V70: General V70 Tyre Pressures.

[richardt1994]

Hello All,

I am new to the forum having just purchased a 58 plate V70 2.4D SE Lux Geartronic. The last Volvo I had was a V40 15 years ago so my Volvo knowledge is a bit hazy :-)

My question is regarding tyre pressure stability over time. On my previous car (Audi A6) the pressures were 29 PSI and they would loose very little pressure over time, about 1 or 2 PSI in 2 months. I generally check the tyres every 2 weeks.

On my V70 the book seems to recommend 38 PSI. (ECO Pressure?) The tyres are all Goodyear 225/50/R17 with > 5mm of tread on them and look in good condition. The issue is that having inflated them all to 38 PSI 2 weeks ago when I got the car they are all now at 34/35 PSI. So they have lost 3/4 PSI in 2 weeks. If it was just one tyre then I would obviously suspect slow puncture or dodgy valve, but this is all 4 of them! Is this normal for the V70? All I can suspect is that as they run at a relatively high pressure (38 PSI) then valve losses etc are greater than at lower pressures as with my old Audi. I have done about 1000 miles of mixed driving in that 2 weeks.

Does anyone have any comments or suggestions. If what I am seeing is normal for the V70 then I will just have to keep a closer eye on tyre pressures.

Many thanks,

Richard.

[oragex]

Indeed, at 38psi you will safe a little bit in diesel, perhaps 1-3%?

To industry standard, 38psi is rather high. 32-35 psi is more like the average.

As for deflating tires, I think it's because of the tire quality and/or tire installation (some put some sort of coat before installing the tire) or wheel corrosion. Given 38 psi is rather high, it is possible the tire can't keep this pressure (but usually it should keep it). Of course, there is also the temperature factor, if the weather is cooling, the pressure will drop.

All in all, the recommended pressure is not something absolute. You are free to inflate to your desired pressure - usually it will affect the comfort and the mileage, as long as it's not too low or too high which will cause uneven tire wear.

[GrantA]

As you have already found out your recommended tyre pressures are in your hand book, they are also on the "B" pillar driver's side. It is recommended that tyre pressures are checked "cold" i.e. before they warm up after the car has been driven for a while. With the present weather we have been having 20+C some days and down to 12C the next the pressure in all the tyres will drop accordingly and likewise rise once the sun has come out for a few hours the pressures will increase. Tyre pressure will also drop over time and may depend on the state of the wheels as well as the state of the tyres. For a large heavy car like a Volvo V70 estate 38psi is quite normal. Personally I would keep the tyres within the manufacturer's recommended limits, a lot of research, time and money goes into finding the optimum tyre pressures during the development stages of all vehicles so I would stick with what the experts say.

The only way to have a tyre pressure that remains "almost" constant with very little change day to day, even after the car has been driven hard, is to fill the tyres with nitrogen not air. This might help to explain: http://www.theaa.com/motoring_advice...-nitrogen.html and here to explain further http://www.racq.com.au/cars-and-driv...ogen-for-tyres

[Guy XC70]

Originally Posted by oragex

Indeed, at 38psi you will safe a little bit in diesel, perhaps 1-3%?

To industry standard, 38psi is rather high. 32-35 psi is more like the average.

As for deflating tires, I think it's because of the tire quality and/or tire installation (some put some sort of coat before installing the tire) or wheel corrosion. Given 38 psi is rather high, it is possible the tire can't keep this pressure (but usually it should keep it). Of course, there is also the temperature factor, if the weather is cooling, the pressure will drop.

All in all, the recommended pressure is not something absolute. You are free to inflate to your desired pressure - usually it will affect theŷ comfort and the mileage, as long as it's not too low or too high which will cause uneven tire wear.

I found a non-trivial mpg improvement, perhaps 5%, running my series 2 V70 at 38psi, with no noticeable decrease in comfort. I think you are on the money with temperature given that all tyres are affected. I'd lose less than 1psi per month at 38psi, driving between 1,000 and 2,000 miles.

[Mr R Design]

My two pence worth from experience is:

1) I had a similar problem, no punctures or leaky valves but a couple of the tyres gradually kept losing pressure. The tyres were taken off and the rims and tyres cleaned and refitted. No problems since.

2) I found 38psi a touch to high and the car felt like it was bouncing a bit. 36psi (when cold) for me feels nice and I get even wear. I am on 245/40/18 97Y if it makes any difference.

[tt82]

I tried 38psi but have since dropped it to 35-36psi. I reckon I lose about 1psi a month doing about 1,500 miles.

As Mr R Design has stated, the problem is most likely to be a poor seal between tyre and rim.

[I-S]

The "problem" is most likely to be that the weather has just turned colder in the past couple of weeks. If you inflated them to 38psi exactly at 20C, then at 10C they will be 36.7psi. Air is heated up when you compress it, so if the ambient was 20C when you filled the tyres, chances are that the air temp in the tyres was greater than 20 (especially if the sun was shining on them).

This morning it was rather chill up here, so it's entirely possible that the tyres are reaching down to 5C overnight now.

If the tyres were filled to 38psi at 25C then they will be 35.4psi at 5C.

Tyres do also just leak a certain amount over time, and i tend to find especially so after first inflation if they've not been done for a while. Certainly in 1000 miles I'd expect a bit of loss, so combined with the temperature variation I think it's normal and nothing to worry about.

Always inflate tyres from cold - when the car has been standing, not after driving.

[PEGE63]

Originally Posted by Mr R Design

My two pence worth from experience is:

1) I had a similar problem, no punctures or leaky valves but a couple of the tyres gradually kept losing pressure. The tyres were taken off and the rims and tyres cleaned and refitted. No problems since.

2) I found 38psi a touch to high and the car felt like it was bouncing a bit. 36psi (when cold) for me feels nice and I get even wear. I am on 245/40/18 97Y if it makes any difference.

set mine at 37, running stable at that, tyres quite new, do adjust them for winter summer according to ambient temp, always check when cold (2 miles to garage...)

[richardt1994]

Hello All,

Thanks very much for the observations and words of wisdom!

I am tending to thinking that it is temperature. If I remember correctly it was very sunny > 20C when I collected the car and set the initial pressures but was quite early in the morning and < 10C when I checked them. I am going to check them weekly and record the ambient temperature for a few weeks to see what I get. (A bit anal I know, but the tyres in my old Audi never seemed to vary that much with temperature but they were at a lot lower pressure and I like to try and understand the "temperament" of a new car)

All in all very pleased with the V70, still getting used to where the switches are, the handbrake is a bit of a pain. Push to put on still seems counter intuitive to me but there you go...

Once again, thanks for everyone's kind advice.

Have fun,

Richard.

[Model flyer]

Hi I ran My V70 fitted with Pirelli tyres inflated to 34 psi . They developed a concave look as the center of the tread wore down quicker than the rest . I now run them at 32 psi this gives a more comfortable ride and the tyres seem to wear normally now .I now only up the pressure If I'm loading up or towing the Caravan. The change in pressure you notice is probably as said due to the change in ambient temperature . Do keep a check on them as I also had two tyres that kept deflating on my previous car due to rims that hadn't been cleaned when new tyres were fitted.