I have a chance to buy a set alloy wheels for my newly aquired 164. My stock wheels are 15 X 5.5 wth a 40mm offset. The wheels in question are from a S80T6 and are 16 X 8 with a 43mm offset wearing 225X55 tires. So far as I can figure there's only 1% difference between the circumference of these wheels/tires and the stock set up. The width is a concern. Does anyone know if they will rub ?
Thanks

The following only addresses the 'width' problem -- the diameter is another matter that is more obvious, and I won't cover that herein.

Your concern is similar to one that I had regarding putting large alloys on my 240. I'll use this as an example, and then address your numbers.

My 240 has, as standard, a 14x5.5", ET=+20mm (that is, a 20mm offset), steel wheel. I put a 16x6.5", ET=+25mm, alloy wheel on it, which was rather a close fit, enough that there was almost no room between it and suspension pieces for the inside edge wheel balance weights; they had to be replaced with "tape" weights. Why?

Ordinarily, when you go to a wider wheel of the same offset, half the increased width is applied to each side (inside and outside edges), so going to, e.g., a 1" wider wheel adds just 0.5" to each side. However, I exacerbated the situation by using a wheel with a greater offset (as you have); this extra 5mm (or ~.2") shifted the centerline that much, and brought the wheel a total of about .7" inward (and only .3" outward), and so most of the increase in wheel width impacted on the inner side of the wheel, bringing it close to the suspension pieces. Combined with a greater tire width, this can be troublesome.

Now, in your case, you're going from a 15x5.5"x40mm wheel to a 16x8"x43mm wheel. Here's what's happening for you.
Based just on wheel width change (assuming equal ETs), the 5.5 to 8", or 2.5" increased, difference would add 1.25" on both inside and outside edges of the wheel. But you, like me, are using a wheel that has additional offset, in your case only 3mm more. That's not much, only ~0.15 inch or so. That means that the shift in the wheel's centerline position inward is that much, and the result is that the new wheel will extend outward about 1.1" more than the old wheel, but also extend inward about 1.4".

Ideally, on RWD Volvos (which have a positive offset), you would want (not that you can find) a replacement wider wheel that has a decreased offset equal to half of the increase in wheel width, in order to keep the inner edge of the wheel the same distance from the suspension.
[This ignores the other side of the coin, that being clearance with the outer fender, something 'Walrus' mentioned; as well as the additional concern from reducing the offset that might overload outer wheel bearings, thus suggesting keeping the offset the same].

Take note that on my 240 (admittedly a different suspension), a mere 0.7" inward intrusion reached a practical limit (any farther, and the wheel would scrape on the suspension). You are contemplating bringing the inner edge of the wheel almost one and a half inches inward -- that could be a serious problem, depending on your 164's suspension.

Although I have a 164 (a '75), I haven't tried to fit my 240's wheels on it, and I don't know if they would have a problem. Also, my '75 164's suspension is not quite identical to previous 164's such as yours -- for one thing, my '75 has a standard 20mm ET (like later 240's, but with a different suspension), but all earlier 164's has a 40mm ET as you have noted.

Be cautious.

Good luck.

Very nice write up!

Here's my 2cents that's been gathered through the years. Hahah, i'm not old. But anyway, I have done research in this and played around with differing wheel and tire diameters, widths, offsets, you name it. I usually play around on this website. The 164 that you will be dealing with, has quite a bit more room to the inside of the wheel when compared with a 240, due to the fact that the 240 has a strut type design vs. the A arm design on the 164. My thoughts with the swap are going to be that the tire will rub under very hard suspension compression (or if your car is lowered much) on the inner fender in the front. In the back and also in the front, there might be a tad of rubbing on the outer fender, which you can easily enough bend/shape to fit the tire and usually not rub. I have a friend who has fitted 17x7 alloy wheels from some of the newer Volvo R models on his 142 which is lowered. He did not have any problems other than rubbing on the inner fender over large bumps on the freeway, and his car was lowered a decent amount.(more than one inch) With the 8" wheels though, it will be getting close, if not too close, because the wheel will be about a half an inch further in that the ones on said 142, and the curve of the inner fender is not working in your favor. It might work and it might not. That's what I have to say about it, it will be close, very close. You may be able to work it without problems or maybe you will have to move the wheels out with small spacers(5mm maybe and longer studs to match), or you might even need more than that, and if you do, you will very likely need to work on the outer fenders a little bit too. And then again, you can also bang away on the inner fender possibly as well, so as to make more room for the tire.

But I don't know, best bet is to find something that is about the same size and check it out. OR, you could use the tire calculator I have above, go out and measure the space you have available with your current setup, and compare it to the numbers it gives you on this site. I can do it for you actually if you give me the tire size, and then all you'll need to do is go out and measure the space available with the current 15x5.5s on it. THOUGH, lol, even after that, we still won't know how it will do when the suspension is compressed, but we will be able to get an idea if there will be any rubbing on the front or back. And actually, i think there might be some possible rubbing on the rear of the car on the inside too, now that I think about it... I have the same wheels on my car that you do, and I don't think that an extra inch and a half or so would work on mine...

FWIW! =D Good luck!
--
Kyle - www.OVTuners.org website and club Official Portland/Corvallis, OR - 1968 142 - current setup: 71b20b SUs, m40, part. stripped, custom CAI, 4-2-1 FI man., Simons exhaust... IPD sways +more

i have fit a set of 17's in the rear of my 145. the tire size was 235/45. the offset on the rims was 25mm had to roll the fender slightly. the car is also lowerd 1 1/2 inches. best of luck

They might. I've run 205-75/15s on my 164 and had to do a few seconds' work
at the bottom front of the rear fenders, the inside of the lip, with a 3#
hammer. Invisible unless you know where to look. Yours, being a little
wider may need a little more but probably not much.
--
George Downs Bartlesville, Heart of the USA!

Hi. Also keep in mind that tire manufacturers are allowed a 7% variation in actual tire size. I was surprised to learn that just recently.

Steve