Jump to content
SAU Community

Recommended Posts

Cue roadtrip, we meet bright and early at local BP for snacks and air.

I put 34psi in, for good firmness on open road driving (19s with a 35 profile)

Mate pulls up (r33) and puts 45psi in his (18s with 35 profile)

So after much bickering I ended up putting 38psi in my car and hoping to god I didnt have explosions on the highway, and all the while he's convincing me to put more in

I mean, christ, I'm usually a 32psi kind of guy, are my tyres going to explode? How much do you guys pump in?

32 would be fine. If I have 5 people plus their luggage i might put 36 in the back.

When i first went on the track I put 45 psi in my street tyres but they were still not up to it so i went to semi slicks and then slicks.

So no they won't explode if you put 45 psi in but there is absolutely no point in doing so. You will just wear out the middle of the tread.

I run about 38 normally...on most road tyres it wil improve handling at the cost of comfort. I don't agree that it is enough pressure to wear out the inside of a tyre, mine wears pretty evenly.

I have run tyres up to 45psi but that is specific tyres on the race track. Too high for general road use to me.

Also check the sidewalls, the tyres will hav a maximum allowable pressure which is generally 45....

mine tyres rated to 40 or 45 psi.

on the old car which were rated to 34 usually ran 36, ride felt sooo much better and direct steering.

also better to be on the rating or slightly over inflated than under inflated, less chance of tyre blow out.

can't remember what profile the girl's are, but they're 19's and we run 40 psi, checked weekly. totally even tyre wear so far.

Edited by pyro-ns
Any idea what psi I should run? 225/30/20... Sorry for hijack!

i'd put in around 36-40psi. it really depends on how much harshness you can tolerate and how the rubber reacts to certain tyre pressures. all you can really do is monitor the tread wear and make sure that it's even on all fours. all other things being neutral (camber, castor, toe), too much pressure will result in a bald spot right in the middle of the tyre and too little will result in baldness on the outside edges of the tyre.

if you find that extra pressure makes the ride too harsh (unlikely), then take a couple psi out and see how that goes. or if you've got coilovers, turn the dampner a few clicks towards soft :D

Cue roadtrip, we meet bright and early at local BP for snacks and air.

I put 34psi in, for good firmness on open road driving (19s with a 35 profile)

Mate pulls up (r33) and puts 45psi in his (18s with 35 profile)

So after much bickering I ended up putting 38psi in my car and hoping to god I didnt have explosions on the highway, and all the while he's convincing me to put more in

I mean, christ, I'm usually a 32psi kind of guy, are my tyres going to explode? How much do you guys pump in?

What was his argument for putting 45psi in? I don't get why he would want 45psi on the street....more to the point why he would want it on the open road :D. I never put more than 36-38 psi in mine on the street...shit if i want more grip in the arse on the street I drop em down.

if you run a lot of stretch you need high pressures but i never go over 40

mine are normally 36-38 for better fuel consumption (plenty of grip with the awd)

and as jetwreck said, if you want more grip on the street you would drop them down a bit, you dont really need stiff sidewalls on the street but you need more straight line grip

I would be a little careful going over 40 psi on the open road due to higher running temps. Considering Chales Law of Thermodynamics (pressure is proportional to temperature in a given volume) if your tyre temps are likely to go up then you could easily end up with a tyre pressure approaching 50psi. Apart from the obvious lowering of grip, due to less sidewall deflection and reduced contact patch, the effects of a blowout will be much more pronounced. All that risk for a possible saving of 0.1% fuel mileage doesnt really add up IMO.

Try alternating the pressures fron to rear too - a difference of only 2psi can be felt quite easlily. If you want a little more direct feeling in the steering wheel while maintaining a rear grip bias, try going 2 psi higher on the front.

I would be a little careful going over 40 psi on the open road due to higher running temps. Considering Chales Law of Thermodynamics (pressure is proportional to temperature in a given volume) if your tyre temps are likely to go up then you could easily end up with a tyre pressure approaching 50psi. Apart from the obvious lowering of grip, due to less sidewall deflection and reduced contact patch, the effects of a blowout will be much more pronounced. All that risk for a possible saving of 0.1% fuel mileage doesnt really add up IMO.

Try alternating the pressures fron to rear too - a difference of only 2psi can be felt quite easlily. If you want a little more direct feeling in the steering wheel while maintaining a rear grip bias, try going 2 psi higher on the front.

is that isothermal, adiabatic or polytropic expansion? haha

just studying for my thermal eng. exam as we speak

i'll put my money on isothermal cause it is due to heat

isothermal expansion the temp stays the same (p1v1=p2v2)

i dont think it really matters

195/70's i'd go with something normal 32-34 maybe

its a pretty high profile tyre

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • I know why it happened and I’m embarrassed to say but I was testing the polarity of one of the led bulb to see which side was positive with a 12v battery and that’s when it decided to fry hoping I didn’t damage anything else
    • I came here to note that is a zener diode too base on the info there. Based on that, I'd also be suspicious that replacing it, and it's likely to do the same. A lot of use cases will see it used as either voltage protection, or to create a cheap but relatively stable fixed voltage supply. That would mean it has seen more voltage than it should, and has gone into voltage melt down. If there is something else in the circuit dumping out higher than it should voltages, that needs to be found too. It's quite likely they're trying to use the Zener to limit the voltage that is hitting through to the transistor beside it, so what ever goes to the zener is likely a signal, and they're using the transistor in that circuit to amplify it. Especially as it seems they've also got a capacitor across the zener. Looks like there is meant to be something "noisy" to that zener, and what ever it was, had a melt down. Looking at that picture, it also looks like there's some solder joints that really need redoing, and it might be worth having the whole board properly inspected.  Unfortunately, without being able to stick a multimeter on it, and start tracing it all out, I'm pretty much at a loss now to help. I don't even believe I have a climate control board from an R33 around here to pull apart and see if any of the circuit appears similar to give some ideas.
    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
×
×
  • Create New...