First off, i've done my searching and i found out some stuff but not everything. I already understand about the number on the tires, but my question come in which is best.
I've upgraded my tires to 17X8 a while back from the stock fittiing, and now its time to get some new rubber. Right now, I have 215/45/17 all around and im thinking unless if get other feedback thats what i might have to go back to.
But i'd like to change the size. I was think either 245/40/17 or 235/40/17 or 225/45/17, or back to my original 215/45/17. I understand the speedo problems, but i feel these tires all fall in a good range.
Questions: what r yall sitting on? Is it better to even mix them up, but some bigger on the back and smaller on the front. Also longevity is very important to me. Im 18 and on a budget ghead , and im trying to squeze as long a life as i can out of em. So longevity and comfortability over performance.... (i dont race, its kind of pointless in my 318, but i do drive spirited.)
Also, is there a big difference in comfort when you switch from 45 to 40% profile? And would getting a larger foot, say 245 as opposed to 215 allow my wheels to last longer?
Any response, somehow related to the question of course , would be much appreciated.
oh! and as a side note, how much does it cost to professionally mount tiresn on the rim and get them balanced. Im thinking about getting tires online cause their cheaper, but if the cost to mount and balance them overides my savings (cause at the shop they do that for free) then im just gonna get tires from the shop. I hope it doesnt' work this way, because i can find great deals online.....
Im sitting on 16's I cant remember the exact size. BF Goodrich G-Forces.
Im pretty sure the first number is the width the second number is the profile and the third number is the rim size.
Theres definitely a difference in ride comfort from 16, 17, 18. I ride on brick roads alot in downtown Orlando and 16s are even uncomfortable at times. Ive driven my dads 2000 GT and the 17s are noticeably more painful on your ass. I cant even imagine 18s on a brick road. But hey its worth it to some to sacrifice comfort for style, including myself. Ive never changed profile so I dont know the difference just in that, but all three of those sizes have different profiles.
I'm running 17 x 7.5 with 215/45's. There is a pretty considerable difference between 40 & 45's . . just imagine how much difference 2 or 3 PSI of pressure makes on your ride characteristics. Longevity is not a factor of footprint, but rather, the treadwear number.
If you want your tires to last long, first make sure the treadwear rating is good. Then go for non-directional tires and make all 4 wheels the same size. This way you can rotate them all. With directionals, you can only rotate front and back on the same side, unless they're different widths. If the widths are different, you can only rotate left and right, but only if they're non-directional.
I've been thinking of posting something on wheels and tire sizes for the past few days, after doing a lot of research and thinking over the past few months. Trying to answer the same questions you, and probably alot of us, are trying to answer, with no good, succint overview on the board. I was goingto write my missive in the form of stated assumptions ands fcat and then let people on the board have at my reasoning and conclusions. So, if i do that i think i'll answer some of your questions and also give you a few more things think about. Here goes....
1. You should make all 4 tires the same (all 235 for example) so that you can rotate them amongst all four wheels, leading to longer overall longevity, especially if you have any wheel that can't quite be 100% aligned properly (like i do) or you're lazy and don't always check your tire pressures every week or so (wrong tire pressure fornt or back can lead to different wear patterns - duh!)
2. You should make all 4 tires the same (all 235 for example) rather than 225 front and 245 rear, to keep the car as balanced as possible, in terms of understeer vs oversteer. BMW's are already tuned to understeer (the front tire pushes out before the rear) with existing tires that are all the same, and having wider tires, with more grip, on the back will exacerbate this unless you compensate for it with suspension, camber etc. However, after reading alot on this board and other boards and various BMW magazines, if you think you're going to be able to tune your own suspension to this degree you are probably smoking rope.
3. You should minimize the overall width of your front tires to reduce tracking. The wider your front tire the more likley it is to track, that is to follow minor imperfections in the road and give your car a wandering around sort of feel. The narrower your tires the less this happens. This is why you see alot of people with 225 on the front even tho you have 245 or more on the rear.
4. You should always keep your overall tire/wheel combo diameter about the same so as not to make undue modifications to your speed display, or to upset other items like traction control if you're lucky enought to have it.
5. If your overall tire/wheel combo diameter is too big you are more likely to run into rubbing issues and perhaps have to either mod your suspension or roll your fenders. So again, keep your overall diameter close to original.
6. Similarly to point #5, overall width should not get too high unless you want to have to roll your fenders, or at the extreme, not be abvle to fully turn your wheels before they rub ont he inside of the wheel well. On my 1996 328i the max appears to be 235 - 245 before you will need to roll fenders.
7. The advantage to a larger wheel (18 vs. 17 for example), assuming you are keeping an overall contstant total diameter, is that the profile of your tire will go down. A lower profile tire has less deflection as you corner and therefore provides better grip, by keeping a larger and more symettrical contact patch in contact with the road.
8. The disadvantage to a larger wheel and the lower profile mentioned in #7 above, is that your ride comfort will diminish, because you will lose some cushioning provided by the deflection of the tires rubber. A lower profile tire will deflect less. If you want a good personal example of this just go ride your bike over a bumpy road, once with a little air pressure and once with max air pressure. You will definately feel the difference.
9. A disadvantage to a larger wheel is that you will pay more
10. A disadvantage to a larger wheel is that the wheel will weigh more. One thing i intend to do (i am tryong to choose between a 17 and an 18 wheel) is compare the price and weight of an expensive (say BBS) wheel at 18 with the price and weight of a cheap wheel (ASA) at 17. My bet is that the so called light wheel that i am paying big bucks for at 18 will weigh about the same as the cheap wheel at 17. So why not save a butt load of cash and by a 17 cheap wheel, rather than an expensive 18 wheel and all i'll lose is a little looks.
11. An advantage to a wider wheel (8.5 vs 8.0) is that i can put wider tires on it. Wider tires increas the contact patch, providing more grip for both acceleration and cornering.
12. Lower profile tires cost more and wear down faster
Note that Ness's comments on the 17 being more painful than the 16 etc, has nothing to do in fact with the size of the wheel but instread has to do with the lower profile tire on the larger diameter wheel.
So, in summary (assuming you are not tracking the car):
1. By all 4 wheels and tires the same, including width
2. Keep the overall tire and wheel combo diameter close to original
3. Unless you really must have an 18 wheel for looks, stick to a lower cost 17 wheel that will be as light as a much higher cost 18 wheel
4. Don't go over 235 for the front tires - this will reduce tracking (which means 235 for all 4 wheels assuming you stick to #1 above)
5. Stay to the lower size profile tire if you want higher perfomance and less comfort with increased price and lower longevity, and a higher size profile tire if you want more comfort and less perfomance, along with lower cost and longer wear.
For your wheels specifically, i think you should do the following, if my memory on what will fit is accurate:
235/35/17 or 235/40/17 or maybe even 235/45/17 for more comfort and closer to original - i think any of these will keep you close to original overall size
Great write-up, should post somewhere permanent as a guide.
235/45/17 have been my best combination with regards to ride/comfort/durability/price.
Up here we pay $10.00 bucks a tire for mounting and balancing...but you have to be careful which shop you use. Some shops can't handle the 17inch mags with machined and/or polished edges.. they scratch the crap out of them.
Much appreciated everyone and andrewgrhogg, thanks a bunch for the extensive write up. It was very informative and actually answered a lot of question on the whole wheel topic.
From there, i think i'll stick to buying all the same size, and it seems the consensus is that i could move up to a 235/45/17 from my 215. Looks like i'll keep a 45% profile, and depending on the cost difference ill choose from the range of 215 width up to 235.
Another quick question.... does increasing the width of the tire affect the look at all. I was just thinking, does it maybe give the car a more aggressive stance, or is change purely in the performance of the tire rather than the looks.
I think 235/45/17 might be too tall of a tire. To stay in the original diameter you should stick to either 225/45/17 or 235/40/17 all the way around. Try to stick as close to the original 25 inch diameter. Always shop around to get the best price on tires.
check the product review forum you might come across some decent reviews for tires, i have one regarding the Fusion ZRi tires which im very happy with, and very affordable, however if you want a longer lasting tire may i suggest the pirelli M&S's (the higher performance ones)
This is a cool site i found for tire sizes. Allows you to quickly see what will work wihtout having to constantly chnage the new tire size to see what will work and what won't. Using this tool and entering your original tire size (but you ought to enter your original original tire size just to be safe), looks like you can get away with 235/40-17 or 225/45-17 and stay within 2% error.
As for increasing the width, it will provide some additonal stability and anti-roll, and from a looks perspective you will only be able to tell if you look from the rear or front of the car. The rear is where the looks really matter, because it is usually easy to see the tires from the rear, whereas on the front the front fender usually blocks your view unless you are lying on the floor! A wider tire just looks more aggressive and "track" like and will give more grip for forward accleeration, and increase lateral g holding capabilites in corners. But they will also cost more.
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