I Have 19 "silver Jupiter wheels on my 08 xkr vert( sliver ) with Pirelli 245/40 zr19 ( 98y ) and 275/35 ( 100 ) pzero resso Tires with no wear ( 6800 mls ) I would like to change them to chrome wheels, or change them to 20" and sell the 19"wheels and tires.

Has anyone used LA WHEEL AND TIRE EXCHANGE or WHEEL CONCEPTS ( C P W ) CALIFONIA PERFORMANCE WHOLESALE. They both do exchange yours for theirs ( Chromed ).very good price. / OR GO FOR 20"

Are there any problems with going to 20". Bernie

 

20" wheels will make the ride a little more granular. I am unsure if the dealer would have to change the CATS settings to account for the bigger wheels. Anecdotal evidence suggests that 20" wheels are more easily bent on road hazards.

 

there are no worse roads anywhere than in sydney.......

20"s all the way!!!!!

 

Bigger rims and shorter sidewalls have several drawbacks, and only a few gains.
Only two things are gained by big rims, one is looks, the other is quicker turn-in.

In my opinion the negative side outweighs them both.
More sidewall assures a smoother ride, and allows more rubber to stay in contact with the road at all times. In the end, it is the amount of rubber touching the asphalt that pulls you around the corners.

Smaller rims often allow for a lesser unsprung weight (a big plus in overall handling), although with enough cash you can buy some very light 20's I'm sure.

my 2 cents
Vince

 

Larger wheels take more power to spin up than smaller wheels too.

 

I recently bought mine and was surprised that almost every '07+ XKR had the optional and expensive 20" wheels so you aren't alone in appreciating that look.

Reviewers seemed to indicate that the 19" gave the better ride with the '07-09 suspension (no surprise there), while the 20" rode well with the '10+ suspension...which my 2010 does. Maybe try to ride in an '07+ XKR with 20's if change in ride quality is a concern, but a better tire choice could have much more impact on ride quality and performance than a 1" change in diameter. If you were talking about jumping from 17" to 20" size would certainly be a valid concern, but 1" is splitting hairs if appearance is the priority.

What I do notice on the '07-09 cars with 20" wheels is that the standard diameter brake rotors look a little small to my eye. The larger optional brake rotors fill out either sized wheel if you have those.

Bruce

 

A common argument and one I would often side with, but it is slightly misleading from one perspective. It all really boils down to "mass".

Smaller rims may weigh less, but the extra rubber to achieve the proper outside diameters can weigh more than the big rim equivalent. They really do come close to negating any real tangible difference, although I do think the smaller rims still favor an ever-so-slight gain, (although trying to actually measure it would be difficult at best).

My biggest concern is total weight, and the tires ability to absorb road undulations without asking shocks and linkages to work overtime.

It was pointed out to me in other forums that if your willing to spend enough cash on "big rims" to actually get high quality super light castings (hint: that would not be chrome) you can keep the total weight very close to lesser priced small rims. You still have to worry about easily damaging rims (and tires) with the "big rim" world, so the combination just never struck me as a winning move from nearly any viewpoint but looks and deep pocketbooks.

my 2cents
Vince

 

We're questioning if the XKR has enough power to spin the 20" wheels and concerned if the suspension is robust enough to handle road undulations? Anybody that's driven one knows the car accellerates just fine with 20's, and why would you worry about the suspension when the 20's are a factory size? Were'nt the 20's the factory size on the Portfolios with larger Alcon brakes?

The car was designed to run on both 19's and 20's. Larger wheels do bend easier though, and I recall that's been an issue for some ever since the 17" and larger wheel became popular. I've read here that there are a number of wheel shops that straighten rims inexpensively, and I'm sure they keep very busy fixing wheels of all sizes with the condition of many roads.

Bruce

 

Please forgive, I 'm too new here to wish to cause upset, and will certainly bow to those that have lived in the Jag world far longer.

I don't think we were questioning of "can it"... more of a comment to yet another possible downside to big rims.
Ride quality and safety are the two greatest losses when talking about going to big rims, as mosesbotbol points out, a slight loss of available horsepower due to increased mass may mix in there as well... I think we were just trying to point out that there are in fact many down sides to the decision.



Brake size is often overrated to the common driver, because in the end, it is how much rubber you can keep in contact with the road that lets the brakes do their job regardless of brake size.
Road undulations are a big player here because a taller sidewall will absorb and mold itself around that rock or crack in the road without lifting the balance of its tread off the ground. the suspension does very little work. Thin tires cannot mold as easily and pass all the energy on the the suspension. When the suspension lifts the whole tire contact patch up and over the imperfection.


In the end it is still your car, and you should enjoy it your way. I just try to be helpful in pointing out that some decisions have a negative side to them as well.



Vince

 

Only Jaguar might be upset with your claim, Vince. I think the majority of XKR owners who have factory 20" wheels on their car realize there isn't a safety issue. Heck, I had mine on the race track within 24 hours of taking delivery, and in preparation put the car through its paces on the twisty and uneven roads leading to it. The car performs flawlessly on 20's on the road and the road course, and doesn't skitter sideways even under high cornering loads on poor road surfaces...a sure sign of well-controlled tire contact even at the limits.

Modern high performance cars are designed with advanced suspension systems that optimize tire contact with the large diameter wheels and tires that are chosen to maximize performance and safety, with the accepted compromise to ride quality that results. The more advanced suspensions incorporate electronic dampers/shocks that vary valving to lessen the impact on ride quality, and to maximize demanding driving performance and safety.

They do that by varying the damper shaft's low-speed valving (used to absorb wheel/tire motion under braking, acceleration, cornering, and undulating road conditions), and the damper shaft's high-speed valving (used to absorb wheel/tire motion typical over bumps and potholes). They do not rely on a tall sidewall to "mold" around bumps to maintain tire contact with the road. Modern high performance and competition tires of all sizes have very stiff sidewalls that barely flex enough to mount on the rims, never mind mold over bumps to maintain contact patch without the need for the damper to provide that function.

I see you have a Lexus IS. I suspect your comments about side walls and safety may apply to cars that were designed with smaller wheels and conventional dampers and then re-fitted with much larger wheels. That just doesn't work well in a number of regards unless suspension mods are also done. That's not the case with the XK, and you can be sure that Jaguar has successfully executed the suspension to handle both of its factory wheel sizes.

I would not be concerned about the performance and safety of using either factory wheel, with the driver's ability surely becoming the limiting factor long before the tires do.

Bruce

 

I have 20" Polished Cremona Wheels and I love Them and they Look Great !!

 

Bernie,

I see you're selling your 19" wheels...what have you decided to change to?

Bruce

 

Bruce, you are correct. All 2009 Portfolio models were equipped with 20" Selena wheels. The Alcon brake package was a $5,000 option; most Portfolios don't have them. Alcon-equipped cars don't have a spare wheel/tire due to the size of the 6-piston front caliper. For more info, see these posts:

https://www.jaguarforums.com/forum/x...rtfolio-59026/

https://www.jaguarforums.com/forum/x...-brakes-53693/ Includes a close-up of the Alcon rotor/caliper.

As for ride quality, I'm very pleased with the 20's on Michelin Pilot SS. Quiet, smooth, quick turn-in, good grip. A little "jiggly" at low speeds over bumpy surfaces, but that clears up at higher speeds. Can't say about how they do in the wet or tread life yet - only have 3K miles on them, with no apparent wear.
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