NMRCC 1.9 Trail Class Build

[Chingon]

I had been competing in the NMRCC 1.9 and 2.2 Trail Classes with my AX10 build for a couple of years, and after slowly upgrading my AX10 piece by piece (not much AX10 left at this point) I had started thinking about building a second rig with the spare parts so I could have a dedicated 1.9 and 2.2 rigs to compete with. What really got this build kicked off was an all-metal Hot Racing Wraith transmission I got for free off one of the other NMRCC members but ultimately ended up not using. I had a spare XR mod AX10 axle, but after looking at options for another axle to pair with it, I ended up just buying a set of SCX10 Pro portal axles (AXI338001) which wasn't really much more expensive than piecing together a Capra axle, and I figured the width suited a dedicated 1.9 build better. I used the G-Speed V4 chassis I won at the 2023 NMRCC state championship, my old AX10 shocks with Axcess springs, my old aluminum AX10 lower links, my 1.9" Ruptures with Crawler Innovations dual stage foams mounted on AMK competition wheels, my Hobby Wing 1080 ESC, my Team Brood 5 slot 11T motor, and my old Injora/SPT low-profile 35KG servo. I had planned on running an old HPI early Bronco Body I had, but I decided against it since it was so big and bulky and ended up using a Proline Coyote Grande Body since it was competition friendly and clearly resembles a Bronco II (albeit with 4 doors).

I apparently sucked at getting pictures of the build, but I put some Vanquish 33/8T underdrive gears (VPS08331) in the rear along with a "Chilux" OD-3 transmission which has 18% rear underdrive underdrive for a total of 29.8% overdrive to the front. I am running a Robinson Racing 17T pinion (RRP1417) for a 68:1 final drive at the front axle (88.5 at the rear). I am also using the Dlux Fab brass axial portal knuckles along with their super heavy brass portal covers in the front. In the rear I am running the Injora light brass portal covers. I printed a tray that attaches to the axle servo mount to mount my ESC and receiver (FlySky BS-6) to the front axle.

XR10 Mod AX10 rear axle width compared to the SCX10 Pro portal rear.

Chinese Dlux OD-3 knock off. Excellent quality for less than 1/3 the cost of the Dlux unit.

About 100g lighter than the aluminum Hot Racing Wraith transmission that I started the build with.

Stock rear SCX10 Pro portal weight.

Added some Injora light brass portal covers and Vanquish 4.125 underdrive gears.

Weight reassembled.

Stock front SCX10 Pro portal weight.

Front axle weight with the Dlux knuckles and portal covers.

 

[Chingon]

I recycled the Hobbywing 1080 G1 I was previously using in my AX10 build. I went with XT60 connectors for the battery plug as well as the motor plug. Old picture from when I first got it.

The Team Brood 5 slot 11T motor I am running (also recycled from the AX10 build).

I am running the OG AX10 shocks with some Acxess springs I picked out from their catalog (PC032-625-10.000-SST-3.407-CG-N-IN) and some lower spring seats I printed that give slightly more compression travel than the stock spring seats and keep the new springs preloaded and from coming unseated as easily.

Acxess springs compared to the Axial "Red" AX10 springs.

Ignore the Traxxas shocks, those are what replaced the AX10 shocks on the other build.

The AMK competition wheels I bought off Amazon. They have about as much clearance as you can get with a 1.9" wheel and seem like pretty nice quality for the price.

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The foam setup I am running with the 1.9 JConcepts Ruptures. Obviously softs up front and mediums in the rear. I think I would like to try some hard outer tuning rings since I think I am getting too much lug folding, but the lateral stability has been pretty good.

Here's the specs of the "Injora" servo I recycled from my spare parts since I was trying to save a little money when I started the build. It was actually a great, cheap low profile servo performance-wise. I replaced it on my AX10 build because it was getting some bad servo shakes and would act up when it got hot, but it had plenty of power running off the HW 1080 G1 ESC without a BEC and was super fast. In hindsight, I shouldn't have recycled it since it really screwed me at this rigs debut at the 2024 New Mexico State Championship when the servo shakes got so bad, the rig was practically undrivable.

Ignore the other parts in this picture, here is the Protek 3S 1400 mah batteries I am running in this build.

Ignore the tires, these are the G Speed V4 carbon rails I am running that I won at the 2023 New Mexico state championship.

 

[Chingon]

I designed and printed my belly skid, boat sides, body mounts, Rear upper links, Rear link riser, and my ESC/Receiver tray that bolts to the stock SCX10 Pro BTA servo mount. I designed the rear body mount as a hinge (inspired by my SCX24) so I only have to pull two pins to lift the body off.

Mocking the body up. I cut a bit off the front of the G Speed frame rails to get them to fit behind the grill.

Painted with some automotive interior paint from Seymour and stickered up. I wanted the paint color to match my real Bronco II, but it ended up being a bit lighter than I was hoping.

All put together and ready to rock.

The wheelbase came out right at 13" which is a bit longer than I was originally planning on, but seems to be working pretty well. Total weight ended up at 5.64Lbs with a 57% forward weight bias, which is a little heavier and a little less forward bias than I was hoping for, but not bad.

 

[Chingon]

It ended up doing well at its debut competition other than the old Injora servo that shook worse than Michael J Fox. I knew I should have bought a new NSDRC RS700V2 direct power servo before the comp, but I didn't want to spend another $125 on what was originally supposed to be a spare parts build. Other than that, I am pretty happy with the way it performed. The drivetrain is excellent and feels pretty peppy despite the gearing with my old Protek 1400mah 3S batteries. It is a bit more top heavy than I was expecting with all the weight in the axles, but I did intentionally build it with some more belly height over my AX10 since that build might be a little too low.

I feel like I performed about as well as I could have in the 1.9 class at the NMRCC state championship with no major mistakes. I ended up in 7th place which I am happy with for an untested build without any seat time before the competition against some great drivers.

 

[Chingon]

I went ahead and picked up an NSDRC RS700 V2 direct power servo from Hittman Fab after the competition. I had to swap my servo horn out since the output is more compact than the SPT servo that I was running before. I just picked up one of the cheapo Amazon special 24mm clamping aluminum units and it works perfectly. I took it out again to experience the truck for the first time without servo shakes and it did great! I enjoy driving it more than my AX10/2.2 build. About the only change I have in mind at this point is converting to an AM32 ESC and compact outrunner motor along with going to 4S to cut 80-100g and get a battery I can mount on the front axle. Hopefully that gets the COG down low enough it is just as stable as my AX10 despite the narrower width and shorter wheelbase. Pulled off some stupid lines I didn't think it would.

Some pictures:

A shitty video I took running this line a second time after it surprised me and made it the first time. It is hard to film and try to drive one handed, and of course the video does it no justice.

 

[Chingon]

NMRCC hosted the Seasoner opener barbecue on February 8th. It was just 1 course for each class they run, but I ended up getting 2nd. No pictures of my rig, but here's a cool shot one of the other members got of my judging.

 

[Saltrock]

Nice looking truck and congratz on the second place.
You mentioned underdriving the rear axle and putting in a gear reduction in the transmission and calling it an overdrive in the front. To overdrive the front axle you need to put new gears in it to make it faster. If you only mess with the rear axle and the transmission it is a gear reduction in the trans and an underdrive in the rear and the front stays the front. Have a good day.

 

[Chingon]

NMRCC held their first 2025 Trail class competition on February 23rd which had a great turnout. I started on course 2 and had the 3rd best score, but my day went downhill from there. I had a perfect run going on the third course, but snapped a rear link rod end after taking a hard drop through the second bonus gate. I tried to keep driving the course with the rear axle flopping around, but I couldn't get through gate 5 and chose to end my run and go fix it. I went back after the 1.9 competition was over and was able to run the rest of the course clean after fixing my truck, so that was a disappointing break. On course 1 I was being stupid and made several mistakes and ended up DNFing on gate 10 instead of being smart and just taking a gate.

NMRCC Comp #1 Trailclass Scores
1.9 Trailclass
1. Christian -39, -49, -49 = -137
2. Garret -49, -39, -39 = -127
3. Chris B. -17, -31, -49 = -97
4. Thomas -29, -29, -24 = -82
5. Zak -17, -2, -35 = -54
6. Kevin +22, -15, -34 = -27
7. Phillip +22, -18, -21 = -17
8. Stephen -17, -17, +24 = -10
9. Mike H. -4, -29, +26 = -7
10. Brian -17, -16, +28 = -5
11. Orlando -10, -16, +26 = 0
12. Jose -16, +2, +26 = +12
13. Jesse -7, -7, +26 = +12
14. ME +22, -38, +32 = +16
15. Anthony +11, -16, +30 = +25
16. William +28, -28, +28 = +28
17. Rona +2, +26, +28 = +56
18. Raul +34, +22, +30 = +66
19. Sunshine +22, +26, +36 = +84
20. Rich +28, +26, +36 = +90

No pictures of me running, but a few of me judging. Here are some pictures from the event.

The bonus drop that ended up breaking my rig. The picture doesn't do it any justice.

A picture of the 1.9 rig parked with me getting some practice in with the 2.2 in the background.

 

[Chingon]

Nice looking truck and congratz on the second place.
You mentioned underdriving the rear axle and putting in a gear reduction in the transmission and calling it an overdrive in the front. To overdrive the front axle you need to put new gears in it to make it faster. If you only mess with the rear axle and the transmission it is a gear reduction in the trans and an underdrive in the rear and the front stays the front. Have a good day.

It is a Dlux OD-3 clone which is an 18% underdrive to the rear axle which combined with the 4.125 rear gears (3.75 in the front axle) works out to 29.8% overdrive in the front relative to the rear axle.

 

[Saltrock]

Underdrive in the rear axle doesn’t work out to overdrive in the front.

 

[Chingon]

Underdrive in the rear axle doesn’t work out to overdrive in the front.

It's the same thing. The front axle is spinning 30% faster than the rear. I posted the final drive ratios for both the front and rear, so I am not sure what you're hung up on.

Anyway, here's a few pictures from the last time I had it out at a spot close to the house.

 

[Chingon]

NMRCC got a new president and VP this season, so they made some rule changes to the trail classes for the first time in a long time. They decided to ban the Ruptures I am running on both rigs which pissed me off a bit, but oh well.

Here are the NMRCC Trail Class Rules for anyone interested:

2025/2026 Trail Class Rules
They do apply for both classes (1.9 and 2.2) unless specified:
Any rule with asterisks is new
Chassis:
- Chassis rail length must be as long as the wheelbase (adding parts to the chassis to make it longer isn't allowed)**
- Chassis can be any regular rail (metal or carbon fiber), stock rail, stock tube, custom tube, and TVP (twin vertical plate).
Vehicle weight/ Added weight:
- Knuckle weights ARE allowed. Weighted wheels are allowed.
Body:
- Bug bodies ARE allowed
- Bodies must be scale in appearance.
- Tube frame chassis must have a minimum of at least a roof, hood, and sidepanels.
- Hardbodies are allowed.
- NO competition style bodies such as Lattice Innovation bodies, or 1/16 and smaller bodies
Tires:
- Scale tires only.
- NO competition or pin tires allowed.
- Tires can be siped, grooved and trimmed.
- Cut and shut tires are allowed, but as for the 1.9 class, only narrowing is allowed (no sidewall modifications)**
--BANNED TIRE LIST--
ALL Pin style tires are not allowed (For example: Reefs RC Cheater tires or Ibex)**
Sedonas
Rovers
Dlux Goats**
JConcepts Ruptures**
Extreme Route Lampreys**
Losi boss claws
Chisels
Panthers (all types)
Wheels:
- Wheels must be either 2.2" or 1.9", no other sizes. They will be ran with the corresponding tire, and ran in the corresponding class.
Electronics:
- One motor limit
- No 4WS or Dig is allowed.



I should have probably bought some 4.75" JConcepts tires, but I like the height of the Ruptures, so I ended up going with the Proline Trepadors and some new foams from Crawler innovations with the ultra dense black foam inners. I bought another set of the same wheels so I could keep my Ruptures ready to go still.

From my experience with the heavy weight inner foams on my 2.2, I learned that it doesn't vent well and if you wad a tire up, it takes it a while to get its shape back. I decided to drill some holes in the inner foam with a #18 drill bit to eliminate that issue.

After assembling the new combo, I am concerned how much harder it is than the Rupture setup. I need to get out and start breaking the new tire in, so I'll find out soon enough.

 

[Saltrock]

It’s not the same thing, if you don’t change the front axle then it isn’t overdriven. The front axle is just “driven” the rear is underdriven.

 

[Chingon]

It’s not the same thing, if you don’t change the front axle then it isn’t overdriven. The front axle is just “driven” the rear is underdriven.

You're literally having the glass half empty or half full argument with me right now.

 

[Chingon]

I took it out today with the Trepadors and burned a pack to try and start getting them broken in and get a feel for them. I have some mixed feelings about the new tire and foam setup. The sidewall grip seems to be better, and some things it seemed to do worse and some things seemed to be better. It seemed to be a lot worse on slab climbs than the Rupture setup.

I got straight denied on two climbs, although one might have been because the rear tires were packing with mud since it just snowed yesterday. Another one that I have spent tons of time trying to get in the past, it more or less walked up today.

Anyway a few pictures.

 

[Chingon]

I had another competition on March 23rd. It was a good turnout and fun courses. The rig did well except it did not want to climb the first gate on course 2 which was a very similar line that I had done recreationally multiple times in the past on my Ruptures. I wasted all my time trying to get through and had to rush through the rest of the course and skip all of the bonuses. I could have made two of the bonuses no problem and in my rush to finish the course, I ended up with a stupid rollover since I was trying to drive while I couldn't see my truck. That one course pretty much tanked my finishing position and I did well on the other courses aside from being dumb and tagging a completely avoidable gate on course 3 (Course 1 only had 2 bonuses since the course setter forgot the third bonus). I ended up with 11th out of 14. Overall, I think the tire/foam change is a wash, but the Trepadors definitely seem to do a little worse on smoothish slab climbs.

 

[Chingon]

I was originally planning on the Rhino S12 motor and 40A ESC Combo I run in my 2.2 Trail Class rig, and in fact had already purchased the combo for this truck. However, I was intrigued by the new Hobbywing Fusion Mini16 that is intended for 1/18 and 1/16 scale trucks, but Hobbywing sells a 540 pattern adapter and advertises it as compatible with lightweight 1/10 scale trucks too. The Mini 16 is rated at 30A, which should be sufficient for a crawler. The parts I used to make it work were a Traxxas Latrax 14 T pinion (7592) I had to drill out with a #43 drill (I was dumb, there are plenty of 2.3mm pinions available), a Chinese motor adapter off AliExpress ($2.50 vs $10 HW wants), and I swapped to an XT60 connector and added a JST connector to work with my direct power servo. If I were starting from scratch, I would go with an XT30, but my batteries are all XT60s and I already had a bunch of female XT60 connectors.

XT60 connectors are suprisingly heavy compared to XT30 connectors in addition to the added bulk:

The weight of the Team Brood Ravage 5 slot 11T motor, HW1080 G1, and BS6 receiver the new combo is replacing:

The weight of the new Fusion Mini16 and FS2A receiver (pre-assembly):

A 171g weight savings!

After a quick run in the living room, the pinion worked itself off the motor, so I re-cleaned everything and filled the pinion with threadlocker in an attempt to keep it from rocking on the motor shaft and working itself loose again. I can easily mill .150" off the motor mounting face of the OD-3 trans which i will probably end up doing to get the pinion slid down for full engagement with the motor shaft. I am a little concerned about putting it into a real bind right now since to get the pinion to mesh with the knock-off Chilux OD-3 transmission I am running, I literally had to put the pinion set screw at the very end of the motor shaft. The 2.3mm motor shaft isn't particularly confidence inspiring and I am worried about the pinion spreading away from the spur inside the trans and skipping/stripping teeth.

Based on Holmes motor speed chart I figured my Team Brood Ravage (machine wound) 5 slot 11T motor was equivalent to ~2500kV and since I was running a 17T pinion, I needed to go with a 14T pinion with the Fusion Mini16 (3000kV) to end up with the same wheels speed. My crawl ratio with the 14T pinion is at 82.8:1 in the front and 108.1:1 in the rear. This video is on 3S and I lost a bit of wheel speed. I think I will try out a 15T or 16T pinion. The low speed creep is definitely better than the old setup, I am just not sure how well it will do when I get it really bound up.

 

[Col_Sanders]

Interesting rule set. Kind of odd that they split by wheel size instead of tire size.

Trepadors are definitely a downgrade in performance compared to Ruptures. Softer inserts would probably help a bit, but even then, I dont know how they would stack up to some of the other tires out there like Tusks. Not sure the added ~0.15" in height is worth having less traction on a comp rig. I run them on my Optic but I'm not AS concerned with performance on that.

It’s not the same thing, if you don’t change the front axle then it isn’t overdriven. The front axle is just “driven” the rear is underdriven.

If you want to get all technical on something that really doesnt matter...the transmission is called OD-3...as in overdrive. Go ahead and take that argument to DLux and Vanquish if you think you can't overdrive a transmission.

 

[Chingon]

Interesting rule set. Kind of odd that they split by wheel size instead of tire size.

Trepadors are definitely a downgrade in performance compared to Ruptures. Softer inserts would probably help a bit, but even then, I dont know how they would stack up to some of the other tires out there like Tusks. Not sure the added ~0.15" in height is worth having less traction on a comp rig. I run them on my Optic but I'm not AS concerned with performance on that.


If you want to get all technical on something that really doesnt matter...the transmission is called OD-3...as in overdrive. Go ahead and take that argument to DLux and Vanquish if you think you can't overdrive a transmission.

I don't hate the Trepadors, and aside from slab climbs I feel like the change is kind of a wash, but part of that is likely because I think the foams I am running in the Ruptures are a little too soft and let the lugs fold too much. It would be interesting to take both sets of tires out and try the same lines with them to get more of an A-B comparison. I think my foam setup in the Trepadors is pretty ideal having run it for a bit now and the Trepadors are just barely starting to break in and round the edges off the lugs. Proline really needs to make them in a Predator compound because the G8 compound is noticeably harder than JConcepts Green which you can break in with one battery pack.

 

[Col_Sanders]

I am running V2 3 Brothers Antifoams in mine. I definitely would not say they suck but I think my Tusks do a bit better. They are not fully broken in yet though. I like JConcepts Green compound. I think Predator can be too soft in some instances and G8 can be too hard. Predator would probably be really good on the Trepadors though.