today I decided Merc don't know what they are doing and improved my car by fitting tyre sizes I think they should use...

As mentioned in a number of posts the original car was sold on 235 55 17 tyres on an 8" wide rim. It drove well but looked hideous - as its such a large car the wheels were out of sorts - So when they had got very scruffy and I needed a set of new tyres - I got hold of a very good set of the OEM option 8.5" rims got them refurbed - then fitted the Dunlop MO (Mercedes original) in the option size of 255 45 18 R101 tyres and the car was transformed - in to a lumbering, unwieldy, horrible to drive mess - stiff bumpy and it hated corners.

So today I put some Michelin Pirmacy 3ST tyres in 235 50 18 R97 size - of course they have to go on rims that are a smidge wide - thus as I had no idea if these "would work" I didn't want to buy a new set at $1000 so obtained a set of part worn ones in great condition for $300 - but and now most places don't want to entertain fitting part worn stuff - its such big business in poverty UK, the professional tyre places are trying to fight back by being unhelpful.

FYI for non our European Audience - Germany tends to get paid far too much and somehow pay nothing for tyres - thus chuck them away when most are still like new - I guess part of their safety routine around terrorising Autobahns. So to avoid the environmental issues re disposing of tyres - half the rest of Europe scrabble around on secondhand german hand me downs....

As the good places refused to help I asked a mate who races cars how he gets his tyres done - and he said "well I've got all the gear" - so thinking I'd get mates rates - I went to fit them today, and got a quick demo on one tyre then he left me to fit and balance the others !!!! Its quite a work out on these stupidly heavy wheels and I had a bit of fun getting the initial seal to get air in to pop on the bead - as subsequent measurement shows the tyres coming off whilst 20mm wider, are actually 40mm further part on the inside... so I had no seal to pop on the beads, until eventually a bit of wriggling got them to catch and pump up.

Second part of the school day - When doing the balancing he did as the machine told, and then re span for good measure to find it suggested there's another 5g that could go on.... to which he said at 5g most garages don't bother and just fit them ! - but we might as well do it And as I did the rest, only one came out saying spot on first round - the other two both wanted another 5g of which one wanted another 5g on the inside and further round 5g in the outer...

So how's it drive now and the answer is its VASTLY superior - its much more nimble, lighter on its feet, more fun, comfier ride, quieter, more balanced, lighter steering - its like driving a different much better car. Which is what I was expecting. I just don't know why we are always expected to suffer super fat tyres that don't like corners... there is just no need.

The previous size fat tyres didn't even generate more grip - it actually has much less most of the time (than the old 17" 235s). The stiff wide ones pick up more road imperfections and all it wanted to do was shudder and hop about sliding wildly - now with a softer fractional higher side wall tyre (5mm in total height) and with a width that doesn't hate turning, it allows the tyre to move properly so it can take corners. Which begs the question during development - why did they bother with the std 17 inch or the option 18 inch set up ? When what it always needed was lighter 18" diameter 8" wide wheels running the 235 width - better to drive, better emissions, less wind resistance and thus faster (and yes the additional width can make an impact - if you check CO2 emissions - which a big thing on sales and road taxes in Europe as higher spec models with wider tyres move bands)