Non-OEM tyre pressures

[mo]

Would anyone know whether non-OEM tyres such as SO3's require different tyre pressures to those in the manual?
My '91 on stock alloys seems to not like factory settings whilst on track.
Thanks.

 

[Acuraphile]

Yet another area of controversy and great interest. I did a search in all areas of the site, and came up with 88 responses to "tire pressure". One of the clearest responses comes from Lud, here:
http://www.nsxprime.com/ubb/Forum1/HTML/000129.html

He says to start at normal pressure, and adjust downward, until you have found the optimum point. However, I advise you to look at a good sampling of the 88 answers to get a broader picture concerning this topic.

Regards,

Bill

 

[pacman]

I have a stock 91 and put on BBS LM wheels (17x7.5F and 18x9.0R) with SO3s and the car is great on the track and the street. Only improvement would be suspension (eg S-Type) and track tires.

 

[pacman]

Sorry .. I forgot to say that I use the OEM pressures (32F 40R) on the street and start there on the track and lower the pressure with temperature. On the track you have to constantly check and adjust. The Yoko OEM tires were all over the place but the SO3s, once adjusted, stay there.

 

[nsxtasy]

Originally posted by pacman:
Sorry .. I forgot to say that I use the OEM pressures (32F 40R) on the street and start there on the track and lower the pressure with temperature. On the track you have to constantly check and adjust.

Nope. You should find the pressures that work best for you, and leave them there. For example, you may find that the OEM pressures of 33F/40R measured cold work great on the track. As you heat the tires up, those pressures change, maybe rising by 5-7 psi. So maybe you wind up with hot pressures of 39F/46R. How do you reach those pressures? By starting out with the tires at 33F/40R cold! There's no need to adjust at all.

The only reason you should have to check and adjust is if you don't like the way the car is behaving - and if this is the case, you can make your adjustment at the start of the day next time, so there's no need to change pressure during the day. For example, let's say you're at the track don't like the handling and you decide to add more air in the front, so that the pressures (with the tires still hot) become 41F/46R. Well, then next time you go to the track, start out with the cold pressures 35F/40R and you should be fine - again, with no need to change during the day.

[This message has been edited by nsxtasy (edited 10 July 2002).]

 

[mo]

Thank you all for your help.
My feelings so far have been that hot pressures of 33F 40R are OK but too much understeer for n=my liking.
Hot front pressure a little higher may be in order, but it does seem there is no exact answer.

 

[pacman]

NSXstasy is not wrong, but ... The essential point I was trying to make was that the SO3s (which were the subject of the Q) are very consistent on the track. I start at 32/40 cold and depending on the ambient and track temperature they tend to go up to 43/50 and stay very consistent after that for the day. If I find that the traction is not right I might drop the pressure a bit based on "feel". How do you know how the tires will work on a given day if you don't go on the track first. I disagree that you can just go by what was right the last time - which might have been a month before?

By the way, the durability of the SO3s has been great.

 

[nsxtasy]

Originally posted by mo:
My feelings so far have been that hot pressures of 33F 40R are OK but too much understeer for n=my liking.
Hot front pressure a little higher may be in order, but it does seem there is no exact answer.

33F/40R sounds VERY low for pressures measured hot on the track.

 

[mo]

I usually start at factory cold then drop as temp goes up. Running with hot rears at about 48psi made the rear feel very light.
I will try starting at OEM cold and drop less this time and see what happens.
I need to get a tread wear gauge to check for over-inflation.
Does everyone switch off the traction control on track?
Mo.

 

[nsxtasy]

Originally posted by mo:
Does everyone switch off the traction control on track?

I didn't when I was first starting out, but I do now that I have a fair amount of experience on the track.

 

[erobbins]

You'll find the proper tire pressures for the track by using a pyrometer and measuring tire temperatures across the face of the tire. Once you've made sure the tires are not too hot in the middle as compared to the edges or vice-versa, you've found the optimum tire pressure.

The idea is to have the largest contact patch you can have... underinflating or overinflating will reduce this contact patch.

That said, I have found that slightly overinflating my track tires (Yokohama A-032R) yield a better feel and faster lap time. I know they are slightly overinflated because the center of the tread is clearly wearing more than the edges. Even so, my tire temps are even across the tire (accounting for a slight increase towards the inside due to negative camber), which indicates that I'm using as much of the tire as I can.

EDR