jonathanf2

I recently swapped out my HG freehub to an XD freehub setup running a 10-42t cassette. I found the 10t most useful for quick sprints, riding downhill and to maintain momentum during top speed. Also most criticisms I read about the 10t cog wasn't an issue for me in actual use. I feel deficiency issues are just trade-off compromises with a 1x drivetrain. Anyways, I'm thinking of trying a 9-46t cassette and I'm curious on user feedback for those who have 9t cog cassettes with a GRX 11 speed RD? I haven't found anything conclusive from my searches and with varying opinions.

I'm currently running a GRX 812 RD paired to Ultegra 8020 shifters. My frame plus GRX 812 RD can clear the 46t big cog with a 38t chainring, but I'm thinking of dropping down to 36t or 34t to get more low gear while taking advantage of that 9t when in high gear. I also like that on the 9-46t the 2nd small cog is an 11t and the cogs in the low gear are closely spaced. I don't care so much about the middle range since I usually link flat road routes with hilly off-road trails so I'm always riding in the extreme cassette ranges. Also I'm meticulous with RD hanger alignment, all my chains are immersive waxed and I have several brand chains on reserve to get the best drivetrain performance.

Thanks for any opinions!

50PlusCycling

If you are talking about the E-13 cassette, it seems to have good reviews. I’ve run a Shimano Capreo cassette with a 9 tooth cog, and while the extra top end was nice, I found that the 9 teeth didn’t hold the chain very well, and it would skip under load. Adding a little tension to the derailleur helped, but never fully got rid of the problem. I’m not sure if this is an issue on the E-13 cassette, but I wouldn’t recommend anything smaller than 10 or 11 teeth for sprinting.

jonathanf2

For quick sprint attacks and to pick up speed on the downhill, I haven't any problems with the 10t, despite people saying it's worst than an 11t cog. I just did a group ride yesterday and that 10t cog came in handy to close gaps and catch up to the breakaway group. We were mostly all on gravel bikes, but there didn't seem to be much of a handicap against those on 2x setups. I haven't heard of skipping issues on 9t cogs. Were you using a new chain? I'm also immersive waxing which seems to help a bit.

50PlusCycling

New chain with the new cassette. I used to be the designated sprinter on our team, and could push pretty hard. In those days sprinters ran a 53~11 top gear, and could hit 70 to 75kph. The good thing about GRX is that you can run a road crank if you like, which gives you better top-end options. I run a 10~51 cassette on my bike with a GRX 822 derailleur, which is more for adventure rides and bike packing, it's a great climber. I had an issue with topping out my Moulton with its 20" wheels, and a 9t cog helped. But because of the skipping issue I moved to an 11t cog and swapped in a 54t chainring on the front. It now has plenty of top end, and no skipping issues.

Duragrouch

No personal experience, but on paper, 11T to 9T jump is a pretty large percent change, especially in top gear where you are near limits of power and pushing up against air drag. That percent jump between the two lowest gears is quite common. This is why, in the lower gears, you have more teeth difference between cogs. But in the high gears, you are limited in that you can't make a smaller jump than 1 tooth, even if you want to*. But you're doing an 11T to 9T jump by choice?

* Which is why some folks still like "half-step-plus-granny" chainrings, the half step, like 47/52 instead of 42/52, allows smaller difference between gears.

jonathanf2

I'm all for bigger chainrings for better drivetrain efficiency, but for 1x gravel in order to get my mountain climbing low gears and a useable high gear, I'm willing to compromise. As I mentioned earlier, I have no issues with 10t for how I use it, so this is why I'm willing to give 9t a chance. I guess there's not much experience with the 9t cog on this forum. I have a cassette on order, so I'll report back once I get one.

Duragrouch

Oh I don't dispute you wanting to go 9T, but based on the percent jumps and it being the high end, it just seems like you might want to go 9-10-11, and then start larger jumps. Depends how big the other gear jumps are, and what that does to your other spacing. By the way, entering your data into gear-calculator.com , and the spacing on gear jumps becomes really easily visualized, that's one of the additional features over sheldon brown gear calc.

Mine; Notice that to get close to equal-percentage jumps, the cog spacing needs to increase toward the low gear end. Which is why cassettes are not "straight-cones", but curved cones, unless it's an old road race cassette or freewheel that is "straight-block", 1T difference between each cog.

jonathanf2

The current 10-42t cassette I'm on has a 10t to 12t jump and the 9-46t cassette goes from 9t to 11t. In actual use, the jump in gearing isn't that bad, but you really need to precisely dial the b-screw adjustment. I see myself not using the 9t or the 46t cog often, but mainly using the 11t to 40t range mostly. I'm going to try a 34t chainring first on the 9-46t and if gearing feels too low I'll try a 36t or stick with my current 38t. I also might considering going electronic shifting in the near future, so that should help smooth out shifting as well.

At one point I was bias towards 2x gravel, but smaller cogs have me reevaluating 1x again.

Duragrouch

(above) Yeah I guess that makes sense, 2T jump at the high end, when you have that wide a range on the cassette.

I still like my 2X setup because I only have 7 speeds in back, so going wider steps there would be larger jumps than I want.

jonathanf2

I still think 2x is the best all-around platform for gravel bikes. It just seems 1x gets pushed more, but 1x isn't as simple as they make it out to be! There's all sorts of things to take into account like proper gearing for terrain, optimized chain line, different cassette standards (HG/XD/MS), etc. In fact all modern cycling just seems like a big mess. I had to replace a thru axle this week and it's all over the place in terms of thread pitch, thread length, axle length, spacers, etc. That's not even getting into bottom brackets!

Duragrouch

Mine is not a gravel bike but a road folder with 20" wheels, and it is now capable of doing 1X 400% range with modern derailleurs. That said, I do like my 2X when I am climbing hard in lowest gears, as that is where the most chain stress and wear occurs, and the chainline is better with an inner chainring going to the inner cogs.

jonathanf2

I'm reporting back regarding the 11 speed 9-46t cassette and GRX 812 RD. I initially had issues running the bike in stock configuration mainly getting solid shift performance across the cassette. It wasn't shifting great and I was beginning to think it was a total bust. I then remembered I had a Goatlink 10 derailleur extender in the drawer, so I decided to put that on and give it a try. Amazingly it works quite well. I'd say shift performance in the small cogs is very good and towards the middle-to-big cogs excellent. Since I'm not pushing a big 11-50t/10-50t cassette, the Goatlink+RD isn't compromising performance very much. I did slightly increase clutch tension which I usually leave ON, but it's still less than stock tension. I've seen some reports of people pushing 11-46t with no Goatlink, but I'm guessing it depends on the chain stay length, bike geometry, etc. I'm running an immersive waxed Shimano 11 speed chain and 12t/12t jockey wheels (to see if it'll take up some slack when in the 9t high gear).

I'll ride the bike extensively tonight and report on actual ride performance, but so far I'm optimistic it should run well.

Duragrouch

(above) Interesting. This gearing is not my forte, but my perception is the Goatlink usually lowers the RD. In the pic above, it looks like it is positioned to move the RD mostly aft, and given that the jockey pulley is still well forward, my perception is that before it was WAY forward; The old Dahon compact RD for their folders was positioned like that, and it shifted terrible, too much lateral flex in the chain going to the cog, so not positive shifts. So I could see how moving the RD aft helps a lot on yours.

jonathanf2

Here's a picture with the 10-42t cassette. I highly recommend this configuration for anyone on an 11 speed GRX setup and the ability to swap to an XD freehub. I find this configuration runs perfect and that 10t cog really comes in handy. The only reason I'm trying out the 9-46t is to get that higher gearing and also utilize that big 40t cog right before the 46t. The 10-42t jumps from 36t to 42t. I really view the 46t as an emergency bailout and I'm also not a fan of alloy cassette cogs since they wear out faster.




Anyways, I ran the 9-46t cassette last night on an 18 mile climbing and fast descent group ride. My tuning was slightly off and I forgot to tighten my crankset properly so I wasn't at 100%, but that 9t cog was like a shot of nitrous on the break away. I could keep pace with other gravel bikes both 1x and 2x using the 11t cog. When it came to attack, that 9t allowed me to pull away with a massive lead reaching the stop checkpoints first. Another observation is that I was having less chainring noise on the Goatlink versus the stock GRX hanger. I'm not a geometry expert, but the chain line angle might also be affected. Not sure if I can say it's a good or bad thing right now, but at least it's more quiet.