Converting Your Bike to a Hybrid Disc/Rim Brake Setup, Part 2

As you’ll recall, last week I let reader Bruce Ross grab hold of the Tech Talk handlebars to start the story of upgrading his beloved Colnago C59 to disc braking. This week, in the conclusion, he covers every detail involved, including getting the replacement fork refinished to match, and the complete costs. After reading the tale, if you have any questions or comments, Bruce is happy to answer. I’ll let Bruce take it from here. —Jim Langley

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By Bruce L. Ross

Numerous decisions go into a project like this. The first and foremost decision, from my point of view, is which bike is a likely candidate for this conversion. Once this choice is made, other decisions tend to become much easier, depending upon your overall interest and how much you wish to keep the bike looking as original as possible.

Choice of Fork

There are many great aftermarket fork choices if your frame manufacturer/maker doesn’t offer a disc-compatible replacement fork. There are no longer any Colnago C59 Italia forks available, so my shop secured a brand new Colnago C60 Italia disc fork. While the new C60 fork fit the head tube of my C59 perfectly, the graphics and paint on the fork did not match my C59 frame at all.

I therefore decided to take the disc fork to Carbon Solutions, a custom paint and carbon repair shop in Watsonville, California, to see how close the owner, Joe Vasquez, could match the decals and finish on my C59 frame (see photo).

Joe has done several projects for me over the years and is a master at painting and carbon repair. He gets bikes shipped to his shop from all over the world, often in horrible shape, and is extremely skilled at putting them back together and making them look as original as possible. I was very impressed with the results he was able to get on my fork.

The other factor to consider when choosing a fork is whether you want a post-mount or a flat-mount disc brake. My Colnago disc fork was only offered in a post-mount version, which is the type used on all off-road forks. However, currently the component manufacturer Shimano, which “owns” perhaps 80% of the road bike component market, is moving to flat-mount and away from post-mount.

The advantages of flat-mount brakes are that they are smaller and lighter than the post-mount versions. All other factors being equal, if a flat-mount fork is available, I believe it would be the preferred choice.

Choice of Brake

There are two types of disc brakes to choose from currently – hydraulic-actuated, or cable-actuated. I’ve always ridden Campagnolo components and love their look and feel. Although Campy has just released their hydraulic disc brakes into the consumer market, their system doesn’t offer either a post-mount front disc brake or cable-actuated front or rear disc versions.

I therefore chose to use TRP’s Spyre SLC cable-actuated front brake. Although TRP has a hydraulic model of this brake available, my shop advised me to use the cable-actuated version as it would feel very similar to my rear TRP cable-actuated rim brake.

Both Shimano and SRAM have excellent hydraulic and cable-actuating disc brake systems, so if you use either one of these manufacturers’ components, you have more options available to you.

However, TRP is one of the only companies that currently offers a dual-sided pad-actuation cable brake, which is considered to be a distinct improvement over either the Shimano or SRAM single-sided pad-actuation systems.

Choice of Rotor

There are many aftermarket rotors to choose from, and most are very good. Road rotors are either 140mm or 160mm diameter, whereas mountain bike rotors are 160mm (rear) or 180mm or 200mm (front) – all made from a single piece of stainless steel. My choice for this project was the Shimano RT99S 160mm Center Lock rotor.

Currently, rotors are interchangeable road-to-MTB, but Shimano is soon to release a “road only” rotor, the SM-RT9000-S, which utilizes their proprietary IceTech technology, a unique process that sandwiches a thin piece of aluminum between two outer pieces of very thin stainless steel.

The engineered effect reduces the heat build-up at the rotor surface by as much as 30 degrees while at the same time promoting better braking power and longer wear. Industry rumors suggest that Shimano is also rounding the edges of their new rotors in hopes of reducing the possibility for injury.

Choice of Pads

This is perhaps a minor consideration, but the people at my local shop tell me that the Shimano M05 disc pads allow for superior wear over the TRP Slate X2 pads that came with the brake. Apparently, this is even more the case if used in a cyclocross or wet and muddy application.

Choice of Wheel(s)

Due to the extra width required for the front disc rotor, which also includes the rotor mounting hardware, you will need to consider, at the very least, a brand new disc hub that would allow for a hand-built wheel using either a carbon or aluminum rim.

Hand-built front wheels can be tricky as you need to match the amount and type of spokes being used to both rim and hub as well as the specific recommended spoke lacing pattern for front disc wheels.

Companies such as Enve and DT Swiss are excellent, quality manufacturers of wheel goods and could help determine how best to get results from a hand-built front wheel.

Alternatively, you might consider whether or not you wish to replace both wheels for this project, as I did, or just your front wheel with a factory-built disc wheel. Wheels are a huge investment, depending upon your approach, so your choice might be guided more by your pocketbook than your preference.

I chose to replace both Mavic Cosmic Carbone 40C wheels originally on my Colnago with newer Mavic Cosmic Pro Carbon SL C wheels. The new wheels are offered in both disc and rim brake versions, and sold separately, which made these an easy choice to replace my previous wheels. Also, the carbon weave on the frame, fork and wheels match, which was a plus for me as the overall aesthetics of the bike was kept intact.

Costs

I’ve itemized all of the related costs for this project, below. Many of the prices could be reduced by choosing less expensive components or perhaps using a hand-built front wheel instead of a factory-built one. It is also important to note that I was able to trade the shop my old pair of wheels toward the cost of this conversion.

• Mavic Cosmic Pro Carbon SL C Front Disc — $1,035.00
• Mavic Cosmic Pro Carbon SL C Rear — $1,165.00
• Colnago C60 Italia post-mount disc fork — $900.00
• TRP Spyre SC Carbon disc front brake — $85.00
• Shimano XTR RT99S 160MM C/L IceTech rotor — $150.00
• Labor to re-paint and apply decals to fork — $225.00
• Labor to install front fork, brake and rotor — $200.00 (includes miscellaneous parts)

Total: $3,760.00

(Less trade for my older Mavic wheels (pair) — $900.00)

Adjusted total: $2,860.00

Conclusion

I am very happy with how my project turned out. The bike brakes extremely well, and the conversion didn’t add much overall weight to the frame. Apart from getting used to the new look of the bike, I would certainly be willing to consider converting another one of my road bikes into this hybrid disc/rim braking system.

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Bruce L. Ross is a psychotherapist, international specialty woods broker and long-time cyclist (44+ years and counting) who lives, works and rides in Santa Cruz, California. Bruce owns several bicycles and splits his riding time between road and mountain. For questions or comments, he can be reached at [email protected].