Tyre Pressures?

[azzamntriton]

I'm at a loss... Firstly if I have re hashed a question that has already been asked, I apologise, I had a look and did not find the answers to the questions I am about to ask.

I am at a loss. I had my MN lifted with a Dobinson 40mm lift and also a wheel alignment was carried out but I have noticed that the steering is really twitchy, its really scary.

I pulled into the servo and checked my tyre pressures they were all at 40psi (I dont know what they were set at originally as my car is only 11000 km old and I have never checked the tyre pressures). Could the tyres have been raised to 40 psi from 29 psi when the wheel alignment was done?

I have dropped them to 36psi in the front and 38psi in the rear but am still not sure if I have done the correct thing. Car still is quite twitchy at 110 km/h it is as if there is no free play in the steering. I have the standard Bridgestone H/T Dulers 245/65/R17. The tyre placard states to run them at 29psi but that seems a little to low to me. Any suggestions would be greatly appreciated.

Should I have done something else to the steering when raising my car?

Please help

Once again sorry if I have re hashed an old post.

Regards
Jason

[Cowboy Dave]

I have found it is fairly typical to have a tyre place put the tyres at 40psi all round - that could easily have been done when you're alignment was done. Try dropping 2 psi at a time until you're happy with the feel of it. 38 is still pretty stiff. If you're towing or carrying a load then I wouldn't have a problem with 40 in the rear though. They also reckon higher pressures for freeway or extended high speed work. Could be worse mate, my dealer had mine at 50 psi all round when I collected mine.

[Homer]

Yeah it will come back from dealer services like that too...generally.

34 psi is about right. Gets rid of most of the bump steer/skittishness

[ash248]

34-38 psi your in a good range I worked in a dealership and they used to put the pressure a little higher at times because people would never check there tyres and be up for new tyres at 30,000km.(passenger cars)

But 50psi is cray sounds like you got the apprentice Dave

[Hymie]

Check the tightness of your wheel nuts.

I broke 2 studs on the front right when I changed my play set off the car, and in between it happening and getting the studs the steering felt quite dangerous at anything above 70Ks. I replaced the studs and it came good straight away. I can't explain why it felt like it did.

If they damaged even 1 of the wheel studs it could explain what it is doing.

[snowman]

i would get the wheel alignment checked.

i have had plenty and i reckon only one was done right. particularly after the lift.

the incorrect caster and or toe can give a flighty or twitchy feel.

Don't assume that as it was recently done it is right. The sussy should be tightened after 1000klm so get the alignment redone after that - probably somewhere else.

read here;

http://www.ozebiz.com.au/racetech/theory/align.html

[azzamntriton]

In relation to the wheel studs is there a certain Torque that they should be set at? I can then compare and check this. And in relation to the 34 psi in my Tiers is that for my size wheels? I really appreciate everyones help. Thanks.

[Joe]

He's talking about his H/T Duelers guys. I would only be running them at 29psi which as the placard says is the correct pressure.

If you're running light truck ATs or muddies, then the higher pressures are appropriate.

Use a torque setting of 128ft-lb for the alloys and 140ft-lb for steelies.

[Homer]

Good post Joe.
From memory I lowered mine until at about 32psi I found the bump steer gone so left them around that. Didn't read the placard

I generally try to keep them slightly over inflated to minimise wear but wouldn't do it if the skittishness/bumpsteer started again. It's dangerous.

[biggibbo]

Factory H/T's, as Joe said run them at 29 psi.

[snowman]

in my opinion 29psi is too low for the standard rubber.

[biggibbo]

in my opinion 29psi is too low for the standard rubber.

I ran 29 cold and found they got up to 33 once I hit the c/coast. They wore evenly and were comfy to drive on. Guess it depends on how far you drive. I cover 135km each way to work so 29psi was perfect for me.

[coxy47]

As a good guide line after driving for a period of time (30min to an hour) your tyres should b 4psi higher then when they are cold.

If they increase by more then 4psi your starting pressure is too low. If they increase by less then 4psi then your starting pressure is to high.

[Homer]

^^good post

[azzamntriton]

Thanks everyone. I'll give it all a try. Hope I have not annoyed anyone with my questions.

Once again many thanks!
Jason.

[Froggy]

As a good guide line after driving for a period of time (30min to an hour) your tyres should b 4psi higher then when they are cold.

If they increase by more then 4psi your starting pressure is too low. If they increase by less then 4psi then your starting pressure is to high.

Interesting information!
I'll try that!

[snowman]

in my opinion 29psi is too low for the standard rubber.

I ran 29 cold and found they got up to 33 once I hit the c/coast. They wore evenly and were comfy to drive on. Guess it depends on how far you drive. I cover 135km each way to work so 29psi was perfect for me.

I don't disagree with you but i don't do the F3 speeds you do (heat) or the distance, so for a lot of around town stuff i still think 29 might be a little low. However, i will do the 4PSI test as well.

i know this was about OEM but i was consistently getting poor wear at mid 30's on my muddies. I run my OEM at high 30's and will admit that it gets a bit bumpy but apart from shite wheel alignments i have been getting pretty even wear across the face.

[trouble]

cooper ST's 36psi all round wear is great and ride is fine.

[chopper]

This could have nothing at all to do with pressures of course, a 40 mm lift is a big deal and changes lots of angles.

How reputable was the installer? What sort of kit did they use?


----
http://Www.p7offroad.com.au

[azzamntriton]

The installer is a one man show with an apprentice. Nice fellas both of them. I had a dobinsin lift kit installed with greesable shackles. Along with a snorkel and 125 lt fuel tank. Nice clean work shop, heaps of 4WD veh in shop being worked on. I had to wait 3 weeks to get my car in for the mods. I've reduced the tyre pressure to 30psi, it's made a huge difference. What else could be the issue? I'm new to all this so any help would be greatly appreciated.
Regards Jason.

[tukadafoonday]

Just looking at the first post you said you put your front tires lower than your rear? Make your fronts 35 and your rears 28 and see how that goes... Remember the ute is very light and will become ruff as guts with high pressure and no weight in the back... I run 40 front and back and it's like driving on the old stone wheels...

[Big T]

Hi Everybody,What is the tyre pressure as there is no readings on the original equipment tyre wall.And also what would everybody suggest for pressures with a load etc.Cheers Tony

[ag9111]

Look on the tyre placard, mounted on the B pillar inside the front driver s door

[krazed]

Look on the tyre placard, mounted on the B pillar inside the front driver s door

This!

[rhodes96]

The B pillar placard tyre reccomendations are what the the manufacturer state as what's optimium for tyre tread contact (grip). Those tyre pressures mean a faster wear pattern and a quicker turnover of a new set of tyres.

I have played around with the tyre pressures over a 1600km round trip at the end of last week.
I have found that 37 to 38 psi all round when cold to be sweet spot on a unloaded to lightly loaded glxr triton running factory tyres and rims. The tyres were tested in conditions from light mud to dusty tracks and tarmac roads at high speed. Pretty good for tactory tyres and pretty stable at high speed with minimal road noise.