Tyre pressures

[S-Westerly]

Here's a question for the forum:-

 

Yesterday after picked up the bike and within a mile of the dealers my tyre monitoring system went into alarm because both my tyres were over pressure. I pulled into a layby let some air out and rode home without further problems. 

This morning with ambient temperature of 2 C, I checked my tyres again and both were quite low - 25 psi vs 36 psi for the front and 30 psi vs 41 psi for the rear. I put in air to the recommended pressures but I'll be interested to see what happens when I head north tomorrow.  

 

Without the TPMS I'd have had no idea of what was going on.

 

Question is what pressures should we inflate to when the ambient is low vs when it's high? 

 

All opinions will be listened to and probably ignored!

[JRH]

I always check and if necessary inflate to the recommended pressure prior to riding. This means pushing out of the garage and checking the TPMs. Then inflate or deflate as required. 
I’ve had the high warning in summer after a few miles riding just because the roads were hot and a high ambient whereas the garage was quite cool. 
 

[husoi]

I remember in 2019 while touring to Portugal I had the TMPS showing the correct pressure/temp until I crossed to France. 

Had to stop as the alarm went of showing  over 50psi instead of 36.

All depends on outside temp and riding speed plus weight you're carrying.

I noticed the front tyre won't increase pressure and temp as much as rear one.

I think this is because rear tyre does all the hard work and gets hot air from the engine while the front always gets fresh cooler air and doesn't have to cope with pushing the bike.

[Bender]

I just set them to what they are supposed to be before setting off, I don't have tpms so I'm alarm free

[S-Westerly]

When I didn't have TPMS once I checked it before riding I was happy. Now I have I can forsee myself getting unnecessarily fraught.

[Grumpy Old Git]

Never had TPMs

[Nick the wanderer]

Yeah I'm happy enough without, just check the pressures before going out and on cold tyres.

[Steve_M]

I’ll admit to not checking my tyre pressures every ride. I do have TPMS (that’s a four letter abbreviation from my days as a COBOL programmer so it takes me a moment to apply it to motorbikes) which has only flagged up a problem - a slow puncture - once in my 4 years of ownership. This includes last year’s tour with ambient temperatures ranging from 12° c (Alston Moor) up to 34°C (Troyes). 

[Yorky]

5 hours ago, S-Westerly said:

All opinions will be listened to and probably ignored!

[husoi]

Was a slow puncture that lead me to get the tmps.

Well worth the 30 quid I spend on it

[RideWithStyles]

Tpms

Edited May 15, 2024 by RideWithStyles

[curlylegend]

8 hours ago, Nick the wanderer said:

Yeah I'm happy enough without, just check the pressures before going out and on cold tyres.

Isn't that what motorcycle AND tyre manufacturer recommend ?

[Steve_M]

According to this article tyre pressures change by 0.19PSI per degree Celsius change.

 

Effect of temperature on tyre pressure

 

 

Edited January 14, 2024 by Steve_M

[Bender]

Air expands when heated so it has to increase tyre pressure, it's why some fancy things use nitrogen it has a much lower reaction to temp changes and doesn't drop pressure over time as much, most of what you breathe is nitrogen.

[keith1200rs]

2 minutes ago, Bender said:

Air expands when heated so it has to increase tyre pressure, it's why some fancy things use nitrogen it has a much lower reaction to temp changes and doesn't drop pressure over time as much, most of what you breathe is nitrogen.

I think the reason for using pure nitrogen is not to do with pressure changes with temperature- all gases are the same and governed by Boyles law,as I recall.

[Tinkicker]

First world problems...

 

I doubt any of the millions of riders in Saigon are wondering if their tyre pressures have changed since they pumped them up.  

 

The handbook on any vehicle gives the answer you seek.  " check and adjust tyre pressures with cold tyres". 

 

Job done.

 

 

Edited January 14, 2024 by Tinkicker

[Nick the wanderer]

10 hours ago, RideWithStyles said:

a warm garage of 18*c or more

I had a dream about a warm garage last night..

[husoi]

23 minutes ago, Tinkicker said:

First world problems...

 

I doubt any of the millions of riders in Saigon are wondering if their tyre pressures have changed since they pumped them up.  

 

The handbook on any vehicle gives the answer you seek.  " check and adjust tyre pressures with cold tyres". 

 

Job done.

 

 

Don't know about Saigon.

In Indonesia is common to see someone with a small compressor ready to check the pressure and add some air to the tyres of any biker passing by.

Same with 1.5l plastic bottles of petrol on remote areas.

[Bender]

28 minutes ago, keith1200rs said:

I think the reason for using pure nitrogen is not to do with pressure changes with temperature- all gases are the same and governed by Boyles law,as I recall.

Normal air has oxygen and moisture and a few other glasses and expands much more over same temperature range, that's  why nitrogen is used in race applications it alters much less with temperature change than just air. I didn't say it's immune to expansion.

 

 

[keith1200rs]

The reason for using dry nitrogen is the absence of moisture and larger molecules than oxygen so slower leakage. Moisure will boil altering the pressure and also potentially increase corrosion. 

[RideWithStyles]

Prev

Edited May 15, 2024 by RideWithStyles

[Bender]

1 hour ago, keith1200rs said:

The reason for using dry nitrogen is the absence of moisture and larger molecules than oxygen so slower leakage. Moisure will boil altering the pressure and also potentially increase corrosion. 

I don't think long term leakage is a concern to a race team, tyres will be toast in one race.

[RideWithStyles]

Or

Edited May 15, 2024 by RideWithStyles

[Tinkicker]

https://monroeaerospace.com/blog/why-nitrogen-is-used-to-fill-airplane-tires/#:~:text=Since the late 1980s%2C the,consistent pressure and is nonflammable.

[S-Westerly]

Jesus. I'm not putting nitrogen in my tyres. My bike doesn't have a nice warm garage to live in so the air it gets is put in at ambient plus the slight rise in temperature due to compression.

I checked tyres yesterday and they were quite low so pumped them up to recommended pressure. Turns out gauge on pump is reading high as when I started up this morning the TPMS had a hissy fit as the pressures were way too high and I had just backed out. Got a separate gauge and both tyres were about 20% over recommended cold pressures. Adjusted them accordingly and rode 297 miles to Northumberland without any further issues. Once they warmed up they were consistent and recorded as 39 psi front (36 psi cold) and 46 psi rear (41 psi cold).