Jump to content
SAU Community

Tyre Pressure

BLACKGTR33

By BLACKGTR33,
in General Maintenance

 Share

Recommended Posts

Galois Veteran

Galois

Posted
Posted

hey mate,

i have nankang ns2's on my r34 gtt, on the rear i have 265/35/r18's on 10" rims which i was told by the shop (tyrepower newcastle) should be at 40psi, on the front i have 235/40/r18's on 9" rims which apparently are supposed to be at 38psi.

i'm guessing the difference in pressure has something to do with the differing height, not sure, but the pressures have suited me okay.

the back is a handful in the rain though

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5389857
Share on other sites
Galois Veteran

Galois

Posted
Posted
^ a 235/40 and a 265/35 have the same height of sidewall.

ahh ok, what do the 35 and 40 refer to then?

You all realise your tyre pressure will rise a few PSI after driving when the tyres have heat up...

and even more for a track day or drags, or on a hot day or cold, or day and night. it'd hard to allow for all conditions tho.

back in my karting days we ran roughly 13 psi, but we'd adjust it till there was a 2 psi difference between hot and cold to find the ideal setup for the day

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5391526
Share on other sites
Munkyb0y Grand Master

Munkyb0y

Posted
Posted
ahh ok, what do the 35 and 40 refer to then?

It is the height of the tyre sidewall as a percentage of the width. ie. aspect ratio.

265/40 would be a higher sidewall than 235/40. thats why the common size is 265/35. keeping the rolling diameter similar across the 18" range. u see?

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5391698
Share on other sites
Galois Veteran

Galois

Posted
Posted
It is the height of the tyre sidewall as a percentage of the width. ie. aspect ratio.

265/40 would be a higher sidewall than 235/40. thats why the common size is 265/35. keeping the rolling diameter similar across the 18" range. u see?

i do, thanks mate, i'm still on the steep side of the learning curve lol

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5391702
Share on other sites
some_cs_student Veteran

some_cs_student

Posted
Posted
You all realise your tyre pressure will rise a few PSI after driving when the tyres have heat up...

My new tyre pressure monitoring system can see anything from 33psi to 39psi depending on weather / tyre temperature.

During warmer weather it was closer to 36 - 39psi.

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5392188
Share on other sites
Galois Veteran

Galois

Posted
Posted

before this thread gets out of hand with people asking what pressure they have for their tyre size (including myself!)

how much does a couple of psi matter? ok, so if we imagine the pressure is meant to be 40psi, for ease of numbers, and it runs at 38 psi. that's a difference of 5%, which would make fk all difference compared to other parameters, like temp, speed, cornering and driving style

and more importantly, how much does it vary between companies? because i'd imagine each company builds to it's own spec, which might vary by a few psi anyways

as a side note, my r34 was bought and after some dramatic events i checked the tyre pressure, it was 26psi, it was after that my worries about the prior owner began...

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5396356
Share on other sites
getyayayaout Enthusiast

getyayayaout

Posted
Posted

There is no one answer to this question. Ideally you want to run a tyre pressure that balances the car and feels good when you drive it. Typically tyres heat up and expand when you drive, so if you stand on the throttle at every set of lights i'd expect the rear tyres to heat up a little bit, however its mostly the front tyres that heat up more than the rears because you have the load of the car thrown forward under braking and also the fronts are constantly working harder that the rears because the turn and slide (if only slightly). Also this is in theory what could happen, in reality it doesn't make a difference when you're stuck behind a bus.

Secondly, with a gtr, I personally think you should run all four tyres with the same pressure because otherwise it may trick the g sensor into thinking you've got wheelspin.

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5399113
Share on other sites
(OO)SKYLINE(OO) Grand Master

(OO)SKYLINE(OO)

Posted
Posted
Yea. I'm running 38psi "cold" (just driving from home to servo). I'm guessing it'll be around 40psi when hot?

Yep, pretty much and when the tyres have cooled down, it will go back to 38 psi.

and even more for a track day or drags, or on a hot day or cold, or day and night. it'd hard to allow for all conditions tho.

back in my karting days we ran roughly 13 psi, but we'd adjust it till there was a 2 psi difference between hot and cold to find the ideal setup for the day

Yes, true.

I just pump an all round 34 psi and seem fine.

:)

My new tyre pressure monitoring system can see anything from 33psi to 39psi depending on weather / tyre temperature.

During warmer weather it was closer to 36 - 39psi.

:D WTF!

:)

You got any pics of that, where did you get that?

Link to comment
https://www.sau.com.au/forums/topic/332257-tyre-pressure/#findComment-5400058
Share on other sites

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
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Murray_Calavera
      R33 GTR running -9 with no tune

      By Murray_Calavera · Posted

      I don't understand how this hasn't boiled down to - Upgrade the turbo when you have everything required. ECU, injectors, fuel pump, turbo, etc. Do it all at once.  If you don't have everything required, just enjoy the car as it is and keep saving up your pennies. 
    • Duncan
      R33 GTR running -9 with no tune

      By Duncan · Posted

      Sounds like you've got an interesting adventure ahead here with local support if you have trouble! My guess is that, unboosted, you will be OK with a small upgrade like -9. What will happen is that once the stock ECU sees more airflow than it expects it will add a heap of fuel and pull a heap of timing to be safe because it can't understand how it could get that much air without there being an issue. You will see clouds of black smoke and it won't pull hard through the midrange and top end. So, overall it will be a bit frustrating but should be OK. If you are still nervous set the base timing back 2o through the CAS, but it will be even more sluggish everywhere. As said above through...this is not my guarantee your engine won't be blown into a million pieces, leaving you looking for very hard to find parts A better idea is get a computer with logging ASAP, wire in a wide band O2 sensor and a use remote tuner. I've done multiple cars this way and while it is not as good as a specific tune on a dyno they can get it 90% right. I'd suggest if you can afford an R33 GTR these days you can afford an ECU and tune. And if you can't afford that you sure won't be able to afford the rebuild if it goes bad in the meantime,.  
    • Duncan
      New kid on the block

      By Duncan · Posted

      Yeah it would be nice if someone took the time to put that sort of information together, but there are a lot of variations in looms. I think you are making this way hard for yourself if you just want to get it running....sourcing an SR20 with the right wiring will be a billion times easier than matching the RB loom to an S15 chassis. If you do end up going this way, you just need to trace every wire in the loom with a multimeter, 95% of them will go to a location you can confirm at the ECU.....and then post it up for the next person who needs it  
    • Duncan
      Coolant leak?

      By Duncan · Posted

      Just top it up with water, and keep a general idea of how much you added. It is normal for water to be pushed into and pulled out of the reservoir through the cap, and it should not be more than half full or it will be likely to overflow when hot. Any decent mechanic can do a pressure test of the cooling system to confirm if you have a leak. Keep in mind if it is only leaking a little and when hot it may well evaporate before you see it hit the ground
    • GTSBoy
      Coolant leak?

      By GTSBoy · Posted

      I'd ask the shop what they used and use that. Mixing coolants is sometimes OK, sometimes not, and you have know the details of each coolant to know whether it's a good idea or not.
×
×
  • Create New...