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[darklord]

 I hate the hard ride in my car.

MOT this morning - straight pass for the third year running! Hey, that hard ride is not so bad after all...

On such a light car, do you think I could safely reduce the tyre pressures to say, 29 psi?

[Alex]

29 PSI (2 bar) front 26PIS (1.8 bar) rear is safe as long as you don't do prolonged high speed or have loads in the car. It won't ruin your handling but please remain aware of the lower tire pressures and drive accordingly.

Rear suspension is a bigger compromise than front due to the bigger variances in load it has to accommodate, so when the car is empty the ride is needlessly hard and the natural frequency of the suspension is also higher. When there's no-one in the back 1.8 is plenty.

If you have low profile tires (17") i would not go under 2.0 bar unless you have the XL or Reinforced tire walls, otherwise you risk the tire slipping under the rim when cornering hard or in emergency avoidance.

So 2.0 and 1.8 as long as the car is empty and you don't drive fast, otherwise adhere to manufacturer recommended pressures because they know best and have tested these extensively.

[darklord]

Thanks for your reply.

Not so sure about the sustained  high speed part - I'm on the motorway at the moment!

I may try lower pressures though - this ride is ridiculous.

[darklord]

Hmm, well altering the pressures certainly makes the handling interesting, but then a Colt is much higher than a Smart, and for the time being I'd much rather have a less rough ride!

[Ocracoke]

This might be barking up the wrong tree here... but is the driver seat foam in good shape? Mine gets awfully uncomfortable on long trips and when it does, it feels like a hard(er) ride than normal to me.

[CrazyG]

Sure by today's standards the ride may 'appear' to be hard..ish...
But let's not forget, the car is a design that is over 13 years old,
and  in it's day the ride quality was no worse than that of most
similar mid sized cars, like a Fiesta or Astra then.

If you had the chance to drive a similar aged one of those vehicles
now, and then a drive in the current 2017 model then you would
find exactly the same issue.

It's a bit like Marmite then...you either love it or you hate it.
If you like what the 454 does and what it costs to run, then you
have no option other than to gracefully accept it's shortcomings.
Or you can compromise to a slight degree and reduce the tyre
pressures a fraction with the hope that you don't wear out the
outer edges of the tread due to under-inflation.  Make your choice.

[cecil]

you could always consider fitting higher profile tyres to your wheels- providing of course you don't foul the bodywork. Or see if the smaller rims n  taller tyre combos fit eg 15 rather than 16

[darklord]

My car is the basic model with 14 inch wheels, wearing 175/65/14 tyres.

[cecil]

Your tyres are already quite high profile and so changing them would not make a big  difference. The other idea might be to replace the shock absorbers age/ wear and tear can make a difference. The rears are easy to swap.

[CrazyG]

You always have the option to change tyre sizes..so long as they
are not more than 2.5% different....such as going up to 185/65R14
which will give a bigger 'cushioned' profile (+2.3%)...or....
go  down in profile width, but up in height to give a different
cushioning affect..such as 165/70R14.

Changing to either will have some obvious differences, with the
slimmer profile offering the possible benefit of better fuel economy
due to less rolling resistance due to a slightly smaller tyre contact
area on the road. The wider tyre will not necessarily be the better
choice over what you have as rolling resistance will be greater and
it will 'tramline' in road ruts and possibly give spongy handling.
tyre on the road, and the possibility of tramlining in road ruts,
whereas the slimmer 165 profile will reduce the rolling resistance.

[darklord]

Hmm, well tire pressures at 26 rear are scary!

Back to 30psi and crashy ride...

[Deszus]

So recommended pressure is 32 psi by Mercedes. Up to 38 psi when with heavier load. That's for 1.5 CDi.

I used to pump them well to 33 psi. Better handling when turning with this pressure. Conti Sport Contact 5 195/50R15 all four.

[CrazyG]

What suits the 454 may or may not be the same for the Colt.
See/read your Owners Handbook for the recommended tyre pressures.
You could also check inside the petrol flap to see if Mitsubishi
followed Smart's idea of placing a label there,with tyre sizes
and the appropriate pressures for them with different load settings.

[darklord]

Well I'm back to 29psi in the rears which improves the scary handling...

[CrazyG]

As per Alex's first post...the ride at the rear is a compromise
as it has to take a variety of loads. It'll feel more 'planted' and even
quite compliant when you have a passenger in the rear.
So, either don't go out without a passenger in the back seat, or stick
a 'lost lamb' you find roaming the moors in the boot...LOL...
or a big sack of potatoes or bag of cement in the boot.