as title how much can the viscous coupling take up on different tyre size from front to rear

im thinking of getting front tyres with a rolling radius of
front .210.24cm
rear . 207.13
is this close enough ?

Thanks in advance Andy

 

im trying to decide how much of a differance that makes, I know what the acceptable differances are in front/rear diff step offs,

the problem is, as you drive down the road you dont want the VC to do anyting at all. If you start heating it up then you will lose drive and overheat the VC and the transfer oil.

them two divided comes at 0.986 differance front/rear, small amoun compared to 1.0 but it is still a differance.

what i would do is get the measurement of two identical make tyres, one being brand new, and one worn to the legal limit, this will then give you the max speed differance the vc should ever see.

hth
mark

 

Thanks Markk

 

if your on about profile sizes, 40's 45's etc. i asked this question on an other site when putting tyres on my legacy and was told never use different profiles front to back as this would knacker the centre diff.

 

Some cars requirements will be less tolerant on three than others, for example the old cavalier 4x4 needed the same sized three virtually to the mm front and rear or it would die, which meant new boots all round if you had a puncture whereas the sierra stuff will cope with a mix and match of old and new

Realistically you would be looking at a rolling difference or around 20mm max which is about 0.3% difference front and rear

 

depends on the car. i've heard freelanders have a max tollerance of 5mm front to back. not sure if thats rolling radius or circumference though.

if i was you i'd keep same make and size all round and rotate every 3-5k to keep wear even.

 

im running an mt75 4x4 box for now the tyres i want to run are

front=245/40/18
rear=325/30/18

or i could use 275/35/18 on front but im not sure i will get full lock

 

those sizes (first two) are pretty much identical at only 0.2% out speed wise doing the same revs so i can't see there being much of a problem with that even on a sensitive freelander.

there must be some sierra and escos 4x4 running different tyre sizes front to rear on this site??? maybe those people could give their input.

 

i know Martoon has got some big tyres on the back of his escort but i do not what size he is running .

 

try sending him a pm. i'm sure he'll be happy to answer.

he's probably not seen this thread yet anyway.

 

but he's got a skylin box in his

 

he'll still have more knowledge of this though than cirtainly me so worth a pm imo.