PSI and tyre wear

Wibbly

Registered User
So there are numerous threads here talking to experimenting with tyre pressures outside of the Audi recommendation and how that affects ride comfort etc.

For those that experiment, how does changing the pressures affect tyre wear? Popular wisdom is that a little over/under inflation would cause disproportionate centre/outside wear. Does this not occur for some reason?
 

ChivsBang

Registered User
Also interested


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Scottyg

Registered User
I've always run my tyres at 33/34 PSI no matter what the wheels/tyre size and done me know harm. I couldn't imagine sticking 39/40 PSI in my tyres. Normally get 20k plus out of set of tyres! Nearly due two fronts which are at 3.5mm after 16.5k. Rears are still at 6.5mm. I normally rotate but haven't done this time as the cars fully maintained on the lease I'm on so don't pay for tyres!
 

Flying Scotsman

Registered User
I fiddle with tyre pressures within reason. I posted asking for Audi UK recommended air pressures for 8V saloon on 19" tyres, as Audi North America only show fully loaded pressure of 44 psi on all tyres. The UK pressure for 3 passengers is what I use as a guide 42 front 39 rear and I will play around with that e.g 41/38, 40/37 41/37 etc. to find the best balance of steering feel/comfort. If I was travelling at autobahn speeds of 100-130 mph I would increase those pressures up to full load and there is not much chance of doing that on my roads.
The car is mostly driven with only 1 to 2 occupants and no other weight and would be bumped up to 44 on all four tyres with a full load.
Why do I use the lower pressures...a higher air pressure on the front tyres reduces understeer and there is a slightly more comfortable ride. Please note I check my air pressures cold every 2 weeks...tyres leak unless they are filled with nitrogen.
To achieve undue centre/outside wear, your tyres would have to be more than a little under/over inflated than the manufacturer's recommended pressures for their specified loads.
I am also willing to bet that there are quite a few cars on the road that have rarely had their tyre pressures checked. The same ones that never check their oil and complain to the dealer when the oil light comes on between oil changes.
 

paulmc

Registered User
I Run around 32psi. Never any issues with wear. going high (40 ish) makes the car too hard.
 

Gugne

Registered User
tyres leak unless they are filled with nitrogen.

The air we breathe and the air in your tyres is 80% Nitrogen 20% Oxygen. The N molecules will still leak but at a slightly slower rate than the oxygen because the molecules are larger so you'd still need to check your tyres.
Also unless the inside of your tyre is in a vacuum I'm not sure how they would replace all of the Air with pure Nitrogen when filling it.
 

allanmb

Registered User
I used to get lots of wear at the edges of my tyres so I overinflate mine and now get a more even wear. I ran my previous A4 Quattro at 40PSI each corner and got 18k miles out of them. I think the recommended was 34-38 depending on load
 

4K

Registered User
Anyone noticed a discernable difference in the 'bouncyness' with your change in pressures? (Non-magride owners only)
 

allanmb

Registered User
Anyone noticed a discernable difference in the 'bouncyness' with your change in pressures? (Non-magride owners only)

It's bouncy but then again I've only had them pumped up high. I'd imagine you'd need to go superlow to get rid of the bounciness
 

Bells

Registered User
Didn’t want to start a brand new thread so thought I’d post in here, had my car in for some warranty work today and the health check report brought up my tyre wear, no recommendations but I noticed my tyre wear seems a little uneven on the front.

Front left is showing as 47% worn (4.8mm) and front right 62% worn (4.00mm). Inner tread depth is the same on both at 4.8mm but then it starts to vary with outer tread depth being the biggest difference.

Question is, is there a problem do I need my tracking done due to the uneven wear? Also, what is the tolerance for tread depth on Quattro cars will 0.8mm fall within this?
 

Adam14

Registered User
Also, what is the tolerance for tread depth on Quattro cars will 0.8mm fall within this?
1.6mm is what I was told when I bought my S3. So 0.8mm would be fine.
 

Matt Titanium

Registered User
Didn’t want to start a brand new thread so thought I’d post in here, had my car in for some warranty work today and the health check report brought up my tyre wear, no recommendations but I noticed my tyre wear seems a little uneven on the front.

Front left is showing as 47% worn (4.8mm) and front right 62% worn (4.00mm). Inner tread depth is the same on both at 4.8mm but then it starts to vary with outer tread depth being the biggest difference.

Question is, is there a problem do I need my tracking done due to the uneven wear? Also, what is the tolerance for tread depth on Quattro cars will 0.8mm fall within this?

Mine do the opposite, Front left 1.6mm, 100% worn, front right 2.7mm, 78% worn and the rears only 1mm more tread left than the fronts. I blame it on the roundabouts. The car has only done 13k so I won't be buying Bridgestones again. I got 23k from the P Zeros on the front of my last A3
 

Svenedin

Registered User
I raised my tyre pressures from the part-laden values to the fully laden values when I drove across Germany (mainly Autobahn) to Austria recently. I used the values on the sticker on the inside edge of the driver's door. I found the higher tyre pressures were firmer (as you might expect) but it seemed to make the "floaty" feeling worse at high speeds (100 mph+). I didn't like the fact that the steering felt imprecise and the car skittish. That is not a good feeling when belting along.
 

KenL

Registered User
I don't see any reason to not use the values recommended by Audi. I'd imagine that they have spent time looking into what is best for the car.

Are the people who have uneven wear on the front pulling out of left turn junctions too quickly???
 

lledwoc

Registered User
I don't see any reason to not use the values recommended by Audi. I'd imagine that they have spent time looking into what is best for the car.

Are the people who have uneven wear on the front pulling out of left turn junctions too quickly???

Pressures that are best for emissions tests...
 

AlS3BE

Registered User
Standard pressure are set for your average joe.
Best grip, emmisions, and wear and a whole list of stuff that your average joe cares about.
Enthusiast like most on this forum plays about with them to find what’s best for yourself and driving style.
Also if I did a lot of motorway miles a few less psi is better for wear especially in the centre tread.
If you drive a lot of long distance it’s probably best to lower pressures as the tyre builds up heat and naturally increases pressure which will wear the centre faster. Similarly a few extra psi if you constant drive around town as the outer edges takes more a beating. This helps even wear.
You should set it different for different occasions or keep the Audi standard as the half way point.
Other option is pure nitrogen fill as pressure doesn’t vary as quickly or as bad as normal air. The only thing is to do it right you need to suck all the air out and fill it with pure nitrogen otherwise it’s a waste of time/money.
 

Matt Titanium

Registered User
Other option is pure nitrogen fill as pressure doesn’t vary as quickly or as bad as normal air. The only thing is to do it right you need to suck all the air out and fill it with pure nitrogen otherwise it’s a waste of time/money.

Would filing the tyres with helium reduce the unsprung weight and improve suspension control? Or are helium molecules so small that they would escape through the rubber like oxygen? Or are nitrogen filled tyres all a big confidence trick that some tyre places pull to extract an extra £10 a corner out of the gullible?
 
Or are nitrogen filled tyres all a big confidence trick that some tyre places pull to extract an extra £10 a corner out of the gullible?
Yup.

I'm sure that if you cough up whatever it costs to have the percentage of nitrogen in your tyres increased from the standard fit 78% to a nominal 100%, complete strangers will be falling over themselves to buy you an expensive Belgian beer in a poncy glass and be hanging on your every word once the wine bar conversation turns to anything with carbon fibre mirror caps and extended mono.pur.

It can't do any harm - if you put aside the deleterious effects on your wallet, that is - but it's going to make things mighty inconvenient further down the road.

Every time you need your fireproof tyres topping up you won't be able to use regular old fresh air.

No Sir.

That'll dilute the nitrogen see, Sir, and your car won't drive in a straight line any more, Sir, because one of the tyres has got some air in it and you'll have to watch it like a hawk Sir, else it'll either swerve off the motorway by itself or that tyre will get hot and explode and just think what might happen to your children and your lovely wife, Sir.

And your wife is really lovely, Sir.

Especially in that summer dress.

Have you noticed how the light shines through it, Sir?

So you'll have to traipse all the way to the 'inflation specialist' to have it done for you while you sit in a waiting room that still smells of stale fags even though the smoking ban is years old, and the only entertainment is either an ancient and well-thumbed copy of Nuts or last week's local rag with half the small ads and take-away curry house numbers torn out.

It'll cost you extra in fuel to get there as well, since it's highly unlikely that your tyres will lose any of their precious gas at the same time you just happen to be passing.

And what happens if, heaven forbid, you go outside one morning to find one of your tyres looking too soft to drive on?

What do you do then?

Panic, that's what you do.

You spill your expensive hand-ground Ethiopian coffee all over your slacks and your patent loafers and flap your hands helplessly like a nun who's just seen up the window-cleaner's shorts by accident.

I suppose you could always call the AA or the RAC on the off-chance that they might have a cylinder of nitrogen in the back of the van, but really.

How could you maintain the tiniest shred of credibility if you ring them up and say that you can't put air in a soft tyre because air has got 22% other things in it, and the 'tech' with steel toecaps at the tyre specialist says it won't be safe to drive?

Good old-fashioned air.

That's what you need.

Good old-fashioned air full of the smells of freshly-cut grass, Castrol R, autumn bonfires, newly-laid tarmacadam, home-baked bread, sizzling bacon, the nape of your baby's neck and old leather furniture.

And a footpump.

The same sturdy old footpump that your grandad used to use to blow up the crossplies on his Rover 90 while the Player's No10 in his lips was nothing more than a filter and a long curve of ash that never fell off.

.
 

Matt Titanium

Registered User
Yup.

I'm sure that if you cough up whatever it costs to have the percentage of nitrogen in your tyres increased from the standard fit 78% to a nominal 100%, complete strangers will be falling over themselves to buy you an expensive Belgian beer in a poncy glass and be hanging on your every word once the wine bar conversation turns to anything with carbon fibre mirror caps and extended mono.pur.

It can't do any harm - if you put aside the deleterious effects on your wallet, that is - but it's going to make things mighty inconvenient further down the road.

Every time you need your fireproof tyres topping up you won't be able to use regular old fresh air.

No Sir.

That'll dilute the nitrogen see, Sir, and your car won't drive in a straight line any more, Sir, because one of the tyres has got some air in it and you'll have to watch it like a hawk Sir, else it'll either swerve off the motorway by itself or that tyre will get hot and explode and just think what might happen to your children and your lovely wife, Sir.

And your wife is really lovely, Sir.

Especially in that summer dress.

Have you noticed how the light shines through it, Sir?

So you'll have to traipse all the way to the 'inflation specialist' to have it done for you while you sit in a waiting room that still smells of stale fags even though the smoking ban is years old, and the only entertainment is either an ancient and well-thumbed copy of Nuts or last week's local rag with half the small ads and take-away curry house numbers torn out.

It'll cost you extra in fuel to get there as well, since it's highly unlikely that your tyres will lose any of their precious gas at the same time you just happen to be passing.

And what happens if, heaven forbid, you go outside one morning to find one of your tyres looking too soft to drive on?

What do you do then?

Panic, that's what you do.

You spill your expensive hand-ground Ethiopian coffee all over your slacks and your patent loafers and flap your hands helplessly like a nun who's just seen up the window-cleaner's shorts by accident.

I suppose you could always call the AA or the RAC on the off-chance that they might have a cylinder of nitrogen in the back of the van, but really.

How could you maintain the tiniest shred of credibility if you ring them up and say that you can't put air in a soft tyre because air has got 22% other things in it, and the 'tech' with steel toecaps at the tyre specialist says it won't be safe to drive?

Good old-fashioned air.

That's what you need.

Good old-fashioned air full of the smells of freshly-cut grass, Castrol R, autumn bonfires, newly-laid tarmacadam, home-baked bread, sizzling bacon, the nape of your baby's neck and old leather furniture.

And a footpump.

The same sturdy old footpump that your grandad used to use to blow up the crossplies on his Rover 90 while the Player's No10 in his lips was nothing more than a filter and a long curve of ash that never fell off.

.

I'm sure some places do free nitrogen top-ups for the life of the tyre if you pay an extra £5 on the top of the extra £10 for nitrogen when you have your tyre fitted. They'll even throw in a set of those nice shiny little hexagonal monkey metal valve caps that weld themselves on after three weeks.
 

Adam14

Registered User
Get your tyres done at Costco. Nitrogen is free

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ictus_duplo2

Registered User
Just replaced my factory fitted 18 inch Hancook's which I ran at 35 - 38 psi. After 15k miles and rotated once they were well above legal approx 3 and 4mm and could of got another 5k miles out of them.

Putting on Michelin Pilot Sport 4's has transformed the car and I wish I had done it at the start of the summer. Car holds a line while steering, rides smoother and road noise is not so intrusive. Even when the car was new did not feel so precise.
 
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