R4 PHEV.. Tyre pressures?

[Nick72]

Got a baring today. Nearside front tyre was 2.0 bar. Opposite was 2.1 and the rears also 2.1. What should they be?

 

Bit odd because it was in for service last month so I'd have assumed that topping up the tyres was part of a service?

 

I've got a 12v pump I keep under the rear floor panel so easily sorted but just curious on tyre pressure and service. It was however 0C this AM and now 9C and the warning has disappeared.

 

Ta

[ernieb]

2.3 bar 33psi. The cold weather would have reduced the pressure causing the alarm. Best to set the temperature when all sides of the car are evenly naturally heated say 15/20oC. But otherwise compensate for a lower temperature. Reset TPMS.
I never trust the garage with tyre pressures, they have been all over the place in my experience.

[Nick72]

8 minutes ago, ernieb said:

2.3 bar 33psi. The cold weather would have reduced the pressure causing the alarm. Best to set the temperature when all sides of the car are evenly naturally heated say 15/20oC. But otherwise compensate for a lower temperature. Reset TPMS.
I never trust the garage with tyre pressures, they have been all over the place in my experience.

Cheers Ernie. Sounds like I need to top them up tomorrow and do the garage's job for them. 🤷

[Cyker]

I usually have to top them up when the weather gets cold - Colder ambient temps = tyre pressures go down; It's just physics. If it was warmer when your service was done they would have adjusted the temps for that, but it's dropped like 7C or so down here and that also gives a noticeable drop of tyre pressures.

Ironically I have the opposite problem - My dealer are very on the ball with checking and adjusting the tyre pressures every service, and I keep having to tell them to not touch them, as they keep setting them to the pressures listed on the car's B-pillar, which would be correct if I still had the 17" rims, but are far too low for the 15's!!!  

I don't mean to be sound preachy but, TBH, things like tyre pressures, oil level, coolant level, screen wash level etc. are all things that should be checked and adjusted as needed regularly by car owners all year round. I must admit I've slacked off the tyre pressures since the TPMS system literally tells me the tyre pressures in real time, so I can see when they need adjusting (Keeping them at optimal levels is partly why I can maintain such good mpg!  ), but the other stuff I still check every fortnight, or every month minimum.

 

[Oscarmax]

I set my tyre pressures up to 35 psi about 2 weeks ago yesterday at 4 degrees C they were showing 33 psi, after a few miles they warmer up to 34 psi.

[Nick72]

19 hours ago, Cyker said:

I usually have to top them up when the weather gets cold - Colder ambient temps = tyre pressures go down; It's just physics. If it was warmer when your service was done they would have adjusted the temps for that, but it's dropped like 7C or so down here and that also gives a noticeable drop of tyre pressures.

Ironically I have the opposite problem - My dealer are very on the ball with checking and adjusting the tyre pressures every service, and I keep having to tell them to not touch them, as they keep setting them to the pressures listed on the car's B-pillar, which would be correct if I still had the 17" rims, but are far too low for the 15's!!!  

I don't mean to be sound preachy but, TBH, things like tyre pressures, oil level, coolant level, screen wash level etc. are all things that should be checked and adjusted as needed regularly by car owners all year round. I must admit I've slacked off the tyre pressures since the TPMS system literally tells me the tyre pressures in real time, so I can see when they need adjusting (Keeping them at optimal levels is partly why I can maintain such good mpg!  ), but the other stuff I still check every fortnight, or every month minimum.

 

Agreed but it was about 10C when the service was done. 10C to 0C doesn't result in drop from 2.3bar (what they should have topped the tyres up to) to 2.0bar (what the warning said). That's a 13% drop. Whereas a drop from 283K (10C) to 273K (0C) is determined by PV = nRT or P = nRT / V. Since the V is constant (the constraint of the tyre geometry at higher pressures) and n and R fixed here. Then, the pressure drop in percentage is actually 100 X 10K / 283K = 3.5%. That's just the real physics.

So whilst I accept user maintenance (no problems as a engineer of things more advanced than space shuttles) the clear gripe I have is that the dealer clearly didn't top up the tyres and in which case what are you actually paying for beyond changing the oil and filter (which is a 30 minute job I could do myself)? I don't pay for servicing or anything out of my pocket as it's a company car but it's the principle here. 😉 In the same way on last year's service which said complementary valet. Which wasn't done.

 

[ernieb]

The problem is they may have ‘adjusted’ the tyre pressure but get them wrong. The first Toyota dealership I used has very poor access and the entrance to the service bays exceptionally awkward. When they did the service I found the car useless to dive, one side very high the other low. I concluded that they had the car in the hot sun on the high side and deep shadow, under a canopy, on the other, once I reset the tyres early the following morning, the drive was perfect. I figure having the tyres balanced is very important even if the absolute pressure may be off slightly.

[Nick72]

41 minutes ago, ernieb said:

The problem is they may have ‘adjusted’ the tyre pressure but get them wrong. The first Toyota dealership I used has very poor access and the entrance to the service bays exceptionally awkward. When they did the service I found the car useless to dive, one side very high the other low. I concluded that they had the car in the hot sun on the high side and deep shadow, under a canopy, on the other, once I reset the tyres early the following morning, the drive was perfect. I figure having the tyres balanced is very important even if the absolute pressure may be off slightly.

That's a good point. Looks like another unnecessary job to make up for dealer incompetence 🤦😥

[TonyHSD]

That’s right , even a specialist tyre fitters aren’t getting tyre pressures right. Only the car owner can do that at home with proper gauge and simple air compressor. Best time to do this is in the morning before driving off or the sun sees the car, these two off sets the numbers. 
Tyre pressures will play up or down, but mostly down with everyday temperatures fluctuations. Less you drive more air you lose.
Monthly checks aren’t enough imo. I do check once a week or every two weeks , it’s super easy and only takes 10 min max all 4 corners.
The benefits are huge , low tyre noise , greater comfort and safety plus a set of tyres last me easily over 60k miles and more 👍