Jim’s Tech Talk
By Jim Langley
Thanks to information provided by helpful readers “JPeterO,” “Chris” and Stephen Turk, I believe I have a little more to add to my answer to the question about older Cannondale carbon forks asked last week. If you missed that story, here it is: Star Nuts and Full Carbon Forks? NO!
The most helpful thing to me was this Cannondale illustration. If I interpret it correctly it could explain why Cannondale’s so-called “star nut” doesn’t damage their carbon steerer forks.
Doesn’t Appear to Work Like a Standard Star Nut
Focus your attention on the first steerer in this illustration, the one on the far left. Look at what they have labeled a Single-Flange Star Nut. Compare it to the standard star nuts in the other steerers in the illustration.
The first star nut is so different from the others, my take on it is that it works differently. Notice that the “star’s” teeth are much shorter and wider than those on the other star nuts. Also notice the Insert that the star nut apparently rests against.
Looking at these details, maybe the reason this can work in a full carbon fork is because the star nut teeth never come in contact with the steerer?
Unfortunately, I still cannot explain based on their written instructions or this illustration, 1) how this Single Flange Star Nut stays in place to allow headset bearing adjustments (is the insert made of rubber so it can mushroom?); and 2) why the other two carbon forks in the illustration call for standard star nut use – since standard star nuts are known to break carbon steerers.
Maybe someone at Cannondale who remembers these old designs will see this and completely solve the puzzle for us.
A Tool Tip for More Than Bicycle Repairs
Offhand I can only think of a couple uses for hose clamps when fixing bicycles. One is as a saw guide to ensure straight cuts when cutting down tubing. And two is to fix a loose, leaking hose or chuck on a floor pump.
But the thing is that we bike mechanics get called on to service all kinds of other things around the house and garage where we are likely to run into hose clamps a lot. So, when I saw Richard Trethewy on the Ask This Old House TV show wielding a standard 7-way screwdriver to tighten one, it made my day.
Because instead of tightening it with the flat blade on the screwdriver, Rich had pulled the screwdriver tip out of the end of the tool and was using the now-open socket on the screwdriver to tighten the clamp!
Maybe I’m the only mechanic who doesn’t know this great tip, but I wanted to pass it along in case you didn’t either. It sure makes easy work of hose clamps. Here’s a photo.
Oh, in case you don’t have one, you can pick up 7-way screwdrivers anywhere tools are sold. Sometimes they’re called different things like 4-way or 7-way. It has to do with how many tools are included. Bring a hose clamp along so you can try the one you’re thinking of buying and make sure it fits.
10,207 Daily Rides in a Row
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.
Here is a Cannondale document on star nuts and carbon forks. A relevant section is below. I think Cannondale’s use of star nuts in carbon back then reflects a misunderstanding of the dangers.
http://wodocs.com/docum/541-cannondale_bicycle_corp-06_en_cannondale_carbon_road_fork_instructions_technote-2.html
Driving a star nut with the tool may produce marks on the inner carbon
steerer tube walls. This effect is normal. Occasionally, the marks inside
the steerer tube can interfere with insertion of the top cap. Any burr or
mark can be reduced by using a ball hone on a drill. This will remove the
marks and open up the diameter enough to allow the top cap to easily
slide inside the steerer. The ball hone will not cut structural carbon
fibers, and will only remove the raised epoxy resin.
Thanks, Chuck, I’ve read that page and I agree that it suggests at the time (early 2000s that they had yet to understand that you should never use a star nut inside a carbon fork.
Regarding your second paragraph, I’m repeating myself, but no one should ever drive a star nut into a carbon fork steerer. Doing so will score/scratch/cut the carbon. Then, when the star nut is in place stuck inside the carbon steerer its sprung steel teeth will push out applying a cutting force on the inside of the steerer. These things will cause carbon steerers to break, which can lead to one of the worst crashes you can have.
Fortunately, modern carbon forks should all come with a special piece that takes the place of a star nut and is completely safe for the fork.
Thanks,
Jim
Ha – that’s why those screwdrivers are SEVEN way; because of the nut drivers. You’ll see that the nut driver size is different on each end of the insert.
Yes, that’s true, Chris. Thanks!
Jim,
Most hose clamps have a 5/16 head. I use a 5/16 nut driver to tighten hose clamps. It is far more secure than a screw driver, doesn’t slip off or strip out the nut, and can’t cut the hose if it slips.
Thanks, Harold – that’s exactly why I wrote up this tip. Using a flat screwdriver on a hose clamp is a pain because like you said it slips off the nut and worse. Which is exactly why it’s so cool that simply by pulling out the flat screwdriver end of the 6-way screwdriver you actually have a built-in 5/16ths nut driver.
Now, I realize you can use an actual nut driver tool to tighten hose clamps but most bike mechanics if they have nut drivers at all, aren’t likely to have a 5/16ths (most bike fittings are metric and Allen type). And as long as you have one of the these 6-way screwdrivers you’re set – no need to buy actual nut drivers.
You can use pliers, adjustable wrenches, locking pliers to tighten hose clamps, but all those are a pain to use, too.
Thanks for the feedback!
Jim