Astral Back Bone X Carbon Rim
The Astral Backbone Carbon X is the sharper, narrower sibling of the Backbone. Astral calls it a 27.5 trail-slayer, and that is a fair description: a 30mm internal carbon rim aimed at riders who want the stiffness and snap of carbon on a trail bike without going to a plus-width bed.
Thirty millimeters is the width most modern trail tires were designed around. A 2.4in tire on the Carbon X sits with a round, predictable profile that rolls fast on hardpack and still has enough sidewall support to lean hard. It is the rim we suggest when someone asks for one carbon 27.5 wheelset that does everything from long climbs to the occasional lift day.
As with every rim we sell, the Astral Back Bone X Carbon Rim comes from us only as a finished wheel: pick the hub, spokes and nipples, and we lace, tension and true it by hand in Georgia before it ships.
Design and construction
The Carbon X shares Astral's Tubeless Easy bead profile with the rest of the range, so tubeless setup is a floor-pump job. The layup is tuned for a trail rim rather than an XC one: there is extra material around the spoke bed and the bead hook area, which is where carbon rims take their abuse. Spoke holes are drilled at the angle the spokes actually leave the hub, so nipples seat straight and tension stays even.
Astral is part of Rolf Prima in Eugene, Oregon, and the company has been building wheels long enough to know that a stiff rim is only a good thing if the spokes can stay tight in it. The Carbon X has a deep enough section to keep spoke tension high and stable, which is why these wheels stay true.
How it rides
Carbon rims give a wheel two things alloy cannot at the same weight: lateral stiffness and damping. The Carbon X tracks straight through rough corners instead of squirming, and it takes some of the buzz out of chattery trail. Riders moving from an alloy 27.5 wheel usually describe the change as the bike feeling more direct.
If you ride mostly cross-country and want the lightest possible wheel, the Carbon X is still a good pick at 30mm. If you run 2.8 or 3.0in tires, step up to the standard Backbone with its 32mm bed.
Specifications
| Wheel size | 27.5in |
|---|---|
| ERD | 556 (27.5in) |
| Inner width | 30 mm |
| Depth | 25 mm |
| Drillings | 28h, 32h |
| Weight | 490g (650b/27.5in) |
| Material | Carbon Fiber |
| Tire type | Clincher Tubeless Compatible |
| Brake | Disc |
| Profile | Triangle |
| Nipples | External |
| Finishes | black |
About this listing
Version notes. 27.5in, 28h, 32h, about 490g, 30mm inside, 25mm deep, disc. The other sizes and brake versions of the Backbone X have their own listings; this page is for this one.
This is the disc-brake Backbone X: plain sidewalls, no brake track to wear, a touch lighter. It fits any disc-brake bike and it is the version most of our customers now build; the rim-brake version is a separate listing.
Sizes, fit and compatibility
27.5in (ISO 584) only, disc brake only, in the drillings listed on this page. Tires from about 2.2 to 2.6in suit the 30mm bed best. Tubeless-ready; we tape and fit a valve when you choose tubeless in the build.
Pair it with a Boost hub of your choice. We build a lot of these on Industry Nine Hydra and 1/1 hubs, DT Swiss 350 and 240, Hope Pro 5 and Onyx Vesper, with Sapim or DT double-butted spokes.
Build a wheel around it
Offered for tandem and e-bike, mountain bike, MTB single-speed and fat bike builds in our Custom Wheel Program. Start with the Astral Back Bone X Carbon Rim and the configurator pins it for you, then checks each choice you make against it.
Spoke head is decided by the hub, not the rim: this rim builds equally well with J-bend or straight-pull spokes, and the configurator only offers the spokes that match the hub you pick.
Testing, standards and warranty at Astral
Astral Cycling is the rim brand of Rolf Prima; both operate from one facility in Eugene, Oregon, where Rolf Prima states alloy rim production has been in-house since 2014. Astral joins alloy rims with a press-fit sleeve about 2.5 inches long weighing 4-5 g that doubles the wall thickness at the joint, avoiding the heat-affected zone of welding. All wheels are hand-built in Eugene. Rolf Prima states it does not farm out testing and has logged "over 10,000 hours of lab testing to above industry standards."
Warranty: Astral states alloy rims are covered two years and carbon rims five years for the original owner, excluding impact damage; Rolf Prima wheels (2016 and newer) carry five years, bearings two years, plus lifetime discounted crash replacement for registered wheels.
Astral's videos
From Astral
Certifications
- Made in USA (alloy rims and wheels) — Astral and Rolf Prima state alloy rims are rolled and all wheels hand-built in their Eugene, Oregon facility; rim production in-house since 2014 (source)
- ISO 4210 base + in-house standard — Fatigue drum at 47 mph vs ISO 15 mph, life requirement 66% above ISO; UCI 40 J impact plus higher in-house level; ISO 4210 dry/wet brake tests (source)
- UCI note — Rolf Prima FAQ: Aspin and Elan family are 'Standard' wheels not requiring UCI approval; no approved-model list verified (source)
- Rolf Prima Certainty — In-house engineering and testing lab, eleven patents, over 10,000 hours of lab testing, 5-year warranty, lifetime crash replacement (source)
Sources on Astral's site:
- Testing – Astral Cycling
- FAQ's – Astral Cycling
- Astral Rim Warranty – Astral Cycling
- Technology – Astral Cycling
- Rim Joining: The Process and the Mystery – Astral Cycling
The figures, certificates and media above are Astral's own. ProWheelBuilder does not run these tests; our part is the wheel we build on the rim.
Building it at ProWheelBuilder
Astral makes the rim; ProWheelBuilder builds the wheel. We are an independent custom wheel builder in Georgia, not the manufacturer, and we build every Carbon X to the rider rather than to a template. That means measuring the ERD of the actual rim, cutting spokes to length, tensioning in stages with a tensiometer and stress-relieving before final truing.
In the configurator you will only see hubs, spokes and lacing patterns that can be built with the drilling you pick. The price updates live, and the estimated ship date is shown before you check out.
Warranty
Manufacturer's warranty. Rolf Prima gives a one-year limited warranty on its wheels under normal use. Astral is Rolf Prima's rim brand; ask us and we will confirm the current terms for the exact rim before you buy.
ProWheelBuilder. Lace this into a wheel here and the finished wheel gets our own one-year warranty as well as the maker's. For twelve months we replace broken spokes however they broke, and the work on the wheel is on us - truing, re-tensioning, a rebuild where it is needed. If the rim or hub is covered by its manufacturer we put the claim in and chase it; if it is not, we supply an eligible replacement rim or hub at 25% off the current retail price. Carriage both ways is the customer's, and this does not cover wheels built from parts you send in.
Full terms are on our Policies & Warranty page.
Back Bone X Carbon Rim questions
What tire width suits this rim?
At 30mm inside this is a trail width, sized around 2.1 to 2.4in tires. That is wide enough to stop a modern trail casing rolling under you in a corner without pushing the tread so flat that it wears down the middle.
What is the difference between the Backbone and the Backbone Carbon X?
Width and material. The Backbone is a 30mm inner-width rim in alloy (28mm in carbon) for wide trail and plus tires; the Carbon X is a 30mm carbon rim for standard trail tires and a lighter, stiffer wheel.
Does carbon mean I need special spokes?
No. The Carbon X takes standard J-bend spokes and external nipples. We use brass nipples by default for carbon rims because they are kinder to the rim bed over years of truing.
What rider weight is it good for?
Astral builds the Carbon X as a trail rim rather than a lightweight XC part, so it suits most riders. Give the configurator your weight and it will set spoke count and gauge accordingly.
Is it hookless?
Astral's Tubeless Easy bead is a tubeless-specific shelf design. Use tubeless-ready tires and follow the pressure limits printed on the tire and rim.
Is it tubeless-ready?
Yes. Astral lists the Back Bone X Carbon Rim as clincher tubeless compatible; we tape and fit a valve when you choose the tubeless option.
Which spoke count should I choose?
It depends on your weight, terrain and the hub, not the rim alone. The configurator recommends a count from your bike type and rider weight, within the drillings this rim is made in.
Not sure? Text or leave a voicemail on 470-253-0929 or email info@prowheelbuilder.com — you will be talking to the people who build the wheels.
