Schwalbe Procore

For some years now it’s been recognised that lower tyre pressures increase traction. On rougher terrain, softer tyres can actually decrease your rolling resistance too. As a result, most astute mountain bikers have been trying to put as little air in their tyres as possible.

There are, however, a couple of limiting factors. Too little pressure will leave you prone to denting your rims, pinch flatting tyres and burping air. Wide tyres and very wide rims help, as they increase the overall air volume and provide more ‘cushion’. Heavy sidewalls and better tyre beads also assist but Teutonic tyre tycoons at Schwalbe believe they’ve come up with a better idea.

Their Procore system is essentially a type of tyre-in-tyre; the narrow inner tyre uses a tube and very high pressure to prevent the tyre bottoming on the rim, whilst the outer tyre is set up tubeless and according to Schwalbe is intended to be run at pressures as low as 12psi. They claim this combination gives the traction of super low pressures but without any chance of pinch flats, rim strikes or burped tyres—it’s said to be a game changer.

In the 27.5 size option, the entire system weighs around 440g (for two wheels) and it will lighten your wallet by $360. Procore installation is a little more complex than either a standard tubed or tubeless setup. It isn’t difficult as long as you follow the instructions carefully, but it’s comparatively fiddly and takes longer; not the setup I’d recommend for frequent tyre changers.
It employs a very clever valve that lets you select which part of the Procore system you want to inflate. As a result, it will work with any standard rim that has an inner width of 23-40mm. During the test period I fitted it to two different wheelsets; one with an inner width of 35mm and the other measuring 23mm internally.

Installation on the wide rim was actually very easy, however the narrow rim was far more challenging; there simply isn’t a lot of space for a rim strip, a tube and four tyre beads. For the first time in several years I was forced to use tyre levers! Once mounted, the inner tyre absolutely locks the outer beads in place—it's not going anywhere! Time to get riding…

Baseline Stats
In order to know if the game has changed, you first need to know what the current game is. I’m a moderately aggressive 70kg trail rider happy to do mid-sized jumps and drops. My trails are fairly rocky and I usually run tubeless 35mm wide carbon rims. I use 2.35-inch wide trail tyres that are typically in the 800g range with reinforced sidewalls. With this setup, I’m able to run 18psi up front and 22psi in the rear. While it’s not uncommon to hear my tyre bottom out on the rim, I haven’t burped a tyre or damaged a rim in several years, nor had a tyre pinch flat badly enough that the sealant couldn’t fix it.

In all honesty, I have to say that riding with Procore didn’t prove revolutionary for me. Thanks to my wide rims, I’m already able to run relatively low tyre pressures and I don’t have any issues with rim damage or tyre security. In this regard, Procore is trying to solve a bunch of problems that I simply don’t have.

I also tried running pressures as low as 12/16psi—something that’s only viable when using the Procore system. Whilst there was definitely more straight line traction, I found the lateral tyre deformation under cornering loads was extremely disconcerting. It made the bike feel squirrelly and vague. It would be fine if you were out for a day of rock-crawling climbs, but for general use I’d already found my lower pressure limit without needing Procore; so again nothing gained.

There are some definite negatives to the system too. The most obvious one is weight, as you’re adding around 200g per wheel, and this is at the rim where its effects on acceleration and handling are most noticeable. Of course there’s the added expense and complexity in setting it up, but I also found that I needed to use more sealant than normal, as a reasonable proportion of the goo clung to the inner tyre where it was wasted. Lastly, and something I hadn’t considered, is the effect the hard inner tyre has on bump absorption. Sure you don’t bottom the tyre onto the rim; instead it smashes it into what’s effectively a skinny road tyre inflated to 90psi—trust me when I say you feel that impact almost as much as hitting a rim. The inner tyre takes up a third to half of the tyres overall height, so you’ll be bottoming the tyre more frequently with the Procore fitted. As the casing can’t deflect anywhere near as far when encountering isolated rocks, the traction and comfort may actually be worse than with a traditional tubeless setup. On this front, we found that running the inner chamber a bit softer (around 70psi) still provided plenty of rim protection without the harsh bottoming sensation.

So this is all sounding pretty negative, but as I said earlier you need to know what the game is before you can see if it has changed. I’m a lightweight trail rider running very wide, strong rims and mid-weight tyres. As a result, I can already use low pressures without excessive tyre squirm or burping, so the advantages of Procore don’t exist for me.

Really wide rims are steadily gaining popularity but most people are still using comparatively narrow rims. When fitted to the 23mm wide test wheels, the Procore benefits became clearly apparent. Normally I’d need to run 24/27psi minimise tyre squirm and burping with these wheels. With Procore fitted, I was able to lower my pressures by 5psi and the beads remained firmly locked in place. It provides a noticeable improvement in traction that will see you attacking loose and rocky trails with greater confidence—both up and down. If you’re used to having 30psi in your tyres to stave off punctures and burping, then Procore will genuinely improve the ride quality of your bike.

While you can certainly drop your tyre pressures without risking rim damage, there’s still a limit to how low you can go before the tyre squirm becomes disconcerting. With or without Procore, you’re always going to have better sidewall support and less tyre squirm with wider rims.

Hardcore with Procore
Personally my lower tyre pressure limit has been dictated by tyre squirm when cornering but I know of others who encounter different hurdles. Even with wide rims they can’t go as low because they’ll simply destroy their tyres; hitting rocks at speed can pinch the casing against the rim and leave holes too big for the sealant to plug. If this sounds like you, Procore definitely offers a solution. The inner tyre works like a bottom-out cushion for the tyre and allows really aggressive riders to use low pressures without the same fear of rim and tyre damage. Of course it can be argued that employing heavy duty DH casing tyres will also solve this problem without the added complexity, but my gut feeling is that the Procore setup will still offer better rim protection. Further to this, if you do suffer catastrophic tyre failure during a timed DH or gravity enduro run, the inflated inner chamber should allow you to finish without needing to stop.

In the end it really depends on your perspective. If your rims are in the 23-28mm inner width range, Procore will allow you to gain the low tyre pressure traction benefits without the risk of burping and rim damage. While the kit isn’t exactly cheap, it costs a lot less than buying a new wheel set with super-wide rims. If your focus is gravity racing, and especially if you’re at the pointy end of things where absolute reliability and security are paramount, then I think Schwalbe has definitely changed the game. Like most things it’s a matter of horses for courses, and in this case I think Procore is best suited to hardcore pros.

Bike Box (03) 9555 5800 / www.bikebox.com.au