I noted that some feel that stylish low profile tires are detrimental to ride comfort. I also feel that the ride comfort of the stock tire wheel combo is very rough and noisy for a luxury sedan, even though if you call it a sport sedan.
I am completely aware that Jaguar is following customer demand for the look of stylish sporty low profile tires. And yes they do offer exact cornering quality. As its a matter of personal preference I'd like to see a more comfort option. I don't do heavy sporty cornering that often, but I can't always avoid Chicago area potholes and lost 2 tires already to damage.
I wish Jaguar would do some research and offer a more cushy tire/wheel combo even as an after market item. I put my thoughts about possible tire sizes in and would like some input. May be a tire expert can chime in.

I love the car but would like to get a smoother ride. Heck, my Range Rover rides smoother and quieter. I did some tire/wheel combo research to go to a 18" wheel. I would welcome your thoughts. Here is what I found.
Based on stock tire/wheel outer tire diameter is 704 mm front and 700.5 mm rear.
Options would be:
245/45ZR18 front, total diameter would be 245x0.45=110.25+110.25+457.20=677.7
275/40ZR18 rear, total diameter would be 275x0.4=110+110+457.20=677.20
That would mean overall diameter is about 1" less. Not sure what impact that would have.
Other option is
235/50ZR18 front, total diameter would be 235x0.5=117.5+117.5+457.2=692.2
255/45ZR18 rear, total diameter would be 255x0.45=114.75+114.75+457.2=686.70
Since I'd like to stick with a similar overall tire diameter to stock I would like a 235/50ZR18 on front and a 255/50ZR18 on rear. Problem is, I haven't found a 255/50 as it seems most 50 ratios go only up to 235. I'll keep searching though.

 

So, I would be curious if an 18" wheel will clear the brake calipers in the front. The rotors and calipers are smaller on non-supercharged vehicles, but given that yours is supercharged, it may not fit. I haven't measured mine personally, but clearances already look tight as is.

 

I had also investigated possible taller tire sizes for the XJ. What I'd found that the sizes are extremely limited. The stock wheel/tire combo calculates out to be 702.6mm. I do not mind going larger or smaller but, not by more than 5 to max 10mm. Otherwise the speedometer and computer will be off.

The closest I came to was a 17" size which, if I remember correctly, was the 245/55/17 size. Others in 17" or 18" were at least 10 mm off the stock size. Of course, then we would have to find the proper wheels with the right (strange) bolt pattern and correct offset, which would be likely more challenge than finding a tire. Then, as you indicated, we have to make sure that the brakes clear. I wonder if the bolt patterns of some of the previous XJs are the same?

You are correct, the ride is rough and noisy for a luxury sedan. Some people do not seem to mind it but, I personally do. I am willing to take up with a compromised ride in a dedicated canyon runner but, not in a car intended as a luxury platform. Jaguar, as well as other manufacturers, should really offer various wheel/tire options so that the customer can decide according to their preferences.

Thanks for your research, please let us know if you find a solution. Same on my side, I'm looking for one. I feel the other culprit here, besides the tire sidewall, is the damper valving. The damper rebound valving rates feel fine but, Jaguar went overboard with the compression valving rates which is likely the reason for the fact that we feel driving over every single ant on the roads. I always preferred softer/medium compression and tight/stiff rebound damper rates for both street and race cars. The cars actually will have better suspension compliance and better performance handling if set up that way. I wonder is the 2013 software update on the dampers could fix this issue on 2011/2012 cars or, would they actually have to change the valves inside the dampers? It would be nice to know what actual changes the factory is making for 2013 to better the ride? Not sure how to find out, usually the dealer can not answer these kinds of technical details.

Albert

 

So I measured the clearances on my car when I got home from work today. I have 20s on my car and in the front, there is a little less than 3/4" of clearance between the front caliper and the wheel. 19s would fit but there is no way to fit an 18" wheel on this car. I can't speak for the non-supercharged versions though.

 

even though it is probably a moot point now, the closest match to stock diameters on an 18" wheel would be

245/50/18 in the front (-1.8mm diff, 0.26%)
275/45/18 in the rear (+4.2mm diff, 0.6%)

Both Pirelli P Zeros and Continental ContiSportContact 3s are available in those sizes...

 

I did make a visual check on my brake clearances for my normally aspirated XJL. It seems that I could easily go to 18" but, likely not smaller. The tires you found above would be perfect fits. My 2005 XK had 18" wheels with different sized tires (think, 245F, 255R) and the car did not ride particularly well on them. My '08XK on 19" wheels and its 245F 275R actually rides better than the '05 did on 18" and even better than my XJL on 19". The difference is all in the electronic vs. mechanical dampers. The '05 had no electronically controlled dampers, the '08 has them. Since my '08XK actually rides better (but, still not as good as I would expect from an XJL) than my 2012 XJL on the same wheel diameter (XJL tire sidewall is actually 0.5 inch taller than the XK's) I am left to conclude that the real difference is in the damper compression settings, as I suggested in my above post.

Would be nice to find out first what exactly Jaguar is doing in softening the ride. Then, can it be retrofitted to an earlier car? That is probably the most prudent approach. Any idea where such info could be secured from? Per my previous experiences the Dealer can not answer such technical details.

Albert

 

I dont know where you would be able to find the information you seek. Keep in mind too that on the XJ, the rear is an air suspension (air bags) while the front is conventional gas shocks (or was it the other way around? I can't recall)

On the 2013s, I'd be curious to find out if it was just a software change or if it was a major mechanical change in the suspension.

There are a few techs here on the forums (Brutal comes to mind) that may know what was changed between model years.

 

Gears,

I suspect you have the 20" wheels on your car, since it's supercharged.

Before you make any decisions, it may be beneficial to test drive some XJs with different wheel sizes. I am sure, any Jaguar dealership would accommodate you.

Downsizing to 19" would help a quite a bit. I remember when i was still searching for a XF, i drove a 09 supercharged version with the 20" wheels and a 2011 with a 19". The car felt a lot more choppy with the 20" Believe it or not, you will feel a significant difference.

 

Just a funny tid-bit.

When I was purchasing my XJL at the dealer, they had a new Supercharged XJL sitting inside the showroom with the 19" Base XJ wheels installed. When I asked the sales manager why the change, he said that "some" customers preferred the ride of the 19"s, instead of the stock 20"s.

Then, I looked at the window sticker and was shocked to see that they charged $1500 extra for putting on the Base XJ wheels/tires. I asked why? He said that they basically had to charge because they had no use for the 20" take-offs. I called BS on that, as I fully expected to see a Base XJ with the 20" wheels somewhere on his lot and an extra $3000+ sticker for the optional wheels. What a racket!!!

Albert

 

Wow, thanks for all the feedback. Seems I am not the only one running the options through my head. My first thought was just going down to stock 19". Obviously any dealer charging extra for those is full of BS. They are all over ebay as take offs because of people upgrading their non supercharged stock 19" to something else.
After that initial thought I realized that the sidewalls on the 19" are still pretty low. But I also read some of the feedback here stating the difference will be pretty noticeable.
I will go out an check the inside clearance on my stock 20" to the brake calipers. From the feedback I read here, it appears 18" won't work anyways. But I will double check. Heck I better check if the 19" fit considering the SC brake size. Didn't realize they put different brakes on the SC.
I also read some of you talking about the shocks. First of all the air suspension is in the back. Second, I believe that first the tires are to be addressed or ruled out before going a step further. I believe we all agree the tires are the biggest detriment to a smoother ride. I experienced that problems on other cars as well including Mercedes S Class.
On the other hand when you look at Lexus, i.e. my wife's GX470 (I know its and SUV) they have huge amounts of rubber on small dia rims. Big difference compared to my Range Rover or BMX X5. No wonder it rides super quiet. (OK, it rides like a quiet boaty tank, but my wife likes it that way.)
If you look at Lexus sedans known to be super quiet you again won't find those aggressive low profiles. That makes me think of where to start.
Thanks all for all the size re-search. I will measure first if 18" are an option. If not the answer is simple. Go to stock 19" and find largest possible sidewall keeping overall diameter within +/- 5mm or so.

 

I don't know if this will help any, but I had a similar problem with my XKR, The pirellis were noisy, Dunlop Sp Sportmaxx weren't great, so I tried switching to BF Goodrich AS960 Pole Positions all around. Voila problem solved, great grip, quiet ride, and comfy!

 

I had my wife in my XJL yesterday for an extended drive, the first time since I got the car. She had no idea that I've been making an issue about the ride. So, during the drive over rather smooth-looking country blacktop surfaces, just to check if I was overly critical, I casually asked her opinions on the ride. Her responses were: "bumpy", "noisy", even while noticing that there were no visible pavement imperfections. Basically the tires transmitted every bit of unevenness that were not even visible to the eyes.

Once we got on the freeway, I asked her again. She hesitated and said; "not the same, not the individual bumps but, a different sensation...". What she described was that the bumps felt in the seats and the steering wheel were no longer individual and separate but, coalesced into a continuous sense of "vibration", given the higher speeds. Again, no visible pavement issues.

Later, driving over an other stretch of road, all went quiet and she immediately noted that, "now, the ride is fine".

Finally, over a highly traveled two-lane highway with lots of pavement cracks, reacting to the racket the suspension was making, she remarked: "I would not expect this from a car, like this".

So, the car rides well over perfect surfaces. That means, no issues with tire balance or out-of-roundness. The issue is either the dampers or the tires. Next week I hope to take my car back to the dealer and urge them to do a better job checking the components than they did the first time. I hope to get them to change my tires to a different brand to see if that helps any. If they won't do it, I'll spend the monies and buy a set. Not crazy about spending >1K, just to test a theory but, still better than taking up with the poor ride over the long distances that I tend to regularly drive.

Albert

 

Great discussion. I really can use all the input Eventually I will switch to 19" and put Michelin on. That is what I believe will be the best possible solution. Obviously there are many different opinions which is to be expected. The "bumpy" part isn't my biggest beef, eventhough it could be a bit softer on the suspension. What about a switch like in some other cars? soft, medium, hard? I know, there are also pros and cons to that. My bigger beef is the tire noise. That may not have much to do with suspension at all. My past experience shows it is mostly about tires when it comes to roll and road noise.
As most of the time I couldn't agree more with Albert. We took the Jag on a few long road trips on mostly highways and the car was near perfect. Smooth, not too hard. Very good long trip car. Usually we take one of our SUV's or the Van. But now we just like the Jag so much more for long road trips.
Again, I would buy the car again. Its not a deal breaker. But these discussions are helpful to all, especially the manufacturer. Impossible to meet everybody's taste. FYI, I don't believe it has to do anything with the "older" guys wanted to ride "younger" or whatever one commented. If I want "hard" I buy "hard" like my CLS63. That was a lot rougher than the XJ no doubt.

 

Gears

Yes, this is a good discussion. Hopefully it will get us to the point where we will be able to enjoy this gorgeous car fully.

I've been looking at TireRack's selections and their various tests, looking for a tire to replace my Pirelli Zero Nero with. I also read and appreciated suggestions from other posters. From other posters, the Michelin Pilot Sport appears to be tops with the Pole Position and the Continental also getting good recommendations. Yet, when I look at the TireRack test they relegate the Michelin A/S to the last place for ride comfort and noise while mentioning my Pirelli as tops. Hmmm....! So, once again, decisions... decisions... which one to go with?

Tire Test Results : Testing Bridgestone's Potenza RE970AS Pole Position Ultra High Performance All-Season Tire

There is an other factor maybe present with my car that may not apply for other cars. 14 months had passed between the manufacturing date of the car and my purchase date. That means that, in the worst case scenario, my car could have sat on a burning hot CA lot for all those months. If that is the case the tires could simply be cooked. There is a chemical compound that keeps tires fresh and pliable. When that compound escapes, due to heat, the tire becomes brittle and hard. This is the very reason that when replacing older tires with new ones, we always notice an improved, more compliant ride. In race cars, due to ultra high tire temperatures, this chemical agent escapes in a matter of a few laps and the performance follows with a measurable drop off. In street cars, it tends to take far longer but, eventually be gone.

So, as I suggested in my previous post, I will try asking the dealer to replace my tires, given the fact that the tires were, at least, 14 months old when I purchased the car. I do hope that would help but, still thinking that the dampers might also be set too stiffly where they absorb the large bumps very well but, not the small surface irregularities. Again, would like to know what Jaguar is doing for improving the ride for 2013. In my new owner survey the factory had asked me if I would like to be called about my issue; I answered, "yes" and hope to hear from them and find out about those changes.

Albert

 

Just got off the phone with my ex-sponsor from my car racing years. They are a Goodyear dealership and have been the sole regional franchise chosen by Goodyear to sell its racing slicks/tires. They have also been in high performance street applications (wheels, tires, alignments, fabrication) for decades.

Both, the owner's and his son's recommendation for the tire was: 1) Pole Position, 2) Michelin PS (not the all season). He (the owner) also asked me about my wheel sizes and when I told him 19" he went off into an agitated tirade on how impossible it was to get decent ride on anything over 18" for this sized car. He recommended for me to go down to 18" wheels for best results. Not sure if I am quite ready to commit to that as I'd end up with a set of wheels and tires that I could not get rid of when my lease expires. Most people who buy wheels tend to want to go larger than the factory, not smaller.

At this point I'd be simply happy to get the ride quality that I have in my '08XK, also with 19" tires. Not great but, better than my XJL.

Albert

 

Reading through this thread has convinced me the issue lies with the suspension setup itself, not the tire/wheel size... and there is *nothing* you can do about the former.

I plan to buy the 2013 model (after initial depreciation mayhem). Only thing I'll miss is the 1200-watt B&W stereo.

Cheers,
Wolfy

 

I've always thought the main contributer is the wheels and tires. High performance tires have much stiffer sidewalls which simply do not absorb the road irregularities like an all-season tire, or a performance tire designed with comfort as a priority. That reality is made all the worse with larger wheels shod with even lower profile tires. Jags on 19" and 20" wheels suffer from both.

I'd research and purchase the most compliant 19" tire you can find Albert, (even an all-season will provide all the performance you need) and hopefully it will be a satisfactory improvement that you can live with because changing suspension components (2013 upgrades?) would likely be prohibitively expensive. Maybe you could justify buying 18" wheels if you could sell your 19's to someone needing them for snow tires or something, and again find a really compliant tire for them.

Bruce

 

Wolfy

That may very well be true but, won't know it for sure until we start isolating the various components. The easiest and least expensive is to try changing the tires. They "can" make a difference in ride.

Still, I can not ignore that my 2008XK rides better on its 0.5" shorter sidewalls than my XJL (XK-245x40x19F, 275x35x189R vs. XJL 245x45x19F, 275x40x19R). That indicates that either the XJL stock Pirelli tire is far harsher than the Ventus I have on the XK or, it indicates a stiffer damper. I don't think the difference is in the springs as the XJL feel to be sprung quite well over larger bumps on the road. By the way, my ex-sponsor had one thing to say about the Pirellis: "They are junk. They used to make some good tires but, their present tires are terrible." I can not think of a single person whose opinions I would accept more than his, regarding this subject. I'll have dinner with him next week and plan to tap his expertise more on this issue.

I also fully share my ex-sponsor's dislike of 19" and larger wheels. Like he said, it is simply not possible to get a truly good ride with those sizes. The fact that so many people tolerate or, even like them, does not mean much in terms of actual ride quality. People tend to accept what a brand-name factory bestows upon them, even though it is widely known that factories screw up at times, no matter of their pedigree. Jaguars used to have horrible reliability issues and, hand built cars, like Lamborghinis, used to be at the very bottom of the quality heap. You expect to get flawless quality and functionality at those prices but, that is simply not how it works.

It is a very good decision from you to wait for the 2013s. Like Bruce H. mentioned above, changing wheels or tires are our (2011s, 2012) only reasonable options. Of that, changing the tire is my hopeful option as I hate to spend many thousands on the 18" wheels/tires that I will have to throw away when my lease is up. Changing dampers would be a nightmare, if not impossible, given the fact that they are controlled by the computer and the 2013 dampers, if different, likely will require software settings that could not be assimilated into 2012 software updates. I am not certain of this but, it is something to look into.

Albert

 

Right again Bruce. I agree that my most reasonable action is to find the most compliant tire. Kind of hard because so many differing opinions are out there. Like the link from TireRack that I posted above, listing the Michelin ride as the worst of the 4 tested while my Pirellis are on the top (really???). Most posters here raved about the Michelins. So, are they top or bottom when it comes to ride?

I do not mind at all to go all-season. The performance difference is so very small compared to the top rated tires that a minor bit of driver's skill difference can easily bridge the gap. Not sure which tires (all season vs. summer only) have the softer compounds that would help with the ride. Wear ratings seem to be much higher for AS tires which appear to indicate harder compounds. I'll get more answers when I see my old friend/sponsor next week.

It is tempting to just go with the tried V12 Ventus tires that I have on the XK and am rather happy with. Not sure if you remember, in one post over on the XK forum I even "blamed" the quiet ride of the Ventus for allowing the 2000 RPM engine drone to be heard over the road noise. Or, the HTR-Z IIIs that I have on my TT which provide that car with incredible handling and still a decent freeway ride.

Albert

 

Albert,

I think tires in the all-season "ultra high performance" catagory are all likely to suffer the effects of stiff sidewalls much the same as if they were a summer or competition tread and compound. It's the more compliant sidewall you need for ride comfort, and I doubt you'll achieve anything better than an incremental improvement in ride quality if you stick to an ultra high performance tire.

I did a quick Tire Rack search for your model, and by eliminating ultra high performance and run flats with their unwantedly stiff sidewalls, and came up with the Bridgestone Turanza All Season (and newer Plus version) to consider. The Continental came up short, but check the survey and test info to see what you think. The Bridgestone got very good scores in every catagory, including ride and noise. http://www.tirerack.com/tires/TireSe...=57752&tab=All

Anyway, check out the Bridgestone and ask your tire guy about dropping below "ultra performance". You could drive the wheels off it with "no performance" tires, and if they scream a bit like raped chickens coming down the mountain at least they'll feel smooth as silk

Bruce