Axial Capra

AXial Capra 2.2" Rock Crawler

Axial Capra set up as a 2.2" rock crawler.

It was time for an update to the 2.2” tire testing program, and after using our Axial Wraith Spawn for the last few 2.2” tire reviews, I wanted to retire that rock bouncer / crawler and use a more modern platform which was better suited for rock crawling.

Interestingly, there aren’t that many options to choose from; it seems rock crawlers running the 2.2” wheel is an underrepresented community. We skipped the Losi Night Crawler because we already have one in build as a Sporty ( details on that in a different review ).

Over the course of the search, it didn’t take long to narrow our focus down to the Axial Capra. I’ve seen more than a few Capras running a 2.2” wheel size and larger tires, and these were being used as dedicated crawlers and not just trail buggies ( Axial describes the Capra as a trail buggy ).

Their performance was respectable, and they seemed to be well regarded by their owners.

Another advantage for the Capra is the wide array of aftermarket upgrade options, and the open-wheel design will allow the use of taller 2.2” tires without clearance issues. I decided to take the Axial Capra 1.9” trail buggy kit and rework it into a 2.2” crawler. Action Hobbies in Boise, ID set us up with the kit.

Since the Capra is a well-known and popular platform, I’m not going to dive into the details about the OEM unit, but instead focus on the changes we’ve made and how our version is setup.

Another item worth noting is that we built two of the 2.2” Capra crawlers at the same time. The rationale is that we ( Kyle ) needed to do some computer modeling for the new front bulkhead and skid, and having two units to measure and test parts on was much easier than being confined to one unit for testing and reworking parts.

The side-hill performance from our Capra was impressive.

Test fitting the electronics early on. We reworked the battery location.

During the development process, Kyle made short work of the flat skid with improved link positions as well as the proper hole pattern to mount a Dlux Fab portal transmission.

The layout is a bit tight, and we had to use a short outrunner motor to clear the front link mounts.

We printed a few test pieces from PLA, then went with our uber-fancy 3D printer and made the final versions with carbon-fiber blended printer filament.

These proved to not only be light weight, but highly durable.

The front bulkhead took a bit of trial and error to establish the correct shock angle and ride height.

Same as before, the initial pieces were basic PLA with the final version from carbon fiber filament.
Finally, we sorted out a way to incorporate the battery mount as part of the servo mount plate, with a short extension off the back of the servo plate.

This system places the battery’s weight on the front axle and not sprung on the suspension. We then removed the OEM plastic battery mount from the chassis.

Again, space is limited, so this setup is designed for a small 450 mAh 3s battery, giving us about 30 to 45 minutes of crawl time per battery.

Under the hood showing the new bulkhead and battery mount off the servo.

Working a steep line with the JConcepts Rupture tires.

Purchased Parts

The Dlux transmission seemed to be the best option for quality and weight savings, and for shocks we stayed with Dlux and used their medium-length shocks for the build.
On the other Capra, Kyle went with a shorter shock and found it mounted better to the bulkhead in the front while maintaining the correct ride height.

For my medium Dlux shocks to fit, I ended up using a set of Hot Racing shock mounts, inverting and reversing the pieces to allow for the medium length front shocks to fit. Both Capra’s are running droop suspension setups, and I feel that Kyle’s setup is a little bit cleaner.

On the trail we didn’t notice any difference in crawling performance between the different shock lengths.

To establish a longer wheelbase at 13.25”, we went with In The Works custom high-clearance links.

The bottom links were made from titanium and the upper links from aluminum.

The rear links are 0.5” longer than stock and the front links are 0.25” longer than stock. The steering links are all titanium.

With the longer wheelbase, I had to mix and match a few spare Axial Wild Bore driveshaft lengths to accommodate for the longer space between axle and transmission outputs.

A few more grams were shaved off with aluminum screws in the cage and trimming away some excess plastic around the shocks, as well as skipping the use of the interior.

The cage itself was pruned down in a few areas to further reduce sprung weight.

For the axles, we added in a handful of Samix RC brass parts to place weight in the corners but opted to stay with the Axial plastic axle housings. SSD RC 25% overdrive portal gears were installed in the front axle portals. A Fishbone rear-link riser was used to help establish the correct anti-squat values.

This was a steep line for the Capra, but we were able to make it to the top.

On the Trail

Over the course of a dozen of trail-runs completed throughout the testing process, I was able to see the crawling performance of the Capra significantly improve.

The larger 2.2” tires coupled with the portals made for awesome ground clearance, while running a flat skid and full-droop suspension kept the crawler sitting relatively low in position.

As with most outrunner motors, the noise is somewhat annoying, but the light-weight Holmes Hobbies motor provided a reasonable amount of torque to keep the big tires turning.

Tuning the suspension took a bit of time, adjusting the shock fluid along with the correct spring weight on the inside of the shock to allow for some articulation but also prevent the nose of the Capra from tipping back on steep ascents.

As you can see in the photos, the Capra is in a continual state of evolution with changes to the cage, shock position, and suspension geometry.

During the initial testing out on the trail, we used random 2.2” tire sets we had on hand, looking to see if the Capra would react to different rubber compounds and lug patters.

Not coming as much of a surprise, the Capra quickly showed a distinct preference to softer and narrower tires.

We played with a few different sets of Crawler Innovations foams and found that soft outer foams all around worked best, as well as not over-stuffing the tire on foam size.

Traction on the side-hills was superb with a number of different tire setups, much of this due to the wide track width and relatively low center of gravity.

Kyle's black Capra following me up the trail.

Outstanding performance from our 2.2" Capra build.

Ready for Testing

With the last round of adjustments complete, Kyle and I hit the trail in Fruita, Colorado.

We had multiple sets of wheels and tires to try out, and overall, both Capra’s worked well with the JConcepts 2.2” Ruptures and the 2.2” Dlux Fab Goats.

The side-hill stability was quite impressive and the low-speed control on steep climbs exceeded our expectations.

After a few days on the trails in Fruita, and then a few more sessions in Idaho and back home here in Vegas, I feel the Capra is ready to take over the testing duties for 2.2” tire evaluation.

Nerdy Stuff

I’ve included the specs on CG and weight distribution of the Capra. The COG height line is right in line with the bottom of the skid plate. With the Insta-Center point just in front of the skid where the front lower links tie into the skid.

Crawler Specs

Weight: 2677 grams
- w/ aluminum beadlocks, CI foams, 450 mAh lipo 3s, Dlux Goat tires, wheel weights
Wheelbase: 13.25”
Track Width Centerline of Tire: 10.1”
Weight Distribution: 59/41

Build List

Axial Capra Builders Kit
Holmes Hobbies Revolver SS Team Spec 2250 kv
RAW 500 servo
Dlux Fab Medium Shocks
Samix Knuckle / Portal Weight Covers
SSD RC Overdrive Portal Gears 14/21 for 25% OD
In the Works Ti links – 13.25” wheelbase ( custom links )
Dlux Fab Portal Transmission
Castle RC Copperhead ESC
Prodigy RC Skid, Front Bulkhead, Battery Mount.
Fishbone Rear Link Riser

Prodigy RC Shapeways Link: https://www.shapeways.com/shops/prodigy-rc