Staggered Set-up wheels + tires

Howdy y'all

So I've autocrossed for the past year now (not seriously at all) and am hoping to do so with my 944 once the conversion is over. I'm no where near ready to start considering wheels/tires but since i'm bidding on a set of wheels for a good deal on ebay this has come up. Considering non R compound tires only.

Here's my dilemma: hoping to win a staggered set of 17x9 and 17x8 wheels. What do I do about tire size and how adverse is it to run a large staggered set of tires? For example, if I want to run 275's in the back my choice for non R compound is a Nitto NT05 and nothing else really. That would leave me with a 235 in the front with the NT05.... what complications can i expect to see with such a difference in tire widths?

OR if i step the rear down to a 255 I can run any of your common autocross tires. RS-3, star spec II, blah blah blah. In most cases, this allows a 255 on the rear and 245 on the front...

What would you do?

Thanks!

I am running 245/45/17 and 275/40/17 Falken RT615K; have you looked at those yet?

My wheels are very wide (9" front and 10.5" rear) but i always liked how the car handled with these sizes and finding anything wider than a 275 in a 17" tire is tough. 275 is a good width for my power levels once the tires are warm and i have not yet wished i had more grip even with 380whp (LSD equipped also).

I find this setup is very balanced, i think a 235/255 should be comparable with slightly less overall grip.

These tires are good for auto-x, but i would not expect to be super competitive against the 'big dogs'. DE they are ok, but start to get greasy towards the last 2-3 minutes of a 20 minute session. The rubber compound with the 615k is supposed to handle heat better than the original 615 and it does, but still is the Achilles heal of these tires i think. I never was the type to bring a garden sprayer with water to cool the tires off between runs but i have started considering it. I might get dirty looks from water conservationist spraying my tires with water in SoCal though..

Ah thanks for the suggestions. Looks like i have TWO options to run 275's while avoiding R compounds.

Any modifications to fit 9's in the front? Refreshing to hear that you aren't having much problems running staggered sets. I hear horror stories about lots o understeer.

At the minimum you need coil overs in the front for the smaller diameter springs. Also my turbo came from the factory with the rolled front fenders so that may be a factor also.

Another tire ive tried was the Kumho XS, also in 245/275. These tires were actually pretty good, comparable to the RT615k, i felt they handled the heat better than the RT615k also.

shoot! I hate when tirerack doesn't carry the full line of sizes of tires. I looked at the XS's and thought they didn't sell them in a 275 on a 17" but it looks like just tirerack doesn't sell them.

Thanks for the suggestions! im gonna double check other tires now on the manufacturers websites

Square!! I ran staggered for a season and never could find balance. Switched to 17x9 front and back with 255/40 tires and never looked back. ET55 wheels with rolled fenders and 15mm spacers in back, late offset car.

And Jon, tire temps come down really quick. No water needed, just a cool-down lap is plenty.

Rich

hmmmmmmm. Interesting. I have an early offset car and unfortunately I only "won" the 8" wheels last night on ebay. Was hoping to get the 9"s so I could see how they fit on the front and then depending on that buy another set of 9's or a set of 8's. Oh well... that's the way the cookie crumbles.

I'll keep reading about handling characteristics but I do enjoy all the discussion here

Square! I run the same wheels as Tim, OEM Cup 2's, 17x9 ET55 and I run 275-40-17's on them all round.

shoot. you are not making me happy about paying for the 8's i just won

I like the 235/255 idea for auto cross.

Like most novice Porsche owners, I’d like to have a car equally good on the street, the track and on auto cross circuits. But, I have to realize that the purpose built cars will spank me on "their" playgrounds.

The track guys will almost always yell “square and wide”. That’s because it works, While I might argue that wider is usually safer but not necessarily faster, it still works. A road course is typically pretty fast and has fast sweeping turns and long braking zones. A loose car (oversteer) is usually faster and easier to drive in this venue than a tight car (understeer). A square setup is inherently loose and very easy to setup/tune on most tracks. This makes “square and wide” a very successful tactic for track cars.

Auto cross is a different animal. Slow speeds, tight corners and single laps mean tire and brake temperatures are of little concern. It also makes a loose car as hard to drive as a tight one. A staggered set up would likely make the car easier to tune to a neutral feel. If I were to build a purpose built solo car, I’d go with as small of a rear tire as I could get away with, keeping an acceptable level of traction under both acceleration and braking. Then drop the front a couple of sizes and make the suspension very adjustable.

In most racing circles, it is generally accepted that sprung weight verses unsprung weight has a ratio of 10:1. This means that shaving 20 pounds of weight off of the tires, rims, rotors, calipers, hubs etc. has the same performance advantage as losing 200 pounds of weight supported by the springs, and your minimum class weight hasn’t been affected much. Still want big wide tires/brakes you might not need? You could be slowing your car down significantly with good intentions.

I disagree. Now take this with a grain of salt as there's no "one" answer here, there's only the right answer for you and the way you drive and want the car set up.

My feeling is auto-x, because of the tight turns and lower speeds requires a car that doesn't push/understeer at all. That makes the car extremely difficult to get to turn in and will cost you bucket loads of time as you have to overly slow down in order to get the car to turn in.

In both auto-x and track driving I *much* prefer a car that I can rotate with the gas pedal, whether that's through power on oversteer or lift throttle oversteer. It lets you instantly point the nose of the car and get back on the power as quickly as possible.

All of our hybrid cars here have the ability to steer with the gas pedal, there's no reason to hamstring that.

There's simply no place for a staggered wheel/tire setup on one of these cars that's going to be in a track/auto-x environment unless you're just going out for fun on your sole set of street tires/wheels.

docwyte wrote:I disagree.  Now take this with a grain of salt as there's no "one" answer here, there's only the right answer for you and the way you drive and want the car set up.

My feeling is auto-x, because of the tight turns and lower speeds requires a car that doesn't push/understeer at all.  That makes the car extremely difficult to get to turn in and will cost you bucket loads of time as you have to overly slow down in order to get the car to turn in.

I agree with 100% of this.

docwyte wrote:In both auto-x and track driving I *much* prefer a car that I can rotate with the gas pedal, whether that's through power on oversteer or lift throttle oversteer.  It lets you instantly point the nose of the car and get back on the power as quickly as possible.  

I agree with this as well, however, you’re comparing understeer and oversteer, not either one with a perfectly balanced car.

The top SCCA Solo guys go through the corners literally on two wheels, that’s a perfectly balanced car. If either end of the car looses traction (the definition of understeer/oversteer) you either push through the turn or you catch it from spinning out and you leave time on the ET clocks. Auto-X is as much a chassis tuning competition as it is driver’s skill. While steering with the throttle is fun and spectacular to watch, spinning tires are not accelerating the car as fast as maximum traction. Do that at a national meet and you’ll get your butt handed to you on a platter by the really good tuners.

I should also point out that tire stagger is far from the only chassis adjustment available; it’s simply not a subtle one.

I have been running a square setup on my SCCA Auto X car and love it. I have 285's all the way around on 18 x 10 wheels, car rotates good, still some more suspension tuning to do next year to make it better.

Andy

So sounds like i'm going to have a pair of new 17x8" wheels for sale...

Enjoying the conversation guys!

To add to the conversation,

I would assume the effect of a staggered setup is less if the wheels/tires are closer in width?

My point being is that with 8''s on the front and 9''s on the rear I could run 245/255 star specs and have darn close to the same tire width.

Increasing front tire width will increase front axle traction regardless of stagger. The effect will be decreasing understeer or increasing oversteer depending on the cars original behavior.

So how much of an effect does a torsion bar (anti-sway bar) have in comparison to the tire?

Could I use a really fat rear and relatively narrow front sway bay to overcome the inherent understeer I would see with a 245/275 stagger? Or would the balance likely be too far off to begin with?

This goes along with what docwyte said.

A car/driver combination is a team. You tune a car to compliment a particular driver, when that one driver is comfortable in the car, you should have a good team. Cars are all different, drivers are all different. The next driver might think that car is a POS. You can even tune two cars to yourself with identical setups, one works, one doesn’t. Go Figure.

The amount of variables involved in tuning a suspension/chassis would make a “how to” book a series of books the size of an old set of encyclopedias. I’m surprised there isn’t a site or forum dedicated to that. It’s not all that cut and dried, even for professionals.

This means that no one has right or wrong answers, only opinions. This is also why everyone is hesitant to answer questions or comment. With that said………..

FrostedFlakeJake wrote:So how much of an effect does a torsion bar (anti-sway bar) have in comparison to the tire?

Could I use a really fat rear and relatively narrow front sway bay to overcome the inherent understeer I would see with a 245/275 stagger? Or would the balance likely be too far off to begin with?

I don’t like the 245/275 combo on your rims because star spec tires call for a 235-245/255 on 8/9” rims. Too narrow a rim will bulge the tire and you’ll have to lower air pressure to get a good contact patch. If anything other than a recommended rim, I’d go with a wider rim and run more pressure for a firmer ride and perhaps more response.

The torsion bar is a pretty significant adjustment as it’s more or less the rear spring. Sway bars will also adjust over/understeer but are better suited to control camber adjustments during very hard turns.

I’d use tire pressure, camber and sway bars to adjust tire temps across the tread (contact patch), and tire size, springs, weight and ride height to adjust over/understeer. Replacing torsion bars with coilovers will make rear spring adjustments much cheaper and easier in the long run.

I don’t like the 245/275 combo on your rims because star spec tires call for a 235-245/255 on 8/9” rims. Too narrow a rim will bulge the tire and you’ll have to lower air pressure to get a good contact patch. If anything other than a recommended rim, I’d go with a wider rim and run more pressure for a firmer ride and perhaps more response.

The torsion bar is a pretty significant adjustment as it’s more or less the rear spring. Sway bars will also adjust over/understeer but are better suited to control camber adjustments during very hard turns.

I’d use tire pressure, camber and sway bars to adjust tire temps across the tread (contact patch), and tire size, springs, weight and ride height to adjust over/understeer. Replacing torsion bars with coilovers will make rear spring adjustments much cheaper and easier in the long run.

Well i wouldn't be able to run star specs because they don't make a 275 in 17"s. Most of the crowd favorite 200 UTQG autocross tires only go to 255 in 17"s. Star specs, RS-3 v2's, Rival S, etc.

Toyo R1R is another 200 tire i can run in 275/245. All the tires i'm considering for 275/245 have their minimum rim width at 9 and 8" respective.

Are you saying that running the minimum recommended rim width would also cause me to have bad contact area?

Just trying to understand

I'm also concerned with how much effort it would to take to fit 275's in the front. From my stock 15" fuchs, the 8" wheels i bought have the same inner clearance in the front but get pushed out 26 mm which is practically 1". Putting the 9" wheels in the front will give me 17mm less inner clearance and push the lip out towards the fender 33mm more then stock. I guess i better get under the car to try to get an idea of kind of clearance I have.

FrostedFlakeJake wrote:
Toyo R1R is another 200 tire i can run in 275/245. All the tires i'm considering for 275/245 have their minimum rim width at 9 and 8" respective.

Are you saying that running the minimum recommended rim width would also cause me to have bad contact area?

Probably. The recommended rim for a Toyo R1R in a 275/40ZR/17 is 9.5” so a 9” will very likely bulge even though the recommended range is 9-11”.

https://944hybrids.forumotion.com/t2666-tire-size-width

Pretty good article:
http://www.motoiq.com/MagazineArticles/ID/3974/How-to-PROPERLY-select-and-size-TIRES-for-PERFORMANCE.aspx

Bottom line, there's a lot more too it than "wider is better".

I doubt it'll bulge. I run 275-40-17 Nitto NT01/Toyo RA1's on 9" wheels. They don't bulge. Don't put too much credence in those numbers.

Rich L. wrote:Pretty good article:
http://www.motoiq.com/MagazineArticles/ID/3974/How-to-PROPERLY-select-and-size-TIRES-for-PERFORMANCE.aspx

Bottom line, there's a lot more too it than "wider is better".

+1

Pretty good article:
http://www.motoiq.com/MagazineArticles/ID/3974/How-to-PROPERLY-select-and-size-TIRES-for-PERFORMANCE.aspx

Bottom line, there's a lot more too it than "wider is better".

+1, very good article!

This makes me much more comfortable running 255's in the rear... I know what the article said about tread width relative to rim width, but I still think i'll run Star Specs in 255's with a 10" tread width on my 9's in the rear and 245's with a 9" tread width on my 8" wheels in the front.

Thanks for the great discussion fellas!