Building a bike out of a pair of shif- I just wanted a gravel bike

-> break left hand shifter on road bike
-> get fed up of using bodged thumb shifter and upgrade to 11 speed
-> spare (now)1x10 mechanical sram shifters
-> time to build a gravel bike

Unfortunately actual gravel/adventure/cross/whatever frames are too expensive so converting an old mtb will have to do. Also they look cool. Enter ebay find which I probably payed too much for, but I like the paint and the triple triangle, a 2001(?) GT Zaskar Race:

Key features which will determine the build:

• came stock with a suspension fork, more on that in a second.
  
• somewhat inexplicably has a 68mm BB, so I can have road Q factor yay!
  
• IS disc mount so the canti studs are getting left alone.
  
• which allows for a wheel size other than 26", it should fit 650b*47 or 50, maybe 2.1".
  
• since the shifters that started it all are Sram, I can use any generation road 1x or 10s era mtb derailleur, probably more choice than is healthy.
  
  

The shifters in question, attached to some spare handlebars and a rather nice Kalloy Uno which unfortunately I will probably not be able to use because the frame is looooong.

However, before it can become a bike it needs a fork. Apparently the stock fork was a Rockshox SID XC which has an A2C of 450mm, so I need something in that range right???
The only production fork I can find that seems like the right thing is the Surly ECR in 27.5 which has 447 A2C and every mount I could ever want (I want lots of mounts). The only downside seems to be that it weighs almost the same as the frame so the ride might not be super SuPpLe, but I suppose that's what happens if you can't afford custom. I hope I'm not missing anything?

Looking forward to this

Hell yeah this is gonna be cool. Being in the process of making similar updates to my old GT, I have a couple of tips:

•68 mm BB yes, but you need to make sure that road crank arms will clear the chainstays. On my Palomar a set of GRX cranks has about 1 mm clearance each side and they hit the chainstays if you're pushing hard uphill.
•you could go for a fork that suspension corrects the frame like the ECR, or go for a shorter fork like a Straggler or Disc Trucker that effectively steepens the headtube and make the bike handle more aggressively. Mine has a Straggler fork and it's always worked great

Apparently the stock fork was a Rockshox SID XC which has an A2C of 450mm, so I need something in that range right???

You'd have to take into account the suspension fork sagging under your weight, so look for a rigid fork around 425mm

I mean could also go with a normal 400ish for with one of these…
https://www.ebay.com/itm/262344350511

Hmm, would the ride really be too weird with the Surly fork? It's the only thing I could find that has enough mounts - 3 pack specifically, could kind of get away with a central low rider and mudguard mount, but really not ideal. There doesn't seem to be anything else between 400 (too short) and 485 (too long). The head angle is already quite steep, 72° from measuring the photo upthread, which is about how the frame would sit with a ~450mm fork. I also measured the reach and it's looking like I'll need about a 60mm stem which I assume would help keep the handling a bit snappy.

Thanks for the heads up re: crank clearance! I've got a set of road cranks I can check with so I'll do that when I get the chance. They're currently on the pub bike, whose inadequacies as a gravel bike also contributed to this project :D

Great frame to start with. I’ve been running my early 90s Rudy Project with drop bars, 105 with cantis and superchonk-size tyres for some time. It’s easily the most versatile bike I’ve ever built. Does everything, goes anywhere and is generally indestructible. In the spirit of things, I’d recommend 1x at the front with a NW chainring. Don’t go too mad at the back, if you have like a 34T at the front and an 11-34 at the back it’ll give you all the range you need with big tyres.

as much as I like the triple triangle nothing you do in this thread will beat the muddy fox

This fate I am resigned to

I’ve done something like this with a Dynatech MTB frame. The results aren’t pretty but the ride is okay. The biggest hazard is avoiding arrest by the style police for putting Paul Motolites on a junk frame.

Similar paint to my Avanti Montari from 2000.

Surly also has lots of options in the 420-450 range. seems the way to go

Surly forks aren't light, but they're relatively affordable and I think the ride quality flatters a build like this. Not too stiff.

built my dynatech quantum like this, still love it

Wow I should've looked a bit more closely at all the options Surly had smh. I guess the Bridge Club fork is exactly what I'm looking for? Disc only, has 3 pack mounts, big tyre clearance, and 420mm A2C.
It'll steepen up the handling a bit but that's good since I'm running drops. There's also the handy side-effect of steepening the seat tube angle, which is nice because I run my saddle quite far forward.

@Slappingpythagoras glad to hear they ride quite well, the price and specs line up very well with what I'm after.

@hippy classic 2000s paint, I can't hate it honestly

@el_presidente love the gold stem, I'm quite tempted to throw something shiny into the sea of red/black/white :D

This was my old Monster.

The fork length of the surly will be fine. Generally a 420mm rigid = 80mm travel fork. 440mm rigid = 100mm travel fork

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Alright, wheels acquired! (Sellers pic) And yes I did get them because they had red hubs. Hopefully I am able to resist taking the red ano too far with this build but it will be difficult.

I've also found a 10 speed Sram X5 derailleur which (fingers crossed) should work with my 10 speed road shifter. Apparently it will clear a 42t cassette, so eBay sunrace type cassette seems the way to go, despite the questionable ratios at the high end. They also have red lockrings hehe

I still need to check crank/chainring clearance, but right now I'm thinking about brakes. It seems like Avid BB5 R are the way to go since they're fairly cheap and not completely shit? I know almost nothing about disc brakes, but I reckon I'll go for 180/160 rotors F/R unless someone stops me. The Avids have red bits too, so I may have to ban myself from any more red parts after that.

Hmmmmmm

That's a bit tight isn't it?

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what? BAGS of room : )

Well hopefully it doesn't clank, have got a couple of spacers to give it an extra mm but I'm not optimistic. I'll be sad if I have to run different cranks, it would be nice to have a power meter on here and entirely ditch the road bike for winter.

Meanwhile, lots of bits have arrived!
Surly Bridge Club fork, definitely made the right choice on axle to crown now I've got it on and had a look at the stance of the frame:

Round things:

Wiggly things:

Went with what I think are the biggest tyres I can get in the rear, 650b x 54 (27.5 x 2.1) Schwalbe G-one Bite. They'll probably be quite slow, but hopefully plenty of grip. Brakes are Avid BB5, they were nice and cheap.

As well as being a gravel bike, this is also supposed to be for bike packing, hence the fork with so many mounts. Carradice (for big and light things like sleeping bag, jumpers, etc), and frame bag will be supplemented by stealing the big front rack off the now fully commuterised Muddy Fox.

(Yes the saddle angle has been fixed, just put it on after confiscating the nice slr for the GT)

Lovely stuff.

I got arm strike in that spot using a H2 road crankset on a MTB frame (68mm shell but it needs cranks designed for 73mm). I thought about spacing it as you have but was worried about there not being enough grip on the nds crank (so I crimped the stay a bit … which I have regretted ever since).
Tl;dr - I don’t think you’re going to have a problem with it as-was, pre-spacer.

Cheers, fingers crossed it works out. Unless I'm mistaken the crank should technically flex away from the frame at that point in the pedal stroke, and I'm not sure if there's even that much torque in it at 3 o'clock anyway. Judging by the heel rub on the chain/seat stays someone has run the frame with pretty narrow cranks before, and there are no marks that look like crank rub, so that's reassuring.

Just think of the extra power and reduced drag

I have the G-one in 27.5 x 2.8 and mine are crazy gast. Maybe 2/3 km an hour slower compared to road tires, but soooo comfy

I have 27.5 x 2.1 G-one Bites, don’t really feel that slow but super comfortable so far on everything I would want to ride on.