Astral Viper Aluminum Rim
The Astral Viper is the alloy mountain rim from Astral, the rim brand of Rolf Prima in Eugene, Oregon: a modern inner width for 2.2 to 2.5in cross-country and trail tires, Astral's Tubeless Easy bead that seats a tire with a floor pump, and the slightly over-built construction Astral rims are known for, in 29in and 27.5in. It is the alloy rim we build for cross-country and trail bikes that want a tough, tubeless wheel from a company that builds wheels for a living; the Backbone is Astral's wider trail rim.
This page covers the Astral Viper Aluminum Rim in 29in, 27.5in. The Viper is not sold bare. You choose the hub and the rest of the build in the configurator, and it ships from our shop in Georgia laced, tensioned and trued by hand.
Design and construction
The Viper is a welded double-wall aluminum rim with a 27mm-class inner bed that gives a 2.35in tire a round, fast profile and a 2.5in tire enough support to corner hard, a Tubeless Easy bead shelf that seats and holds a tubeless tire at trail pressures, and spoke holes angled toward the hub flanges so the wheel builds to even tension. The walls are thick where rock strikes land. Standard nipples, J-bend spokes, disc only.
How it rides
A Viper wheel is quick and stable. The bed keeps a 2.35in tire fast on hardpack, the Tubeless Easy bead never burps at low pressure, and the welded rim takes trail abuse without complaint. For wide tires and hard trail riding the Backbone is wider; for cross-country and trail on 2.2 to 2.5in tires, the Viper is the Astral alloy rim we recommend.
Specifications
| Wheel size | 29in, 27.5in |
|---|---|
| ERD | 537 (29in), 537 (27.5in) |
| Inner width | 18 mm |
| Depth | 19.5 mm |
| Drillings | 28h, 32h |
| Weight | 415g (700c/29in), 390g (650b/27.5in) |
| Material | Aluminum |
| Tire type | Clincher Tubeless Compatible |
| Brake | Disc |
| Profile | Triangle |
| Nipples | External |
| Finishes | black |
This listing
This is the 29in, 27.5in listing of the Viper, 28h, 32h, about 415g, 18mm inside, 19.5mm deep, disc. Pick the size that matches your frame; the profile and construction are the same across the range.
The disc version of the Viper has no brake track, so the sidewall is a plain extrusion that saves a little weight and never wears; it is the one to choose for any disc-brake frame. The rim-brake version, listed separately, has a machined sidewall.
Sizes, fit and compatibility
The Astral Viper Aluminum Rim comes in 29in, 27.5in and 28h, 32h drilling. It is a disc-brake rim. We build the Viper on DT Swiss 350 and 240, Industry Nine 1/1 and Hydra 2, Hope Pro 5, Onyx Vesper and Bitex BX 211 hubs, usually with Sapim Race, D-Light or DT Competition spokes and brass nipples.
Tire range on the Viper is 2.2 to 2.5in. Give the configurator your bike type and weight; it picks a sensible spoke count and lacing pattern, which you can override.
Build a wheel around it
Offered for gravel and road disc, track and road single-speed, touring, mountain bike and MTB single-speed builds in our Custom Wheel Program. Start with the Astral Viper Aluminum 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.
What Astral says about testing
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."
Astral and Rolf state they use ISO 4210 "as a base starting point but it is not tough enough." Their drum fatigue tester runs at 47 mph against the ISO 15 mph, putting over 3 times the energy into the wheel, with a life requirement 66% higher than ISO. Impact tests use a calibrated steel anvil to the UCI 40 J standard and then a higher in-house level, at spokes, between spokes and at the valve hole, including pre-heated rims. Rolf's carbon brake protocol runs ISO 4210 dry and wet tests, 300 W for 15 minutes twice, 400 W for 16 minutes twice, 450 W and 500 W for 16 minutes, and 500 W for 3 minutes followed by the UCI impact test with no failure allowed. No rider weight limit is stated.
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
Everything in this section is published by Astral. ProWheelBuilder is the wheel builder, not the tester, and the rim reaches us as the maker ships it.
Building it at ProWheelBuilder
Astral makes the Viper; ProWheelBuilder is an independent wheel builder in Georgia, not the manufacturer. Every Viper wheel we build gets spokes cut from the rim's measured ERD, is tensioned in stages with a gauge, stress-relieved and trued before it ships. Tubeless tape and a valve are fitted on request.
In the configurator you will only see parts that fit this drilling; combinations that are not made are struck through, and the price updates as you pick.
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. Any wheel we build on this part carries ProWheelBuilder's one-year warranty in addition to the manufacturer's. Broken spokes are replaced for a year whatever the cause, and all wheel-side labor is included - truing, re-tensioning, rebuilding. Where the maker covers a failed rim or hub we handle that claim for you; where they decline, an eligible replacement comes at 25% off current retail. The customer covers shipping in both directions. Components supplied by the customer are not covered.
Full terms are on our Policies & Warranty page.
Viper Aluminum Rim questions
What tire width suits this rim?
At 18mm inside this is a road width. It suits roughly 25 to 32mm tires, which is where most road bikes now sit, and it will run a 23 if you still want one. Go much wider than 32 on this rim and the tire starts to balloon above the sidewalls and squirm when you lean on it.
Viper or Backbone?
Viper for cross-country and trail on 2.2 to 2.5in tires; Backbone for wide trail and plus tires with its 32mm bed.
Is the Viper tubeless?
Yes. Astral's Tubeless Easy bead seats a tubeless tire with a floor pump; we tape and fit a valve on request.
What tires fit the Viper?
2.2 to 2.5in. A 2.35in tire is the pairing most of our customers run.
Who is Astral?
The rim brand of Rolf Prima, the wheel company in Eugene, Oregon.
Is it tubeless-ready?
Yes. Astral lists the Viper Aluminum 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.
