Different tyre sizes and the VC

1
I have a question about damage to the VC if tyres are too different in size. I obtained a set of four tyres 50% used and one new one. All are the same brand and size. The circumferencial size difference between the used tyres and the new one is 15mm (Used 2090mm, new 2105mm). Can I run the new one with the old ones? I could buy a second new one and run one new and one old on the front and one new and one old on the rear. Would that mean that the VC is not under load on the highway?

Thanks
Doone Wyborn
89 Syncro with Golf 2 litre motor since 2003


2

Doone,

The free circumference is not a very accurate reading.  It is the rolling circumference that matters.  There is a paper on the process for measuring the rolling circumference in Files.

Where there is a difference between the total rolling circumference front to rear, the VC will be trying to equalize the difference and therefore working when it should not..

Les

From: Syncro_T3_Australia@yahoogroups.com [mailto: Syncro_T3_Australia@yahoogroups.com ]
Sent: 27 December 2015 13:38
To: Syncro_T3_Australia@yahoogroups.com
Subject: [Syncro_T3_Australia] Different tyre sizes and the VC

I have a question about damage to the VC if tyres are too different in size. I obtained a set of four tyres 50% used and one new one. All are the same brand and size. The circumferencial size difference between the used tyres and the new one is 15mm (Used 2090mm, new 2105mm). Can I run the new one with the old ones? I could buy a second new one and run one new and one old on the front and one new and one old on the rear. Would that mean that the VC is not under load on the highway?
Thanks
Doone Wyborn
89 Syncro with Golf 2 litre motor since 2003

3
Thanks Les,

So one new and one old on the front and one new and one old on the rear should be OK.

Doone
4
Might be a good time for a decupler no more problems,

On Sun, Dec 27, 2015 at 12:37 PM, doone.wyborn@gmail.com [Syncro_T3_Australia] <Syncro_T3_Australia@yahoogroups.com> wrote:

I have a question about damage to the VC if tyres are too different in size. I obtained a set of four tyres 50% used and one new one. All are the same brand and size. The circumferencial size difference between the used tyres and the new one is 15mm (Used 2090mm, new 2105mm). Can I run the new one with the old ones? I could buy a second new one and run one new and one old on the front and one new and one old on the rear. Would that mean that the VC is not under load on the highway?

Thanks
Doone Wyborn
89 Syncro with Golf 2 litre motor since 2003



5
sure , a decoupler has some advantages..such as not needing to have a perfectly matching spare tire ..

There are safety advantages to having the AWD working full time though ..
the anti-lock brake affect for one.
In two wheel drive on any car.....the front brakes are stronger ....they will lock up first in a panic breaking situation ..
which is really bad ..with fronts locked, there is no steering ( driver has to be aware enough to let off the brakes,
no matter how badly needed ) to get steering control back. )

and there's just less braking with the fronts sliding .
AWD ...each end tends to keep the other end rolling.
It's a brilliant system.

You can research it forever of course online..
but I gather that it's pretty important the 4 tires match almost exactly, for the health of the VC.

there is such a thing as shaving a tire, though I've never found anyone to do it.
In Showruum Stock car racing..
where the car must be exactly stock,
since new tires don't handle as well on a race track as worn-in some ones do...new tires are shaved down a few millimeters to get a touch better handling and lower lap time.

here's just one article of many on tire shaving.
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=67

perhaps if one tire is bigger than the others, this would be a solution.

Scott

On 12/26/2015 5:49 PM, Peter Wilson peterw1000@gmail.com [Syncro_T3_Australia] wrote:
Might be a good time for a decupler no more problems,

On Sun, Dec 27, 2015 at 12:37 PM, doone.wyborn@gmail.com [Syncro_T3_Australia] <Syncro_T3_Australia@yahoogroups.com> wrote:

I have a question about damage to the VC if tyres are too different in size. I obtained a set of four tyres 50% used and one new one. All are the same brand and size. The circumferencial size difference between the used tyres and the new one is 15mm (Used 2090mm, new 2105mm). Can I run the new one with the old ones? I could buy a second new one and run one new and one old on the front and one new and one old on the rear. Would that mean that the VC is not under load on the highway?

Thanks
Doone Wyborn
89 Syncro with Golf 2 litre motor since 2003