Camilo

I'm starting to home in on what I'm looking for in a tadpole trike and what some options are (see my post on suspensions). Can you pick apart my logic on gearing and rear wheel size. I am kind of analyzing in a vacuum, although I do understand the gearing on my road and mountain bikes.

The executive summary: It's easier to get much lower gears on 700c wheeled trike than it is to get much higher gears on a 20" trike. There may be other factors such as stability and smooth ride that should be considered.

Read on...

Given the same crank and cassette, I understand that 20" drive wheel will result in a much lower low gear as well as a lower high gear compared to a 700c. It seems like 50-39-30 and 11-34 cassettes are fairly standard. I know what high and low gears (and gear inches) I need for my road bike to be comfortable in the hills I have around here and I'm assuming I'll want quite a bit lower gearing with the trike.

But I'm also concerned, to a lesser extent, about high gearing, again roughly comparing to my road bikes. I don't need to meet or exceed the high gearing of my road bike but I don't want it to be a huge difference.

I've been using some gear inch calculators and I'm thinking it is pretty easy to get much much lower gears on a 700c bike because of commonly available mountain bike triples. (one of which I can scavenge from my stable). For example, a 26X34 low gear is a lot (lot!) lower than my road bikes and within a gear inch or so to the 20" trike at 30X34.

For what it's worth, I understand rear derailleur specs - largest sprocket and chain wrap - so know I have to pretty much stay within those specs. Also for what it's worth, the effort of doing this modification is not a factor, I like doing it and have the tools and know-how to change cranks and chain wheels, etc.

On the other hand, there is not a heck of a lot that I can do with the high gearing on any bike or trike. You can't commonly get a smaller cassette sprocket than 11t. You can go up as high as 54t for most road triple cranks, depending on the chain wrap capacity of the rear derailleur. But from the calculators, even with the 54t ring, it seems to me, I would probably not be happy with this. It's not even close to what I'm used to. I'm certain I'd be unhappy with the stock 50X11 with 20" wheel.

So, am I thinking straight? That I can probably get a 700c trike nearly as low as a 20", but I can't get the 20" even close to the high gearing on the 700c? Has anyone gone through this sort of thing?

And, are there other factors II should also think of? For instance, the longer wheelbase 700c vs the shorter wheel base 20". Which would generally be more stable at speed going down hill? Which size wheel, in general, would tend to roll smoother over stuff you generally encounter on paved roads ( know that tire volume and PSI matters a lot here,).

I appreciate any comments you have!

79pmooney

Google time trial cranksets. I don't know what you will find but BITD there were some enormous chainring made. You could run a tandem drivetrain if you can install your derailleur and a BB to something in the middle of the trike. Run a single leftside 50 tooth off your pedal crankset and a 36 tooth leftside on the middle crankset. Run your regular (say) 50-35 on the right. A "timing chain" using 50 to 36 brings your gear rations to normal. I think that second BB needs to be an eccentric tandem BB so you can dial in the chain slack.

50/36 = 1.39 ~= 27/20 = 1.35

Now, that second crankset probably wants to be exactly where you are. And it is expensive and not light. (Not light? A plus going downhill!)

This stuff s fun to think about. I might get some more ideas lying in bed.

Ben - the guy who designed and built a triple chainline fix gear with three radically different gears for days in the mountains. Three 1/8" chainrings on a double crankset with a low Q-factor. Odd - yes, but it works really well. Yes, you do have to stop and pull out the wrench. It is a fix gear and there is no magic.

gobent

They’re pretty expensive but the Schlumph Speed Drive might be your ticket.

BlazingPedals

My preference would be low gears on a big wheel. But since I bought used I ended up with a 20" rear wheel. The trike has a 58T chainring on it. That's a little low by road bike standards but I doubt I'll need more because the trike is slower anyway.

Trsnrtr

I owned Speeds and when I did, I ran a 55 ring up front on a double crank. I don't remember the little ring size or the largest rear cog but I was just outside of the "wrap" spec and it worked fine.

My current machine uses a 700 rear wheel with a 50/36 up front and an 11x30 rear.

And, before anyone asks, my average speeds are identical. To be honest, I like the little rear wheel better because it accelerates from a stop like a jack rabbit. On the other hand, the bigger rear wheel trikes do ride a little softer without suspension. As for stability, it's more a function of design than wheel size. My Speeds cornered like they were on rails.

For the record, I've owned 2 Speeds, 2 700s, a VTX, a Vortex, an Expedition, a Windcheetah, and an older Road.

VegasTriker

In your previous post you mentioned that you were in the market for an entry level trike. The trikes with decent gearing and a wide range are not entry level.

I'd suggest you use the Mike Sherman (Mike Sherman's Bicycle Gear Calculator) or Sheldon Brown (https://www.sheldonbrown.com/gear-calc.html) gear calculators to make exact comparisons between different drive train combinations. If you use Mike Sherman's calculator and do the calculation for Catrikes with the 30/39/52 chainrings and 11/36 cassette will be: 20" drive 15.9-90.1 gear inches, 700C drive 20.9 - 124.2 GI. The latter is about what you find on many road bikes.

I also own an older Greenspeed GTO which has a single 65 tooth chainring and Schlumpf Mountain Drive in the front and SRAM dual-drive 8 speed in the rear. If I recall correctly, the gear range is around 14 to 140 gear inches. SRAM no longer makes the dual-drive rear hub so this combination is not available today. It was a system that always had a gear range to suit the terrain even on the steepest of hills. It is very expensive to duplicate something that gives you a similar gear range. This was about a $5K trike when still available.

When you first start out trike riding you will probably need lower gears compared to what you need after you get your "trike legs". My first trike had the 19-90 GI drive and I needed the low gear range but after riding for a few months consistently I wanted something more on the high end but didn't need the low end as much. These days I ride my 2013 Catrike 700 in the middle chainring almost all of the time which means a 28.5-93.2 gear inch range suits me just fine. That would have been tough when I first started out.

dorkypants

Shimano makes a 9-speed Capreo hub and cassette for small-wheeled bikes that goes down to a 9-tooth small cog. Bike Friday modifies the Capreo hub to take a 10-speed cassette (don't know whose Shimano freehub spline pattern compatible cogs BF actually uses).

Camilo

Interesting... Is that a 58t single crank? Do you know what the BCD is?

When I did a quick search for chainrings for a 130 BCD crank (which I assume is what the standard triples are), I only saw 54t as the largest.

Camilo

Thanks. Your experience helps put it in perspective, which is what I need.

I did use a calculator to compare a gear ranges with the difference being the wheel size. The numbers I got were similar to yours except that I was using a 34t cassette. Using the 20" wheel with what looks like a fairly standard stock 30X34 low gear (~18 gear inches) as the benchmark .... the 26X34 with the 700c wheel is about 20 gear inches, and would allow me a 48t large ring within easy RD specs - and a high enough high gear. 20 would be close enough for me and if not, I could go with either a 24t chainwheel or a 36t cassette, depending on price and RD capacity. My road bikes all have a 34X28 low gear which the calculator showed at 32. So the ~20 gear inches that seems easily achievable is quite a bit lower, and I'm thinking would be OK. If not, again, I get down a couple more gear inches pretty easily pretty cheaply. Especially since I have two 9 speed bikes in the stable and therefore no cassette take off is wasted! 8-)

BlazingPedals

No, that's a standard 30/42/52, 130 BCD triple with the 52 replaced by a 58. I had to go to aliexpress to get it because I wanted it to be pinned and I couldn't find anything domestically. 42/58 seems to shift OK, but the derailleur's not made for that combo and will probably not shift directly from 42 to 30. If I need the granny (unlikely around my home range at least,) I'll have to start in the big ring and shift all the way down at once.

Edit: Nope, it won't shift from 42 to 30 because the shift ramps on the front derailleur don't go down far enough. But it shifts from 58 to 30 just fine. I rarely use the 30 (I can get down to 25 gear inches without the granny ring) so I'll probably leave it as-is.

Leisesturm

SRAM made Dual Drive hybrid IGH/Cassette rear hubs in 8,9 and 10 speeds plus 3sp planetery gear. Sturmey-Archer continues the tradition. That's what I would do if I wanted both a high gear in the 100 teens and a low in the low teens or even high single digits. The Sturmey-Archer 3x8/9/10 is under $100 for the hub without cassette! Laced into a decent 20" rim ... <$200.

osco53

I just don't understand needing so many gears. I climb very steep loose stuff and ride smooth pavement
with my 2x10 with 13.5" to 79" gear Inches. More gears to me just means more overlapping.
a 27 speed has what,,16 actual different gears ?? I dunno.,
I get plenty of flat road speed at a 90 rpm cadence. If I wanted more Id do a triple up front.
I mostly use 5 or 6 of my 10 gears anyways..My Tour Easy had 27gears, I used about 9 of them.
Not knockin,, just a different perspective..
Just sayin.

rydabent

This is not a big deal. There are many chain ring sprocket available and the same with rear cluster gears. You can pretty much pick the gear inch range you want.

Juan Foote

I owned a set of 20" wheeled Catrikes. The biggest thing I noted about having a trike was how hard they are to climb with. As a result, I wanted low gear inches, even less than what the bike offered. I added SRAM internally geared hubs to each bike. I think they were called Dual Drive or something. So far as I know they have been discontinued but am sure there is something similar on the market. The lowest gearing was incredibly low, full cadence resulted in something like 1.5 MPH or somesuch if I recall correctly. The tallest gearing was pretty stout. I noted here that the bigger problem wasn't the gearing so much as beam flex on the cranks.
One thing of note with the 20" wheels is that it was very easy to get stuck/spinning on loose dirt or wet on a hill and such. I can only imagine that the larger rear wheel models have less issue with that aspect.

Camilo

I settled on the Peformer JC70 trike with the 700c drive wheel. I followed the gearing rationale I came up with above, and I think it will be sound. It will be easy enough to get both the low and high gears I think I will need. Now that I've ridden it a bit, I probably could have done it with the 20" wheel too. But I'm happy with the 700c.

In my time frame without any local dealers, Performer with it's unassembled, free shipping sales modelwas really the way to go and I'm happy with it so far. But I like putting bikes together, and this had some new stuff to figure out.

BlazingPedals

Adding an IGH is nice, not so much for the number of gears you get but for the range you can get. It does add complication to the handlebars, though.

Camilo

Yeah, after riding around 100 very hilly miles and some flats around here, I think I do need quite a range. For now, a change of crank to a 46 35 24 triple with the 11-34 cassette will work, but with a lot of effort going up the steepest hills - partially caused by not being in good cycling shape. Rolling hills and inclines are just fine. I've probably forgotten that the particular hills that challenge me also challenged me on the bikes in the early season (I haven't ridden since last fall). I think it will work OK though as I get in better shape and more patient and accustomed with the slow uphill speed.

I've found that I don't think I need the high gears that I use on my road bikes (50X11). Probably even a 46t big ring would do. I'm not comfortable pedaling at high speed, say above 25mph, while I pedal comfortably beyond 30mph before coasting on the bike.

There's some sway in the trike when I pedal at that high speed - I'm pretty sure it's technique-related. I need to smooth out the pedal stroke; it's different than a bike, and seems to be getting better when I concentrate on it. The sway isn't as noticeable at lower speeds and doesn't bother me until I get going faster. So I tend to coast sooner than I would on the bike.

It coasts "on rails" on the fast downhills and is very stable and fun. 41.2 mph so far, while easing into the speed, being careful and testing the brakes! I have done 45+ on that particular hill on the bike, so I'm not concerned with going any faster on the trike. =8-0 (going up that hill is one of the challenging ones!)

adamrice 

I also used to have a Speed, and replaced the big ring on the triple with a 55t. It shifted fine, and I did not feel under-geared.

SRAM has taken an interesting approach with their latest road groups, with smaller gears on both the cassettes and crank. You could put together a 50x10 top gear and a 37x36 low gear, which would give you a pretty good range from a double.

BlazingPedals

I don't like using anything smaller than 14 teeth in normal practice. Efficiency starts dropping a slight amount at 13 teeth, and more precipitously starting at 12 teeth. Ten teeth? <shudder> I can't imagine that'll ever be popular except with the type of cyclists who doesn't go fast but likes the ratios that a 10T gear can produce.

adamrice 

I've never used SRAM's stuff, but according to them, the drop in efficiency is trivial. FWIW.

How many teeth are on your derailleur pulleys?

BlazingPedals

Of course they'd say that. Jockey pulleys aren't on the drive side.

Steamer

Not a valid comparison due to the wildly different chain tensions between the two scenarios.

adamrice 

Here's an independent test comparing SRAM's AXS drivetrain with Shimano's. Clearly there is some efficiency loss, although it's up to each of us to decide how significant that is. If we were really worried about losses, we wouldn't put up with the losses associated with a third wheel..

osco53

I live by the "KISS" methodology.. You Know, Keep It Simple ssss,
My 24 inch tire Terratrike Rambler ALL terrain,, The thing to note is the regular road Rambler version is changing to 24 " wheels.
My Gear Inch range with my 2x10 is something like 13.5" to 79" but my trike is to me a Gravel grinder, perfect gearing..
On road I'd want something like 15" to 90"

If I wanted fast I'd do a Cat Trike 700 or something,,
You sure you can actually handle Gear Inches above 100" ??? If so your choice should be simple,,
Now go back and consider my first line in this post for just a second longer than the first time You read It..

Surubi

You must analyze where you ride, your weight, trike weight and your conditioning.. If your area is hilly, the 20" wheel giving lower gears would be advantageous. If flat, you might want bigger for more speed. If you face many intersections and traffic controls the smaller wheel will give better acceleration, which is handy for stop signs. I have owned several recumbent trikes, and the best one, gearing wise, for city and mixed riding was an 81 speed Greenspeed with 16" wheels. I always had the right gear for any situation, and could accelerate away from a stop sign quickly.