Hello -
I just went through all this, installing 15mm spacers.
First, what wheels are you trying to install? You have to look at the back mounting pad of the wheel. The early NSX rims (1994-2001) do have reliefs on the back, so a little stud protrusion for the adapters would probably be OK. I, unfortunately, was mounting 2002 NSX rims - the back mounting face on those is practically flush, so the 15mm bolt on adapters were not an option.
Those TC sportline adapters are fairly new. Not too sure if anybody has tried those yet.
I ended up going with the standard 15mm H&R adapters and changing the studs. If I had to rank which was more difficult, changing the studs or changing the shocks, I would say changing the shocks was more difficult.
To change the front studs, you remove the brakes and unbolt the hub unit. It was necessary to create a small relief on the hub carrier to fit the stud through (the relief was necessary on both front and back.) The front was fairly straightforward.
The rear studs are slightly more complicated, but not impossible. You need an impact wrench to remove the axle nut, and some type of a puller to slide the hub unit away from the drive axle splines.
If you've never done it before, it would probably take a whole day plus to change out studs, so the bolt ons would probably be a better solution. Plenty of people here on Prime have the 25mm bolt on spacers, and have few problems except for frozen/stripped studs sometimes.
You may need to be the guinea pig on the 15mm bolt on spacers though. Before you order, check the back mounting surface of your wheels. If that surface is flush, you will probably need to pick the other spacers and change studs. Personally, I would not cut the factory studs (I measured and they were somewhere between 20-25mm long), and I think the mounting nuts will still extend out from the face of the bolt on spacer.
Hope this helps. By the way, I think the spacers do greatly improve the look of the factory wheels - they were worth it.
- Frank