New member and also a new and happy owner of a 2001 GS430. Bought with 11,500 miles, can you believe, like new. Love the car, hate the small rims. I'm thinking of going to 18" rims. Maybe 245's or 255's. Any idea if this would be a problem with handling, and also any suggestions on the size. Also, once larger rims (tires) are on the car is it a major problem to get the speedo calibrated correctly? Thanks TonyB

Did you notice you posted in the Website Suggestions and Feedback Forum? I am sure a mod will move this in no time.

Anyway, if you go to 18s, you can run 245/40 tires and no calibration is needed since this tire spec will keep your outside diameter within OEM spec. Typically, people run 18x8.5 rims. The width and offset will be based on how aggressive you want the car to look. Also, there is the option of staggered wheels where the wheel is wider (not taller) in the rear. +38 is a good safe offset to start with.

You can post more details on your preferences and we can go from there.

Thanks for the info Neo. I think that I'm going to go with the same size tires all around. I do want the car to look more aggressive, but do not want to give up a lot of handling. My other car is a twin turbo 300ZX, so handling and road feel are important to me. That's why I don't want to go any higher than 18"s. On the same subject, do you think that going with maybe 255's would be too much as far as the ride and handling department. Right now I have the 225 16's, so anything would be an inprovement. Any further comments would be appreciated. Tony

If you are going the same size all around, it will be safe to run 18x8.5 +38. The rear will not look as flushed but you are basically limited by the room in the front wheel well. You can push a little if you run 18x9 +41 or 18x8.5 +35. I would not go with 255/40 tires though as there will be some rubbing unless you are planning to do some fender modding and/or run the camber more negative. The rear will be fine with all these sizes as the rear wheel well has more space.

Thanks for the info Neo. Looks like I'll stick with the 245's. Not being a tire "GURU" like it sounds like you are, what is +38? Is this something that I need to know when purchasing the rims and tires? Thanks again Tony

Offset is very important in determining if a set of rims will fit on a car. In addition to the width, this number helps to show how flushed to the fender the rim sits. This is not the definition of offset (but you can find that on the net ) but in the real world, the combination of those two numbers will determine how the rim sits in your fender well.

The lower the number, the farther out the wheel moves towards the fender. For example, 20x8.5 +38 will be inside the fender while 20x8.5 +10 will sit outside the fender. (The offset number is a mm neasurement.)

i learned something new today thanks

Just to make sure it is clear, the sample offset numbers are for the 2nd gen GS. For example, wheels with +25 will be outside the wheel well for the 2GS while will be accommodated (staying within the wheelwell) by other cars.

Thanks again Neo, I, as well as some members learned something from that info.

Actually that offset number determines how deep the face of the rim sits in the rim. To use your example, +38 the face of the rim will sit closer to the front of the rim. +10 will sit deeper in the rim. The lower the number, the deeper the face sits in the rim giving the rim a bigger lip. It's true though because of the lower offset the rim will be pushed out more from the fender. I'm not saying Neo is wrong just in case, I just wanted to give another p.o.v.

That is not entirely true. I did not want to talk about face location because it is not fixed. In a typical wheel, you are right. On custom wheels, though, where you can vary the lip size, you can build up the thickness of the the mount plate. If it is thicker there, then you get less lips. Offset does not change. Why would you want to do this? BBK clearance. In addition to companies having different faces that curves slightly differently to deal with BBKs, the mount area can also be thicker. How do I know? My next wheels were built this way.

The only real absolute is the outer edge of the wheel (lips or face if no lips) moving closer or farther from the hub or the fender if you look at it from the other side.

Again, I did not want to define offset as most will need diagrams to help and these are all over the net. I just wanted to get into cause and effect.