I recently went back to the stock wheel and tire setup (love it btw!), but feel like the rears look "whimpy" for lack of better terms. I am going to apply spacers, but not sure what your thoughts are. Chris @ SOS recommends either the 25's all around, or 15 up front and 25 out back. Any suggestions. I would prefer to do 25's all around so that I can do all the labor in my garage, but I worry that the fronts will be out too far for my tastes. Any thoughts/opinions? Also, if you have pics I would love to see them as well. Thanks in advance.
Best,
Chuck
In my experience, most enthusiasts add spacers or use lower offset wheels on their otherwise stock vehicles simply for aesthetics, because they want the wheel to sit flush with the fender as opposed to inset. Typically the degree of spacing, often in the range of 5-15mm per side is negligible enough to be of little practical consequence, with the only real side effect being more debris thrown out onto the doors and quarters during daily driving.
If the vehicle is further lowered significantly, then another issue would be clearances, namely in the front. The first part of that discussion is the fender clearance along the upper range of motion travel. On track cars the wheels/tires are often tucked in with added negative camber on a stiffer spring rate, and this generally allows for a lower ride height during chassis setup. By regressing so significantly from the stock positive offset, on a mild alignment you may be more limited. An alternate explanation, positioning the top of the tire outwards so close to the fender lip; will sacrifice dialing out ride height in order to gain marginal track during chassis setup. Much depends on your tire profile, which on most daily drivers tends to be shorter side-walled narrower street tires with very mild alignments using stock fenders/liners. This all amounts to leaving little finaggle room. The second part is that I will also say that the farther you deviate the more tricky it becomes to realize issue-free lock to lock steering, as this can require experimentation being another wild card along with tire sizing.
If mild sounds like your direction, then depending on your existing offset and width you might go to 37 or so, not sure on your specific ride but 25mm sounds a little aggressive for stock. You might wish to make a notation of the width and offsets of members setup's you have come to prefer so you can get exactly what you want. If this is simply about aestetics... you can also preview various offsets by stacking on washers to the lugs in the garage. Spend a day playing around with a metric ruler to arrive at the exact offset you visually want. Then simply have a set of custom spacers made. However, be consistant along the wheel base. I can't agree on using staggered offsets (read below).
Do you race with spacers? You are changing the entire geometry of the suspension. Wider yes, when there is no suspension flex. But what happens during hard cornering movement? it seems that even the alignment would be off at that point. I don't think that moving wheels in and out 15-30mm and more on one end than the other has any sort of "negligible" affect. I am not trying to argue with you, I am just bringing up a point and asking.
On to performance theory.
The basic performance concept is that increasing track reduces lateral weight transfer when cornering, so can increase grip. However, the reality is that changes need to be more significant before you will really begin to notice this modification during cornering at or near the limit.
As an example, on an 02' NSX the front track is 1,511mm and the rear track is 1,542. The stock wheel offsets are 55 mm front, 56 mm rear. Once you start moving towards really aggressive widebody fitments like zero to +12 offset wheels then you can begin to start getting the track increased out to 88mm-100mm which is a relatively significant 3.5" plus increase. Go ridiculously too wide, other problems follow I noted in my other post. My point being, assuming your chassis is setup properly, my own experience is this this is more then range whereas you can begin to start feeling a seat-of-your-pants difference on the NSX.
It is very much like ride height in some respects, half the change half the result. For comparison, if you look at the numbers moving to a slightly lower offset wheel or slapping on a pair of 15mm spacers... these subtle changes would put you out about 1.18", so that is a change of about a half inch per corner on the center line. I tracked a whole year setup like that, including doing direct A-B comparisons between sessions among various spacer widths on my GTC's. It is just about as noticable as that NSX-R chassis bar. :wink:
The most important thing to know when you start playing with spacers or ordering wheels is that if you increase your track at one end of the car only, it changes the diagonal weight transfer characteristics, which would result in more understeer (rear track increased) or oversteer (front track increased).
Assuming you increase the front and rear track by similar amounts, the
basic effect on handling balance should be fairly minor BUT the effect on front end grip can be more significant, depending on Steering Axis Inclination, since you will be increasing the Steering Axis Offset. Steering Axis Offset has the effect of trying to lift one corner of the car when you turn the steering wheel, so if you increase the offset by fitting spacers, you will increase both the steering weight and the change in load on the tire (hence increasing understeer), for a given amount of wheel movement. You will often find that tendency to tramline is increased, too.
Mitigations- downside one, is that some warn that it can increase loads on bearings and suspension joints to an extent, and it would not be bad to generally expect reduced life on your stock hub components due to the added loads carried by the bearings. Race cars generally have better grade aftermarket hubs and bearings, but you know personally I've never seen a OEM hub failure myself that was not more easily attributed to age and normal wear and tear on an NSX. I've yet to have a problem with mine which are 9 years old. Using the proper offset wheel is cleaner, and in some instances it is possible to have the wheel center line distance to the chassis to actually differ depending on the fine details. Two is corner weight, but if you are using a quality forged aluminum spacer without integrated studs this can be measured in grams.
In any case, take any advice you so choose.. but as a matter of safety most definitely make sure you use a quality spacer that is both hub centric to your wheel and your hub. Relying on your wheel studs alone to carry loads is not the best idea. Not sure on all of the brands available, as our bores are different, the generic stuff is usually crap. I've used wheeladapter.com in the past they can fabricate you anything you want.
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