Coilovers fitted....how to set the ride heights properly?

gippy · 10-11-2020, 02:59 PM

So....before my car goes in for alignment, i've been trying to get the ride heights sorted.

I'm aware that adjusting the RR for example would have an effect on the FL. Even so, the rears are reasonably equal with the same threads both sides.
I also understand that cross weight adjustments would mean bespoke settings - at the moment i just want to get the car riding the same height as stock, maybe just 10mm lower.

It all seems to be a mess. I've been measuring from top of the wheel arch to the wheel rim edge. The measurements vary all round, from 8.5cm to 9.5cm, i've got it to a level where it's roughly the same each corner, but what i don't understand is why my FL has had to be set sooooooo much lower than my FR....see the pics below. Doesn't make any sense to me. I have checked that both are sitting at the same level in the knuckle.

Any ideas what's going on here?

Below pics show how far down they are protruding past the knuckle - as you can see, pretty much bang on the same as you'd expect:

jackstrath · 10-11-2020, 04:56 PM

Sounds stupid but do all the numbers match (bar the left and right designation)

I personally set them normally the same across the axle. Leave it a week or so of daily driving.

Once everything is settled i take some sizes, I prefer to measure from the wheel arch to middle of the centre cap, this takes out any tyre wear ect ect. I dont tend to care much about the difference in threads showing ect ect but yours does seem more than id think there should be.

I wouldn’t be overly worried about it. I do have to ask the question why you went down the coil over route if your not looking to drop the height much if any, issue with coil overs the dampers are valved to normally work right about in the middle of the height setting, and anything out of that they arnt optimal for the springs and vice versa...

If your really wanting to get the most out of them id take it to a local motorsport suspension place and get them to corner weigh the car and set the ride height & alignment. There will be a trade off between height and ballance but seeing as im going to assume you just want the car to handle better it should be very slight ( IE your not going to the motorsport extream of having mass amounts of rake on the car)

therealm3 · 10-12-2020, 03:24 PM

I have noticed on several spring swaps that the front left seems to naturally sit higher on these cars. For example, my current set up has even height across the rear but the FL is about 1/4" higher than the FR. Lots of different speculation on the board as to why. In the end, I agree with the other post above. Go to a good shop and have them corner balance it if you are concerned about performance. But if you just want it to look level, then go for what you find you like best.

Watsey · 10-14-2020, 03:34 AM

Getting the ride heights even can be a pain.

Center Gravity (yes, spelled correctly) are in Atherstone which is only 40 minutes drive from Leicester. They do all my suspension work and I'd certainly recommend them to complete your install/set-up : ride heights, corner weighting and alignment.

gippy · 10-14-2020, 05:27 AM

Quote:

Originally Posted by Watsey

Getting the ride heights even can be a pain.

Center Gravity (yes, spelled correctly) are in Atherstone which is only 40 minutes drive from Leicester. They do all my suspension work and I'd certainly recommend them to complete your install/set-up : ride heights, corner weighting and alignment.

thanks, yeh i did email them but spat out my proverbial coffee when i saw the quote. I've found a local place only 5 miles from me that runs mx5 race cars that can do the alignment + corner weighting for £200-£250 region so giving them a shot, see how it goes.

other places around me are:
northampton motorsport
rogue motorsport
mg motorsport in ripley

all charge roughly the same, all can do corner weighting etc, but all about 30-40 miles from me.

gippy · 10-14-2020, 06:00 AM

Quote:

Originally Posted by jackstrath

Sounds stupid but do all the numbers match (bar the left and right designation)

I personally set them normally the same across the axle. Leave it a week or so of daily driving.

Once everything is settled i take some sizes, I prefer to measure from the wheel arch to middle of the centre cap, this takes out any tyre wear ect ect. I dont tend to care much about the difference in threads showing ect ect but yours does seem more than id think there should be.

I wouldn’t be overly worried about it. I do have to ask the question why you went down the coil over route if your not looking to drop the height much if any, issue with coil overs the dampers are valved to normally work right about in the middle of the height setting, and anything out of that they arnt optimal for the springs and vice versa...

If your really wanting to get the most out of them id take it to a local motorsport suspension place and get them to corner weigh the car and set the ride height & alignment. There will be a trade off between height and ballance but seeing as im going to assume you just want the car to handle better it should be very slight ( IE your not going to the motorsport extream of having mass amounts of rake on the car)

coilovers - just because they were in budget and the stock Msport suspension is a sick joke, i set myself a £1.5k budget for suspension, and the B14 kit was only £850 odd. It left me spare change for an ARB kit + bushes upgrade.

measurements - it's currently on (in cm)
FL 8.8 FR 8.9
RL 8.7 RR 8.9

stock rideheights were
F 9.9
R 10.2

rear tyres are maybe 1.5-2mm more worn than fronts so in that respect i've taken out the rake...and therefore presumably shifted the weight balance rearward.

yes originally i wasn't fussed about lowering but now that (accidentally) i lowered the car by 10mm i actually like the aesthetics now! so i'm happy to keep it there without it being impractical.

it's the fact that they're all within 2mm of each other which is why i'm concerned about that FL difference...
its going to a specialist place tomorrow, i'm excited to see the data and weightings!

Watsey · 10-14-2020, 01:55 PM

Quote:

Originally Posted by gippy

thanks, yeh i did email them but spat out my proverbial coffee when i saw the quote. I've found a local place only 5 miles from me that runs mx5 race cars that can do the alignment + corner weighting for £200-£250 region so giving them a shot, see how it goes.

other places around me are:
northampton motorsport
rogue motorsport
mg motorsport in ripley

all charge roughly the same, all can do corner weighting etc, but all about 30-40 miles from me.

Well, "you pays your money..." as the phrase goes.

With such a difference in the preloads (as per your photos) you may well get some uneven ride/handling characteristics in the car. It's one of the reasons that I opted for Ohlins - the damper bodies have a threaded collar which allows the ride height to be easily and precisely adjusted independently of the preload.

Preload should be set first (according to the manufacturer's recommendations), then adjust the ride height by moving the damper bodies in the hub carrier.

It looks like you're trying to set the damper bodies at a constant height (relative to the hub carrier) first, and then adjusting the ride height by using the spring preload adjusters. This is not the correct method.

Logicoeur · 10-14-2020, 06:22 PM

Quote:

Originally Posted by Watsey

Quote:

Originally Posted by gippy

thanks, yeh i did email them but spat out my proverbial coffee when i saw the quote. I've found a local place only 5 miles from me that runs mx5 race cars that can do the alignment + corner weighting for £200-£250 region so giving them a shot, see how it goes.

other places around me are:
northampton motorsport
rogue motorsport
mg motorsport in ripley

all charge roughly the same, all can do corner weighting etc, but all about 30-40 miles from me.

Well, "you pays your money..." as the phrase goes.

With such a difference in the preloads (as per your photos) you may well get some uneven ride/handling characteristics in the car. It's one of the reasons that I opted for Ohlins - the damper bodies have a threaded collar which allows the ride height to be easily and precisely adjusted independently of the preload.

Preload should be set first (according to the manufacturer's recommendations), then adjust the ride height by moving the damper bodies in the hub carrier.

It looks like you're trying to set the damper bodies at a constant height (relative to the hub carrier) first, and then adjusting the ride height by using the spring preload adjusters. This is not the correct method.

He has B14 coilovers I believe. Those adjust height and preload with the same collar.

Watsey · 10-15-2020, 09:13 AM

These YouTube videos both relate to adjusting the ride height of coilovers. Neither relate to BMW, and both vehicles are using coilovers which have threaded collars on the lower damper bodies (as does Ohlins R&T), BUT, there are two key messages :

Spring preload : 'set and forget' (i.e. leave it alone once each spring preload has been set correctly).
Adjust the ride height by moving the lower damper body relative to the wheel hub carrier.

Adjusting ride height by adjusting the spring preload is NOT the way to go.

FaRKle! · 10-15-2020, 10:53 AM

Quote:

Originally Posted by Watsey

Adjusting ride height by adjusting the spring preload is NOT the way to go.

Preload doesn't change when you adjust the spring perch on this platform unless the perch is positioned so high that the suspension never compresses more than full droop.

There was just a discussion about this in the past two weeks on this in the F8x forum.

Watsey · 10-15-2020, 12:51 PM

There are several different things being discussed in that thread and in the attached installation guides / web articles.

For McPherson struts, spring preload is exactly that - a preloaded spring. This is set when the damper is at its fully extended range, typically after the strut assembly has been built but prior to fitting to the vehicle - if fitted to the vehicle, we let the suspension go into full droop.

The damper manufacturer should publish its recommended preload for each specific vehicle, and it's typically expressed in mm compression of the spring from 'slack' i.e. zero load. This is the state when the lower collar is just snug to the spring, i.e. the collar stops rotating under finger pressure, but no further rotation of the collar has been applied.

If the preload isn't set before the weight of the vehicle is applied through the strut, then it's guesswork. Raising the lower spring collar would simply jack-up the corner of the car and would keep going until the damper hit its internal stops i.e. its fully extended position. It would then be possible to apply an additional loading to the already loaded spring, but the starting point is incorrect as the spring is already partially compressed - we would be post-loading the spring, not preloading it. The ride height of the vehicle would also have been ruined.

As one of the articles makes clear, preload and spring rate are not related. Although preload places the spring into a pre-compressed state, it's rate of deflection rate won't change once the preload has been overcome. If a spring with a 200lb/in rate is preloaded by 1" and a 200lb weight is placed on it, the spring won't compress. Add a further 200lb (a total of 400lb) and it will compress by 1", assuming it's a linear rate spring. Place a 400lb weight on a 200lb/in spring which has not been preloaded, and the spring will compress by 2".

Obviously this doesn't apply to the rear suspension on the F3X because the springs are inboard of the damper. It's impossible to have preload in the true sense.

For those dampers/struts that have them, independent mechanisms for achieving preload adjustment and ride height adjustment exist for a good reason. If Bilstein dampers require a preload, and the OP had correctly set the preload, and the OP then used the lower spring collars to adjust the ride height (his photos show quite a big difference in the height of the lower spring collars), the correct preload adjustment has been lost, the ride may be compromised, and there's a risk of 'spring blocking' under large primary ride inputs.

gippy · 10-15-2020, 04:07 PM

Quote:

Originally Posted by Watsey

For those dampers/struts that have them, independent mechanisms for achieving preload adjustment and ride height adjustment exist for a good reason. If Bilstein dampers require a preload, and the OP had correctly set the preload, and the OP then used the lower spring collars to adjust the ride height (his photos show quite a big difference in the height of the lower spring collars), the correct preload adjustment has been lost, the ride may be compromised, and there's a risk of 'spring blocking' under large primary ride inputs.

On those b14 struts there was quite a wide range between the collar being snug against an unloaded spring, and the spring then being reasonably compressed. Id' already set them with some preload before installing them, i'd actually gone ultra conservative because i'd read/heard in videos that it's easier to adjust down than up.
So i initially set all the collars high i.e. with all the springs reasonably compressed (and certainly higher than where they were set out the box) so, when i dropped the car to the ground for the first time, it was sat a fair bit higher than stock.
Then i started adjusting down.

you're absolutely right though and i totally get what you're saying (see below).

Anyway it's all sorted and perfect, my FL was a bit low when taking measurements of the ride height in a more logical way i.e. from the bottom sill of the car around the jacking point to the ground.

EDIT - i just found this nugget of info on the bilstein website..........i just need to find out what that identified bilstein range is, where the spring is already under some specified preload. (edit...found it)

gippy · 10-15-2020, 04:46 PM

Watsey

i should have read the instructions more carefully

in conclusion, as long as my collar is set somewhere between 215mm to 235mm from spring plate to the kuckle bolt, i'm good

Watsey · 10-16-2020, 03:32 AM

gippy guys don't read instructions, but sometimes it's better if we do

The table which you've posted is (obviously) key.

Glad to hear that it's all sorted and you're happy with how the car is sitting

10-11-2020, 02:59 PM	#1
gippy Lieutenant 230 Rep 525 Posts Drives: F32 440i, pre-LCI, w/MPPSK Join Date: May 2018 Location: UK iTrader: (0)	Coilovers fitted....how to set the ride heights properly? So....before my car goes in for alignment, i've been trying to get the ride heights sorted. I'm aware that adjusting the RR for example would have an effect on the FL. Even so, the rears are reasonably equal with the same threads both sides. I also understand that cross weight adjustments would mean bespoke settings - at the moment i just want to get the car riding the same height as stock, maybe just 10mm lower. It all seems to be a mess. I've been measuring from top of the wheel arch to the wheel rim edge. The measurements vary all round, from 8.5cm to 9.5cm, i've got it to a level where it's roughly the same each corner, but what i don't understand is why my FL has had to be set sooooooo much lower than my FR....see the pics below. Doesn't make any sense to me. I have checked that both are sitting at the same level in the knuckle. Any ideas what's going on here? Below pics show how far down they are protruding past the knuckle - as you can see, pretty much bang on the same as you'd expect:
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10-11-2020, 04:56 PM	#2
jackstrath Major 659 Rep 1,239 Posts Drives: 16' F31 340i & 03' Focus RS Join Date: Aug 2014 Location: Aberdeen iTrader: (0)	Sounds stupid but do all the numbers match (bar the left and right designation) I personally set them normally the same across the axle. Leave it a week or so of daily driving. Once everything is settled i take some sizes, I prefer to measure from the wheel arch to middle of the centre cap, this takes out any tyre wear ect ect. I dont tend to care much about the difference in threads showing ect ect but yours does seem more than id think there should be. I wouldn’t be overly worried about it. I do have to ask the question why you went down the coil over route if your not looking to drop the height much if any, issue with coil overs the dampers are valved to normally work right about in the middle of the height setting, and anything out of that they arnt optimal for the springs and vice versa... If your really wanting to get the most out of them id take it to a local motorsport suspension place and get them to corner weigh the car and set the ride height & alignment. There will be a trade off between height and ballance but seeing as im going to assume you just want the car to handle better it should be very slight ( IE your not going to the motorsport extream of having mass amounts of rake on the car)
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10-12-2020, 03:24 PM	#3
therealm3 Lieutenant Colonel 630 Rep 1,649 Posts Drives: F30 340 MSport Join Date: Aug 2006 Location: CA, USA iTrader: (7)	I have noticed on several spring swaps that the front left seems to naturally sit higher on these cars. For example, my current set up has even height across the rear but the FL is about 1/4" higher than the FR. Lots of different speculation on the board as to why. In the end, I agree with the other post above. Go to a good shop and have them corner balance it if you are concerned about performance. But if you just want it to look level, then go for what you find you like best.
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10-14-2020, 03:34 AM	#4
Watsey Major General 6404 Rep 8,492 Posts Drives: F31 330D sDrive M Sport Join Date: Jun 2015 Location: On sabbatical. iTrader: (1)	Getting the ride heights even can be a pain. Center Gravity (yes, spelled correctly) are in Atherstone which is only 40 minutes drive from Leicester. They do all my suspension work and I'd certainly recommend them to complete your install/set-up : ride heights, corner weighting and alignment. __________________ Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-15-2020, 09:13 AM	#9
Watsey Major General 6404 Rep 8,492 Posts Drives: F31 330D sDrive M Sport Join Date: Jun 2015 Location: On sabbatical. iTrader: (1)	These YouTube videos both relate to adjusting the ride height of coilovers. Neither relate to BMW, and both vehicles are using coilovers which have threaded collars on the lower damper bodies (as does Ohlins R&T), BUT, there are two key messages : Spring preload : 'set and forget' (i.e. leave it alone once each spring preload has been set correctly). Adjust the ride height by moving the lower damper body relative to the wheel hub carrier. Adjusting ride height by adjusting the spring preload is NOT the way to go. __________________ Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-15-2020, 12:51 PM	#11
Watsey Major General 6404 Rep 8,492 Posts Drives: F31 330D sDrive M Sport Join Date: Jun 2015 Location: On sabbatical. iTrader: (1)	There are several different things being discussed in that thread and in the attached installation guides / web articles. For McPherson struts, spring preload is exactly that - a preloaded spring. This is set when the damper is at its fully extended range, typically after the strut assembly has been built but prior to fitting to the vehicle - if fitted to the vehicle, we let the suspension go into full droop. The damper manufacturer should publish its recommended preload for each specific vehicle, and it's typically expressed in mm compression of the spring from 'slack' i.e. zero load. This is the state when the lower collar is just snug to the spring, i.e. the collar stops rotating under finger pressure, but no further rotation of the collar has been applied. If the preload isn't set before the weight of the vehicle is applied through the strut, then it's guesswork. Raising the lower spring collar would simply jack-up the corner of the car and would keep going until the damper hit its internal stops i.e. its fully extended position. It would then be possible to apply an additional loading to the already loaded spring, but the starting point is incorrect as the spring is already partially compressed - we would be post-loading the spring, not preloading it. The ride height of the vehicle would also have been ruined. As one of the articles makes clear, preload and spring rate are not related. Although preload places the spring into a pre-compressed state, it's rate of deflection rate won't change once the preload has been overcome. If a spring with a 200lb/in rate is preloaded by 1" and a 200lb weight is placed on it, the spring won't compress. Add a further 200lb (a total of 400lb) and it will compress by 1", assuming it's a linear rate spring. Place a 400lb weight on a 200lb/in spring which has not been preloaded, and the spring will compress by 2". Obviously this doesn't apply to the rear suspension on the F3X because the springs are inboard of the damper. It's impossible to have preload in the true sense. For those dampers/struts that have them, independent mechanisms for achieving preload adjustment and ride height adjustment exist for a good reason. If Bilstein dampers require a preload, and the OP had correctly set the preload, and the OP then used the lower spring collars to adjust the ride height (his photos show quite a big difference in the height of the lower spring collars), the correct preload adjustment has been lost, the ride may be compromised, and there's a risk of 'spring blocking' under large primary ride inputs. __________________ Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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10-15-2020, 04:46 PM	#13
gippy Lieutenant 230 Rep 525 Posts Drives: F32 440i, pre-LCI, w/MPPSK Join Date: May 2018 Location: UK iTrader: (0)	Watsey i should have read the instructions more carefully in conclusion, as long as my collar is set somewhere between 215mm to 235mm from spring plate to the kuckle bolt, i'm good
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10-16-2020, 03:32 AM	#14
Watsey Major General 6404 Rep 8,492 Posts Drives: F31 330D sDrive M Sport Join Date: Jun 2015 Location: On sabbatical. iTrader: (1)	gippy guys don't read instructions, but sometimes it's better if we do The table which you've posted is (obviously) key. Glad to hear that it's all sorted and you're happy with how the car is sitting __________________ Current : F31 330sD, remapped, Ohlins Road & Track, Millway camber plates, Quaife LSD, Stoptech brakes + Pagid RSL1 pads all round, Weichers front strut brace, Eibach front & rear anti-roll bars, Michelin MP4S.
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