Thanks guys.
Ralph yes the gates one I bought last year is a different design to the original. I pulled out the old to show in pic below. It was propa shagged.
The gates one I bought last year seems to be a bit odd on further inspection. The second outer rubber (which is not visible) seems to be off centre, when I pull hard bracing it in my hand it’s comes back to an off centre position. I checked the motor running without it one, the shaft itself spins nice and cantered.
So it looks like either this gates pulley is, yet again, failing too quickly. Or I’ve done something wrong. I mean last year after only 2 weeks a previous pulley failed, then the replacement (warranty) worked for over a year to now. I’m thinking I’ll find an original Stilo pulley from a broken car at this point. One that looks exactly like mine. I know it might not run that long (though these are surely good for big mileage) but it’ll at least be a sure test.
If my tensioner is too loose I don’t see how it can wreck the pulley. And I just don’t see anything that has made the belt tighter. When it’s all assembled I can just about live the tensioner when pulling down on the top stretch of the belt (between alt and water pump).
View attachment 211760
It's an odd problem for sure... but new pieces might help to work out what's gone awry.
My Fiat pulley has 205,000 miles on it, and shows no signs of disintegration at all (it lives in Wales though, so it's very rarely warm, never mind hot)… but it means the Fiat pulley is pretty sorted. A second-hand Fiat one will be cheaper than a new one, at least until we work out what's killing the pulleys, if anything. It could just be that the Gates pulleys are not great and there's nothing wrong with the car itself.
The Gates pulley must be the same size as the Fiat one, since the 55096301 pulley uses a 1270mm belt and the 55190424 pulley (16v) uses a 1360mm belt.. but the Gates TVD1013 pulley is listed as replacement for both of these Fiat ones. I suspect the 16v may just have a different pulley-locating arrangement since the crank will be different.. and the Gates pulley can fit on either the 8v or the 16v by being made more "universal". It could be as minor as that.
Don't worry about your 1275mm belt. When I measured mine I think it was also 5mm longer. It could be the belt is measured on the inside run, whereas you and I probably measured around the outside. Anyway, 5mm is so trivial that it makes no difference.
I don't see how the tensioner can be wrecking the belt either... it has a spring that presses against the belt.. so there's a finite amount of force it can exert... but it could be "uneven" if it's a bit sticky, so that the pulley experiences "tight" then "loose" as it goes round. Admittedly it's a long shot..
Can you rotate the tensioner all the way to the end of it's travel? I had to buy an extra-long (40cm) 15mm ring spanner to be able to get enough leverage on the tensioner (I'm sure it'd be easier if the car was on a ramp) but now I can rotate the tensioner right round to it's end stop. With no pressure on the belt at all, the belt will fit easily over the other pulleys.. but there's not much belt to spare.
If your tensioner moves freely and without graunching/grinding or any indication that it's stiff or sticking ("heavy" is okay.. ) then cancel my suggestion to change it. I talked myself out of it.
I doubt your belt is twisting the pulley. If it was misaligned, you would have wear on the shoulder of the belt. You would see the grey/brown cords being exposed, instead of the rubber shoulder.
Can you photograph your aux belt run? I wonder if it's fitted right. It should pass ribbed side onto the grooved/metal pulleys and smooth side to the smooth/plastic pulleys. I can't remember if it will fit in any way except the right way, if you obey that ^ rule.. but it might be possible. That could be making the belt too tight..?
Otherwise, if it all checks out, then I'd have to conclude that there's nothing wrong.. just the pulleys (both Gates) both failed. The Fiat (or any other brand) might fare better.
Ralf S.