Bike Wrenching for Paracyclists:
To begin, a shout-out to Leon Bostick who suggested a handcycle maintenance class. Leon, thanks for the inspiration and may this blog suffice for now.
Questions, comments and suggestions for further how-to topics can be sent to me at g_damerow(at)yahoo.com
To begin, a shout-out to Leon Bostick who suggested a handcycle maintenance class. Leon, thanks for the inspiration and may this blog suffice for now.
Questions, comments and suggestions for further how-to topics can be sent to me at g_damerow(at)yahoo.com
From December 14-30, 2011 I am a semi-finalist in the Hartford Achieve Without Limits contest. Enjoy the blog and I would appreciate your repeated votes at the facebook link!
http://www.facebook.com/TheHartford?sk=app_284266101605194
Note: Some maintenance topics will apply to both adaptive and conventional bikes. Those topics that are unique to a given adaptation will be noted.
Handcyclists who are set on doing most or all of their own work, may find it helpful to have a table to set their ride upon to ease access when they work. Something as simple as a sheet of plywood set on saw horses can suffice. Riders of uprights will probably want to invest in a mechanic’s stand to save their knees.
Part 1: Derailleurs, Cables and Shifters
I still remember my first drop handle-bar ten-speed. It was a blue framed Huffy with gumwall blue tires, metallic paint, and as I came to learn, had the weight of an Abrams tank. While the Loti, Cannondales and Schwinns of my cycling club buddies rode flawlessly down the road, I was usually on the curb, putting the thrown chain back on the sprockets and wondering why the bike never shifted right. I was glad to have the Huffy, but if I knew then what I know now about shifters, cables and derailleurs I would have spent a lot more time riding happily!
A thrown chain can ruin a perfectly good ride, club race or championship winning charge. So what do you have to know to have a reliable shifting bike?
Proper Derailleur Adjustment
(Note: In handcycling the Rear derailleur is known as the Bottom. The Front derailleur is known as the Top derailleur. Sounds like a description of a game of cricket, no? However, for the discussions here I will refer to a derailleur as a chainwheel derailleur or cassette derailleur)
Make sure the basic derailleur settings are correct. Chainwheel derailleurs and cassettes derailleurs have two stop screws: One screw limits the top position and the other limits the bottom position of the derailleur.
Top Limit Adjustment. Common symptoms of a poorly set top limit screw are a chain that rides over the largest gear and onto the axle or crank. Turn the top screw in until you feel a slight resistance in the shifter when shifting into the largest gear. The resistance indicates that the screw is preventing the derailleur from pushing the chain too far. If you cannot shift fully into the largest gear or the chain will not stay on the large gear but drops down onto the next lowest gear, back the screw off slightly. When possible, shifting adjustments should be made on an indoor trainer when possible to simulate riding conditions.
Bottom Limit Adjustments: Cassette derailleurs that randomly skip the chain on and off the smallest gear or refuse to drop below the second to last gear may require the bottom end set screw backed off slightly. Adjust the screw until the skipping stops and the chain runs noiselessly on the smallest sprocket.
Note: A worn, kinked, mis-routed or badly adjusted shifter cable can also cause skipping on the bottom end, so if backing the screw out all the way does not stop the skipping, inspect the cable then adjust or replace it.
Chainwheel derailleur bottom end stop screw setting: The goal is to have the derailleur pull the chain down to the smallest gear without having it pull the chain off the small sprocket.
Also keep in mind that if after properly setting the top and bottom screws, replacing the cables and properly adjusting the cable tension, poor shifting symptoms persist, then you may have a bent derailleur bracket or a chainwheel derailleur that is worn out or loose.
“Front Derailleurs operate in defiance of good engineering principles.” -Theodore Costantino. (Have you ever observed and contemplated the action and motion of a front/top derailleur? Watching the chain move back and forth often makes me a constant skeptic!) Even properly adjusted front/top derailleurs do not like to be shifted while under heavy loads and will often misbehave if you do not let off on the torque and allow them to do their job. When upshifitng, or even downshifting be sure to lay off the power slightly!
Shifters
Modern index shifting has revolutionized cycling in the same way that electronic shifting is about to change it again once more. Having said that, reliable index shifting depends on a properly adjusted cable and derailleur. On the spot adjustments while on the road can be made with the barrel adjuster on the end of the shifter but when the adjuster reaches it’s limits as the cable stretches it becomes mandatory to re-set the barrel adjuster and adjust the cable.
Shifter Preferences
I am not a fan of rotary/twist style mountain bike shifters (There I said it! I feel so much better now!) Twist shifters are simple, you twist to the right gear and the shift happens. Usually. Twist shifters tend to be less tolerant of sloppy and worn cables and so while you may think you have shifted into the right gear you know by the sensations on the cranks that the shift did not happen. The reason I prefer paddle shifters is that most paddle types have a small gap between shift points which allow the rider to go slightly past the intended shift point and so get a balky derailleur into the desired gear. However, a rider’s hand dexterity may determine the choice of shifter to be a twist. In cases where a twist shifter is required, shifting reliability may increase by the use of compressionless cables housings. (Sometimes known as “SIS”)
Note: Some maintenance topics will apply to both adaptive and conventional bikes. Those topics that are unique to a given adaptation will be noted.
Handcyclists who are set on doing most or all of their own work, may find it helpful to have a table to set their ride upon to ease access when they work. Something as simple as a sheet of plywood set on saw horses can suffice. Riders of uprights will probably want to invest in a mechanic’s stand to save their knees.
Part 1: Derailleurs, Cables and Shifters
I still remember my first drop handle-bar ten-speed. It was a blue framed Huffy with gumwall blue tires, metallic paint, and as I came to learn, had the weight of an Abrams tank. While the Loti, Cannondales and Schwinns of my cycling club buddies rode flawlessly down the road, I was usually on the curb, putting the thrown chain back on the sprockets and wondering why the bike never shifted right. I was glad to have the Huffy, but if I knew then what I know now about shifters, cables and derailleurs I would have spent a lot more time riding happily!
A thrown chain can ruin a perfectly good ride, club race or championship winning charge. So what do you have to know to have a reliable shifting bike?
Proper Derailleur Adjustment
(Note: In handcycling the Rear derailleur is known as the Bottom. The Front derailleur is known as the Top derailleur. Sounds like a description of a game of cricket, no? However, for the discussions here I will refer to a derailleur as a chainwheel derailleur or cassette derailleur)
Make sure the basic derailleur settings are correct. Chainwheel derailleurs and cassettes derailleurs have two stop screws: One screw limits the top position and the other limits the bottom position of the derailleur.
Top Limit Adjustment. Common symptoms of a poorly set top limit screw are a chain that rides over the largest gear and onto the axle or crank. Turn the top screw in until you feel a slight resistance in the shifter when shifting into the largest gear. The resistance indicates that the screw is preventing the derailleur from pushing the chain too far. If you cannot shift fully into the largest gear or the chain will not stay on the large gear but drops down onto the next lowest gear, back the screw off slightly. When possible, shifting adjustments should be made on an indoor trainer when possible to simulate riding conditions.
Bottom Limit Adjustments: Cassette derailleurs that randomly skip the chain on and off the smallest gear or refuse to drop below the second to last gear may require the bottom end set screw backed off slightly. Adjust the screw until the skipping stops and the chain runs noiselessly on the smallest sprocket.
Note: A worn, kinked, mis-routed or badly adjusted shifter cable can also cause skipping on the bottom end, so if backing the screw out all the way does not stop the skipping, inspect the cable then adjust or replace it.
Chainwheel derailleur bottom end stop screw setting: The goal is to have the derailleur pull the chain down to the smallest gear without having it pull the chain off the small sprocket.
Handcyclists: Modern bicycle cabling, even the best and most expensive brands were never designed to survive the abuse that a constantly moving handcycle crank delivers so expect to replace any rotating cables after about 400 miles. Expensive lined compressionless cabling may give crisper shifting and slightly greater durability.
Also keep in mind that if after properly setting the top and bottom screws, replacing the cables and properly adjusting the cable tension, poor shifting symptoms persist, then you may have a bent derailleur bracket or a chainwheel derailleur that is worn out or loose.
Handcycle Racing Tip! Shifters that move with great difficulty indicate worn cables. I recommend that one or two week prior to the big race that you replace any cable that is showing wear and excessive friction. The remaining training days before the race will allow you literally work out the kinks and find/solve any cable routing issues that may affect your shifting on race day.
“Front Derailleurs operate in defiance of good engineering principles.” -Theodore Costantino. (Have you ever observed and contemplated the action and motion of a front/top derailleur? Watching the chain move back and forth often makes me a constant skeptic!) Even properly adjusted front/top derailleurs do not like to be shifted while under heavy loads and will often misbehave if you do not let off on the torque and allow them to do their job. When upshifitng, or even downshifting be sure to lay off the power slightly!
Shifters
Modern index shifting has revolutionized cycling in the same way that electronic shifting is about to change it again once more. Having said that, reliable index shifting depends on a properly adjusted cable and derailleur. On the spot adjustments while on the road can be made with the barrel adjuster on the end of the shifter but when the adjuster reaches it’s limits as the cable stretches it becomes mandatory to re-set the barrel adjuster and adjust the cable.
Handcycle Shifter Cable Maintenance Tip
When routing new cables and housings to handpedal mounted shifters that are tied to and bundled with brake cables be sure that when placing zip ties that the cable housings follow the same arcs. (think of the adjoining cable housings as the multi colored arcs of a rainbow and you will get the picture) Movable and rotating cable housings that are bundled and zip tied unevenly against neighbor housings will flex in strange ways and put excessive stress on the cables inside when rotated and cause premature cable breakage.
Shifter Preferences
I am not a fan of rotary/twist style mountain bike shifters (There I said it! I feel so much better now!) Twist shifters are simple, you twist to the right gear and the shift happens. Usually. Twist shifters tend to be less tolerant of sloppy and worn cables and so while you may think you have shifted into the right gear you know by the sensations on the cranks that the shift did not happen. The reason I prefer paddle shifters is that most paddle types have a small gap between shift points which allow the rider to go slightly past the intended shift point and so get a balky derailleur into the desired gear. However, a rider’s hand dexterity may determine the choice of shifter to be a twist. In cases where a twist shifter is required, shifting reliability may increase by the use of compressionless cables housings. (Sometimes known as “SIS”)
Very helpful and informative, Greg! I especially like how you stress that proper maintenance leading up to the big day can make the difference between an avoidable mechanical failure and the podium. Well done!
ReplyDeleteGood write up. Lets get some pics in the next article to help reinforce some of your thoughts!
ReplyDelete