Different size profile on rear/front tyres

[huntygowk]

Hi,

I bought 2102 A6 C7 3.0 Tdi Quattro S-Line last week.
I really like the car, except for the awful 'Quattro crawl' I experience turning at low speeds. I've asked around and everyone thinks this is normal for quattro. It might be normal but it's taking a bit of getting used to.

I've only just got out today because of the weather to be able to wash car and dress wheels etc.
When dressing the wheels I noticed the tyres on front and rear are not the same profile.
Front 245/40/R18/93Y - Firestone Firehawk SZ90
Rear 245/45/R18/100Y - AVON ZZ5

So two questions.

1) Is it ok to have front and rear tyres with different profiles?
2) Could this different in profile exacerbate the 'quattro' crawl I'm experiencing?

Thank you in advance for taking the time to read and reply!

Euan

2102 A6 C7 3.0 Tdi Quattro S-Line

[zollaf]

tyres must be very close in overall diameter, even new tyres one end and worn the other will make it feel funny and upset the centre diff. yours are miles out, next stop for me would be somewhere to fit at least 2 new tyres, and yes, this will very much make the scrubbing when turning worse. in fact i wouldne even be driving it like this... very bad.

[huntygowk]

Thanks for the reply zollaf.

Your advice fits with what I'm thinking as well.

In your opinion, if a dealer has sold a car like this with different profile tyres, is it something I'd be justified in asking them to replace?

I'm going to do it regardless of what happens but am interested if I might have a some justification in asking them.

Cheers

[zollaf]

hell yeah, i would be taking it straight back to them.

[M1tchy]

Never disagreed with zollaf and this was about to be my first, but had to have a re-read and then noticed the 40/45 bit.

I now agree with zollaf and would get them changed. I'd check the sticker in the drivers door and get them matched to that.


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[huntygowk]

Thanks for the info M1tchy.

I'll be on the phone to them tomorrow.

Here's the thing though. I don't know how long these tyres have been on the car. They look pretty new and tread depth is good both 8mm,7mm,8mm. If the car has been getting driven on them for a while , and maybe older tyres before these ones were the wrong size too, who knows, what could the impact be on the diff other parts of the transmission etc?

Should I be concerned about potential damage elsewhere?

Cheers

[zollaf]

Tyre sizes in Quattro cars DO matter ( vibrations and studdering) - LONG | Audi Forum (http://audiforum.us/threads/tyre-sizes-in-quattro-cars-do-matter-vibrations-and-studdering-long.15764/)

this bloke had the same mix of tyres... only a vibration but could alos lead to damage to the torsen diff.

[M1tchy]

That's a zollaf problem [emoji23][emoji23]
Beyond my knowledge I'm afraid


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[huntygowk]

Ok,

That's a useful link cheers.

Am going to get it checked out by my local indie Audi servicing garage and see if there's anything obvious wrong, then get on to the dealer fully armed!

Thanks for the help

[zollaf]

technically a torsen diff can handle a slight difference like this, its only like the car is driving in a circle, but they do prefer to drive in a straight line, hence the scrubbing you do get on corners. its a quaiffe style diff, lots of funny shaped gears that transfer the power to the wheel with the most grip, unlike a normal diff that transmits it to the wheel with the least grip. really complicated technology but purely mechanical. but after 10,000 miles of driving the diff may object, but may not, but if it does you are looking at a huge repair bill. this is why audi say to keep the same size , make and model of tyre with roughly the same amount of tread on all 4 wheels. sure there are folk running about with different sized tyres with no problem.
incidentally if it was a haldex, the electronic fluid coupling as found on transverse engined cars, golf 4 motion, a3, freelander etc, it would have probably died by now, but they are not proper 4 wheel drives.

[huntygowk]

I won't pretend to understand everything you mentioned, but I get the gist of it. You know your stuff!

I'm hoping that the front tyres were put on recently, and the dealer effed up and put the wrong size on. I've only done about 400 miles since I got the car last week. It's got 57000 on the clock.
The fear factor is if it's been running the wrong size because somebody in it's 5 year past decided to put the wrong size on the front and no telling when it happened.

'If' there is a problem with the diff is there anything obvious I should be looking out for when driving?

[zollaf]

any vibration or clunks really. thats the only way to tell, or any noise , whining etc. chances are its only just had them, hopefully...

[huntygowk]

Ok, thanks again for your help, much appreciated.

I don't recall hearing any other noises etc other than the vibration turning at low speeds. Here's hoping

I'll be dropping the car off on Monday to get looked at.

[fest0r]

Correct size/rating for standard s-line 18” wheels is 245/45 R18 100Y. I would be looking for the dealer to provide a very recent receipt for the Firestones and a lengthy warranty on related components before I considered keeping the car. It may be excessive, but I don’t even like using different tread patterns (rolling resistance etc.) so I would ask for the same model of Avons for the front too. Easy for me to say, but I would reject the car if they can’t show when the Firestones were fitted. The previous owner might have had all sorts on there if it wasn’t the dealer.

Apart from going against specific manufactures requirements there are also insurance implications. Was it an Audi dealer?

I can’t find the thread, but I remember someone posted the maximum allowed variance a few years back and it was 3mm for my tyres which are the same as yours. Throw a depth gauge on the rears to make sure whatever you get on at the front will be OK.

[bbrown1664]

I have seen an issue on a mercedes where the cruise control wouldn't work above a certain speed due to different size tyres fitted on each axle.

[A6S]

Surely this difference would have knocked out the abs, traction control and tpms. It would be like driving with a flat up front. My tpms has thrown a light with 1 tyre at 26-7psi which isn't that low.
The 40 profile most likely came off another car, A4/5 as far as I know has a lower profile but different offset.
Would probably go as far as checking if the wheels are the correct ones with the right offsets and width.

[bbrown1664]

According to this site, the difference in rolling radius would have been nearly a centimetre. Enough to cause some problems.

Tyre overall rolling diameter (http://www.errolstyres.co.za/content/tyre-overall-rolling-diameter)

[huntygowk]

Hi,
Cheers for all the advice, lots of good info here.

I've not had any warning lights go off. The only thing I'm experiencing is the bad quattro crawl at low speeds /tight cornering. I am noticing a lot of road noise/grumbling when driving but to be honest I'm maybe just being paranoid now. I'm going to speak to my local audi indie garage tomorrow, I've used them for years, and will be contacting the dealer once I'm sure what I want from them.

I know I want to find out when the wrong fronts were put on the car but whatever the garage tells me I'm still not going to know for sure what's happened as I'll be surprised if they have wheel history for the last five years.

At very least I want two new avons for the front (have checked rear tread depth and are 6,7,6) and either a full check of transmission to identify if there are any problems or five year extended warranty on the transmission.

I'll post how I get on.
Cheers

[fest0r]

Just keep in mind you might not be insured at the moment… even a lazy assessor will check the tyres.

[huntygowk]

Ah good point. I'm not driving tomorrow, on my bike, so will be ok. Once I've figured out what's what with dealer I'll get in touch with insurance company. What a pain in the...!

[huntygowk]

Local garage confirmed all of what's been said here, just no way of knowing if any damage or undue wear on the transmission unless sent in for some kind service.

I've spoken to the dealer and they had down that the tyres were all 245/40/R18's. They're looking into how the different sized ones appeared on the front.

[fest0r]

Local garage confirmed all of what's been said here, just no way of knowing if any damage or undue wear on the transmission unless sent in for some kind service.

I've spoken to the dealer and they had down that the tyres were all 245/40/R18's. They're looking into how the different sized ones appeared on the front.

That’s even more worrying then. Have you checked the tyre sticker? I’m sure they should be 245/45/R18 :confused:

[huntygowk]

Yes I checked yesterday, the tyre sticker on the door does indeed say 245/45/R18

They said the car came in with those tyres. How they marked them all down as 245/40/R18 might be because they just looked at the fronts and assumed all were the same. Sloppy.
Anyway, am waiting to hear what they come back with to me tomorrow regarding how long they've been on etc and I'll take it from there.

[zollaf]

i would push for 4 brand new tyres of your choice.... and extended warranty on the diff and gearbox.

[huntygowk]

Yeah I agree. I'm not going to be happy with the one year warranty even with new tyres now that I know there might be problems down the road. I'll see how it goes tomorrow.

The maximum claim on their existing 1 year warranty is £1000 which I'm fairly sure wouldn't come anywhere near sorting out problems with the diff or gearbox. Should I be asking for the max claim to be upped to something like £5k?

[zollaf]

hmm, these warranties like this are silly really. for 6 months the seller is liable , any fault is presumed to have been there when sold.

[huntygowk]

Yes I suppose a year warranty only really helps if something goes wrong in the last six months as would remove the need for the buyer to prove there was a fault when bought.

Am hoping i get it all sorted out tomorrow.

[fest0r]

I would be looking for a no limit warranty (parts and labour) on the components zollaf suggested for the length of your ownership. Also, can you select who does warranty work or are you tied into them? Are they independent?

Looks like used s-tronic boxes with short warranties start at a £2k and refurbs are £2.5k up… supply only. Used rear diffs are around £300/400. It obviously depends what’s needed (if anything), but if there was a problem with a replaced gearbox then it could easily go over £5k with labour etc. and a few visits.

I’m guessing £1000 would easily get you a used diff and gearbox oil change… at an independent.

[huntygowk]

My eyes are watering reading these prices :yikes: Thanks for the advice re costs, I'll bear it mind when talking with dealer. They are an independent dealer, not 100% sure but don't think warranty work would be tied to them, think it would be done by whichever garage in my area had deal with warranty company. To be honest I'm not too sure about the fine detail there, haven't needed to use third party warranty before and am hoping that doesn't change.

[huntygowk]

So, latest update. The car is going back :(
Spoke to the dealer today and they could offer the replacement tyres but not extended warranty on the diff/gearbox. They admitted that they can't offer the warranty because they now have no idea themselves of the history of the car regarding the tyres, and while in 99% cases it might be absolutely be no bother they don't want to set themselves up for expensive bills further down the road either. I'm in the same boat as well. So the car is going back. The dealer has been pretty good about it I think. Although it's an obvious eff up on their part there's been no arguments at all about my returning the car and getting my p/x back (luckily it's not been sold!) They're arranging drop off/collection as well (the garage is about 200 miles away, so very happy about that)

Am totally gutted about returning it, but I think without a warranty I'd be listening for every single knock/whine/bang/grumble and thinking the worst.

Many thanks for all your help and advice, the forum has been extremely helpful :D

Will keep looking for an A6 Avant 3.0 Tdi S-Line Quattro, but a few lessons have been learnt!

[zollaf]

shame, but well done on their part for taking responsibility. i presume they will sort the tyre out and sell it to someone else and if anything does go wrong the tyres wont be responsible ?? to be fair i would probably be happy for 4 new tyres myself and take the gamble if the car is worth it, but its a long shot that may cost you dearly or may be a reliable car. but then you could buy another and the engine blows up just out of warranty ??

[huntygowk]

Yes I think the tyres will be replaced and then car sold on. If that had happened before I'd got it I'd have been none the wiser as well. Entirely possible any other car I look at could be exactly the same, in that case I would definitely go with 'ignorance is bliss'.