Whilst the ride won't improve much, seriously there can't be much sidewall flex in a 35 or even 30 aspect tyre, it might be possible to do some much better value sound reduction by soundproofing.

Some years ago i did this to the family Aygo, it made a massive difference to noise and yes i know there's no comparison.

From the bay of E i bought probably 20 or so (probably need more for your car) large self adhesive soundproofing pads, these were around 12" square and probably 1/4" thick, using imperial should upset the europhiles :-) , i cut these to size and shape where necessary.

First thing to do is source where the worst of the noise comes from, you might find blanking off say the whole rear end and rear wheelarches reduces noise considerably, same with under the rear seat, if it does remove all the interior cladding and apply these pads to the bare painted metal around wheelarches inner rear quater panels the whole of the boot, under the rear seat etc...those areas are fairly easy to get to on most cars, if iit works also consider inside the door skins under the carpets inner sills bullkhead and front inner wheel arches where they are inside the cabin.

Could be worth experimenting with several duvets and blankets placed about to see if this is a goer, circa £50/70 and a days work against probably £600/800 for new tyres.

Tyre wise, the worst car we owned for ride and noise was a Citroen C2 VTS, sat on 45 aspect tyres with concrete springs, it came in Michelin Pilote tyres, slung those and fitted Vredestein Sportracs, improved both noise and stopped the nasty torque steer but short of swapping out the springs and shocks there wasn't much could be done for the awful ride.

Now you've confirmed 35 aspect, i once got picked up by a friend in his Golf GTD sat on 35's, the noise and ride it could easily have had no springs at all in a bare racing shell.

Edited by gordonbennet on 19/10/2023 at 11:38

Interesting point about the runflats.

Son bought a used 325i estate from Evans Halshaw, 06 plate cars probably 6 years old at the time, they MOT'd it before delivery and decided to fit new tyres (runflats) at the same time, he wondered about asking them if could contribute to a premium brand fully expecting some unheard of make to be fitted otherwise but before he could get in touch the deed was done at EH's sole expense.

It arrived shod on brand new runflat Firestones, so whilst not maybe regarded as a premium make certainly better than expected, they proved to be an excellent tyre all round, during the winter he removed the winter tyres and refitted those Firestones because the warmer days wet grip of the winters wasn't up to scratch...something i've found too with some full winters.

Full marks to EH by the way, a very positive experience dealing with them.

Edited by gordonbennet on 19/10/2023 at 12:50