Slicks for 17" wheels

[jonasjmac]

Looking for recommendations for slicks for 986 boxster with 17" rims. Having trouble finding a place that sells them in the sizes that I assume I need. 205/50 and 225/40. I have seen some folks go to all four same size square tire set up which I have heard helps with some inherent understeer. I would imagine that's 4 225/40's?? Any thoughts or comments.

[steved0x]

I don't know the sizing for slicks but for rcomps some standard sizes in 17 are 225/45/17 front and 255/40/17 back, or you could fit a 235/40/17 in front like the spec boxster sizes. A lot of spec boxster folks run 255/40/17 square too.

[thstone]

The standard square setup is rear wheels/tires all around, not fronts. The rear 8.5x17 wheel and 255/40/17 tire will fit in the front just fine.

But you'll also need to upgrade the suspension (adjustable sway bars and maybe coil overs) because the car will go from the stock understeer to lots of oversteer in the square configuration. The suspension adjustments can bring it back to neutral or whatever you like.

[Mr Flat Six]

I don't know a lot about suspension. With that being said what are the adjustments that need to be made? I've heard of people running 255's with rear wheels on the front and was actually looking at my car today and wondering how it'd look/handle. I feel 225's or 235's would be fine for whenever I get new tires and I could keep my wheels. Anyway, its always nice to learn more!

[jakeru]

What do you plan on doing with the new tires?

What you plan to do with the tires is important, because there are a wide variety of specialty and racing tire products designed for niche applications, and one person's recommendation might not work out well at all for the application you particularly have in mind.

[thstone]

Originally Posted by Mr Flat Six

I don't know a lot about suspension. With that being said what are the adjustments that need to be made? I've heard of people running 255's with rear wheels on the front and was actually looking at my car today and wondering how it'd look/handle. I feel 225's or 235's would be fine for whenever I get new tires and I could keep my wheels. Anyway, its always nice to learn more!

225 or 235 on the front with 255 on the rear is a nice setup which will reduce the stock understeer. Either 225 or 235 will fit fine on the stock front wheel (regardless of what tire rack might say). No other adjustments are needed so its a nice upgrade on a stock car.

Running 255's on all four corners will not only eliminate the stock understeer but will also induce quite a bit of oversteer. To be clear, this doesn't mean that the car will be undrivable or unstable or squirelly at normal street speeds (the car will drive quite normally).

But the car will have HUGE front grip from the 255's up front and no understeer so it will be very tempting to push the car to see just how much front grip it has. Let me tell you, front grip like this can be intoxicating to those of us who like the corners. With high grip summer tires, you can literally just not brake before going around a regular street corner - the car will grip and make the turn (kids don't try this at home).

The problem is that as you push harder, you'll eventually get close to the handling limit and then the car will exhibit a strong tendency to oversteer, Boxster's rotate VERY quickly (due to the low polar moment of inertia) and if the driver isn't prepared or skilled at driving an oversteering car, it could result in something bad.

To adjust the handling back to neutral, adjustable sway bars (Porsche 996 GT-3 sway bar in front and the Tarrett Boxster adjustable sway bar in the rear) are installed with the front bar set quite a bit stiffer than stock and the rear bar set on the softest setting. This will bring the handling back towards neutral. Exactly how much adjustment depends on the other suspension components, the tires, and what handling characteristics the driver prefers.

[Mr Flat Six]

Wow thanks for the very informative post. I love hitting the mountain roads near me but I'm rather new to the sports car thing and have a lot to learn. I was more of a bike person and know a lot more about bikes than cars. I don't push it very hard at all on the street because of this and have been looking to get into autocross or driver education to become more skilled. My tires are fairly new and I feel like I'd like the grip a 255 would add but I have a lot to learn. I appreciate the detailed explanation.

[jonasjmac]

Thanks for replies. The car is strictly a track car as initially was planning on racing spec boxster but time nor money allows that currently. So now this a TT/DE car, so I'm not tied to any spec rules. The other benefit of the squares seemed to be allowing rotation of the tires to prolong the wear. So it appears running the squares would not necessarily require changing up suspension, gt3 control arms, even though eventually plan is fully upgrading suspension and sways from the current ROW setup.

[steved0x]

I have some extra wheels and I was thinking of running 17x8.5 on all 4 corners with 225/45 front and 255/40 rear. The extra rim width should help to give a little more grip and even tire wear on the front, I have read that running a tire on the widest approved wheel should give better turn in and response and my help dial.out another bit of understeer.

It is an interesting idea to me and I may try it. Has anyone ever run 225 on an 8.5" wheel, did you notice any benefit over running on a more narrow 7" wheel?

[Topless]

Do your suspension B4 mounting soft compound tires. Stock camber settings will destroy a $1600 set of 40tw tires in a few hours. Suspension work becomes very cheap when you go through 20 sets of tires in a season at $1600 ea.

[jakeru]

Originally Posted by jonasjmac

Thanks for replies. The car is strictly a track car as initially was planning on racing spec boxster but time nor money allows that currently. So now this a TT/DE car, so I'm not tied to any spec rules. The other benefit of the squares seemed to be allowing rotation of the tires to prolong the wear. So it appears running the squares would not necessarily require changing up suspension, gt3 control arms, even though eventually plan is fully upgrading suspension and sways from the current ROW setup.

Well, it sounds like as a driver's ed car, you would be driving it on the street to get to the track. Not trailered to events. Is that correct?

If so, I would suggest a slick would be inappropriate for your application. You should be looking at probably dot-legal radials in the ultra-high or "max" summer performance category, (https://www.tirerack.com/tires/types/perfCat.jsp?perf=EP) or possibly in the more durable of the r-compound categories
(E.g.: https://www.tirerack.com/tires/types/perfCat.jsp?perf=STRT )

I'm sure you'll find plenty of 17" options that fit whatever wheels you happen to have or prefer.

Since you're not competing, finding the "best" tire isn't really that important. So, don't sweat it... have fun!

[jsceash]

If you can get your car to the track without driving it there. The Hankook Ventus Z214 is an inexpensive choice in a slick tire 245-40-17 set of 4 are under $800 I turned some really good track times last year on these tires. I run the 18" size. The catch is I'm also running allot of (-) camber -2.5 to -3 with about 4" front and 4.5" rear ground clearance.

If you can't and have to drive to the track. Try the Nitto NT01 or Toyo R888. are as close to a slick as you can get and drive it on the street to the track.

[steved0x]

Originally Posted by Topless

Do your suspension B4 mounting soft compound tires. Stock camber settings will destroy a $1600 set of 40tw tires in a few hours. Suspension work becomes very cheap when you go through 20 sets of tires in a season at $1600 ea.

That is a good point, I am set up with -2.0 camber front, 0 toe, -1.6 camber back, little bit toe in, this is a good setup for 200 TW street tires like the R-S3. I ran a set of Nitto NT-01 on these same settings and corded my outside rear, and the other 3 tires were worn a little more on the outer edges, while the rest of the tire had 1/2 life left. I was bummed Rather than tinker with my setup at this time I'm staying on the hankooks for a while. The nittos were fun and a confidence builder, but I'm still leaving some on the table with the hankooks so I'm going to stay on them for a while until my skills increase to where I can take better advantage of rcomp tires.

[jonasjmac]

The car is not street legal, no horn, full cage, 5 points, not registered, and trailered to all events.

[jakeru]

Originally Posted by jonasjmac

The car is not street legal ... not registered, and trailered to all events.

Now you tell us! (This would have been good information to know about 3 posts earlier. It will definitely affect your optimal tire selection!)

Since you aren't driving on public roads, and can use the car as purely a track toy, please scratch all my previous advise on dot-legal tires, yada yada yada.

You actually do want, as your title suggests, and honest-to-goodness racing slick. Give throught to whether bias ply might be acceptable, or if you'll need a radial. Bias ply will handle "differently", and the car was not really designed for it. But oh man, will you have grip. An honest-to-goodness racing slick should grip more, last longer, and cost much less than a dot-legal option.

Really, the only racing slick I have experience with is Goodyear eagle. Funny enough, as your thread title suggests, they are not available in 17"! They do come in 16", and 18". You could look at other brands of racing slicks, or change your wheel diameters to a size that is compatible with available racing slicks. 16" wheels I've heard, will fit over front Boxster base brakes, but not "S" brakes. You might not to get a custom, lighteright racing wheel in custom dimensions to go with your slicks.
Goodyear Race Tires || Sports Car

http://www.racegoodyear.com/tires/pdf/Goodyear_Sports_Catalog_2015.pdf

Honest-to-goodness (non-dot compliant) racing tires are sized a bit differently than dot tire sizing. Here's how the sizing works:
DOT tire sizing:
Tire width (in mm) / section ratio (in percent) R rim diameter (in inches)

Non-DOT tire sizing:
Tire outside diameter (in inches) x Tire width (in inches) - rim diameter (in inches)

Maybe someone else who has more experience using non-dot P-car slicks can chime in with a suggestion. Hope that helps, and best of luck!

[jakeru]

Also, it wouldn't be cheap, but Hoosier R7's would be awesome. Even though they are DOT compliant.
http://hoosiertire.com/assets/circuit%20racing%2012%2020%2016b.pdf

Other DOT compliant R-compounds (for your application, stay away from autocross-specific compounds)
https://www.tirerack.com/tires/types/perfCat.jsp?perf=DRY

Wish I knew more traditional racing slick offerings for ya.

Since you're just playing around, if you found a local forum where people might sell their old race rubber, you could consider picking up a used set, for probably a small fraction than buying new. They wouldn't perform as good as new, but you're just playing around, used racing tires could totally fit the bill.

Clarifying your location (I've never heard of "RDU") could help us potentially suggest local options for you.

[Van914]

You can get Contential Race takeoff's in 17" sizes. Not a lot of $ and thy last a few DE's

[Topless]

Intended purpose matters when choosing tires. For a fun DE track only car I would probably run NT-01s and have a blast. For TT competition, I would choose tire compound and size very carefully to maximize my car class. Contact patch and weight are the two most important decisions to make in competition.