Video: Tech Talks - Data Under Pressure Part II, Presented by Park Tool

Aug 30, 2018
by Pinkbike Staff  
Tech Talks Presented by Park Tool

In this episode, Calvin and Truman take a look at the Tyrewiz, and ask you how the data from the Tyrewiz could prove useful for your ride.

Tech Talks Presented by Park Tool is a monthly video series hosted by Park Tool's own wrench whisperer, Calvin Jones. The series covers the A to Zs of some of the most prevalent repair jobs, with the last highlighting how to bed in brakes.

Data Under Pressure Part II

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Need more Calvin in your life?

Episode #1 - Tubeless tire installation and conversion
Episode #2 - Saving that bent disc rotor
Episode #3 - Derailleur hanger alignment
Episode #4 - Shimano and Crankbrothers pedal service
Episode #5 - Trailside wheel repair
Episode #6 - Trailside chain repair
Episode #7 - Derailleur limits and cable tension
Episode #8 - Derailleur setup
Episode #9 - Fork wiper seal replacement
Episode #10 - Clipless pedal setup
Episode #11 - New cleat setup
Episode #12 - Top 5 next level shifting issues
Episode #13 - Fixing cassette play
Episode #14 - Gearing hacks
Episode #15 - Fixing sticky pistons
Episode #16 - Lubing fork seals
Episode #17 - A cleat's story
Episode #18 - Tricks of a mechanical mind
Episode #19 - Handlebar Trimming
Episode #20 - Chain Line
Episode #21 - Tools for a trip
Episode #22 - Bedding in brakes
Episode #23 - Direct Mount Chainring Install
Episode #24 - Wheel Balance 101
Episode #25 - Data Under Pressure, Part I

Stay tuned for more mechanical how-to videos with Calvin returning on the last Thursday of every month to show you the easiest way to get the job done. Want to know more? Park Tool's how-to section has you and your bike covered. / @ParkToolCompany

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  • 18 0
 Most riders these days are riding around on flat tires trying to convince themselves - and anyone else who'll listen, that's what the tire engineers intended..... then they brag about how awesome they are 'cause they destroy 3 rims a year. LMAO at all of you.
  • 9 0
 @ParkToolCompany a few years ago I had a look at 100 Hz dynamic tyre pressure using a ShockWiz prototype sensor. Unfortunately, it was surprisingly boring data. Even on big jumps and hits there was only a very marginal change in pressure, perhaps 0.5 psi for less than a tenth of a second. I didn't go any further with tyres as the data looked so unpromising.
My thinking at the time was that the volume change due to tyre deformation was relatively small compared with the overall volume of the tyre. Also, unlike a fork / shock, the tyre is made from a more elastic material, so a localised deformation at the bottom of the tyre may stretch the remainder of the tyre's diameter, which might reduce the pressure change you could measure. However, possibly the biggest factor is that you are measuring the pressure at the valve which could be a relatively long distance from where the deformation occurred. During a dynamic deformation (unlike in you forklift test which was steady state), the pressure throughout the tyre volume will be a little different and some damping of the pressure will occur. We have been able to observe this on suspension by daisy chaining many ShockWii together and looking at the pressure after travelling through 5 hoses and 5 devices. At each ShockWiz further downstream, you see slightly lower peaks and troughs in the data, and a the data looks smoother. This isn't a big deal in suspension as the pressure changes you are looking at are at least a few psi, but in the world of tyres, this effect would be very significant.
  • 6 1
 Your compressor, my floor pump, and that hand pump we both borrowed from someone on the trail all produce a reading that may or may not be accurate (Read: Probably isn't 60 PSI in your minions). This removes that inconsistency because you're always using the same gauge to measure your tire pressure. Probably a much better product for the Plus/Fat crowd where those deviations in tire pressure have a more obvious effect on traction and tire roll.
  • 4 1
 Great vids. For those of us that ride skinny tires sometimes, can you guys do a roadie test? How about how much (if any) psi increases on a hot summer day? Let's say a 700x25c rear tire starting at 85 psi over a 100k ride.
Keep up the great work.
  • 2 0
 and on the other end of the spectrum, lets see the fat bike test as well. Volume has to play a big factor in all this. I may also start running a bit more, maybe 20 is better than the 16 I've been running in my 29+
  • 3 0
 I'm probably missing the point, or they are. The looked at two occasions that might cause issues.
1. Straight impacts through rock gardens.
2. Burping caused by sideways landings.

Between the two, sideways landings were critical. That is, the tire would burp in a sideways landing at a pressure which wouldn't cause issues in that rock garden. Their data didn't show any pressure variation leading up to that burping and it is also not likely that there should have been any.

With that in mind, why should we log the tire pressure during the ride?
  • 2 0
 I'm a geek, I love data to look at, and I love these videos.
But unlike a ShockWiz I think you just proved this device does not offer much (any) value over monitoring your tire pressure manually.
  • 1 0
 I’ve never understood why people struggle / debate this so much.. figure out your psi based on tire roll and when your rim bottoms out.. my sweet spot on noble tr33 and 2.3 to 2.4 tires is 25 front and 27 rear. I’ll damage my rim and experience tire roll when I go lower..
  • 1 0
 I was wondering if you have looked at any data comparing tire (or fork/ shock) pressure changes with elevation change. I have been curious for a while how much variation you will see in tire pressure throughout a long descent or climb. If it is substantial should you adjust your pressure to be optimal at the highest elevation, lowest elevation or somewhere in between?
  • 2 1
 Solid, I'm really bummed out about burping. Man things are made poorly. That being said, I couldn't personally do any better, probably just best not to rely on things too much.
  • 2 1
 Run an insert like Schwalbe Procore and burping ceases to be a problem. Tire pressure becomes a choice between grip and support without the risk of flatting or damaging your rims.
  • 4 0
 try ghetto tubeless, I never burped when setup that way. Guessing it has to do with having a continuous rubber on rubber seal
  • 2 0
 @Grmasterd: same. Never bumped a ghetto either or pinched a side wall.
  • 3 0
 Since I've gone ghetto tubeless I've never ever burped again. It's like having tubular tire
  • 1 0
 Yup - ghetto tubeless using a sliced tube pretty much solves burping. I know Jared Graves was using it on the EWS a few years back. Works great.
  • 1 0
 Interesting video and nice to see how the data was collected and tested - I might have to go back and watch part 1!

The question is then... What should I be running front n' back?!
  • 3 0
 Just too many variables to compare person to person... the best pressure will vary for each rider depending on: Weight of rider, width of tires, width or rim and tire casing (EXO, DD or DH), style of riding and terrain. You just have to test for yourself and find what works best for you.
  • 2 0
 @islandforlife: Exactly, I wonder every time anybody talking tyre pressure without considering the weight of a rider. I have something aroung 100kg and If I would run 15psi thats for me a flat Tyre. New rims 3x per season....
  • 1 0
 @islandforlife: I agree there are too many variables. I assume there's also the weight of the bike, they kit you're wearing for that particular ride and everything else in between!
  • 1 0
 All I care about is getting done the rear tyre pressure low enough for grip without dinging my god dam rim. So far 26-28psi for safety
  • 3 0
 Honzo ST FTW!
  • 1 0
 true but the honzo is underforked!
  • 1 0
 Guerrilla Gravity Pedalhead!
  • 1 0
 Thanks for the 0.2 psi drop per tap on the previous vid, quite helpful actually!!
  • 1 0
 Nice vid ! He's right, watch your manners lads ! Too much burping going on ! Big Grin
  • 1 0
 cush core & a $15 tire gauge

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