Tyres Look Deflated On Toyota Diesel Cars

[Johan007]

I have a 2.2 Verso and previously had 2.0 Auris and when I inflate to the recommended pressures the front tyres always look flat and on most types of tyre. Is this right? I need to inflate to at 40psi for the
sidewalls not to bulge and look like my Petrol cars. I compromise at 38psi on the fronts. On cheaper tyres 40psi+ used to result in less grip however now I use premium Goodyear I am not concerned about this. The higher pressures feel better on premium compounds.

So my queastion is are Toyota’s tyre pressure recommendation incorrect for heavier bigger engines?

[FROSTYBALLS]

I would imagine that tyre pressures quoted by Toyota are arrived at through consultation with the tyre manufacturers supplying tyres for that particular vehicle model/size of tyre. Why do you think you know better than the car/tyre manufacturers?

From the Michelin website:

"By keeping your tyres at their correct pressure, you’ll reduce your running costs. Under inflated tyres are prone to overheating use more fuel and wear out more quickly. Likewise, over inflation can reduce tyre life, reduce grip and cause steering problems."

[Parts-King]

Stick to the recommended pressure, the engine is one heck of a weight, but the correct tyres are built to stand the weight

Don't inflate the pressures to make the tyre "look" inflated

Kingo

[Cyker]

I think it's normal; Both of the diesel Mk1 Yarisususes have that bulgy tyre look on the stock tyre PSIs.

I do notice increased shoulder wear at stock PSI tho' and because of that and for MPG reasons, I usually run 38-40 on the front and 35 on the back to give it a bit more structure.

It suits my driving style as I tend to pulse and glide and the harder tyres helps extend the glide. Grip in the dry is better too, esp. at speed, but slightly less good in the wet, and much worse in the snow (As you'd expect! )

My only concern is on days like this where it's very hot and I'm doing long motorway runs as that'll increase the pressure in the tyre past 40psi which will start bulging out the centre of the tread and increasing wear along the centre line.

The bad one is under-inflating as this causes high tyre wear and, at speed, can cause the tyre to burst. Over-inflating on the other hand doesn't really change things that much and slight over-inflation will have no increased risk of tyre failure. If anything it adds a bit of safety at speed as it stiffens the tyre up. (This is, I assume, why the car has higher PSI specs for travelling >100mph (ahaha) or when heavily loaded)

Another alternative is to switching to a LRR tyre - They often have slightly stiffer sidewalls as part of the tricks to reduce rolling resistance which reduces the bulge (Slightly over-inflating a normal tyre is kindof a poor man's LRR )

[FROSTYBALLS]

Think the reference to travelling at a higher speeds relate to above 100kph (62mph).

[Cyker]

You made me have to double check that because it indeed sounds quite ludicrous but no, it indeed gives elevated pressures for 100mph/160kph!!

This is quite amusing given that a Yaris can barely hit 100mph and no sane person would want to anyway because when it does it's !Removed! terrifying because it feels like you're floating and skipping with no sense of any steering input!