I just had my winter tyres fitted (Dunlop SP winter sports) and the engineer who did the job recommended they be run at 2.5 and not the 2.2 bars listed in the manual. He said snow tyres work better at higher pressures, anyone care to comment?
M & S rated tyre pressures.
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It would be nice if we had more info.
For example, Year, make and model of your vehicle. What tire size are we talking about? Is it the same as the tire size listed in the manual?
And - yes, winter tires work just a bit better at higher pressures - smaller footprint - and 0.3 bar (4 psi) fits into my picture nicely.
For example, Year, make and model of your vehicle. What tire size are we talking about? Is it the same as the tire size listed in the manual?
And - yes, winter tires work just a bit better at higher pressures - smaller footprint - and 0.3 bar (4 psi) fits into my picture nicely.
The tyres in question are 185/65/15 Dunlop Winter Sport SP's fitted to a Volvo 1.9D.
The owners handbook gives only one set of tyre pressures for different weights varying from 2.1 to 2.3, so the engineer setting them at 2.5 has used a figure about 10% higher than anything in the book.
I had a look through Google but although there are quite a few articles saying that summer and winter pressures should be the same, there are some saying run higher and some saying lower pressure in winter.
The owners handbook gives only one set of tyre pressures for different weights varying from 2.1 to 2.3, so the engineer setting them at 2.5 has used a figure about 10% higher than anything in the book.
I had a look through Google but although there are quite a few articles saying that summer and winter pressures should be the same, there are some saying run higher and some saying lower pressure in winter.
".....Sometimes it does take a rocket scientist to design a tire. Dr. Burkhard Wies, vice president of tire line development worldwide for Continental AG, helped develop the new General Altimax Arctic. His credentials include an undergraduate degree in physics and a PhD in mechanical engineering; his thesis relied heavily on combustion research.
Wies knows everything about the tire, which is made with a higher percentage of natural rubber than many of its competitors, thanks to extensive testing. Some of the following tests were performed by an independent third party, so he is confident that the tire performs as advertised...............................................................................................
............. Pressure. "Yes, we reduced pressure slightly -- not significantly, maybe 20%. Grip normally increases as the pressure decreases. It can, of course, destroy mileage......................................................................."
http://m.moderntiredealer.com/Article/?id=1372
Wies knows everything about the tire, which is made with a higher percentage of natural rubber than many of its competitors, thanks to extensive testing. Some of the following tests were performed by an independent third party, so he is confident that the tire performs as advertised...............................................................................................
............. Pressure. "Yes, we reduced pressure slightly -- not significantly, maybe 20%. Grip normally increases as the pressure decreases. It can, of course, destroy mileage......................................................................."
http://m.moderntiredealer.com/Article/?id=1372
From a Q&A in 2002 with Dr. Burkhard Wies:
".................Question: Are there any other improvements [of winter tires] which could be achieved through different means?
Answer: If the tyre pressure could be adapted to the driving and load conditions of the vehicle, improvements could be made to traction and comfort, without adversely affecting the service life of the tyre. Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition.........."
Continental Q&A
".................Question: Are there any other improvements [of winter tires] which could be achieved through different means?
Answer: If the tyre pressure could be adapted to the driving and load conditions of the vehicle, improvements could be made to traction and comfort, without adversely affecting the service life of the tyre. Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition.........."
Continental Q&A
OK, so I think that perhaps a higher pressure is not such a good idea, so I will go back to my summer 2.2 setting until I read something more conclusive.
But higher pressures have their benefits, as Dr. Wies points out:
"...........Substantial progress could also be made in handling, aquaplaning protection and braking in the wet if the tyre pressure could be individually increased from 2.5 to 3.5. This would enable braking distances to be reduced by 5 per cent, whilst handling could be improved by 15 per cent and aquaplaning protection by 20 per cent...... "
"...........Substantial progress could also be made in handling, aquaplaning protection and braking in the wet if the tyre pressure could be individually increased from 2.5 to 3.5. This would enable braking distances to be reduced by 5 per cent, whilst handling could be improved by 15 per cent and aquaplaning protection by 20 per cent...... "
Most tyre/car combos have there sweet spot. Try and adjust accordingly. If you are not the principal operator, ongoing adjustments can be difficult to impossible to gauge. My experience has been a falloff of traction above 2.2. Best traction in bad conditions will be somewhere in the 1.9>2.2 range, I would hazard.
My Volvo has the usual high speed load and normal speed load pressures, but also has an higher pressure the name ECO, which is higher than the others.
This pressure made the car quite harsh on my normal tyres but this characteristic was not as evident with my winters, which are closely related to your Dunlops, mine are Goodyear UltraGrip 8s.
From this experience I think it shows that my winter tyres at least are much softer in compound and probably sidewall rigidity. So it would make sense that they would drive a little better with higher pressures.
This pressure made the car quite harsh on my normal tyres but this characteristic was not as evident with my winters, which are closely related to your Dunlops, mine are Goodyear UltraGrip 8s.
From this experience I think it shows that my winter tyres at least are much softer in compound and probably sidewall rigidity. So it would make sense that they would drive a little better with higher pressures.
Originally Posted By: SubLGT
From a Q&A in 2002 with Dr. Burkhard Wies:
".................Question: Are there any other improvements [of winter tires] which could be achieved through different means?
Answer: If the tyre pressure could be adapted to the driving and load conditions of the vehicle, improvements could be made to traction and comfort, without adversely affecting the service life of the tyre. Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition.........."
Continental Q&A
Be careful here. If you can get a tire to contact the road surface, the grip increases dramatically - and the way to do that is to reduce the size of the footprint = higher pressure.
- BUT - if you CAN'T reach the pavement, then it is true that grip on snow is better with lower pressure = larger footprint. I am sure that is what Dr. Wies meant - after all the discussion was snow traction and that is how engineers think. (Trust me, I know how engineers think!!)
What we used to do is use 5 psi more, then if we got stuck and couldn't get out, then lower the pressure to get us unstuck. Then reinflate once back in the barn.
From a Q&A in 2002 with Dr. Burkhard Wies:
".................Question: Are there any other improvements [of winter tires] which could be achieved through different means?
Answer: If the tyre pressure could be adapted to the driving and load conditions of the vehicle, improvements could be made to traction and comfort, without adversely affecting the service life of the tyre. Particularly with traction in snow and especially on loose ground, if we could reduce the tyre pressure from 2.5 to 1.5 bar, spectacular improvements of up to 30% could be made. This would however have negative effects when braking on dry roads and in handling, so any adjustments to the tyre pressure always have to be in the correct ratio to the driving condition.........."
Continental Q&A
Be careful here. If you can get a tire to contact the road surface, the grip increases dramatically - and the way to do that is to reduce the size of the footprint = higher pressure.
- BUT - if you CAN'T reach the pavement, then it is true that grip on snow is better with lower pressure = larger footprint. I am sure that is what Dr. Wies meant - after all the discussion was snow traction and that is how engineers think. (Trust me, I know how engineers think!!)
What we used to do is use 5 psi more, then if we got stuck and couldn't get out, then lower the pressure to get us unstuck. Then reinflate once back in the barn.
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