In terms of pure bike fit you should strive for typical bike fitting measurements. But not the very basic Saddle nose to end of stem (handle bar mounting point) and rather “middle” of the Saddle to the Hoods. So if you would transfer these over from your other gravel bike or get from a bike fitter you will know what to build up.
Yes, certainly - the feel on the bike might be different to what you previously rode if that new frame has a totally new geometry with longer front-center and maybe other parameters. So maybe once being able to ride it you might decide you actually want to sit a bit longer or a bit shorter and what not. But at least the bike itself should fit you.
Best would be if you could ride that frame as a complete bike (even if it has a rigid fork). This would give you confidence in your choice, especially if you are unsure on the exact sizing of the frame or how you would like how it handles.
Edit / addendum: Especially in light of the very valid point of @JonGreengrass I assume that the frame you have your eyes on already has a suspension corrected geometry like quite a number of new gravel bikes have these days. If not, then indeed you should expect some steering differences resulting from a risen front end (leading to a slacker head tube angle) which may or may not put the steering more or further away from the direction you prefer.
FYI - For anyone running the new SRAM XXSL crank and wanting to fit a larger (>38) chainring on their MTB, the new RED XPLR rings use the same diameter/pitch as the threaded MTB rings.
The XPLR rings are available up to 46t, but unfortunately have a 6.5mm offset. So, while you can get a bigger ring and it threads onto the crank fine, the ring is offset closer to the chainstay compared to the MTB chainrings (which are available in 0 offset or 3mm offset). Depending on the model of XXSL crank you have (168 vs 174 Q factor), that makes the chainline either 51.5mm or 48.5mm with the XPLR rings. The 51.5 chainline should be fine from a shifting standpoint, but not likely clear the chainstay on a frame that “officially” maxes out on a 36 or 38 chainring with a normal chainline.
So, how did Keegan run a 42 ring on his highball at leadville (which officially supports a 38t max)? Based on my discussion with a guy at SRAM (who wasn’t involved with the setup, but aware of it), Keegan ran the new XPLR ring and shimmed the crank over to the right a bit to provide extra clearance. And he also mentioned that the ring was rubbing the frame at times, so not a great solution.
Anyway, the 6.5mm offset is a challenge, but it sounds like there is at least a hacky option to run a larger XPLR ring for people willing to shim their crank to the right a bit. I’m sure it’s highly dependent on the frame and how tight it was with a 38 to begin with. It would be nice if SRAM (or aftermarket) would make a compatible zero offset ring in 40 and 42, I think that would work on many frames without shimming (at least for the 40).
I was at MADE last weekend and saw that bike. It’s owner of Mosaic’s personal bike, a GT-2X
It’s a very very capable bike, but to fit the tires and such the geometry does differ more than your standard gravel bike. It seems that (largely) the wider tire clearance you get, the longer the wheel base gets, the longer the chainstay gets, it changes the fork angle, requiring a shorter stem and altered handling. The main problem is having proper chainring clearance at the chainstay to still permit a wide enough tire as they basically overlap. Carbon fiber may be better with this as the tubing dimensions can be worked a bit easier than titanium. Some titanium builders are doing 3D titanium for that section to allow a little more clearance.
There’s give and take with everything. I settled on a Mosaic GT-1 45 with custom geometry that I put the down payment on this week. It lacks a little of the tire clearance, but also has geometry closer to a road bike. Everything seems to be a bit of a trade off. I know I’ll be doing a lot more pavement than I will super rugged terrain, so I’d rather be better off for the pavement rides than the super technical gravel/single track.
My next bike will likely be something that better blurs the line between single track & super chunky gravel, while the GT-1 45 will be on the line between regular gravel and pavement. A two-bike set up should suit most everything I’m interested in doing very well.
Just as a point of clarification, to some good info, this is regarding the XX SL Thread On Power meter… Not just the XX SL Crank, which still has the same 8 bolt pattern spider mounting, and can use any offset ring.
I measured the standard 1x direct mount road rings that come on the range from Apex to Red to have something like 8mm offset, which was part of why I was easily able to get away with a “road crank” on my mtb’s by simply using a 0mm or 3mmm offset ring. The fact that you can get varying offsets is a huge appeal to this system. From launch, the thread-on chainring was a little less appealing to me, as I simply don’t see any third party manufacturers that will be willing to try to tackle such a detailed threading design. So you’re locked into Sram rings, and we can see now, that you’re somewhat limited in options… (The other downside for me, which is admittedly niche, is the special tool required, which is a big turn off for the self supported ultra distance bikepacking type races I do.)
Thanks for clarification, I should have better highlighted that this was the new threaded ring version.
And I had the same reservations about going this route on the new bike. Lots of downside if wanting to go aftermarket rings (oval, different offsets, etc.) and the rings are kind of stupidly expensive. My main concern was ease of switching rings and that has been a pleasant surprise. Even though you need a tool, I find it to be a better system if you swap rings all the time. I’m a compulsive ring swapper and I tend to go through chainring bolts constantly (cracking/breaking them).
I was thinking about running my new Epic at big sugar this year just for fun (C race). Was hoping to fit a 40t ring, but looking like I’ll be sticking with the 38. I’m honestly not sure a 40t would fit anyway at a 55mm chainline, but I wanted to try. Seems like a no-brainer for the OEM’s to skinny up the chainstay a bit to support up to ~44t. Not sure why they don’t do that, but I guess it probably has some impact on suspension behavior on a FS bike.
Part of their hesitation in slimming down the chain stay, or making it solid, (á la Seigla) is that you eliminate the possibility of running a shift cable or electronic wire through it… With the prevalence of AXS, one could argue that its a worthy tradeoff, and we’re already seeing some of the big companies ditching mechanical compatibility, and I’m sure more will follow suit, especially if Shimano ever gets around to offering something similar.
Yeah, nixing the cable routing would be fine with me (especially if it allowed a bigger ring). Specialized did it on the new s-works Epic 8 frame (both for shifting and dropper) to save weight. They left the cable routing for the non-sworks frame, but I think they only sell one lower end evo model that you can buy with mechanical shifting.
I am guessing this isn’t as easy as you think it might be. There is always some trade off. It is already a tight space to balance tire clearance, chainring size, suspension movement, suspension performance, weight of the frame, and geometry of the frame. And if there a compromise to be made in any of those, why would you make that compromise when there is very little need/demand for rings 40 and above. You are talking about super niche use cases here that these bikes are not designed for. Even the pros generally only go up to a 38 on real XCO courses.
Yeah, but a bit part of the theme of this thread is using a MTB for “non-mtb” applications. We aren’t talking about needing bigger chainrings for XC courses, it’s the gravel and mixed surface stuff where a 38 can be a limiter.
I’ve done quite a bit of gravel racing on my FS MTB and there are only 2 things that I consider significant limiters - Aero position with flat bars (the primary discussion here focused on drop bars to address that) and gearing. A 38 works OK on some gravel courses, but it’s far from ideal on others (even for amateurs without crazy FTP’s). I’ve never done big sugar before, but have ridden/raced a lot of the gravel around Bentonville and I know there are sections where I’d be much better off with a 42 or 44 compared to a 38.
All good. But you suggested that it was a no brainer for OEMs to allow 40+ chainrings. I was just suggesting reasons why it isn’t a no brainer. There is likely a tradeoff that 98% (made up stat) of XC bike buyers wouldn’t want.
Nice. I wonder how much is due to the suspension over the tires. Our course yesterday that got me thinking was incredibly bumpy and rocky. Just having suspension I feel like could have taken a minute off your lap time. Especially after 5 laps of getting shaken like you were operating a jackhammer. Not to mention probably 40-50% was on single track or the bumpy fields. Just soaking up the bumps and rocks would have saved so much energy and fatigue.
