Tyre pressures you run in your stock NA tyres

[93_Clubman]

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

Most, if not, all defensive/ advanced driving instructors will advise 32psi cold or higher. These days probably even some of the suburban driving instructors will similarly advise higher than the factory recommendation depending on their background.

[miata]

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

Most, if not, all defensive/ advanced driving instructors will advise 32psi cold or higher. These days probably even some of the suburban driving instructors will similarly advise higher than the factory recommendation depending on their background.

Yep, and the 26 on the placard, is absolute minimum, for cars being used primarily for shopping. Also to cater for markets such as the US, where ride comfort is king. The car doesn't come to life until the tyres are run at a decent inflation, it's not supposed to ride like a Rolls, it's a Sports Car and a light one at that.

[GP]

On the track, ride is not important. Keeping the tread face square with the road for maximum grip and instant response to steering wheel input is

I find it strange because when you take a bike on the track most run lower than the recomended pressures to allow the sidewall to flex increasing the grip. I just thought cars would be the same

[93_Clubman]

On the track, ride is not important. Keeping the tread face square with the road for maximum grip and instant response to steering wheel input is

I find it strange because when you take a bike on the track most run lower than the recomended pressures to allow the sidewall to flex increasing the grip. I just thought cars would be the same

Under inflating on a bike should give you a better tyre contact patch for cranking over during cornering, however it would be at the cost of some increase in slip angle due to more lateral tyre flexion.

[snshami]

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

Most, if not, all defensive/ advanced driving instructors will advise 32psi cold or higher. These days probably even some of the suburban driving instructors will similarly advise higher than the factory recommendation depending on their background.

I know that and that is why I always used to run 36psi. I thought maybe because the MX-5 was light and had a lower centre of gravity therefore it did not load the sidewalls as much hence the lower pressures.

Anyway today I put it on 30psi. Lets see how we go with this.

[91 Malibu]

As others have said, since doing a defencive driving coarse 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.

Off topic I am really enjoying your threads whether I agree with you or not they are bringing some very good debates.

[snshami]

As others have said, since doing a defencive driving coarse 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.

The skittishness was going around a small roundabout very fast and the road was not smooth. I am a bit over sensitive to road feel so maybe what I call skittishness would not bother someone else.

Off topic I am really enjoying your threads whether I agree with you or not they are bringing some very good debates.

Thanks. That is what I was trying to contribute. I often find that being a bit controversial helps in generating a lively debate. I just need to be mindful that I don't offend anyone.

[Entice]

In Melbourne, I would try, and personally have used:

Ralph at TruTrack suspension in NorthMelbourne,

and Ricky at Essendon Tyrepower (now in Niddrie?keilor Rd)


Both of these guys have a racing pedigree.



PS, didnt realise Dunlop was making Potenza's.... Bridgestone might have something to say about that!!!

[Mr Morlock]

Who does wheel alignments and what do they cost - how about checking in the old fashioned way? Try also the search facility.

[de Bounce]

For advice on tyres and wheel alignment, I recommend you give Ray a call at Reservoir Tyrepower.
Another dealer with racing pedigree and a good understanding of MX5's.
I take all my cars there for alignment and tyres for a number of years and never had an issue.

[Garry]

I also went to the Mazda sponsored free advanced driving course and was also told to inflate my tyres to 37PSI. I find it strange that the ideal tyre pressure for every car available in Australia is 37PSI. The course I went to was heavily attended by fleet drivers in Falcons and Commodores and the course was biased towards them as was, I suspect the tyre inflation recomendations as well. It seeems strange to over inflate a Golf tyre by only 1PSI from manufacturers recomendations yet overinflate an MX5 tyre by 11PSI. What happens when you get to something like an Audi S3 with manufacturer recomended pressures of 39PSI. Should they be underinflated to 37PSI?

I found 28 to 30PSI gave the best grip/handling/ride combination in my NA on 15" rims and 30 to 32PSI in my NB on 16" rims depending on what tyre was being used at the time. Any higher and the cars got skittish and lost grip in corners on the crap roads we have around my area. 37PSI in either model using the tyres I've been using made the cars very unsettled through rough or corrugated corners.

Where as my Mirage is quite happy running mid 30's tyre pressures, yet it's much lighter than my MX5.

[snailspace]

This is a really interesting thread and in that everyone seems to run completely different pressures, personally i run 205 50 r15 toyo's and have done for 6 yrs and always run 38psi front and 40psi rear, I found 40psi in the front gave me a bit of understeer and feels a bit squirmish at 35psi, the rears I've alwys runs 40psi and had plenty of grip. I now have a roll bar and i think that has stiffened the rear quite a lot so i might experiment with the rear pressures to try and dial some of that out and make it a little less skittish over bumps. stay tuned. . . . and yay for a thread that made me post for the first time in about 18mths!!

[snshami]

I also went to the Mazda sponsored free advanced driving course and was also told to inflate my tyres to 37PSI. I find it strange that the ideal tyre pressure for every car available in Australia is 37PSI. The course I went to was heavily attended by fleet drivers in Falcons and Commodores and the course was biased towards them as was, I suspect the tyre inflation recomendations as well. It seeems strange to over inflate a Golf tyre by only 1PSI from manufacturers recomendations yet overinflate an MX5 tyre by 11PSI. What happens when you get to something like an Audi S3 with manufacturer recomended pressures of 39PSI. Should they be underinflated to 37PSI?

I found 28 to 30PSI gave the best grip/handling/ride combination in my NA on 15" rims and 30 to 32PSI in my NB on 16" rims depending on what tyre was being used at the time. Any higher and the cars got skittish and lost grip in corners on the crap roads we have around my area. 37PSI in either model using the tyres I've been using made the cars very unsettled through rough or corrugated corners.

Where as my Mirage is quite happy running mid 30's tyre pressures, yet it's much lighter than my MX5.

Skittishness on bumps is what I am feeling as well. Presently am running 30 psi and I can feel more rattles than when I was running 28psi otherwise it feels the same.

[miata]

I also went to the Mazda sponsored free advanced driving course and was also told to inflate my tyres to 37PSI. I find it strange that the ideal tyre pressure for every car available in Australia is 37PSI. The course I went to was heavily attended by fleet drivers in Falcons and Commodores and the course was biased towards them as was, I suspect the tyre inflation recomendations as well. It seeems strange to over inflate a Golf tyre by only 1PSI from manufacturers recomendations yet overinflate an MX5 tyre by 11PSI. What happens when you get to something like an Audi S3 with manufacturer recomended pressures of 39PSI. Should they be underinflated to 37PSI?

I found 28 to 30PSI gave the best grip/handling/ride combination in my NA on 15" rims and 30 to 32PSI in my NB on 16" rims depending on what tyre was being used at the time. Any higher and the cars got skittish and lost grip in corners on the crap roads we have around my area. 37PSI in either model using the tyres I've been using made the cars very unsettled through rough or corrugated corners.

Where as my Mirage is quite happy running mid 30's tyre pressures, yet it's much lighter than my MX5.

Skittishness on bumps is what I am feeling as well. Presently am running 30 psi and I can feel more rattles than when I was running 28psi otherwise it feels the same.

How old are the shocks? You can't test shocks on an MX-5 by bouncing the car as you can with other cars, they need to actually be tested on a test rig but if you're getting skittishness with such low pressures, I'd be looking there first. I never ran less than 34 and never had skittishness.

[snshami]

Instructors at the FREE Driver Training Course, given with new MX-5s, always insisted on 37 psi.
They would send people out with gauges during the first classroom session and those who didn't have the specified pressures were given a few minutes to find a "servo" and rectify the situation.
During the course of the lectures, they then explained why. Of course the Station wagon driving traveling salesperson in the group, always argued with the experts because "they knew better" but by the end of the day were converted to sacrificing a little comfort for more car control and greater safety.
I think most of us then knocked a couple of psi off the optimum and used around 33 - 34 psi for the road. Certainly worked with my NA and even better with the NB, especially after I fitted the Konis.

I can vouch for the fact that all instructors at driver training courses do that. I have myself done five

There are several reasons why they insist on this. The first one is that driver training courses teach you to correct slides. They are also often partially conducted on dirt tracks.

One of the big reasons they give is to prevent the tyre peeling off the rim when the car is going sideways (like in a skid). Apparently two things cause rollovers. The first thing is the side of the wheel hitting something such as kerbing and the second is tyres peeling off and being trapped under the rim.

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.

Clearly for any given tyre and vehicle there is an optimal pressure zone. Anything lower causes reduced tread contact to the road and excessive heat build up at constant high speed, which leads to high speed blow outs. Anything higher also reduces tread contact to the road. Too high pressures also affect your overall spring rate and your unsprung and rotational masses.

My initial question was in the hope of understanding what the optimal compromise on an NA MX-5 with stock wheels and tyres is. 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.

Right now I am running 30 psi on the MX-5 and it appears to be about right. I'll keep on playing with it a bit before I settle on a final number.