T.P.M.S./Tyre pressure/MAX P.S.I. ???

[phantom]

First up, I would like to thank the forum/members for all the incredible amount of information available, and what a great forum it is.
Been riding for 52 years and always had a bike and had a ST11 in the late nineties, now have a 2010 ST13 /Black since June last year and loving it.

I have fitted a TPMS to the bike. I set my tyre pressures at 42PSI front and back. Being summer here in Australia i expect the tyre pressure to increase a little more with
the hot bittuman roads. The front tyre can increase to 46/47PSI and rear to 48/49 PSI.
Not ever having a TPMS , would this be normal for that amount of pressure ? This is riding at around 100/110kph, about 60/70 MPH.
I have set my min pressure alarm at 32 PSI and max at 50 PSI.
I run Michelin Pilot Road 4 GT FRONT. ROAD 5 GT REAR

Secondly i have to set a maximum temperature for the alarm to warn me, but at what temperature??

Any information is appreciated and what pressure and temperature settings into the TPMS??
Gary.

 

[TerryS]

Those pressures look pretty similar to what I have seen on my 1300, +4-5 on front and as much as 8 psi at the back. Depends a lot on your right wrist and gassing it out of corners.

I would not worry too much about the max temperature; that might make sense on a car where low pressure leads to massive overheating/disintegration but I doubt that would be an issue on a bike.

 

[Larry Fine]

The front tyre can increase to 46/47PSI and rear to 48/49 PSI.
Not ever having a TPMS , would this be normal for that amount of pressure ? This is riding at around 100/110kph, about 60/70 MPH.

Those are excellent gain numbers, not too high, about a 10% gain.

I have set my min pressure alarm at 32 PSI and max at 50 PSI.

I would set my minimum warning much higher than that, say 38 to 40.

Secondly i have to set a maximum temperature for the alarm to warn me, but at what temperature??

I never changed the temperature warning level on mine, so I can't say.

 

[Andrew Shadow]

That amount of pressure gain due to temperature is normal.
I would set the maximum pressure and temperature warning alarms as high as they will accept so that they never alert. i.e. ignore them. Neither reading is of any value except for curiosity sake.

I agree with Larry, your minimum warning is set to low. As you have seen, when running hot tires the pressure increases to the mid to high forties. Having the minimum warning alert set at 32 means that you will have already lost over 15 p.s.i.g. before you get an alert. That is to much loss before getting a warning. You want more advance notice of a problem than that. I would set the minimum at 40 P.S.I.G.. Because of the temperatures of where you ride and with a cold tire pressure set at 42, I would guess that there would never be a big enough temperature drop to cause your tire pressure to go below 40, so you won't get false warnings at that setting before your tires have warmed up. If you do get an alert while riding, you will know that it is because there is a pressure loss and you will have the earliest warning possible.

 

[Larry Fine]

. . . you will have the earliest warning possible.

Which is the whole purpose of a TPMS. You should be able to detect, find, and plug a leak before dropping to 32 psi. Plus, by the time you're that low, the handling should have already alerted you.

 

[Duporth]

I fitted a FOBO Bike 2 TPMS last year to my ST, and like you phantom I was initially surprised, and a little concerned, at the temp increase from the cold setting to the hot reading after a run on the motorway.
Last week I set 42.5 psi (should do 3-4 weeks until next pump up) on my rear Pilot Road 5 GT and on returning home the TPMS reading was 49. It was a warmish day 30C/86F. Rear runs hotter than the front.
Now I have been educated by the TPMS about temp increases, I am not so concerned. A low reading of course will get my attention promptly.
D

 

[SMSW]

On the occasional very hot day, I've seen my tire pressures nudge just past 50 psi. As long as the cold pressure (before the bike is started in the morning) is at spec (42psi), your riding pressure will be within the pressure limits of the tire. On the occasional cold morning, my TPMS has warned me of low pressure - whether due to air loss or cool temps overnight I do not know, but I check the pressure and adjust it to 42 before riding. It's nice to have that reminder that I'm a couple of pounds low.

I do wonder, however, about a rider in one of those Paris-Dakar style races who gets a flat in the middle of the desert. His pit crew changes the tire, and it is 112ºF in the shade. If he pumps that very hot air into his tire filling it to 42 psi, what pressure is he likely to see as he roars off on the next leg of his race?

 

[mortenk]

Perfectly normal as everybody already stated. I have my pressure alert set to 36 psi but whatever makes you feel good. I did a track day a few years ago and the instructors started by taking quite a bit of air out of my tires. They said that due to the extreme riding we were going to do, they wanted to avoid over pressuring...

 

[dwalby]

His pit crew changes the tire, and it is 112ºF in the shade. If he pumps that very hot air into his tire filling it to 42 psi, what pressure is he likely to see as he roars off on the next leg of his race?

my guess would be 42psi, because if his crew can put air into his tire in the middle of the desert during the race day, they should be able to put more air into the tire wherever they stop for the night.

but more to the point, and useful for those with TPMS wanting to make such calculations:

pV=nRT

p is absolute pressure = gauge + 14.7 at sea level
T is absolute temperature = C + 273

If they start first thing in the morning, let's say the ambient temp is 20C or 293K. Air was put in at 45C or 318K the day before. Absolute pressure is 42+14 = 56 (we'll ignore the 0.7 because we're not likely at sea level so its probably closer to 14 than 15). Pressure drops by ratio of 293/318 = 0.9214 due to temp, to 51.6 psia, minus 14 = 37.6psig.

 

[Al st1100]

I don't have a tpm and check my tires cold . Never bothered no check them hot and why would I unless it looked obviously low. Don't care what the pressure is hot or in high altitude, the manufacturer take's all that into consideration.

 

[Al st1100]

my guess would be 42psi, because if his crew can put air into his tire in the middle of the desert during the race day, they should be able to put more air into the tire wherever they stop for the night.

but more to the point, and useful for those with TPMS wanting to make such calculations:

pV=nRT

p is absolute pressure = gauge + 14.7 at sea level
T is absolute temperature = C + 273

If they start first thing in the morning, let's say the ambient temp is 20C or 293K. Air was put in at 45C or 318K the day before. Absolute pressure is 42+14 = 56 (we'll ignore the 0.7 because we're not likely at sea level so its probably closer to 14 than 15). Pressure drops by ratio of 293/318 = 0.9214 due to temp, to 51.6 psia, minus 14 = 37.6psig.

Dirt riders usually run lower pressure in their tires some as low as 10psi. I'm sure the crew has their calculation for what they want in the tire hot and they are probably using nitrogen.

 

[TMF]

Perfectly normal as everybody already stated. I have my pressure alert set to 36 psi but whatever makes you feel good. I did a track day a few years ago and the instructors started by taking quite a bit of air out of my tires. They said that due to the extreme riding we were going to do, they wanted to avoid over pressuring...

It's easy to get in trouble at the track with tire temps. Race tires have compounds that have less traction at typical street tire temperatures hence tire warmers, warmup laps and decreased pressure. Street legal tires will gain full traction at lower temps and will become greasy if underinflated/overheated like a race tire. A 10% rise in pressure from cold to warm is a rule of thumb for street rubber. Racers run low pressure but not arbitrarily. Too cool then reduce pressure, too hot then add air. When the tire is fully warm it should be in a range specified by the manufacturer and that goes for street or track. The race tire's low pressure is also a form of suspension that works alongside stiff spring and damping. The heat accumulation cycle is not a runaway. As temps increase in a street tire and the pressure rises, the tire flexes less and the rate of heat accumulation decreases. All that is taken into account by the manufacturers and a safe spec is arrived at and put out there to ensure handling quality and tire integrity.

 

[RaYzerman]

I set my low pressure at 36 and the high at 53. Precheck cold before departing....

 

[oude geit]

I have seen temps right at 150 F. I have mine set at 155. Max tire temps are in the 180 F range. Mostly i like to see temps max about 30 above ambient temperature. It will vary from season to season but im mostly just watching them heavily loaded, touring weight, especially in our western deserts.

 

[dwalby]

Dirt riders usually run lower pressure in their tires some as low as 10psi. I'm sure the crew has their calculation for what they want in the tire hot and they are probably using nitrogen.

yeah, I used to ride dirtbikes in the desert here in my younger days, and I realize that you'd never actually run the tires at 42psi for desert dirt riding. I was responding to the premise in the post I quoted that they put 42psi into the tires in the first place.

 

[phantom]

Thank you to all for your replys ... i now have enough info on what maximum and minimum pressure settings to put into the TPMS. I wont worry to much about temperature settings.

Thanks again. Phantom

 

[STraymond]

I fitted a FOBO Bike 2 TPMS last year to my ST, and like you phantom I was initially surprised, and a little concerned, at the temp increase from the cold setting to the hot reading after a run on the motorway.
Last week I set 42.5 psi (should do 3-4 weeks until next pump up) on my rear Pilot Road 5 GT and on returning home the TPMS reading was 49. It was a warmish day 30C/86F. Rear runs hotter than the front.
Now I have been educated by the TPMS about temp increases, I am not so concerned. A low reading of course will get my attention promptly.
D

One thing that I like about the FOBO units is that it will display a calculated pressure that a heated tire would have at 68 F/20 C - in addition to the current actual pressure.

 

[ST Gui]

I don't have a tpm and check my tires cold . Never bothered no check them hot and why would I unless it looked obviously low. Don't care what the pressure is hot or in high altitude, the manufacturer take's all that into consideration.

This ^ is how I roll. Like many riders putting hundreds of thousands of miles over many bikes I never had a TPMS until after owning my ST. Even then I didn't bother until the FOBO became available.

The tire pressure and temperature deltas were noted but only out of novelty. All that was really important was being alerted to a loss of pressure. I removed the temperature reading from the display.

I check my pressures before the first ride of the day and never think about it again unless I were to get an alert over my Sena. In the past checking the pressure might have been done every few months or when the handling felt off or maybe just out of boredom.

 

[drrod]

I have seen rear pressures in the 55-56psi range on a medium loaded bike, one up, 80-90F ambient temp, cruising 85+mph, sweeping corners. Started at 42psi in the morning. I thought the TPMS was out of wack but the numbers correlated with 2 pencil gauges when checked. I am not worried about the high psi numbers. Nothing I can do about it. Like others, I use the TPMS to detect a leak.
I would suggest setting the high psi and temp warnings as high as possible otherwise they will just annoy you.

 

[ATA]

Looks normal for me on my '07 with the same tires. I also picked up a roofing nail a couple of weeks ago and the TPMS did it's job very well. I was alerted by the red flashing light in the unit and slowed and pulled over before it was too low. It went down fast too. So, I endorse a TPMS and Hawks Head T valve stems. And, yes I had a plug kit and micro pump in my side pan.