TT Bike Gearing – 1x or 2x
I’ve got a 2018 Cervelo P5 and run Dura-Ace 9000 (mechanical) as my group-set, with a Quarq D4 power meter. I’ve run the DA 9000 group set for 5 years now and I love it, absolutely no complaints. I have, however, been itching for an upgrade and given my frame is only 2-years old I’m not looking to change that; plus, I’ve got too much money in rim brake wheels to invest in a disc frame. I’ve been looking at the SRAM Red AXS group set since it was launched last year, and I’m intrigued, especially about the 1x capability.
I’ve looked at the various gearing combinations possible between the front ring and various cassettes and understand how those compare to standard two-ring set-ups. However, I haven’t yet ridden a 1x system on a road or tri bike.
Currently for my DA group set I run 11-28 in the rear and have 50-34, 52-36, and 53-39 chain ring options. I am planning on doing TC 70.3 this year which has ~2,500 feet of gain and targeting IMMT in 2021 which has ~5,900 feet of gain. Looking at the SRAM website, I could go with a 48-tooth ring up front and 10-33 cassette. While this affords me a wider range than a 50-34/11-28 combo, it does come with larger jumps higher in the cassette, meaning my "granny" gear could become a "grinding" gear.
For my riding here in MN, I know I’ll be fine with the 1x set-up.
My question for the team – do any of you run your TT bikes with a 1x set-up? If so, what has been your experience? What considerations should I be concerned with? TC 70.3 and IMMT veterans – are those hills long drags or shorter, punchier climbs? If you use a traditional 2x set-up did you want more gears than a 34-28 or 34-32?
Thanks in advance.
Comments
@Jeff Phillips I did IMMT 2017 with SRAM Red 11/28, 52/36 and no issues. (eTAP)
If you have a relatively healthy w/kg ratio, i.e., 3.0 or better for your FTP, you should be all set.
@Jeff Phillips - @John Withrow has a 1x setup on his new Ventum. I am toying with moving to it from my 2x11 after dropping a chain and FUBARing my IMLP race last year. I won't post for John, as he is an engineer, experienced with this and much smarter than me (but not as good looking). He has all the charts for gear ratios, etc.
Simply put you can have the same gear range as you have with 2x just bigger gaps between the gears. That said, JW furthered the analysis by removing the extreme cross chaining gears and the redundant gear, I think you end up at 15 or less gears, so you really aren't sacrificing much in the end..
Following just because @scott dinhofer said he is better looking than @John Withrow ... of course the 1x feedback will be interesting as well
I have never had a 1x but as @scott dinhofer noted my biggest issue I foresee is the larger jumps between gears. My biggest pet peeve is the 17-19 gap that is typical in most 11x25/28. For whatever reason I really like the 18 so I sub it in and create larger gaps in bigger teeth. Just a personal preference. A fair number of roadies in Virginia have made the switch and like it.
I am certainly smarter than @scott dinhofer on this particular topic (or at least longer winded) but he is scrawnier than me so there's that... Maybe we'll have to post a poll to see who's better looking, but for now, I think I'll give him the benefit of the doubt.
Regarding 1x, I built my new Ventum last winter as a 1x with 11 speed eTap (literally a month before AXS was announced). I will never EVER go back to a 2x on any bike EVER again... The 1x is such a simpler system and gave me the EXACT same gear ratio I had on my old P5 where I was essentially running a 52/36 and an 11/28 almost all of the time. The only time I ever took the 11-28 off was when I did IMFL and IMCOZ, because that was complete overkill for those courses. (technically I had a 50/34, but I ran Ossymetric chain rings for several years, so the exact numbers aren't apples to apples, but for purposes of the below, lets just pretend I was using a 52/36 with round chain rings).
Instead of re-writing all of my original 1x math/tables and explanations here, please go read this thread from before I built my bike up:
But if you run a 48T in the front and a 10/33 in the back, this will be what you get... and I'll put it next to my old baseline of 52/36 and 11/28 (10 spd) to show you exactly what you miss:
So you actually have an ever so slightly higher Top end, but at the expense of losing your biggest climbing gear. This would be the similar to running an 11-24 Cassette with a 52/36 Crankset. I don't personally think that's enough gears for MT Tremblant (unless you have @Coach Patrick types of W/Kg numbers, and sadly most of us never will). You'd need to go all the way down to a 44T on the front to get a climbing gear that I'd be comfortable with on and hillier types of terrain. Going with a 44T on the front would be a very similar range as riding with to a 52/36 Chain ring and say a a 12-28 Cassette. So as long as you don't might spinning out just a little earlier, this could work...
The reason I didn't immediately upgrade to AXS on my Ventum before completing my build was mostly because I didn't like these range constraints... I don't mind my cadence gaps at all... They are very similar to what I used to have anyways (since I always rode with an 11-28) until you got to your climbing gears... But while climbing, cadence gaps are mostly irrelevant anyways since you are almost always quickly ready to jump to that easiest gear anyways...
However, there are also a few other options/possibilities...
You could go with the AXS system, but get an Eagle XX1 RD (instead of the Road version). You'll also need an Eagle chain with this, but this would allow you to run a MUCH bigger cassette on the rear (the Road AXS maxes out at the 33). Here's a good article that explains some of these mix-and-match options: https://blog.3t.bike/2019/09/12028/gravel-tech-hacking-sram-axs-drivetrains/
There's also a cheaper option that will get you the exact same functionality without quite the same flare of having the brand spanking new AXS... Just do what I did and go with the 11-spd SRAM Red eTap. With the 11-spd, you can use the Wolftooth Roadlink adapter which is super cheap that will allow you to go with a much bigger cassette on the rear. For some reason, they don't offer a Roadlink that will work with the new Road AXS stuff, and I Google searched for an alternative and couldn't find one...
The 11-speed blip box is bigger (harder to hide from the wind), and the 11-speed is less future proof...
But at least gives you an extra thing to think about. I'm using a 52T SRAM Narrow-wide Chainring on the front and there are a million different options for 1x 11spd chainrings... There are a lot less options for 12-spd and they maxed out at 48t when I last checked. I'm not 100% sure if an 11spd chainring will even work with AXS. I have asked that question many different ways and never got great answer, but given the different roller shape of the chain links, the answer is most likely "not ideal if it works at all".
Here's how my gears compare to my old baseline setup:
So I get the exact same Top end and the exact same climbing gear... I lose my old 52/12 which I almost never used anyways... I also lost my old ~36/15 (which would generally be when I would have been shifting back to my big ring anyways). And I lost the 52/14 which is the only "new" cadence gap which I have never actually noticed or missed having...
It's cheaper than AXS (better deals on the older generation stuff). And I can confirm it works.
I have had exactly 1 dropped chain on my Ventum and that was 100% user error (vs. at least 1 dropped chain per every ride or two on my old P5). 99% of the dropped chains on my P5 (or any bike I have owned) were caused by my FD shifts... My only dropped chain with my eTap was flying down a giant hill at 50+ MPH in Colorado (from Maroon Bells), getting lots of chain slap after a full minute of coasting over a rough road surface, then immediately tried to pedal at ~100RPMs from a full coast during some chain slap. That was stupid and likely would have dropped any chain on any bike in the world (1x or 2x).
The biggest benefit of the AXS RD is having the orbital fluid clutch. This will give you a better tension on your chain in a 1x system and probably minimize some of the chain slap (which has been very minor in general for me, previous example excluded). But that clutch also create's a bit more drag in the system and with the Eagle comes with a slight weight penalty.
But personally I'd rather have better range options and cheaper install than a clutched RD. Because even though the Red eTap stuff is not advertised to work in a 1x setup, I can attest that it absolutely does work and is nearly flawless.
With 1x eTap, it is REALLY nice to "only" have to worry about shifting up or down. If I press the blip on either my right aerobar or my right bullhorn, my RD shifts to the right (harder gear), and if I hit either of the left blips with my left hand, my RD shifts to the left (easier gear). I don't ever need to think about timing my FD shift to my RD shift or think about when I will be cross chaining or anything else. Right button = upshift, left button means downshift.
So this answer is already WAY too long, so DM me if you want to chat live or if want any more details, or ask here if you want any lurkers or future searches to also be able to read them... I can't remember exactly where you live in MN, but I live in 55356 if you want to see mine in person before you take the plunge...
I've been looking into similar setups, and I am nowhere near a strong cyclist, so it was quickly abandoned for me. I just liked the idea of the setup for simplicity and my Trek SC has chain suck about every ride, with no solution from a bunch of different bike shops and much $ trying to fix it (even with di2). While researching the 1x option i came across the frictional loss problem of 1x and found it interesting. I am not a gearhead or a watt weanie. I could certainly gain more speed by losing 10 lbs than worrying about 4-6 watts from chain friction, but just interesting is all. Granted this was published in May, and I don't think this test was done with AXS system, so probably doesn't matter anyway.
@Jeff Horn What is your current setup front and back? Shouldn't matter what your bike power is unless maybe you are currently running a compact up front and an 11-32 in the back... but that can also be solved with a smaller front chain ring.
And regarding the friction chart above, it won't be as dramatic for my setup since I only have the 11 in the back and not the 10... And I'm running a 52T in the front, so mine will look very similar to the Blue line for most of it... But even if you lose a couple Watts going around the small cog of your cassette (and I'm not convinced that is actually true), you'd gain most (or some) of those watts back in the aero advantage from not having a front deraileur hanging out in the wind (especially at anything north of ~16+ mph which is most of an IM course). AND, some of that drag is supposedly from the angle of the chain... and if a 1x is setup properly the chain ring is pretty close to the center of the middle cog on the cassette, which means for 90% of your riding in an IM (i.e. the middle 5-6 gears), you actually have better chain alignment than a 2x meaning reduced drag...
The other incredibly stupid thing they did in that test was to test a SRAM Force 1 Rear Deraileur with PC-1170 chain in the 1x setup... But on the 2x setup, it was an Ultegra RD and an HG701 chain... I don't know why they would have used 2 totally different Deraileurs if they were only comparing 1x to 2x... This test would be much more interesting if say they used the AXS drive train (or 11 spd Red eTap) for both tests and simply changed it from 1x to 2x... I can see using the narrow-wide chain ring and chain for the 1x and normal chain rings and chain for the 2x, because then you can draw real world conclusions... but at least keep the RD the same... Who knows how much of that drag difference was just because of the particular angles in the Shimano vs SRAM RDs...
@John Withrow good points all around on the details of that test. Results don't seem to be valid if all the parts aren't held constant, except for front ring setup like you stated.
I am currently running 50-34 and 11-28. Preparing for St George with plenty of climbing, so will likely keep compact up front and go 11-32 in rear for plenty of low end. Im not a bomb descender so I don't need the top end range, but if i miss gears on the bottom, I struggle. Most of my climbing is done spinning at 90+, rather than grinding at 50-60 cadence.
There were a lot of strikes against the new AXS when looking, namely price with expensive group and having to buy new front chainring, and difficulty upgrading older model zip 808s to be compatible with the XDR driver for the 12spd cassettes (I have a Hope hub on there from re-dishing from 10spd to 11spd). Didn't want to re-dish or buy new wheels. I didn't look into the eagle option, but maybe will consider looking into it with your the excellent review you posted above.
@Coach Patrick @Brenda Ross ^^this^^ info fro @John Withrow is something that might be good as a wiki document if aggregated..
@John Withrow - is the 11-40 cassette a MTB cassette? can you post a link to the right one? I will need to send one to the guys at Lasco for modification to fit my zipp 10 spd disc http://www.lascoconcept.com/en/11s-cassette/
i have been running 1x for some time. the old etap. probably the ENer with the most experience with this ?
advantages/disadvantages of the old versus new as above. I will keep running the old etap due to the versatility and the low cost.
i don't find any significant disadvantages.
flat courses i do 52. 11-32. hilly 52. 11-40. i have Shimano and SunRace cassettes.
addition of products from Wolftooth. longer B screw. and for the 11-40, Roadlink derailleur extender.
@scott dinhofer I use the Shimano XTR 11-40 (Mtb cassette)
You If you don't care about an extra ~81 grams, you could save $140 and just buy the XT version
And as far as the @robin sarner comment above, he is absolutely the 1x expert in da haus as he was the OG that I modeled my Ventum build after... He literally held my hand, sent pics of his build and told me about the simple things like the Wolftooth Roadlink that I didn't even know existed... I'd say the main difference between our approaches is that I bought a single Cassette (XTR 11-40) and just leave it on for ALL riding conditions (flat, rolling, or serious climbing).
1x on my OMNI...love it. Made the change after reading @robin sarner 's and @John Withrow 's posts on the subject. I do swap my cassette often depending on the course (FLAT/ROLLING/HILLY)
I have the 11s etap...works like a charm
@John Withrow – Thank you for the wealth of information you provided, you’ve given me a lot to digest and consider. I very much appreciate the time you took to write your response. I had run similar gear ratio tables for a 50-34/ 11-28 and saw I was really losing my climbing gear, 1.21 (for 34-28) compared to 1.3 (for 48-33). I’m a 3.5 w/kg at FTP right now and hoping to drive that up but will take your point that 44-33 may not be enough gearing for that course. How would you describe the IMMT hills – long/ consistent drags or shorter/ punchier, mix of both? I understand there are some steep sections at the end of each loop and some rollers throughout? I think I’m fairly close to you (I’m at 55343) and will PM you if the offer still stands to come look at your set-up. I want to explore the options you laid out above and educate myself a little bit more before that so I can have better questions to ask.
@robin sarner – thanks for your gearing and set-up descriptions. 52 front ring 🤣 I wish!
@DAVID RICHMOND – What front right and cassette options set-up do you use for the different courses?
^^^^ Oops, I mean 1.45 ratio for 48-33 cassette above ^^^^
go 52 front. 11-42 back. Gives you everything you need.
Tremblant is sharp/short stuff at end of each lap. Long/shallow sections otherwise.