In our Tech Q&A series, we tackle readers’ mechanical dilemmas and upgrade questions with help from the BikeRadar team and trusted industry experts. This time, a reader wants to modernise a much-loved steel bike – but wonders if adding disc brakes to an old rim-brake frame is possible, or a step too far.
I have an old, 26in steel bike that I love. It fits me and I want to keep riding it. But it has rim-brake mounts only. I want to give it a new lease of life and fit a disc-brake tab. Is this feasible, and is it worth doing?
Adrian Wilkin
First off, we’re very much in favour of projects such as this. If you’ve got a bike you love that fits you well, upgrading it and keeping it on the trails is a great thing to do.
It’s greener than buying something new and, perhaps more importantly, it can be a lot of fun, breathing fresh life into a bike you’re attached to.
Before diving into the specifics of adding a disc mount, it’s worth thinking about what you want the finished bike to be.
Build back better
If you’re planning a full rebuild, the fork will play a big role. Assuming your existing fork doesn’t have disc mounts either, you’ll likely be replacing it.
We’re making some assumptions about the age of your bike, but if you want to stick with suspension, the availability of new 26in forks with straight 1 1/8in steerers is fairly limited these days.
That said, the used market is packed with options from brands such as RockShox, Fox and Marzocchi. Just factor in the cost – or time – of a service if you want it performing at its best.
If you’re happy to go rigid, your options open up considerably. A number of brands still make rigid forks designed for older mountain bikes, often with disc mounts and modern axle standards.
Wheels are another consideration. New 26in wheelsets aren’t as common as they once were, but they’re far from rare. Again, the used market is full of good options, and you could always have a set custom built if you want something specific.
Beyond that, sourcing the rest of the parts for a rebuild shouldn’t be a major challenge. Drivetrain components, brakes and finishing kit are still widely available and generally compatible with older frames.
Disc inferno
As for fitting a disc tab to the frame itself, that’s entirely feasible on a steel frame.
Typically, a disc-mount plate is brazed onto the outside of the chainstay. Most builders will fit an IS mount, which means you’ll likely need a post-mount adaptor depending on the caliper and rotor size you plan to run.
If the frame uses particularly thin tubing, the builder may recommend reinforcing the area. In some cases, this involves adding a brace between the chainstay and seatstay to better handle the braking loads generated by a disc brake.
Unless you’re happy running your brake hose or cable with cable ties (don’t do that if you’ve gone to all this effort), you’ll also need to consider having new cable guides brazed on.
And because brazing involves heating the frame, a repaint is almost always required afterwards.
You can’t put a price on love
Costs can add up, but they’re not necessarily outrageous if the bike means something to you.
At the time of writing, Argos Cycles – a well-known UK frame repair and refinishing specialist – charges £150 in labour to fit a disc-mount plate. The plate itself is quoted at £30.
If reinforcement is required, adding a brace between the chainstay and seatstay is listed at £40. Cable guides or stops are around £16 per item.
You’ll also need to factor in the cost of refinishing the frame. A full respray for a steel frame and fork starts at around £275 in a plain or metallic enamel finish.
Some builders offer more packaged conversions. For example, London-based Stayer Cycles offers a mail-in service to convert a steel rim-brake frame to an IS disc mount for £200.
That includes adding the disc tabs and cable guides, with the option to remove the original brake posts, although refinishing isn’t included and the heat from the brazing process will usually mark the existing paint.
Of course, Argos and Stayer aren’t the only options. There are plenty of talented frame builders and repair specialists across the UK who carry out this kind of work, and sometimes the easiest way forward is simply to give one a call or drop in for a chat.
It’s also worth being honest about the economics. Buying a newer bike with disc brakes will almost always be easier and sometimes cheaper.
But bikes aren’t purely rational purchases. The emotional attachment to a frame that fits perfectly and has years of memories attached to it shouldn’t be underestimated – and building something unique around it can be hugely satisfying.
V for victory
If adding a rear disc mount feels like too much work or expense, there’s also a halfway option: run a disc brake up front with a V-brake on the rear.
Modern V-brakes are still impressively powerful. Shimano’s current models work extremely well, and boutique brands such as Paul Component produce beautifully made versions with excellent performance.
It might not be the most modern setup on paper, but it can still deliver plenty of stopping power – while enabling you to keep riding the bike you love.
