This is a huge down side of running narrower tyres.; and why people often comment on much better the ride characteristics are when they swop from 215/60/17 to 235/55/17 or better still 235/60/17. And also thats why VW fit their premium T6's with 235/55/17 as standard or 255/45/18's as options; they just ride better, because they can run at lower pressures.
I know on the continent they regularly use narrower tyres than OEM for winter use, because the grip levels are higher on snow/ice surfaces with higher ground pressures. It's an interesting thing (well to sad engineer like me), that the pressure you run in your tyre, is the same pressure that your tyre exerts on a hard surface.
The more pressure in the tyre, the lesser the flat spot on the contact patch with the road, so the higher the pressure exerted on the road. Very interesting
So, a couple of things to consider;
What level of load to you carry?
How is this spread between your axels?
A quick trip to your local public weigh bridge can confirm each axel load
What is the load rating of your tyre, and how does this compare to your axel load?
If you are getting close to the maximum load of your tyre, you need to be running that tyre close to its maximum pressure (printed on the side wall of your tyre), thats because most tyres can only support their maximum load at their maximum pressure.
If you look at your front tyres (when inflated to their correct pressure), and try to measure the side wall bulge at the bottom of the tyre by using a parallel straight edge off the wheel rims; this gives you an indication of how much you can adjust the rear tyres by, so that the bulges match. This is because generally the fronts carry the passenger/engine/transmission load(fixed-ish) ; and the rears carry most of the cargo load(variable-ish).
So (if you haven't lost the will to live
), fit 235/55/17-235/60/17's next time
