By Rick Schultz
I recently had a customer come in for a bike fit who didn’t realize he had a damaged/cracked carbon fork. The fork came off a 2014’ish Giant TCR Advanced Pro. I usually perform a quick safety inspection of my customers bicycles to see if there is anything that stands out as an issue. The issue was that whoever built or fixed his TCR in the past cut the steerer tube a little too long causing the stem cap to bottom out on the stem just shy of being able to correctly preload the headset bearings. This caused the fork to rock back and forth. So, instead of correctly diagnosing the actual problem, someone took the easier way out and just cranked down on the stem cap screw and stem pinch bolts ever tighter. Their action caused the fork to crack in 2 places.
Bike fit on-hold. He went to his local Giant dealer and ordered a matching fork. A month later, he scheduled the rest of the fit and we installed the fork CORRECTLY then proceeded with the bike fit.
In the meantime, he donated the fork ‘to the cause.’ I cut it up to show and discuss what a high quality fork actually looks like inside. Inspecting this fork, you will note one thing that is different than the usual forks I see. Inside the Giant TCR fork is piece of machined aluminum that is molded inside the carbon fiber crown and steerer tube. Most forks are only carbon. Why? (a) it’s a little lighter, (b) it’s cheaper to produce but (c) not quite as strong/safe.
For road bikes, there are 3 main types of forks. (a) steel forks with steel steerers making these the heaviest, (b) carbon forks with steel/aluminum steerers making these lighter and (c) carbon forks with carbon steerers which are the lightest. This TCR fork is a carbon fork with a carbon steerer, but, with an embedded piece of aluminum for added strength and safety.
The following table shows the inside of 2 different steerers (both sawed off at the crown). The remaining photos show the inside of the crown with the inserted rectangular aluminum support which measures approximately 65mm long x 15mm wide x 1.5mm thick. Also, in the photos below, note minimum wall thicknesses of each steerer tube.
This Giant TCR fork is built with the riders’ safety in mind! Kudos Giant! So, the final question “Which fork would you want to ride?
Another damaged fork cracked from overtightening of the stem. Notice no supporting metal at the crown interface. In order to get this fork ready for a photo, I had to pull out a lot of left over bladder. This fork is from an Orbea road bike.
Note: minimum wall thickness at 12 o’clock and 6 o’clock is 3mm.
The Giant TCR Advanced fork. Notice the silver piece of aluminum embedded into the center of the carbon. This 65mm x 15mm x 1.5mm piece of aluminum extends about 30mm from this point up into the steerer tube and 35mm into the fork crown.
Note: minimum wall thickness at 3 o’clock and 9 o’clock is 6mm. Twice the thickness of the Orbea fork steerer. Slightly heavier, Yes, a lot safer, Yes.
Fork sawed in half. I first cut off the steerer tube, had some trouble sawing though due to the aluminum insert.
Next, I sawed the crown down the middle.
Fork sawed down the middle. Hacksaw tracked next to the aluminum which is reason shows on one side only.
35mm of aluminum embedded into the fork crown.
Another picture showing the insert.
When sawing the fork in half, I placed the blades into a vice which then allowed me to make another video performing a tap test so you can actually hear what damaged carbon sounds like. Many of an article out there describes a ‘DEAD’ sound, but nothing replaces hearing what it actually sounds like.
Coach Rick Schultz is an avid cyclist who trains, races and coaches in Southern California. Rick is an engineer by trade, and in addition to being a coach, he’s a bike fitter and prolific product reviewer. He’s the author of Stretching & Core Strengthening for the Cyclist in the RBR eBookstore. Check his product reviews website, www.biketestreviews.com, and his coaching site, www.bikefitnesscoaching.com. Click to read Rick’s full bio.
Rick,Your demonstrations are informative.You take the time to explain the true cause & effect of conduct relating to bike safety.The over tightening illustration & tap test were insightful.I especially liked the fact you took the time to cut the fork open & show the issues to prevent catastrophic failures & quality manufacturing.it was smart of your customer to have his bike safety checked by you too.Thanks again.