Over inflated tyres

Odd · Postby **Odd** » Thu Mar 03, 2016 8:51 am

Would overinflated tyres (36psi) on a NA8 gave it potential to understeer?

Magpie · Postby **Magpie** » Thu Mar 03, 2016 9:02 am

On the track or in general? 36 psi all tires hot or cold? What tires? Under braking? On corner exit?

Oversteer can be corrected by lowering all the tire pressures slightly or just the rears.

Odd · Postby **Odd** » Thu Mar 03, 2016 9:25 am

Standard NA8....ATENZA 185/60R14....36psi cold
On public road, at speed limit,going down Hill from Mt Glorious to Samford
braking into a corner....

Car under-steered....never done that before

but I normally run tyres at 26psi....36psi was by others....and I was't aware at the time

Magpie · Postby **Magpie** » Thu Mar 03, 2016 9:32 am

Sounds like the problem, however 26 cold is possibly a bit low for normal road use (my opinion).

Drop the tyre pressures and see if it makes a change.

rascal · Postby **rascal** » Thu Mar 03, 2016 9:45 am

sooooo many variables that could be at play here, that trying to provide a meaningful answer is almost impossible.

how long had you been driving since cold?
how enthusiastically had you been driving since cold?

Both of the above could change what pressure the tyres were at at the time.

were all tyres at 36psi cold or just rear or just front or just one?

Was there any debris on the road? oil, water, gravel.
Was the weather colder or hotter than usual..
What time of day was it, was there dew on the ground
Did you enter the corner quicker than usual.
Did you brake heavier than usual
Did you have the same load in the car as usual.

blah, blah, blah.

Yes, a higher than normal pressure 'could' have caused it but it could also have been a dozen other reasons..

Just put the pressures back down to what you normally run (26 seems low) and in future limit others adjusting it, or check yourself afterwards.

JBT · Postby **JBT** » Thu Mar 03, 2016 9:46 am

Around 30 psi cold should work for normal and spirited use. 36 cold is way too high IMO.

Odd · Postby **Odd** » Thu Mar 03, 2016 10:05 am

All tyres were 36psi cold....
had just dríven up from gap to Mt Nebo....

Could have been oil on the road?
It has been posted here that roads in that area had issues

Seems many garages over inflate tyres on MX5's....no thought given to them being a very light car

I recently had the car serviced at a MX5 specialist....and didn't check tyre pressure after....I thought they would know what they were doing

When I found out that the tyres were over inflated (checked when I got petrol), I spoke to workshop manager

His response was they pump all tyres to 36psi....as under inflated tyres are a bigger danger....and most don't check tyres between services

My concern is that this practise on MX5.....isn't just ill conceived....it could be dangerous

Manufacturer recommends 26psi....Tyre manufacturer recommends another 4psi for high speed or extra load

Magpie · Postby **Magpie** » Thu Mar 03, 2016 10:33 am

Lower the tire pressures and go for another run in the same area, driving to suit conditions and see if it 'feels' any different.

Second what Rascal posted there are so many variables at play. At least putting the pressures back to 'normal' would remove this variable.

I still think 26 is low for road use. If on the track you would expect about 6° increase, however getting that much heat into a tire on the road would be difficult. Again if that is what the OEM recommends then go for it.

Steampunk · Postby **Steampunk** » Thu Mar 03, 2016 10:42 am

+1 to Rascal's reply.
Rubbish tyres as well. Google can't find Atenza brand, did you mean Aderenza?

36psi is not significantly over inflated. Most people will run between 31-34 with no adverse effects.

A good set of tyres should always be first and foremost for ANY car.

Odd · Postby **Odd** » Thu Mar 03, 2016 10:43 am

Sorry....Altenzo....

Mis-spelt

SE · Postby SE » Thu Mar 03, 2016 10:51 am

Odd wrote:Would overinflated tyres (36psi) on a NA8 gave it potential to understeer?

Manufacturer recommends 26psi....Tyre manufacturer recommends another 4psi for high speed or extra load

Why are you running 36

Odd · Postby **Odd** » Thu Mar 03, 2016 10:56 am

SE wrote:
Odd wrote:Would overinflated tyres (36psi) on a NA8 gave it potential to understeer?

Manufacturer recommends 26psi....Tyre manufacturer recommends another 4psi for high speed or extra load

Why are you running 36

See earlier post....

I recently had the car serviced at a MX5 specialist....and didn't check tyre pressure after....I thought they would know what they were doing

When I found out that the tyres were over inflated (checked when I got petrol), I spoke to workshop manager

His response was they pump all tyres to 36psi....as under inflated tyres are a bigger danger....and most don't check tyres between services