944S Tire Size Questions - Square fitment or no?

[MrBattleRabbit]

So I'm looking for some up to the minute answers on tires for my 944. I'm looking for the ideal tire size combination for my 944S. The car will be used primarily on the street, but it has to stand up to occasional track days(HPDE type stuff), and the odd autocross. I do not need or expect to be the fastest guy at the track or at the autocross- I am a newbie and I just want a setup that works well on my car.

The car currently has a set of narrow spoke Cup wheels on it(I think they're from a 968 originally). Tire sizes are stock, so 205-55r16s on the front, and 225-50r16s on the rear. The current tires are Bridgestones and they are just Meh. I got them because the previous tires were shot and I needed something to tide me over until I got a few other things on the car sorted out.

My new tires, for a variety of reasons, NEED to be Michelins. This is going to mean going up at least to a 17" wheel. I think for my use the Pilot Super Sport(or the PS4S when it comes out in 17" sizes) will be my ideal tire. The Pilot Sport Cup 2 is tempting, but I think that is better suited to someone with the opposite usage patterns to me(IE primarily track/autocross use, only street driving to get to the track/autocross). If I'm wrong about that, please correct me!

So the sizes available with the PSS in 17" are as follows:

• 205/45ZR17(88Y)
• 215/45ZR17(91Y)
• 225/45ZR17(94Y)
• 235/45ZR17(97Y)
• 245/40ZR17(95Y)
• 245/45ZR17(99Y)

And for the Pilot Sport Cup 2 in 17" are just 215/45zr17 and 255/40zr17... I don't think either of those are a good fit for me. Options are better in 18", but that just seems too large.

Porsche's recommended fitment is staggered:

225/45 ZR 17 7,t Jxl7 AH 65mm Front Summer tires
255/40 ZR 17 9 Jxl7 AH 55mm Rear Summer Tires

But I've read on this forum and others that going to a square fitment(IE, a 245/40zr17) might be a better option for overall performance.



So, PelicanParts users, should I be looking at moving to a square stance for improved performance, or will I be better off going with Porsche's recommendation? Is there some third option that I'm not considering that I should be?

[smudo]

With those wheel and tire sizes I would go with 225/45 in front and 245/40 or 245/45 in the rear. The 245/40 tire will have slightly smaller than OEM size outer diameter and 245/45 will have bigger outer diameter. These tire sizes should work fine.

[MrBattleRabbit]

Originally Posted by smudo

With those wheel and tire sizes I would go with 225/45 in front and 245/40 or 245/45 in the rear. The 245/40 tire will have slightly smaller than OEM size outer diameter and 245/45 will have bigger outer diameter. These tire sizes should work fine.

I guess I should have been more clear- would it be to my benefit to get wheels that are the same width front to rear? Since I'll be wheel shopping anyways should I be going with Porsche's recommendations, or should I just get a 17x9 front and rear and run the same size tire front and rear?

[v2rocket_aka944]

I am shopping for wheels and tires and like the idea of going "square"...only have to buy one tire size, so if you race or whatever you can stock up easier.

Wider rear tires can promote understeer, wider front can make oversteer...square should make it more neutral, but all this depends on your existing suspension setup.

[flash968]

going square can have a number of advantages. it better controls understeer, and allows for tire rotation.

be aware that in going to a 9" front rim, the steering will get heavier, you will gain tramlining and wander, wear out bushings, and strain suspension components a lot more than you do now. everything will need to be fresh. i've done it, and liked it, but i spent a small fortune on the suspension so as to handle it, and i like a heavy steering wheel. when i sold my car, the first thing the new owner did was pull the 9" rims off the front, and put 8" rims on there, with a tire 2 sizes smaller than what i had.

choices

[Rasta Monsta]

OT:

That is a great looking car. Thanks for posting, those Cup wheels are tasty AF.

[smudo]

Originally Posted by MrBattleRabbit

I guess I should have been more clear- would it be to my benefit to get wheels that are the same width front to rear? Since I'll be wheel shopping anyways should I be going with Porsche's recommendations, or should I just get a 17x9 front and rear and run the same size tire front and rear?

Nothing wrong with your post - I did read it wrong I also had the same choice for the next season as I wanted to have 17 inch wheels for the track instead of OEM 16 inch phone dials on which I put staggered tires setup with 225/50 all around. I liked that set-up - it was neutral as it can be with moderately modified suspension (some understeer in slow corners, neutral in most corners on race track where you go through with 45 - 65 mph and you had to pay attention in fast corners (88 - 100 mph) - especially if you needed to slow down in those corners or do braking right after them. However, it came more from suspension setup and not only from putting on staggered tire set-up. If you want to have fun on the track and are not competing with anyone, 16 inch wheels IMO are the best set-up for those cars as they were designed for 16’’ wheels. If you modify the suspension, you can go to 17'' or 18''.

I thought about new 17x9 Fuchs wheels (ET 55mm) (OTTO FUCHS Felgen: Shop), but was not sure whether it would clear the front fender with 255/40 tires. Those are very light wheels 7.95 kg in 17x9 size, but cost EUR 600 per wheel here in Europe. I ended up with used 996 17x8.5 and 17x9 wheels that are also rather light - at least if you go with Porsche OEM wheels (the front is around 9 kg and the rear around 9.7 kg which is not much more if compared to OEM phone dials, 8.4kg and 9kg respectively in 16x7 an16x8 size).



I would have used 255/40 tires all around, but after some reading about the tire width I found out that the gain in corner grip (on dray track) is not proportional to the increase of the tire width (unless you use more aero), and you also have to consider the things that Flash mentioned, especially that you will drive the car also on the street. In the end I ordered 235/45 and 245/45 Yokohama Advan Neova AD08r tires. Will see how this will work for me. I have adjustable rear sway bar that was set on the softest setting, thus if I will have too much understeer with such set-up, it will be an easy fix.

[MrBattleRabbit]

Originally Posted by flash968

going square can have a number of advantages. it better controls understeer, and allows for tire rotation.

be aware that in going to a 9" front rim, the steering will get heavier, you will gain tramlining and wander, wear out bushings, and strain suspension components a lot more than you do now. everything will need to be fresh. i've done it, and liked it, but i spent a small fortune on the suspension so as to handle it, and i like a heavy steering wheel. when i sold my car, the first thing the new owner did was pull the 9" rims off the front, and put 8" rims on there, with a tire 2 sizes smaller than what i had.

choices

Good point about the strains on the front end- I really hadn't thought about that. My front end is reasonably fresh if I remember correctly.

Since the car will be used mostly on the street, maybe there is some benefit to going with Porsche's recommendations. The car is a wonderful roadtripper, and I'd hate to have it turn into a tramlining handful on the highway.

Some other modifications are coming in addition to the new wheels and tires. There will be uprated springs/torsion bars, along with adjustable Konis and Lindsey Racing's adjustable M030 swaybar kit. My car was not particularly well optioned stock, so I want to tighten it up a bit!

Originally Posted by Rasta Monsta

OT:

That is a great looking car. Thanks for posting, those Cup wheels are tasty AF.

Thank you! They were the PO's addition, not mine. I did remove the decaying stone guards though, which really did wonders for the look of the car.

Now to find some Euro bumpers....

Originally Posted by smudo

Nothing wrong with your post - I did read it wrong I also had the same choice for the next season as I wanted to have 17 inch wheels for the track instead of OEM 16 inch phone dials on which I put staggered tires setup with 225/50 all around. I liked that set-up - it was neutral as it can be with moderately modified suspension (some understeer in slow corners, neutral in most corners on race track where you go through with 45 - 65 mph and you had to pay attention in fast corners (88 - 100 mph) - especially if you needed to slow down in those corners or do braking right after them. However, it came more from suspension setup and not only from putting on staggered tire set-up. If you want to have fun on the track and are not competing with anyone, 16 inch wheels IMO are the best set-up for those cars as they were designed for 16’’ wheels. If you modify the suspension, you can go to 17'' or 18''.

I thought about new 17x9 Fuchs wheels (ET 55mm) (OTTO FUCHS Felgen: Shop), but was not sure whether it would clear the front fender with 255/40 tires. Those are very light wheels 7.95 kg in 17x9 size, but cost EUR 600 per wheel here in Europe. I ended up with used 996 17x8.5 and 17x9 wheels that are also rather light - at least if you go with Porsche OEM wheels (the front is around 9 kg and the rear around 9.7 kg which is not much more if compared to OEM phone dials, 8.4kg and 9kg respectively in 16x7 an16x8 size).


I would have used 255/40 tires all around, but after some reading about the tire width I found out that the gain in corner grip (on dray track) is not proportional to the increase of the tire width (unless you use more aero), and you also have to consider the things that Flash mentioned, especially that you will drive the car also on the street. In the end I ordered 235/45 and 245/45 Yokohama Advan Neova AD08r tires. Will see how this will work for me. I have adjustable rear sway bar that was set on the softest setting, thus if I will have too much understeer with such set-up, it will be an easy fix.

Thank you for the very thorough reply! As I noted in my response to Flash968 there will be some suspension tweaks to go along with the new wheels and tires.

Your tire sizing is very close to Porsche's recommendations, and I really appreciate your insights.

As I noted in the first post I actually need to use a Michelin tire, which will mean going to a 17" wheel. I do quite like the combination of aesthetics and ride quality my 16s give me, but in the interest of using the Pilot Super Sport or the new PS4S, I'll deal with the compromise I suppose!

[MrBattleRabbit]

Originally Posted by smudo

I thought about new 17x9 Fuchs wheels (ET 55mm) (OTTO FUCHS Felgen: Shop), but was not sure whether it would clear the front fender with 255/40 tires. Those are very light wheels 7.95 kg in 17x9 size, but cost EUR 600 per wheel here in Europe. I ended up with used 996 17x8.5 and 17x9 wheels that are also rather light - at least if you go with Porsche OEM wheels (the front is around 9 kg and the rear around 9.7 kg which is not much more if compared to OEM phone dials, 8.4kg and 9kg respectively in 16x7 an16x8 size).

Interestingly, these are available in the US. I didn't look when you posted them originally(I'm not really sure why), but they do have a US vendor.

http://www.fuchsfelgeusa.com/wheel/16599/fuchsfelge-fuchs-17

The pricing isn't bad, so I may come back to them when the time comes!

[SloMo228]

I have 225/45/17 tires on all four corners of my '87 S and I like it a lot. I don't think any wider is necessary for the S's power output. If you have a Turbo, then yeah, the big rear tires start to make sense.

With a 26.8mm front and a 19mm adjustable rear sway bar I have good, neutral handling with the square setup. I also have 200lb/in front springs matched with 26mm rear torsion bars, plus Koni yellow shocks/struts.

The only thing I would change is to get slightly wider rims. I have the 225s on 7" wide Cup II wheels, ideally a 7.5" or 8" width would let the tire work better.