I've got 20" Nevis w/ Michelin Pilot Sport All Seasons and I am considering swapping out the twenties for nineteen inch wheels and tires. I'm wondering what is the down side of reducing wheel diameters in order to regain some ride cushion with an increase in sidewall height?

Don't get me wrong, I love the grip and handling provided by this setup. But given my driving style, I think Jaguar engineers might have pushed the needle a little too far to the sport side of the handling / comfort scale. Actually, I think Jaguar might have been more influenced by appearance than ride dynamics when they succumbed to the big wheel trend and mounted twenties. (Being able to charge an additional $5000 was also an incentive.) Everything I've read about track performance and tire sizes suggests the optimal diameters are much less than 20". Either way, having thin strips of rubber around cartoon-sized wheels is not the look I'm interested in pursuing, especially if I have to give up ride comfort.

Finally, this current set of Michelin's are loud... especially over worn concrete surfaces. The car has less than 22000 miles so they could even be granny-driven originals and aged hardened. Given they are about three quarters worn, I know that new tires will reduce road noise considerably, but I also want to reduce road noise with the new package.

Therefore before I invest a $1100 for a new set of Michelin 20's I wanted to explore my options with using a smaller wheel/tire combo. I'd especially like to hear from owners who have downsized -1; 20" to 19" wheels. Gordo

 

I have 17", 16", and 15" for my old Porsche, and pick whichever set I want to run.

If I scale up the larger rolling diameter of the Jaguar I'm not 100% sure where that would fall, I'm not in a math mood this morning.

One thing I've noticed with tire choices for the Jaguar, is 18/19/20 often weigh about the same as eachother, not the drastic different in weight I see with my Porsche. (17" is a big jump up in tire weight).

I'd imagine the similar weight means that there isn't much a construction difference between the 19" and 20", which also means the 19" may not have any major difference for being softer.

For the Porsche, 17" is a huge difference in harshness and weight from 15" and 16", but 15" vs 16" isn't that noticeable.

It is possible the 19" and 20" on the Jaguar are similar to the 15" and 16" on my old Porsche, not very discernible. Probably at 22" or 21" you get a real kick of difference.

Just my rambling. Cheers.

 

When I replaced the tires that were on my car when I bought it(unknown age), the new ones were a lot quieter on concrete.

 

Tire noise increases with tire wear simply because there is less space between threads for air to squeeze out causing more "tire slap noise". Racing "slicks" are notoriously noisy. New tires are almost always quieter. Many decades ago "snow tires" were very noisy, much like modern truck off-road tires. Now my winter Michelin Ice3s are much quieter than three season Michelins.

 

Discussed several times... Search is your friend.
20" are for looks only....

Noise is subjective due to tread styles, but 19" rims will isolate the chassis from more jarring as they roll. This jarring translates to the chassis itself contributing to cabin noise.
Yes 19" and even 18" from 2007 will ride better than 20's, and actually out perform 20" in almost any road condition except a smooth race track.

Cheaper tire costs as well.

 

Well, I haven't down-sized, but I did up-size from the 19" Carelia's that came on the car, to 20" Senta's. I did it for visual appeal, as I really like the look of the Senta's on the car. I've kept the 19" wheels, as the tires only have about 5000 miles on them, and so if I can convince the wife to take a long road trip vacation I'll put the 19's back on, to put some wear on them.
Since I don't have the same brand/model tires on both, its impossible to do a direct comparison. My brain tells me that the 20's should be firmer, but the tires I put on them were softer than the tires on the 19's (to my disappointment).
Over inflating the 20" tires by 4 pounds got rid of the squishyness, but made the tires firmer, resulting in a firmer ride, but still good.
If the wheels had matching tires, I'm not sure that the difference would be readily noticeable, and the struts may absorb the difference.

 

I have the 20" Senta wheels with Dunlap tires that are about 3 years old. I am also experiencing a harsh ride that I'm not happy with.

I'm no expert, but my gut tells me that the harsh ride is more related to the tires than the 20" wheels. I would love to hear other more educated opinions. Also, replacing the wheels is a lot more expensive than changing out the tires.

My choice is to dump the Dunlaps and go with the Continental DWS06 tires.

Ken

 

This depends on how it was designed.

Think of the stiffness of the tire as a spring rate, the lower the spring rate, the longer the distance is needed to make a particular force.

If you design a 19" tire optimally, you shouldn't use that same design for a 20" tire because you have a shorter throw distance.

However, you can do the inverse, and use the 20" tire construction to come out with a 19" size, the 19" will have roughly the same stiffness of the 20" in this scenario.

It would be like taking 1/2" off a spring, and putting in a 1/2" spacer, the ride will stay the same providing there is enough travel to not bottom out on the spacer.

So whether or not going to 19" would benefit or not is going to depend on the tire construction. If the tire isn't getting lighter in a 19" size vs 20", it probably has the same stiffness/construction, the difference would likely only come into play when you hit a deep pot hole that would blow out the 20" tire, but the 19" might survive.

We don't really have the data available to us, but I would take a tire that didn't get lighter in 19" from 20" as an indicator the same structure holds up both. This would make for the same stiffness.

When I go from 16" to 17" on my old car there is a noticeable difference in tire weight and stiffness. 18" to 19" on the Jaguar does not seem a weight difference on several tires I have checked.

I am unsure on 19" vs 20". However, if a softer ride is desired consider that a heavier tire may acquire that weight from a stiffer construction.

 

I had 19's on my first XF and the ride was sublime, I had 20's on my second and it was nowhere near as good. I actually found the ride in my XKR to be very good on 20's from the driver's seat which was pretty soft after 40,000km of **** on it. The passenger seat however was "as new" with very little **** mileage, and from that seat the ride felt a lot firmer. I had the Dunlops on mine which didnt grip very well at all.

 

Thanks for your reply. What search terms are you using? I've tried the following with little success:

20" to 19"
Downsize wheels
reduce tire wheel size
19'' difference 20"

 

Why buy expensive Michelins? Check out the Continental DWS-06. They're much less expensive and get great reviews. I'm very pleased with them on my XJ, and will put them on my XKR when the time comes.

 

Too specific for a search engine... No doubt you drew blanks...
I used 'rim size', 'tire size', 'rough ride' and similar...
https://www.jaguarforums.com/forum/x...eel-xk-190076/
https://www.jaguarforums.com/forum/x...-wheels-70397/
https://www.jaguarforums.com/forum/x...-my-xkr-65845/
https://www.jaguarforums.com/forum/x...-tires-142046/
https://www.jaguarforums.com/forum/x...eel-xk-190076/

BOL
V

 

I have and have only had 19". I'm currently running Bridgestone S-04 Pole Positions. They are a hard rubber. I like them fine, but I bench my car in the winter. They are not cold weather tires. I'm hearing impaired but with the resonator, is there really such a thing as a quiet ride in an XK?

I won't jump to the 20's. I like the look but also like my teeth fillings to stay in place.

My 05 XJ Super V8 had 19's on them when I bought it. I downsized to 18" for a smoother ride. The ride on that car was ridiculously quiet anyway. I could have a normal conversation with my wife without my hearing aids in. The was my first clue, the car wasn't for me.

I put Michelin Pilot's on the 19" Tobia wheels and found them to be a bit noisy. Being hearing impaired, the highway noise level increased from used 19" tires to new 18" tires. My wife agreed that the ride was smoother but a bit louder. I could only blame that on the tire.

 

I'll add this. Your tire search is going to be frustrating as hell if you base them on opinions here, or Tire Rack.

Road surface material and conditions will dictate quietness. Concrete will always be louder than asphalt and there are different types of bituminous materials, depending on geography that will affect noise level as well.

I would suggest getting input from a few local tire shops and dealerships. Also the input on tires will be more valuable from your neck of the woods than from me up here in Minnesota.

 

You are very correct.
Tire search can be subjective, however rim size and suspension geometry is simple math and physics.

 

To the OP: As stated earlier, tire searches are subjective, and so are the opinions of the members on this forum. Stuart is pleased with the Conti DWS-06, and I am not.
These are the tires I put on my 20" Senta wheels, and found them to be initially scary when going around a curve. Felt like the tire sidewall was caving in and I'd be running on the rims. Nowhere near as stable as the Bridgestone Potenza RE970AS tires on the 19" Carelia's. I didn't notice any difference in the noise level between them. So even though the DWS-06 is higher rated than the RE970AS on TireRack, I'm hoping the Conti's wear out soon, so I can put on something different (but they have a dang long tread life).

 

Can't judge the comfort level of the 19's as I have only had 20's. But so far I have no problem with the Conti's DWS 06 tires and enjoy the smooth and quiet ride we get during or week end cruises. Just my 2 cents.

 

Thanks Sean, I agree w/ you. I am fairly well versed in the fine art of tire selection so I am not worried about being swayed by the subjective opinions of arm chair tire testers; or the marketing efforts of tire discounters to push overstocked specials. I've got a good relationship with a retail Goodyear dealer who is also active in Nascar and SCCA events which gives me confidence in his opinions and recommendations.

BTW I've got Michelin Pilot Sports on one sport suspension E91 BMW; Perelli Zero Neros on the other AWD E46 BMW wagon and a set of Continentals DWS on the XK8 comfort-mobile convertible... and am very happy with them.

PS the knock on the Contis was excessive wear on the outside edges during aggressive cornering. My dealer recommended avoiding them on the XKR but was fine using them on the XK8 which is my cruiser.

 

Every tire is a compromise of various factors including, but not limited to, ride comfort, traction (dry and wet), cornering, braking, road noise, treadwear, tire compound, tread design, and cost. Your driving style determines the priority of those factors. Some factors are mutually exclusive, such as UHP summer tires and winter traction.

For me, the Conti DWS-06 was a good choice in the All-Season tire category considering my driving style, climate, performance priorities, and cost. There is no "one size fits all" in tires, so what works for me might not work for you.

 

My 2009 XKR had 20" wheels, I now have a 2010 XKR with 19" wheels & the difference is quite noticable. Granted, there were some suspension changes between the two models so I can't say for sure how much that changed the ride vs wheel size. I'm in the SF bay area & they have some of the poorest roads i've ever enountered. In the 2009 I felt every little bump where in the 2010 the ride is significantly smoother. In my opinion if you can get a hold of some 19" wheels at a fair price go for it, I think you will be happy with the ride.