Tyre pressures, I'm going to ring Audi and ask but...

DorsetDude

DorsetDude

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Hi
I have a 2009 reg A3 (no, im not a hairdresser, thanks for asking) 2.0 TDI S-Line. The tryes on it are low profile. 225/40 ZR18 to be exact.
The little panel behind the petrol flap only has one entry for profiles that low and its for a 225/40 R18 92Y XL and says normal load 42psi front and 36 psi rear.
The exact spec on my tyres is 225/40 ZR18 92W.
No "XL" bit. Are these pressures the ones I should be using?
I checked yesterday and all my tyres were at 24 which I thought was a bit low so I inflated them to 37 front and 34 rear. (Didnt have my glasses at the garage and couldnt see the little panel properly. Doh)
Im hoping once I get them right my mpg will improve a bit.

In general, are low profile tyres inflated to higher pressures than "normal" tyres?
 
The XL means "Extra Load" which is to do with sidewall strength and doesn't affect the pressure the tyres need to be inflated to.

If the panel says 42/36 then that's what you should go for

Without wanting to teach granny to suck eggs here, the profile part of the tyre size is the "40" bit. It means the side wall height is 40% of 225 which is the width of the tyre in mm. The 18 is the diameter of the wheel, the letter after that related to the speed rating and the number is the load which is then backed up by XL if it's an Extra Load tyre.
 
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Forbiddenbiker said:
You should find the recommended tyre pressures for different tyre types written on the side of each tyres wall. :thumbs:
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I've never seen recommended pressures actually on the tyre - do you mean maximum rated pressure?
 
Cheers all. Just got off phone to audi and after some confusion Ive got 2.8 bar front and 2.5 rear (my plate on the door says 2.9 front 2.5 rear) So I'll go for 40psi front and 36 rear I think. Could be lumpy.
 
The higher pressures on the front relate more to the fact that your car is front wheel drive plus being the Diesel version could be 50kg heavier than its petrol equivalent and hence why the manufacturer may have recommended the XL type tyres to cope with the extra weight.

On a side issue, when tyres are replaced, its fairly common place for car owners/garages to use similar sized tyres that may not exactly match the manufacturers original equipment [or in some cases the exact tyres may not be available to purchase] - i.e. in your case the non XL and the different speed rating W instead of Y. It may be prudent to advise your insurance company just in case of any potential disputes in the event of having to submit a claim as most policies have a term that says you should maintain your car to the manufacturer's recommendation.
 
Sounds a bit more like it though - 24psi was definitely too low. It'll be interesting to see if you notice any difference in fuel economy. And you'd better make sure you warn any denture wearers that travel with you :)
 
Forbiddenbiker said:
You should find the recommended tyre pressures for different tyre types written on the side of each tyres wall. :thumbs:
Click to expand...

As others have said, that may be the case for bikes & motorbikes but a car tyre would only have maximum pressure that's relevant for the tyre itself, not the car.

The reason being some cars are heavier than others to the tyre pressure needs to take this into consideration. As lotsoulal2 said, you normally find diesels need more pressure in the front tyres because the engines weigh a fair bit more than the petrol equivalents.

As well has having different pressure for back/front tyres, most cars will also have a rating for "normal" (generally up to 3 people and light luggage) and load carrying (5 people and luggage). There can be a big difference between the two sets of pressures too.
 
lostsoulal2 said:
On a side issue, when tyres are replaced, its fairly common place for car owners/garages to use similar sized tyres that may not exactly match the manufacturers original equipment [or in some cases the exact tyres may not be available to purchase] - i.e. in your case the non XL and the different speed rating W instead of Y.
Click to expand...
The W and Y is not a speed rating apparently. Its the load rating. Ive been speaking to Audi and the engineer didnt pipe up and scream when I gave him the details so cant see a problem there. no harm in checking as you say. The speed rating is the letter before the "18", ie. R18 or ZR18

It may be prudent to advise your insurance company just in case of any potential disputes in the event of having to submit a claim as most policies have a term that says you should maintain your car to the manufacturer's recommendation.
Click to expand...
This is the real world however and as it's near as dammit I shant bother.
 
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The W and Y are speed ratings - the bloke at Audi was wrong if he referred to that as load ratings

W is rated up to 168 mph
Y is rated up to 186 mph

The 92 is the load rating 630 kilos vs the 580 kilos offered by the 'standard' 89 load rating.
 
I see you are correct. Most odd. However, 168mph in that case then is more than adequate. What with a top speed of 129mph.

The "R" is for radial, as opposed to crossply, apparently. So wonder what ZR means?

Cheers.
 
Quote: "Back in the early 1970s the available codes were SR (112 mph, 180 km/h), HR (130 mph, 210 km/h), VR (in excess of 130 mph, 210 km/h) and ZR (in excess of 149 mph, 240 km/h). The ZR code is still in common use, often combined with a W or Y speed code.
 
Russ77 said:
As others have said, that may be the case for bikes & motorbikes but a car tyre would only have maximum pressure that's relevant for the tyre itself, not the car.

The reason being some cars are heavier than others to the tyre pressure needs to take this into consideration. As lotsoulal2 said, you normally find diesels need more pressure in the front tyres because the engines weigh a fair bit more than the petrol equivalents.

As well has having different pressure for back/front tyres, most cars will also have a rating for "normal" (generally up to 3 people and light luggage) and load carrying (5 people and luggage). There can be a big difference between the two sets of pressures too.
Click to expand...


Okay, :thumbs: same for bikes with load's and codes and stuff btw.

I was assuming the correct load rating of tyre was going to be pumped up.
 
DorsetDude said:
Hi

I checked yesterday and all my tyres were at 24 which I thought was a bit low so I inflated them to 37 front and 34 rear.
Click to expand...

The tyres maybe ok but letting them driving them on low pressures destroys the inside of the tyres. You end up with granules of rubber rolling around inside the tyre. If this has happened the tyre needs replacing.
 
nilagin said:
The tyres maybe ok but letting them driving them on low pressures destroys the inside of the tyres. You end up with granules of rubber rolling around inside the tyre. If this has happened the tyre needs replacing.
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I'm fresh out of tyre x-ray equipment unfortunately so I wont be able to tell. :p
 
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Just for your comparison, I used to have a 2009 A3 5 door Sportback 2.0TDi (may be slightly bigger than the S-Line) and that did a little above 50mpg without trying, I do about 70-80 miles a day with some motorway and 'A' roads but let's just say I wasn't hanging about. Also had the climate control on all the time with the AC.
 
Go with pressures that it says in the book.

24psi is quite low for any car, even my 2.0 Clio runs 33/30.
 
PaulF said:
Just for your comparison, I used to have a 2009 A3 5 door Sportback 2.0TDi (may be slightly bigger than the S-Line) and that did a little above 50mpg without trying, I do about 70-80 miles a day with some motorway and 'A' roads but let's just say I wasn't hanging about. Also had the climate control on all the time with the AC.
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:'( My average is 44. Was hoping for more.

Although my 11 mile commute seems to be sitting in traffic queues for about 5 miles of it. Once, in the summer when the schools were off, and the roads were uncharacteristically clear I got 62mpg. If only that was everyday.
 
JamesBryan said:
Go with pressures that it says in the book.

24psi is quite low for any car, even my 2.0 Clio runs 33/30.
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Standard pressures for a Hillman Imp on radials are 18psi front, 30psi rear.

Yes, it does confuse the fitters in tyre places when I ask if they are trying to kill me by putting 30+psi in the front tyres.
 
onomatopoeia said:
Standard pressures for a Hillman Imp on radials are 18psi front, 30psi rear.

Yes, it does confuse the fitters in tyre places when I ask if they are trying to kill me by putting 30+psi in the front tyres.
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Maybe I should have said most modern cars haha
 
Lowest tyre pressures I needed were about 21 and 24 for the vitesse. Usually had to let them down from 28 psi if a garage had been anywhere near it...
 
srichards said:
Lowest tyre pressures I needed were about 21 and 24 for the vitesse. Usually had to let them down from 28 psi if a garage had been anywhere near it...
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You had a Vitesse? Will admit to some jealously there, have always hankered after one.
 
onomatopoeia said:
You had a Vitesse? Will admit to some jealously there, have always hankered after one.
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My first car was a convertible Herald 13/60 - it was all I could afford. At the same time, my friend (we were both 16) bought a convertible Vitesse and he and his Dad spent many hours and £££s restoring it to like new condition. He failed his test 3 times, gave up and doesn't drive to this day. But 35 years later that restored Vitesse still sits in his Dad's garage and has never been used. I don't know what it might be worth now - it's peak was probably in the 80s? Lovely car, although I always fancied the TR6.

Whoops - sorry DD
 
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onomatopoeia said:
You had a Vitesse? Will admit to some jealously there, have always hankered after one.
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Yes, had one until about 2 years ago. Had to sell it :(

Mint cars are worth more now than they used to be. There seems to be only two price points. Mint and everything else. Everything else just gets banger money.
 
nilagin said:
It's well worth having the tyres taken off to check. If they have started to break up inside the consequences could be fatal.
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Agree, especially if you ran that pressure for any long/fast journeys. Because the pressures were lower the sidewalls flex more, which combined with heat building up (also due to sidewall flex) can

A local garage should charge a tenner a corner, maybe less, to check.
 
I can't believe it's got to 30 posts on tyre pressures when the OP answered his own question in the first post...

"The little panel behind the petrol flap only has one entry for profiles that low and its for a 225/40 R18 92Y XL and says normal load 42psi front and 36 psi rear"

That's near enough.
 
Have a read of those posts, it may help with your belief system... ;)
 
I did. I still think it's being made massively over complicated :)
 
Keith, if the tyres haven't been run below 24 psi, you do not need to worry about the carcass rubber having shredded!

Tyres aren't the only round objects being spoken here :naughty:
 
I`m glad some body started this thread,my car has a sticker that says diesel on the petrol flap. This has confused me somewhat, I know the engine is a diesel, yet the sticker is on the petrol flap. Can somebody hold my hand through life and tell if I should put petrol through the petrol flap or diesel in the tank beyond aforementioned flap?

Why are things so confusing?
 
fracster said:
I`m glad some body started this thread,my car has a sticker that says diesel on the petrol flap. This has confused me somewhat, I know the engine is a diesel, yet the sticker is on the petrol flap. Can somebody hold my hand through life and tell if I should put petrol through the petrol flap or diesel in the tank beyond aforementioned flap?

Why are things so confusing?
Click to expand...

Oh dear!
Obviously you need to write to the manufacturer to ascertain the correct course of action. I couldn't possibly comment...
 
fracster said:
I`m glad some body started this thread,my car has a sticker that says diesel on the petrol flap. This has confused me somewhat, I know the engine is a diesel, yet the sticker is on the petrol flap. Can somebody hold my hand through life and tell if I should put petrol through the petrol flap or diesel in the tank beyond aforementioned flap?

Why are things so confusing?
Click to expand...

No confusion in this thread - just people trying to answer a perfectly reasonable question from the OP and being civil to each other. Perhaps you need to spend a bit more time in your truck.
 
I agree, no confusion at all. The question was answered in post number one.
 
But the question wasn't answered in the original post, was it. He'd changed the tyre specification so the question was did that affect the pressures. Turns out it it didn't. Unless you're suggesting there needs to be some sort of filtering in place to make sure questions are of a certain standard?
 
Sense of humour failure by some........affirmative.
 
Ah, didn't realise it was humorous - I just thought it was a sarcastic dig at the OP. Perhaps a smiley or two would have helped but I'll know now for the future :thumbs:
 
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