I'm pondering a custom-built gravel bike at the moment from a framebuilder who's done a friend's MTB. This custom frame thing comes to me from time to time and is usually an exercise in searching for components and researching frame specs more than anything. I'm back and forth between this and a Chinese carbon Carbonda frame as my current bike fantasies.
Still, now that I have an idea of what kind of bike I like and what the geometry needs to be, I'm actually tempted to get a detailed quote from the framebuilder guy (having already obtained a rough estimate a couple of years ago).
That made me think about building something with boost spacing for the rear wheel, a 73mm bottom bracket shell with a boost-specific MTB 1x crankset (possibly with a 38T chainring) for proper chainline etc.
Still, I wonder if that would make any sense, if it would require a boost fork etc. What do you think?
First off, it won't require a Boost fork. Whether you choose Boost for the front or the rear are independent choices, no connection.
As for the frame, I wouldn't recommend it. For the reasons the previous posters mentioned but also for pedaling efficiency. To me, one of the great things about (most) gravel bikes is the ability to run road cranks. A mountain bike crank has a wider Q factor so your feet are further apart. A Boost crank has an even wider Q factor, at least compared to the narrowest non-Boost options (for example SRAM non-Boost cranks come in 156 and 168mm Q factors, the Boost crank doesn't offer the 156mm option).
So now your riding like a duck, not a huge issue on a mountain bike but if you have a gravel bike that you use not just on trails but also on gravel and other roads where you have long steady stretches of just pedaling, I think you'd miss the efficiency of the narrow Q.
Ditto what they said plus the idea that you'd have a difficult time finding 11-speed hubs if you decided to run anything like a road gearing. Most Boost hubs are going to use XD drivers, Shimano/SRAM 10-speed, or, soon, Shimano Micro Drive [sic?]. Boost is meant primarily for wheel strength, by increasing the spokes' bracing angle on 29er wheels. That doesn't matter as much in gravel bikes, since you're not putting the same kinds of load on the wheel (or as large of tire, as someone else pointed out). I'd stick w/ 142.
Counterpoint. You go with BOOST spacing if you want to swap XC wheels/tires with your MTB and gravel bike. XC tires on full-suspension MTB can get your through some pretty gnarly stuff. While XC tires on gravel will everything but the gnarly stuff.
dangle wrote:Honest question: What is it that you want from your potential custom bike that Boost spacing will give you?
Basically because of this:
smoothmoose wrote:Counterpoint. You go with BOOST spacing if you want to swap XC wheels/tires with your MTB and gravel bike. XC tires on full-suspension MTB can get your through some pretty gnarly stuff. While XC tires on gravel will everything but the gnarly stuff.
Most new mid- to high-end MTBs these days use boost spacing.
Re: Q-factor, IMO is overrated. Everybody has different body mechanics, hip width, and femur/tibia lengths anyway. A bigger issue that people may not realize is a narrow Q-factor maybe compensating for muscle and mechanic imbalances that causes duck feet and collapsing knees.
Unfortunately, most shoes whether it be cushy sneakers, heeled dress shoes, or stiff sole SPD shoes, only make these imbalances worse.
With the right corrective exercises and shoes, one can ride a range of Q-factors without worrying about duck feet or collapsing knees.
Finally - if you go BOOST you can always use MTB cranks - albeit likely end up heavier than their road counterparts.
Most new mid- to high-end MTBs these days use boost spacing.
That's all true. I just can't think of an instance where I would ever want to run the tires I like for my mountain bike on any of my cx/gravel bikes. Or vice versa. I would consider popping one of the lighter weight wheelsets I race CX with on the mt bike with fast xc tires for the one or two race I do per year, but I haven't. That's just me though.
What kind of tires do you want to run on this gravel bike?
Boost doesn't really have anything to do with tire size except for the extra load that a large tire puts on the rim: the Surly Pugsley used 135 QR in the rear for a long time and my 2018 Epic has Boost but can only accept a 2.3 in the rear. You can definitely use mountain sizes without Boost spacing - the Surly Cross Check and the Specialized AWOL both clear 29x2.1 tires (depending on the model) with 135 QR spacing. It has way more to do with the frame than the hub.
Pynchonite wrote:Ditto what they said plus the idea that you'd have a difficult time finding 11-speed hubs if you decided to run anything like a road gearing. Most Boost hubs are going to use XD drivers, Shimano/SRAM 10-speed, or, soon, Shimano Micro Drive [sic?]. Boost is meant primarily for wheel strength, by increasing the spokes' bracing angle on 29er wheels. That doesn't matter as much in gravel bikes, since you're not putting the same kinds of load on the wheel (or as large of tire, as someone else pointed out). I'd stick w/ 142.
I think most aftermarket hubs come with 11s road freehubs so all you'd need is the included spacer to make it 10s. I'm not sure about factory wheels.
I think most aftermarket hubs come with 11s road freehubs so all you'd need is the included spacer to make it 10s. I'm not sure about factory wheels.
You're right. I build most of my wheels w/ DT Swiss 350 hubs, so I was thinking of those; they still offer disc hubs only with their mountain 10-speed freehub for some reason, even though they're compatible with road 11-speed.
Sure it does - it moves the chainline (and chainrings) outwards to give more room for bigger tires.
I think it's more of a coincidence that the two trends - wider frame spacing and bigger tires - are happening at the same time. If you're talking mountain bikes, the original justification was 29er wheel stiffness. That happened at the same time that plus tires were being introduced but the two things were independent, even if frame designs began to incorporate both ideas. Surly, Salsa, and a whole slew of small frame builders did plus tires without Boost spacing, and the example of the Epic was meant to show that Boost is used on bikes that aren't meant to take bigger tires. You could make the argument that it allows the chainstays to be shorter with a larger tire, but so does getting rid of the front derailleur. For gravel bikes, this is all pretty much beside the point because very few people are putting the same kind of hurt on their gravel wheels as they do on a trail-oriented 29er.
Boost is a rear hub spacing, not an axle standard. You would use the same thru-axle dropouts from Paragon as 142TA.
I'm aware of the spacing part. From perusing a document from Paragon I had the impression that either the shape or maybe their derailleir hangers precluded boost compatibility somehow. My bad.
You could make the argument that it allows the chainstays to be shorter with a larger tire, but so does getting rid of the front derailleur.
There's plenty of gravel frames with a dropped right chainstays to get shorter chainstays and still run road cranks, with or without front derailleurs. So I guess if your goal was to have fat tires, short chainstays, road-q cranks and large single rings, then Boost might be worth looking at as part of the total design. But other than swapping wheels with other bikes in the garage I don't see a reason to go Boost just because it exists.
