This post is about how to modify your bike to cycle with thumb arthritis (CMC arthritis) . This kind of arthritis causes pain while cycling, especially while using your thumbs to change gears. Many cyclists (including me) eventually develop a common type of thumb arthritis, called CMC (carpometacarpal) arthritis. Since getting my diagnosis, I have modified my bike to make it easier to cycle with thumb arthritis without pain. Most of my pain occurred when I changed gears on my mountain bike using my trigger gear shifters. This post describes the cheap changes I made to modify my bike. I include several ideas for you to modify your bike to cycle with thumb arthritis more comfortably.
What is Carpometacarpal Thumb Arthritis?
Carpometacarpal (CMC) arthritis causes a deterioration of the joint at the base of the thumb, leading to pain when grasping things, and when using rapid trigger shifters on a bike. It can be caused by “activities and jobs that put high stress on the thumb joint” (Mayo Clinic).
After decades of doing a lot of cycling, I developed CMC thumb arthritis. It took a while (and an X-ray) to rule out other causes, notably De Quervain’s tenosynovitis. In the meantime, it was becoming quite agonizing to change gears on my bike.
Once I developed thumb arthritis, I rapidly became aware of how often I changed gears on my bike. Basically, I am almost constantly using my right thumb to change the gears on the front hub. As my bike has trigger shifters (also known as rapid fire shifters), gearing down on the front hub is done entirely with my right thumb. Over time, this was becoming so unbearably painful that I was trying to avoid changing gears, and even starting to avoid cycling.
Possible Bike Modifications to Cycle with Thumb Arthritis
The first consideration was of course to do something to change the gear shifters. Using trigger shifters for so long was probably the cause of my problem. I had to stop using my thumbs so much, both for pain relief and also so as not to make the arthritis worse. But solutions were hard to find.
One way would be to fit electronic gears. However, this would be incredibly expensive (about two thousand dollars). Plus, electronic shifter group sets cannot be retrofitted on many frames. All in all, it would make more sense just to buy a new bike that already had electronic gears. But those start at about four thousand dollars.
Well, that brilliant idea was a complete non-starter with Mrs. Average Joe Cyclist, so … back to the drawing board.
Twist-grip Shifters to Cycle with Thumb Arthritis?
I briefly considered swapping out the trigger shifters with twist-grip shifters. But I have never been a big fan of twist-grip shifters, as I don’t find them precise enough. Much more importantly, twist-grip shifters would still put some pressure on my thumbs. And the retrofit can be complicated. Not all twist-grip shifter sets are compatible with all bikes.
However, if you have early stage arthritis, this change might be enough for you. It would enable you to use your entire hand to change gears, not just your thumb. Apparently, it has brought relief to many mountain bikers (Mountain Bike Forum).
Road Bike Brakes to Cycle with Thumb Arthritis?
The combined brakes/shifters found on road bikes would have been a huge improvement, as you use your fingertips to change gears with those. So, you are not putting pressure on your thumbs. However, it would not suit my current riding conditions to switch from a mountain bike to a road bike. Plus, “I know, I could just get a new bike!” is almost always a non-starter with Mrs. Average Joe Cyclist.
However, this could be a change that would work for you, if switching to a road bike is an option for you. But do bear in mind that on road bikes you tend to lean quite heavily on your hands, which would not be helpful. However, see below for an idea on how to decrease the weight on your hands.
The Source of the Problem: Trigger Gear Shifters
The trigger shifters on my bike require the use of the thumb when down-shifting on the right side (for the front hub), or up-shifting on the left side (for the rear hub). In practice, like most people, I change gears on the front hub much more often than on the rear hub.
So I could remove about 95% of the pain by somehow modifying the down shifter on the right. This is a short lever, and due to its position, you pretty much have to use your thumb to work it.
I brainstormed the problem with my friend Wayne, an engineer. Wayne has been known to fix light aircraft in the desert using scrap metal, so I suspected he would come up with a solution. And sure enough, he did.
“How about if we just make that lever much bigger, so you can use your entire hand to down-shift?”
Yes, that would do it!
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Modifying my Trigger Gear Shifter to Cycle with Thumb Arthritis
Wayne’s idea was to add an extension piece to the lever in question, so that I could operate it with my entire hand. We started by cutting out a small piece of aluminum, destined to be our gerry-rigged lever extender.
Once the shape and size were right, Wayne used his dremel to smooth the edges.
We first tried using an epoxy glue to glue the piece of aluminum to the existing lever.
However, this did not hold up to usage. The contact surface was just too small for any kind of glue to withstand constant gear changing. I do think that using an epoxy is a good starting point, though.
To reinforce the epoxy, we had to drill a small hole in the existing lever, and in the extended lever, and then screw them together with a small screw.
This did the trick. We ended up with a much bigger gear shift lever, essentially. And I can now down shift by simply swiping the large lever with the palm of my hand. My thumb is not required at all.
This simple change made a huge difference. I can now cycle for hours again, without ending up with my right thumb in agony. I can now change gears just as frequently as before, instead of trying to avoid changing gears.
At some point in the future I might make this modification on the left-hand trigger shifter as well. But for the time being, this is all I need to do with the shifters. I just stay in the middle of the rear gear hub.
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Modifying the Stem of my Bike to Cycle with Thumb Arthritis
The second change we made was easier. I knew that raising the handlebars would take some of the weight off my hands, and therefore off my thumbs. This is easy to do by simply buying and fitting a stem extender. Luckily, most mountain bikes have standard-sized stems and handlebars, so I simply ordered a stem extender off Amazon. I had a choice of lengths, and went with the 110 mm choice to give me as a reasonable amount of flexibility while still maintaining a mountain bike feel.
With this stem extender, you have multiple points of adjustment, so you can fine-tune the height and angle of your handlebars, until you find the best possible fit to take the weight off your hands.
I was very impressed with the quality of the stem extender, especially relative to the price. And installing it was quite simple, not even requiring the use of the enclosed instructions. Below is the exact stem extender that I bought.
Video Showing How to Install a Stem Extender on Your Bike, to Help You to Cycle with Thumb Arthritis
In case you need a little help, here is a video about how to install a stem extender.
Bottom Line on How to Modify Your Bike to Cycle with Thumb Arthritis
These simple modifications will go a very long way towards making it comfortable to cycle with Thumb Arthritis. They have done the trick for me. Here is my modified bike, now much more comfortable for cycling with thumb arthritis.
Good luck with your efforts to keep on cycling, despite the annoying side-effects of aging!
Sources Used in this Post
Bostok, Susie. Medical – Thumb Osteoarthritis. Adventure Bike Rider.
Mayo Clinic. Thumb Arthritis – Symptoms and Causes.
Mountain Bike Forum. Thumb joint arthritis solutions for riding?
Young, Karol. Cycling with Thumb CMC Joint Arthritis: Keep Moving Forward! Clinical Pearl No. 62 – May 2020.
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