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Stiff sport suspension-options to soften?

Discussion in 'E53 X5 (2000-2006)' started by PaulBSFO, Jun 15, 2008.

    PaulBSFO guest

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    We've had a 2004 X5 4.4 (E53) with the Sport Suspension and 19" rims for about a year now, and would like to soften the ride a bit...jarring is the best way to describe it, except on the smoothest of roads. We also have an '01 740i w/Sport Suspension, and that car rides very nicely, so it's not like we want it to ride like a '70's Cadillac or anything. Are there other folks out there that find the sport suspension on the 4.4's too jarring, and if so, have you done anything about it? Am thinking that going down to 18" rims is one option (would have to buy 3 rims, since we have an 18" spare), then the more drastic one is to look at non-sport springs / shocks, but all those options are costly to say the least. Anyone out there softened up a 4.4 X5 w/the sport suspension? Ideally, we'd love it to ride more like the 740 sport, but obviously the X5 is a truck of sorts...
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    I don't have experience w/ X5, but looking at the Tire Rack, they show a max rim size of 22" for an X5 4.4i w/ sport package, recommending a 285/35-22 tire size. Using http://www.1010tires.com/TireSizeCalculator.asp and entering the stock size (255/50-19 fronts, or 285/45-19 rears) and then the 285/35-22 size to compare, it says the overall diameter of the larger size wheel/tire is 29.85 inches, compared to stock of 29.03 inches, and as 1010tires flags a warning if the diameter difference is beyond what's recommended, that diameter difference apparently stays within appropriate range.

    Theoretically, any wheel/tire combination that's 29.85" diameter should fit the vehicle without problem. The Tire Rack winter tire section shows options for 18" & 17" tires. If a 17" wheel/tire combination will fit your vehicle, then to soften up your ride, you could use a 17" rim with a tire size that could be up to 29.85" dia. The Tire Rack's winter size recommendations are nearly the same overall diameter as the stock 19" rims, and take you from 5" sidewall height to 6" sidewall height (according to the tire size comparer). However, (again theoretically) there's room to fit a larger sidewall. 1010tires says a 255/65-17 is slightly beyond the 3% recommended diameter difference (which would be about 6.5" sidewall height) and a 245/65-17 yields a 6.26" sidewall height, which is not 3% over stock.

    Going back to Tire Rack to check if there's anything made in that size, apparently that's an uncommon size, and the only tire in that size is a Blizzak. Same for a 255/65 (just for interest). Unfortunately that throws you down to 255/60-17, which Tire Rack shows a number of street/sport truck tires available. I searched tire sizes by vehicle after selecting an X5 4.4i w/ sport pkg. and then custom sizes, so that (in theory) the Tire Rack tire selector would only choose tires it deems appropriate to be used on your X5.

    Since you're not looking at snow tires, you may want to stick with the same width as the stock tires so as to less radically alter the general handling. After that, you have to look at the construction of the tires. I'm no truck tire specialist (consult w/ a Tire Rack salesperson) for what's safe for your car, but my guess would be the cheapest tires are going to be the mushiest because their construction (again, in theory) would have less sidewall reinforcing. Might not have the wet weather grip you're used to either, depending on tread compound. Steering response, lateral grip, etc. (most of the benefits of a performance oriented wheel/tire combo) would likely be less than what you're used to w/ the current wheels/tires. Adjust your driving style appropriately.

    The last question for anybody that's done it or the Tire Rack folks is whether you can get the desired result (less harsh ride) with only a 1" change in sidewall height (each 1" change in wheel diameter gives you 1/2" change in sidewall height - since the tire sizes available end up being same overall dia. as original, you gain your sidewall height difference only from the 2" drop in wheel diameter.)

    Tires _could_ be the easiest solution if it'll work the way you want. Otherwise, changing the suspension components might be what you have to resort to. I don't think Koni makes FSD's for X5's, maybe you should give them a call and put in a request!
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    Jeff Gomon South Central Region Vice President

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    Harsh Ride...

    I have a 2005 4.4i with the same 19in wheel sport setup. I have to ask, do you have the optional 3 position ride height adjustment option? I ask because it has been shown that X5's with this system (basically an air bag setup), and the sport suspension have a less harsh ride than the stock sport suspension alone. My X5 came with this option and really doesn't have a harsh ride, in my opinion. I have ridden in X3's that have a much harsher ride and almost "buck" on the highway. Not saying to "live with it" just perspective.
    You can also move to the 17" wheels from the 3.0i X5 and benefit from the taller sidewall of those tires. More sidewall will translate into more absorption of impact, but not so much cancellation of spring rebound of a Sport Suspension. It will make a difference, but you will give us some handling performance characteristics such as crisp turn in. Or as least as "crisp" as a 5k lb. SAV can have...LOL....lol...
    As you stated, changing springs etc would be costly. The easiest thing, in my opinion, would be to change the tire size. You might not notice that big a difference going from 19" to 18" rims, but I could be wrong. I think tire choice will have a lot to do with the result as well. Do NOT buy a LT tire as they have stiffer sidewalls designed for heavier weights and towing. A passenger type tire in a 17" or 18" will give you the best ride, but will not be great for any towing, if you do that.

    Hope that helps in some way.
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    This X5 Sports package should not ride hard as essentially it is a extra heavy 5 series with sports suspension. I have however seen this before and it is likely caused by your tire choice, not size of tire but actual brand and compound of tire. BMW suspensions are tuned for certain tires. E-mail me off forum and about what you are running for tires and I'll try and help you make it softer.

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