What Aftermarket Wheels Will Fit?
Factory Offsets
The NSX’s front offset is 55mm and the rear is 60mm irrespective of 15/16 or 16/17 wheel sizes. The NSX’s front wheels fit the 97 preludes (and 3.2 TL’s) in either 15 or 16 sizes. The 16 or 17 rears will fit the RL and the Legend – hence – lock your wheels!
[BP] Definition of offset: Offset is the distance between the mounting surface of the wheel (which contacts the hub) and the center line of the wheel. All wheels have offset, even if it is zero. To determine the center line of the wheel, you find the exact middle of the wheel by physically measuring the actual mounting surface of the tire (usually bead to bead).
Just because a wheel may say it’s 8″ wide, doesn’t always mean that is the center line is 4″. But it usually is, so when trying to figure out if a rim will fit a car, I use this as a starting place. Positive offset would mean the “mounting surface” of the wheel is more towards the street side of the wheel. Negative offset would mean the “mounting surface” of the wheel is more towards the hub side of the car.
[FG] Also keep in mind that aside from the fitting issues (rubbing or sticking out too much), the steering geometry is also affected when you change the offset. For the front wheels, the steering axis – the point at which the wheel steers around was kept in mind what the Honda engineers determined the offset for the wheels. Though the rears do not have this problem, they however do affect the overall steering geometry.
There is a lot that can be said about suspension and steering geometry so I will try to keep it simple. When a given engineer (or team of engineers) designs the suspension and steering for a car, they specifically determine the placement of the contact patch of the tires relative to the rest of the suspension components, the car’s track, center of gravity, alignment etc etc. In the case of the NSX, the front wheels have an offset of 55mm and the rears 60mm. (Also note that when they went from the 15×6.5 and 16×8 wheels in 91-93 to the 16×7 and 17×8.5 wheels in 94-current) As a refresher, the offset is the distance from the centerline of the wheel to the mounting surface of the hub.
Therefore, if you go with a wheel that is 0.5″ (12.5mm) wider in the front, you would ideally still want the center of the wheel to be the same 55mm from mounting surface. Hence the wheel will be 6.25mm further out on the outside lip than before as well as 6.25mm further in on the inside lip. This is what I would determine to be the “correct” offset.
HOWEVER, other things come into play like adequate internal wheel clearance of the brake calipers as well as external clearance of the fender lip and the suspension components. This is very much determined by the design and shape of the wheel as well as it’s width. Based on my measurements, staying with a 16/17 combo, you could not go another 1/2″ wider without decreasing the wheel offset. With a 17/18 combo, it may be possible (though this would have to be a very well designed wheel to accomodate the NSX brake calipers and the face of the wheel may not look to good because it would likely be even more convex than the OEM wheels are.
What it boils down to is that if you go with a wider wheel, you are normally compromising something. I am not saying this is bad because it is possible to change the suspension alignment settings etc to get a different optimum setting with different goals than the factory engineers were thinking of. Or, if you needed an upgraded brake package, then you may not have a choice anyway but in that case you are getting better stopping (actually less brake fade). Or maybe the wider wheel gives your better grip in the turns. On the other hand, a wider or larger wheel is normally heavier, hence affecting acceleration and taking back some of the braking. Also, the spring and shock rates may no longer be optimal for the difference in unspring weight.(one reason why I prefer the feel of the suspension and steering in the pre-94 coupes).
What Offsets Have Been Tried?
[DNG] I have 7.5″ width in front and running 45mm I have 9.5″ width in rear and also running 45mm. The front wheels could be moved more outwards another 0.25″. The rear wheels are perfect IMO.
[HS] My MIM/Speedline five-spoke modular wheels (8×16 front, 9×17 rear) have the following offsets – F-40, R-48.
I believe ideal for 8-inch fronts would be 44, ideal for 10-inch rears would be 47. I have 225/45/16 & 265/40/17 PZeros with no problems (stock height).
[TS] My new wheels arrived from Japan last week so I went up this past Saturday to have them installed at Autohaus. The front 17×8 and 37 offset did not fit despite the importer’s assurance. (they rubbed against the caliper).The rear 18×10 with 45 offset were fine.
I have 17″ x 8″ with an offset of 40 at the front, and 18″ x 10″ with a 45 offset at the rear. Both fit perfectly without any rubbing. And the tire is right at the edge of the fender without it sticking out.
Offset and Caliper Clearance
Let’s take a wheel which has the straight spokes which do not clear the caliper. It would look like this (sorry for my poor art):
(top)
-___________-
|
***
|
(car side) | (spoke side)
|
|
|
_-----------_
(bottom)
This is (a poor attempt at) a cutaway view of the wheel from the side. The | in the middle is the hub mounting surface of the wheel, the *** is the caliper width, which is shown intersecting the vertical plane created by the spokes (thus the wheel doesn’t clear the caliper and does not fit).
Decreasing positive offset means that the entire center part of the wheel (spokes, bolt area, and hub mounting section) is moved towards the centerline of the wheel as one piece. Meaning that the distance from the hub mounting surface to the spokes remains constant. The calipers are fixed to the car, so their width in relation to the hub and hub mounting surface is also constant. Thus you would have:
(top)
-___________-
|
***
|
(car side) | (spoke side)
|
|
|
_-----------_
(bottom)
Since the spokes are moving in with the hub mounting surface, reducing the offset does not increase horizontal caliper clearance.
[AWN] Positive offset moves the hub-mounting surface toward the OUTSIDE of the wheel; negative offset moves it toward the car. None of this is important, though, because the offset is measured between the wheel’s hub-mounting surface and the centerline of the wheel; it has NO bearing on the distance between the hub-mounting surface and the spokes.
The only thing you’re interested in — for the purpose of deciding whether a given wheel will clear a given caliper — is the distance between the hub mounting surface and the spokes. That’s not “offset” and it’s not “backspacing”; it’s usually called “caliper height”, “caliper clearance”, or “caliper relief”. “Backspacing” is the measure of the distance between the hub-mounting surface and the plane of the inside edge of the wheel. In other words, it’s just like offset except that you measure all the way to the inner side (the side closest to the car) of the wheel rather than just to the centerline.
To determine the necessary caliper height, take a wheel off the car and lay it aside, then look at the hub on the car. Measure how far the caliper “sticks out” from the surface to which the wheel will mount; that’s how much clearance you need between the wheel’s mounting surface and the wheel’s spokes.
Are There Disadvantages To Bigger Wheels?
I am looking at going with 17/18 TecnoMagnesio rims with Michelin MXX3 235/40 on the front and 285/35 on the back on my 91 NSX. This is the rim/tire setup recommended by CompTech. Has anyone tried this — what are your impressions?
[MJ] My initial impression is that it is a **very** expensive setup. Call around on the Techno wheels, I’ve seen them elsewhere for 2/3 rds the CTECH price, and those tires are pretty HUGE and HEAVY. Do you have the HP to push them ??
The fronts are 3.3 % larger than the stock tires.
The rears are 4.6% larger than the stock tires.
You will need to buy the NSX/R 4.235 Ring and Pinion (4.5% “lower” ratio than stock) just to maintain your OEM acceleration and that is not accounting for the increased mass of that size tire. Perhaps you can get them to throw in the 4.55 rear end and the Supercharger with the tires and wheels ! ‘;-)
rear suggestions:
245/35/18 or 285/30/18 is just 0.1% larger than stock, so you will not feel the acceleration drag.
front:
215/40/17 is 0.7% larger than stock
225/35/17 is -1.8% smaller than stock
235/35/17 is -0.6% smaller than stock
anyhow, LOOK before you leap.
[KS] Two problems: performance and cost.
Mark noted the performance problems resulting from using tires with a larger diameter than stock. Another way of looking at that is to consider that using larger-diameter tires is equivalent to using LONGER gears (or lower-ratio R&P) that will raise your shift points – and we’ve all heard about how the SHORTER gears (and higher-ratio R&P) have the advantage of lowering shift points.
Regarding price, Mark noted that this is a very expensive setup and suggested calling around for prices on the Techno wheels. Consider the prices on the tires as well; for example (using current Tire Rack prices):
Stock rear tire (Yokohama A-022H): $192
285/35-18 Michelin MXX3: $319
285/30-18 Michelin MXX3: $329
Stock front tire (Yokohama A-022H): $156
235/40-17 Michelin MXX3: $254
(Their ad doesn’t list a price for the other sizes Mark recommended, the 245/35-18, 215/40-17, 225/35-17, or 235/35-17, so I suspect the MXX3 doesn’t come in these sizes.)
Remember, you will be paying that $470 difference not just once, but every time you buy a set of tires.
Will Different Sizes Affect TCS?
[A/H] One way to test wheel/tire combo for TCS compatibility once it’s on the car is this: pick a level cement area, put a small (2mm) piece of grease in the rain groove of both front tires, then push the car backwards for 2 tire revolutions, then measure (to the mm) the distance between the grease spots for both front tires. If the fronts are not the same size the computer thinks the car is in a turn because the sensors show them turning at different rates.
Then, wipe the floor and do it again for the rears and push the car forward. Measure the distance between the grease spots and then divide rear/front -1. The fronts should be about 5 to 7% smaller.
You can also get this information by calling the tire mfg. and get the “revolutions per mile” and divide.
You can check diameter for any tire size at: http://www.powerdog.com/tiresize.cgi
See how different wheels will look on a car at Claus Ettensberger’s “Wheel Machhine”: http://www.cecwheels.com/
[KS] The RATIO between front and rear should be within 5 percent of the STOCK RATIO. Based on the ’91-93 OEM
sizes, the ratio should be between 2.7 percent and 12.7 percent. Based on the ’94-98 sizes, it should be between -0.3 percent and 9.7 percent.
However, as a general rule, your best bet in choosing tire sizes is to not only shoot for the stock ratio between front and rear, but also the stock outside tire diameters. Otherwise you will be changing what some people call the “effective gearing” of the car, i.e. the number of engine revs per mile traveled. With bigger wheels, if you’re not careful, you are likely to wind up getting tires that are a larger diameter than stock; think of this as equivalent to getting LONGER gears put in your car. Not very desirable for performance.
How Will My Speedometer Be Affected?
[KS] First, you’ll need the outer diameter of the two tire sizes (original and actual). There are numerous websites where you can enter the tire size and calculate the outer diameter of the tire (for example, http://www.4lo.com/gearcalc.html ) – or it’s a fairly simple calculation anyway (outer diameter equals wheel diameter plus twice the shoulder height; shoulder
height is tread width times aspect ratio; convert between mm and inches as necessary).
Then adjust your speedometer by multiplying by the ratio between the original and actual outer diameters.
What About Hub Rings / Adapters / Spacers?
[BP] Hub rings were designed to allow a wheel to be “hub centric” which means that when you mount the wheel to the hub the bolts align properly. This is common in today’s wheels because it allows wheel manufactures to make one wheel with the same offset and bolt pattern for several cars.
The NSX bolt pattern and offset is used in some Honda, Acura, Mitsu, and Toyota applications, but the hub ring makes the wheel set properly on the hub. This is not a bad thing. It does not hurt the performance of the wheel. Be sure to read the instructions before pressing the ring into the wheel because if you do it backwards you’ll have a hard time getting it out again and it won’t sit right on the hub.
[SR] My first NSX (’91) had spacers installed on the rear wheels to allow wheels with the wrong offset to be installed. After I had owned the car for a few months I heard a rattle comming from my right rear wheel. When I opened up the lug cover I found a lug nut with a piece of the stud rolling around in there (broken off!!) the rest of the lug nuts, I discovered required only 3 turns to be torqued!!! The spacers I had were just a 10mm washer like piece of metal with holes drilled to
match the lug pattern. This arrangement eliminated the “hub centric” design of the wheel and put the lug studs in a shear loading condition (they are only designed for tension). If you do use spacers make sure they are designed to attach to the hub and transfer the “hub centric” out to the wheel and not just act like a washer. Also make sure that you will have enough grip length on your lug nuts (at least filled with stud). Rule of thumb is 6 full turns at least.
[KP] Hub rings are REQUIRED to make your new, multi-car designed rims, hub-centric. Aftermarket wheels are typically manufactured with centerbore diameters equal to the largest hub size of the car that the wheels are targetted for. The manufacturers then supplies the buyer with hub rings to make the rim hub-centric by matching the diameter of the wheel centerbore with the hub. Make sense?
This is done for a very simple reason. It makes swapping wheels on your car much faster since hub centric rims allow you that little lip to rest on while you gently rotate the rim to line up the lug nuts. (Crap! Am I thinking about my BMW which has lug bolts again? ) Hmmm, OK, maybe this isn’t the right answer. Alan? Help!
OK, the real reason the you want hub-centric rims is for those occasions when you buy tires at one of those local discount tire stores staffed by a bunch of high school kids. You see, the moron that mounts your new A022’s has no idea what that damn bright red rotation sticker is as he’s convinced the tire will really rotate both ways. However, the other moron who’s just dialed the impact wrench in to 400 lb-ft, might actually have seen a corvette or two (who hasn’t) and might notice the little rotation direction moldings. Well, hub-centric rims will prevent him from mounting the rims backwards to avoid all the trouble of removing and re-orienting the tire. Makes sense, huh? See, there’s a logical explanation for everything.
OK, so if you don’t buy that one either, I’ve got one more potential answer. Hub centric rims provide some assistance in high tolerance centering of the wheel… a task normally left to that precise angle on the lug nuts. But… the real reason is so that shear (is that the way you spell it when you’re not talking about sheep?) forces are transmitted directly to the hub and the total load is not absorbed by the lug nuts. Imagine the energy absorbed by your tire, wheel, (and back teeth) when you inadvertently slam into a giant pot hole. In these conditions as well as high loads incurred by high performance driving, you’ll want to have somethin’ besides your nuts taking all the load. Uhh, your lug nuts that is.
Convinced? Put the correct rings in and you can avoid all the problems listed above.
[BC – 99/3/29] It’s not a good idea to put spacers. It adds extra stress to the hub/suspension/axle, and unless you carefully tune the suspension, you might screw up the handling.
[AVE – 2000/10/31] If you know the exact diameters, specialty wheel shops have bins of hubcentric rings. They are generic to fit different wheels. Just like the lug nut bolt pattern on the NSX is 114.3mm, other car manufacturers share this same geometry.
Dazz Motorsports in LA informs me that all Racing Hart wheels are bored to 73mm. The front hub on the NSX is 70mm and the rear is 64mm. I mic’ed the rings last night, and they are right on.
Some wheel manufacturers (BBS) have proprietary rings and some wheel manufacturers’ rings are generic.
Spare Tires
OEM Spare Tire with OEM Wheels
Using the factory spare tire may cause TCS to get upset. In this case, simply press the button on the dashboard to disable TCS.
Also be sure to note that the ’97+ cars have a different spare tire. It’s yellow instead of the orange color on the ’91-’96 spares. The new spare is larger to accomodate the slightly larger brakes. You can’t use the older spares with the ’97+ brake setup.
OEM Spare Tire with Aftermarket Wheels
[KS] There are two considerations regarding which spare you can use: outside diameter of the tire (whether you can drive on it) and inside clearance on the wheel (whether it fits over the calipers).
As long as you still have the stock calipers and rotors on a ’91-96 NSX, you can just use the OEM spare (even the 15/16 spare) with no problems. There’s no need to upgrade to the ’94+ spare, since the outer diameter of the 16/17 tires is very similar to that of the 15/16 tires. And even if you have larger diameter tires on those 17/18 wheels, I would think that you can still use the smaller OEM spare to replace the flat tire. Even though the diameter will be smaller than the other three tires, it will get you the few miles to a place where you can get the new tire. Remember, any use of the spare is going to be limited in miles and speed anyway; you’re not going to drive like you’re on the track with a donut on the wheel. So you won’t be worrying too much about the TCS working, etc.
However, one problem you MAY have is where to put the flat tire to take it to be fixed; if you have a passenger, you may have a choice between leaving your flat at the side of the road or leaving your passenger. You’re sure you still want to get those big 17/18 wheels, now, right? 🙂
If you have a ’97 or later NSX, I would think you can only use the OEM spare for ’97 or later, since the calipers and rotors are larger than on the earlier years. If you have the Comptech/Brembo brake package, your ONLY option for a spare will be a can of Fix-o-Flat. Brand doesn’t matter since I would think you wouldn’t want to repair a tire that’s full of that gunk.
What Types Of Wheels Are There?
Forged Aluminum wheels are strong and light, but usually more expensive. Cast Aluminum, which most aftermarket wheels are, tend to be heavier. Most “lightweight” cast wheels are in 20-25# range
Micellaneous Tips
[SS] For those of you keeping up on wheels, or just want to see another NSX on the net, check out http://www.hrewheels.com/Showroom/
[MCA] My dealer suggests these 2 fitments, and they do a lot of race/track prep cars: Per John Vasos (AoB):
“Popular” fitment: Front – 215/40R17 on 17×7.5, Rear – R 265/35R18 on 18×8.5. I used these. Front:Rear ratio 6.4%
“Bigger” fitment: Front – 235/40R17 on 17×8 (modified wheel well), Rear 285/35R18 on 18×10.
225/40-17 F are probably as wide as you want to go withouto rubbing –> rare size (SO2 only?)
235/40-17 F will fit, but you will rub on full-lock turns (pound inner wheel well)
Lastly, SO2 Pole Position seems to offer better performance (particularly when worn) and longer wear than the SO2, for the same $$$ (I suspect that the SO2 may have a slight edge in dry)
Some combos might be a tight squeeze with H&R springs, but should work with Eibachs.
BTW — you should compare the TCS ratios against the OEM settings (for 15/16 the ratio is 7.7%, you want to be within +/- 5% of that, ie 2.7 to 12.7). Also, watch for speedo error (in my case, the rears are 0.4″ taller, resulting in a correction factor of approx 1.0176 (811/797).
What Do Various Wheels Weigh?
| Wheel | Tires | Weight | Overall Diameter |
|---|---|---|---|
| Stock 15″x7″ Front | Yoko A022H (stock) | 32 lbs. | 23″ |
| Stock 16″x8″ Rear | Yoko A022H (stock) | 44 lbs. | 24.5″ |
| OZ Mito Modular 3-pc 17″x8″ | Dunlop SP-8000 215/40-17 | 44 lbs. | 24″ |
| OZ Mito Modular 3-pc 18″x10″ | Dunlop SP-8000 275-35-18 | 53 lbs. | 25.5″ |
| Fittipaldi Interlagos 16″x7.5″ | Dunlop SP-8000 225/45ZR16 | 43 lbs. | |
| Fittipaldi Interlagos 17″x8.5″ | Dunlop SP-8000 245/40ZR17 | 53 lbs. |
[HS] Low-profile tires on 17/18 wheel combinations need to be stronger than the Forgelines… Forgelines on THREE cars were damaged at NSXpo. Enough said.
[MJ] Stats for the Technomagnesio wheels sold by Dali Racing/MotorMail:
16X7
about kg. 7.0
15.40 lbs.
17X8.5
about kg. 8.1
17.60 lbs.
17X8
kg 7.4
16.28 lbs.
18X10
kg 9.3
20.46 lbs.
As you can see, they are not too much heavier and will allow wider tires. Pricing on the 17/18 is $620/$735 plus shipping. Shipping to the USA per set of 4 is about $260.
How Do You Properly Assemble 3-Piece Wheels?
[HS] Here’s how I’ve done it… bear in mind that at least two people are required to do the job quickly — before anything dries.
- Clean and lay out all the nuts, bolts washers. On race cars I *NEVER* reuse old nuts or bolts.
- I use GE “RTV” silicon sealant on the “O” ring because it is not too viscous and doesn’t set up too fast.
- RTV up the “O” ring and install in in the wheel. I apply the stuff by pulling the “O” ring through my finger tips. Use as little RTV as possible, but make sure you get coverage — you don’t want the stuff oozing out between the hats. Use 6 or 8 old nuts and bolts to hold it in place snugly. Don’t use the lock-type nuts for this.
- Quickly start installing the proper nuts and bolts (run the nuts down all the way, but not tightened to torque yet) do it in a star pattern — like you would do with head bolts or wheel studs.
- Once all the fasterners are in place (and you’ve replaced the original 6 or 8 nuts with the proper bolts and lock nuts. Torque the nuts to their proper value. Got that: torque the NUTS, not the bolts. Use a six-point socket so you don’t round any flats. Three people help here: one to hold and turn the wheel, one to hold the socket wrench on the bolt, one to toque the nuts.
- Retorque all the nuts and bolts again, to make sure none were missed. Use that star pattern to pull everything down evenly.
No need to wait to install the tire — whether the RTV is dry or not makes no difference.
Oh yeah, as long as you have everything apart, use metal (not rubber) valve stems — and good, metal valve stem caps with new “O” rings in them.
What Causes Wheel Vibration?
[KJ] First, look and see the amount of weight that is being used to balance the tires. It shouldn’t be more than about two ounces, preferrably less. If one or more of your rims has a lot of weight, you may ask the tire shop to break the bead and rotate the tire on the rim 180 degrees. Notice if the weights follow the tire.
Second, you can check the runout on a gross scale by yourself. Jack up the car and get a block of wood, milk crate, etc. and place a straight edge on it and get it right up next to the rim. Now, spin the tire and notice if there’s any noticeable runout. I’ve done this with the straight edge about 1/32 from the wheel, and you can just stare down this gap and see if the wheel is wobbling.