Tire Pressure- cold vs hot??

[betoney]

I use a tire pressure monitor on my bikes and notice quite a difference in pressure increase between cold and hot between the two bikes.
I also have a large Honda VFR1200X which weighs over 630lbs and uses a 150 profile rear tire.  On both bikes I use 36F/38R tire pressure.  On the Yamaha on a hot day the pressure will rise to about 42F/44R while the heavier VFR with the skinny rear tire will rise to 45F/48R and the alarm on my TPMS will start flashing.  Is this normal?  This is the only bike I have owned that doesn't have a 180 profile tire, do skinnier tires pressure rise higher than wider tires?  Should heavier bikes use a higher cold pressure?  Forgive my lack of physics or engineering knowledge.

Thanks for any insight

[RaYzerman]

Pretty normal..... weight vs. tire pressure will affect.  Use 40/42 on that VFR.... or just play with it and you'll see the difference..... put your TPMS alarm higher, like 52, cuz it will go there on a scorching hot day.  You only need the lower limit anyway to give you early warning you're losing air.

[betoney]

1 hour ago, RaYzerman said:

Pretty normal..... weight vs. tire pressure will affect.  Use 40/42 on that VFR.... or just play with it and you'll see the difference..... put your TPMS alarm higher, like 52, cuz it will go there on a scorching hot day.  You only need the lower limit anyway to give you early warning you're losing air.

The high pressure alarm going off had me in a panic, Ive never had that happen on the smaller FJ09. 

I realize high speeds and hot days will cause the pressure to rise higher but higher than 48psi isn't out of the normal or dangerous?

I have heard that the difference between cold and "operating temperature" should be 10%, is this correct?  My reading was closer to a 25% rise.

[Heli ATP]

Dave Moss on Tire PSI

[betoney]

52 minutes ago, Heli ATP said:

Dave Moss on Tire PSI

A lot of good info in that video.  I have some testing to do. 👍🏻

[RaYzerman]

Do your own testing.  I don't see that tire manufacturers recommend anything but max cold pressures, almost always 42 psi.    I've had many bikes, and to be honest 36 psi front is handling like a dog, worse on heavier bikes, and the tires wear funny.  Better at 39/40 front and no loss of traction.  Race track will want lower because they want them real hot.  Not on the street.

All my rears are 42 psi, as most bike manufacturers recommend, but on a heavier bike (FJR, e.g.), add another 2 and again, no loss of traction, tires wear better and last a hair longer.

On hot days, a front at 40/41 psi cold can go up to 51/52 hot.  There is no 10% rule, but there is a pressure/temperature curve, I believe roughly for every 10 degrees approx. 1 psi rise.  It's not linear...

Edited April 9 by RaYzerman

[2and3cylinders]

Oy vey, another oil thread...

Experimentation is the only Way

Tire maker and model of course play a big part though.

I have a TPMS  and the cold hot disparity front/ rear is crazy, and relative not that accurate.  You must verify with a decent digital or even a good analog Mechanical giage.

[Ride365]

It's a fine line between the right contact profile, and too much air makes for a harsher ride, less contact, abnormal wear, and not enough air can be ill handling, abnormal wear and more sidewall flex. I "typically" run 35 front and 38 rear, anything more than that IMHO and experience, I don't care for how it rides/handles. Not riding on the same side/lane of road makes a difference in wear as well, as the road crown is different on both sides. I get extremely even wear on my tires, and of course I try to ride plenty of twisty roads regularly as well.  I do adjust per the temps outside like Dave suggests, and I have lost 22 pounds over the last year, so I weigh less now as well. 

Edited April 9 by Ride365

[2and3cylinders]

🤣if only 22 pounds

[2and3cylinders]

My gear would fit🫠

[Ride365]

2 hours ago, 2and3cylinders said:

🤣if only 22 pounds

I was 202, now I am at 175 "so I have lost 27 pounds".......52 years young and overall in the best shape I've been since a much younger man, Lifestyle changes can go a long way, in particular when doing it a bit at a time so the body adjusts naturally. My problem is the opposite of yours, my gear is hanging off me now. 😂

[Ride365]

Sorry to hear that my man, that is certainly a bad run of luck and you're dealing with it best you can......getting older aint for sissies. I hear about alot of serious cycling injuries both on and off pavement, IMHO it's much more dangerous than riding motorcycles. 

[2and3cylinders]

10-4!

Instant power + / -, brakes, suspension and most importantly,  LIGHTS!

I was actually wearing a Joe Rocket motorcycle jacket less the back armor, and it got shredded more than a bit.

My Bell Achera helmet PEPS bead Crush Cap was split in half right  between my eyes!

But at that time, in over 35 years of street riding, I'd never really been hurt except for my brain sloshing around in the ole skull as well, when I highsided my 61 BSA Rickman Matisse Gold Star within the first 6 months of street riding a 500 4stroke near Big Basin SP northeast of Santa Cruz in the San Bruno mountains.

As I may have previously mentioned, the sport of Judo, "the gentle way", is even worse than American football for CTE...

17 years of that makes every day Groundhog Day as SWMBO reminds me every day 

 

 

[betoney]

On 4/8/2024 at 2:20 PM, RaYzerman said:

Pretty normal..... weight vs. tire pressure will affect.  Use 40/42 on that VFR.... or just play with it and you'll see the difference..... put your TPMS alarm higher, like 52, cuz it will go there on a scorching hot day.  You only need the lower limit anyway to give you early warning you're losing air.

We have had several days at or close to 70F so I have been playing with air pressures on both bikes, you were correct the big VFR has no issues with 40F/42Rpsi starting point, after several hours of riding, twisty roads and highway at 70-75mph for over half an hour, the pressure rose to 44F/46R.

On my FJ I have always used 38psi in the rear and have experimented with everything from 34 - 38psi in the front, yesterday I tried 34 and didn't like the steering, it felt kind of like riding on grooved pavement or a grated bridge deck, this morning I raised it to 38 and the steering was much improved.

The Dave Moss video that @Heli ATP linked was extremely helpful to find what works for ME and MY type of riding.

Thanks again for the advice. 

[2and3cylinders]

I just yesterday them at 33 / 38 when I reinstalled my TPMS unit.

I never considered going higher than 36 in the front.

I have a friend runs what I set them at, not the same bike but comparable in terms of weight, a S1000SX, and he also has yeas of  racing  experience. 

So when it warms up, and I get out for a shakedown run, my first attempt to ride this year, I'll pay more attention.  Likely though I won't be pushing it. 

However, my season may end soon after it begins due to my  bod.

It always could be worse...