Technical Tyre Pressure

[oXRUSSXo]

I'm running 195/45/15 on my Punto. I currently put 32 psi in the tyres all round. But the ride feels really hard and personally I think the tyres look like there isn't enough air in them. Can anyone recommend a tyre pressure

Thanks

 

[Ziggy122]

because its a 45 profile - its got less flex = a harder ride

stock for 185/55/15 is 28psi
I would have thought that the 195/45/15 somewhere around 28-34 is the required pressure

How is the tyre wearing? Middle or shoulders? as thats a clueto the tyre pressures required

Ziggy

 

[PuntoHowTo]

195/45/15 is a really low profile, your speedo will be seriously under reading.

I ran my 195/50/15s at 34psi front and 32 rear

 

[oXRUSSXo]

195/45/15 is a really low profile, your speedo will be seriously under reading.

I ran my 195/50/15s at 34psi front and 32 rear

Thanks its the tyres that was on the car when I got it. As for the speedo it seems to be quite accurate when going past those lamp posts that read your speed and display it

 

[Brendan W]

Low profiles are harsh. I run towards the top end of recommended pressure range for everyday use. It's a bit harsher and lighter on the steering but I trade that for rolling resistance and fuel economy.
If you want to play, check the pressures cold and hot after say a reasonably brisk spin of ten miles or do.
The pressures should go up. As a base line if they haven't gone up 10% they are too hard and if they go up more than 10% they are too soft.

 

[Ziggy122]

because java is banned from IE and Firefox for use (stupid i know)
I cant get on the miata tyre calculator

Another one i've just used says the following

the 195/45/15 tyre has (vs the stock 185/55/15)
-4.8% Diameter difference
5.5% width increase
-14% sidewall difference
-4.8% in circumferance
5% increase in Revolutions per mile

So in thoery the 195 should wear out quicker because its traveling furhter per mile

The website shows the speed difference, which aint hugely different @30

Have a look for yourself
Remember on 15" the stock size is 185/55/15
http://tire-size-conversion.com/tire-size-comparison/

Ziggy

 

[PuntoHowTo]

As Ziggy said it will be fine at 10 - 20 - 30mph

But the faster you go the bigger the difference



Plenty of websites have comparison calculators.

You can see the difference at 70mph will have you doing an actual 66mph

 

[oXRUSSXo]

As Ziggy said it will be fine at 10 - 20 - 30mph

But the faster you go the bigger the difference

View attachment 148288

Plenty of websites have comparison calculators.

You can see the difference at 70mph will have you doing an actual 66mph

Hi I have been looking at that website and really it should be ok as I don't drive very far to be honest the fatest road I go on is a 60mph so does that mean that my speedo shows a higher speed than I'm actually doing?

Thanks

 

[Ziggy122]

Hi I have been looking at that website and really it should be ok as I don't drive very far to be honest the fatest road I go on is a 60mph so does that mean that my speedo shows a higher speed than I'm actually doing?

Thanks

When your speedo says your doing 70mph - your doing 66mph
So your dash/speedo will probably say roughly your doing 74/75 todo 70mph

Tbh - i wouldn't bother touching it / trying to alter it

I'd like to keep it that way personally - your less likely for a speeding ticket

Ziggy

 

[PuntoHowTo]

Hi I have been looking at that website and really it should be ok as I don't drive very far to be honest the fatest road I go on is a 60mph so does that mean that my speedo shows a higher speed than I'm actually doing?

Thanks

Don't get me wrong it's not a world ending issue, but......

Insurance companies have started asking if you have aftermarket fitted alloy wheels (even if they are OEM like mine) if the tyres are the manufactures specs, because it throws the speedo out and can alter the handling of the car, next time you need new tyres I'd recomend changing the whole set, will make for a much more comfortable ride aswell

 

[portland_bill]

For tyre pressures, look on the website of the tyre manufacturer, somewhere there should be a list of pressures. See if they list it for your vehicle, if so, use their pressures. If not listed, you'll have to do a tedious search to find others they are fitted to, and compare pressures. Many tyre companies recommend one pressure for a tyre whatever fitted to, as it should only be fitted to vehicles that match its load/speed capabilities.