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Discussion Starter · #1 ·
Looking for new rims, probably 18s or 19s. I'm going to buy some BMW knock-offs from eBay, But I want to kow the width limits on the rims. Sure I could fit a 10 inch rim up front, but it would have to be mostly in off-set. Yes I want off-set, but I want to know how much offset I can have on rear and front (w/out taking both lanes of a street, I want to keep it at the farthest: flush with the body), how much backspacing on both front and rear. My ideal rims would be the 18" 5-series rims, parallel rims, you've seen them, they're 8" on the front and 9.5 on the rear, rears have a lot of offset. I'm also considering the Schnitzer 18" which can be had on eBay for 399 plus 125 shipping, those are 8.5 all around. I've seen pics of the Schnitzers on e46 330ci, so I assume they fit, but I'd prefer to squeeze the 9.5s in the rear for improved traction. Someone with rim-fitment information please respond!! :dunno:
 

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I just got my car so I am going to wait until the Continentals wear out, put some winter tires on the stock 16s and get some nicer rims and tires for spring, summer, and fall.

It rains a lot here so even the summer tires have to handle wet roads well, more so in the summer where it can go a few weeks without rain and then you have all that oil on the road with the rain making it slick.

That said, I would be looking for performance. While I like the look of a nice wide tire, width does not always equate to performance, so what I am mainly looking for is a wheel that is significantly lighter than stock. That should also result in a more comfortable ride. I don't want real low profile tire as I think they give a harder ride and look like wooden wagon wheels with the wheel tire combo mostly consisting of the wheel.

The BBS brand seems to be significantly lighter than stock (8-10 pounds lighter?) as are the SSR Competition, although I have heard a lot of people recommend BBS and only one recommend SSR.

One poster here had some links in his sigline and I picked up on a wheel company in an article in that link. Complete Custom Wheel apparently make wheels that allow 10" tires to fit under a 3 series body without mods to the car - although I am not sure of how changes in offset would affect the handling. One thing I don't want to give up is one iota of handling - I love the way my 325 Ci handles at speed and it is just the plain jane version.
 

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Discussion Starter · #3 ·
Due to the IRS, increase in width can always improve handling, as long as the same tire is preserved (tire type, not width). I'm looking to fit a 265/35 tire on my rims on the rear, I'll check that link, seems like a good idea. To get a better ride, you musn't necessarilly improve sidewall height, just get a softer sidewall. I'm going to buy some MAx Performance Summer tires from the 'rack, and so handling is my biggest concern, as is traction to the rear wheels. It's not so much the look of little tires on big rims, it's the look of a filled out wheel-well. Is your 325 a sports package, it would explain the rough ride, mine is, and I would go for even rougher. My most desired upgrade is the praxis suspension, so I could drop it to 'track' and handle like a stock car (race car). Any mods you have planned for your car will either stiffen the ride- for better handling, or mush the ride to weaker handling. It's a string with two ends, which end do you want more right now?
 

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bluejeansonfire said:
It's a string with two ends, which end do you want more right now?
1) Width does not always mean better performance, and offset of a wheel/tire can not only affect performance in a detrimental manner, it can also affect mechanical reliability - specifically the life of wheel bearings. Done right such issues can be addressed - done wrong and you have a nightmare 10/20/50 K miles down the road. I am not saying don't do it, just that these issues must be taken into account.

2) A stiffer suspension does not necessarily always equate to better handling, especially in the real world where roads have potholes.

I am looking for a nice balance of comfort and handling. I don't race, but if I want to get sporty I get on my Ducati and go for it - not only is the bike more able than the car, if I screw up there is less likelihood that someone else besides me will pay the price (a 700 bike/rider combo at 120 MPH is a lot less dangerous than a 3500 pound car/driver combo at 120 MPH).

Also, if I break the bike over the weekend I can still drive to work on Monday (two broken bikes, a Suzuki and a BMW now sit next to the Ducati).

So, while I look to improve the handling of the car, there is no reason I can't also improve the ride comfort. A lighter wheel/tire combo allows the suspension to not work so hard and be more compliant with road irregularities (keep the tire on the road) and at the same time deliver a better ride because a bump in the road is not near as jarring as less mass is moved and less energy is transferred to the car body.

Of course, the stock suspension is tuned by BMW when they design the car, for a particular wheel/tire weight and size, but I can help it within a certain range of unsprung weight - which BTW, as a general rule of thumb, every pound of which is worth ten pounds of sprung weight. This is one of the advantages of IRS, not only is the suspension able to handle road irregularities on one side with little effect on the other side of the car, but just as importantly (maybe more so actually) the unsprung weight of an IRS suspension is generally much less than that of a non-IRS suspension.
 

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Oh, and another thing I am looking for; quiet. I am looking for a tire that has the minimum road noise, esepcially on noisy pavement.

I have been around noisy stuff so much (I used to be a pro mech) and I injured my ears in a training accident in the military, that I now have tinitus. Any kind of noise, like the road noise you get from tires on rough pavement, sets off a reaction in my ears that multiplies the sound by a certain amount, so a quiet car is a more comfortable and enjoyable car for me.
 

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Discussion Starter · #6 ·
Adventure Rider said:
1) Width does not always mean better performance, and offset of a wheel/tire can not only affect performance in a detrimental manner, it can also affect mechanical reliability - specifically the life of wheel bearings. Done right such issues can be addressed - done wrong and you have a nightmare 10/20/50 K miles down the road. I am not saying don't do it, just that these issues must be taken into account.
How would one achieve "right". remember, this is not a swing arm suspension, I wouldn't be here if it was, I'd be dead. Now I could be quiet wrong, but from what I understand, as a spindle goes up and down through it's range of movement (in the IRS) it does not change it's vertical angle to the ground, unless the body flexes (which it will, but such figures are negligible). But because the angle is kept equal, load on the wheel bearing doesn't change, sure, now there's more leverage put upon the bearing, especially if the offset (lip on the outside of the wheel) increases (not ideal for handling necesssarily, but usually not destrimental on rear wheels of an IRS car. Like I said, I could have something wrong, my logic isn't the most impressive of my traits, but I can't figure out a way in which the leverage inflicted upon the wheel bearing would be improved, and I can't see a substantial lifespan decrease to the bearing either.
 

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bluejeansonfire said:
How would one achieve "right". remember, this is not a swing arm suspension, I wouldn't be here if it was, I'd be dead.
How a person achieves "right" is they ask people who know. I only know enough to be dangerous and therefore know that it is wise to ask people who know more than I do as to what works and what doesn't. Also, sometimes there is no "right", sometimes there is just pluses and minuses.

Now I could be quiet wrong, but from what I understand, as a spindle goes up and down through it's range of movement (in the IRS) it does not change it's vertical angle to the ground, unless the body flexes (which it will, but such figures are negligible).
The wheel/tire stays more perpendicular, but no suspension is perfect and depending on the setup and design the angle can change, just much less so than a non-independent suspension.

But because the angle is kept equal, load on the wheel bearing doesn't change, sure, now there's more leverage put upon the bearing, especially if the offset (lip on the outside of the wheel) increases (not ideal for handling necesssarily, but usually not destrimental on rear wheels of an IRS car.
It has been years and years since I was a mech, and only part of that time was working on cars (most of it was spent working on boats, tractors, combines - big heavy equipment), but I remember when I started off working at a Porsche/VW/Audi shop the owners of bugs would sometimes reverse the wheels on their bugs to get a wider stance (usually mostly for looks). Because the wheels had a pronounced offset that was now reversed, this put a lot of load on the wheel bearings and wore them out much faster. Instead of the load being centered on the bearings the load was now further out on the spindle and this increase in leverage was detrimental to the bearing life.

I have also read a few books on suspensions and recall mention being made of how wheel offset can affect both bearing life and handling.

I am just saying that it is something to consider and get expert opinions on when considering a change, especially on an expesnive car - more so when under warranty (may void the warranty).
 

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http://www.mirafiori.com/dave/s-wheels.html

Careful measurements must be taken before considering a wheel with different offset so that you know what range is acceptable for your application. Wheels with grossly inappropriate amounts of offset will greatly reduce the handling abilities of your car and put tremendous loads on bearings, ball joints, and steering components leading to eventual failure. You would be wise to give plenty of room to the modern low rider with so much negative offset that nearly ALL of the wheel/tire is OUTSIDE the fender so that you do not become part of the inevitable accident. The individuals that drive these cars are either ignorant of the mechanical torture they have put upon their cars or just irresponsible about their actions, both of which can be very dangerous. Another important note is that any change in offset will result in a change in steering geometry since the contact patches of the front tires will be a different distance from the pivot point of the front suspension. This will be especially evident at higher speeds or when turning sharply.
http://www.mazda6tech.com/articles/suspension/plus-sizing-for-dummies..html

Reduced steering feel. Due to gyroscopic effects, larger wheels are harder to turn left and right. Thus, a slipping wheel will not transmit as immediate nor as strong of a force to be felt through the steering wheel. Running a different wheel offset changes the car's scrub radius, which can multiply this effect.
http://www.jax.com.au/sc09_tips/body.asp

Wheeltrack is the distance between your car's wheels. It is measured between the rim centrelines.

If you fit wider wheels you will probably increase wheeltrack and this is usually associated with a change in wheel offset, increasing the loads on bearings, axles, suspension joints and steering tie rods.
 

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Discussion Starter · #9 ·
Adventure Rider said:
The wheel/tire stays more perpendicular, but no suspension is perfect and depending on the setup and design the angle can change, just much less so than a non-independent suspension.
How does a live axle change angle at all, other than body flex?

Adventure Rider said:
It has been years and years since I was a mech, and only part of that time was working on cars (most of it was spent working on boats, tractors, combines - big heavy equipment), but I remember when I started off working at a Porsche/VW/Audi shop the owners of bugs would sometimes reverse the wheels on their bugs to get a wider stance (usually mostly for looks). Because the wheels had a pronounced offset that was now reversed, this put a lot of load on the wheel bearings and wore them out much faster. Instead of the load being centered on the bearings the load was now further out on the spindle and this increase in leverage was detrimental to the bearing life.
Swing-arms, not IRS: that may be the difference
 

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bluejeansonfire said:
How does a live axle change angle at all, other than body flex?
You mean with relation to the road surface or the body or the axle itself?

If one wheel moves up while the other moves down you can get all kinds of differences in angle with relation to the body or the road surface.


 

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Discussion Starter · #13 ·
Adventure Rider said:
You mean with relation to the road surface or the body or the axle itself?

If one wheel moves up while the other moves down you can get all kinds of differences in angle with relation to the body or the road surface.
Well, there is body flex, movement of the springs will cause uneven relation between body and tire, but look at your pictures, even when the body is in no way linned up with the tires, the tire is perpendicular to the ground, unless the gound changes shape. and its a live axle, the wheel can't change angle in relation to the axle.
 

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bluejeansonfire said:
Well, there is body flex, movement of the springs will cause uneven relation between body and tire, but look at your pictures, even when the body is in no way linned up with the tires, the tire is perpendicular to the ground, unless the gound changes shape. and its a live axle, the wheel can't change angle in relation to the axle.
Right - I agree. The wheel typically will not change it's angle with relation to the axle with a "live" axle. With regards to the angle relationship to the ground however, you can get the wheel/tire to change its angle because the other wheel is moving up or down. This is the advantage of the independent suspension - that it will keep typically the wheel tire in a more perpendicular relationship to the road surface independent of what the other wheels are doing. Not perfectly (as the wheel moves up and down there are changes to the angle of the wheel - depending upon the design of the suspension), but to a much higher degree than a non-independent suspension.

I think we agree on this - all I am trying to say is that a person should be aware of the changes that a wider tire, especially in combination with a wheel with a different offset, can cause to the handling of a car.

You were asking about limits - the offset is one of the characteristics of a wheel that is a limit with regards to a fitment on a given car.
 

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Discussion Starter · #15 ·
Adventure Rider said:
Right - I agree. The wheel typically will not change it's angle with relation to the axle with a "live" axle. With regards to the angle relationship to the ground however, you can get the wheel/tire to change its angle because the other wheel is moving up or down.
Up or down off of the ground. Remember, the wheel is directly bolted to the axle, unless the axle bends, which would be catostrophic, all remain in same anlgle, except the body, which can move with the restraints of the springs, control arms, shocks.

Adventure Rider said:
This is the advantage of the independent suspension - that it will keep typically the wheel tire in a more perpendicular relationship to the road surface independent of what the other wheels are doing. Not perfectly (as the wheel moves up and down there are changes to the angle of the wheel - depending upon the design of the suspension), but to a much higher degree than a non-independent suspension.

I think we agree on this - all I am trying to say is that a person should be aware of the changes that a wider tire, especially in combination with a wheel with a different offset, can cause to the handling of a car.

You were asking about limits - the offset is one of the characteristics of a wheel that is a limit with regards to a fitment on a given car.
I agree, but i think that the intention of the IRS is not for improved handling, but more of a refined ride. In a live axle, unless one wheel is off of the ground, the two wheels are both perpendicular to the ground, and even when one wheel is raised off of the ground, it couldn't matter less that it isn't touching the ground, it's not getting traction, yet given all power, even if t is touching the ground, but weight is shifted such tire will spin relatively freel and have no improvement in acceleration.
 

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Adventure Rider said:
Oh, and another thing I am looking for; quiet. I am looking for a tire that has the minimum road noise, esepcially on noisy pavement.

I have been around noisy stuff so much (I used to be a pro mech) and I injured my ears in a training accident in the military, that I now have tinitus. Any kind of noise, like the road noise you get from tires on rough pavement, sets off a reaction in my ears that multiplies the sound by a certain amount, so a quiet car is a more comfortable and enjoyable car for me.
Most summer high performance tires will be louder and ride harsher than the stock Conits. The Contis are quite when new but do become louder once you're past half of the tread life. If you go wider than stock expect more trammeling and a louder tire, with a lower sidewall expect a more harsh ride and greater chance of a bent rims.

If a quite tire is a important go to Tirerack's website and read the owner reviews and survey results on a tire you are considering buying and pick a tire that scores well in ride and noise comfort.
 
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