Suspension Advice *Lowering Springs & Shocks*

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kish_635
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Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

Hi guys,

I'm looking to upgrade my current suspension set up in the near future by putting in some lowering springs and some new shocks.

I have a 88' 635csi highline motorsport edition and i'm debating whether to put H&R lowering springs (30mm lowering) or Fritz Bits lowering springs (20-25mm lowering).

I am aware that no springs were specifically made for the UK Highline model and instead people have just used the standard 635csi springs on them despite highlines being considerably heavier. After speaking with Fritz Bits i was informed that they have springs specifically made for the UK highline model to deal with the extra weight compared to a non-highline 635csi.

If anyone has used H&R springs or FritzBits springs could you please provide some insight / pictures.... I am edging towards the H&R springs with Bilstein B4 Shocks as I feel the Fritz Bits springs won't lead to a noticeable change in ride height.

(I am also aware that the overall drop with H&R springs is likely to be nearer to 35mm once the springs have settled).

Any advice / experiences with these springs is appreciated :D.

Cheers....
wattsmonkey
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

I've tried both, albeit on a chrome bumper six, and did not like either. M635 set up best thing I've found, especially with the US M6 arbs.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

Also, you'll need the shorter B8 shocks if you don't want the rears to fall off their perches.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
kish_635
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

wattsmonkey wrote:Also, you'll need the shorter B8 shocks if you don't want the rears to fall off their perches.
They will only fall off if the car is jacked up correct? :-k
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

That's right, but you'll need to make sure they are seated properly as car is lowered onto springs in the first place. B8s are just b6s with shorter travel, not sure why you want b4s, unless I've misunderstood.

I always imagined the motorsport cars having the yellow inverted b6 bilsteins, but don't know this for a fact.

Do have a look at previous posts on this topic, especially Brucey's thoughts on the angle of the front top mount with lower springs.

I've got some pictures of my old car with both fritz and h&r fitted, I'll see if I can find them.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by ron »

kish_635 wrote: They will only fall off if the car is jacked up correct?
Put your location in your profile as requested by admin.
They are ALWAYS rustier than you thought!!!!!!
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kish_635
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

ron wrote:
kish_635 wrote: They will only fall off if the car is jacked up correct?
Put your location in your profile as requested by admin.
Done.
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

wattsmonkey wrote:That's right, but you'll need to make sure they are seated properly as car is lowered onto springs in the first place. B8s are just b6s with shorter travel, not sure why you want b4s, unless I've misunderstood.

I always imagined the motorsport cars having the yellow inverted b6 bilsteins, but don't know this for a fact.

Do have a look at previous posts on this topic, especially Brucey's thoughts on the angle of the front top mount with lower springs.

I've got some pictures of my old car with both fritz and h&r fitted, I'll see if I can find them.
My car is a 635csi Highline (Not an M635). It is a Motorsport Edition as it was the end of line production in the UK where they made 181 cars in 3 limited colours.

With regards to Bilstein B4 I have been advised that they give a 'softer' ride quality and more closer to OEM springs. B6's on the other hand lead to a very firm ride?

Yes if you could send me pictures that would be great, cheers!
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

Thanks Kish,

I understand the Motorsport edition bit, with the LSD and cool colours, but I don't know what shocks these cars had as standard - I'm sure the springs are different from a standard Highline though?

Will dig out pics.
"Most of it necessary; all of it enjoyable." LJKS
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

A quick search on this site was quite helpful: have a look at this one, including advice on Highline versus chrome bumper height.

Almost brand new H&Rs UK only *SOLD*

Postby wattsmonkey » Wed Sep 21, 2011 7:46 pm
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
kish_635
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

wattsmonkey wrote:A quick search on this site was quite helpful: have a look at this one, including advice on Highline versus chrome bumper height.

Almost brand new H&Rs UK only *SOLD*

Postby wattsmonkey » Wed Sep 21, 2011 7:46 pm
Found it!
kish_635
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by kish_635 »

wattsmonkey wrote:I've tried both, albeit on a chrome bumper six, and did not like either. M635 set up best thing I've found, especially with the US M6 arbs.
What didn't you like about the Fritz Bits springs? they replicate the Eibach springs (which are no longer available to buy new right?)
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by 603racing »

I really like the H&R sport and Billy HD setup. Sporty, more firm that stock, a bit lower, but not to harsh of a ride. Improves steering wheel feedback as well.
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by ron »

kish_635 wrote:
wattsmonkey wrote:Also, you'll need the shorter B8 shocks if you don't want the rears to fall off their perches.
They will only fall off if the car is jacked up correct? :-k
.....or if you "take-off" over a humpback bridge!!
They are ALWAYS rustier than you thought!!!!!!
'85 M #228
'87 M #367
'88 High line.
'10 X5
‘84 Alfasud 1.5 ti
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by wattsmonkey »

kish_635 wrote:
wattsmonkey wrote:I've tried both, albeit on a chrome bumper six, and did not like either. M635 set up best thing I've found, especially with the US M6 arbs.
What didn't you like about the Fritz Bits springs? they replicate the Eibach springs (which are no longer available to buy new right?)
Don't misunderstand me here: this is just my subjective opinion and experience. They were too hard [goodbye BMW ride quality] and too low [goodbye rear of exhaust], plus concerns over topmount being angled all wrong and rear springs falling off their perch as I was using B6s on the rear at the time.

Also, I've never driven an Alpina B9, B10 or B anything, so perhaps I'm missing the point.

The M635 suspension on my cooking 635 was the best by a country mile, in my opinion. For what it's worth I'd tried standard stuff, Fritz, H&R, E28 M535i, Powerflex rear beam bushes, 17" staggered Alpinas, 17" Style 32s, 16" Style 8s, 16" Style 32s, 16" staggered Alpinas and 16" staggered Hartges before coming to the conclusion that - for me - M shocks and springs, standard rear beam bushes and 16" wheels were the best. I did enjoy finding this out, but it was an expensive research and development programme!

The Fritz springs aren't expensive - you could always give them a try, you're sure to find a buyer if you don't like them.
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by jps635 »

Here's my experience with H&R's. In the end I put the 3mm pads back in.

viewtopic.php?f=17&t=23852&hilit=h%26R+springs
'85 635csi JPS (RA2-66)
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Re: Suspension Advice *Lowering Springs & Shocks*

Post by Brucey »

ron wrote: Thu Aug 17, 2017 4:53 pm
kish_635 wrote:
wattsmonkey wrote:Also, you'll need the shorter B8 shocks if you don't want the rears to fall off their perches.
They will only fall off if the car is jacked up correct? :-k
.....or if you "take-off" over a humpback bridge!!
yup. I am bewildered by folk that carry on about 'performance' and so forth but clearly don't intend to drive their car with enough enthusiasm to get the wheels into 'full droop'.

There are a lot of 'suspension/wheel upgrades' to E24 that just result in the car being uncomfortable with little gain, and/or the car just being plain incompetent and/or dangerous on anything other than a billiard-table smooth surface, in a straight line.

The vast majority of aftermarket springs (IIRC including the eibach/fritz ones, and H&R etc etc) have a non-integer number of turns in them. This is OK at the rear but places the top hats at completely the wrong angle on the front suspension. So do E90 top hats and a whole bunch of other stuff. To put it into perspective I think that you would only be a little bit worse off if you just cut a turn or two out of your OEM springs; in fact this might be preferable.... :roll:

If you want to run short springs with long-travel shocks, in theory you can do it by using a 'helper spring'. This is a weak spring that runs coilbound (i.e. effectively as a spacer) all the time unless the suspension droops, in which case it extends and stops the main spring from dislocating.

If you are thinking coil-overs, it is almost certain that (for the road) the springs will have to extend down the strut below the height of the front tyre (else be short enough that they will dislocate with any standard damper insert). This means you can't run the tyre close to the strut (as per normal) which means you run with the wrong wheel offset and the steering is (feel-wise) basically crap.

For the track you can run very short travel shocks, stiff ARBS and stiff springs, and not worry about spring dislocation so much.

However on the road, racecar suspension is (literally) a PITA, and in wet/winter use you really need those gaiters to be fitted and working; without them the uprights tend to fill with water and the rear shocks just clap out. You can't sensibly fit boots/gaiters with coil-overs on an E24.

I've driven in a lot of different 6ers over the years and I've carried out a few experiments on my own, including wheels from 14" through to 18" and tyres up to 265mm or something.

18" wheels with sticky rubber went round corners very well but were noisy, tramlined horribly and (being a staggered set) you couldn't rotate the wheels to even out the wear. I got about 1/3 the usual mileage from a set of tyres before they were done because of this.

17" wheels are just about tolerable by comparison and I currently have a non-staggered set fitted. You can fit bigger brakes inside 17" wheels.

16" wheels are the best compromise for road use and are a good match to the M-tech/M635 suspension setup. Standard brakes fit inside most 16" wheels, and so do some upgraded ones.

15" wheels and tyres [225/60-15 as per E34 chassis fit on series 2 E24 cars BTW] are the best for low noise, fuel consumption, comfort and match the standard suspension well.

I agree with Rob about M635 suspension suiting the car well. It is quite purposeful without being stupid or uncomfortable. The rear ride height is adjustable using different perch settings and spacers etc with bilsteins fitted. The only thing is that the spring lengths for any given ride height will vary with the front weight of the car. Thus M635 front springs give a slightly higher ride height on a standard 635 than they do on M635 (the engine is heavier) and somewhere inbetween with a highline (which is typically a fair bit heavier than a chrome bumper car).

BTW you should fit bump stops that are consistent with the ride height; M635 rear ride height requires M-spec bump stops. At the front the bump stops are hidden inside a Bilstein strut insert, and you should fit shorter ones if the ride height is lower than the strut is intended for.

The reason this is important is that the term 'bump stop' is not accurate; IIRC the ETK refers to the external ones as 'supplementary springs' or something but they also provide compression damping as well as springing. They alter the roll stiffness (quite a strong effect on standard cars with standard ARBs) and consequently control the balance of the car when cornering hard; long bumpstops at the front of a lowered car make for a front end that is harsh normally and then will understeer on the limit, which is kind of exactly not what you want in a rear wheel drive car.

If you lower more than M635 spec, the toe and camber of all four wheels will probably go out badly enough that you will get bad tyre wear unless it is compensated for (difficult).

Think carefully what you want before buying a revised suspension setup for an E24; it is easy to end up with something that is basically rubbish.

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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