Hi guys - here's a couple of pictures of the front tyre of the Green Machine. Its a Marangoni Vanto 185/65VR15. I know its not the performance model (which I understand is very good), I needed the unusually tall profile for my 1970s retro-masterpiece!





I don't know if its very clear in the pictures, but there is a lot of asymmetric wear, with the inside shoulders of both fronts worn down to the limit, with virtually full depth of tread on the outside edge.

Until quite recently, the suspension has had a dash of negative camber, which might explain the wear, but I was also wondering if this exaggerated wear condition might be caused by poor scrub geometry (which I know I have - tread centreline 92mm outside steering axis at last count), or toe-out on braking caused by my recently discovered bump-steer geometry.

Is it possible to differentiate the causal mechanisms based on the appearance of the wear? There is no evidence of any shearing/scrubbing on the surface, just smooth wear. There is virtually no "feathering", and no particular "snagging" feeling if I run the palm of my hand over the tyre in one direction or the other.

My guess is that its camber, but I know nothing about tyres (you probably know this because I have bought a set of cheap Marigolds ). What do the experts think?

Thanks in advance,

Lauren

PS - I should add this tyre is 3 years old and has done around 5,000 miles.

In truth there's no real trauma with the tyre wear, yes it shows some distress but after all this time and work done to the car it's impossible to isolate the criminal.

Thanks for looking anyway Tony. I just wondered if it was possible to eliminate the scrub radius geometry from the equation, as I have chosen to stick with this spindle/wheel offset arrangement. As you say though, its probably a combination of several factors, and 4,500 miles from a pair of tyres isn't considered bad these days - mind you, that is usually with FWD!

Lauren

It's been a year or two since i worked with these tyres but isn't the "Vanto" a commercial van tyre? i may be wrong.......

Calculating the scrub position by "design" is a mare, from my side of the fence this calculation is already done so my position is to deal with a modification or advance things toward handling desires. Historically incorrect SR leads to pronounced handling problems that's easily identified.

Cool

The Vanto is a passenger car tyre, its just not a performance version. I needed a tyre that was no wider than 185 section, but with a 65% profile and a 15" wheel diameter. Those requirements usually eliminate all the serious rubber - they are considered to be a bit archaic nowadays

Without a major chassis re-design I am stuck with the 90mm SR dimension. I've done 13,500 miles with it, I guess I can cope

Lauren

90mm from a contact patch of 185mm reads fine to me assuming both wheels own the same value (more or less) ...... My alert button is 10mm, don't know why it just is