Need suggestions for tires DE car - 986 Forum - The Community for Porsche Boxster & Cayman Owners

RedTele58 · 10-07-2015, 07:34 PM

Hey Guys - I need some help with tire size for my new wheels, and also suggestions on brand/model.

They will be going on my '99 aerokit Boxster that I use some for street, but is mostly my DE car. My goal is stickiness and performance, not wear, but I'm not ready for a R-compound tire. I'm also not worried about all season performance - summer only is fine. The wheels are a GT3 replica wheel. Fronts are 8 1/2x18 52 ET, rears are 10x18 54 ET. I'll probably have to run 5mm spacers. I have the spacers and the longer lugs.

I'm thinking 225/40/18 for the front and 255/35/18 for the rear, but I'm not confident the rear size is correct.

I ran Re-11's this past season and was mostly happy with them. I'm also looking at Potenza Re-71R and Potenza RE 760 Sports. Also Potenza S-04.

No preferred brand, so I'm open to suggestions.

Thanks!

Rick

NewArt · 10-08-2015, 06:04 AM

the standard sizes are 225/40/18 and 265/35/18.

Burg Boxster · 10-08-2015, 06:51 AM

Good background info... one more piece:

What run group?

JayG · 10-08-2015, 07:35 AM

Also look at Hankook RS3, a very popular tire for AX and track on a street car.

another suggestion is get a set of 17" wheels for AX and track.
Tires are lower cost in 17's and you don't want to ruin those freshly painted wheels on the track

The Radium King · 10-08-2015, 08:17 AM

when you start pushing oem spec on wheel fitment other considerations come into play - lowered? lots of negative camber?

for my fronts, I am on et 53 8.5x18 rims, lowered about 1.5" and -2 camber. i am running 235 on the front and see some rubbing on the inside at full lock. I've got over 1/2" space on the outside, so am going w a 7mm spacer and 245s. that will add 10 mm (5mm inside, 5 mm outside) but push the wheels out 7 mm so all should fit fine (gain 2 mm on the inside and kill the rubbing, push out 12 mm on the outside to fill the gap).

on the rear i am -1.5 camber on 10x18 rims et 40, again lowered about 1.5". with 265s I've got lots of room, so going to a 275.

you want lots of tire on the front and going to a 235 is the standard method to dial out some of the factory-engineered understeer the car comes with. note that the balance of your car is more than a change at one end, but rather how the front and rear work together. 235 front and 265 rear tend to be a good combo to make a balanced car (and i am hoping that going to 245/275 is going to maintain that balance for me).

I've run the yoko ad08 as a combo street/track tire and like it. 180 tw, proprietary rcomp-ish compound, good in the wet, seem to last quite a while.

ps, still working on that gear we talked about.

seningen · 10-08-2015, 09:54 AM

Quote:

Originally Posted by JayG

Also look at Hankook RS3, a very popular tire for AX and track on a street car.

another suggestion is get a set of 17" wheels for AX and track.
Tires are lower cost in 17's and you don't want to ruin those freshly painted wheels on the track

I run Direzza Star Specs.

I happen to run 18" rims, but our 944 chump cars use Boxster 17's.

The Direzzas just hold up and grip well enough. On track, you can run them down to the polyester...... and they will still keep gripping.

They are OK in the wet on track.

Mike

CasualCarnivore · 10-08-2015, 11:20 AM

I'm running the RE71R's on my 18" rims. I absolutely love these tires and highly recommend!

John

NewArt · 10-08-2015, 02:25 PM

Hey folks, could you please type in the tire brand with the model. For those of us who don't have the Tire Rack catalogue memorized. Such as Bridgestone RE71R.
Thanks, Tires for Dummies.

LAP1DOUG · 10-08-2015, 02:30 PM

I run 245 Front / 275 Rear NT-01's for track events. These are designated as R comps, but are not really any stickier than the top shelf street tires like RE71 R's.

I had rather run a 255 Front / 285 Rear, which I have run in a Hoosier a couple of years ago, and they worked great. The problem I have is that you can only get good sizing for these in a Hoosier and ZII, and I really don't like ZII's, as they overheat too quickly.

Bridgestone does make a good low profile 255 F/285 R in the RE71R, but it is currently only available in Asia. I am hoping they will bring it to the USA for next season.

You need to pay attention to the overall diameter of the tires before ordering. Our cars are already geared way too tall, and larger tire diameters just exacerbate this problem. I had rather give up a little width in say going from my preferred 285 to a 275 in exchange for keeping the diameter down. Unfortunately, this compromise is way too frequently required.

As others have said, you need to be careful about what will fit on your car with your particular ride height, camber, etc. Take lots of measurements, and pay close attention to all of the manufacturer's dimensions.

Good luck.

RedTele58 · 10-08-2015, 03:17 PM

Hey Guys - all good info so far. I appreciate it.

I did forget - the car is sitting factory US spec M030 suspension. When I had the suspension freshened this past spring, I had the shop set everything to factory M030 numbers (castor, camber, etc).

I do have some concern about the car pushing an 18x10 rear wheel. It does look awfully big sitting next to a factory 8.5x17. I may be defeating the whole purpose of what I'm trying to do with making myself faster and the car more stable/neutral. Thoughts on that?

steved0x · 10-09-2015, 06:12 AM

Quote:

Originally Posted by LAP1DOUG

You need to pay attention to the overall diameter of the tires before ordering. Our cars are already geared way too tall, and larger tire diameters just exacerbate this problem. I had rather give up a little width in say going from my preferred 285 to a 275 in exchange for keeping the diameter down. Unfortunately, this compromise is way too frequently required.

+1

In addition to the gearing, the fronts especially do not have much room and you can't fit a 245/40/18 - it is too tall and it contacts the strut perch. I bought a set of Cayman wheels with that size mounted in the fronts and it didn't fit. (987 run a taller tire than 986 so it fit on the Cayman). The stock diameters are 25.1" in the front and 25.3" in the back - you can fit bigger in the back (I test fitted a 25.9" 285/35/18 RS on a 9" wheel in the back, not ideal for gearing but it fit) but the 25.7" 245/40/18 RS3 on an 8" wheel were too tall

I think a 10" rear wheel is OK, I have heard that 11 is where you get into a lot of trouble.

I have heard that the Bridgestone RE71R is the current 200tw "cheaty" tire in Autocross - it is really more like an R-comp, sticks like the devil, wears super fast, and I have heard it heats up really fast so it is perfect for Autocross or for getting a flying lap or 2, but for a 25 minute session it gets hot quickly and slides around a lot.

The guys in my autocross group that run chumpcar like the BFGoodrich Rival - the first one, not the "S". They say they hold up well.

I personally run the RS3 and it hold up well, I typically run 20 -30 minute sessions and I have not had them fall off due to overheating. I like the RS3 because it is directional and around halfway through their life I flip them on the wheels to get more even wear.

Discount Tire Direct often runs $100 off a $400 purchase on eBay with free shipping and folks use that to stock up on the Nitto NT-01, and I think the 18" sizes qualify with 2 orders of 2 tires and they get $200 off.

The Radium King · 10-09-2015, 11:30 AM

so with a 245/35 on the front, would you run a 275/30 on the rear? running a 275/35 on the rear starts to push the tolerances of the ABS?

Topless · 10-09-2015, 04:02 PM

Goals:
Fast and fun DE, no trophies or championships involved, good balance, and tires that work with M030 and mild camber. Not running Red group.

If it were my car I would save the pretty 18s for street and run 17s. 235/40/17F, 255/40/17R. These are the Boxster Spec Race Car sizes and work well with 201 hp. Too much tire can choke these cars until you strip them and run R-comps or add a 3.4L motor. RS-3, Rival, RE-11, RE71R, AD-08, Star Spec are all 200 tw and perform very well in continuous lapping. With 18s and careful attention to fitment you could run 245/275 but it might double your tire costs and probably not be much faster if any.

Get a performance alignment and max out your negative camber to make full use of your tires.

Good luck!

thstone · 10-10-2015, 01:13 PM

Quote:

Originally Posted by Topless

Goals:
Fast and fun DE, no trophies or championships involved, good balance, and tires that work with M030 and mild camber. Not running Red group.

If it were my car I would save the pretty 18s for street and run 17s. 235/40/17F, 255/40/17R. These are the Boxster Spec Race Car sizes and work well with 201 hp. Too much tire can choke these cars until you strip them and run R-comps or add a 3.4L motor. RS-3, Rival, RE-11, RE71R, AD-08, Star Spec are all 200 tw and perform very well in continuous lapping. With 18s and careful attention to fitment you could run 245/275 but it might double your tire costs and probably not be much faster if any.

Get a performance alignment and max out your negative camber to make full use of your tires.

Good luck!

What Dave said! ^^^^^. At this point, you want a stable, repeatable, handling package and the lower the running costs means the ability to afford more seat time!

By the way, I love the color of those wheels!