Tyre Pressure

[Kujotk]

Got federal 595's at the front 235/45/17, and shitty Antyre 245/45/17 on the rear....

had a flat last week (leaky valve) so got it replaced, they went over all the tyres last friday, i recon they did it well..... well today i noticed the tyres looked alittle low. Its raining today so the tyre temps are pretty much room temp, either way i found all tyres were at 26psi, this isn't right is it? anyway i put the front to 33 and rears to 32psi (cold), Ive done a search and some people put their tyres up to 45, usually between 32-38 psi.

What should the tyres be at during warm and cold readings????

[R34_Wong]

A lot of factors will dictate the tyre pressure, but on my R34 GTT I run 31PSI all around when cold.

I think the weight of your car will really dictate how much you want to pump in there, but I'm definately no expert.

[blind_elk]

You will probably want at least 34 front, 32 rear (cold - always measure pressures cold). In the wet, add another 2 psi all round. (45 is way too much for normal driving.

Generally, servo gauges get the hell mistreated out of them, so buy your own tyre gauge, and use it to measure tyre pressure. It may not be correct, but it will be consistent. (although the digital BP units appear to be pretty accurate)

[Mayuri Krab]

I have some general 235/40/18 all round & I was told to fill them up to 38 to 40psi.

[Kujotk]

so im at 33/32 now so that should be fine then, thanks thats all i wanted to know

[nisskid]

for street, coming up to winter id put in around 34psi if i cbf doing anything else.

but if ur after performance, id start at 40psi cold, go for a run through the hills, find a road that isnt very populated but u know well, then go for it a few times, get a feel for it, then take out 2psi at a time until u get to low 30's (ur air will be hot now), figure out which feels best, go put ur tyres back up to 40psi, get them hot again, then go back down to the pressure u liked.

[BLKR34GTT]

As a pro in the tyre industry, we generally put about 36 to 40 psi in those sizes 235/45/17 245/45/17

[Bullet32]

There are a lot of factors that determine which pressures are best for which car, such as: vehicle weight, tyre size, driving style etc.

Generally if you want more dry traction you should run lower pressures (lower pressure means a slightly wider contact patch over higher pressure and lower pressure also heats the tyre up quicker than higher pressure)... There is a limit to how low you should go though as low pressures can cause premature wear.

I have to agree with nisskid - you should trial pressures by driving along the same stretch of road (preferably somewhere nice and twisty) and drop your pressures 2psi each time until you find what performs best for you.

P.S. Most Tyre shops will pump tyres up fairly high - this makes the steering feel nice and light (makes the customer think the tyres feel good)... You should always check your pressures after having them fitted.

[nisskid]

P.S. Most Tyre shops will pump tyres up fairly high - this makes the steering feel nice and light (makes the customer think the tyres feel good)... You should always check your pressures after having them fitted.

+1

general rule is dont take advice from tyre shops lol, i find often their knowledge is extremely limited and their real expertise is in sales.

there are exceptions to the rule obviously

[ECR-033]

+1

general rule is dont take advice from tyre shops lol, i find often their knowledge is extremely limited and their real expertise is in sales.

there are exceptions to the rule obviously

+2

Most of them only know how much psi to make a big bang with a second hand 205/65/15 and how much smoke it will make.

[writeoff]

I have my own question regarding tyre pressures so thought I'd add it to this thread.

I recently had Kumho KU36 Ecsta XS 275/35/18 fitted all around my R32 GTR ~1500kg, ~350rwkW. I had always previously used 34psi on my GTR but are these tyres considered semi-slicks and should the pressure be around 22psi? I seem to recall that was the pressure that Wheels or Motor magazine used on their semi-slicks in a tyre comparison last year.

http://kumhotyres.businesscatalyst.com/pcrku36.htm

My question is what psi should I use for daily driving? I am also going on a track day on August 25 at Mallala, what should the tyre pressures be for that day?

[nisskid]

each tyre is different, each car is different, but id be putting in around 33psi for the street.

[Bakes]

Mine are 38 PSi 275/30/19. I like how they feel, firm.

[Ultimategtr]

I have run goodyear eagle F1's 235/40/18 for 2-3 years now on 32psi and noticed VERY good traction. Havent noticed any uneven wear at all. I think 38-40psi is a bit too high - but i aint no tyre expert:) Just personal preference.

[MrStabby]

I recently had Kumho KU36 Ecsta XS 275/35/18 fitted all around my R32 GTR ~1500kg, ~350rwkW. I had always previously used 34psi on my GTR but are these tyres considered semi-slicks and should the pressure be around 22psi? I seem to recall that was the pressure that Wheels or Motor magazine used on their semi-slicks in a tyre comparison last year.

http://kumhotyres.businesscatalyst.com/pcrku36.htm

My question is what psi should I use for daily driving? I am also going on a track day on August 25 at Mallala, what should the tyre pressures be for that day?

No they're not considered semi-slicks aka R spec tyres. They're like Falken RT-615s and Federal 595RSs. I run somewhere in the 30-32 psi for road and same (cold) for track (RT-615s). At the track you want them a bit doughy when you first get on, and they will harden up as they get temperature into them. If you start too high they just get skatey as the temperature goes up. Just play with the pressures at the track as YMMV.

Mind you, with that much power you'll probably wish you were on real semis...

[SiR_RB]

okkk well after reading this il hav to put my tyres down abit in pressure, i got new 265/35/18 hankook ventus rear tyres few months bak, i checked the pressure and they were on 40psi, i for sum reason went and put 45psi (cold) in them (tyre says 50psi max wen cold)

im guessing you have to leave room for the air to expand wen they get hot?

[Bullet32]

No they're not considered semi-slicks aka R spec tyres. They're like Falken RT-615s and Federal 595RSs. I run somewhere in the 30-32 psi for road and same (cold) for track (RT-615s). At the track you want them a bit doughy when you first get on, and they will harden up as they get temperature into them. If you start too high they just get skatey as the temperature goes up. Just play with the pressures at the track as YMMV.

Mind you, with that much power you'll probably wish you were on real semis...

I hear this from people way to much these days... It is to easy to say that a tyre isnt a "semi-slick" because it isnt an 'R' compound.

The term semi-slick is simply determined by the tyre manufacturer or their marketing department to describe a tyre that has a lower void ratio than a normal "street tyre" in their range. - This term is used to describe the tyre's tread pattern.

The term 'R' spec or 'R' compound simply means that the tyre has soft compound and motorsport casing made specifically for race or track use (although many are approved for road use as well), whether the tyre is a "semi-slick" or not doesnt matter. - This term is used to describe the tyre's tread compound / casing.

Falken RT615, Kumho KU36, Federal 595RS-R, Bridgestone RE070 (factory fitment for R35), Toyo R1R - These tyres are all considered "semi-slick" but not R- spec (there are more but you get the idea).

If by saying "Real Semi's" you mean 'R' Spec tyres then you are correct, the KU36 isnt considered an 'R' Spec tyre, but it is widely considered as a semi-slick.

I hope this clears up some confusion.

[Brandon]

Bridgestone RE055 285/30/18 all round at 38psi. Dont know if this is right but feels pretty good imo.

[_Ryan_]

for street, coming up to winter id put in around 34psi if i cbf doing anything else.

but if ur after performance, id start at 40psi cold, go for a run through the hills, find a road that isnt very populated but u know well, then go for it a few times, get a feel for it, then take out 2psi at a time until u get to low 30's (ur air will be hot now), figure out which feels best, go put ur tyres back up to 40psi, get them hot again, then go back down to the pressure u liked.

depends on tyre and car, stagea is 40psi summer cold summer, 41winter, i test it hot every now and then too. digital servo gauges are my choice.

datto i used to go around 32hot

32 yet to play with new tyres...

[_Ryan_]

No they're not considered semi-slicks aka R spec tyres. They're like Falken RT-615s and Federal 595RSs. I run somewhere in the 30-32 psi for road and same (cold) for track (RT-615s). At the track you want them a bit doughy when you first get on, and they will harden up as they get temperature into them. If you start too high they just get skatey as the temperature goes up. Just play with the pressures at the track as YMMV.

Mind you, with that much power you'll probably wish you were on real semis...

They seem to be similar rubber or harder than my old RE001's on the stagea, but in a "semi slick" pattern, I have them on my GTST as the option1garage.com.au price was too good to pass up trying them out...

im guessing you have to leave room for the air to expand wen they get hot?

yes