By Ashley Guy of UtahTrikes.com
If you've poked around some of the articles I've written, checked out my blogs, or taken a test ride on one of my own personal trikes, you've no doubt realized that I'm pretty particular about my gears -- especially my high gears. The fact is I like to go fast. When I'm commuting on level ground I like to keep my speed between 20-25 MPH. When I am going downhill I like to go as fast as possible. I hate it when I run out of gears and start to spin out. For this reason I've found the stock gearing on all the WizWheels Trikes too low for my taste. If you're like me then you may be considering some different gearing options for your trike.
In this article I'll be using "Gear Inches" to indicate gear ratios so we can have a common reference point to compare the different gearing options. Gear inch (GI) is a measurement of the distance traveled by the wheel for every one revolution of the pedals. A typical mountain bike might have a gear inch range of 18 - 103 and a typical road racing bike could have 43 - 127. A good range for all around riding is about 20 - 90.
Why our gearing is messed up
A cool feature of the WizWheelz trikes is that they all feature 20-inch wheels all the way around. The nice thing about this is that you only need to carry one spare tube size, and you can have all the same tires. Having smaller wheels also makes them stronger and less likely to flex or bend when turning. The bad news is that your gear range suffers because the front chainrings and rear sprockets were originally designed for 26 to 29-inch tires for mountain and road bikes. Letís see what happens when we take the same gears and use smaller tires. For these examples Iím using the very common 11-34 rear sprocket cassette, and a triple chainring configuration with 24, 42 and 53 tooth gears.
27-inch tire w/11-34 Cassette and 24/42/53 Chainrings = 24-130 GI
26-inch tire w/11-34 Cassette and 24/42/53 Chainrings = 23-125 GI
24-inch tire w/11-34 Cassette and 24/42/53 Chainrings = 21-115 GI
20-inch tire w/11-34 Cassette and 24/42/53 Chainrings = 18-96 GI
Values derived by using the gear calculator on sheldonbrown.com.
As you can see from the results above, as the size of the wheel gets smaller the whole gear range shifts down. The result of putting a standard 11-34 cluster on a 20-inch wheel is to shift the whole gear range down 34 Gear Inches at the high-end. At the lower end the resulting 18GI actually becomes a benefit and makes it easier to climb hills. This low gearing is greatly appreciated among recumbent cyclist because we donít have the advantage of being able to stand on the pedals to get up the hills.
For the extreme cyclist, the lower top-end gearing soon becomes a limiting factor. A fairly conditioned rider may have an average cadence of 85 rpm. If we take the gear inch figure from the chart above for our highest gear, at 85 rpm our speed will be about 24 MPH. While this speed is great for just cruising around town, youíll never set any records. If you like to pedal down the hills to build up speed youíll also be limited.
While the entire gear range is lowered with our 20-inch wheels, most recumbent cyclists WILL appreciate the low gears for climbing hills. The trick is finding a way to keep the low gearing while increasing the top-end range of gears. There are a few different approaches to resolve this and all involve making modifications to your trikeís existing drive train. The ideal goal is to create a gear-inch range of about 18 to 130 GI, enabling us to climb any hills and fly down any hills without spinning out.
My current gearing
On my regular commuting trike (modified Cruiser) I have a modified 16-speed drivetrain with a gear range of 17 to 128 inches. I have never met a hill that I could not climb and I can still pedal while going down hill at 50MPH (at about 130 cadence). While these are the extremes of my gearing, I typically only use my top two gears going downhill. I spend most of my time in my 13th and 14th gears (which I call 5H and 6H). My 5H gear is 80GI and I use it for going 19-24MPH. My 6H gear is 97GI and I use it for going 24-28MPH. As you can see, my 6H gear is just a little higher than the 96GI-high-end from the stock gearing. So, why, you may ask, do I care about getting higher gearing if I spend most of my time in the 80-97GI range? Well, there is something about knowing that I always have 2 more gears, plus every day I have a couple hills that I like to go at least over 45MPH down them. Plus, I should also mention that my trike, as snazzy as it looks, is a tank! With all the accessories and baggage it typically weighs about 65lbs. So, when I get on one of the lighter trikes (like the WizWheelz RACE or WizWheelz EDGE for instance), their stock top-end gears donít even begin to push my limit on level ground.
Different Gearing Solutions
There are several ways that we can go about changing our top-end gearing. Some solutions require major modifications to your trike, while others are simpler. Also some riders may not need as high of a gear range as 130GI, so a lesser modification may be in order.
All the WizWheelz trikes come with a standard rear hub wheel that has an 11-tooth sprocket as the highest gear. So first Iíll talk about making some modifications to the front chainrings and derailleur and leaving the rear end alone.
Getting A New Front Chainring
Since most of our trikes will have a triple chainring of 24/42/53(or 52) the easiest modification to get our gearing would be to swap out our largest chainring for an even bigger one. Since our low-end gearing is determined by the 24-tooth chainring it would stay the same. So first letís use some math and figure out what size chainring we would need to get a 130GI top end with our 11-tooth rear sprocket. Using Sheldon Brownís calculator again I find that we will need a 72-tooth chainring. Hmm. I immediately think weíll have a problem with that. First, I tried finding one online and had a hard time locating one. Second, a 72T chainring would not work with our derailleur. Third, a 72T chainring would create an extreme angle in our chain line, and unless we also have the TerraCycle Idler up front, it would rip the stock idler to shreds pretty quickly. Fourth, a chainring that size would be like a huge saw blade and would eventually catch the hair in your leg and rip it out.
So, if we canít go with such an extreme-sized chainring, letís see what we can do. WizWheelz uses all Shimano front derailleurs. Depending on the model trike that you have it will be equipped with the Sora, Tiagra, or Ultegra. According to the Shimano website, the Sora is already maxed out with a 52T chainring. The Tiagra and Ultegra derailleurs will accept a 56T chainring. Fortunately, 56T chainrings are easier to find and they run about $70. So, if we go with a 56T chainring what will it do to our gear range? Letís see:
20-inch tire w/11-34 Cassette and 24/42/56 Chainrings = 18-102 GI
So, if we change nothing else but the larger chainring weíll go from 96GI to 102GI. Doesnít sound like a lot, but letís see what kind of speed changes we could see. With an 80RPM cadence we would see an increase of speed from 23MPH (53T) to 24MPH (56T). At 120RPM cadence we would see a difference of 34MPH (53T) to 36MPH (56T). So, in effect we are looking at $70 to pick up an extra 1-2MPH potential speed increase. Better than a $500+ fairing, I suppose.
Cost: $70 or less.
Pros of 56T chainring:
56T chainring is easy to find.
Works with Tiagra and Ultegra derailleurs.
Easy to upgrade, with minimal modifications to trike.
Cons of bigger chainring:
Does not work with Sora derailleur
Does not get us up to 130GI
Larger than 56T chainrings hard to find or requires major modifications.
For details on installing a larger chainring click here.
Our next entry in the front-end category is the Schlumpf High Speed Drive. I really like this drive a lot. Essentially, it eliminates the entire set of chainrings, front derailleur, and shifter and replaces them with a new single chainring with overdrive. The chainring on the standard Schlumpf HSD is a 27-tooth sprocket. Inside of the drive there are internal gears which, when activated, make the chainring turn 2.5 times for each pedal rotation. This has the effect of giving you a virtual 2-chainring setup with a 27T on the low side and a 67.5T on the high end. Oh yeah, try finding a 67.5T chainring out there! Not gonna happen. So letís plug in our numbers and see what we get:20-inch tire w/11-34 Cassette and 24/67.5 Schlumpf HSD = 16-123 GI
Wow, so we even get a slightly lower end, and our high-end gearing is looking pretty nice. Letís check out our speeds again. With an 80RPM cadence we would see an increase of speed from 23MPH (Stock 53T) to 29MPH (67.5T Schlumpf). At 120RPM cadence we would see a difference of 34MPH (Stock 53T) to 44MPH (67.5T Schlumpf). Wow, with those numbers I think we could stop and keep most people happy, but there still might be some hills you canít pedal down, so let's keep going.
Cost: $499 plus assembly
Elegant solution, replaces entire front derailleur and chain rings.
Eliminates possibility of cross chaining.
Small 27T chainring promotes nice chainline.
Easy to swap cranks for different sizes.
Gives even lower end gearing.
Can be shifted when stopped.
Needs to be installed with special tools.
Internal gears are only 95% efficient.
Front End summary
So, in the front we have a couple of solutions available. Going with a 56T chainring is easy enough if you have a front derailleur that can handle it. If you are riding near your limit with the 53T chainring, then getting the extra 2MPH from the larger chainring might be worth it to you. The Schlumpf High Speed Drive provides a very nice gear range and eliminates the need for some other components. It is fairly costly though and does provide a slight loss in efficiency. The nice thing about these Front End options is that they CAN be combined with other rear end options.
Rear End Gearing Solutions
The stock 11-34 MegaRange cassette found on most stock trikes gives us 8 or 9 gears (depending on the cassette) and a pretty good range. In order to get a higher top-end gearing we need to change the gearing more than what the 11T sprocket can do for us. The problem is that the smallest sprocket that will fit on the standard Shimano-style hub is the 11-tooth sprocket.Internal Hubs - Shimano Nexus 8
Iíve been a big fan of internal hubs for a while, particularly the Shimano Nexus 8, so that is the one Iíll be talking about. Internal hubs have just one sprocket for the chain and different gears internally. Each gear, when selected, rotates the wheel by a factor of the connected sprocket. The smaller the connected sprocket, the higher your top-end gearing will be. The smallest sized sprocket for the hub that I could find required some modification and is a 17T. Letís crunch the numbers:20-inch tire w/17T Nexus 8 Hub and 24/42/53 Chainrings = 15-100 GI
Here we see an even lower bottom end, and just a slightly higher top end. With an 80RPM cadence we would see an increase of speed from 23MPH (Stock 11T) to 24MPH (17T Nexus 8). At 120RPM cadence we would see a difference of 34MPH (Stock 11T) to 36MPH (17T Nexus 8).
If we could find or modify or find an even smaller sprocket like a 16T our top end would get even higher.20-inch tire w/16T Nexus 8 Hub and 24/42/53 Chainrings = 16-107 GI
20-inch tire w/15T Nexus 8 Hub and 24/42/53 Chainrings = 17-114 GI
Cost: Hub, wheel, shifter, and idler/tensioner is $500-$600.
Shift at anytime Ė rolling or stopped.
Easy to play with different ratios.
Need a whole new wheel.
Need to run an addition idler or modified derailleur to take up chain slack.
Need to change shifter.
May need to modify mount to get it in.
May need to modify the sprocket.
Only 80-95% efficient compared to derailleur.
While it appears that there are more cons than pros, I still love this hub. Being able to shift at any time, while not a focal point of this article, is a huge benefit. The gear range is good and can be moved up or down to suit your own preference by just changing a single rear sprocket.
The Shimano Capreo system is relatively new, and was designed especially for small-wheeled bikes like folders and recumbents. Essentially they made a new hub that works with a modified-type cassette and has smaller gears. The standard setup has a nine-speed 9-26T cassette. The smaller 9T sprocket will give us a higher top end so letís see what the calculator says:20-inch tire w/9-26 Capreo Hub and 24/42/53 Chainrings = 18 -118 GI
Those numbers are pretty good. With an 80RPM cadence we would see an increase of speed from 23MPH (11T) to 28MPH (9T). At 120RPM cadence we would see a difference of 34MPH (11T) to 42MPH (9T). My favorite thing about this setup is that all the modifications are made to the wheel, and not the trike itself. You can just pop the wheel off and replace it with the stock one if needed.
Cost: Hub, cassette, wheel w/assembly about $200-$300 depending on the wheel.
Does not require a different derailleur if you have a 9-speed.
Only works with 9-speed derailleurs.
Requires new wheel.
Currently hard to find in the US, so you may have to import it.
While there may be other solutions available that others have tried, I only wanted to talk about things that I have tried. I am currently working on one more exciting option and that is mounting a 26-inch wheel on the back of a TerraTrike. More details on that to come soon.
In the meantime, we can get even better results than those mentioned above when we combine the front-end modifications with the rear-end solutions. I personally have trikes set up with two combinations as detailed below.
All Internal Gears
My main commuter trike is a Cruiser
equipped with both the Schlumpf HSD and the Shimano Nexus 8 Hub. This completely eliminated derailleurs for me and with a nifty idler mount from TerraCycle I donít even need a chain tensioner. I can shift at any point, even while stopped or coasting, which makes riding in traffic much easier. The Shimano Hub is most efficient in 5th gear because none of itís inner gears are used at that position and the sprocket is locked to the hub. I played around with different sprockets and found that a modified 17T was best for me. So crunching the numbers I get:20-inch tire w/17T Nexus 8 Hub and 27/67.5 Schlumpf = 17-128 GI
Cost: About $900
Only one shifter.
Can shift at anytime.
Great gear range.
Less efficient due to all the internal gears.
Requires major modifications.
Slightly heavier than stock gearing.
While being less efficient, this combination really gives me the high gearing I like for going downhill, while still giving me the low end to climb any hill. There are certain gears where the two internal gears vibrate together and I hear a rumble sound, but overall I donít notice that it is terribly inefficient.
Bigger Up Front/Smaller In Back
My fast racing trike is a WizWheelz Race
running a 56T chainring up front and the Shimano Capreo gears in back. While I donít get quite the gear range that I have on my Cruiser, it is a marked improvement over the stock gearing. Being a much lighter trike (and not loaded with as much stuff) I donít need the low-end gears because it is much easier to go up hills. Also, because it is a lighter trike gravity does not help me as much going down hills. I still spin out at about 47MPH with this set up, but overall it is much more efficient and WAY cheaper than the Schlumpf/Nexus combination. Here are the numbers:20-inch tire w/9-26 Capreo Hub and 24/42/56 Chainrings = 18 -124 GI
Cost: About $270
Cheapest solution to raising your gears.
Uses all stock derailleurs.
Gear range still not quite high enough.
Until next time
Once I have the results of the big wheel modification Iíll let you know!