Full squish XC bike to gravel rig discussion

In my quest for an all-season crappy dirt road bike I'm giving some serious thought to converting a cross country bike with lockout front and rear to a dropbar bike. I almost bought a Niner MCR frame since they have them priced at $1299 right now but they can only fit  2.1" 650b tire. I'd like to run a 29-2.2ish tire.

 

Looking at bike weights and prices I could easily score a top of the line 5 or 6 year old XC bike like a Giant Anthem or Trek Top Fuel with carbon wheels and xo or xx1 12 spd drivetrain that weighs about the same as the MCR. I am wondering about a few details:

 

1. I normally ride a 58cm gravel bike. Should I go with a medium XC bike and then put on the drops? I wouldn't want a dropper so I worry about having a ridiculous legnth of seatpost exposed.

 

2. My biggest concern is getting a big enough chainring on the bike. Will most of these xc bikes take a 42t ring? 

 

3.I would put on a AXS mullet setup and use the existing 12 spd cassette. Would the SRAM mtb calipers work with SRAM brifters?

1.  If you want to use drops you will most likely need a medium.  Most mountain bikes made in the last 5 years will probably be around 60cm (or longer) for the top tube in a medium.  Size your stem accordingly to get the reach you need.  You likely will need a really long seatpost, like 400mm.

 

2.  There aren't going to be many (if any) modern mountain bikes that will fit a 42t.  But honestly with 29x2.2 tires do you really need a 42t?  29 x 2.2 tires using a 42t with a 10t cog is the equivalent of a road bike with 700 x 28 tires using 50t with an 11 cog.

 

3.  You can find the SRAM brake compatibility chart here.

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Please post pics.

I've done this and while it was a fun project, in the end it wasn't worth the hassle to try and get a good fit on the MTB conversion.  I did this on my old Vassago Jabber (which is longer than most frames) and the Giant HT my son grew out of.  I had better success with the much smaller Giant frame but eventually went back to flat bars with bar ends (for more hand positions).  I only use it at the cabin so it doesn't get ridden that much.  I have it set up with something like 32/22 in front and 10 speed in the rear, along with 2.2 tires.  On the gravel roads, that's plenty of gearing. 

 

Surly does make the corner bar (I think it's called) that is sort of a drop bar and made to run on MTBs.  Go over to mtbr.com to see what others are saying.  There's lots of these discussions in the gravel bike forum there.

 

Good luck and yes, post pics if you do this.

I spent about six years in Victorville, CA which is the high desert/north side of the San Gabriel mountains.  My first iteration using bikes I had available was to put drop bars on a front suspension fat bike and build new 29er wheels.  I liked it, but it was a beast when I hit paved climbs and the position was too upright.  My next attempt was rigid and It just did not work.  No. 3 was a Niner frame with xc 100mm fork.  I really liked it but wanted to run aerobars offroad (the wind in the high desert was incessant) and started wondering if you could ride aerobars offroad with a dual-suspension.  I eventually found a Turner Czar xc bike that I pulled most of the MTB components and also converted to electronic at the same time.  To create a more road-bike position, I built a 650b wheel for the front and kept the 700 at the back.  Because the climbing is steep, long and often at altitude, I went with a 40x11/24x42.   

As I started riding it, I quickly realized I wanted small bump compliance so I let out the pressure and run the front and rear 100mm shock with a lot of sag.  I probably only get 50-60mm of travel.  

The result was a bike that felt like a road bike position but that I could ride on the non-graded, washboard dirt roads around here.  It quickly because my favorite bike, perhaps that I have ever owned.  There are hundreds of miles of dirt roads that I can access in like five minutes of riding and now I had a super comfortable bike to ride them.  

I have realized I'm not a true mtb'er at all, but really prefer dirt and double tracks with lots of climbing, which this bike excelled at in nearly every way.  

The front Fox shock locks easily and the rear suspension is so well designed that I rarely even bothered to lock it.  

I mostly ran a combo of Thunder Burt front/Race King Proection rear for float because there was enough sand that 40mm would require hike-a-bike more than I like.

Anyway, it is a great bike that now hangs in my garage because I moved to Utah,  and my location is far away from dirt and the Utah mountain roads are much better paved than my favorites in California.

I never got back to my drivetrain system.  I used Shimano Ultegra di2 levers with an XT rear derailleur, bar end shifters and a climbing shifter so that I could shift from any hand position.  I started with a off-brand cassette and when that wore out I used an SLX cassette.  It required a lot of chain, usually the entire 116 links and so you had to avoid small ring with the 13, and obviously the 11, but otherwise worked great.  In the beginning, I used the non electronic XT FD (which required the above described situation) but after about a year, I found a di2 XT front and then the di2 would not shift into the 11 or 13 which was really nice (On occasionally rough terrain, I would shift the front ring before moving up the cassette and that caused some issues with dropped chains).

This bike covered a good 80 percent of my cycling needs with the two extremes being really rough off-road stuff and smooth paved climbs where it was not the best choice.

It really excelled at mixed-surface rides where I could jump from dirt to pavement and back many times during the ride.  I used it to race the Utah and California gravel raced that don't have nice smooth gravel, usually have a lot of climbing and some rough descents.  

A really great bike. 

1) I'd ignore the sizes and go by stack/reach. You're looking at an era where geometry was changing and letter sizes or TT length may not be that helpful. 

That said, I'm super happy on my 58cm Warbird and also have a vintage 2009 size M hardtail MTB converted to drop bars. It works very well, but I honestly wish it were a large to get more stack and seat tube. More stack because in the places where I want this bike, I also want my bars closer to level with my seat. More seat tube to make more room inside the main triangle for bags and bottles, plus less seatpost. Yes, the bike has a ton of seatpost. Oh well, it only looks awkward when I'm not in the saddle. 

The problem is of course if you get too modern in MTB geometry, then the larger sizes have too much reach to work with drop bars. I would definitely go into this looking to run a shorter stem than typical for a gravel bike. Maybe 60-80mm stem length. 

 

2) I'd ask around on owners forums. Go as big as you can fit.  On my bike, since I put on Conti Racekings I do find myself hitting 42x11 in a lot more places and wondering about a bigger ring.   

 

3) ask SRAM?  I'm running SRAM 10sp where the road and MTB shifters are cross compatible since my conversion well predates all this AXS stuff. 

I've scrounged around quite a bit and just haven't come up with a XC frame that would do what I wanted. I know that Lachlan Morton runs big chainrings on a Cannondale xc bike (as do about all pro Leadville 100 racers) but I don't know how they do that. Those frames are usually restricted to a 36t ring at most when you look at the literature. I suspect they are running a wider crank axle and spacing it out to where the chainline is funky, running it outboard a ways. I know that oddball chainlines are pretty common with gravel racers who want an optimum chain alignment in the smaller cassette gears.. 

 

Long story short, I went ahead and bought an MCR frame for the $1299. That is a bargain by any standard and I already had a fork and wheels for it. I did a bit of Black Friday shopping and have it built with an Eagle AXS mullet setup, Rival brifters and powermeter cranks. Our weather has been uncooperative but am hoping for a first shakeout ride this weekend.

Still have a few things to do; grip tape, longer and lower stem, setback seat post will get it in the ballpark but it's close to done.

That's coming along nicely and a very capable ride to tackle more than just gravel.  I dig it!

Those are 45mm Ramblers on it in the pic. It is supposed to fit 50mm so I may order a set of those. I do have a nice set of 650b’s with 2.1” Thunder Burts though so I’ll give those a try before I buy different 700c tires. 

It weighs 24.3lbs with pedals as pictured, has a Quarq power meter, Ritchie carbon bars, Rival AXS shifters, GX der and XX1 51t cassette, HED GC3 wheels. All but wheels were bought on Black Friday sales.

The Rival/Quarq crank is pretty heavy and so is the AXS der so I suppose the bike could be built to around 23lbs with a full weight weenie build. Definitely not worth it when it will never be a race day bike.

I had the Rudy fork on my carbon Norco Search XR which went from 19 lbs to just under 22. Basically paying a 2lb penalty for rear suspension with this bike. My plan for this bike is to be an everyday rider and keep my Norco for premium road conditions and races.

Gotten a couple rides in. Very happy with it at this point. It's no race machine but it really is a magic carpet ride.