tricky 

I recently saw that one of our local bike wizards (Cyclefab) is willing to add disc tabs to vintage frames. This got me thinking. I have been saving up for an All-City frame, but am now thinking that I can kill two birds with one stone and get the socket style dropout Trek I have always wanted and get a steel disc all around frame at the same time. I figure I can get he rear disc tab added and pick up a front disc fork from Soma or Salsa and have it converted by Cyclefab to threaded (another thing he's done before). I may or may not come out cheaper than an All City after it is all said and done but it would be that much cooler than a new mass produced frame.

I would be looking for something that could fit at least 32c tires (larger would be cool.) This will mostly be a commuter bike but I would probably use it in some local CX races and some light touring too. Which late 80's Trek am I looking for? 400? 330? And for those Trek purists that didn't head my warning to look away, I fully intend on sourcing a frame that has a finish in bad shape. I want to end up with a frame that is in better shape than when I found it, not ruin a perfectly good Trek for my disc brake fever dream.

Summary of Criteria:

Trek socket type dropouts (and seat cluster)
Enough frame clearance for knobby 32s
Decent tubing (I don't mind non-butted tubing in the rear triangle)

tiredhands 

If you want knobby 32s, you're looking at finding a frame for 27" rims. The socket dropouts started in '85, so that limits the number of models sporting 27" wheels. Looks like you've got the '85 400 series and the 520 from '85 to '89. It's slim pickins, but at least there are two options.

I'm not sure about the availability of 1" disc forks, but maybe there's one out there available a la carte.

One of these days I'm going to have enough pennies saved to get a custom disc fork made for my '89 520 and disc tabs on the rear. The aim is to get a swiss-army knife of a touring rig - swap in knobby 26ers for backroads, swap in floaty 650b for pavement. The same frame was used for 26" and 700c wheels, so I know that much will work

The Golden Boy 

Aside from being a 'Trek purist,' which, I guess I sorta am...

Is this a good idea?

I mean, the bike is engineered for the braking force to be applied and distributed at the brake bridge, not one seat stay.

Aubergine 

I suspect Colin would know how to brace the frame to handle the braking forces. Make sure you ask, Tricky.

For the fork, Nashbar sells one. It has mounts for both disk brakes and cantis, but Colin can remove those if you want. Also, if you do get a fork with a non-threaded steerer, you can just use a new headset for that, rather than trying to thread the steerer.

Chrome Molly

Part of me thinks that discs on horizontal drops might be fiddly.

wrk101

Since almost all of the braking power is up front, I would just get a replacement front disk brake fork and marry it to a Trek touring frame.

JohnDThompson 

The fork would need to be designed with disc brakes in mind. This would mean either an aftermarket fork (if you can find a disc-capable fork with a 1" steer tube; I've never looked), or a new, custom fork designed to take a disc brake.

The rear brake takes far less load than the front, and the rear triangle could be gusseted to reinforce it for the disc brake.

Brewsmith 

This.

Any combo of QR and disc is a bit fiddly imho. I have a stainless Alchemy frame that was a custom they did for someone several years back. It was setup for disc brakes with vertical QR drops and it was still a pain to remove and reinstall the rear wheel without some rubbing. I ended up having canti studs brazed on and went with a set of paul touring brakes and couldn't be happier

puckett129

I mostly ride early to mid-80's frames that have been modernized in terms of components, so I understand the inclination for the type of project you're looking to do, however, I think [objectively] that there's better options out there. The Soma Fog Cutter comes to mind if discs are an absolute requirement. Was the Space Horse disc the All-City you were thinking of buying? For me, the cool factor could be addressed by getting custom paint/powdercoat and doing what you want with it.

I like where your head's at and I know nothing about braking forces, etc. If you're seeking modern benefits like discs, I think a modern frame is the way to go. I've been OK doing my modernizations with long reach caliper brakes and decent pads. I fit 32's with fenders and get to customize the paint or keep it old school.

To address your actual question... my, hands down, most used bike is a resto-modded and repainted '83 Trek 620 (?) which I find to be versatile as can be. Perhaps not suited to cross races, but that's not likely your main goal since you're beginning with the idea of using a 30 year old bike frame as your starting point.



Either way, good luck and post pics if you end up doing it.

RobbieTunes

Given your intentions, I'm thinking a Trek 520. Nothing else comes to mind for versatility. I've seen them roadie, touring, cross, gravel, canti's and not. I'd think the frame can take it. Most I've seen have been beaten senseless and were still in normal use. Even in good shape, it's not like their color schemes were something worth preserving.

nesteel 

After it's all said and done, and the moneys's spent, what's the point of molesting a decent trek? Just pony up and buy something designed for your purposes, and be done with it.

ceelint

Wabi Thunder?

Bianchigirll 

Why do you want disc brakes? I’ve never used or worked on them but I somehow find them cumbersome. They look cool but seem hard to work with.

fietsbob

Large diameter straight blade , non tapered, better.. the disc brake force will straighten out a bent curved Blade ..

a little at a time..

Dfrost 

@gugie has built a frame with discs and a curved fork (search for “North Trask”). So this is a reach out to Mark to add his thoughts to this thread.

BTW, Jeff Lyon does custom forks.

gugie 

this

and this

The gravel bike I built was with a certain ride in mind. It has a few long, steep, curvey downhills. I’ve ridden it with cantis, centerpulls, and disc. My hands cramp up on everything but discs. While I agree that the current trend of discs on every bike is way overblown, there are some quite valid uses for them.

something to consider

gugie 

Based on my experience, I would use through axles and beefy, straight blades. I based my design somewhat on the original Elephant NFE. The 2.2” wide Rat Trap Pass tires are compliant enough so that curved blades probably don’t add significant shock absorption. My curved blades induce chattering during heavy braking as they flex and release-at least that’s what I think is going on.

I would would not consider a disc mod to a vintage frame, for the same money there are a lot of modern options.

fietsbob

Short, stiff, and straight-blated, is the forks on my Bike Friday Pocket Llama, disc brake..

Bianchigirll 

what about a classic drum brake?

gugie 

Better yet, an anchor.

Honestly, if you've ridden down a long, steep gravel road with tight turns and worried about having enough hand strength and stamina to hit the brakes one more time, you'll know what I mean. A good set of disc brakes, preferrably hydraulic, or at least a hybrid cable/hydralic set up like I use definitely has it's place. If 80% of the new bike market has disc brakes, maybe 79% of the market could use it. I know some people that say they're also great for wet commuting, but I don't see the need, and I live in Portland and commute year round.

Classic drum brakes were heavily used by some guys in Marin County several decades ago. The hill they raced down was called "Repack hill", which is what they needed to do to their classic drum brakes after every run. A good pair of disc brakes don't fade.

tricky 

This is what ends up happening. A brace is added between the seat and chainstays. https://www.instagram.com/p/BeHAQ_CD...by=haulincolin

tricky 

Will do. I was going to consult with him on this before even buying a frame.

tricky 

This is definitely a factor. Another thing to discuss with the builder. I know some Surly disc frames had track dropouts, but they also had disc tabs that allowed for for and aft movement of the caliper.

tricky 

A "mullet?" While I like that people call them mullets, there is something that rubs me wrong about two different brake types on the same frame. This is totally illogical since I have no problem with vintage mtbs with cantis up front and u-brakes in the rear.

tricky 

They are super nice up here in Seattle. You get braking consistency and power when riding in the rain. The bike stays cleaner without all the rim brake gunk that accumulates over time. You can beat on your brakes all you want on downhills without worrying about overheating. And you don't wear out your rims.

I conceded your point about a lot of disc brakes being hard to work with. I only use Avid BB7s since they are the easiest to maintain. I think the TRP Spyres might be similarly easy to work on but have never tried them. I will say that dual pivots are still easier to work on. But, IMO, cantis are the most mystifying method of stopping a bike that I know of.