This posting is aimed at members with performance suspension and race car set up experience.

I have numerous challenges I am looking into regarding the suspension changes and upgrades I am making on my 2000 s-type with and LS3 conversion in it.

My present plan is to run front 19 x 11 rims with 295 to 315 x 35 x 19 tires and 19 x 12 rear rims with 335 to 355 X 30 X 19 tires. Does anyone have experience with optimizing the tire size to the car's wheelbase/weight of the vehicle so that the tires you run aren't too wide?

I am working through the geometry in the suspension, but am not sure how tire sizes will affect handling. Especially since the added rim width will all be towards the outside of the car.

I know that wider is better, but what is the limit of diminishing return?
What is the impact of staggered tire sizes on high speed handling - On the Track? I know that if the tires aren't balanced front to rear this can effect over-steer and under-steer.

Has anyone been through this exercise on other cars?

Thanks.

 

Wow! Those R very wide wheels for the front and rear. The max width for the rear is 295/35, and these will rub when suspension is deflected. I ran 285/35 on the rear of my 03 STR (est. 460 chp @ 480 lb/ft trq.). They were the max suggested. Handling can be greatly diminished running wide front tires. B careful.

 

Well running staggered is never helpful at the track. You tend to understeer more. 285-295 is the max you can really run with the stock fenders. I am running a 10mm spacer with 275 with an ET of 25 and the tires poke out past the fenders.

 

The fenders will be flared. 2-1/2" to 3" wider. The wheel well fender diameter will be increased from 30" to 31" to accommodate a nominal 27" diameter versus the standard 26.7" S-Types tire diameter. I need a larger diameter opening in the front for the tires to clear as they turn back and forth. It is already a tight fit for the standard/stock set up. Aesthetics will be important to me for the look of the flare. I have 2 to 3 different approaches I am looking at before cutting metal. I have a spare set of front fenders set up on a stand that will be my guinne-pigs. I have been using them for measurements. The S-types existing flare contour is a compound shape where I have not found any off the shelf flares, that in my mind will look good on the car. I've tried contacting a couple of the race car outfits that used to race S-types asking about how they did their fender flares, but have never received a response.

I will be using Corvette wheels. They are the only cost effective wheels with enough offset without having to purchase 2 or 3-piece custom wheels.
(Fronts are purchased, looking for a good price on the 19 x 12 rears.)

I will be using a custom coilover setup. The car has to be lowered 1 to 2 inches to accommodate the larger diameter tires, plus this will allow me to limit/control the suspension travel and stiffness of the car.

I know what am doing and will be doing to the suspension and body, but am trying to learn more about the effect the tires will have on the car.

 

The S-type is supposed to have around a 52/48 weight distribution. My LS3 swap took out about 80 pounds off the front of the car. I am adding back another 60 pound in rotor, caliper, wheel, and tire weight. Therefore I am assuming around a 52/48 distribution in my case.

This is a fairly neutral weight distribution. This would indicate to me that I can get away with staggered tire sizes without too much induced understeer.

My brother runs a Camaro and his C06 corvette on the track. His 3800# Camaro has a weight distribution of around 56/44. When he ran staggered wheels, he did see an increase in understeer, and the tendency for the rear end to pop out suddenly if he applied too much power. His 3200# Corvette has 315s in the front and 345s in the rear. the car has very close to a 50/50 weight distribution.

His Vette has a little over 500hp, with staggered widths and 50/50 wieght dist. The Camaro has around 300 hp with a 56/44 weight distribution and 315s in the front and back and it understeers. I will start with somewhere around 450hp, with plans to get the LS3 to 500Hp. The 52/50 weight distribution, combined with lots of power is why I chose to go with 305s to 315s in the front, versus say 285s, so that the fronts will more closely match the 335 or 345s in the rear and perhaps keep the car neutral on high speed corners.

If I am wrong on these assumptions let me know, this is why I asked the questions regarding tires in the firs place.

 

You seem to be on the correct track, the only other factor I am thinking about is the lack of a lsd on the Jag and how that will affect the handling as well.

 

That is in my long term plans. but LSD will be another $1K. You've probably seen on the Lincoln LS forum, how several Ford LSD's can be fit into our differential housing. (1999.5 to 2003 S-types) Newer S-types is another story.

 

There was an old forum member on here who was able to get a xkr lsd to fit by removing a tab or something in the S-type pumpkin.

 

^^^ I think clearance-ing the inside of the case that you're referring to is needed even for the 'bolt-in' lsd from quaife. Lack of an LSD in the STR is a real oversight on behalf of jaguar.

 

Tijoe, why R U doing this to an STR? Such a beautiful car. Sorry. No offence, just my thoughts.

 

It is not an STR. I have been modifying a 2000 S-type that had the regular V8 in it. I recently purchased a 2004 STR.
I purchased this car about 2 years ago with a blown engine and from the get-go the intention was to put in an LS3 with a 6 speed and then upgrade the suspension/tires to match. It has been a long slow process because after I put in the LS3 engine, I started a job that has had me away from home for the past 1-1/2 years. I am back home now and trying to build momentum and get the project moving forward. Working away from home, I could still purchase parts and make progress on suspension mods, but haven't had time to work on all the electrical needed to get the car running.

 

I am running the following set up:

-Forgestar CF5 staggered wheels in textured gunmetal finish
~Front: 19"x8.5" w/ 245/35/19 tires
~Rear: 19"x10" w/ 275/30/19 tires

My car is dropped on H&R springs, and the fenders are neither flared nor rolled (they have been left untouched) with zero rubbing. Are you going to use 19" wheels off a Corvette Z06? Those are handsome wheels but check out Forgestars, they are monoblock (i.e., single piece) and are Spun forged and cost about the same as cast wheels. They are also custome made for your car (keep in mind it takes 6 weeks). I ordered mine from Jurrian or modbargains.com, and he was cool enough to send me pics every now and then as it was being readied. His emails Jurrian@ModBargains.com

Interesting idea on the LS3 swap. Where I live, there is a shop called Billet Design Motorsports and the owner drives an S Type R himself as his daily driver! Anyway, he and I were talking and he said if he ever blows his motor, he is dropping in a 4.6L supercharged Ford Cobra engine from the 2003-2004 "Terminator" Cobras. I thought that would be a cool choice as Jaguar was owned by Ford during this period. Also, his shop does a lot of 2jz swaps on just about anything, including BMWs. He says it's cheap and easy to find these Supra engines/transmissions. Just giving some alternative ideas!

 

Sorry Joe. I believed it was the STR with the LS3.

 

I'm doing some research, and im planning to buy my baby some new shoes(04 s type 3.0) .the question i had for you was: i was wonder how did you know if the rim is going to clear the brake caliber? and also i was looking at your specs for your rims and tire, are you rubbing cause i was think about running 19" also. if have the time can you gave me a the down low? p.s . an awesome job on the jag

 

CEL, if underpressure may not notice this thread, send him a PM. then you both may bring it back here.

 

Thanks for the compliment! I knew my rims would clear the calipers because I have seen them on other cars with big brakes, plus I could tell visually the spokes were bowed out enough where the calipers would be under, and I also asked the poeple I ordered it through from modbargains and they confirmed it with the manufacturer (Forgestar). I have no rubbing issues, and they are as pushed out as you can get. I'm not sure what offset Forgestar decided to go with as I never inquired and they are custom built to order so not stamped with the offset. But with proper offset the STR can easily clear 8.5" in front and 10" in rear.

 

Lots of good information regarding basic set-ups, but my plans are a little more extreme. I am widening up my front fenders by 2-1/2" and 3" on the rear.
The 19" tires I am using will add another 1" diameter to the car, so that was part of the reason I posted my questions in the first place. Just trying to get more information so I don't miss anything while I am taking the time and money to mod the suspension.

Here is an image of one of the fender during an earlier stage of making a mold for for the flare. (Still lots of work to do...)

 

LS3, mad fender flares, soooo gonna follow the progress!