hi hope you can help, i want to run 7.5x17 et 33 wheels up front with a 25mm spacer to clear brenmbos and 8.5x17 et 33 the front tyres are 205/40 and back tyres are 215/40 ive been told this will blow the diff on my rallye is this the case?
I can see what they mean - there's more grip, so that puts more pressure on your diff before it loses traction, but you can say that about any car with a diff (i.e. all cars) - front wheel drive cars have diffs, so I don't see any difference. I would have guessed that your clutch is the weakest point - before breaking the diff I would expect the clutch to break, but of course we are talking extreme circumstances here. I would do it to be honest - Rallye's need something like that to fill the arches. If you are worried, you could post something on Dubforce forum where there are lots of Rallye owners running more power, wider wheels, etc. Matt.
I think its more likely to cause problems with the syncho viscous coupler that transfers power from front to rear wheels possible ending in transmission wind up, I know that's why VW fit a space saver with a similar diameter to the normal wheels on synchro models.
I would have thougth it would be more down to the fact that you are running 2 different rolling radii front and rear, meaning that for one wheel revolution, the front and reaw wheels would cover different ditstances. Ther is only a 4mm radial difference betweent he two tyre sizes quoted, but this adds up to the rear wheels want to do nearly 42 metres more per kilometre driven by the fronts. It may be that this is not an issue. I seem to remeber reading a post on here a while back where it was said that the rear axle on sychro cars could be under or over driven. I cant remember which one, and since the other would kill the diff, this needs confirming, and I cant remember who posted it Possibly the easiest solution would be to fit a pair of tyres to the front or rear that match the rolling radius of the other 2.
You need to get the rolling radius the same, or as close to as possible, front to rear. If you don't you will cause damage, go over to vwsyncro.co.uk for more info.
