Anyone who has used 1x with a gravel bike has probably experience this when descending. It's very real, and not sure how you'd stop it without significantly increasing freehub drag. It's simply momentum of the large cassette and coupled with a potential slight back pedal as you position your legs for switchbacks etc and there's a chance the momentary slack in the upper run of the chain will derail off the changing when in the small cog Not sure if they were running a chain catcher but it's probably prudent. Didn't see one on the treks that were set up 1x

While I haven’t put a ton of miles on my tt bike since Lyme wrecked my season least year, I didn’t have a single drop wit my 1x set up.
I purposefully took it on the roughest road I could and tried to make it fall off. 56 tooth Stone chainring, Sram mechanical red derailleur , 11-26 cassette. Maybe the size of the narrow wide ring I use helps. I have never dropped a chain on my mtb and I ride some really rocky stuff here

You ride a mtb with 1x and a nonclutched Rd or clutched?

Clutches for mtb and cx of course, tt bike regular Sram red derailleur.

Not replying to you in particular, but I've been experimenting with 1x setups on by TT bike for about the last four years and this is my N=1 experience.

1. Sram mechanical wi-fli (non-clutch) RD with NW chain ring - total of 3 chain drops in around 10 months of riding (all when coasting in the 11T over a very bumpy section)
2. Sram Force 1 (clutched) RD with NW chain ring - 1 drop in 12 months of riding.
3. Sram Etap Wi-fli RD (non-clutched) with NW chain ring - no drops in ~6months riding
4. Sram Etap with CeramicSpeed OSPW - set to medium tension - with NW chainring - no drops in ~6 months of riding.

For around a 12 month period between 3&4 I went back to a 2x setup (mainly because I did some hilly races and wanted a slightly wider gear range) and during that time probably had a 6+ chain derailments shifting the FD (admittedly, I used Q-rings which increases the risk of a FD mis-shift). Have since gone back to set-up 4. and will likely never go back to 2x on my TT bike again (I see Sram AXS 1x12 with that aero Quarq crankset in my near future... :) The Sram Etap derailleurs seem to have more tension than the older non-cluch mechanical RDs...

Putting a 1x Di2 system together for my tt bike.
-If I have a narrow wide chainring, do I need a clutch RD?
-XT di2 is compatible with road/tt shifter correct? (want to think so from seeing miss-matched gravel set ups)

Thanks

XT Di2 RD should be compatible and I've seen others get it to work, but it was giving us all sorts of trouble when I tried to use with road levers. Swapped to Ultegra Di2 RD and no issues. Any reason you wouldn't go with the new Ultegra RX805 RD rather than the XT?

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Amateur recreational hobbyist cyclist
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I use 1x di2 on my all road bike..I use the XTR rd, so it does have a clutch but not sure if it's required. I have it off unless I go offroad and dont have issues. Yes XT is compatible with road shifters, I just change the left side to be the same of the right side since I dont have an FD anymore.

you cant mix XT(R) with Road in the derailleur world..as in front(road) rear (MTB) or Front (MTB) rear (road)

thank you, I'll have to shop around wether I can find a budget ult or xt RD first (56 - 11/23 has me thinking a short cage non-clutch might do the trick)

P-R setups for trek. All on 1x

I had an idea to make a simple keeper out of carved aluminum angle. I think you just need a rigid piece of something that rides just above the chain at the high point of the ring. You could remove the hangar and bolt it straight to the frame. The aero hit should be nil.