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.
A good pun is it's own reword

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.