Tyre Pressures - What's the go?

[deucer]

I havent experimented too much yet with my lib, but in previous cars I have generally stuck to keeping it about 5psi under the OEM, having less pressure will affect your fuel economy, but it seems to stick to the road just that bit better.

Ouch! "Say hello to your Tyre power pro".... much sooner than you need to!

OEM recommended pressures are usually very low. Going even lower pressure by another 5psi is radial suicide!

But hey... the worlds FULL of variety eh? To each his own.

deucer.

[suff]

Hey I have Potenza RE001 and I run 40 psi. Thats what I was instructed to run these and they are fine.

Same, and thats in both my 17's (RE001's) and the 18's (RE050's)

Only recently made the move from 34PSI to 40PSI, and find minimal difference in noise / harshness, noticeable improvement in fuel economy though!

[smythie]

32 is way to low for the street you will wear out the edges of your tyres. i run 40psi on the road and that is not extreme

Just checked the placard on my Spec B. Subaru recommends the RE050A being set at 33/32 front/rear for low loads and 33/36 for high loads/sustained high speed. They would have done loads of km's at those pressures and they wouldn't be recommending a pressure that caused the tyre to wear abnormally

[jdm rsk]

32 is way to low for the street you will wear out the edges of your tyres. i run 40psi on the road and that is not extreme

Just checked the placard on my Spec B. Subaru recommends the RE050A being set at 33/32 front/rear for low loads and 33/36 for high loads/sustained high speed. They would have done loads of km's at those pressures and they wouldn't be recommending a pressure that caused the tyre to wear abnormally

your kidding tony......"wouldn't be recommending a pressure that caused the tyre to wear abnormally" sell more tyres

[Boxer]

I wouldn't think Subaru have a huge market for selling tyres to previous customers???

That said I think they are a little on the low side purely to give a better ride to 80% of their client base who want a nice smooth ride. I definitely dont think 30PSI is low enough to wear the edges from normal driving (as in make the edges contact the ground moreso than the centre).

It *may* exacerbate the driving style which is rolling the outside edges on heavy cornering anyway, in which a higher pressure would be adviseable yes.

[jdm rsk]

I wouldn't think Subaru have a huge market for selling tyres to previous customers???

That said I think they are a little on the low side purely to give a better ride to 80% of their client base who want a nice smooth ride. I definitely dont think 30PSI is low enough to wear the edges from normal driving (as in make the edges contact the ground moreso than the centre).

It *may* exacerbate the driving style which is rolling the outside edges on heavy cornering anyway, in which a higher pressure would be adviseable yes.

they are all in it together dont worry about that. i used to run 32 and both edges where gone, now run 39-40 and all even

[Boxer]

Wow, I'd be questioning the structural integrity of the tyre or alignment - was it both front and back?. A well constructed tyre should not allow collapsing of the centre of the tyre at 32PSI.

For example race tyres are far better constructed than street as we know and these are Dunlops suggested ideal pressures in race tyres:

Inflation Pressure Guide:

Sports/GT/Touring = 23PSI

The reason race tyres run low pressures is to allow the tyre to "work" a little with the surface and the sidewalls are far far stiffer as is the carcass. I found all this out the hard way years ago when competing in track sprints in a WRX. I was running R spec Dunlops with 36PSI at the track and couldn't understand why they were no grippier than the road tyres. Tyre Tech advised to try 28PSI and waddya know - tyres warmed up and became tacky Note I'm not suggesting this for road tyres - merely a point that stonger carcass tyres wont need the pressure a weaker tyre does

Agree we are talking street here, so a rule of thumb from BF Goodrich engineers for street tyres is (weight in lbs/100)

Liberties are 3400lbs? somewhere - makes 34PSI.


Regardless as previously stated there will always be personal preference to pressures run.

[senator]

I wouldn't think Subaru have a huge market for selling tyres to previous customers???

That said I think they are a little on the low side purely to give a better ride to 80% of their client base who want a nice smooth ride. I definitely dont think 30PSI is low enough to wear the edges from normal driving (as in make the edges contact the ground moreso than the centre).

It *may* exacerbate the driving style which is rolling the outside edges on heavy cornering anyway, in which a higher pressure would be adviseable yes.

they are all in it together dont worry about that. i used to run 32 and both edges where gone, now run 39-40 and all even

I wouldn't think Subaru have a huge market for selling tyres to previous customers???

That said I think they are a little on the low side purely to give a better ride to 80% of their client base who want a nice smooth ride. I definitely dont think 30PSI is low enough to wear the edges from normal driving (as in make the edges contact the ground moreso than the centre).

It *may* exacerbate the driving style which is rolling the outside edges on heavy cornering anyway, in which a higher pressure would be adviseable yes.

they are all in it together dont worry about that. i used to run 32 and both edges where gone, now run 39-40 and all even

right on the money shane, had my wheels balanced and aligned at the bridgestone centre, the guy laughed at the me and sti tyre place card, he said those tyre pressures where taking in comfort, in short i am running 40 psi all round

he said higher pressure ensure even wear and also protect the wheels when you hit pot holes.

[Fangin_RX]

Well at work most sedans we do get 36 PSI all round (We also tell the owner) unless you get the really pricey tyres then 40 PSI goes in them like the Run-Flats

[Boxer]

right on the money shane, had my wheels balanced and aligned at the bridgestone centre, the guy laughed at the me and sti tyre place card, he said those tyre pressures where taking in comfort, in short i am running 40 psi all round

.

Isn't that exactly what I pointed out on the first page the standard placard (or "place card" as you put it) is biased toward??

Granted higher pressures perform better - to a point. (I too run higher than the placard at 37 and 35 in the rear as it carries less weight), but I am surprised Shane experienced centre collapse at 32 and is why I'm genuinely curious whether it was front and rear or just front? Its conceivable to wear both the inside and outside edges of a front tyre if running toe out on the front (scrubs inside edges in straight lines) and giving them a hard time on corners at 32PSI (rolls onto the outside edges). Also why I asked if he had an alignment done at the time he swapped to 40PSI and what quality of tyre is being used.

Manufacturers are not going to specify dangerous settings to run their vehicle on - which would be the case if a tyre is significantly rolling on the outside and inside edges more than the centre - its water dispersal properties are severely hampered (aquaplaning) as is grip.

Finally I made the point everyone will have a subjective opinion here and its all personal preference and application from 32-40PSI

[jdm rsk]

right on the money shane, had my wheels balanced and aligned at the bridgestone centre, the guy laughed at the me and sti tyre place card, he said those tyre pressures where taking in comfort, in short i am running 40 psi all round

.

Isn't that exactly what I pointed out on the first page the standard placard (or "place card" as you put it) is biased toward??

Granted higher pressures perform better - to a point. (I too run higher than the placard at 37 and 35 in the rear as it carries less weight), but I am surprised Shane experienced centre collapse at 32 and is why I'm genuinely curious whether it was front and rear or just front? Its conceivable to wear both the inside and outside edges of a front tyre if running toe out on the front (scrubs inside edges in straight lines) and giving them a hard time on corners at 32PSI (rolls onto the outside edges). Also why I asked if he had an alignment done at the time he swapped to 40PSI and what quality of tyre is being used.

Manufacturers are not going to specify dangerous settings to run their vehicle on - which would be the case if a tyre is significantly rolling on the outside and inside edges more than the centre - its water dispersal properties are severely hampered (aquaplaning) as is grip.

Finally I made the point everyone will have a subjective opinion here and its all personal preference and application from 32-40PSI

the tyre were the factory bridgestone re50a and the wheel alignment was done just after they where fitted.

[swingn]

Since moving to the 18's (Now running 225/40 18) I've always run around 37psi cold... Seemed to keep everything wearing nicely.

But from some discussions over the weekend, it looks as though we should be running more like 40-42psi!

Now, running that sort of tyre pressure for improved tyre wear is one thing, but when I boosted up mine to 40psi on the weekend (Before going through Nasho ) it has made the ride extremely hard & you can really notice it on crapy road surfaces.

Also, I thought that having a very high tyre pressure was bad as it can cause "skipping / jumping" if you hit potholes in corners etc... Due to less flex in the tyres etc.

I'm just confused

[Boxer]

so if everything was wearing nicely and you were happy with the performance - why did u change ?

This is my point its all subjective above the min pressure specc'd by manufacturers. in the end go with what works for u. And much is fueled by tyre fitters & peers saying more is better.

I run 37 cold and have perfect wear (i also rotate every 6250kms and got 35-40kms outta the Pirelli's. )

Its a good compromise for daily driving for comfort and performance - certainly dont have any center collapse.

if I was to do a track sprint i'd probably run a bit more.

[swingn]

I was happy with the way they were riding with the lower pressures, & performance wise I can't say I noticed a massive difference (Unless I hit a pothole in the middle of a corner).

My tyres are wearing like sh!t anyway as I have a fair bit of megative camber on the front.

What I'm trying to find out, is what is the optimum pressure to run in our cars - Seeing as they are all pretty much the same. Surely, there must be a standard that we can all come up with

[smythie]

It depends from tyre to tyre too. Different tyres will have different compounds and construction. So while 35 might be best for one tyre, 32 might be best for another for the same driving conditions