Tyre pressures you run in your stock NA tyres

[93_Clubman]

The second reason why they insist on such high pressures is because it actually reduces the contact area to the road making it easier to initiate sliding.

This comment suggests that the aim of recommending higher air pressure is to make it easier to initiate a skid on a public road, which would be less than optimal from a public safety perspective.

I do not buy into the argument that the pressure has to be the same for all cars regardless of weight, centre of gravity, tyre construction, tyre profile, etc etc.

No one's arguing that point - indeed, NA & NB owners know that the sidewall of their space saver spare tyre states "inflate to 60psi".

Forumites are simply recounting advice given to them, i.e. the new MX5 purchaser course recommended 37psi in the context of a course for new MX5 owners, while another course recommended 40psi regardless of car.

Instructors at the FREE Driver Training Course, given with new MX-5s, always insisted on 37 psi.

As others have said, since doing a defensive driving course where they wanted 40psi regardless of car, I run my MX5 with 195/15/50 dunlop potenza's at 36psi & dont seem to get the skittish ride you are talking about.

In the case of the latter course, I'd suggest that while 40psi was suggested to course participants, it's a figure which takes advantage of being able to run high air pressure in modern construction tyres with less deformation, noting that people will eventually adjust it to suit their driving requirements, with the overall aim of achieving higher inflation pressures than the typical 20 something of the past.

[snshami]

As others have said, since doing a defensive driving course where they wanted 40psi regardless of car, I run my MX5 with 195/15/50 dunlop potenza's at 36psi & dont seem to get the skittish ride you are talking about.

In the case of the latter course, I'd suggest that while 40psi was suggested to course participants, it's a figure which takes advantage of being able to run high air pressure in modern construction tyres with less deformation, noting that people will eventually adjust it to suit their driving requirements, with the overall aim of achieving higher inflation pressures than the typical 20 something of the past.[/quote]

There may be tyres whose construction allows 40psi. The only issue I would having this on my MX-5 is the negative effect it would have on the overall suspension. Any well sorted suspension is designed and tuned as a whole system that includes everything from chassis flex all the way down to the tyre sidewall flex. Any change to any of the parameters can have a negative effect on the overall system. If the system has been designed well it will have a fair degree of robustness built into it, which will at minimum allow for production tolerances and effects due to wear and tear to not have an effect on the quality of the system's output.

Now for any suspension system there will invariably be many stable states of tune. You can bias it towards a softer ride or a more grip, less roll, easier controllability etc. etc. However there will be only one that replicates the feel of the car the way Mazda designed it.

I am not saying here that the factory state of suspension tuning is the only right thing to do. It was undoubtedly appealing to lots of people; but it is not the only way.

The system will change the way it responds if the any significant changes are made to any of the design parameters. This includes changing the wheel weight or its own springiness, something that higher tyre pressures will do.

I do not know the MX-5 well enough yet, to be able to guess how far I can push it before it stops feeling like it was intended to by Mazda. Since I am really enjoying the feel at the moment I do want to make any changes.

[93_Clubman]

Your not telling us anything we don't know.

There may be tyres whose construction allows 40psi.

In 2011, all new passenger car tyres are capable of this - maximum inflation is usually marked on the tyre sidewall.

However there will be only one that replicates the feel of the car the way Mazda designed it.

Well Oscar Pereda, an tyre engineer for BF Goodrich, disagrees with you: "There is no 'golden' tire pressure," Oscar said. The optimal setting depends on the individual driver and his preferences".

If you want to replicate what you think Mazda intended, then run whatever the tyre placard of the car says, noting that this is a Mazda Corporate compormise of the side of comfort, & not handling performance. But ultimately it still comes down to your interpretation of what is: "...the feel of the car the way Mazda designed it." & "...feeling like it was intended to by Mazda.", which we may not share with you.

[Entice]

OK, I'll Bite

what's on the placard is what was "determined" using the oem tyres.

Modern tyres are different to the mud slingers on 1987, 88, 89 etc etc

and so too is their construction.

Personally, I prefer 28PSI cold, and that's with my suspension setup and alignment... (185/60/14)
even 32 psi is unbearable in my car for day to day commute, for a bloke with lumbar and thoracic issues...

[93_Clubman]

OK, I'll Bite

what's on the placard is what was "determined" using the oem tyres.

Modern tyres are different to the mud slingers on 1987, 88, 89 etc etc

and so too is their construction.

Indeed - was going to add that the NA6 when first produced was supplied with lightweight Bridgestone & Dunlop tyres specially made for the MX5 (at least in the case of the Bridgestone), which when I enquired to replace mine in the early 90s were no longer available.

[snshami]

Your not telling us anything we don't know.

There may be tyres whose construction allows 40psi.

In 2011, all new passenger car tyres are capable of this - maximum inflation is usually marked on the tyre sidewall.

However there will be only one that replicates the feel of the car the way Mazda designed it.

Well Oscar Pereda, an tyre engineer for BF Goodrich, disagrees with you: "There is no 'golden' tire pressure," Oscar said. The optimal setting depends on the individual driver and his preferences".

If you want to replicate what you think Mazda intended, then run whatever the tyre placard of the car says, noting that this is a Mazda Corporate compormise of the side of comfort, & not handling performance. But ultimately it still comes down to your interpretation of what is: "...the feel of the car the way Mazda designed it." & "...feeling like it was intended to by Mazda.", which we may not share with you.

I like the way the car feels now. It feels very balanced and natural to me. I would not go as low as 26psi and prefer to stay on the higher side of what I think the design robustness would allow for. I really have no intention of mimicking someone else unless doing so made sense to me. If I was racing the car I would do what I need to do to win a race but I have no plans to race.

As for current tyre pressures in modern cars, even though tyres can tolerate 40psi, most modern manufacturers of sporty cars keep recommended pressures between the range of 28 to 32psi.

[Entice]

My GTI has a placard for 38PSI Cold Unladen

feels better at 35....

[93_Clubman]

As for current tyre pressures in modern cars, even though tyres can tolerate 40psi, most modern manufacturers of sporty cars keep recommended pressures between the range of 28 to 32psi.

That may be so for sporty cars where comfort is a priority for many drivers, but we're talking Sports cars.

[samx5]

I know most people think the placard pressure of 26 psi is too low, but I wonder why Mazda would go to all that trouble to design a sportscar from the ground up, and then deliberately curtail its abilities by recommending a tyre pressure that made it handle less well that it was capable of? Doesn't make sense.........

[miata]

I know most people think the placard pressure of 26 psi is too low, but I wonder why Mazda would go to all that trouble to design a sportscar from the ground up, and then deliberately curtail its abilities by recommending a tyre pressure that made it handle less well that it was capable of? Doesn't make sense.........

Because they wanted to sell it in America. Americans don't like a firm ride and most customers aren't buying it because it's a sports car, they're buying it because it's "cute".
The true enthusiasts (very much the minority buyer) know that the placard pressures are a compromise and add several pounds on top of those minimum pressures because we're looking for performance.

[93_Clubman]

I know most people think the placard pressure of 26 psi is too low, but I wonder why Mazda would go to all that trouble to design a sportscar from the ground up, and then deliberately curtail its abilities by recommending a tyre pressure that made it handle less well that it was capable of? Doesn't make sense.........

Because they wanted to sell it in America. Americans don't like a firm ride and most customers aren't buying it because it's a sports car, they're buying it because it's "cute".
The true enthusiasts (very much the minority buyer) know that the placard pressures are a compromise and add several pounds on top of those minimum pressures because we're looking for performance.

Corporate compromise Mike - as Miata says Corporate's eye is firmly on the bottomline (& not even the triple bottomline in times like the present). The market segment to satisfy in this case is the largest, & that's comprised of people that want a comfortable ride. The designers & engineers as enthusiasts would have ultimately wanted more - indeed most of the threads on this & other MX5 forums would be non-existent if the MX5 was perfect, as there would be no need to finesse the car.

[GP]

Because they wanted to sell it in America

Sorry this doesn't make sense. They go to the trouble of rebadging it Mazda MX5 for us, Miata for the Yanks and Eunos Roadster in Japan and your saying that a tyre pressure sticker inside the door is to difficult to replace. Try again I reckon

[snshami]

Because they wanted to sell it in America

Sorry this doesn't make sense. They go to the trouble of rebadging it Mazda MX5 for us, Miata for the Yanks and Eunos Roadster in Japan and your saying that a tyre pressure sticker inside the door is to difficult to replace. Try again I reckon

I have to agree. I have worked with Mazda and they are sticklers for details. Nothing is ever to small for them.

[93_Clubman]

Reality is that most people don't like firm riding cars - after all at time of posting 44% of respondents to this poll run 30psi or lower, & this is an MX5 forum!

It's an individual choice - but if you're asking what's best from a handling performance perspective, as opposed to a comfort perspective, then higher is better on road & on track.

Indeed, if 20 something psi delivered the handling essence of an MX5, why do the racers run higher air pressure, up to a point, to achieve better times?

[manga_blue]

Racers run higher pressures because they can. Racetracks are smooth. If I go over 28psi on all the B-grade roads around here then I can barely keep the car on the road.