New bike on the way

 I finally ordered a new electric mountain bike.  After long research I decided on the Biktrix Juggernaut Ultra FS Pro 3.

I have now put over 1,100 miles on my Rurui XT10 and I have learned much about what I needed for where I ride.  I chose the Biktrix bike because:

• Bafang M620 ultra mid-drive is the best motor for serious off-road with steep hills and loamy terrain that I ride in.
• 52V batteries are more efficient and powerful with the M620 motor than the typical 48V.
• 11 speed cassette with 11-42 gears supports a wide range of riding conditions, including steep hills and loamy terrain. The bigger rear gears will work much better in the technical or real steep riding.  It is a proper cassette too, instead of the screw-on freewheel than has limits.
• Fat-tire and full suspension for serious off-road riding.
• It has an optional add-on battery for extra capacity when needed but easily removed to reduce weight when not needed.  Main battery alone is 126% capacity of the Rurui.  With the additional battery I will have 220% capacity of the Rurui.  I have only run the Rurui out of power one time so while this will be nice it is likely more than I will generally need. This will give the option of longer, steeper rides at higher speeds.
• Air shock and forks.
• Inverted fork has less un-sprung mass and is more rigid. 

The next best option I found in this price range was the Eunorau Specter S.  It was less expensive than the Biktrix.  It has the same motor and 11-speed cassette. It used 48V instead of 52V and lacked the air suspension.  Besides, it is hard to pronounce the name.  

The Rurui was great for street riding and off-road in less steep areas.  The rear hub drive did not provide enough low speed power for climbing for where I like to ride.  It did great at speeds from 11mph and up but for lower speed technical stuff, or long steep hills it did not work well.  

I also looked into more aggressive off-road bikes that were closer to electric dirt bikes.  Here are some examples.

CAB Motorworks. They make bikes from 750W all the way to over 20kW.  These are based on motocross bikes more than bicycles.  They had some very appealing features such as proper motocross suspension, wheels, and tires and regenerative braking.  I also like the moto seat option.  However, these would not be welcome anywhere but off-road.  They would not pass as a bicycle to most people.  They are also much heavier that most ebikes and are single speed (pedal).  The one I was most interested in was the Falcon.

UltraTRX. They make a range of off-road ebikes that include bike that are based on the higher end of ebikes all the way to motocross bikes.  The Cheetah looked the most interesting to me.

I ordered the Biktrix but it has not shipped yet.  Once I get it and take it for a few rides, I will post about it here on this blog.  

Tighten a loose freewheel on the trail

 I have had bicycle freewheels come loose while riding, many times and on multiple bikes.  Here is a video showing it.

You start to hear and feel a knock, worse in some gears that others.  As it progresses, it may struggle when changing gears.  If you let is continue, it will come apart and leave your stranded.  

Maybe I am the only one that seems to have this problem but I doubt it.  The first time this happened I was out in the desert up a long hill.  I felt it happening but did not stop to check into it.  It finally got so bad the freewheel came apart and locked so there was no ratchet action anymore and the pedals just followed the wheel.  It made for a long trip home.  My bike was under warranty so I got a whole new rear wheel assembly.  The new one did the same thing.  This time I caught it early.  Normally you need to take the wheel off and use a special spanner for this.  I only had some basic tools I carry on the bike.  I finally used a Philips screwdriver and some ingenuity to tighten it back up without taking anything apart.    

Here is a photo showing the freewheel off the bike so you can see how to place the screwdriver.

There are small holes for the spanner. Push the Philips screwdriver into that hole at a bit of an angle. Since the bike will be assembled on the trail, there are only a few areas where you can even see this part of the freewheel.  Generally in the slot where the axle bolts to the frame.  While pushing in hard on the screwdriver, rotate the wheel in the forward travel direction.  This will cause the whole freewheel to move with the wheel but since you are holding the freewheel nut with the screwdriver it will stop against the frame and tighten the nut.  Since you have the leverage of the whole wheel diameter, the weak point of this is keeping that screwdriver held tight into the nut hole.  You can help this by holding the screwdriver at a bit of angle.  Hard to explain in words but it works well.  

The freewheel bearing preload is set with shims, not a specific torque, so you really can't overtighten it, especially since the screwdriver approach does not give enough grip to overtighten it.  

Biking Websites

 I enjoy mountain biking, especially off-road mountain biking.  Over the years I have found some handy websites for mountain biking.

First of all I use a Garmin smartwatch to track my rides.  I had a Vivoactive 3 first, then upgraded to a fenix 6X Pro Solar.  I use Garmin Connect and Garmin Explore website the most since they have the most detail for a Garmin user.  Since my rides take me outside of cellular coverage, I also have a Garmin InReach Messenger to track and stay connected.  Garmin has done a fantastic job with these devices.

Here are some other website I discovered and use:

• Strava.  This is a social biking website.  It sync's with Garmin well so my rides tracked with Garmin Connect also post to Strava.
• Trailforks.  This site is a place to find and share routes.  
• PinBike.  This includes classified ads for bike stuff.

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.  

  

Mountain Bikes

 My favorite form of exercise is biking.  I really prefer to ride on designated bike paths or off-road versus on the street.  I currently have 3 bikes.  

Hybrid Mountain Bike

My oldest is a 2013 Specialized Crossroads Sport hybrid (mountain/road) rigid frame, no suspension. I bought this bike in 2014.  At the time of this post my Garmin watch recorded 830 miles but I did not get the watch until 5 years after I bought the bike.  I would guess I have closer to 4,500 miles on this bike.

Full-Suspension Mountain Bike

In December 2020 bikes were scarce.  Most bike shops had very little available and even used bikes were hard to find.  I found myself looking for a full-suspension mountain bike at a very bad time.  I happened to be shopping at Walmart one day and they had a Kent Flexor in stock for $148 so I bought it.  

I was surprised how inexpensive this bike was, but it is also cheap.  I call it my Cheap-O-Cycle.  At the time of this post I have accumulated 676 miles.  I would say about half the hours I have put on this bike have been off-road.  I did have trouble with the freewheeling hub.  It fell apart on one of the early rides. 

Kent sent me a set of replacement wheels (which included the freewheeling hub).  The new one did it as well and I learned how to tighten it.  It appears they do not seat the bearings or torque the unit properly when assembling it.  I tightened it very tight and the issue seems to have been corrected now.  I did buy a replacement on Amazon for $16 and that was much better.  Overall though I did get my $148 worth.  

Electric Fat-Tire Mountain Bike

Riding the Kent Flexor made me realize that I needed a fat tire bike for off-road.  The narrow tires on the Flexor would sink it too much.  A fat-tire full suspension bike takes more energy to ride.  I also found steep or long hills to be not fun on the Flexor.  When riding downhill on rough terrain, the Flexor did not feel substantial enough either.  It does not have actual shocks, just springs.  The brakes are just rim brakes and I wanted hydraulic disc.  These things led to to wanting to upgrade to an electric assisted mountain bike.  

I ended up with a Rurui XT10.  Since it has electric assist, I call it my Cheat-O-Cycle.  This bike has a much more substantial frame, full suspension with real shocks, hydraulic brakes, and 4" wide fat tires.  

My first ride on this bike was great. I was able to ride a trail that previously took about 2 hours in 20 minutes.  This particular ride has about 1000' elevation gain and is mostly loamy sand and gravel.  I made about a 14 mile loop which also included some paved bike path.  Most of that 14 miles was rugged off-road riding.  I was in PAS mode 1 for most of the ride.  PAS mode 1 provides electric assist up to about 10mph.  I took it on a paved bike path for a bit as well and tested the top speed in mode 5.  I was able to get over 27mph which is plenty fast for me on a bike. The maximum assist speed in user configurable through the display. In high gear the pedaling cadence is the limiting factor.

It took a bit to get used to how the electric drive worked.  This bike uses a rear hub-motor.  Some other electric bikes used a motor at the crank.  Each have pros and cons.  The hub motor is simple and does not impact the chain or gears.  However, it lacks the multiple gear ratios of the gears too.  This limits the speed range where it is most efficient.  I am happy with my choice of bike having a hub motor.  One upgrade I may consider it going with wider gear ratios, mostly for first gear.

I am happy with the battery range versus weight.  My first ride was not many miles for the effort as it was mostly off-road with many hills and loamy terrain.  Since these bikes don't have regenerative braking, that really consumes battery.  Garmin reported the ride at 13.9 miles and I used less than half the battery. This will really vary based on the specific ride and how much the rider puts into it.  I ride for enjoyment but a main goal is also exercise. I plan to always pedal. The first ride was much more intense than off-road rides on the Flexor since the speed was so much higher going up in elevation, and through loamy terrain.  

The hydraulic brakes and actual shocks were big upgrades from the Flexor.  One issue I did have is the pedals hit the ground when riding in ruts or when there are rocks.  I measured the distance from the bottom of the pedals to the ground on this and the Flexor and found the Flexor had at least 1" more ground clearance.  I may look into raising the back suspension on this bike a bit.  The fat tire made a huge difference off-road.  I was able to easily go through stuff I would have to get off and walk the Flexor through.  Same with hills.  The fat tires also soak up some of the bumpiness.  

I had dirt bikes back in the day.  My favorite was  KTM 500MX.  Riding the Rurui was somewhere between a mountain bike and a dirt bike, but more towards the mountain bike.  Obviously the 1HP this Rurui generates is tiny compared to my KTM that had 55HP.  Of course the KTM was also at least 100lbs heavier.  I was able to push the Rurui up super steep hills which was not really possible with dirt bikes.