I just put on a set of 18" alloys with 235 50's on my new to me s-type, and I'm surprised at the harshness of the ride. It feels a lot more like a pure sports car than a touring sedan. I can pretty much feel painted lines. The tires are velcro on wet roads so I really like them for that quality, and overall performance is outstanding (aside from the floppy front sway bar), but I was hoping for something a little softer. A long road trip would likely play hell on this flabby butt, and tooth fillings are expensive. My question is: is the ride harshness just a function of 18" wheels, the vehicle design, or these tires? I have a few days to swap them with something different (and wider). I have no experience with this car before these wheels were put on, and so have nothing to compare it with. I always thought jags had an old fart's ride with a young man's performance.

 

The pre-2003 (USA) cars had poorer suspension. It was hugely improved with the 2003+.

Of course I don't know the condition of the suspension parts on your car

The actual tyres (make & specific model) make quite a difference, too. Pirellis I found harsh and noisy, for example.

 

Lots of reasons, some of which I include.

The suspension of ANY car is tuned so ALL components work as the designer meant it to. So increasing tyre diameter and profile derease will always give harshness. As you have said, the lower profile stick like glue etc etc, and wear quicker than taller profile tyres.

To go from 16" to 18" is a huge alteration without adressing items such as dampers and spring rating to achieve what you want.

I would settle for 17" with 50 series tyres, and should be better???

Spring ratings vary with manufacturing spec changes, such as the "R" and "Sport" in Jaguar language.

Tyre brands vary ride quality quite a lot.

Of cousre the OBVIOUS, maybe its got waaaaay too much pressure in the tyres. Some fitters put really high pressures when fitting, NO idea why, they just do. Soooooo, chek the presures and lower accordingly, and that MAY give a better ride.

That sway bar rattling and clattering is certainly a NO NO, so bite that bullet and DO THEM. You need 2 sway bar "D" rubbers, and a few hours of spare time, and that alone will improve the ride no end.

 

My 2005 S-Type 3.0 has 17-inch wheels with 235/50/17 Dunlop SP Sport Signature tires installed in early January 2011 that have between 5,000 and 8,000 miles left in them. Its ride has always been very comfortable, moreso when the tires are new. There's no question that 17-inch wheels and tires would provide a plusher ride on these S-Types, even the older models that don't have the much-improved suspension....

 

People talk about the later models having a better ride, but what does that mean? Better cornering, a softer ride? Siri telling you how hot you are? Were the earlier models known for a stiffer ride?

Right now I'm running at 28 psi; it was 40 from the installer, but I knew that and adjusted accordingly. there was a difference but not a massive one. I paid a fair bit for these wheels and tires, and yet I don't want to waste the time flipping through a series of models of tires if the results will only be a 10-15% difference. I might be trying to cure an inherent quality of this vehicle rolling on big rims.

Another detail -and I don't know if this would effect things - is the tire itself is a tiny bit narrower than the rims. You could easily slap 250 -265 tires on these things but they installed 235's. To my eyes it looks a little badass with that minor reverse profile, but I wonder what if anything it would do to the ride.

 

Better everything - they re-did the suspension with a whole set of different parts. So it improves cornering and everything else.

What exact tyres have you fitted - make &model etc?

 

These. ACCELERA 45 Series The ones with the assymetrical tread, the phi model. And my mistake, mine are 225 45s

 

Those look rather small. Too narrow / not enough profile. That's going to be part of the problem. I don't think they match any of Jaguar recommended sizes. (On my car they would be 10% too small.)

 

AGREED.

Those 45 profile tyres have little to no sidewall, so flexing of the tyre is minimal, so the suspension must take all the bumps etc that the 55 or 50 series on the OEM spec would absorb.

There is the harshness you now have.

 

As other have said, it's the short sidewalls that are giving you the rough ride. The springs/shocks are calibrated for the stock sidewall height and inherent flexibility.

 

Figured as much, I just didn't have enough previous experience to go by. Thanks for the feedback. Final question: the width of the tire. He was originally going to put 235s but then went for 225s. I know the tire is narrower but it's a performance upgrade from what we had originally discussed, and these things have tremendous grip so the narrow tread is not a traction concern. But could narrower tires have any effect on the ride quality? Seems unlikely...

 

The 45 is a per cent of the width so not only is 45 too little you've made the result even worse by going narrower.

You could read all this on many sites if you just google it, you know, and save yourself a lot of time.

 

Well, I wanted to get the opinions of those who are familiar with the vehicle rather than just general advice. But the tire shop installed tires that would result in a stock final diameter, so I have to assume that if they went 45 of 225, to go to 235 they would need an even smaller ratio, like 35, to maintain the same final diameter. what that would do to ride quality, I don't know, but I think I'll go see them tomorrow.

 

To me they do NOT result in the correct stock diameter but are too small. Best to check. Not hard to look in handbook...

 

They are the correct diameter, but with nothing to lose I have an appointment on Wed morning to have them replaced with a set of 245 40 18 tires, which is correct for the sport 2001 s-type. It'll be interesting to see how much it changes the ride

 

That 18" spec is for the front tyres of the S Type R in the X202 onward years/model. That model has different suspension to the other S Types, both in the standard car AND the R spec.

The 2001 V6 (X200) had 225/55 X 16 as standard.

The Sport X200 had 235/50 X 17 as standard.

The R spec (X202) had the 245/40 X 18 on the front and 275/35 X 18 on the rear.

 

As Grant has posted, they're not correct. May be slightly better than the wrong ones you have now, that's about all.

 

I understand that, but 18" rims is what I got, they look great and it'll be interesting to see how the wider tires effect the ride. There's a full suspension rebuild in the future of this beast, and that will improve it even further. Thanks everyone for all the feedback.

 

The correct width with 35 profile on 18 rims is 275, as only used by STR rears. 35 is far too small otherwise.

 

Got the new rubbers on and the ride is far better than it was. Likely a function of make, design, as well as size. It's a firm ride no doubt, but handling is great and it's a good compromise.