eMTB Tire Review – DHR2/DHF vs Assegai vs Eddy Current vs Magic Mary

My 2020 Turbo Levo Comp has 390 miles on it, and am loving every minute of it. While not perfect in every way, everything that I have had an issue with I have been able to address. For example, the suspension was very bumpy, but I solved that by removing the tokens from the forks and rear shock that the factory opted to pre-install. The brake levers had way too much slack, but I fixed that by designing DeSlackinators. The 32-tooth chainring didn’t allow me to pedal much above 20 mph unless I was turning more than 100rpm, so I changed that to a 36 and later to a 38 – and then designed a chainguide adaptor to keep the factory look. Even the 38-tooth ring has been no problem for climbing the steepest of hills, making me wonder why it had a 32 to begin with.


During this time, I learned a lot about tires. I rode the original Specialized Butcher/Eliminator 2.6″ tires for 72 miles and knew that they had to go when they slipped on wet roots more than I think they should (based on my experience with my Nobby Nic Addix that I am mostly happy with on my manual bike). While I don’t ride on wet roots often, it is not the everyday case that I need extreme grip for. Rather it is more the occasional scary surface is what I want to be protected from because any tire does ok on normal surfaces. My rule for tires is to always get the best, but the hard part is finding out what is the best, and the best for one riding condition will not be the best for the other.

Some tires I was interested in were Maxxis DHR2/DHF, Assegai, Schwalbe Magic Mary and Eddy Current, and Michelin Wild Enduro. I started by getting the DHR2/DHF in 2.6″ width, 3C MaxxTerra, EXO+. I rode them 272 miles in dry and wet conditions, going for Strava eMTB KOMs in dry, and trying to hit every root in wet. I am 142lbs/64Kg and used them at about 18psi rear and 14 psi front, just like the stock Specialized tires. At this pressure, they were about 2.45 inches wide on the casings on my 30mm internal rims. I could tell right away that they were amazing, and I was not able to slip on the wet roots that caused me trouble before. I also did intentional panic stops on wet wooden bridges, also without any drama. Also, even though the knobs are not massive, I did not break traction climbing the steepest of hills, even when they were sometimes not the most firm dirt. Great all-around tires for sure.

Still, I could not leave well enough alone, and was dying to try the Eddy Current because they were said to being designed without regard for rolling resistance. That is bad right? Yes. But, I figured they used a really soft compound that would give them amazing traction in exchange for that added rolling resistance – and since it was an eMTB, I would only give up battery life and not really any speed. I got the 2.6 inch front and rear. They also measure about 2.45″ casing width at the same pressures. As of this writing, I have 46 miles on them, and I learned something interesting: The open block tread pattern feels weird on roots and solid rocks. You can sometimes feel the knobs snap off the root, and that is an unpleasant and sometimes scary feeling. And the same time, that large open tread has got to help on mud and sand – perhaps making them great winter tires. But for me, the wet root thing was still on my mind – I didn’t like these tires for where I rode, and decided to go back to Maxxis – but not before I tested rolling resistance.

There is a website https://www.bicyclerollingresistance.com which I love – but I asked the author if he could review more tires like the DHF and Eddy Current. He explained that people who buy aggressive treads just don’t care about rolling resistance so he was focusing on tires designed for efficiency. I took this to mean that people care about tire weight, but not the much more important rolling resistance – probably because it is hard to measure and quantify. So how could I find out which tires rolled the best? In general, when reviews say a tire “rolled well” or “did not roll well,” I don’t trust that they even can tell.

So I devised a test and rode a pre-planned trail-ride with the Maxxis and Eddy Current, both at 100% assist, and with me trying to end with the same segment time. I wanted to see how much battery the bike used up for each tire.



The test was successful. The DHR2/DHF won the rolling-resistance test. As far as I can tell, it rolls better, and there is certainly no evidence that it rolls worse! So, good job Maxxis with that tire that is also plenty grippy.

Now I wanted to test the Assegai, and went all out and got them in MaxxGrip with the DoubleDown casing. While the Assegai had an astonishing amount of grip on the forest floor, they were actually slipping on wet roots, even though they are MaxxGrip, so they were not infallible either. I also almost crashed when the front hit a minor patch of shallow mud – I bet the Eddy Current front would not have blinked at that. I am thinking I prefer the DHF MaxxTerra to the Assegai MaxxGrip, all things considered (price, weight, grip, rolling resistance).

So then I tried a Magic Mary 2.6 up front. To me, this was the best looking tire. I loved the snake-skin cross-pattern on the casing, and the sides of the knobs were nicely stylized. In general, this tire gripped equal to the DHF on most surfaces, but I think worse on wet roots. I say “think” because it is impossible to know for sure because each ride is a different path. The wet-root experience was more like my Assegai ride – and again, I am not sure why the Assegai slipped more than the DHF given it was a softer compound, so I do have doubt DHF is actually the best. Most likely, I perhaps just happened to hit the roots in a way that didn’t result in the tire slipping on my DHF ride.

Other factors to consider was that Maxxis installed really easily – I could probably do it without tools, which would be helpful for field repairs. The Eddy Current were the opposite – I broke a tire lever and needed to use a Pedros lever to install them – and even then, at great difficulty. This was a function of the super-tough sidewalls, so perhaps for the extra effort you get durability. I have seen people tear the Maxxis EXO+ sidewall on their Turbo Levo rims and don’t see any chance of that happening with the Eddy Current. In fact, I hit a hard object and my rim edge did put a hole in my DHR2 that I later patched from the inside. But, I did get better at installing the Eddy Current, and would not use this as a reason to avoid them. I would buy this tire again, at least for the rear – and for the front in loose or muddy conditions.

So what will I do going forward? I think the DHR2 or Eddy Current (rear or front) are great rear tires. For a front tire, I will stick to the DHF 3C MaxxTerra EXO+ after I use up the Assegai. I will skip the Assegai MaxxGrip DD due to the extra energy required and weight, as that makes my 700Wh battery behave as if it were a 630Wh. The Magic Mary was nice and I would be happy with that as well, but if I had nothing and was starting over, I would personally opt for the DHF/DHR2 combo again.











Making “nylon-like” Resin

Most resins are hard and can crack when dropped. There are some great “tough” resins such as Siraya Blu and eSun Tough, but what if one doesn’t want clear? I needed a white. I tried adding white opaque pigment to Siraya Blu, and it was promising, but the blue color was evident and it was just not white enough.

Elegoo white is often on sale for $38 per KG at Amazon with an extra 5% off if you buy several, but it is a normal modeling resin, which is designed to be hard and detailed – and my part was cracking the first drop at one meter onto a hard floor. I decided to see if adding in Siraya Tenacious would solve that.

https://youtu.be/WXHNfCgrlHg

Tenacious is a clear and flexible resin that when used by itself, can form flexible rubber-like parts such as watch bands or tank treads. When used for thicker parts, it behaves more like a urethane from skate-board wheels and feels solid. The nice thing about mixing in Tenacious is that the exposure happens to be the same as Elegoo White, so the same settings work for any ratio – though optimally another second or two is best, and base-time can be lowered.

I tested Elegoo white dropped from 1 meter, and it failed first drop. I then repeated with another sample, and that also failed on the first drop. With 33% Tenacious, 10 drops were not a problem. Now we are getting somewhere.

https://youtu.be/W4UEm3Tuo0s

The color does turn into a warm/yellowish white, but I am happy enough with the look, and recommend 33% Tenacious mixed with a hard resin for an affordable nylon-like blend. This is a simple 2:1 ratio, so easy to mix up with whole bottles.

Networking with the EPAX X1 LCD-SLA Printer

The EPAX X1 is capable of networking using hardwired ethernet. To set this up, first install the latest firmware from here:

https://epax3d.com/pages/firmware-and-parameter-files

To install, put both files onto a USB memory stick, insert the stick into the printer, and power on the printer. You will hear a series of beeps. Wait until they finish, and then check the version using the Info screen to make sure that it updated.

Now unscrew the four screws on the back side of the enclosure, and plug in an ethernet cable (the green cable in the photo). Plug the other end into your router or switch.

Using the front panel control, enter the network setup area:

Now toggle the network type. While WiFi is shown as an option, there is no WiFi hardware inside the printer, so you must use a cable. Push the switch in the upper left of the touch-screen to enable the ethernet connection. If you see an IP address fill in, it is working. A green LED should now be illuminated where the cable plugged in.

Now load the latest version of ChiTuBox, version 1.4.0 or newer, and slice a file. You will be presented with the option to save the sliced file, or send it to the network.

Select “Network Sending,” and you should see all of the EPAX printers that you have connected to your network. If this is your first time, you may need to select the refresh icon.

Note that you can click on the pencil icon and rename what each IP address is called.

Now press the send button. You should see it showing the progress where it says “Send file to the printer…”

When the sending is complete, it will ask if you would like to print the file. If you say OK, then it will start printing. If you hit Cancel, then the it won’t print, but the file will now be on the printer’s SD USB memory card for you to later start it manually from the printer’s touch screen.

If you would like to make the machine wireless using WiFi, you can probably make it work using a wireless bridge. Here are some untested referral-link examples:

https://tinyurl.com/yy3nnd4e

https://amzn.to/2Gt5H4E

I hope that helps get you up and running without resorting to the sneaker net.

On the difference between DLP and LCD based SLA printers

Laser, LCD, and DLP are three distinct methods of exposing a light-sensitive resin in layers to cause a cross-linking of liquid polymers, curing the liquid into a solid object. All of these are used within SLA printers, a term used to refer to the stereolithography process. There has been a disturbing trend to refer to LCD printers are “DLP” printer that started when lower price-point manufactures began to use the already-taken “DLP” term for marketing purposes and claiming it was ok because their LCD does light processing using digital signals. Doing so, however, is like calling a gasoline-engine car an electric vehicle – something that it is not – just to confuse consumers into thinking that they are getting something often seen as more desirable but at a lower price.

Laser, (originally L.A.S.E.R as an acronym for Light Amplification by Stimulated Emission of Radiation) uses galvanometer scanners to direct a light beam via vector and raster scanning. The process is fast for smaller object, but get progressively slower when it must draw out more objects. The advantage is a smooth surface finish and compatibility with resins high in polymer content for the strongest resulting parts. An example of desktop laser-based SLAs are the Peopoly Moai and the Formlabs Form-2 printer.

LCD is a variation of SLA that uses a Liquid Crystal Diode display, the same as in most laptops and mobile phones, as a mask. It is also known as MSLA, or masked SLA. A light source is placed on one side, and the resin on the other. Because the entire layer can be exposed at the same time, they are generally faster for printing more or larger objects. Example of LCD-based SLA printers are the Anycubic Photon, Wanhao Duplicator 7, and the EPAX-3D 1X. One reason why LCD still remains on the low end, because the fact that they can simply be manufactured for less cost, is that there is a limited amount of light that can pass through the LCD panel before it overheats and self-destructs. This limits the speed at which printing can take place. To help make up for this lower amount of light exposure, the resin makers increase the monomers and photo-sensitive initiators, with a resulting increase in potential for shrinkage and weaker parts. In reality though, due to advances in resin such as Siraya Labs Blu (the strongest LCD resin I have tested) and eSun Bioresin (the strongest solid-color LCD resin I have tested), some very strong parts can be made – just as strong, if not stronger, than PLA and ABS parts on FDM printers.

DLP uses a digital micro-mirror device in which light is reflected through a projector lens and onto a tank of resin. Because this matrix of mirrors can be well cooled, a lot more light can be directed than with LCD, thus making it the choice of larger, faster, and more expensive printers that can still make use of less sensitive and stronger resins normally reserved for laser. The downside being a higher price point, taller printer size, and sometimes lower resolution because DLP chips tend to max out at 1080P.

But you may ask – why is it not ok to refer to my LCD-based printer as “DLP” when the manufacturer says it has light processing and is digital? The answer is because the term DLP was already taken for a digital micro-mirror projector device, and there would be no distinction between the technologies, both of which are used in resin printers, if you used the same term for both.

Here is a video showing a DLP chip in action:



This is TI explaining their DLP reference design. Notice how it does not make use of an LCD:

Examples of some DLP printers are:

Chimera:

https://www.instructables.com/id/Chimera-60-DLP-resin-3d-printer/

Ember:

https://www.fabbaloo.com/blog/2014/12/28/see-autodesks-ember-3d-printer-in-action

Milkshake 3D:

https://www.milkshake3d.com

Carbon-3D

Moonray

G3D T-1000

https://www.g3dsys.com/product/t-1000-dlp-3d-printer/

FlashForge Hunter:



References:

See https://en.wikipedia.org/wiki/Digital_micromirror_device

https://en.wikipedia.org/wiki/Digital_Light_Processing