Nessism

Has anyone made a lugged gravel frame? I'm itching for a new project and was thinking gravel bike. I'm comfortable working with lugs so that would be my first choice.

As I understand it a gravel bike is very similar to a relaxed geometry road bike with a lot of tire clearance. How does a gravel bike differ from a cyclocross bike? Cantilever brakes on a gravel bike?

I imagine building in adequate rear tire clearance would be one of the main challenges.

I've got a Daza XL OS lug set and one of Kurt's XL OS bottom brackets courtesy of Andy laying in wait.

Anyway, just thinking out loud. Please share your thoughts and recommendations.

unterhausen

That's what I'm slowly working on. You have to bend the chain stay ports of the bb shell. I am using the Columbus flat mount chainstays. The chainstays are not going to be particularly short. Probably clear 700x40 or 650bx 50-ish.

8aaron8

I have built a couple of lugged gravel bikes. Unterhausen is correct that you will likely need to bend the chainstay ports outward to accommodate wider tires. If you build the fork yourself there a few options of wide crowns on the market, Pacenti comes to mind. You could use cantilever brakes on a gravel bike but then your limited to one wheel size. I'm not typically in the disc camp for road bikes but on a gravel bike it makes sense because sometimes a 650x48 is the right tire and sometimes 700x38 is the way to go. As you mentioned gravel bikes are a bit more relaxed than a road frame, be aware of wheel flop when designing the front end which becomes more a reality when you slacken the head angle and kick out the fork rake. Also, compared to a CX bike the bb drop can come way down. Lastly Rene Herse sells their BB shell with matching bent chainstays that clear a lot of space in the back, if you don't want to do a lot of manipulation it's a nice option, though almost 2x the cost of any other bb shell/chainstay combo. Here's a stainless steel lugged gravel bike I build last year.

Cynikal 

One issue that you will run into is the DT/HT junction. Unless you raise the BB a bunch or slacken the head tube it's hard to find lugs to fit a 58 degreeish DT/T junction.

unterhausen

I always worry about the DT head lug, but the angle on my design is 59 degrees, and the lugs are 60. So I probably won't have to bend the lug. Granted, I have 75mm drop, but I ride on enough rocks that I have hit the crankarm on them and I don't think the difference between 75mm and 85mm is particularly noticable. I'm sure my current (production) frame has some ridiculous drop, like 60mm or something.

Longer forks make up for the other factors a little. The A-C on my design is 395, which is very common for gravel forks.

Nessism

Whoa! That's a long fork! What brakes are you using?

Suggestions for chain stays? Some sort of S bend I suppose but which ones?

Plobryan

I built one and had wider chain stays. Unfortunately they were so wide a traditional road crank won’t work (q factor too big). So the only option is a mountain bike crank. It works but know that your options may be limited.

unterhausen

I'm not sure anyone has the life flat mount chainstays right now, all I looked at was framebuilders supply and they are out. The other option I have looked at was the Zona cyclocross s-bend. I don't really like the bend on those though. If you use a long dropout, you probably would want to bend the dropout.

dsaul

395-400mm Axle to Crown is standard on almost all current gravel and CX forks. It's best to design your frame so that it doesn't need a custom fork to maintain its geometry.

unterhausen

It seems like some of the newer gravel forks are even longer, like 405mm. Since this bike will have 1 1/8 steerer, I am not closely monitoring the carbon fork market. I'm pretty sure I can get a carbon fork for it in 395mm if I want. I have thought of making a fillet brazed frame with a tapered head tube, so maybe I'll look more when that gets closer to being realized.

Cynikal 

If you are looking for a carbon fork for a lugged frame, the Ritchey CX fork is a good option. 52mm of tire clearance and a A-C of 383 mm with a 1 1/8 steertube and flatmount brakes. I nice option for lugged builders.

https://us.ritcheylogic.com/us_en/wc...on-gravel-fork

guy153

That's lucky. I make the fork first and then measure it before finalizing the frame design. My unicrown came out at 407mm, which seems to be anticipating the latest standards! Completely by accident.

unterhausen

I design the fork first based on what I want it to clear. I usually make sure I can build a frame around it before I build anything

Nessism

What brakes for a 400mm long fork? Disc?

unterhausen

Discs. I wouldn't use anything else given the terrain around here. I suppose you could use rim brakes, you wouldn't have to worry as much about the fork blades. But in general, I don't think it's worth fighting the industry over discs on gravel bikes.

It's nice to be able to design around different size wheels and not worry about brakes, although I expect that I'm going to stick to one size or the other.