Tyre pressure too high?

[Bear63 Senior Member Find all posts View Profile Close Bear63]

Is that all of them Matt?

[matt150 Avid PP Poster! Find all posts View Profile Close matt150]

Is that all of them Matt?

Basically yes.

[Bear63 Senior Member Find all posts View Profile Close Bear63]

Yeah well definitely under inflated for your vehicle then , bump them up 2 psi it may be all they need

[matt150 Avid PP Poster! Find all posts View Profile Close matt150]

Yeah well definitely under inflated for your vehicle then , bump them up 2 psi it may be all they need

My thoughts also. I will give it a try.

[wazafi Junior Member Find all posts View Profile Close wazafi]

Did a drive at Preston Beach with tyres at 21psi last week.

Decide to bring down from the pressure set by dealership (38psi) to 32psi.
Might not be as efficient or may bring about more wear, but definitely better in terms of driving comfort.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

Wazafi comfort and wear aside, low tyre pressures stuff up on road handling in a big way.

I did an advanced driving course where we had to avoid obstacles, and drive fast through cones and around a track. With low tyre pressures it was impossible to avoid obstacles, brake as quickly or get through the cones. Biggest surprise was that low pressures made it impossible to stop quickly in the wet.

So you're giving up safety, tyre wear and handling for comfort. A big trade off.

[gxllouie Member Find all posts View Profile Close gxllouie]

Wazafi comfort and wear aside, low tyre pressures stuff up on road handling in a big way.

I did an advanced driving course where we had to avoid obstacles, and drive fast through cones and around a track. With low tyre pressures it was impossible to avoid obstacles, brake as quickly or get through the cones. Biggest surprise was that low pressures made it impossible to stop quickly in the wet.

So you're giving up safety, tyre wear and handling for comfort. A big trade off.

also, the way a tyre flexes under braking, it is better to be overinflated.

under braking, effectively the outer edges of the tyre flex downwards towards the ground and the middle flexes upwards away from the ground. if the tyre is under inflated, only the outer edges of the tyre will make contact with the ground. if the tyre is overinflated, the edges will come down, but more of the tyre (in the middle) will remain in contact with the road.

i also learnt this from a defensive driving course where they showed us a cross section of tyre and how it behaves.

this diagram i got through google search shows how the tyre contact the ground under normal driving:



so based on what i said above in conjunction with the image - under braking, the overinflated tyres edges would move towards the ground and create more contact than the image shows. underinflated tyres would do the same and provide even less contact thatn the image shows.

louie

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

Louie, that's exactly how it was explained to me. It was still amazing to actually experience the increased brake distance with low tyre pressures on wet roads. The old school approach used to be to lower pressures in wet conditions which has the exact opposite effect to what you would expect.

[Prone Member Find all posts View Profile Close Prone]

Krypto and gxllouie,

Likewise. It was explained and demonstrated to me as you both say. Also if you think about it over inflation will keep the tread grooves open whereas under inflation will allow the tread grooves to pinch together and close up, giving less drainage for water under the tyre.
After being told this I noticed many black skid marks on the road with two black streaks about 100mm apart for each tyre, indicating low pressure in the tyres that allowed the centre of the tyre to loose contact with the road with only the outer edges of the tyres leaving the marks.

Prone

[matt150 Avid PP Poster! Find all posts View Profile Close matt150]

My thoughts also. I will give it a try.

All reset to 41psi cold.

[wazafi Junior Member Find all posts View Profile Close wazafi]

Hmm, will bring it up a bit when return to Perth to the point where comfort is not too bad.

Checked with my mates driving the Prados (120)..... both seems to set at 210kPa (as per on the door)

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

Wazafi, sounds like your travelling. When travelling at speed tyres work a lot harder and get a lot hotter. Obviously it's your choice what you do but you should be aware that running 30psi (cold) or less on the highway is asking for trouble especially in hot weather. It actually matters less around town.

[D4Dazz Member Find all posts View Profile Close D4Dazz]

I have Cooper STs on my Mitz Challenger, have done 80,000 k's and are still very much road worthy. I have worn the outer edge of one tyre as I've got a slow leak that I'm too lazy to have fixed. Run my tyres at 40 / 41 psi religiously....the ride is great and would happily fit these again.

[wazafi Junior Member Find all posts View Profile Close wazafi]

Hi Krypto

I am not on my ride. Interstate by air.
Will push up the pressure again on return.

Running below 30psi cold on a highway is asking for trouble you mentioned. Is it applicable only for the Prado?

My previous ride was the XC90 with pressure set 220 to 270 kPa..... which in this case is equivalent to 32 to 39psi.

Just wondering why the has that 210kPa setting sticker at the side door.

[wazafi Junior Member Find all posts View Profile Close wazafi]

Hi Krypto

I am not on my ride. Interstate by air.
Will push up the pressure again on return.

Running below 30psi cold on a highway is asking for trouble you mentioned. Is it applicable only for the Prado?

My previous ride was the XC90 with pressure set 220 to 270 kPa..... which in this case is equivalent to 32 to 39psi.

Just wondering why the has that 210kPa setting sticker at the side door.