The MOT didn't find anything untoward.

The MOT didn't find anything untoward.

BT's question is an ecellent one, and something that can easily be missed by main dealers - I recall it being raised here before, so best to get it verified beyond doubt, just in case.

The tyres you said are fitted should - by their size profile (they are almost the same sidewall height as now on my 17yo Mazda3), be perfectly fine in terms of comfort, with the make/model of tyre making less of a difference than if they were low profile (below 50) to start with.

The MOT centre I use is one that also trains new testers, so I'd be surprised if they hadn't noticed transit blocks

A friend has a Logan and has the same issue. His Stepway is marginally more comfortable due to the larger tyres.

Worth bearing in mind that it is not the size of the tyres exactly that matters but the depth of the sidewall (from wheel rim to the road). So unless the sidewall of the tyres on the Stepway are deeper, the tyres being bigger wouldn't make much difference. But the Stepway also has a higher ride height than the Sandero (by about 20mm or thereabouts if memory serves), and that could well explain a cushier ride.

There are two aspects I suspect are responsible for your harsh ride. First is the term "eco" within the name of the tyre (Ecowing). This will invariably mean a harder compound of rubber giving lower rolling resistance (especially along with a higher pressure than others think necessary for a car like the Sandero) and lower wear rate. The second, in combination with "eco" is the actual weight rating of the tyres. The higher the number is, the stiffer and stronger the rubber will be (to deal with more weight). Your weight rating of 88 represents 560kg per tyre, four of which is 2240kg. Now I have taken the liberty of assuming your Sandero is the previous gen car, the heaviest of which would be the diesel engined version. But even that only has a GVW* of 1633kg, way less than your tyres can deal with. If your Sandero is a petrol version, you can knock at least 100kg off that GVW. I would say, even accounting for a disparity between the weight over the front and rear, you don't need any more than 80 (450kg per tyre, 1800kg total) for a petrol, and maybe 82-84 (475-500kg per tyre, 1900-2000kg total) for a diesel. I should point out that I have no idea of the legalities of choosing tyres with a lower weight rating than OE. But, as long as they comfortably exceed the requirements re the GVW of the car, I can't see why it would be a problem.

For reference, my VW Caddy van has a GVW of 2240kg, and while I choose tyres with a 95 load rating, I could get away with 91's. That represents 615kg per tyre, only a little more than yours.