In an industry dominated by carbon fiber, we’ve come to see the magic cloth extend beyond just framesets, to include virtually every component that makes up the bike – even related apparel and gear.
However, the first we’ve seen carbon fiber incorporated into hardware, comes by way of renown composites gurus Stefan and Matthias of the brand that bears their name – Schmolke.
Carbon fiber bolts, for real?
Yes, believe it or not, according to the Schmolke brothers, their carbon bolts are not only as strong as those made from metal, but the carbon actually expands slightly when tightened, thus accomplishing the same internal tension as their metallurgic rivals with less tension.
As a result, carbon fiber hardware has made its way into other applications such as aerospace and automotive parts, offering a weight reduction as much as 40% over traditional screws, bolts, fasteners, ect…
‘Carbon fiber has hugely versatile potential beyond that which is currently exploited, we believe,’ says the Schmolke.
‘So we wanted to see how far we could push things. The first prototypes I tested on my personal bike, but after we had nailed down the consistent manufacture of the bolts, we saw they had promise far beyond the cycling industry.’
According to Schmolke, the bolts are made from intermediate-modulus carbon fiber sourced from Hexcel, which offer slightly more flex than high-modulus variants.
‘The way they’re made is actually pretty clever,’ says Schmolke. ‘The fibers are orientated at 0° and follow the spiral of the thread, which makes the bolt near impossible to strip. “However, orienting the fibers is difficult and the mold is incredibly complex, so that’s why they command a high price.”
Once the bolts are removed from the mold, they undergo a heat treatment process which combines a matrix material called PEEK, which acts similar to epoxy resin.
‘You can’t heat epoxy like you can PEEK, which is key to get the bolts of a consistently high quality,’ says Schmolke.
While the weight saving virtues of carbon fiber bolts may be appealing to those wishing to shed weight, unfortunately the amount of torque necessary to properly tighten components like handlebars, seat posts and stems pose too high of a risk. Therefore, the bolts have been relegated to lesser stress bearing components such as derailleurs, headsets, derailleurs and water bottle cages.
‘We’ve seen the potential for us to design our own components specifically for these bolts, which would open the door for some truly light weights.’
‘I never thought cyclists would like to buy such expensive bolts to save just a few grams. Obviously I underestimated the lengths cyclists will go to!’
more from Schmolke…
Carbon Bolts
Our screws are manufactured in a highly specialized pressure extrusion procedure. The material used is our own high quality Intermediate module fibres with PEEK-matrix. This is the only means to make sure the fibers are arranged in a spiraling pattern following the thread and centered towards the inside of the screw. The actual thread can not be stripped. In terms of dynamic strength carbon fiber is much superior to all other materials used for screws. They are stronger and 40% lighter than aluminium bolts.
Where to use carbon bolts:
Bottle cage
Our Carbon bolts are perfectly suitable for mounting bottle cages. Usually this requires M5x20 hex bolts. Some models, such as BTP or Tune, may require M5x20 bolts with a countersunk head. Our bolts may also be used for blanking off bottle cage threads, which are not currently required. In this case you may shorten M5x20 hex bolts to a thread length of 7mm.
Headset adjustment screw ahead-cap
Our Carbon bolts are perfectly suitable for adjusting the headset. Usually this requires a hex M6 bolt. These can often be shortened to save yet even more weight. Make sure the bolt is long enough to use the full length of thread of the insert in the fork tube. Some ahead caps may require an M6x16 bolt with a countersunk head.
Brake levers and shifters MTB
Our Carbon bolts are perfectly suitable for mounting brake levers and shifters on your MTB. Usually this requires M5x20 bolts. Please check what exactly you need before buying though. Bolts may have to be shortened to the length of the original bolts.
V-Brakes rear
Our Carbon bolts are perfectly suitable for mounting the rear brake of your MTB. Use your original bolts as a reference for shortening our M6x30 bolts. We recommend using a washer to ensure the brake’s function. Do not use our bolts for front brakes or disc brakes. Failure may lead to injuries. Use common sense when shaving weight of your bike!
Road brakes
Our Carbon bolts are perfectly suitable for mounting the brake pads to the brake bodies. Use your original bolts as a reference for shortening our M5x20. Make sure the bolt’s head is large enough to clamp securely. If in doubt use a washer. Adjustment bolt for bearing play THM Clavicula crank. Our M6x16 Carbon bolts with countersunk head are perfectly suitable for adjusting the side play of the bottom bracket bearings.
Front derailleur
Depending on the make and model you may be able to use up to 4 carbon bolts: With most derailleurs you may use our M4 bolts to close the cage.
For rear derailleurs
You may use our M5x20 bolts for the mounting of the derailleur to the frame. With Campy derailleurs you may replace the center bolts of the parallelogram with our M4x16 bolts. All Carbon bolts should be shortened to the original bolts’ length.
Rear derailleur
You may use a fair number of our bolts on all derailleurs:
Due to wide variety of bolts used we recommend to check what sizes are needed prior to buying. Shorten all bolts, with the exception of the stop bolts, to the original bolts’ dimensions!
Do not use our bolts for:
– Clamping a handlebar in the stem. The required torque is too high. – Seatpost clamps – For brake discs
You may use our bolts to clamp the shifter cables. Please be aware, that the bolts heads are likely to wear with use, and that they may have to be replaced then.
Schmolke
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