Question for tire experts - modern tire pressure?

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MexicoMike

MexicoMike

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I have been trying to figure out why modern bikes' owners manuals recommend such high tire pressure. My three modern bikes - a '14, '17, and '19 all show 38-42 PSI as the recommended pressure. But I find that 34/36 works much better for me on the bikes. My Norton's manual says 28/30, which works fine as well. So what changed that causes the increase in recommended pressure for modern machinery?

It isn't tubes vs tubeless because my '14 R9T has tubes with that same 38/42 pressure recommendation as the tubeless tires on my other bikes. The same high pressures are indicated for my wife's Africa twin tube tires as well as her tubeless Ducati Diavel tires.

When I put new Avon RoadRunners on my Commando a few years back, I just used the same pressure I always used as per the owners manual. I didn't look at any Avon recommendations so I don't really know if they recommend the high modern pressures or not. But I know what works for me... ;)
 
So what changed that causes the increase in recommended pressure for modern machinery?

Tyre construction has changed, I use 30 front 32 rear on my Roadridered Commando.
 
what about weight, both bike and rider? Im seriously light and surely that would mean less tyre pressure?
 
You still vary the pressures depending on the load so a lower load means lower pressures but they will still be higher than tyres made in the 70's. You can email the tyre tech guys giving loaded weights front and back and they should give you the calculated pressures for the tyres.
 
What would be the best F/R pressures for Nortons running standard tubed TT100s.

Question for tire experts - modern tire pressure?
 
Tire company lawyers will disagree but for me, it always depends. The tire companies have to pick a number, so they give you a range.

That said, tires are suspension too; they help your springs/dampers; its a system. The companies can't know all the variables - your weight, application, road conditions, and so on.

For me, to get the most out of a change in brand or model of tire, IMO, there is no replacement for feeling/sensing the tire's performance while I'm riding. Then, when I stop, with that feel in mind, I check both carcass and tread heat by hand and I try to read the tread.

Softer pressure feels better on low speed low load roughish roads, harder feels better on higher speed higher load smoother roads. If my steering feels imprecise/wallowy, then my pressures are too low. If steering is precise but my tires tend to skitter, my pressure is too high. If the tire carcass is too hot, the pressure is too low, tire will wear too fast. If the tire's tread is too hot, the pressure is too high, again, tire will wear too fast. My hand tells me a lot. I feel for difference in temperature between the side walls and the tread.

Inner tubes and radials are not designed to mix. The classic Dunlop K81 is not a radial, neither is the more modern Avon Roadrider - both are bias ply.
 
Interesting. On my AHRMA Sportsman 750 Triumph T140 in a Champion frame, and Dunlop race tires, Dunlop said 29-31 front, 30-32 rear. Lower pressure heats the race tires up and makes them stick. They won't really have much traction at 36 lbs or more. On my modern road racer, using a 200 rear Dunlop and a 120 front, Dunlop says, 22 lbs cold or less off the warmers on the back (and some guys go down from that, without Dunlop's agreement), and something more normal sounding, like 30-32, on the front.

These lower presures don't do much for street wear and longevity, and certainly won't work for carrying a fair amount of weight long distances, but for what it is worth, that's what happens on the race track.
 
I run my roadriders without tubes on a cast alumimum rims at 28 - 30 lbs front and back. They might stick better a few pounds lighter, but I'm too chicken to go with lower pressure, and maybe end up on my ass...
 
xbacksideslider said:
Tire company lawyers will disagree but for me, it always depends. The tire companies have to pick a number, so they give you a range.

That said, tires are suspension too; they help your springs/dampers; its a system. The companies can't know all the variables - your weight, application, road conditions, and so on.

For me, to get the most out of a change in brand or model of tire, IMO, there is no replacement for feeling/sensing the tire's performance while I'm riding. Then, when I stop, with that feel in mind, I check both carcass and tread heat by hand and I try to read the tread.

Softer pressure feels better on low speed low load roughish roads, harder feels better on higher speed higher load smoother roads. If my steering feels imprecise/wallowy, then my pressures are too low. If steering is precise but my tires tend to skitter, my pressure is too high. If the tire carcass is too hot, the pressure is too low, tire will wear too fast. If the tire's tread is too hot, the pressure is too high, again, tire will wear too fast. My hand tells me a lot. I feel for difference in temperature between the side walls and the tread.

Inner tubes and radials are not designed to mix. The classic Dunlop K81 is not a radial, neither is the more modern Avon Roadrider - both are bias ply.
Click to expand...

There are some factory bikes using radials with inner tubes. BMW and others. There are inner tubes designed specifically for radial tires also.

I've been doing some research lately as radials and spokes are in my future plans.
 
Yes, I've always thought that the advice that tubes should not be used in tubeless radial wheels/tires was a bit lawyerly yet I understand that in theory there's more friction, high heat potential, between tube and tire with a soft side wall radial ply than a stiff side wall bias ply. But then as ply design evolved we got stiff sided radials and soft sided bias plies.

Since I use pressures in the lower range for the slower canyons that I often ride, to reduce tube/tire friction, I Iavish talcum powder on both on the tube and on the entire interior of the carcass.
 
Jim, what is your weight when you are on one of your long journeys?
 
Onder said:
Jim, what is your weight when you are on one of your long journeys?
Click to expand...

It's been a few years but last time I weighed the bike alone it was ~470# with fuel. [With the fairing and rack but no backrest]
I weigh 220# and the luggage and rack is generally ~80#
 
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Then not so radical your air pressures. Lot more weight all told then my situation. Not to forget your high speeds and high temperatures.
Perhaps we should measure our hot air pressure at different initial pressures to see what the changes look like.
 
Here is my favorite method.

First check the tire pressure when the tire is cold and set it near the maximum. Then take a ride at your normal speed and weight. Then, measure the tire pressure immediately after stopping. If the pressure has risen less than 10% on the front or 20% on the rear, remove air from the tire. Once you obtain this pressure increase for a given rider, bike, tire, road and road temperature combination, check the tire pressure again while cold and record it for future reference.

So on my bike, if I am heading to the south where high speed and straight roads are the norm I run 42 and 36. If I am heading toward Salt Lake City where I will be going over 10 mountain passes on the way, I drop the pressures by about 4.
 
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Well, when I called Avon years ago when they came out with their Road Riders and was told to use 31-34 for my Commando
don't think it matters but this is with 19 front, 18 rear and Buchanan's in California built shouldered rims
 
comnoz said:
Here is my favorite method.

First check the tire pressure when the tire is cold and set it near the maximum. Then take a ride at your normal speed and weight. Then, measure the tire pressure immediately after stopping. If the pressure has risen less than 10% on the front or 20% on the rear, remove air from the tire. Once you obtain this pressure increase for a given rider, bike, tire, road and road temperature combination, check the tire pressure again while cold and record it for future reference.

So on my bike, if I am heading to the south where high speed and straight roads are the norm I run 42 and 36. If I am heading toward Salt Lake City where I will be going over 10 mountain passes on the way, I drop the pressures by about 4.
Click to expand...


Well said. More scientific.

And, thst’s the method recommended by vendors of slicks at race tracks.
 
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