nor do they make 'em in 993 wide-body sizes *NM*

Motor Trend Three Tire Review

Driving a new-to-me '09S in Aqua Blue Metallic. It does .5 past light speed. I made the Kessel run in less than 12-parsecs.
Motto: If you have your top up, that storm outside had better have a name!
Motto 2: Having the top up on a convertible is an oxymoron. Don't be a (oxy)moron.

Maybe that means it understeers a lot, or that it's more communicative.

The hot Bridgestone is the RE-11. Its very sticky, holds up rally well on the track and Auto-X, ont he downside it is HEAVY and has lots of tread noise on the highway - it does not understeer appreciably more than others - it just annoying on the road. Ont eh track those things matter little.

Conversely, the PSS is all things to all people with three limitations:

1. it actually begins to chunk and fall apart if driven to the limit on rough surfaces, such as your local AuotX. We had several drop pieces the size of mid-sized pea gravel. Alarming! Michelin replaced both sets at their cost under the satisfaction warranty.

2. It is not available in the proper or even alternate sizes for 17" 986s. The rear 255/40-17 is not made.

3. Contrary to the article, most found it to have less warning when it began to slide. (more abrupt break-away, but strong to that limit)

I wanted the PSSs but cant get them. I considered the Bridegstones but chose the Yoko semi track tires N-08? I forget.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

I just put a full set of the Super Pilot Sports on my 2003 S.



Edited 1 time(s). Last edit at 05/24/2012 10:38PM by TomBrand. (view changes)

Unfortunately they don't make them in the 17" Boxster size.

...might I ask some advice on offsets?

I have OEM 7.5 x 18 w/50 mm fronts and 9 x 18 w/52 mm rears.

Another OEM 18" option for my '99 are 8 x 18 w/50 mm and 10 x 18 w/47 mm.

The wheels I'm considering are 8 x 18 w/ 54 mm fronts and either 9 x 18 w/ 43 mm or 10 x 18 w/40 mm rears.

Appears the new fronts will have 10 mm less inner clearance and extend the outside edges by 2 mm from my current setup. Will that work/fit?

Which option rear should I select, 9 or 10 inch width? 9 inch width would be 9 mm more inner clearance and stick out an additional 9 mm from my current setup. 10 inch width would be 1mm less internal clearance and stick out an additional 25 mm.

Those numbers are the differences from my current rim/offsets. But since there's a larger width rim that was available from the factory, can I use those numbers to help confirm the max widths/offsets I can use? If so, the differences as compared to the larger wheels would be fronts 4 mm less inner clearance and outer edge reduced by 4 mm. And the rears would be 17 mm more inner clearance and reduce outer edge by 9 mm for the 9 inch width. And 5 mm more inner clearance and stick out an additional 5 mm.



Edited 1 time(s). Last edit at 05/25/2012 11:15PM by bar10dah. (view changes)

I bought my second Boxster and the inner edges of the rears were showing a bit of wear. My mechanic at the time, who was experienced at setting up cars for the track, knew what the affect was on handling and wear of various settings so he set me up with a setting that was within the stock limits but which was biased towards even wear. Then I replaced the tires. Those rears wore so well I still had great tread when I finally replaced them over concerns about their age. I could have run them to 25-30k which is great for a Boxster. And it wasn't because I babied them...I like curves.

You can do wonders with the right setup.

Last Summer we noticed that our rear tires were wearing faster on the inside. The front had similar issues, but not as bad. We had the wheels balanced and the camber adjusted when we put on the Winter tires.

When we pulled the Winter tires off the Boxster, the rear inside edges was pretty beaten up. We won't be able to use them again next year.
Tire inflation was probably not the cause as the pressure was at 32 for the rear when removed.

The question is...what else could be causing the problem?

I have had my alignment checked several times, but it has NEVER varied.

Rear negative camber is large. Just look at the car sitting on a level surface from the rear. QED. Inside will wear prematurely unless offset by spirited driving. My rears wear nearly 100% evenly, but that's with lotys of track time to wear the inside, and to roll the camber over to zero.

Your wear is completely normal for a car driven normally on public roads. That's the price you pay - hese things eat rear tires/ Typical rule of thumb is 2 rear sets per front set.

(except my last front set lasted two days at mid ohio)

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Guess we need to drive the Boxster into the corners harder!!!

I would nto give up the negative camber ( in fact i'm dialing more into the front) - but for 95% of drivers it may not be needed and maybe you can eliminate a bit, get better wear, and never notice the lost grip at 8/10ths and above.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The rear set up had lots of camber, and owners complained of having to change the rear tires something like every 5 to 7,000 miles. Acura subsequently dialed back the camber, although the change may've adversely affected the handling balance somewhat.

and they will tell you camber in the alignment is a trade off. Better cornering at the limit requires a pretty aggressive setting, but it can be dialed back for the street. It will of course result in positive camber and less grip at the limit but get much better life from the tire by wearing the tire across more of the tread. It's a choice between objectives.

This car in the picture is set up for the track with a fairly aggressive camber. Under hard cornering you can see the left rear wheel is pretty close to zero camber with suspension compression and lean. The right rear is showing the opposite of an exaggerated camber with one edge of the tire not touching.



Dave - 06 987 S coupe SG/NL; gone (but still my first love): 03 986 AS/GG/BK;

when it comes to inner edge tire wear.

In one case, when I took my Boxster to an indy alignment shop (Custom Alignment) to get new tires and the alignment done the manager came to me and said that the car was done, but mentioned the rear camber was at its max allowed. I immediately wanted it brought into spec and he told me it would add more money to the bill (which would have brought the cost up over that from the dealership) but at the same time he told me there was no need. The excessive negative camber would not affect rear tire wear one itoa. This one one of my two major concerns. The other was how the car would feel/steer/handle.

He proved to be right.

Over and over again when I have my cars aligned, it is the rear toe (and in a rare instance the front toe) that is out and which accounts for the inner edge tire wear. (I just posted a few days ago pics of the rear tires from my Boxster after 30K miles and while the center of the tread was worn away the inner/outer edge wear was about the same. And the alignment has the customary negative camber.

While it looks like camber would result in inner edge tire wear it does not. For reasons I can only barely guess at. One being that as the car moves down the road the tires move from the natural give in the suspension bushings and obtain a full contact with the road and provided the toe is ok there is no scrubbing of the tires.

Think about it. No way could an automaker come up with a suspension system that resulted in partial contact of the tire's tread with the road surface. The safety agencies would have a field day with this.

To develop a baseline I recommend an alignment be done when 4 new tires are installed, unless the tire wear indicates the alignment is out when just replacing (most often for me) the rear tires.

Then just keep an eye on the tires. If you see uneven wear, inner or outer edges, front or back tires or if you can feel when you run the palm of your hand over the tread faces then it is time to have the alignment done again.

My experience is unless one is rough with the car: bumping curbs with the front (or rear) tires when parking in a parking space, or cutting corners into or out of driveways that have the rear (or even the front) tires running up and over or down a curb, the alignment will remain good for lots of miles.

I'm very careful to avoid doing any of the above and even after over 250K miles the original wheels of my Boxster have zero curb rash. (I did brush a curb with the side of a rear tire once and while the sidewall of the tire was scuffed, but not severely, the wheel was not harmed. The toe on that side was out though when I had the car aligned the next time I replaced the tires.)

However, I was not so careful with my Turbo one evening when I pulled just a bit too far into a parking space at a motel. Due to extreme tiredness I misjudged how far I could pull in and the front tires hit the low curb, the curb being low enough the front air dam didn't make contact. The car felt ok on the road the next day but on the way back home the car developed a howl that had me thinking wheel bearings. A stop at OKC Porsche and the tech there id'd the source of the noise (after a test drive of the car) as coming from the front tires. He said the alignment (toe) was out. And one could feel the feathering of the tire tread when running his hand over the tread. I wanted the alignment done but was told that the misalignment was not that bad and to just have wait until the tires were replaced. Also, I was told that to get the best alignment results the alignment is best done when new tires are fitted.

Against my better judgement I headed home and made it home ok. Once home after a bit though I got tired of the noise and had the alignment done when I had the oil changed, even though the tires were not replaced. The tech did caution me that the results might not be as good as in the past, but I was willing to risk this.

The before numbers of the alignment printout showed the front toe to be out. After the alignment the tires eventually wore down a bit and became quieter.

Get some good tires on your car. Worn tires can affect the quality of the alignment. Be sure to remove all dead weight from the car. Have the spare tire/tool kit in the trunk and secure in their proper places. Fill up the gas tank. Get the car properly aligned at a place that really knows how to align these cars. It is not just a set the front toe and forget car to align. You should get before and after numbers on a printout. The before numbers will show you what settings were out. The after numbers can provide some early warning something may be going amiss in the suspension/steering department.

Sincerely,

MarcW.

that the guy who did my alignment set it up with worn tires on it. And, when I swapped on some new wheels and tires, I had excellent tire wear where before the alignment the wear was uneven. Since he set many cars up for racing and did nothing but Porsches and had an excellent reputation in the area P-car community, I figured he knew what he was doing. He was aligning the wheels, not the tires.

The alignment is of the wheels but the wheel's attitude depends upon the condition of the tire. If the tires are worn bad enough this can affect the alignment. Then when new tires are installed the alignment is off.

In the case of the Turbo the front (and rear) tires were not that worn. Besides, to eliminate the irritating howl that really affected my enjoyment of the road I was willing to the chance the alignment might not have been as good as it would have been with new tires. From the results -- the car has become quiet again and tire wear seems even --I think the alignment was ok.

But it is best if one can have the alignment done with new tires, and as I've covered before with the car prepped properly: spare/tool kit in place, secure; car empty of dead weight; full fuel tank.

If the alignment is off though and the existing tires are at risk of accelerated wear, I'd still go ahead with an alignment. It really bothers me not getting 20K or more miles from a set of rear tires from my Porsches. It really irks me to have to replace prematurely worn out rear tires in one case with under 9K miles due to a bad alignment. Also, since I drive a lot keeping tire noise down and having a car that steers/handles well on the road, with no annoying pulling or other symptoms of misalignment is worth it to me. Bad enough on a 30 mile work commute. (I had the new Cayman S in just a few days after I bought it for an alignment and it was just used to commute to/from work in this span of time. In fact now that I think of it I had the Turbo in for an alignment just a few days after I bought it. In both cases the cars felt a bit off and after the alignment were just perfect.) Living with a car in need of an alignment in covering 4K to 5K miles in a week? No thanks.

Sincerely,

MarcW.

sit with camber influenced in part by the tire (although the suspension will attempt to hold it in place, bushings will deflect).

So the alignment will then zero out the error - by placing a counter error on the camber setting.

When the new tires go on, two changes occur. The camber is off, and as a result, the tie-rod effective length is off, so the toe moves (can be either way).

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

Will find a local shop with a Hunter and get the alignment done.

Thanks for the input!

When I had the the stock alignment setup changed for one that was more track oriented , the dealer tech was able to get -1.0 in front and -2.0 in the rear with zero toe in front and just a bit of toe in on the rear.

The tires have worn well (GY F1 Asym) with about 20K on the fronts (7/32 tread) and the 8/32 in the rear (second set with 10K on them). Before I replaced the rears, they had 5/32 on them with just a 1/32 difference in- depth outside to inside--more wear on the inside.

...accelerate wear. But negative camber at neutral position will increase inner edge wear. The only debatable point is "how much".

So if your toe is out, fix it - agreed.

Over the long haul most people seem to report 15-20k from the rears and 30+k from the fronts, with normal road driving (let's leave track rats out of this). This jives with my presumption. Of course there is also 55% of the weight in the rear, but to counter that, the tires have a 25% wider contact area, and due to tire design, bigger tires DO have a bigger patch. They don't act as ideal pneumatic devices.

Further evidence: my road-driven original tires wore more on the inside than out, and the fronts wore twice as fast (roughly) as the rears. but once i went to the track, all this changed. Rears wear evenly (albeit quickly) and fronts wear instantly, and at the outside edge. Hence my new alignment will have as much front negative camber as can be coaxed out of manufacturing tolerances, and keeping the toe near the center of spec.

Now, will most of the tire be in touch with the road at rest? Yes. Will it be evenly loaded? No. Will the loading tend toward the inner edge more as it moves through its arc? Yes. You cant avoid this -- draw it out if you like. I don't know what safety agencies would say if they realized this, which i doubt they do, but it IS true and they apparently say nothing. QED.

So -- your comment adds a lot to explaining which parameters matter most. But i don't think your experience, of the alignment guy's comment, counter the fact that a tire tilted out will wear its inner edge more than one that is vertical at neutral travel.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

The stock suspension set up up has lots of negative camber in the rear to induce understeer, not what you want, but its hard to dial it out with a a stock suspension. Negative camber will wear the insides of the rears very quickly. The solution is to run directional tires and rotate the rears by dismounting them and swapping them side to side. You can double the rears life by doing this. If you have assymetrics, you can' rotate them.

So I got to wondering about the car/tire ratios....

Veyron price (used) $1,150,000 Tires $26,000 => 2%

Boxster price $65,000 Tires $1100 => 1.6% (but you could get below 1%)

Even so the Veyron tires are perhaps more affordable because, if you can afford that car, $26k is a rounding error.