Horrible Whirring noise after tyre change

[dandywarhol]

Ok - at the expense of boring the old brigade to death (again) a new bongo 4WD was different sized tyres as standard 215/65/15 rear and 195/70/15 front.
This gives around 1% difference in propshaft speeds and is acceptable WHEN NEW! Whenever you start to steer from lock to lock, the difference becomes slightly greater. My switchable Hiace does not have a Viscous Coupling and if I try to turn on dry roads the tyres start to "scrabble" and "howl", that's why the system should only be used on 2WD in the dry. But I digress............

The viscous coupling system is designed to be a service item depending on the vehicle's true mileage and use, and a lot depends on whether the vehicle is used predominately in a straight line on motorways or if the tyres are ALWAYS changed as a set of 4.

Through time and mileage, the VC will become to break down internally and cause the problems you're describing - fitting the same tyre sizes all round and as a matched set prolongs the life of the VC in my (humble) opinion but it will eventually fail.

After you've driven around for a few miles, twisty A road is preferable, jack up one front wheel and see if it turns by itself - it could be over half a turn if the VC if goosed enough! Then get a big socket onto the hub centre nut and try to turn the jacked up wheel - it should turn approx. 120 deg from memory - there's a diagram posted by Demon AV in Russia of the testing technique, you'll find it in "SEARCH"

As I've posted before - I'be be reluctant to buy a high mileage Bongo 4WD

Good luck

[downward dog]

Just a quick resurrection of this post. My Bongo 4WD has 4 winter tyres on alloys, and so I will soon be buying a new full set.....given that 'one size all round' is OK for a 4WD.... is it too dense to ask what/which size of tyre it ought to be !!??

[scanner]

Just a quick resurrection of this post. My Bongo 4WD has 4 winter tyres on alloys, and so I will soon be buying a new full set.....given that 'one size all round' is OK for a 4WD.... is it too dense to ask what/which size of tyre it ought to be !!??

If standard 15" alloys, then 215/65-15 is usual.

If 16" alloys (like mine) then 215/60-16 to maintain the right rolling radius and not upset the speedo too much.

[downward dog]

Thanks Scanner!