Użytkownik "Dano58" wrote
>I have the Torsen system on my A4, and have been told that as long as
> the tires on the same axle are the same and have similar tread wear
> (i.e., within about 3%), you're okay.

According to the little snipped posted on Tire Rack which they say they took
from the owner's manual: ""rolling radius of all 4 tires must remain the
same or within 4/32-inch of each other in remaining tread depth":
http://www.tirerack.com/tires/tirete....jsp?techid=18

> That said, isn't the Haldex
> system a part-time system? That is, the car is FWD until slippage is
> sensed and the Haldex sends power to the rear wheels?

True, but it can be argued that different rotational speeds between wheels
(caused by different tread depth) can be decoded by the system as slippage
thus causing the system to engage. But as noted, it's not as crucial on
Haldex as it is on torsen. And honestly, I think things like tire pressure
and carrying load (full trunk vs. empty) may cause higher variations in
rotational speeds than differences in tread depth. I may be wrong though...

Cheers,

Pete

 

Użytkownik "Dano58" wrote
>I have the Torsen system on my A4, and have been told that as long as
> the tires on the same axle are the same and have similar tread wear
> (i.e., within about 3%), you're okay.

According to the little snipped posted on Tire Rack which they say they took
from the owner's manual: ""rolling radius of all 4 tires must remain the
same or within 4/32-inch of each other in remaining tread depth":
http://www.tirerack.com/tires/tirete....jsp?techid=18

> That said, isn't the Haldex
> system a part-time system? That is, the car is FWD until slippage is
> sensed and the Haldex sends power to the rear wheels?

True, but it can be argued that different rotational speeds between wheels
(caused by different tread depth) can be decoded by the system as slippage
thus causing the system to engage. But as noted, it's not as crucial on
Haldex as it is on torsen. And honestly, I think things like tire pressure
and carrying load (full trunk vs. empty) may cause higher variations in
rotational speeds than differences in tread depth. I may be wrong though...

Cheers,

Pete

 

Użytkownik "Dano58" wrote
>I have the Torsen system on my A4, and have been told that as long as
> the tires on the same axle are the same and have similar tread wear
> (i.e., within about 3%), you're okay.

According to the little snipped posted on Tire Rack which they say they took
from the owner's manual: ""rolling radius of all 4 tires must remain the
same or within 4/32-inch of each other in remaining tread depth":
http://www.tirerack.com/tires/tirete....jsp?techid=18

> That said, isn't the Haldex
> system a part-time system? That is, the car is FWD until slippage is
> sensed and the Haldex sends power to the rear wheels?

True, but it can be argued that different rotational speeds between wheels
(caused by different tread depth) can be decoded by the system as slippage
thus causing the system to engage. But as noted, it's not as crucial on
Haldex as it is on torsen. And honestly, I think things like tire pressure
and carrying load (full trunk vs. empty) may cause higher variations in
rotational speeds than differences in tread depth. I may be wrong though...

Cheers,

Pete

 

Pete wrote:
> Użytkownik "Dano58" wrote
> >I have the Torsen system on my A4, and have been told that as long as
> > the tires on the same axle are the same and have similar tread wear
> > (i.e., within about 3%), you're okay.
>
> According to the little snipped posted on Tire Rack which they say they took
> from the owner's manual: ""rolling radius of all 4 tires must remain the
> same or within 4/32-inch of each other in remaining tread depth":
> http://www.tirerack.com/tires/tirete....jsp?techid=18
>
> > That said, isn't the Haldex
> > system a part-time system? That is, the car is FWD until slippage is
> > sensed and the Haldex sends power to the rear wheels?
>
> True, but it can be argued that different rotational speeds between wheels
> (caused by different tread depth) can be decoded by the system as slippage
> thus causing the system to engage. But as noted, it's not as crucial on
> Haldex as it is on torsen. And honestly, I think things like tire pressure
> and carrying load (full trunk vs. empty) may cause higher variations in
> rotational speeds than differences in tread depth. I may be wrong though....
>
> Cheers,
>
> Pete

Thanks for your good advice everybody. As ever, the official line (as
per the manual) will always err on the side of caution, so maybe it's
not completely black-and-white. That said, the dealer has now agreed
to replace the different tyre with one the same as the rest so I'm
happy. Next issue, I guess, is how different the tread depth will
be.......... Thanks, Reg

 

Pete wrote:
> Użytkownik "Dano58" wrote
> >I have the Torsen system on my A4, and have been told that as long as
> > the tires on the same axle are the same and have similar tread wear
> > (i.e., within about 3%), you're okay.
>
> According to the little snipped posted on Tire Rack which they say they took
> from the owner's manual: ""rolling radius of all 4 tires must remain the
> same or within 4/32-inch of each other in remaining tread depth":
> http://www.tirerack.com/tires/tirete....jsp?techid=18
>
> > That said, isn't the Haldex
> > system a part-time system? That is, the car is FWD until slippage is
> > sensed and the Haldex sends power to the rear wheels?
>
> True, but it can be argued that different rotational speeds between wheels
> (caused by different tread depth) can be decoded by the system as slippage
> thus causing the system to engage. But as noted, it's not as crucial on
> Haldex as it is on torsen. And honestly, I think things like tire pressure
> and carrying load (full trunk vs. empty) may cause higher variations in
> rotational speeds than differences in tread depth. I may be wrong though....
>
> Cheers,
>
> Pete

Thanks for your good advice everybody. As ever, the official line (as
per the manual) will always err on the side of caution, so maybe it's
not completely black-and-white. That said, the dealer has now agreed
to replace the different tyre with one the same as the rest so I'm
happy. Next issue, I guess, is how different the tread depth will
be.......... Thanks, Reg

 

Pete wrote:
> Użytkownik "Dano58" wrote
> >I have the Torsen system on my A4, and have been told that as long as
> > the tires on the same axle are the same and have similar tread wear
> > (i.e., within about 3%), you're okay.
>
> According to the little snipped posted on Tire Rack which they say they took
> from the owner's manual: ""rolling radius of all 4 tires must remain the
> same or within 4/32-inch of each other in remaining tread depth":
> http://www.tirerack.com/tires/tirete....jsp?techid=18
>
> > That said, isn't the Haldex
> > system a part-time system? That is, the car is FWD until slippage is
> > sensed and the Haldex sends power to the rear wheels?
>
> True, but it can be argued that different rotational speeds between wheels
> (caused by different tread depth) can be decoded by the system as slippage
> thus causing the system to engage. But as noted, it's not as crucial on
> Haldex as it is on torsen. And honestly, I think things like tire pressure
> and carrying load (full trunk vs. empty) may cause higher variations in
> rotational speeds than differences in tread depth. I may be wrong though....
>
> Cheers,
>
> Pete

Thanks for your good advice everybody. As ever, the official line (as
per the manual) will always err on the side of caution, so maybe it's
not completely black-and-white. That said, the dealer has now agreed
to replace the different tyre with one the same as the rest so I'm
happy. Next issue, I guess, is how different the tread depth will
be.......... Thanks, Reg

 

> Thanks for your good advice everybody. As ever, the official line (as
> per the manual) will always err on the side of caution, so maybe it's
> not completely black-and-white. That said, the dealer has now agreed
> to replace the different tyre with one the same as the rest so I'm
> happy. Next issue, I guess, is how different the tread depth will
> be.......... Thanks, Reg

good news! New tyres tend to have around 8mm of tread

 

> Thanks for your good advice everybody. As ever, the official line (as
> per the manual) will always err on the side of caution, so maybe it's
> not completely black-and-white. That said, the dealer has now agreed
> to replace the different tyre with one the same as the rest so I'm
> happy. Next issue, I guess, is how different the tread depth will
> be.......... Thanks, Reg

good news! New tyres tend to have around 8mm of tread

 

> Thanks for your good advice everybody. As ever, the official line (as
> per the manual) will always err on the side of caution, so maybe it's
> not completely black-and-white. That said, the dealer has now agreed
> to replace the different tyre with one the same as the rest so I'm
> happy. Next issue, I guess, is how different the tread depth will
> be.......... Thanks, Reg

good news! New tyres tend to have around 8mm of tread