Quote:
Originally Posted by 100K+
Found this thread from here
https://www.volvoforums.org.uk/archi.../t-144353.html
This is similar to what I said earlier :- the early V70 + V70XC ran a viscous coupling which was very unforgiving re different tyre diameters.
Since about 2004 perhaps sooner all 4x4 systems fitted to Volvo have been a Haldex system which could car less about tyres of different diameters.
Cheers
Bob |
Thanks Bob, I have done a little research myself and our V40 has a Haldex Gen 5 which doesn't have a viscous coupling. Reading on the Internet the Haldex Gen 5 should be able to cope if the speed is kept below 80kph. There are posts warning about staggered setups that run different diameter tyres between the front and the back but exceedingly few on cross axle diameter difference. It seems that ‘stuarts’ problem and mine are very rare occurrences.
I am now chasing the thought that it is not just the Haldex but competing safety systems. When I was driving back the instrument display should have lit up the Electronic Stability Control as the module should have seen that R16 space saver on the nearside wheel was rotating faster than the R18 nearside wheel, it was not. The Tyre Pressure System should have also lit up for the same reason as it should believe that the nearside was flat because its rotation speed was continually different from the other three wheels for a long period of time, but the light did not come on.
I think that the control modules thought that the nearside wheel with space saver on was suffering from a lack of traction and to keep the car stable just kept putting the brake on that wheel alone forcing the car to steer to the left as tractiopn was there. The Haldex hydraulics then had to work hard transferring power to the rear diff for the entire duration of the journey to balance the power. I think this happened with ‘stuarts’ car and after a time blew oil seal. I was lucky as I did not have to travel as far on the space saver.
I have tested the Tyre Pressure System this morning, dropping the nearside rear wheel to 20psi and it did not raise any warning. I could test the rest but there is little point as I have proven that something is wrong with at least one of the sensors that I think could have caused this problem to occur.
I will get the car alignment checked next week, change the offside front tyre for a new one and rotate the backs to the front. I will then send a compensation claim into the council to see if I can get them to pay. The car also needs a service, so I tell the dealer the problem with the sensor, the problem with the driving on a space saver and my theory, and then let them solve it. When I get it back, I will have some fun seeing if I can re-create either problem. The car is still under standard and Select warranty so if they haven’t fixed it then they will have it back until they do.