Jim’s Tech Talk
By Jim Langley
Thanks for the excellent comments about last week’s column on speed wobble. As usual, I shared it on my Facebook page, and a lot of knowledgeable cyclists weighed in there, too, with additional issues that cause this phenomenon.
So this week, I’ve updated my list of causes since there are quite a few more. And because it’s such a frightening issue – bad enough that some of you said you actually just bought a new bike to solve the problem!
Two industry gurus, Bill Farrell, the founder of New England Cycling Academy and the inventor of The Fit Kit and their frame alignment system (Bill sold the business); and Craig Calfee of Calfee Designs a pioneer in carbon bicycle technology said that frame and fork alignment issues cause speed wobble. I’ve added them to the list.
In case you aren’t a Facebooker, here’s part of Bill’s comment, “Whenever a cyclist described having “speed wobble,” I’d pull the components, clean the threads and face the bottom bracket. Upon inspection, the culprit was always a misalignment in the tracking plane. Once the frame was “cold set” (i.e. bent) back into alignment, the “speed wobble” issue was resolved. When the newer carbon fiber materials integrated into production, cold setting this type of material was impossible.” [Bill talks about how he helped find and fix carbon frame alignment issues, too – with machining not cold forging.]
And, here’s some of Craig’s comment, “Fork alignment is a very different animal than frame alignment. When the steering axis is projected to one side of the tire contact patch on the pavement, it forces the rider to make a correction. This sets up the speed wobble and the rider continues with an asymmetrical response, making it worse.”
To read Bill and Craig’s comments in full plus a lot more, visit my page here: https://www.facebook.com/langley.jim.
Here’s a graphic from Sheldon Brown showing some steel frame and fork alignment tools:
Last week I mentioned my riding buddy Tom’s speed wobble. Thanks to the comment from Melissa about her Roval wheels having bad bearings that caused a wobble, Tom is now looking into that possibility on his Rovals. Thank you Melissa!!
The New List of Speed Wobble Causes
- Stem too high lightening the front end too much
- Excess weight on wide dropped handlebars (such as added accessories)
- Tire not seated (front or rear)
- Defective or damaged tire with crooked tire treads (front or rear)
- Out of true or round wheel (front or rear)
- Seat positioned too high for the rider (incorrect seat height)
- Superlight frame tubing under a rider too heavy for it
- Frame alignment issue
- Fork alignment issue
- The wrong fork geometry for the bicycle
- Defective frame design
- Cracked frame or fork
- Wheel bearing problem
- Wheels not properly positioned in the frame
- Wheels not fully tightened in the frame
- Loose headset
- “Death grip” on the handlebars
- 25-pound e-bike battery mounted on a rear rack (the tail wagging the dog)
- A gust of wind from the side
- Shivering can make a bike wobble
- Cattle guards
- Loose bags or weight loaded too high in bags
More Actions While Riding to Stop a Speed Wobble
Along with the causes, here are some additional techniques recommended
- Move a pedal to 6 o’clock and put a lot of weight on it to stabilize the bike
- Don’t let the wobble start in the first place by routinely resting a knee against the top tube on descents
- Keeping your speed below a certain mph that you know won’t cause a wobble on your bike
- Crouching down to lower your center of gravity
- Installing a roller bearing headset
In closing, probably the most important thing is to have a strategy for dealing with speed wobble if it happens to you. Based on my own experience and the fact that it’s the most commonly offered tip, if you can only remember one technique, you should remember to bring your knees together to squeeze the top tube of the frame to stabilize the bike and hopefully stop the wobble. And once you know your bike may wobble, keep in mind that if you get in the habit of resting one knee against the top tube as you start picking up speed downhill, that that action could prevent the speed wobble from happening in the first place.
Thanks again readers and Facebook friends for all the help!
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.