Tire Pressure Loss After Five Months

[The Critic]

I had a set of Cooper CS4 tires installed onto my friend's Prius back in October.

Since then, I have not checked the tire pressure and today the TPMS light came on.

When the tires were purchased, I set the pressures to 40 psi cold in the front and 38 psi cold in the rear. Also, at the time of the tire purchase EVERY TPMS sensor was rebuilt with a new o-ring, valve stem, nut and cap.

Here are the readings as of today:

LF: 32 psi
RF: 36 psi
LR: 34 psi
RR: 34 psi

So, there was a 4 psi loss per tire after five months except for the oddball LF tire. That equates to about a 1psi loss per month.

How much air do your tires loose on a monthly basis?

 

[Carbon]

You might want to check that left front for a nail.

 

[crinkles]

i found at most 5 kPa or 1/2 a PSI or so over two weeks... so 1 PSI a month. steel rims, dunlop 94V tyres

 

[JustinH]

Here in NY, the tires will lose about 5 psi during the winter time, and every spring, I have to let a little bit of air out of the tires.

Refill the tires again cold, and have him check after a week. That front left sounds like it has a leak.

Were you using the same tire guage?

 

[Shannow]

45f temperature difference is worth about 4psi, as well.

 

[Papa Bear]

You let those new tires run until the TMPS light came on ??!! What's wrong with you ?....

 

[Quattro Pete]

Originally Posted By: Shannow
45f temperature difference is worth about 4psi, as well.

Yup.

Critic, what was the ambient temp when you measured it 5 months ago and what was it now?

 

[Craig in Canada]

You need to check your pressure far more often than twice a year. Seasonal variations in average temperature will have your true pressures all over the place affecting handling, safety, tire wear and fuel economy. (OK, I suppose CA might be the ONE place this isn't as large a concern - but do you wait for the oil idiot light to come on to check it?).

Generally all tires will lose some air, and valves can be leaky as well (this happened to me on a set of snows - slow leak from the valve).

 

[kkreit01]

Check at minimum 1/mo. Use the recommended PSI stamped on your door frame. It's very easy to lose/gain several PSI between Fall-Winter-Spring.

 

[cchase]

My car loses a few pounds a month.

My truck almost never loses any air for some reason. I run winter and summer tires on it, I don't think I've added air in 2 years to the summer tires.

I have a bicycle with tubeless tires that I have never added air to. I run it at about 28 psi and they have been at 28 psi for 3 years....

 

[The Critic]

Originally Posted By: Quattro Pete
Originally Posted By: Shannow
45f temperature difference is worth about 4psi, as well.

Yup.

Critic, what was the ambient temp when you measured it 5 months ago and what was it now?


When the tires were installed, they were installed at 8-9pm at night so it was about 50F out. It was about the same temperature last night.

The OEM tire spec is 35F/33R, so with the exception of the LF tires, they are still above spec.

 

[HTSS_TR]

All tires lost some PSI's overtime, on the average most tires lost about 1 PSI a month that why I check my tires once a month, and to be sure that no tire will never at below recommended pressure I have all tires at 2-6 PSI above recommendation for all cars.

 

[eljefino]

Remember this isn't OPs car so he isn't the neglectful one.

 

[Shannow]

That makes the information and the question totally ambiguous then.
And the galactic alignment later supplied somewhat superfluous.

 

[The Critic]

Originally Posted By: Shannow
That makes the information and the question totally ambiguous then.
And the galactic alignment later supplied somewhat superfluous.

 

[daves87rs]

About 1 a month sounds right.

 

[rshaw125]

Refill with nitrogen.

 

[Shannow]

Or at least 78% nitrogen like I do.

 

[Papa Bear]

 

[Spector]

remember for every 10 degree change in outdoor temperature the tire pressure changes 1PSI. so if the temp goes from 50degrees to 40 the tire pressure will drop 1 PSI. In addition, as noted, tires lose pressure at varying rates over the course of a month.

Nitrogen filled tires supposedly lose less air over time