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You can download the excel sheet in post #4 to run any simulation below the screen copy of 20/55 65 With the same 128 belt, this corresponds to a 494mm chainstay or 5mm more, so the bike needs to have at least 7/10 mm available to move the wheel back

From the gates calculation, we know 20/60 with the 130T belt would fit. Ravi can get you the right parts, and the shop install it. An hour of labor at most...

I am not following. There is a lor more work involved in replacing the rohloff by a derailleur than simply changing the sprockets and belt. Replacing the rohloff would mean not only replacing both sprockets as required for the belt upgrade, but also completely rebuilding a new wheel. So more...

Always happy to help :) Can you share how much range there is on the chainstay on either side of the nominal 489mm?

We cross posted. 2.5 is a minimum not a maximum, so no reason not to go to 3...

@Cybersnow Actually, 2.5 is a minimum, not a maximum. https://www.rohloff.de/en/service/handbook/speedhub/tables So there is no reason there would be a warranty issue by going to 3, it is actually recommended for higher torque an load usage

You should definitely do that. Normally Rohloff sets a ratio limit of 2.5. Unless you would be hammering the hub with max power in wrong gear, I am pretty sure that going to 3 (60/20) would be fine, but if you want to be safe warranty wise, it should be done with Zen's approval indeed...

If you are happy with the speed table I gave you for the 20/60 gear ratio, I think you are fine with a 130T belt. If you want to go with the 19/60 ratio, then using the same 130T belt, the chainstay is 493mm or 4mm more than what you have now. Gates recommend to have 10mm (.39") available...

I found the radius of the 55T, it is 95.4mm = 3.76" and the radius of the 60T is 104mm = 4.09" So the 60T will extend 8.6mm or 0.34" from the current one (a little under 3/8")

128T confirms the belt size 19 1/8 is 486mm close to the 489 that is the nominal for that belt and 55/20 sprocket. Probably the imprecision of the measurement. When you say 1/4 (6.35mm) or 3/8 (9.5mm), do you mean on each side of the axle (forward AND backward)? May be take a picture of the...

Good so you can go to 60. Now if you can confirm the 4 points above in my post #25, we can narrow down on the best upgrade scenario :)

I found a value for the chainstay on Zen site of 489mm (TO CONFIRM) If that is correct, the gates calculator tells me that a 55/22 would use a belt with 128 teeth which leads to a chainstay of 489mm Now if I use a 60/19 sprocket set with the same 128 belt, I get a needed chainstay of 481.5mm...

OK, so problem is It does not look like there is a 57T front sprocket, it goes from 55 to 60. So the closest to the 22+55 = 77 would be 19 +60 =79 at a pedaling cadence of 60, here are the result for 19 rear 60 front For a cadence of 70 So speed wise you are good with 19/60, but the...

@Cybersnow can you check what chainring adapter is on the bike? 4 bolt 104mm BCD or 5 bolt 130mm BCD

Why not increase assistance...

18mph on gear 14

Looks like gates sprockets for rohloff are available in 19, 20 and 22 https://www.gatescarbondrive.com/products/rear-sprockets?productline=cdx&fitment=rohloff&mountstyle=rohloff%20-%20splined Depending on the type of mount for the front sprocket, you can find below the available sizes...

Similar here, by the calculation in my excel sheet, with a 584mm rim (the standard rim for a 27.5" Wheel), a 2.4" tire, a 22/55 sprocket, at a cadence of 70rmp, the bike should be going 21mph. Can you measure the outside diameter or circumference of the rear wheel. a 584mm rim with a 2.4" tire...

I have an excel sheet that calculates speed in each gear with sprocket cadence and wheel size as variables. It has sheet tabs for each IGH, just click on the Rohloff tab Speed and gear ratio.xlsx You may have to download to change the variables