Tyre pressure

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Alan L

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Hi all,
I was wondering about the finer nuances of tyre pressure. I have read various posts as well as the owners manual and there is a considerable range of opinions.
I am running Dunlop K81s front and back. I’m very large at 2m and 125 kg. My riding is almost always solo.
As the pressure change what variations do we notice. A grossly under inflated tyre is obvious and I guess a highly over inflated tyre must give a harsher ride but what other effects do smaller variations have. I guess the footprint on the road would have to change.
al
 
Alan L said:
Hi all,
I was wondering about the finer nuances of tyre pressure. I have read various posts as well as the owners manual and there is a considerable range of opinions.
I am running Dunlop K81s front and back. I’m very large at 2m and 125 kg. My riding is almost always solo.
As the pressure change what variations do we notice. A grossly under inflated tyre is obvious and I guess a highly over inflated tyre must give a harsher ride but what other effects do smaller variations have. I guess the footprint on the road would have to change.
al
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Hi Al. I run my K81`s at about 24 psi. Any higher is too rough and as you know they will increase as they warm up. Cheers, Max.
 
I use the pressure listed in the manual for the Norton - OEM wheels/Avon RR tires. On all my other bikes, I use pressures considerably under their manual's spec. Most of them show pressures in the 38-42 range which is much too high for my use/riding style. They handle much better with considerably less pressure than spec.
 
It never mentions rider weight. That surely has to have an effect.
 
My layman’s understand is that basically, higher pressures will firm up the ride considerably because tyres are part of your suspension. They’ll also make it turn in quicker / easier. But the smaller contact patch gives less grip, especially during acceleration and braking.

Lower pressures give more grip via a wider contact patch, especially during acceleration and braking. But they’ll make the steering heavier and slower. Too low can allow the rear tyre to creep on the rim and tear out the valve.
 
On my K81's anything under 26#(rear) squirms, but then I'm @ 230#. 26-28#(rear) is just right for good response and reasonably smooth ride with plenty of grip. Front is fine @ 28#.... Any higher is like sitting on a rolling rock, and a tight twist and bump has the rear hop over with me puckering. There's not much range before I notice pretty major changes in handling behavior, so I check before almost every ride.
 
There is a considerable differance between cold and when the tyre is hot, pressure.
Solo should be via the owners handbook, but bear in mind a rear set at say, 28psi, will jump up to over 30 psi after 20 minutes of spirited riding!
It's something only you should feel comfortable with when tyre is cold, as if set too low, the bike will handle like a camel !
 
My bike arrived with 40psi front and back, in 10 year old TT100s. It rode really well, but I dropped it to 30/28 out of respect, which introduced a wobble at 30mph (one handed). My new TT100s are also at 30/28. No wobble, but still not as fine steering as it was at 40psi.
 
The riders handbook is out of date, today's tyres have less supportive tyre walls and need higher pressures but it depends on the tyre. Best ask the tyre manufacture giving bike and rider weights.
 
A MotoGP tire tech told me you should never drop more than 4 psi below recommended cold max (as embossed on most tires) due to the risk of hitting potholes, larger-than gravel obstacles or road debris which could cause the carcass to separate, not necessarily at that point. Also, modern street tires heat up pretty quickly. Running lower pressures increases traction by increasing heat, but it's not all that necessary if you take the time to get the tires hot from friction.
 
Alan L said:
Hi all,
I was wondering about the finer nuances of tyre pressure. I have read various posts as well as the owners manual and there is a considerable range of opinions.
I am running Dunlop K81s front and back. I’m very large at 2m and 125 kg. My riding is almost always solo.
As the pressure change what variations do we notice. A grossly under inflated tyre is obvious and I guess a highly over inflated tyre must give a harsher ride but what other effects do smaller variations have. I guess the footprint on the road would have to change.
al
Click to expand...
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.
 
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