Rurui XT10 Gear upgrades

 

I ride mostly off road which includes steep hills, loamy sand and gravel, and technical trails.  The original gearing on this bike seemed more pavement focused and the gear ratios were too tight, and too geared for high speeds for me.  The original gearing had a 52 tooth chainring up front and a 28-24-22-20-18-16-14 freewheel. First gear was far too high for steep hills and technical stuff. 

Changing the chainring was simple.  I bought a 44 tooth chainring.  I swapped that out and it immediately helped but I did of course loose top speed.

I chose a Drift Maniac 11-34 freewheel with wider gear ratios than original 14-28.

Changing the freewheel on this bike is a challenge.  The axle nut is too big for even this special tool: https://www.area13ebikes.com/products/bafang-750-watt-freewheel-removal-tool-made-in-usa-by-bolton-labs, which I did buy for this job.

The connector is too big for the nut to go over and the nut is too big for the tool to go over.  I had the motor apart to see of there was an easy way to remove the wiring but no, it is all soldered in.  I did not want to hack the wiring up so I needed a better way.  I finally decided to get a larger fitting to replace the nut and slot it so the nut can be installed without having to go over the electrical connector.  Having a slotted nut is not great as it is much weaker this way so I found an item made for something different and modified it for my needs.  Here is what I used: https://www.amazon.com/dp/B07T18ZKH1?psc=1&ref=ppx_yo2ov_dt_b_product_details.  

Not ideal as stainless is softer than I wanted, and it needed significant modification to work for what I needed here.  I had to drill out the unthreaded end, reduce its diameter a bit (grinding), and slot it to fit over the wire.  Having a slot in a nut like this weakens it substantially but this is far thicker and longer than the nut it had.  Just to make it stronger, I bought a 7/8" shaft collar from Tractor Supply that goes over the special slotted nut to clamp it down which both locks it to the axle and eliminates the weakness caused by the slot.  I also had to grind flats on the new nut so I could tighten it on the axle.  The result, crude as it is, looks like this.

I was able to get plenty of torque on it, similar to the original nut.  The collar then locks it in place and strengthens the nut.  Now I can easily remove these to swap out freewheels.  Here is what the gear ratio comparison looks like, Opt1 being the new gearing.

Torque in this chart is just the ratio from original, 1st gear having 144% of original 1st gear torque for instance.  The speeds are derived from my "typical" pedaling cadence (estimated).  The lower 3 gears give more torque and less speed than original.  The upper 3 gears give higher speeds than the original.  This give a much wider ratio between the low and high gears.

My first ride with this new setup was much better at climbing hills.  In the more difficult stuff, I could power through in first gear now where I could not before.  At times I started having traction problems now where I would spin the real wheel.  I ordered a more aggressive rear tire as mine was worn and had a damaged sidewall as well.  After searching through all the options, I ended up with a Zol Montagna (available on Amazon: https://www.amazon.com/dp/B08KFMHLHJ).  

I have been on many rides since these modifications and the bike is much better suited to my off-road focused riding now.  Since this freewheel has wider ratios, it still works great for higher speeds on pavement too (actually can go a bit faster than before).   I have considered other mods like switching to a cassette style rear gear, going to a 9-speed, etc., but for now I am pretty happy with it.  I use that low first gear quite often off-road when climbing hills or in real loamy conditions and it makes a world of difference.  In super tight situations I can ride it in 1st without motor power and it is so much more useful than before.