RE: What is the widest tire I can put on my 17" rims?
I may be an ***, but I believe the link I provided will more than answer your questions. To summarize:
- The widest tire you can put on there without having it rub (first question), depends on what your wheel offset is, the section width of the tire you are putting on, and the relationship of the tire width to the rim width. By the last part I mean that a particular manufacturer will have a "design" width and an "acceptable range" of widths for a specific tire. Your Kumho 205/40R17's, for example, are specifically designed to fit a 7.5" wide rim according to the manufacturer, but the acceptable range is 7-8". On the design rim, it is 8.3" wide overall. Putting it on a smaller rim than the design width (like yours) reduces the overall section width slightly (0.2" or so), putting it on an 8" rim would increase the section width slightly (0,2" or so). In my opinion, and the opinions of most hard-core drivers, it's best to stick with the design width whenever possible if you intend to push the tires to their limits. But that's really beside the point.
- Putting a 225 width tire on your current rims (second question) could be a problem. To keep the same tire diameter (23.5" or so), a 40 profile would make it only a half inch taller, but good luck trying to find that particular size. You can get the same tire in a 215/40R17 that's pretty close, but the lowest profile you'll find for those tires in a 225 width is the 225/45R17's, which are 25" tall and I can almost guarantee they are going to rub on the bottom of your spring perch, just like my snow tires do without spacers (175/85R14 on stock 14", 40mm steel wheels). This is all assuming you want to stick with the same tire you have now, just a different size. I really don't have the time right now to go off researching others for you, it took me 3 weeks to settle on my own tires...
- Yes, a wider tire provides a larger lateral length for cornering (third question). But wider tires are only a part (a pretty small one at that) of the overall traction/handling equation. The 712's are a pretty sticky summer tire. With 17's, you don't have a lot of sidewall flex. That extra 7/8" of extra rubber isn't going to mean much if you've got enough body roll to screw up the suspension geometry in a really hard turn, which you will do with a relatively stock suspension. What you have will be fine. In fact, take a look at what the serious competition guys are doing. Chances are they'll have race rubber (V700's, for example) on the smallest wheel they can fit over the brake calipers. On my car, I could go with 205/60R13 Victoracers on 13x6" wheels (Diamond Racing, very nice, very cheap). The smallest wheel you could probably go with is a 14" without taking a grinder to your calipers... Most of the Neon autocross guys/gals I know end up going with a 15" wheel because a) it's hard to find a lightweight 14" wheel that won't break the bank, b) better tire selection (street tires), and c) keeps them in stock or street prepared classes where they can actually be competitive (assuming there are no Cooper S's on the track that day...).
- Lowering the car (second post, first question)... I'm going to assume you used lowering springs. That means that the only thing that really changed significantly is the distance between the bottom spring perch and the top spring perch/frame. Your tires sit beneath both of those. The distance from the top of the tire to the bottom spring perch does not change. Trust me, you will hit the spring perch before you ever hit the splash guard. Using lowering springs will tend to cause postive camber, which means the top of the tire sits out further unless you use camber bolts/crash bolts, etc. That may put you a bit closer to the rear trailing arm in back. Not so much of an issue for 2nd gens though. Even for 1st gens, 2 degrees of positive camber will only put a stock size tire on a stock rim about 1/4" closer to that arm... I checked... In general, lowering the car does not have any real bearing on whether a tire is going to rub, with the exception of really, really wide/tall tires up front on a really, really lowered car during a really, really tight turn. Really.
- I'm not generally one to toot my own horn, but yes (second post, second question), I am rather knowledgeable on the subject. I've had the pleasure of wasting thousands of dollars on mistakes over the last 6 years on this car. One of my main goals here is to prevent others from doing the same.
- From the pic, I would guess the bulbs are in the 4500F range (third post, first question). At least the headlights. The fogs look to be the stock bulbs, which are more in the 3200F range. I tried the higher "cooler" color temp bulbs for a while, but found visibility wasn't what I had hoped. Ended up going with a 3800F for now, but will probably go a little cooler the next time around. The reason it was brought up was because headlight bulb information is about as useful as how much a car is lowered or what width of tires will fit when the most critical points are left out. Those points being offset and tire section width, neither of which were mentioned until I transformed myself into an ***.
Hopefully the link I provided (the new post I did) will get stickied so questions like these don't come up quite as often. I wasn't born with that post tattooed on my butt, I had to figure out a lot on my own, usually at my own expense. Tire sizing seems to be one of those areas that is hugely misunderstood. I do try to provide the real help that people need, but most just blow it off because it isn't what they want/expect to hear. It doesn't help whe 20 yahoos jump on a post and say "yeah, I've got 17's/18's/19's and they fit, so you should have no problem." The truck guys are even worse... I've given up on them...