Tire pressure talk

[Zzzorse]

"Talking tires with Josh Poertner – new discoveries about the relationship between pressure and performance indicate new directions for research and development."

http://trstriathlon.com/talking-tires-with-joshua-poertner/

 

[DavidCH]

Interesting, I get a great ride on my mountain bike - hybrid - I swapped the old wheels out and put Mavic Aksium's on with a 33mm cx tyre and at 70 psi. Getting a flat on these it's so easy to change the tyre you don't really need a tyre lever. I take the Pedro's levers with me to help others. The interesting thing about the article was finding out the pressure of your pump could be out by 12%... Is there a place where you can recalibrate your pump? Now that's a little worrying.

Also if you have sealant in your tyre and the valve dries up, when you force air into your tyre, are you damaging the pump's calibration?

 

[hoyden]

After replacing 25mm 100+psi racing tires with 28mm 85psi commuter tires on my Silvio I should complete the job by adding wings.

 

[ratz]

wings

We can get you some nice fairy wings at the Shakopee Renfestival

 

[hoyden]

We can get you some nice fairy wings at the Shakopee Renfestival

I might could like those wings. There's just one small flaw in my implementation: when I take flight I lose propulsion. Back to the drawering board... or put my trust in Lycoming.

 

[ratz]

I might could like those wings. There's just one small flaw in my implementation: when I take flight I lose propulsion. Back to the drawering board... or put my trust in Lycoming.

Strictly a dietary issue.

 

[McWheels]

There's a chap does rolling resistance tests at various pressures. I've been running Schwalbe greenguards for years without realising how good they are at going fast.

http://www.bicyclerollingresistance.com/tour-reviews/schwalbe-marathon-2015

 

[snilard]

This is what Jan Heine is telling us for years. That to get best from your tires You need supple tires pumped to correct pressure. And it is better to be 10 psi under this correct pressure than be 10 psi higher. On rought surface most loses are not ocuring in tire itself but in riders body.
So that is why I use 28 mm tubeless Pro Ones at lower pressure than my friend with 40 mm Marathon Racers

 

[ratz]

This is what Jan Heine is telling us for years. That to get best from your tires You need supple tires pumped to correct pressure. And it is better to be 10 psi under this correct pressure than be 10 psi higher. On rought surface most loses are not ocuring in tire itself but in riders body.
So that is why I use 28 mm tubeless Pro Ones at lower pressure than my friend with 40 mm Marathon Racers

I will point out 1 warning; with the FWD; on the front tire; you do have to carefully test lowering the pressure; there is a point where it gets too low and the front tire will get "squirrelly" It's best to start 5-10psi below max for the tire; and learn how the bike feels. Then after you have master the bike; start lowering the pressure. When you hit that squirrelly point you will know. You just can't get around the fact that we ask a-lot more of our front tire on an MBB than other bikes do.

 

[snilard]

I will point out 1 warning; with the FWD; on the front tire; you do have to carefully test lowering the pressure; there is a point where it gets too low and the front tire will get "squirrelly" It's best to start 5-10psi below max for the tire; and learn how the bike feels. Then after you have master the bike; start lowering the pressure. When you hit that squirrelly point you will know. You just can't get around the fact that we ask a-lot more of our front tire on an MBB than other bikes do.

Can you explain term "squirrelly", please? I understand that it is from squirrel but don't understand how my bike should ride when it occurs.

 

[bladderhead]

It means that your bike is wobbly and hard to steer. Some people say "squirly"

 

[castlerobber]

Can you explain term "squirrelly", please?

Unpredictable, changing direction suddenly and unexpectedly. The way a squirrel, mouse, or other small rodent darts around when running from place to place.

 

[snilard]

Unpredictable, changing direction suddenly and unexpectedly. The way a squirrel, mouse, or other small rodent darts around when running from place to place.

Thank you. Fortunatelly even with my low pressure this is not my case.

 

[Emeljay]

I'm riding on Schwalbe Marathon Plus 559x35 tires at 60-70 psi (recommended is 55-95 psi). This gives me a smooth ride as well as very few flats!

At first use I tried out 95 psi, but the ride was very harsh. So I started lowering psi first at 80 which gave a better ride. Then tried 70 which was smoother ride yet seemed fast and stable. (I'm about 150 lbs, and usually commute with 25 lbs in panniers and bike is about 30 lbs) Then after a few months of riding and not checking tire psi it was very smooth but slow rolling. When I checked tire pressure it was about 50! So now I pump to 70 and check weekly.

 

[ratz]

Unpredictable, changing direction suddenly and unexpectedly. The way a squirrel, mouse, or other small rodent darts around when running from place to place.

Ah the fun with languages;

This may be something that only bothers me or it may be a tubeless thing. When the pressure gets too low I can feel the lateral left to right motion of the rim over the top of the tire; it becomes like the tires is hydroplaning on the rubber. Steering in put becomes slower and reversals of steering input few slower; that messes with my head and I make errors. It also "Feels" like the tire will come off the rim; obviously it won't but if my mind and had a mind I wouldn't have these issues.

If it's just me that's great.

 

[trplay]

I think it might be you have moved the threshold over to a balloon tire ride with the 28mm size. A comfy ride but the riding on rail feel is gone no matter the amount of air.

 

[rfneep]

This finding of suspension losses at higher pressures has been talked about by Jan Heine and the Compass Cycle people for several years. It is good to see it confirmed.

I've started to take it seriously with my Q650b, and so far the (anecdotal) results seem pretty surprising. I'm running 584 x 42 mm Pacentis Pari-Motos on low-level Mavic CrossOne wheels, and have yet to hit a low pressure limit. In particular, I've taken the pressures down to 40 psi - front and 35 psi rear and it seems to be as fast and as low rolling resistance as at more conventional higher pressures. And it is very comfortable! Very muted bumps even over some rough broken up roads here in WI. On smoother roads, the bike just rolls and rolls on its own. In contrast, it surprisingly feels faster and rolls better than my Volae high racer with 650c x 26 mm tires. The Pari-Motos have decidedly more supple walls than the Serfas Urbanas I have on the Volae (at about 80-90 psi on them). Makes the Quest a potential speed demon...

This is well worth exploring. It is making me look much more aggressively at tires with supple sidewalls and at lowing the pressure. I suspect I'll use some tubeless sealant in the tubes to provide puncture protection even when tubed. My understanding is that tires that are really supple tend to not have much inherent puncture protection.

Fun times!

Ray

 

[DavidCH]

I will go back to the tire pressure issue I have with my V , the rear tire doesn't inflate properly as the sealant has dried in the valve. I have to use tremendous force to get just a little air in. It can't be good for the pump. So what's the best way of dealing with it?

Idea 1. Put a hole in the tire and loose pressure and then undo and replace the valve?

Idea 2. Just undo the valve and get orange sealant sprayed everywhere and clean/replace the valve.

Idea 3. Keep grunting ...

 

[RojoRacing]

I will go back to the tire pressure issue I have with my V , the rear tire doesn't inflate properly as the sealant has dried in the valve. I have to use tremendous force to get just a little air in. It can't be good for the pump. So what's the best way of dealing with it?

Idea 1. Put a hole in the tire and loose pressure and then undo and replace the valve?

Idea 2. Just undo the valve and get orange sealant sprayed everywhere and clean/replace the valve.

Idea 3. Keep grunting ...

Idea 4. Ask a mtber

Rotate your wheel till the stem is at 3 or 9 o clock then wait a min for the sealant to drain to the bottom of the tire. Now with a rag in hand release the air like you normally would allowing the rag to catch the tiny bit of residual sealant in the stem, it wont be much at all. Now you need to remove the valve core from your stem and run a tiny pipe cleaner down the bore of the stem body. The valve core likely has dried sealant in it as well which is most the reason for your grunting. It's very hard to clean a core so I suggest you replace it with a new one. You can buy replace cores online for $2-3 each or go through your stockpile of old punctured road tubes and steal the removable cores from them. After I discovered some brands of road tubes come with removable cores I made sure I only bought that kind. Now I've got a dozen clean road tube cores ready to drop in my mtb wheels at any time.

Best way to avoid this problem is to use a little common sense about how the sealant flows. Any time you add, remove or check the air make sure to allow the sealant to drain away from the valve first, it only takes 30 seconds.

 

[DavidCH]

I must have been a prize dork not realizing that. Anyways. The funny thing was the valve was completely air tight and even pressing the knobby bit in no air would come out. So I took the rear wheel off the bike and put it in the road and rotated the release of the valve and the f'ing thing just kept on rotating. So I got the pliers and pulled it out like a tooth. It had quite a bit of rubber growth at the end of it. No sooner had I done that then I got a little sealant easing out of the beads and then I thought "I hope it pumps up first time after I replace the valve".
It did!