04-08-2020, 08:11 AM | #1 |
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MP HAS - uneven drop ?
I finally had the time to tinker with my MP HAS since my car was sitting a quarter of an inch higher on one side. After fine tuning everything I realized that the number of threads on each side is different. For example - even drop in the back was achieved by showing 6 threads on the rear driver side and 3 threads on the passenger side. Front was similar.
Explanation for the front could be the seats not pressed in the same on each side so I get it. But how about the rear? Could it be that the springs are uneven lengths? I know this has no affect on performance but it bugs me to the point of wanting to get rid of this suspension in favor of something else. Thoughts? Thanks in advance. |
04-08-2020, 08:25 AM | #2 |
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When I installed the suspension, my drop was slightly uneven as well (I think about 1/4" higher on the driver side). I was pretty certain that I had dialed in the same amount of threads but I reset it and redialed it and still there was a bit of an imbalance. After settling, there was still about 1/8" difference, but I figured that if anything the drivers side was supposed to be slightly higher and it was like that to account for a generic driver weight. I ended up getting the car corner balanced w/ my weight (180), so now there is definitely supposed to be difference, however it isn't really noticeable visually.
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04-10-2020, 11:23 AM | #3 |
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It’s not only the “drop height” that matters, but also the corner weighing.
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04-10-2020, 05:46 PM | #4 |
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^^This - Tommy - it may be worth taking your car into the shop to get a wheel aligment (if it needs it) and a corner balance. That will level out the corners - the ability to corner Balance is one of the major advantages of having a height adjustable suspension over fixed springs
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04-11-2020, 06:18 PM | #5 |
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The rears on mine are on even threads and drop. The fronts though have 1 or 2 thread difference for an even drop.
Not sure if it’s confirmed, but I believe there’s about 10mm difference that was intentionally set by bmw to account body weight and to keep the car balanced. This is true to the e46 and e9x M3 and defined as normal to the enthusiast crowd.
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04-18-2020, 10:39 AM | #6 |
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What's a "corner balance"? Setting equal ride heights with the driver sitting in the car? If you "corner weight" a car where the driver sits on one side, the drivers side will always be lower unless your adding ballast in the opposite rear corner. You can't get a road car corner weighted with equal ride heights without carrying a similar weight passenger.
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04-18-2020, 11:57 AM | #7 | |
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04-18-2020, 12:55 PM | #8 |
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Uneven drop
With coilover adjustable suspension it will ideally be adjusted using scales to corner balance the car. The condition where you want best performance is how car should be adjusted. Car fuel level should be set, car contents, and driver or driver and passenger weights. BMW recommends the ride height is adjusted or confirmed with the car properly weighted (tire pressure set, full tank, driver and passenger and some load) for ride heights to be correct. Scales cost about $1k or you can take your car to a race shop and pay them. The ride height doesn't change that much with BMW specified weighting so it is easier to use the unladen ride heights as reference. BMW values are in the TIS (see newtis). BMW sets both sides equal with different values front to rear. Heights are measured from inside of wheel rim to the fender with tape measure. Most stock cars I have checked will be within about 1/16" to 1/8". So just adjust your coilover to within 1/16 ride height, not shock threads, on each side and it will be within factory specifications. Use the factory dimensions to get the correct delta front to rear, then select your front ride height based on what you prefer for drop. Find as flat a surface as you can. Linoleum tiles can be used to level the car better. If you lift the car you must push on the car to bounce the suspension or results will be off. Best to drive the car on the setting spot. Record your settings, then after driving some miles check again.
When adjusting each corner changing one corner affects the other 3. Therefore correct adjustment is iterative and time consuming. With scales the cross weight can also be confirmed, which 50% cross weight will give the car the car the most equal right - left turning traction. Rubber suspension bushings tightened in unloaded condition can be a cause of significant variation from side to side. A leaking gas shock can also be a cause of variation. |
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04-18-2020, 01:01 PM | #9 | |
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04-19-2020, 07:28 AM | #10 |
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The contents of your gas tank weigh between 6 and 90 lbs so its best to corner rebalance/height adjust every few miles or half lap on track. Sure it's awkward but it's also absolutely critical if you want to truly enjoy the car.
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04-19-2020, 07:47 AM | #11 |
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04-19-2020, 08:43 AM | #12 |
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lol if you did that you would never even get to enjoy your car on the track because you would spend the whole day adjusting the ride hight.
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05-26-2020, 12:24 PM | #14 |
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Hey Tommy....Tried to PM you but your box is full, I think.
I'm thinking about going back to a factory spring set up from the KW HAS my car came with. The KW's are just too soft for me and I'm thinking of going to ZCP springs. I remember when you changed out your suspension that you had to remove your factory perches and wanted to know if you still had them and might be willing to sell them... Thanks, Tom
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05-26-2020, 12:32 PM | #15 | |
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But I suggest you swap with someone on the forum. Lots of people would be interested in paying you for your KWs in exchange for stock shocks |
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05-26-2020, 10:33 PM | #16 |
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I've also noticed on my '16 non-zcp that on factory springs my driver's side (RHD) is about 5mm lower. And would be lower once I'm in it.
Would this be a spring or shock issue? |
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05-30-2020, 12:25 PM | #18 |
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I've installed many coilovers over the years (36/46Ms) and never once, ever, were there threads identical on each side to achieve an even ride height.
This is normal.
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