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[cem_devecioglu]

Braking Distance (in feet) provided by Goodyear
 Wet Stopping Distance (0.050" water depth)

Surface Speed 17 psi 25 psi 29 psi 35 psi Macadam 25 mph 32.4 30.8 29 27.4 Macadam 45 mph 107.6 101 100.8 98.6 Concrete 25 mph 47.4 48.2 48.2 48 Concrete 45 mph 182.6 167.2 167.4 163.6

[cem_devecioglu]

Braking Distance (in feet) from NHTSA testing
 Stopping Distance from 60 mph

Surface 15 psi 20 psi 25 psi 30 psi 35 psi Wet Concrete 148.8 147.5 145.9 144.3 146.5 Dry Concrete 142.0 143.0 140.5 140.4 139.8 Wet Asphalt 158.5 158.6 162.6 161.2 158.0 Dry Asphalt 144.0 143.9 146.5 148.2 144.0

[cem_devecioglu]

generally I check tire pressures monthly in summer..

yesterday tire pressures were low for both cars (nearly 5-6 psi lower than normal) seems in winter I need frequent checks..

[cem_devecioglu]

here is the link

http://www.nhtsa.gov/cars/rules/rulings/tirepressure/LTPW3.html

[TheBoy]

I tend to run my Omega saloons at 32mpg all year round, dropping slightly if we have snow.

Up to 38/45 if fully laden.

[kcl]

I wonder how much pressure you should put to tyres for optimum brake distance? It seems in these above tables that higher pressure equals to shorter distance but where is the limit?

[TheBoy]

I wonder how much pressure you should put to tyres for optimum brake distance? It seems in these above tables that higher pressure equals to shorter distance but where is the limit?

I'd say not far off the manufacturer's settings TBH.  These generic tests are not specific enough to be useful.  As we keep saying here, each model of car uses its tyres differently. For pure stopping, as much rubber firmly planted (so sidewalls come into it) on road as possible. Which may not be the ideal for handling.

Overinflated from manufacturer's settings, only centre has firm contact, underinflated, only the edges due to sidewall rigidity.

[kcl]

I wonder how much pressure you should put to tyres for optimum brake distance? It seems in these above tables that higher pressure equals to shorter distance but where is the limit?

I'd say not far off the manufacturer's settings TBH.  These generic tests are not specific enough to be useful.  As we keep saying here, each model of car uses its tyres differently. For pure stopping, as much rubber firmly planted (so sidewalls come into it) on road as possible. Which may not be the ideal for handling.

Overinflated from manufacturer's settings, only centre has firm contact, underinflated, only the edges due to sidewall rigidity.

That is not quite true! It used to be so when tyres were not steel belted radials. But nowadays the steel belts are so rigid that overinflating (and we are now talking about some reasonable pressures, let's say less than 4 bar) will not cause any significant excessive wear, pressure just is not enough to disform the tyre. More likely cause for mid-tyre wear is acceleration, in FWD cars the fronts wear from center, in RWD rear tyres. This has been confirmed by Nokian Tyres when it was asked because we had some debate about this issue. Under inflation is an issue causing the tyre to "disform" when cornering etc resulting in wear on edges. The side walls are not as rigid as the "driving surface" of tyres.

I also know that tyres are tested with 12 bar inflation.

[Kevin Wood]

Under heavy braking, front wheels are much more heavily loaded and rears less so due to forward weight transfer, so I wouldn't mind betting that more pressure in the front and less in the rear would improve things - if stopping is your only criteria.

What those figures say to me, though, is that it doesn't make a significant difference.

[sticka_v8_init]

Under heavy braking, front wheels are much more heavily loaded and rears less so due to forward weight transfer, so I wouldn't mind betting that more pressure in the front and less in the rear would improve things - if stopping is your only criteria.

What those figures say to me, though, is that it doesn't make a significant difference.

+1 

[kcl]

Under heavy braking, front wheels are much more heavily loaded and rears less so due to forward weight transfer, so I wouldn't mind betting that more pressure in the front and less in the rear would improve things - if stopping is your only criteria.

What those figures say to me, though, is that it doesn't make a significant difference.

Agreed, not any significant difference but still, a few feet difference will cause a huge change in possible collision speed as we know.

[cem_devecioglu]

I wonder how much pressure you should put to tyres for optimum brake distance? It seems in these above tables that higher pressure equals to shorter distance but where is the limit?

I'd say not far off the manufacturer's settings TBH.  These generic tests are not specific enough to be useful.  As we keep saying here, each model of car uses its tyres differently. For pure stopping, as much rubber firmly planted (so sidewalls come into it) on road as possible. Which may not be the ideal for handling.

Overinflated from manufacturer's settings, only centre has firm contact, underinflated, only the edges due to sidewall rigidity.

definitely..

[cem_devecioglu]

I specifically searched for that subject, as most of us dont measure pressures frequently except the lucky members that have already pressure sensors in their other brand cars..

I really discovered that (in the hardway) 3 factors effect braking distance(except the tire itself)  (although I cant measure) tire pressure, suspension system and tire surface dirty with oils ..yes oils.. the roads that we use daily are not that clean.. generally covered with diesel spillage, and oil dropping from other cars, trucks.. so from time to time I wash them with detergents (although detergents harden them).. especially the surface of mechanic repair shops  and the parking area in front of them unbelievably dirty and oily

so briefly dont blame your old tires quickly.. wash them with detergents, arrange their pressures and renew your front suspension system.. it will make a difference..
 

[hotel21]

That is not quite true! It used to be so when tyres were not steel belted radials. But nowadays the steel belts are so rigid that overinflating (and we are now talking about some reasonable pressures, let's say less than 4 bar) will not cause any significant excessive wear, pressure just is not enough to disform the tyre. More likely cause for mid-tyre wear is acceleration, in FWD cars the fronts wear from center, in RWD rear tyres. This has been confirmed by Nokian Tyres when it was asked because we had some debate about this issue. Under inflation is an issue causing the tyre to "disform" when cornering etc resulting in wear on edges. The side walls are not as rigid as the "driving surface" of tyres.

I also know that tyres are tested with 12 bar inflation.

I disagree.  Even running with full load pressures on an unloaded car causes inappropriate wear to the tyres.  Admittedly, requires a good few hundred miles to manifest itself but as sure as eggs were made to be broken, running with a tyre overinflated (and I also mean less than 4 bar) will shag a good tyre right down the middle.

By the same token, running a tyre 10 psi less than recommended will shag the outer edges in quick order.

No table of facts to refer to, just a good number of years experience running professional fingers over a tyres surface.... 

[feeutfo]

It's always wise to check pressures weekly IMO. Can save a whole lot of grief if a low tyre is spotted early. A WHOLE lot of grief... And not just under braking either.

I see almost as many under inflated tyres just by visually looking at other cars as I do wonky headlights. It's rife. And dangerous. Although those that neglect their cars also seem to generally be unaware of a cars capabilitys, which is probably just as well tbh.

Pressures are vital to a tyres performance. Depending on the tyre a few psi difference can be felt quite easily, and a few psi can be lost or gained purely on a change in temperature, ESP this time of year with generally mild weather with the odd frost, 4 or 5 psi differance is not uncommon IME. The car can feel very different then...  IME.