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      05-19-2019, 03:25 AM   #2333
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Quote:
Originally Posted by CanAutM3 View Post
Lowering a car very rarely results in more roll when cornering. It’s actually the opposite, where lowering lessens roll.

It's actually a fair bit more complicated than just the roll center. It also has to do with weight transfer. Lowering a car reduces the amount of weight transfer during cornering which improves total grip and reduces the forces that roll the car. For a car to roll more as a result of lowering, the effect of the roll center displacement relative to the center of gravity needs to be greater than the effect of the reduced weight transfer, and this is very rarely the case.

As for the effect of lowering on the handling balance (over/understeer), it mostly has to do with weight transfer and not with "making it softer". Lowering the rear results in less weight transfer on the rear axle during cornering, which in turn improves total grip on that axle that results in more understeer. This is why it is beneficial to lower a car, because it improves total grip. However, chaging the amount of roll on one axle relative to the other also impacts the handling balance, because if one axle rolls more, the other will suffer greater weight transfer because it is the one resisting the roll.
Lowering the roll centre softens the wheel rate and in racing categories where roll centre adjustability is permitted, raising pick up points on the lower control arms has a greater effect than altering ride height. Roll centre isn't adjustable on most cars and it isn't a tuning factor many use. More weight is transferred with a lower roll centre as the chassis pivots on a longer fulcrum like it easier to undo a bolt with a longer wrench than a short one.

Some cars used in production car racing with live axles and watts links attached to the diff, raising the rear ride height lowers the roll centre and doesn't have the same effect as a watts link mounted on the chassis or independent rear suspension cars when altering ride heights to improve handling balance. A 1/4" change in watts link height (roll centre) is all it takes sometimes to alter the handling balance between oversteer and understeer. In racing categories where controlled springs/shocks and ride heights are implemented, massaging suspension pick up points to alter roll centres and achieve a particular handling balance a driver prefers is a common cheater the tech guys often look out for and roll centre changes can have a surprising effect.

I'd be sure that roll centre is taken into account with BMW recommending a specific ride height when the car can be physically lowered a lot more.

Last edited by RevNev; 05-19-2019 at 03:32 AM..
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      05-31-2019, 07:23 PM   #2334
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Think I've decided to go for the MP-HAS option vs aftermarket coilover options

Question: Of those who have installed the MP-HAS suspension option, is anyone in northern NJ / NYC, where I might be able to see your car in person?......I'll also post in the NJ regional forum too

FYI: Go to post #296 and you'll see my mineral white M4 at a recent NJ meet
https://f80.bimmerpost.com/forums/sh...501627&page=14

Feel free to PM me...many thanks....
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      06-01-2019, 07:00 AM   #2335
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Quote:
Originally Posted by RevNev View Post
Lowering the roll centre softens the wheel rate and in racing categories where roll centre adjustability is permitted, raising pick up points on the lower control arms has a greater effect than altering ride height. Roll centre isn't adjustable on most cars and it isn't a tuning factor many use. More weight is transferred with a lower roll centre as the chassis pivots on a longer fulcrum like it easier to undo a bolt with a longer wrench than a short one.

Some cars used in production car racing with live axles and watts links attached to the diff, raising the rear ride height lowers the roll centre and doesn't have the same effect as a watts link mounted on the chassis or independent rear suspension cars when altering ride heights to improve handling balance. A 1/4" change in watts link height (roll centre) is all it takes sometimes to alter the handling balance between oversteer and understeer. In racing categories where controlled springs/shocks and ride heights are implemented, massaging suspension pick up points to alter roll centres and achieve a particular handling balance a driver prefers is a common cheater the tech guys often look out for and roll centre changes can have a surprising effect.

I'd be sure that roll centre is taken into account with BMW recommending a specific ride height when the car can be physically lowered a lot more.
It's important not to confuse roll and weight transfer. For example a car that has a fully rigid suspension would have zero roll under cornering but would still experience weight transfer. The amount of weight that is transferred as a result of the center of gravity moving about the roll center is negligible compared to the weight that is transfered as the result of the cornering forces.

I don't disagree about the effects of adjusting roll centers to tune the handling characteristics of a car. But this is not really relevent in this discussion since the suspension attachement points are not altered with lowering springs.
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Last edited by CanAutM3; 06-02-2019 at 05:40 AM..
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      06-03-2019, 09:05 AM   #2336
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Quote:
Originally Posted by CanAutM3 View Post
It's important not to confuse roll and weight transfer. For example a car that has a fully rigid suspension would have zero roll under cornering but would still experience weight transfer. The amount of weight that is transferred as a result of the center of gravity moving about the roll center is negligible compared to the weight that is transfered as the result of the cornering forces.

I don't disagree about the effects of adjusting roll centers to tune the handling characteristics of a car. But this is not really relevent in this discussion since the suspension attachement points are not altered with lowering springs.
Yes a rigid suspension car will experience weight transfer and break traction easier than with suspension movement, bit like Karts when they make the chassis flex abnormally to alter handling balance and gain traction.

Having never plotted the M4 suspension geometry to determine if this applies, however depending on the suspension geometry, lowing the ride height often lowers the roll centre more than it lowers the centre of gravity and the roll axis is the roll centre in relation to the centre of gravity. The closer the centre of gravity is to the roll centre, the less the car will roll at the same cornering force.

As an aside, I'm fitting a carbon roof to my M4 and removing the sunroof in a couple of weeks which effectively lowers the centre of gravity closer to the roll centre from removing weight from the highest point of the car. I'm interested to see if I can determine a difference in the way the car handles particularly when they fitted CS rear springs to the sunroof ZCP cars.
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      07-03-2019, 07:27 PM   #2337
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Bump

I installed my suspension today but did not install the dust boot in the front. Thoughts of going without it? Or should I suck it up and put them in?

The instructions did not say to put them in. But then I looked up photos - most people have it.
Thoughts?

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      07-03-2019, 08:18 PM   #2338
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Quote:
Originally Posted by Tommy L Garage View Post
Bump

I installed my suspension today but did not install the dust boot in the front. Thoughts of going without it? Or should I suck it up and put them in?

The instructions did not say to put them in. But then I looked up photos - most people have it.
Thoughts?

I say put them in. You "might" be able to just undo the top hat nut (and sway bar endlink) and push the shock down enough to clear the fender. Then put the boot on and put the shaft through the top hat again. That way, you don't have to undo all the strut tower braces etc.


Some tips:

- Be sure to put some protection on the fender so your shock shaft doesn't nick it.

- Undo the brake lines so they don't get stretched when you push down on the strut assembly.

- Lower the spring perch all the way down before undoing the top hat nut just in case there is tension on the spring.

Good luck!


Like this picture, but leave the top hat on the car.

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      07-03-2019, 08:20 PM   #2339
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Quote:
Originally Posted by x.shell View Post
I say put them in. You "might" be able to just loosen the top hat nut and pull the shock down enough to clear the fender. Then put the boot on and put the shaft through the top hat again.


Some tips:

- Be sure to put some protection on the fender so your shock shaft doesn't nick it.

- Undo the brake lines so they don't get stretched when you push down on the strut assembly.

- Lower the spring perch all the way down before undoing the top hat nut just in case there is tension on the spring.


Also, there is the possibility that you won't be able to clear the fender with this method. The OEM shock might be too long. On my aftermarket coilovers, I can do this method easily. Good luck!

Thank you. That’s what I thought. Gonna tackle it tonight. Silly mistake on my part.

I did the install myself today. Was fairly easy. And yes I’ll be able to lower the strut and angle it away. Thanks again!
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      07-03-2019, 10:16 PM   #2340
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Just did it. 45 for both sides. Not bad!
Also lowered the front a bit. Took it for a drive - I like it!!
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      07-03-2019, 10:28 PM   #2341
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Quote:
Originally Posted by Tommy L Garage View Post
Just did it. 45 for both sides. Not bad!
Also lowered the front a bit. Took it for a drive - I like it!!
Looks great!!
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      07-03-2019, 11:19 PM   #2342
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Quote:
Originally Posted by Tommy L Garage View Post
Just did it. 45 for both sides. Not bad!
Also lowered the front a bit. Took it for a drive - I like it!!
[img]https://i.ibb.co/6wCWFHy/91-BF3-B0-C...61248-D066.jpg[/img]
Good job on the install T. Enjoy in good health.

If you did make a DIY video of the install, let me know. I'll edit it in on the first post of this thread and the Suspension Master List thread.
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      07-04-2019, 05:20 AM   #2343
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Quote:
Originally Posted by x.shell View Post
Quote:
Originally Posted by Tommy L Garage View Post
Just did it. 45 for both sides. Not bad!
Also lowered the front a bit. Took it for a drive - I like it!!
[img]https://i.ibb.co/6wCWFHy/91-BF3-B0-C...61248-D066.jpg[/img]
Good job on the install T. Enjoy in good health.

If you did make a DIY video of the install, let me know. I'll edit it in on the first post of this thread and the Suspension Master List thread.
Yes thanks. I'll have it up in two weeks or so
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      07-04-2019, 06:33 AM   #2344
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Looking forward to the vid Tommy.
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      07-22-2019, 05:19 PM   #2345
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Has anyone made the jump from Eibach to MP HAS? If so, can you comment on how they compare, particularly in regards to ride quality?
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      08-12-2019, 12:08 PM   #2346
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I'm sure this has been asked before but it's a 108 page thread. Anyway, what is BMWs recommended lowering height and how long did you guys wait till you got balancing and alignment done after installation?
Thanks in advance
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      08-12-2019, 12:40 PM   #2347
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Quote:
Originally Posted by 330cibimmer View Post
I'm sure this has been asked before but it's a 108 page thread. Anyway, what is BMWs recommended lowering height and how long did you guys wait till you got balancing and alignment done after installation?
Thanks in advance
Check the install instructions.

It's a 25mm drop from stock I believe.

Instructions are on getbmwparts
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      08-12-2019, 01:27 PM   #2348
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Did anyone go through bmwpartspros.com or getbmwparts.com for this kit. Which is site do you recommend?
Thanks!
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      08-12-2019, 01:53 PM   #2349
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Quote:
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Quote:
Originally Posted by 330cibimmer View Post
I'm sure this has been asked before but it's a 108 page thread. Anyway, what is BMWs recommended lowering height and how long did you guys wait till you got balancing and alignment done after installation?
Thanks in advance
Check the install instructions.

It's a 25mm drop from stock I believe.

Instructions are on getbmwparts
Thanks. I just ordered it last week and waiting for it to arrive. I'll check if it comes with instructions and if not I'll check the website.
How long did you wait till balancing and alignment?
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      08-12-2019, 01:57 PM   #2350
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Quote:
Originally Posted by F80Xris View Post
Did anyone go through bmwpartspros.com or getbmwparts.com for this kit. Which is site do you recommend?
Thanks!
Quote:
Originally Posted by F80Xris View Post
Did anyone go through bmwpartspros.com or getbmwparts.com for this kit. Which is site do you recommend?
Thanks!
Both of them are great with pricing and will offer free shipping. If you live outside of their state then you don't get charged for tax
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      08-12-2019, 02:49 PM   #2351
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Quote:
Originally Posted by 330cibimmer View Post
Thanks. I just ordered it last week and waiting for it to arrive. I'll check if it comes with instructions and if not I'll check the website.
How long did you wait till balancing and alignment?
Same bro.

Mine arrives this week.

Gonna have it aligned on install, then do a more aggressive track alignment a week later.
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      08-13-2019, 05:28 PM   #2352
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Well I had a chance to install the kit today....wow boys and girls, this is the kit to have! Well worth every penny. I told myself when I bought my car that I wasn't going to touch the suspension (knew that wouldn't last), but wanted to lower the kit with something engineered for the car. At least so far, boy did it deliver.

The install kicked my ass - not because it was hard, but just because I dragged it out due to my extreme caution. I've been wrenching on cars for 20 years and I've never been so careful with suspension work. Even knowing what to look out for, I accidentally banged the sensors a few times, but no codes.

About the ride and handling - wow these things ride great. If the stock setup is a 5/10 in firmness, I would put these at a 6/10, but it is very controlled and compliant. I was really worried about the "lowered ride" of some spring setups, but this ain't it. Thrilled with the ride. Handling is obviously improved greatly, body roll diminished even in comfort mode. As a result, some of the numbness if the steering is gone too. As a bonus - my occasional strut clunk in the front end seems to be gone (I have this one stretch of road where I can make it clunk every time).

I set the ride height arbitrarily based on Tommy's video. Might have gone too low - measures about 26" from ground to fender on all corners - did I slam it a little too much? Might raise it up a little. The only weird part is the left front had to be adjusted down further than the right front to achieve the same height.

I'm going to drive it a few days to get the ride height dialed in, then send it in for alignment.
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      08-13-2019, 05:40 PM   #2353
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Quote:
Originally Posted by allinon72 View Post
Well I had a chance to install the kit today....wow boys and girls, this is the kit to have! Well worth every penny. I told myself when I bought my car that I wasn't going to touch the suspension (knew that wouldn't last), but wanted to lower the kit with something engineered for the car. At least so far, boy did it deliver.

The install kicked my ass - not because it was hard, but just because I dragged it out due to my extreme caution. I've been wrenching on cars for 20 years and I've never been so careful with suspension work. Even knowing what to look out for, I accidentally banged the sensors a few times, but no codes.

About the ride and handling - wow these things ride great. If the stock setup is a 5/10 in firmness, I would put these at a 6/10, but it is very controlled and compliant. I was really worried about the "lowered ride" of some spring setups, but this ain't it. Thrilled with the ride. Handling is obviously improved greatly, body roll diminished even in comfort mode. As a result, some of the numbness if the steering is gone too. As a bonus - my occasional strut clunk in the front end seems to be gone (I have this one stretch of road where I can make it clunk every time).

I set the ride height arbitrarily based on Tommy's video. Might have gone too low - measures about 26" from ground to fender on all corners - did I slam it a little too much? Might raise it up a little. The only weird part is the left front had to be adjusted down further than the right front to achieve the same height.

I'm going to drive it a few days to get the ride height dialed in, then send it in for alignment.
Looks great. I also had to lower one side more than the other to get the right heights, but it was within the recommended less than 5mm difference so did not worry about it. I have already tracked the car once and it did great. Enjoy.
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      08-15-2019, 06:35 AM   #2354
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Quote:
Originally Posted by literbikes View Post
Looks great. I also had to lower one side more than the other to get the right heights, but it was within the recommended less than 5mm difference so did not worry about it. I have already tracked the car once and it did great. Enjoy.
The right way of doing this is, after setting the desired ride height, to put the car on scales and fine tune the height until both diagonal weight sums are the same. This is called corner balancing and ensures balanced cornering in both directions.
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