Lots of people are into adapting vintage 1990s MTBs into modern gravel bikes, yet Geoff went one step further with his 1993 Rockhopper: he took on a disc brake conversion. In his garage! Let’s check out his process and final product below…
I built a bike this summer that I’m really stoked on and figured I’d share the details for a Readers’ Rides submission. It’s a 1993 (I believe) Rockhopper that I converted to disc brake in my garage.
The backstory is the following. I’ve always been super keen on old rockhoppers for the way they ride and look and because they can still be picked up for a couple hundred dollars. I’ve been wanting to try a disc brake conversion on one for years and when a pristine and mostly original example popped up locally, I bought it without a plan, just a vision of a drop bar disc brake gravel grinder. This bike was on the small side for me in stock trim, which is the tradeoff to be able to get a manageable reach with drop bars on these frames.
Originally I was thinking post-mount calipers would be the way, but a take-off Rival 1x hydraulic groupset popped up for the right price that I jumped on. I used some QR road disc wheels to get 160mm rotors in place and the idea for the caliper mounts came to me after some tinkering. A weld-on adapter made from steel plate, thick enough to be tapped, would accept bolts through a mating aluminum plate that sat flush on the weld adapter. These are the bolts that are visible in the photos; they sit outboard of the frame tubes. To mount the calipers themselves, the aluminum plates are drilled and countersunk such that the bolts thread in from underneath – just like an OE flat mount caliper adapter.
Before having parts cut out, I used plastic printed prototypes to dial in the correct plate thicknesses for both the steel weld adapter and the aluminum caliper adapter. This part was important to make sure that the contact patch and rotational alignment of the pads landed on the rotors in the correct location, given that I had no intentions of using anything other than uniform thickness flat plates. Mocking things up gave me the confidence I was looking for to get the parts cut out and go for it.
In a controversial decision, I used my MIG to weld these on. I had no idea what the thickness of the frame tubes were and the internet strongly recommended not to do this. I grabbed some scrap 4130 tube from a local framebuilder and tested things with the MIG before deciding that it could be done – if not aesthetically, at least structurally.
I sanded the weld area down and tacked things into place after mocking everything up. The welding went pretty alright, considering I was joining 1/4″ plate to very thin wall steel.
From here, I ground things as best I could and painted over the area. I assembled the rest of the bike and used tiny P-clips and some existing frame features to manage cable routing. The bike really shines on gravel, is slow and comfy on the road, and is a sketchy kind of exhilarating on singletrack.
The brakes feel excellent. It’s my favorite bike that I own, all while being a fraction of the cost of my others.
Build Spec:
Frame and Fork: 1993ish Specialized Rockhopper Sport
Disc Adapters: Custom
Brakes: SRAM Rival Hydraulic
Wheelset: Hunt/Mason 650b Adventure Disc QR
Tires: Continental Terra Speed 650b x 40mm
Cranks: Truvativ Stylo 172.5
BB: SRAM DUB BSA 73mm
Chainring: Praxis 40T 6mm offset
Cassette: SRAM Rival 11-42T
Derailleur: SRAM Rival 11spd
Bars: Specialized Crux Takeoff
Stem: Cannondale Scalpel Takeoff w/ Threadless Adapter
Seatpost: Kona 27.2 Parts Bin
Check out Geoff’s blog for more!
We’d like to thank all of you who submitted Readers Rides builds to be shared here at The Radavist. The response has been incredible and we have so many to share over the next few months. Feel free to submit your bike, listing details, components, and other information. You can also include a portrait of yourself with your bike and your Instagram account! Please, shoot landscape-orientation photos, not portrait. Thanks!
