Another tire pressure question

[dcameron]

Recently purchased an '11 r1200r and manual says tire pressure should be 36 front and 42 rear. That's it - no other recommendations. However on my '03 r1150r the manual made recommendations based on whether riding 1 up, 2 up or 2 up loaded, anywhere from 32f-36r to 36f-42r. Any info., comments on this change. I only ride 1 up and find the 36f-42r somewhat harsh.

[JohnM]

However on my '03 r1150r the manual made recommendations based on whether riding 1 up, 2 up or 2 up loaded, anywhere from 32f-36r to 36f-42r

This applies to my `09 R12R as well.

Out of curiosity, do you have tires with tubes?

[dcameron]

No - tubeless - Dunlop Battleaxe BT021R

[Bill Stevenson]

That is a change. Dealers for years have pumped the tires up to the new recommended levels and I always had to drop them back after my bike is serviced. The dealers claim that most bikes coming in for service have under inflated tires. By over inflating them a bit it is presumed that they will stay inflated enough for safety for a longer period of time. Nitrogen is popular with dealers because the tire pressures don't fall when it is used. With this as a back drop it can be assumed that this new higher pressure recommendation has come about because of dealer feedback. If you are conscientious in checking your tire pressures frequently it seems to me you could lower the pressures to suit your preference. One rule of thumb is to inflate the tires to a target pressure cold, then ride the bike until the tires have warmed up and then check them again. The target should be approximately 10% pressure increase over cold. If the tires are over inflated to begin with the increase will be less than 10% and if under inflated the increase will exceed 10%.

[ammolab]

My BMW M Coupe has a similar recomendation.... For the USA they only give pressures for the MAXIMUM load in the vehicle while for the rest of the world they give tire pressures for driver only and then (higher) for loaded conditions.

Giving the MAX load recomendation makes sense in SUE HAPPY USA.

One word explination: LIABILITY!

[deilenberger]

I'd have to go look at my M-Coupe door panel with the tire pressures, but other BMW cars I own list both normal and fully loaded pressures (my M-Coupe is an '01..)

The original recommended R12R pressure was 32F/36R for one up. That's what I run unless I'm going touring with a bunchacrap - when I up the pressure several PSI front and rear. The pressure has to be temperature compensated since it is assumed the bike and air is at 20C (about 68F).. and the pressure does vary a LOT with temperature (I have a tire-pressure-monitor system that shows both real pressure and tire air temperature..)

[Clem]

Same situation across the pond.
Here in Japan, 2012 R1200R BMW owners manual
suggests only one pressure setting, period!
2.5 bars Front and 2.9 bars Rear tire
That's roughly 36 psi front and 42 psi rear tire.
After reading these threads, I asked my dealer.
Got no explanation for the difference.
Just an uncomfortable smile and shrugged shoulders.
I'm still going to use my common sense
when temperature, speed and loads vary.

[diethornig]

yeah, i have one also with the same problem..

[Woland]

Not to be difficult, but I prefer to adhere to the tire manufacturers recommendation.

[deilenberger]

Not to be difficult, but I prefer to adhere to the tire manufacturers recommendation.

If they give one. In the US the only company that does is Metzler. The other companies refer to the motorcycle manufacturer's recommended pressures. Some people confuse what's marked on the sidewalls for recommended pressure.. it isn't. It's maximum pressure, not the pressure the tire is intended to be run at.

[deilenberger]

That is a change. Dealers for years have pumped the tires up to the new recommended levels and I always had to drop them back after my bike is serviced. The dealers claim that most bikes coming in for service have under inflated tires. By over inflating them a bit it is presumed that they will stay inflated enough for safety for a longer period of time. Nitrogen is popular with dealers because the tire pressures don't fall when it is used.

The air you breath is ~78% nitrogen. I know lots of things are claimed for nitrogen, but it's basically a waste gas produced when oxygen is extracted from air.. as such, it's REALLY cheap. The nice green valve caps are a nice touch though..

With this as a back drop it can be assumed that this new higher pressure recommendation has come about because of dealer feedback. If you are conscientious in checking your tire pressures frequently it seems to me you could lower the pressures to suit your preference. One rule of thumb is to inflate the tires to a target pressure cold, then ride the bike until the tires have warmed up and then check them again. The target should be approximately 10% pressure increase over cold. If the tires are over inflated to begin with the increase will be less than 10% and if under inflated the increase will exceed 10%.

That rule of thumb was for non-radial tires, ie - bias ply. A radial tire flexes a LOT more then a bias ply (which is why the grip is so much better) and the flexing creates heat... enough that the increase at a recommended "cold" (which is actually 20C/68F) pressure to a hot tire (say 110F or so - which I often see in mine in the summer) will be WAY WAY more then 10%. (From memory, my 32PSI cold pressure becomes something like 44PSI hot with that sort of rise in temperature... and conversely, if I take off from the garage with a tire at 45F that was correctly filled at 68F - to 32PSI, it will usually be 29-30PSI at 45F. It rather quickly warms up to > 68F..

[Bill Stevenson]

"A radial tire flexes a LOT more then a bias ply (which is why the grip is so much better) and the flexing creates heat... enough that the increase at a recommended "cold" (which is actually 20C/68F) pressure to a hot tire (say 110F or so - which I often see in mine in the summer) will be WAY WAY more then 10%."

Don,

Now you've got me curious. I have checked tire pressures cold vs. warm, but it has been a while. For most of my riding I set the front a 33 psi, and the back at 42 psi and have checked to see if the pressure went up by 10% or so and thought it was in the ballpark. But I will double check this now that you prompt me. As far as nitrogen goes, you and I see eye to eye.

Regards,

Bill