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 āofficiallyā 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 wasnāt 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. Iām sure itās 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. Itās owner of Mosaicās personal bike, a GT-2X
Itās 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.
Thereās 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 Iāll be doing a lot more pavement than I will super rugged terrain, so Iād 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 Iām interested in doing very well.
Just as a point of clarification, to some good info, this is regarding the XX SL Thread On Power meterā¦ 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 āroad crankā on my mtbās 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 donāt see any third party manufacturers that will be willing to try to tackle such a detailed threading design. So youāre locked into Sram rings, and we can see now, that youāre somewhat limited in optionsā¦ (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. Iām 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 Iāll be sticking with the 38. Iām honestly not sure a 40t would fit anyway at a 55mm chainline, but I wanted to try. Seems like a no-brainer for the OEMās to skinny up the chainstay a bit to support up to ~44t. Not sure why they donāt 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, (Ć” la Seigla) is that you eliminate the possibility of running a shift cable or electronic wire through itā¦ With the prevalence of AXS, one could argue that its a worthy tradeoff, and weāre already seeing some of the big companies ditching mechanical compatibility, and Iām 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 isnāt 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 ānon-mtbā applications. We arenāt talking about needing bigger chainrings for XC courses, itās the gravel and mixed surface stuff where a 38 can be a limiter.
Iāve 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 itās far from ideal on others (even for amateurs without crazy FTPās). Iāve never done big sugar before, but have ridden/raced a lot of the gravel around Bentonville and I know there are sections where Iād 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 isnāt a no brainer. There is likely a tradeoff that 98% (made up stat) of XC bike buyers wouldnāt want.
For those two 2023 races that I did with the drop bar MTB, I had a rigid fork installed. Those courses werenāt bumpy, so I donāt think suspension would have helped for those particular races. Another CX course that I race on though has a fast bumpy downhill section, and when I used my hardtail MTB for the 2022 race (prior to my drop bar conversion) I was a lot faster on that bumpy descent, gaining about 5 seconds over other riders on traditional cyclocross bikes, who really struggled. My local CX league doesnāt have bike/tyre restrictions, so anything goes. So I think youāre right, on certain cyclocross courses suspension would help and might be faster overall, and I would put the suspension fork back on for some courses.
Even without suspension though, I think the wider tyres helped a lot. Some previous testing I had done, on a smooth grass field, showed that my wider MTB tyres had much lower rolling resistance on grass than my cyclocross tyres (see my blog post here for more details).
Technical regulation that grabbed my eye, from a local MTB race over the weekend. The race has about 20 miles of pavement or gravel, and 35 miles of singletrack. Iāve done it a couple times on a dropbar hardtail and couple times on a regular hardtail with flat bars. If it rains the course changes to a 50 miles pavement and gravel loop - no singletrack. The forecast this year was significant rainfall.
From what I can tell, some racers used gravel bikes the last time the rain route was required so this rule was created this year to keep everyone on MTBs. I didnāt register for the race this year and thereās probably only a few people who would have done it on drop bar MTBs but I thought it was interesting given their current popularity.
I donāt think handlebar difference is the determining characteristic between MTBs and Gravel/CX but I guess itās probably the easiest to define and enforce from a promoterās perspective.
I never ran this bike with flat bars, as I bought it solely to build it up with drop bars, and as such, sized down to a mediumā¦ Iād need something like a 120mm stem to run flat bars on it(100mm x -20d on my Large Epic Evo).
