What are the issues with putting larger than normal size factory wheels on a car? Is it safety, performance, car handling, etc? Are there any advantages to this modification?
If the larger wheels are also wider, you may be overloading the outboard bearings, and they will fail prematurely.
Your speedometer will be off, reading lower, which may get you a ticket.
The steamroller tires you see on those kids cars rersult in DISMAL HANDING. They normally only provide increased traction in a straight line for acceleration.
I assume you’re talking about those rims that are like 9 inches tall and like 20 inches wide.
Upsizing, you’ll get a tad bit better handling which will result in a harsher ride and be more prone to damage from potholes, curbs, etc.
Advantage: They look way cool.
Disadvantage: Everything else.
Use the +1 and +2 options at tirerack.com to see which wheels will work correctly with your 325i.
Larger than factory wheels that still wear tires with the same outside diameter and tread width, will show increased handling capability, may run cooler tires at higher speeds and may provide better brake cooling. All this depends upon the make of car and lots of luck to attain. Otherwise, they are more prone to damage, ride harder, can decreased load capacity and cost more to replace. That they look cooler is subjective. When I see the choice made for that extra alloy over factory recommended, they can look out of proportion to me.
Perfect example is a truck based SUV with 20+ inch rims that practically negates all advantages they may have over a car.
Advantage: They look way cool.
Disadvantage: The look really silly.
The only advantage is style, which is entirely subjective. I have never seen aftermarket wheels which look better than the factory offerings we have today, or even in the past 15-20 years. To me, they just look like a ridiculous fashion statement and ego trip that screams, “look at me! I spent WAY too much money on rims for my car!” This especially applies to people who spent $400 on a rusted out Caprice or Delta 88, then spend $4000 on new springs and 24" rims and tires with no sidewall. Yes, I have actually done such projects in the past. I don’t agree with doing the same thing on a $30,000 beemer, either.
Disadvantages are numerous. You will experience unusual handling, increased road noise, a MUCH harsher ride, an inaccurate speedometer and odometer, rapid wear of suspension and brake parts, dramatically increased cost of tire replacement, as well as having to do it much more frequently, and, if you actually drive the car and are any less than a perfect driver, you will most likely have to occasionally replace individual rims. If you even so much as look at a curb or a pothole with those things on your car, they will get scuffed, scratched, dented, or otherwise damaged.
If you want to make your mechanic rich while giving him a bad back, these may be for you, though. I had a customer once with a Lincoln Navigator who had, if I remember correctly, 26" wheels. He spent several thousand on wheels and tires in the two years I was working on that truck, much of which was on the tires. He said the most he could get out of a set of tires in that size was 10,000 miles, and those were so hard he couldn’t get traction in the rain. He was in the shop at least every month having brake and suspension parts replaced, including pads and rotors, tie rod ends, ball joints, sway bar links, bushings, etc. This was bad for us, too, because those wheels and tires probably weighed 130-140 pounds each! This may be why he couldn’t keep that truck in brakes. He finally put the (much better looking) factory 17" wheels back on the truck and, guess what, stopped having problems with it.
What size do you have now? What year? The only new wheels I would put on a 325i would be larger factory wheels, preferably ones that were an option for yours. Others just don’t look right. You can get ‘new’ (lightly used) factory rims as ‘take offs’ from a tire/wheel store or BMW dealer, or ebay/craigslist.
I really need to take a picture of this truck near my house. It’s an F-150 with large enough rims that the tires are barely there(think 17s on an older Civic sized tire). There’s 2 or 3 more vehicles there with their ghetto chrome look