So You Over Tightened your Stem and Cracked you Carbon Fork-Here's How to Fix it!
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- Опубліковано 1 жов 2024
- I bought a really nice gravel bike frame on eBay with a cracked carbon fiber steerer. Somebody over tightened the stem and cracked it. Don't worry, it's not trash. I can fix it! In this video, I show you have I repaired it and made it safe to ride. I saved myself $500 and I kept it out of the trash bin. This is part of a much larger project and a good first start. I hope you enjoy the video!
If you don’t have the tools to make an insert, you can skip the hard part and buy an insert made by Envelope or Cervelo.
That crack is due to morons using a short expansion plug, all road bikes are using the wrong length expansion plug, it should be 10 cm long so that it supports the headset area and of course the extension should be torqued properly. You don't know if the delaminations have reached further down past that crack, so have that fork checked with ultrasound service and then do the fix if the crack is short.
I've bought new forks (from Whisky) which have shipped with those tiny 30mm compression plugs. I don't understand why they do it. The one I made is 100mm and thoroughly bonded to the inside of the fork so it provides good reinforcement. I've put 1600 miles on it and three gravel races without issue. I pulled it apart a few days ago in prep for another race on Saturday and it looks good as the day I put it in there. I'm not worried.
is carbon fiber really that better? i had a steel bike for 30 years and no crack! amazing video and nice idea! Greetings From Portugal
My thoughts exactly.
Depends on the application and the maintenance that the part receives. This likely would not have cracked if not over tightened. I have had steel and alloy parts that deformed from over tightening, so I'm not hater of carbon. It wouldn't be my first choice for a steer tube, but neither would I turn my nose up at a carbon steer tube.
Hi, I just wanted to ask your advice. I just bought a carbon frame secondhand, and as I was descending the other day, I heard this crack. I hope I haven't damaged either the steerer or the seatpost. I need to check them now, but if I have what would you recommend to fix the steerer? A compression plug by say Specialized (which one would you recommend?) or the ENVE or Cervelo insert? And do you have tye links for these inserts with epoxy glue? I'll check both tonight. Can you fix a seatpost also, the same way? Thanks for the video. I will be doing a lot of downhill so I need to rely on these two things to prevent failure and hence an accident.
Are you sure it wasn't your water bottle or seat bag banging against the frame that made the noise? I have an Emonda which I swore I cracked in half when I hit a frost-heave, but I tore it apart, gave it a full inspection, and didn't find any damage. Decided it was my water bottle slipping up out of the cage and hitting the underside of the top tube. If I were you, I wouldn't repair a seatpost unless it is one of those integrated posts. Seatposts are cheap (relatively speaking, I think I pay about $120 every time I buy a new one). For the fork, regardless of whether you find a crack or not, it might be worth the peace-of-mind to install one of the Cervelo inserts. I trust the bond-in type more than compression plugs. It bonds in with regular epoxy (Gorilla glue and JB Weld are common manufacuters; it's a two-part that you mix together).
@@RobertAdairWorkshop I am sure because I have neither on the bike at the minute (no bottle cages or seatbag). I inspected the top of the steerer today because I changed the stem and it looks fine. Went for a ride and no creaks or cracking sounds. It might be the seatpist because I haven't torqued it to the correct setting I don't have a torque wrench that size). The seatpost is one of those that has a wedge in the back (I really don't like that design at all). Might have to go to LBS for them to check it and torque it to the correct setting. Yeah, I might do as you say with the steerer for peace of mind. Thanks again.
My compression plug is too low inside the fork and I actually always used a torque wrench, but since there's plenty of void between top cap and the compression plug, even torque wrench will slowly crush the top part. It only makes sense to have a long compression plug in the first place. Instead of your solution, I will probably replace the original compression plug with a longer one and keep my fingers crossed at -10% downhill at 80km/h.
I’m putting together a new Niner RLT and am going to make another of these bond-in plugs for that fork. I’ll have some extra aluminum from that. If you ping me with some measurements from your fork’s steerer, I can turn that scrap into one for your fork if you want to try that over another compression plug.
The compression plugs that you buy sit on top of the steerer tube though. How is you r plug sitting too low.
Is there an issue with the aluminum reacting with the fork tube and causing corrusion?
There is a possibility of that, yeah. I’m relying on the epoxy to offer some isolation between the two materials and use a special one-piece top cap that will help keep moisture out of the area. But yeah, galvanic corrosion is a possibility.
Brilliant fix and i agree should be bomb proof just building my first gravel bike and watching as many carbon fork vids so i dont go wrong
My lbs guy is very skilled somehow he had installed a flower nut and my fork was working fine. Little did i know compression plug is for carbon steerer tube. My fork is exactly broken the same as yours upon installing flower nut. I bought 80 mm compression plug and a riser stem. The riser stem grips on the broken section and the actual stem all force is absorbed by riser stem steererer. Is this a good enough fix? Some UA-cam channel recommended to put a cricket bat tape on it.
Hi, Cole. The one I made is bonded in place and the crack is supported on all sides by the adhesive bond with the aluminum. This reduces the stress on the crack preventing propagation even when subjected to repeated vibrations. I would be hesitant to run the cracked fork using only a compression plug. The plug provides and outward force on the crack that is resisted by the stem, but the compression cap won't support the crack fully. It is possible for the crack to propagate due to stress risers from vibration. If you could find a way to bond in your compression cap so that the crack is fully adhered, I think that'd be a better solution. The key is to support the cracked are fully so that it isn't carrying any repetitive loading.
@@RobertAdairWorkshop yes I was wondering the same thing that as compression plug provides an outward force wouldn't be best. I'll see if a craftsmen here could make such a thing. In the meantime I am thinking to wrap the steerer tube broken part with plenty of loops of nylon thread and a cricket bat tape to secure it in place
Nice video, would you guys have a link on where to buy one of these inserts?
This is the one I mentioned in the video:
www.excelsports.com/cervelo-fork-insert-kit-359
It’s out of stock from Excel Sports but I bet you can find it somewhere online.
I appreciate your creative solutions! Nice fix.
Thanks!
Great job. 👍
Thanks 👍
Hi, the problem with Aluminium is, that aluminium expands very well with heat (actually the best of metals). On a hot summer day, it can break your fork. Especially if it is a tight-fit solid piece of aluminium with no other spaces to expand.
Nah, man. The thermal coefficient for Aluminum is 24x10^-6 m/m-C. A 20 degree C temperature change would only change the diameter less than 0.010mm. That isn’t going to break anyone’s fork.
it will BARELY expand even in 120 degree Fahrenheit day. Its too small of a diameter to make a difference.
@@RobertAdairWorkshop, I think you are right then.