I knew you'd come up with a good reply. Are you saying because of the unequal length multi-link system the NSX can maintain its intended contact patch better than others with some spacing changes?
I am simply stating that different suspension designs will react differently to a significant change in vehicle track width. I don't know enough at this point to make that specific point you are making. Case by case here... I have only read-up on independent designs.
Here is a good primer with pretty pics on other types of common suspension designs:
http://www.carbibles.com/suspension_bible.html
It sounds like you are giving this mod an OK overall within reasonable limits.
Yes. I can tell you that in the right context, the wider track mod is faster. Minimal on a road car. Maybe not as cool as a JDM widget.. but basic weight balancing/transfer control mods are awesome for track.
If you were a qualified engineer and re-designing the entire suspension for full race, track width would be just one parameter taken into account. Most of us are working within the constraints of the stock suspension, so just be mindful of what changes you are making. I suspect most will be making bigger far more significant changes in tandem (e.g. moving to more tire, race suspension, etc...) and thus I wouldn't dwell on it. It is the cumulative results that count.
The thing to remember is suspension is like anything else (brakes/engine/etc...).
Cars are like big dials. One side reads Kia Spectra then in the middle is Porsche 987 starbucks sippin' Boxster and on the other side it reads Porsche 917 race car. Any one small change unto itself is probably not going to make or break drive-ability or performance. However, when you start adding everything together or making drastic changes then you hit this point whereas you are like... hmm... I see. I can't have both.
In general, unless you are a track enthusiast, increasing the track width or running ubber large tires is not a significantly beneficial modification dollar for dollar IMHO and will create more problems then it is worth. Most people buy spacers to fill in fender gaps or something for aesthetics. You would likely do better by focusing on the basics like suspension/tire setup. Buy yourself some more seat time at the next track day.
The reality is wide-body / extreme track type modifications are designed to increase lateral mechanical grip, not make the car 'street fast' in a straight line by any measure. In fact, they can slow it down. Why do you think stream liners on the salt flats are so long and narrow? High speed stability.
My data point is 1510mm front /1530mm rear is NSX 02' track width, and will go so far as to disclose that in current trim my wide body is at 1596mm front and 1630mm rear at the spindle at 35psi. Not that it is all that comparable.. but for reference a Super GT 500 car with 13" wheels is like 1690mm/1685mm
What about the wheel bearing thing? I have heard that too.
Don't worry about it. All I can say is I've never replaced mine yet and I have a pretty extreme difference. I have on other vehicles with larger wheels/tires but the NSX so far has been ok. If you are at the point as a driver whereas you are doing heavy modifications and track width changes are a primary talking point, I would hope that the possibility of replacing a wheel bearing isn't high on the concern list. They aren't all that expensive. Couple hundred bucks. I will likely do mine as preventative.
Last, can you think of any other drawback besides the turning radius issue?
From the best that my butt can tell you the difference in steering is likely the most notable. Clearance to the fender and under full lock-to-lock can also be impacted depending on ride height and other factors. Case by case.
In theory... well, to the very best of my knowledge, the other problem is that once you make such changes- the center of the tire contact patch is not necessarily at the center of the tire anymore. It depends on rim offset. Thus, adding a +15mm spacer is not necessarily equivalent to swapping to a wheel with 15mm lower offset... the final vector forces are further a function of the back-spacing of the specific wheel design for the rim width too.
The spindle/upright is the most important piece, and once you change it and the suspension arc in relation to the instant center it can cause a bump camber change.
Source: Chapter 6 Race Car Engineering:
http://www.rowleyrace.com/PDF/Chapter_6_Excerpt.pdf
Do you agree that the offset increase/decrease should be maintained front and rear on a stock suspension?
In principle, yes. Their are better ways of adjusting that don't have as drastic negative consequences.
I know you can start playing once you start changing other things that change under/over steer.
The basic idea is you get yourself in the right ball park with race car design, then you tweak (sway bars, pressures, aero, etc...) from there.
I wouldn't think the spacer will be any different than, say, wider rims or tires.
