Tyre sizes for a bit of stretch

[lcbandit]

Hi we have an a3 Quattro we are putting coil overs on it along with some 18" staggered alloys, rear measuring 91/2 inch n fronts 81/2 I was told to put 225 40 on the rear n 205 40 on the front as wanting a slight stretch on them, before we spend more money on tyres wanted to check these sizes are ok? We already have the 225's but not the others yet

Cheers in anticipation

Mandy

[lcbandit]

Anyone?

[Sam]

Have a look here - TyreStretch.com - Image Library (http://tyrestretch.com/) - should give you some ideas on what works and what doesn't.

If you stretch too far you run the risk of completely ruining the handling.

EDIT: I've just noticed this is a quattro - all four tyres must be of the same size, compound and tread pattern. You run the risk of seriously damaging the drivetrain if you mix tyre sizes.

[lcbandit]

I've had a look and the sizes are ok that we are getting, but now I'm confused with the sizing we want now, are you saying we can't have staggered wheels on it as that is what makes tyre size different? When we've had normal tyres fitted never checked tread pattern On them, you've worried me now cos don't want to break it!

[zollaf]

he means the circumference of front and back tyres must be the same. they can be any width or size, but overall diameter has to be equal.

[lcbandit]

So as long as they are 18" they will be fine or am I being thick? As for the tread pattern I assume that cross ply or radial? Just to get my head round it all 225 n 205 are the width n 40 is profile height?

Thanks

Mandy

[zollaf]

not quite. right, the 18 is the diameter of the rim. 225 is the width, and 40 is the percentage of the width that the sidewall height is. so 40 % of 225 is 90, so the sidewalls are 90mm deep. the overall diameter is 18'', which is about 45cm give or take, so 45+9+9(theres 2 sidewalls , top and bottom ) = 63cm. this is the total diameter of the tyre.
for the 205, 82 is the 40 %, so 45 + 8.2 + 8.2 = 61.4 cm.
now we do the circumference, which is diameter x pi. so 63 x 3.14 = 197.82 and 192.78. so the 205 width tyres will travel 5 cm less per revolution than the 225's. this will cause the 4x4 system to destroy itself as they are not meant to work like this. you need tyres the same diameter to get the same rolling circumference. 205 45's would give a much closer size but still not perfect.

[lcbandit]

Omg my brain just exploded! I'm crap at Maths and obviously tyre technicalities! Lol, so in my Yorkshire plain English 225 40 18 on rear n 205 45 18 on front? N this won't destroy the drive chain ? :beerchug: What effect will it have in the slight difference?

[zollaf]

i won't go so far as to say it wouldn't destroy things, but less likely to than with 40's at both ends.

Tyre Size Calculator - Changing Tyres - Etyres (http://www.etyres.co.uk/tyre-size-calculator.htm)

handy size calculator

using that, the closest i can get is a 255 35.

[lcbandit]

i won't go so far as to say it wouldn't destroy things, but less likely to than with 40's at both ends.

Tyre Size Calculator - Changing Tyres - Etyres (http://www.etyres.co.uk/tyre-size-calculator.htm)

handy size calculator

using that, the closest i can get is a 255 35.

Hypothetically if it was your car n you had bought staggered alloys like I have, what tyres would you put on it? I'm worrying now we're gonna bugger the car up, I can re sell the rear tyres I've bought, if its a case of car running ok n it havin a slightly stretched tyre would rather have a running car!! Can't afford to not have it on the road

Really appreciate the help you've given

[zollaf]

i would run all 4 tyres the same size. basically the front and rear axles are joined by a clutch. if it senses a difference in rotation it tries to lock up as it thinks an axle is slipping. with odd tyres it thinks you are always slipping so tries to always be locked but can't.
so any size tyre, the 205's or 225's but both axles the same.

[Sam]

Hypothetically if it was your car n you had bought staggered alloys like I have, what tyres would you put on it? I'm worrying now we're gonna bugger the car up, I can re sell the rear tyres I've bought, if its a case of car running ok n it havin a slightly stretched tyre would rather have a running car!! Can't afford to not have it on the road

Really appreciate the help you've given

As long as the tyres are as close as possible, you'll be fine.

A quick look around the internets suggest it's done quite a lot in the USA.

Two threads with facts and figures that may help, the first one has similar sized wheels to you.

VWVortex.com - Staggered setup on a quattro question (http://forums.vwvortex.com/showthread.php?5781269-Staggered-setup-on-a-quattro-question)

and

Staggered... what i've learned... (long-ish) (http://www.audizine.com/forum/showthread.php/61425-Staggered-what-i-ve-learned-(long-ish))

(I still wouldn't do it, but I'm older than I used to be and a lot more boring then I ever thought I would become)

[rhencullen1989]

Are you sure on the A3 Quattro that rolling circomforence is an issue as it has the Haldex fluid drive system, so the rear wheels only drive when the fronts spin up, My A4 Quattro has the drive shafts/prop shaft to the rear wheels so i replace all 4 tyres at the same time to keep the rolling circomforence the same, i am not so sure this is an issue with the haldex, but please enlighten me.......

[Sam]

Seems I may have jumped too early there!

lcbandit, my apologies, the A3 uses Haldex, not true Quattro/Torsen so as long as the tyres are the same size per axle, you'll be fine.

I'll get back in my box now.

[lcbandit]

i would run all 4 tyres the same size. basically the front and rear axles are joined by a clutch. if it senses a difference in rotation it tries to lock up as it thinks an axle is slipping. with odd tyres it thinks you are always slipping so tries to always be locked but can't.
so any size tyre, the 205's or 225's but both axles the same.

Had a read of a few sites n I still find it conflicting n confusing (I'm not blonde honest!) how do we achieve stretch on the front if we have 225 40 all round? The Quattro page is an interesting read but I'm still non the wiser as different people run different tyre sizes on the same rims as ours. Might have to revive their thread and ask the question lol

[Eshrules]

Stretch is played out anyway - more effort than it's worth, increased tyre degradation and an invitation to the nearest Tpol to give your car the once over.

[zollaf]

deviate from standard at your peril.
sure the 4x4 is haldex, but with odd size tyres it will be thinking there is slip taking place and therefore try to limit it.

[lcbandit]

so if i run 225 40 18 on the back and 215 40 18 on the front that should be ok as I think ive worked it out to be -1.38% but not sure if i was using one of the many tyre calculators people have suggested, correctly. It has made very intereseting reading into the do's no don'ts of staggered wheels but as said so many conflicting opinions, just for info as you will all prob's know, the standard ones hes running are 225 45 17 and they don't always have the correct tyre pressures unless i bloody check them!! lol

[S66MJETDI]

What is this stretch thing all about anyway? Surely it just screws up the handling and makes the tyres wear in a odd manner? They aren't designed to be run like that. What if you had a an accident as a result..... can't imagine the insurance company would be to excited about paying out and if someone was killed or seriously injured..... well !

Not trying to be a kill joy but some modifications for aesthetics alone belong in comics no on the road.

[rhencullen1989]

Still confused over the haldex, surely if there was a difference in rolling circumforence between front and back, the haldex fluid drive would think it was slipping and just put drive to the rear wheels, would this not be a good thing, permanent 4 by 4? I have heard of people having the haldex ecu chipped to give proper 4 wheel drive....I need to read up on the Haldex system to better understand its workings.

[lcbandit]

What is this stretch thing all about anyway? Surely it just screws up the handling and makes the tyres wear in a odd manner? They aren't designed to be run like that. What if you had a an accident as a result..... can't imagine the insurance company would be to excited about paying out and if someone was killed or seriously injured..... well !

Not trying to be a kill joy but some modifications for aesthetics alone belong in comics no on the road.

Your entitled To your own opinion n if the mods declared to insurance not a problem, but why would havin a stretch tyre cause an accident if done correctly? It's a mild stretch not a humongous one, not having correct tyre pressures can cause bad handling along with not much tread on tyres etc etc.

[lcbandit]

deviate from standard at your peril.
sure the 4x4 is haldex, but with odd size tyres it will be thinking there is slip taking place and therefore try to limit it.

The calculations you did for me earlier on in the thread does that not count now? Getting confused lol

[zollaf]

personally i would keep both ends the same. a 2wd, fine, no probs, but any sort of 4x4 i would keep identical. the stretch is fine, no probs with that at all.

[S66MJETDI]

Your entitled To your own opinion n if the mods declared to insurance not a problem, but why would havin a stretch tyre cause an accident if done correctly? It's a mild stretch not a humongous one, not having correct tyre pressures can cause bad handling along with not much tread on tyres etc etc.

"Done correctly" is the issue here, correct me if I'm wrong but do any tyre manufacturers design test and manufacture tyres for the stretched look? If the answer is NO then how can it ever be correct?

[lcbandit]

"Done correctly" is the issue here, correct me if I'm wrong but do any tyre manufacturers design test and manufacture tyres for the stretched look? If the answer is NO then how can it ever be correct?

Wouldnt have a clue lol there are a lot if cars with stretch tyres in the modification world, from very mild to quite extreme and they have been doing it for years in the USA, I suppose some have failed and obviously it affects the handling one way or another, but those who seem to be in the know it works for them n especially your drift cars.

[lcbandit]

personally i would keep both ends the same. a 2wd, fine, no probs, but any sort of 4x4 i would keep identical. the stretch is fine, no probs with that at all.
So basically stick to 225 40 18 all round? I assume then the stretch on the front will be very very slight compared to rear, which at those sizes is slight on rear?

[S66MJETDI]

Wouldnt have a clue lol there are a lot if cars with stretch tyres in the modification world, from very mild to quite extreme and they have been doing it for years in the USA, I suppose some have failed and obviously it affects the handling one way or another, but those who seem to be in the know it works for them n especially your drift cars.

There are also many smokers and heroin users but it really doesn't mean its safe....

[lcbandit]

There are also many smokers and heroin users but it really doesn't mean its safe....

So shall we just lock all our doors n stay inside incase something may not be safe??

[S66MJETDI]

Nah..... that would be daft......problem is though you might be a little aggrieved if you get hurt in a accident caused by someone else's risk taking.....

Live and let live fella, but not at someone else's expense.

[lcbandit]

Nah..... that would be daft......problem is though you might be a little aggrieved if you get hurt in a accident caused by someone else's risk taking.....

Live and let live fella, but not at someone else's expense.

FELLA??? would you also like to explain to me what risk is being taken? what proof do you have that having a very slight stretch, or even any stretch on your tyres is dangerous or risk taking? have you actually read through all my thread? it is about tyre sizes with a very slight stretch that will fit an audi quattro with staggered wheels not about how dangerous they may be

[S66MJETDI]

I give up. ( Apologies for the use if the term Fella, no offence meant ).

As for the risk - I refer you to the fact I have already pointed out, the tyres are designed, manufactured and tested as safe to be fitted to the correct wheel therefore any deviation from that is untested and carries risk. You are purposefully placing the sidewall of the tyre in a permanent state of stress with the dynamic loads exacerbating this further........ how much damage that will do and how quickly it could cause failure and a possible accident injuring you and or someone else I haven't a clue, if I did know it wouldn't be risk it would be certainty. Plus as you already pointed out handling is likely to be affected to what degree again I have no idea - but its likely to be in the upper range of available grip and therefore when and if you have a sudden need to change direction or brake heavily perhaps to avoid a accident you may not have that last bit of grip that would have otherwise dug you out of the mire, another RISK you take.

Theres a reason why this practice would be popular with drifters..... its definitely not going to be because it keeps the rubber glued to the tarmac.The other Risk as has already been pointed out is the likely damage to the drivetrain on your car if you fit tyres with different rolling circumferences.......

I shan't comment further......

[lcbandit]

this is what the wheels look like, the car is actually grey not black



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