Belly Laughs in the Mud on Onza Porcupine RC MTB Tires [Review]

Tiny porcupines wrap the casing to keep you upright, just like their quills.

Rated for the supportive and high-speed demands of downhill and enduro racing, or the added weight of e-bikes, the Onza Porcupine RC tire is your friend for sloppy riding and racing conditions.

Like trimmed quills, the widely-spaced spikes are shorter than you’ll find on some classic mud-spike treads, which cuts a little weight without losing your line. The Porcupine RC is only available in a single 29×2.5″ size, with a puncture-protecting gravity casing and tan sidewalls. Yup, just one model. The classic sidewall color is typically only available on lighter trail and XC tires, and Onza says that these roughly 1200g thumpers are the toughest gumwalls on the market.

29×2.5″ with tan sidewalls is the only option for Porcupine RC.

A single 120TPI casing layer is backed up by a second layer from bead to bead and extra nylon bead protection to give the Porcupine RC all the support and puncture resistance riders want in a gravity tire. The casings have yet to bleed a drop of sealant, despite being ridden hard on some of our rockiest local trails with two long-travel test rigs. Not only is the sealant level still topped off, but the tires hold air with the best of them. I’ve been able to run the same pressures that I would in any similar tire, and I have only had to add pressure once a week or so.

The nylon-fortified folding beads snapped into place with aplomb, leaving little to say about their tubeless performance other than installation was fast and simple. I mounted the tires front and rear, on rims with a 30mm internal measurement.

Mud spikes tall enough to cast a shadow.

As a lifelong mud lover, I was pumped when these tires showed up to test. We have some positively rocky descents nearby that are perfect when the weather isn’t, and the slimy dirt between those stones has been a solid proving ground for the Porcupine RC tread. Spacing between the mid-height lugs is massive, similar to that of a newly redesigned Maxxis Shorty in both shape and spacing. The massive amount of open air between lugs helps them shed mud quickly so they can be ready to collect and shed anew.

When it comes to fast and loose descents, this tread is one of the few that will hold on when it’s really a mess outside. I have found laughable amounts of traction on our local trails, only to look back and see my friends flailing on the ground for trying to keep up. If you like wet riding, and you want to do it relatively fast, this tire is a fantastic choice. It not only widens the fine line between grip and slip, but those sturdy hunks of rubber will slow the roll brilliantly when things get too spicy.

I’m not going to belabor the climbing characteristics of the Porcupine RC when two words do the job: tractor pull. These tires will not get you to the peak quickly, and they definitely require more watts to do it, but given their grip you will spend less time walking up slick trails and more time pedaling.

Which tires will grip wet roots? Well, none really, but these do a better job than some of the competition. If you’re riding with both brakes and eyeballs wide open they will roll right over the shiny tree-fingers most of the time, and quickly regain traction as soon as they find soil. Some tires sneeze and sniffle at the mere sight of wet roots, but these are not in that crappy camp. As for rain-soaked stones, I only tested them on trails with relatively grippy rocks, because I’d like my collar bones to stay in their current shape. The Porcupine RC shoulder lugs are well supported, both by their own rubber buttressing and the stout casing and they have managed to stay on the stones countless times when I expected a slide.

The shoulder lugs are both taller and softer than those in the center, helping them grip the earth on loose, off-camber trails, and none of the tread could be characterized as hard. Unlike some other mud spikes, I didn’t manage to rip any of the lugs asunder. Despite multiple stoney descents, each and every Porcupine quill remains present and accounted for. The center tread on the rear tire maintains about 70% of its original height, undeterred by my skidding over the rocks.

Notice how the outer edge of the shoulder knobs is below the base of the center knobs? The rounder profile better cuts into the soil.

Porcupine RC tires have a rounder profile than most of the gravity tires I have tested recently, which likely helps them bite down into the mud rather than floating on it. One way to judge the round vs. square profile of a tire is to look at the outer- and upper-most edge of the shoulder lugs. That’s usually the widest point of the tire. Where that edge sits in relation to the base of the center lug’s lowest outer edge can be a helpful way to eyeball the profile differences between two tires. I digress, the important point here is that these lugs are angled to get the grip on all sorts of loose terrain, even holding a line on some of the sloppiest off-camber tracks I have ridden this season.

Dual-ply casings often feel somewhat harsh on slower technical trails where impacts come with less force than the carcasses were designed for. They don’t deform around objects as well as lighter casings, which can be a benefit and a deficit. Harshness isn’t the adjective to use with this set. They perform well on slow choppy stuff and faster trails with repeated bumps and lumps. Onza seems to have dialed the tread and casing rebound properties to give them a comfortable manner on the roughest of tracks, without any sudden snapping or squirming.

I’m impressed that these tires remain intact and puncture-free after rattling down the rockiest trail I’ve found in Northern Italy multiple weekends in a row. They have plenty of life and latex left in them, and I will definitely save this set for next winter’s slippery silliness.

These tires are optimized for rims from 28 to 35mm wide.

These quills don’t lie. The Porcupine RC tires are well worth the €69.90 or $84.77 price tag for folks who genuinely love wet riding. Like the Maxxis Shorty, they should also work well in deep loam and heavy dust conditions, where digging to the bottom for grip is the only way to keep the bike upright and moving forward. You can pick up a set at Onza.com and Amazon.

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