% gear range.

Tilley
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Re: Short drop deralier for 20" wheel trike

Postby Tilley » 21 Jun 2018, 9:35pm

Ok so I'm struggling to attach/insert Photos if someone could simply describe how best to achieve this I will happily post some taken tonight. Meanwhile the minimum clearance I have achieved from ground to the underside of the rear derailleur hanger is 65mm or in old currency 2.5 inches.
Image Attachments
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Tilley
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Re: Short drop deralier for 20" wheel trike

Postby Tilley » 21 Jun 2018, 9:36pm

Ok so I cracked it here are 2 more photos.
Image Attachments
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