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alignment specs

11 February 2000
Half Moon Bay, CA, USA
I just put a set of SP9000's on my '91 that has Dali sway bars and no other suspension mods. The car doesn't seem as "hooked up" when driving in a straight line. The car seems to drift a bit on the highway. Turn-in is slow and sloppy but once the car takes a set in a corner it grabs like it's on velcro.
The FAQ seems to suggest an alignment change to rectify the problem. Has anyone else had similar problems with these tires? Will an alignment give me more straight-line stability?
I believe front "Toe in" increases straightline stability. If I recall right the front alignment settings on the NSX are Toe OUT, which increases its dartiness and gives you a quicker response when turning. The rear's are set to Toe in, which helps keep your rear end planted and combat that lovely snap oversteer which is so common to mid and rear engined cars.
I changed the settings on my '99 a couple of months ago to get more mileage out of my tires - I replaced the first set at 7.5K miles. Toe-out was 5.3 mm in front and toe-in 4 mm in back. My new specs are 1 mm toe-out in front and 2 mm toe-in in back - no changes in camber and caster.

The car feels the same with the exception of some loss in straight line stability, particularly at speeds over 120 mph. My guess would be that increasing the toe would bring you more straight line stability. Again, just a guess.
RM Racing Alignment Specs for Street/Track.

Camber -0.4 deg.
Caster 7.5 to 8.0 deg.
Toe +.04 in.
Cross Camber & Caster + - .2 deg.

Camber - 1.5 deg.
Toe 0.0 in.
I recently installed RE730s on my 91. Stock tire sizes on stock rims. The alignment was to 93 specs except Front Toe was set to 0.0 to decrease tire wear. Custom Alignment in Mountain View, Ca 650/961-5311 did the alignment for about $150. They are familiar with the NSX, have state of the art equipment, and their lot is always filled with Porsches for street and track. I was concerned immediately after the work, since the car now seemed to ride more like a Lexus than the NSX that I was used to. After reviewing the pre vs. post alignment settings with that was provided in the work report, it was clear that the difference was in the tires and not the alignment. After discussing this with Custom Alignment I believe that this can be attributed to simply having more tread on the tire (tread squish). The handling improvement, of course, is gradual as the tire wears, but when the old 'slicks' are replaced with new tires the handling will feel degraded.

In summary, I have no experience with the SP9000s and don't know jack about the effects of alignment settings, but thought I would relate my experience. If you would like to talk to an experienced individual about Street/Track alignment setups here in the Bay area, give Custom Alignment a call. They will set it up the way you request, and guarantee their work. No I am not affiliated with them, I just greatly appreciate outstanding customer service.
Since we are talking about alignments... I must as well throw this in.

If you ever get your car aligned and they cannot get the castor in spec (I dont remember, but it was something large like 7 or 8 deg), make them dial BOTH sides to the SAME value.

If the tech puts one side to spec but leaves the other out of spec, then your car will have a tendency to pull towards one side.

I made this mistake once and the results were very disappointing. I had just spent $140 to get a car perfectly aligned -- to drive slight to the right. GREAT...

BTW, most cars have around 3-5 deg castor, so the loss of 1-2 degrees wont be *that* detrimental. It just means that your steering wheel wont return to center with as much force after a turn. Thats less annoying than a car that drifts left/right.

Motorcars Acura in Cleveland had to do mine twice. It pulled to one side after the alignment. Since they neglected to give me a printout, I am unsure of the exact settings.

//If the tech puts one side to spec but leaves the other out of spec, then your car will have a tendency to pull towards one side.//

First I would like to ask you if the chops stands for lamb or pork?

If it stands for lamb I am sure that your problem is a common problem that stems around your taste for lamb.

If it stands for pork that you should forget about it and go back to our previous set-up.

Hope this helps in solving your problem.

If I can be of further assistance please do nto hesitate to ask.
Old thread. But as long as someone already revived it, I noticed that a key point seems to have been left out of the responses to the original question. Although it is covered often in these forums, no harm including it here for newbies to find.

As already mentioned, toe out helps a car turn in quicker and better, whereas toe in improves straight line stability. The whole point of the made-to-order OEM tires was to accomplish the seeming impossible, achieve both. They do this by setting the geometric alignment to toe out for turning, then design the tire carcass with built in scrub towards the inside and dial the caster way up to make up the rest in straight line stability. The rear suspension and tires are just the opposite, toe in and scrub out. This constant battle between toe and scrub is the biggest reason why OEM tires wear faster than others for a given alignment.

So, when you go to anything other than the OEM tires you lose half of this wonderful equation so carefully crafted by Honda engineers. Toe out on the front will always feel vague even with great tires, which is why most street cars have toe in.

Does that mean your car won’t corner as fast/hard? Not necessarily. I suspect that the physical alignment largely dictates the limits of performance, and the scrub makes it feel crisp and stable. However, your particular choice of tire may significantly impact performance. The SP9000 is probably not up with today’s top supertires such as the SO3 or T1S.

[This message has been edited by sjs (edited 09 April 2002).]
Thanks SJS, since my rears are already toasted I'm looking at a set of SO3s as a replacement and just tossing the fronts even though they have very little noticeable wear.

SO3 opinions anyone?

[This message has been edited by ChopsJazz (edited 11 April 2002).]
I love mine so far. (SO-3's that is) About 1k on them and a very noticeable improvement over the cheaper tires that were on my car when I purchased it. I considered those my learning tires and now I'm running high quality tires. Rain was a big consideration in my choice since I'm in Fl. The SO-3's are designed with this in mind. I don't want to save on tires to spend on a wrecker