Wheel offset question for the NSX wheel wizards

[TCroly]

I have a '91 NSX with stock 15/16 wheels. I need new tires and I am considering a wheel change, since Tire Rack has some close-out SSR wheels at a good price. The only thing, is that not all wheel sizes and offsets are available. So I am trying to see if I can take advantage of what is available and want to make sure that I can make it work.

But before my specific size/fit question I have a general question as to the typical wheel widths and offset changes that seem to be the norm around here. Compared to the stock wheel width and offset, it appears that most people are selecting a width/offset that pushes their wheels out by about 25mm or 1 inch on each corner. I understand that this creates a more pleasing esthetic, but doesn't it also create some additional problems? Like rocks kicking up and impacting the sides of the car, or steering geometry changes, or extra stress on wheel bearings and suspension mounting components, or even a much greater tendency to brush a curb or two when parking? If this is true, then is there some logic to maintaining the stock offsets, given that I do not have plans to upgrade my brakes to larger calipers?

I will admit to being a bit of an NSX purist, and I believe that each decision that Honda made with the NSX has some sound reasoning behind it. So to that end I am considering a wheel upgrade that is very close to the choices that Honda made for the late year NSXs. I can get a set of 17X7 front wheels with a 50mm offset and 18X9 rear wheels with a 55mm offset. Isn't this acceptably close to the 2002 stock sizes of 17X7 with 55mm offset and 17X9 with 56mm offset? Can anyone confirm that this combination will fit without any issues?

Alternatively, If I did want to push the wheels out a bit, I can get a 17X8 with a 35mm, 40mm or 45mm offset and an 18X8.5 or 17X8.5 with a 34mm or 42mm offset. Is one of these options a better choice and if so why? These are the only sizes that are available on these close out wheels.

I use my car strictly as a daily driver, I would love to track it, but here on Maui, I don't have that choice. So I am looking for a nice updated look with minimal ride/handling compromises and I am willing to sacrifice extreme performance for balance and lower cost.

Tom

 

[arfnsx]

Hey Tom-

I am running 18/19 with a 38mm offset. This is a very nice set up with the perfect amount of spacing. Are you also planning on lowering it?

 

[Hapa88]

But before my specific size/fit question I have a general question as to the typical wheel widths and offset changes that seem to be the norm around here. Compared to the stock wheel width and offset, it appears that most people are selecting a width/offset that pushes their wheels out by about 25mm or 1 inch on each corner. I understand that this creates a more pleasing esthetic, but doesn't it also create some additional problems? Like rocks kicking up and impacting the sides of the car, or steering geometry changes, or extra stress on wheel bearings and suspension mounting components, or even a much greater tendency to brush a curb or two when parking?

Yes for all those questions. I've had issues with dirt getting on the side of the car because of the wheel flushness, but no rock chips yet.

If this is true, then is there some logic to maintaining the stock offsets, given that I do not have plans to upgrade my brakes to larger calipers?

Yes again, however it'll probably look funny, almost like a go-cart with the body too big. I'm not a fan of that look, but I imagine it would look something sorta like this:

I will admit to being a bit of an NSX purist, and I believe that each decision that Honda made with the NSX has some sound reasoning behind it.

If that's the case, keep it stock or OEM. Upgrade to the 7 spokes of the 1994-2001 or to the 2002+ wheels.

So to that end I am considering a wheel upgrade that is very close to the choices that Honda made for the late year NSXs. I can get a set of 17X7 front wheels with a 50mm offset and 18X9 rear wheels with a 55mm offset. Isn't this acceptably close to the 2002 stock sizes of 17X7 with 55mm offset and 17X9 with 56mm offset?

Yes the spacing and gaps would be very similar to the OEM wheels, but again, it'll probably look funny (just warning you).

Can anyone confirm that this combination will fit without any issues?

I don't know how much spacing there is behind the spokes of the wheels and whether or not they will clear the OEM brake calipers. You will probably have to contact Tire Rack to confirm that fitment.

Alternatively, If I did want to push the wheels out a bit, I can get a 17X8 with a 35mm, 40mm or 45mm offset and an 18X8.5 or 17X8.5 with a 34mm or 42mm offset. Is one of these options a better choice and if so why? These are the only sizes that are available on these close out wheels.

If it were me, I'd take the 17x8 +40mm for the front to get it pretty close to flush.
Unfortunately the 18x8.5 +34 will probably be further inward than the fronts resulting in a slightly awkward look (the +42 would be even worse). Also I'd try to go with at least a 9" width for the rear. . 8.5" should work, but that's a personal preference.

Remember that Flushness of a given wheel is related to both Width AND Offset. Not just offset. No offense, but saying "I have 18/19 wheels with +38 offset" isn't enough information to know what it'll look like, if the wheels will rub, or where the wheels will sit. If you can give the widths too, that would be very helpful.

For more info on offset, check this out:
http://1010tires.com/WheelOffsetCalculator.asp

I use my car strictly as a daily driver, I would love to track it, but here on Maui, I don't have that choice. So I am looking for a nice updated look with minimal ride/handling compromises and I am willing to sacrifice extreme performance for balance and lower cost.

Tom

I still think the updated OEM wheel option is the best bet given this criteria.

 

[TCroly]

Aloha Adrian,
Thank you for your thoughtful reply, but I am a bit confused about some of your points. First, the point that the car could end up looking like the under tired go cart? If I have computed correctly, the wheel widths and offsets that I have proposed should end up with the fronts 5 mm further out and the rear 1mm further out than the OEM 16/17 setup. And the stock set-up does not look under tired to me. so i am confused as to why the general consensus seems to ignore this as a viable set-up.

Second, It is my understanding (and I might be wrong) that the greater the positive offset value, the more the wheel is brought inward (given the same wheel width). Therefore a 17X8.5 wheel with a 34mm offset should be 8mm further out than a 17X8.5 wheel with a 42 offset. And either of these setups should have the wheel positioned an inch or more further out than the stock 16/17 setup with 60mm rear offset.

I totally agree that for my given criteria, an OEM set of '97 to '01 16/17s is probably my best choice. But I cannot find a perfect set of these wheels at anywhere near the same price that I can get the Tire Rack close-out SSR wheels. Since Tire Rack will mount and balance the tires for free and the shipping cost that Tire Rack offers to Hawaii is less than half the shipping cost for wheels alone from any private purchase. ($174 vs $400) At Tire Rack my delivered price for 4 wheels and tires is less than $1600! If I can get a perfect set of '97-'01 wheels with tires, delivered to Maui for that price, I am sold.

Tom

Yes for all those questions. I've had issues with dirt getting on the side of the car because of the wheel flushness, but no rock chips yet.

Yes again, however it'll probably look funny, almost like a go-cart with the body too big. I'm not a fan of that look, but I imagine it would look something sorta like this:

If that's the case, keep it stock or OEM. Upgrade to the 7 spokes of the 1994-2001 or to the 2002+ wheels.

Yes the spacing and gaps would be very similar to the OEM wheels, but again, it'll probably look funny (just warning you).

I don't know how much spacing there is behind the spokes of the wheels and whether or not they will clear the OEM brake calipers. You will probably have to contact Tire Rack to confirm that fitment.

If it were me, I'd take the 17x8 +40mm for the front to get it pretty close to flush.
Unfortunately the 18x8.5 +34 will probably be further inward than the fronts resulting in a slightly awkward look (the +42 would be even worse). Also I'd try to go with at least a 9" width for the rear. . 8.5" should work, but that's a personal preference.

Remember that Flushness of a given wheel is related to both Width AND Offset. Not just offset. No offense, but saying "I have 18/19 wheels with +38 offset" isn't enough information to know what it'll look like, if the wheels will rub, or where the wheels will sit. If you can give the widths too, that would be very helpful.

For more info on offset, check this out:
http://1010tires.com/WheelOffsetCalculator.asp

I still think the updated OEM wheel option is the best bet given this criteria.

 

[nsxtasy]

Hi Tom,

I think I can resolve the confusion.

Adrian said (correctly):

Remember that Flushness of a given wheel is related to both Width AND Offset. Not just offset. No offense, but saying "I have 18/19 wheels with +38 offset" isn't enough information to know what it'll look like, if the wheels will rub, or where the wheels will sit. If you can give the widths too, that would be very helpful.

Let's look at a diagram showing how positive offset (which our wheels have) is measured, and I think you'll see what Adrian is saying:

You can see from the left part of this diagram (labeled "positive offset") that the distance that the wheel sticks out from the mounting surface of the hub is half the width of the wheel, minus the amount of the offset. That's why the wheel width is a factor that needs to be taken into account in determining how far the wheels stick out. As you note, the lower the offset number, the more the wheels will stick out - as long as the wheel widths are the same. Otherwise, you have to do the math to determine where the outer face of the wheel is positioned, relative to a wheel of a different width and offset.

Incidentally, it's also worth noting that the center bores of the wheels are an area of concern. Hopefully the Tire Rack will provide hubcentric rings with any rings for which the center bore is not the stock values of 64 mm front and 70 mm rear.

Since Tire Rack will mount and balance the tires for free and the shipping cost that Tire Rack offers to Hawaii is less than half the shipping cost for wheels alone from any private purchase. ($174 vs $400)

I'm in the process of considering shipping a set of wheels to someone in the Pacific, and I can explain why that is. Most people are accustomed to shipping items within the States via UPS or FedEx, whose rates to our Pacific areas are very high. Check out shipping rates through the USPS and you'll find that it's much less expensive to ship them through the post office, either Priority Mail or Express Mail, both of which take only a few days. Just ask any private seller to send the wheels through the post office and you'll probably get lower rates similar to those of the Tire Rack.

 

[TCroly]

After looking at pictures of Adrian's car and other photos posted on NSXPrime, I think that I have decided that moving the wheels out about an inch may be a reasonable compromise. But I still would like to hear from others if they can state that moving their wheels out has created any unexpected, undesireable effects?

So to that end here is my question as clearly as I can state it:

I have a '91 NSX and I am proposing installing SSR GT7 rims of size 17X8 with a 40mm offset in the front and 17X8.5 with a 35mm offset in the rear. (Yes, I know most people would go with a 9" or 10" rear, but these are the only sizes available for the low close-out price)

The wheel offset calculator says that this will move my wheels further out by 34mm in the front and by 31mm in the rear compared to the OEM 15/16 setup. (Compared to the OEM 16/17 setup, this proposed setup would be 28mm further out in front and 25mm further out in rear.) In either case I do recognize that I am pushing the front wheels 3mm further out than the rears. Will this setup work, and look acceptable on my stock ride height car?

As for tire sizes, I am proposing 205/40/17 fronts and 245/40/17 rears. These sizes will maintain the OEM diameters of the 15/16 setup within 1% to prevent any TCS or speedometer errors and smallish tire size would avoid making my stock gearing longer! Also this particular wheel and tire size gives me 18 different tire choices from Tire Rack! Finally this should be a reasonably light weight tire/wheel package. Maybe a couple pounds more than the 15/16 with Yokes, but not nearly the 50 to 55 pound 18/19 setups that so many people seem to have selected.

Tom

 

[nsxtasy]

As for tire sizes, I am proposing 205/40/17 fronts and 245/40/17 rears.

Those will work. So will 215/40-17 and 255/40-17, which is a more common fitment for 17"/17" wheels. What's unusual about what you are considering is that the front wheels are somewhat wider than the optimal 17x7 or 17x7.5, and the rears are somewhat narrower than the optimal 17x9. A 17x8 wheel is at the high end of the approved range of rim widths for 205/40-17 (7.0-8.0), so that combination in front may look stretched. OTOH, a 17x8.5 wheel is at the low end of the approved range for 255/40-17 (8.5-10.0), so that combination in the rear may look bulging. And if you combine 215/40-17 and 245/40-17, you raise the possibility of TCS problems. So there are slight downsides with any of these combinations. But any should work...

 

[TCroly]

Ken,
You reached exactly the same conclusions that I had reached. I understand that there is some compromise here, but I am making it because these wheel sizes are what are presently available for the low close-out prices on a wheel that I like. But I don't want to buy them if they are going to cause problems or end up looking bad.

Tom

Those will work. So will 215/40-17 and 255/40-17, which is a more common fitment for 17"/17" wheels. What's unusual about what you are considering is that the front wheels are somewhat wider than the optimal 17x7 or 17x7.5, and the rears are somewhat narrower than the optimal 17x9. A 17x8 wheel is at the high end of the approved range of rim widths for 205/40-17 (7.0-8.0), so that combination in front may look stretched. OTOH, a 17x8.5 wheel is at the low end of the approved range for 255/40-17 (8.5-10.0), so that combination in the rear may look bulging. And if you combine 215/40-17 and 245/40-17, you raise the possibility of TCS problems. So there are slight downsides with any of these combinations. But any should work...

 

[Hapa88]

I wish I could state things as elequently as Ken. He basically touched on all the points I was trying to get across.

Have you contacted Tire Rack directly to see what they recommend? Everytime I try to see SSR wheels that fit the NSX on their website, no SSR model ever comes up on their "Upgrade Garage". They have a pretty knowledgable staff and have done lots of research, call them and make sure the wheels you are looking like would even fit. That'll help guide your decision.

I'd say, don't compromise. If there seems to be fitment issues and you think you may not be happy in the end, pass up the deal (regardless of how good it is).

 

[TCroly]

Have you contacted Tire Rack directly to see what they recommend? Everytime I try to see SSR wheels that fit the NSX on their website, no SSR model ever comes up on their "Upgrade Garage". They have a pretty knowledgable staff and have done lots of research, call them and make sure the wheels you are looking like would even fit. That'll help guide your decision.

Yes, I am in touch with Tire Rack. The applications for the NSX on their upgrade garage push the fronts wheels out by 23mm to 31mm and the rears by as little as 18mm to as much as 48mm, compared to the stock offsets with the 15/16 wheels. The general advise that they are giving me is that I am best to maintain the OEM position of the wheel. And the advice that I am getting from the NSX community is to move the rears outward by 45mm and the fronts out by 34mm from stock. The guy at Tire Rack said his fitment specialist said of this setup "I hope the guy has some massively wide fender flares"

But I think that I clearly understand the choices and the compromises associated with each choice.

Tom