Gravaa has set their sights on solving the issue of perfect tire pressures with their new electronic wheels that will adjust your pressure while you ride.
The new system from Gravaa uses a miniature pump stored in the hub to allow tire pressure changes throughout a ride. Using the hub system you could potentially add pressure for harder surfaces or drop pressures when tackling looser trails. Gravaa claims their system will also stop the problem of small leakages dropping pressure as the system can continuously add in more air to ensure it keeps to your desired settings.
| We all know riding on gravel roads and mountain bike trails can be demanding. Because the surface of the trail changes throughout the ride it’s always a gamble which tyre pressure you need for the front and rear tyre when you go out for your ride. In the end you often settle for the middle ground regarding tyre pressure. After years of research and engineering we have developed high-end wheelsets which enable you to manage your tyre pressure during your ride.— Gravaa |
Using carbon rims and their own 'advanced hubs' Gravaa has incorporated a miniature high-pressure pump, driven by the wheels using an integrated clutch unit that can be disengaged when it's not needed. A hose runs from the hub to the wheel's valve to accomplish the pressure changes. Gravaa has also fitted an electro-pneumatic control system to ensure the pump is only activated when it is needed. To control the system the hubs can connect to devices using ANT+ and they aim to be able to display relevant information about pressures onto cycle computers.
The idea of a tire inflation system is nothing new as off-road vehicles have been using these systems for years, but only a few companies have tried to bring these systems to MTB. White Crow also created a hub-based inflation product back in 2015; unlike the Gravaa wheels it used a mechanical system rather than an electrical solution. White Crow's solution meant it added a lot of weight with an additional 350 grams per hub and a 200 grams chamber inside each tire. It remains to be seen how much weight Graava's system adds, and the price hasn't been announced yet either.
Gravaa is looking to open orders for their wheels later this year. You can find out more
here.
It’s just the solution is dumb.
This. I remember when some 4" travel "freeride" bikes were coming out we thought they were lame. Likewise, there was a couple years when the pro DH circuit was split between V brakes and discs.
There's so much specialization in mountain bikes now (remember there was a time when there was just XC and DH? and before that there was just mountain biking?) that these previously silly sounding ideas are going to pop up. There was a time that computers were mocked, and no one thought the internet would ever be more than a novelty. Anyway, it's pretty ridiculous to ridicule any innovation that might help someone else when you're hanging out with a fleet of bikes with an singlespeed, downduro, trail, and enduro bike.
Reminds me when all you idiots were decrying 29" wheels a few short years ago. Look at where we are now.
I rode Brandywine (and Iron Hill, Fair Hill & Middle Run) on those rigid canti-lever braked bikes back in the day, and also for the better part of a decade on a rigid singlespeed. That gave me a great appreciation for the comfort of the full-suspension bike I now ride on those same trails. Fair Hill without suspension in the early days before we built the bike-friendly singletrack trails, was adventurous.
We want more moving parts and points of failure. [CHECK]
Also weight, hopefully that adds at least a pound. [CHECK]
Any chance of future updates to add a battery? Would love something to charge. [CHECK]
More cost and maintenance [CHECK]
Limited application [CHECK]
This tech will be standard, along with on-the-fly transforming geometry (at minimum adjustable head angle), seat angle, smart shock pressure, fully wireless electronic shifting. Sensors everywhere detecting ambient temp, humidity, altitude, slope, and compensating for all of it in real-time. Integrated computer for all the calculations and real-time display of info. And it will weigh the same as your bike does now because of advances in materials and other optimizations.
This is how innovation is achieved. Nobody will buy this stuff now, and that's completely fine. But watch.
I'd rather see smart-bike tech like this ANY day rather than e-bikes too.
Do I want lower pressure on the climbs for better traction, but then I roll slower.
Do I want higher pressure on the downs to not bottom out on the rim, but then I have less traction.
Maybe I want that sweet spot that I’ve already found.
data.mlok.net/Rolling_Resistance_Eng_illustrated.pdf
jaydawg69 isn't wrong, but there's a way to present it that resonates better with people:
The rougher the terrain, the lower the pressure. Saying it this way doesn't feel counterintuitive. We know a mountain tire at 60 psi would shake us to pieces on rocky terrain and the same tire at 5 psi is slow on smooth pavement.
Obviously, it gets a lot more complex if we try to find the exact, perfect pressure in a given situation, as it's a complex mix of roughness, tire construction, temperature, etc. For a supple XC race tire, as used in the Schwalbe study, on a typical mountain biking trail, the efficiency continues to improve past the point where the tire vulnerable to pinch flats and is laterally unstable. We can make the sweeping statement "lower pressures are faster" for this tire in this situation.
A stiff, double-layer DH casing with high hysteresis would be a different story, likely having a complex relationship between speed, temperature, and roughness. We couldn't make a simple statement about pressure and speed for self-powered riding. Uplift-assisted riding on fast, steep terrain would be different, of course, and once again the best performance would probably be at the lowest pressure that's safe to ride, but for reasons other than rolling resistance.
It's a strawman argument to say "riding on the rim". I doubt that's what anyone was talking about and a disclaimer along the lines of "... to the limit of safe and practical operation" is implied.
The message is simply that higher pressures aren't necessarily faster, especially on dirt.
If they'd tested surfaces that people actually ride such as rocks, roots and packed dirt there would be some value but they didn't so there isn't.
Maybe rolling through meadows is more common in Germany.
My trails don't look much like either of those things although when I lived in Brisbane the "gravel" results would have been applicable to many trails.
it's all about transfer of energy... Higher air pressure means your getting bounced around/deflected more slowing you down compared to a lower air pressure tire. Obviously there is a law of diminishing return but it's one of the reasons why people like inserts so much.
1. English isn't the first language for the authours, so maybe the descriptions weren't perfect.
2. Even with what sounds like tame terrain, the results were that supple tires at lower pressures produced less rolling resistance. The effect is likely to be even greater on the kind of terrain you described. This is not a reason to completely dismiss the results.
" It sinks into the ground less"
Yeah... I'm not sinking into the ground when riding rocks and roots so I'm gonna stick by my claim that their results are not relevant to the many many trails that are not soft grassy meadows or gravel roads.
In the pavement test, the rolling resistance decreased with increasing pressure. Switch to gravel and the trend reverses: rolling resistance increased with increasing pressure. More testing is obviously warranted, but it would be strange if this trend reverses as the terrain gets rougher.
Fat biking you don't want anything that will have issues in sub-zero temps and air systems end up with a lot of moisture, moisture freezes, valves stick pumps seize.
"ride roots/rocks at 50psi vs 25psi and see what is faster and more in control..."
I'm not arguing against lower pressure being better for grip on rocks and roots but that's got nothing to do with rolling resistance.
Probably not reverse but certainly it's possible for the difference to be irrelevant. Gravel is too small for suspension to be effective so tyre flex is doing all the work. Rocks and roots are handled by suspension so tyre pressure probably won't contribute nearly as much.
But we don't know because the study is too narrow and shouldn't be quoted as some mountain biking gospel.
What I am saying is the study is not particularly relevant to how many people ride so people should stop taking it as proof that lowest pressure you can run is best.
People use inserts for grip. I've never heard of anyone claiming their bike rolls better from them.
You seem to be conflating the idea of low pressure being good for riding in general with the idea of low pressure being best for rolling resistance.
You can start by checking out the excellent information below. Much of it is from road bikes, which will surely tempt you to entirely discard it. All observed trends are toward lower pressures reducing rolling resistance for rough terrain and there is no reason to think this suddenly reverses in the presence of hydraulic suspension.
Josh Poertner, Part A
Josh Poertner, Part B
Tom Anhalt
Poertner & Anhalt
Jan Heine
FSA
"Probably not reverse ... "
I agree. If the trend is always toward lower pressures being more efficient in rougher terrain, it would be extremely surprising if this trend suddenly reversed in the presence of greater roughness on your personal trails or with the addition of hydraulic suspension.
"Gravel is too small for suspension to be effective so tyre flex is doing all the work."
Tires, forks, shocks, frame flex, your body: they’re all suspension. They all have different properties, they all contribute, and their properties and contributions can be analyzed.
Supple tire casings are designed to have as little hysteresis as possible. Forks and shocks with dampers are designed to have extremely high hysteresis – that's the whole purpose of dampers.
Hysteresis is a major cause of rolling resistance in tires. If dampers add a great deal of hysteresis, it is reasonable to assume the most efficient suspension is to have the component with lower hysteresis (tire) handle as much of the displacement as possible, which will occur at lower pressure.
The tire has a further advantage due to only a few grams of unsprung mass, while the hydraulic components have hundreds to thousands of times as much.
"Rocks and roots are handled by suspension so tyre pressure probably won't contribute nearly as much."
This statement implies the tire flexes less on larger impacts, which is clearly false. While it’s true the hydraulic components move more during larger impacts, the tire also flexes more. Both suspension elements are affected more during larger impacts.
"But we don't know ..."
"... proof ..."
Nothing can be an absolute certainty, but that doesn't mean everything is absolutely uncertain. Given the evidence presented, the notion of an inverse relationship between trail roughness and pressure (within reasonable limits of tire safety and stability) in terms of rolling efficiency probably meets the "balance of probabilities" standard for burden of proof.
It is possible there exists a pressure so low that additional losses due to tire hysteresis overcome additional gains due to efficient suspension (excluding the obvious case of the tire bottoming against the rim). The Schwalbe study found no evidence of this. A lower limit on pressure is imposed by the need for tire safety and stability; factors other than rolling resistance are likely to prevent us reaching the point of minimum rolling resistance at low pressure.
If you choose to view the situation as completely uncertain, despite the provided evidence - and other evidence in the vastness of the internet - then feel free to continue using rock-hard tires while the rest of us place our bets on the lowest practical pressure when riding rough trails.
As I've said before, run as low as you can.
With such a dumb conservative attitude, we would still ride bikes with no tires, no droppers, no suspension, and probably square wheels. Tire pressure is probably what affect the most the riding performance and traction. it would be incredible if i could modulate my air pressure from 15psi to 30 psi while riding.
If you don't like innovation, you can still ride a rigid single speed!!
Innovation starts somewhere. People used to laugh at droppers....”why do I need that when I can just get off and use the quick release??!!”
Just saying
f*ck people, it’s this kind of stuff that makes mountain bikes so damn interesting ffs.
Apart from the usual slate of non-believer that state tire pressure regulation is worthless without ever-ever trying riding with one (yep, I remember the same about dropper posts.. and before that 29ers!) , I can add the following clarifications on WhiteCrow Tech system that are misinterpreted in this article:
A) the added weight in the hub was indeed about 300gr in the last prototypes, but this was because we dimensioned the system to support both FAT and Plus tires, which require moving a lot of air. For standard “2.5” tires this could be dimensioned quite smaller and therefore at least 50gr lighter.
B) The added weigh of the last prototypes of the inner chamber by a-dugast was less than 150gr, and still less than most current current “mouses” (which btw: it’s a function that we also perform!). Everybody agrees that a some kind of tire insert is must to properly ride at low tire pressures!
C) the system was mechanical by choice, in the same way that SRAM stuck for mechanical shifters 11spd while Shimano went electronic. This was to enable max reliability and full range temperature compliance for fat bikes (try shifting on electronics at -30 F and you let me know how it goes!). To be clear, I’m actually a embedded IT engineer… and f*k making it fully mechanical it was very, very hard. Of course, it a total no-brainer making it electronically actuated, and our patents fully cover this.
Why did not get to the market… simply because pulling off this complex engineering/ manufacturing project in the European startup ecosystem was too hard due to much constrained risk capital availability.
And for the Pink bike editors.. .do you homework a bit ! The name of the company is “WhiteCrow Tech” not “White Crow” ( you don’t call RockShox - “Rock Shox” do you?? )
Wait 1 second if it can pump tires could it not also propel the bike with some type of air motor?.....I coin the the term A- bike. I will need to reach out to these folks....
Convenience of using CO2 but you could use it as much as you want.
Sooooo basically this: road.cc/content/review/260467-fumpa-minifumpa
but with a pressure readout (to 1/10th of PSO obvi) and ability
to charge phone/lights from it.
Question is: who is financing the research of this technology, knowing that it won't sell? Does Gravaa belong to a big industrial group or something?
Wouldn't it be simpler to strap a CO2 canister to the hub with a tiny hose to the valve and a miniaturised piezo powered or button cell battery 3 way micro solenoid valve to bleed air out of the tyre or fart more in from the canister? Or have a fitting on the end of the axle and have a CO2 cartridge tied to the frame or fork leg? Gotta be doable for less weight penalty, plus lots of people already carry CO2 on them.
Thinking out loud you could have a custom axle hub combo with a rotary seal inside the hub. Fit the axle to the bike, charge the axle/reservoir. With a hose to the hub you could house the valve on the hub itself to avoid having a large mass out at the rim which might cause off balance. No hideously complex pump clutch arrangement.
It's not appealing to me but I can see the benefits for some people. Like a lot of people said, suspension forks and disc brakes were poo pooed on bikes initially, look where we are today.
Example situation:
—> arrive at a rock slab, tire pressure decreases.
—> just before the transition, pressure increases to help prevent bottoming out the rim.
—> chunky section? Slightly drop pressure
—> going off a jump? Tire pressure increases for the landing and immediately drops after that.
Same for enduro, system knows you want 20psi or something. If it drops more than 10psi it refills it instantly.
.https://www.bridgestonetire.com/tread-and-trend/tire-talk/airless-concept-tires
We will have adaptive profile, addaptive tread and addative ride soon enough. Just soon enough to get outdone by the hover bikes.... we wont even need tires. Oh and I forgot infinite wheel size adjustment ( 26 aint dead!) will be part of the bridgestone bike wheel/tire. I hear they are partnering with the guy at Superwheel on some extra features.
This will make riding absolutely Gravaay
There is a lot of venture capital around. It gets put into some marginal things.
Things which have rightly ‘stuck’ in the industry:
Light, well designed suspension from Canyon, Transition and the Big Guys - excellent
Mondraker, Transition, Cotic, and Dan Stanton’s shift in geometry - excellent
Tubeless which works - excellent
Disc brakes from Hope and the two Big S’s - excellent
Droppers with no sag (you know who you are) - excellent
And pushing for marginal gains can add up all over the place - lighter, stronger, wider rims; Kevlar beads in tyres, carbon bars (thanks Nukeproof and Renthal), and so on.
And then....I’ve seen a lot of dead-ends in MTB engineering since the 90’s....Darwin knows best
But it would seem to make a lot more sense to mount the pump/canister on the frame and have it directed to each tire through a sort of CTS system like on military vehicles. Keep the weight off the hubs and have 2-3 preset tire settings to switch from fed though small airhoses.
Done right you wouldn't have to even swap wheels to have the same control unit on multiple bikes.
Thank you!!
How would you get air from the bottom bracket into moving wheels?
What, you smack your rims on your rides? Well dude ride freaking better. Smacking rocks fast af doesn't mean you are a good rider you choom.
aside from that i incompletely agree . This inflator invention is trying to convince riders that they have a problem where none exists .
Mtb industry: here's another stupid f*cking idea from the pile of useless expensive shit pile we keep throwing at you because we don't want to keep 1 standard to keep simplicity and costs down
PS Pinkbike ran the article on the people who created a handlebar alignment tool back in November, and everyone hated on that too. www.pinkbike.com/news/dnr-designs-reveal-a-new-tool-to-align-your-handlebars.html?trk=rss
it is 1 April ?