255/60/18 tyres anyone?

[soovy]

Hi everyone, new member here, firstly thanks for the forum and all the useful advice, it's been a great help.

I have a query:

I'm running a 4.4 on staggered 19's with sport suspension and self levelling rear, the ride is harsh on broken tarmac and I want to switch to 18's with 255/60 ATR tyres, I know it'll knock the gearing and speedo down by around 10% but I wondered if anyone had used that size tyre and if there are any other issues I should look out for?

Thanks in advance,

Soovy.

[X5-D-Sport]

As a point of interest,
I put matching rear wheels all round on mine with 325 tyres all round...
The tyres are then wide enough to straddle most pot-holes and heavy enough to simply absorb the crater edge impact easily..

Also, if you're getting lots of impact feel thru the steering, I'm just wondering what tyre pressures you're running.
If I run about 36psi, the tyre wear is better, BUT the pot hole impact shock is dreadful, so I prefer to run at 32 front & 35psi rear and have a much nicer ride with less road noise AND also I do a few miles on unmade roads very often too with a better driving feel.

If you have Run-Flat tyres, then the ride may also be a bit harsher !

[soovy]

Thanks for the reply. That's some massive rubber you're running!

I'm not running runflats and the pressures were a bit low at 31psi all round.
I need ATR's here and something a bit narrower is preferable, 235/60/18's are my 2nd choice but I thought they might look a bit skinny in the arches, high shouldered 255/60's would surely help the ride.

[X5-D-Sport]

Well, for my 3 penneth worth,

I got the set of 4 for £400 fitted on the car from Kwik-Fit.... and mid range tyres too... that was a year ago and 20k miles singe & still bucket loads of tread.

The wider tyres/wheels are considerably heavier & the road handling is fabulous, and even better, the front end tyres have ceased to scrub the edges due to the load being spread & less tyre wall roll-over.

The over all feel is much more solid, and I can drive over any damned thing I want and barely notice it happen..

The heavy tyre/wheel combination compared to the weight of the suspension parts leads to less vibration transmitted to the vehicle, so by going for skinny tyres/smaller wheels, you will increase the suspension reaction and more impact shock transmitted thru the vehicle and make the situation worse still !.

Mail me privately with a mail address & I will ping you some piccies.
I have no luck loading them here for some reason...

[X5Sport]

It might also damage the transmission if you get the ratios wrong.  The diffs are quite happy to break as some have been finding recently on older cars (higher mileage).

If not a standard size, also check your insurance.  It may be a 'mod' and they need to approve it.

[soovy]

Thanks chaps - I don't think that raising the gearing 10% would do any damage but looking at the clearance in the arches it might be touch and go so I think I'll go for either 235/60's or 255/55's.

The wider stuff (325's) won't work for me, I need ATR's out here and narrower rubber that can easily deal with snow.

[captainsossige]

My BMW supplied 18s came with 255/55 Continental Wintercontacts, which I believe provide the same gearing as the standard 19s.

[X5-D-Sport]

Whatever diameter wheels you run, just ensure you have a matching set of 4, as per X5Sport says, they like a matching set and you can run into problems with diffs.