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Low rear end when loaded - 147

4K views 39 replies 6 participants last post by  tishobg 
#1 ·
Hello, me and my car have been having some problems with the rear suspension.
It is sitting on KW sports springs which are -30mm. Wheel to wheelarch is about 5-6cm.

When two adults hop in the back, that gap is removed leaving no more than 1cm between the wheel and wheelarch. The front is fine.

Any ideas what could be causing this? I have a suspicion for crushed shock top mounts, but can they really cause that?

As per suspension noises, car creaks like crazy on the rear over speed bumps or dropping from a curb, whenever there is A big vertical movement of the wheel. That noise is gone when loaded but then you hear a knocking noise, as if I’m on the bump stops.

Any input will be appreciated, have a good weekend!
 
#2 ·
The bumping could very well be rear strut top mounts. I have a suspicion they often fail after removing the rear struts. Look at strut top locating plates; there should be a gap between plates and strut turrets. Jack rear of car up; if gap disappears then mounts need replacing. Alternatively, get someone to bounce rear of car. The rubberised locating plate on rear strut top should stay steady. If it moves, then it's time for strut mountings.

I was not aware KW did lowering springs. I thought they only ever did coilovers. I have Eibach Pro Kit springs on both 156s and there is less suspension sag than standard. I also suggest you remove the springs from the struts to very carefully inspect the spring perches as these pans have a tendency to rust.

The rear suspension is quite simple and generally trouble free. I think it is just care is needed as these cars are a bit older now but spring perches and top mountings are the 2 main things which cause problems. Finally, check the rear springs ate located properly. There is not much pre-load on the springs and less with lowering springs. It may be simply a dislocation fault.
 
#3 ·
Thanks for the reply! My strut mounts are shot I’m certain as they began making noises after loading my car for a long period of time. But can they actually cause a more prone to sagging rear?

The squating is my main concern. Car has been like that ever since I bought it (about 3 years). Rear just seems softer when bouncing it compared to the front. Rear has more space between tire and arch than the front but I presumed that this is normal. Same springs. They are ST lowering springs which is some sub brand of KW as far as I understand.

I am considering Eibach Pro Kit as well, but am not really keen on spending the money if mine are fine.
 

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#4 ·
The rear strut tops will cause bumping but not the sagging when loaded. My main concern is the struts themselves as the pans the bottom of the springs sit on can corrode. That is more an issue in northern Europe though and I'd be a bit surprised (unless my knowledge of Bulgarian climate is wrong) if your car has this issue. They need careful checking (remove from car and stripped down, ideally). It was only when changing to Eibach Pro Kit springs that I noticed the rear struts on my JTS were corroded. They looked fine on the car.

I checked ST suspension website. It eventually took me to springs for a Hyundai Coupe after inputting "Alfa 147"! The picture looks like it may fit but I wonder...

Look at your rear springs. All aftermarket sport springs (for original struts) have 6.5 coils. The bottom 2 coils sit on each other. As the suspension compresses, more of the spring touches the dead coils at the bottom. This is what gives springs the progressive characteristic (rising spring rate due to compression). Are your springs like this? (Factory springs are 4.5 coils with no coils touching each other so are linear rate springs). I just want to ensure that it is not a spring design issue.
 
#5 ·
Generally, Eibach springs are highly thought of and I suppose so are H&R (specifically for our cars).

What I've found by looking at the detailed Eibach spring specifications is that Eibach Pro Kit and Sportline springs are the same spring wire for all our cars, regardless of engine or model. It is the free length the spring is wound to which is the only difference. (Pro kit and Sportline have same spring rating and hence ride.) Due to occasional comments about JTD front springs being too soft and causing too much pitching, it is clear these springs are really optimized or designed for the 4 cylinder petrol engines. I don't know if H&R are much better but I think they are a slightly firmer spring so are likely better suited to the heavier engines. Anyway, this shows each spring is not individually developed but tailored from a specific base within a model range(s). That may also be why certain models or engine versions work better than others in a manufacturers spring range. It may be why your rear springs seem to sag when loaded but I wish to know if they are progressive or linear and if your rear struts are corroded because if so, a spring perch is likely to completely fail very soon and possibly dangerously.
 
#6 · (Edited)
I'll go down to the car in a sec and update with photos!

P.S. I have the actual box of the springs themselves - it says KW FS 30/30 Spring set for Alfa Romeo 147 GTA + JTD, Type 937 - so i'm certain they are for my car - not certain of their characteristics though.

EDIT: Pictures uploaded. Left and right rear springs. They seemed a bit soft to me - I can squeeze them by hand and they flex a bit.
 

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#7 ·
Springs do not look dislocated and are of progressive type. I'd check they are not broken after jacking up the car though as I was not completely happy with the coil spacing.

Here is a link to Eibach technical;
PKW

If you change the springs, Eibach Pro Kit rear springs for the 147 benzine 4 cylinder are F11 10 001 01 HA part number.
They are part of the E10 10 001 01 22 Pro Kit set.
They are also available individually on the German www.autodoc.co.uk website. They look black in the picture but all my Pro Kit springs are red. They are listed at £48.63 GBP each. You can get new strut top mountings from them too. Decent brands are Febi or the ZF owned Sachs or Boge.

I have had over 120kg in the boot of my 156 with the Pro Kit and the ride height was reduced very minimally and there was no rubbing or bumping. Indeed, the ride height reduction was less than with factory springs (as it should be with progressive springs).
 
#8 ·
I have heard simular input from other Eibach Pro Kit users. The amount of ride height reduction I experience is about 4-5cm with ~150kg in the back seat. About 20-30 liters of fuel. To me it seems to be too much and as there isn't anything else affecting ride height, I am starting to believe my springs just aren't up to the task. Either softened up or worse - they are lowering springs which don't stiffen the ride, which is very compliant I'll be honest.
 
#9 ·
Hello all, just decided to upload some photos. 1st photo is unloaded, 2nd photo is with 130kg in the back seats. Do you think that’s a lot of “sagging”?
 

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#10 ·
It doesn't look bad. Obviously there has to be a ride height reduction but I don't think it is excessive.

I went back over the whole post an the issue seems to be some kind of groaning sound, presumably whilst the suspension is moving. What I suggest is slackening the bottom hub bolt which goes through the transverse arms. Ideally rotate the bolt a little and then tighten the nut whilst the wheels are supporting the weight of the car (car on DIY ramps pr driven onto a garage 4 post ramp- not when supported by a jack or axle stands). You could spray some silicone lubricant around the bushes whilst the nut is loosened also. Whilst at it, spray the rear anti roll bar D bushes with silicone.

If that does not make it quiet, you may also need to slacken the rear transverse arm inner bolts and again, spray with lubricant but be careful not to upset the rear tracking adjustment.

I suggest this as I wonder if the reduced ride height is causing the transverse arm silent-block bushes to make a noise. Silent-block bushes should be tightened in place when they are in their natural position (weight on wheels) and it may be that things were simply done in the wrong order.

If the car has any polyurethane bushes on it, these can make noise and I've found that to keep them quiet, my both 156s need a twice yearly spray of silicone lubricant to keep them completely quiet. I have polyurethane bushes for the front ARB and rear hub in the JTS. The TS has poly bushes in top wishbones at the front and both cars begin making a noise if left much more than 6 months between being sprayed with silicone.
 
#13 ·
Thanks for the suggestions. Bushing have been liberally sprayed with silicone grease a few times now with no positive effect in terms of the terrible noise at the back. The only thing which removes it is loading the car at the back, thus compressing the suspension. Once I do that, I can hear muted thuds from the rear. That’s why top mounts are my best bet.

Car has no poly bushes and your suggestion about the transverse arms is very good - as I don’t have access to a ramp or even a driveway, I’ll ask my mechanic to follow your tip and readjust them.

I’m going in for supposedly rear top mounts, I’ll share the end result. The noise from the rear is so loud these days, I’ll be reborn once fixed.
 
#15 ·
In utter desperation;
As your mechanic will be looking at it, his trained ear should be able to identify what is making the noise. If the car is on a 4 post ramp (weight on wheels) perhaps someone else can apply force to make the suspension move up and down. If so, listening with a sonoscope or mechanic's stethoscope should identify the source quite easily.

The trouble with trying to diagnose from text is we don't get to hear what kind of noise is produced so we an only use best guess from descriptions which makes this sort of thing the hardest of all to try to offer help for. That said, hopefully it will be quite was for an experienced mechanic. I hope it is resolved quickly and easily.
 
#26 · (Edited)
Fruity, hello again. Hope you’re still here hehe. Visited my mechanic who unfortunately wasn’t able to directly pin point the noise, but he suspects it’s the struts themselves. He said there isn’t any movement in the strut mount. I captured a small video of the noise I experience on the rear of the vehicle:

https://streamable.com/cc1c8

Noise is lessened with people in the back, but a knock which happens on even the smallest imperfections replaces it.

What do you think?
 
#16 · (Edited)
I have exactly the same sagging problem in my GT JTD. It has enough clearance when empty, but as soon as I load even two kids in the back, the suspension will sag to such an extent that just about any bump in the road will cause the tyre to touch on the bodywork. I have the standard springs, with 225/45R18 tyres, also standard AFAIK. I suppose new springs or retempering of the old springs would be my best solution? Or has anyone tried an auxiliary spring the works in conjunction with the existing ones? Such as these
 
#17 ·
@Vortexe;
As per John's explanation, sagging rear springs don't change the rating, they just lower the ride height so unless the rear is too low when the car is unloaded it won't be springs.

The most obvious thing is your tyres are too big. You should have 225/40R18 tyres and that is no doubt the reason for the fouling. Lowering springs are available to reduce rear ride height but 50mm and that's before adjustable coilovers so I doubt it is simply spring sag.
 
#18 ·
Thanks for the answer.
I have to say I can't quite agree with you.
As the springs get old they likely form some micro cracks in the crystal structure, so over time it seems that the spring constant will change (hence the sag when loaded) compared to when they were new.
Obviously loading the springs won't change their rating. It's called a spring constant for a reason... :glasses:
Re the tyres, they width is the same but the tyre height is then slightly increased. (I bought the car with these) I do understand the reasoning, as the road surface in SA tends not to be the greatest sometimes... That may cause some slightly sooner fouling (if you get what I'm trying to say) vs the 40 profile. But the distance the scuff marks show up in the sidewall is more than halfway under the middle of said sidewall. And it happens more on the left hand side...
So my question was actually more aimed at knowing the spring rate is too low, and wondering if there's any way of fixing that. I'm not keen on rubber spacers, as that makers the load distribution in the coils uneven, just asking for a spring failure.
So it's new springs, or some sort of aux spring or possibly a spacer between the spring and the cup.
eish...
 
#24 ·
Thanks for the answer.
I have to say I can't quite agree with you.
As the springs get old they likely form some micro cracks in the crystal structure, so over time it seems that the spring constant will change (hence the sag when loaded) compared to when they were new.
Obviously loading the springs won't change their rating. It's called a spring constant for a reason... :glasses:
I agree that a crack will soften the spring, because it changes the physical dimension of the spring (the coil wire is effectively thinner where the crack exists). But, a crack is a stress riser. If the spring has started to crack it won't be long before it fractures completely.

All spings will eventually sag given enough repeated deflections, at least to some very small degree. The difference between a 'good' spring and a 'bad' spring (of identical physical shape / dimension) will be the quality / suitability of the material (and heat treatment if the particular steel requires it, not all do), but the rates will be the same.

With two identically dimensioned / rated springs, one a good quality spring and the other not so good, the 'good' spring will last longer before the physical dimension changes (spring sags), the 'bad' spring will sag sooner, possibly much sooner.

Regards,
John.
 
#19 ·
Not necessarily. Firstly, are your wheels original and NOT using spacers? Tyres are also nominal sizes but also the shape of a particular tyre can make the difference, also.

The rear springs themselves are very reliable and I've never known a rear OE spring to fail (sag or break) but it is not impossible. Often the rear spring support can corrode and that may lead to a reduction in spring height even before the spring perch touches the tyre. I'd be surprised if the Mediterranean-like climate of South Africa cause caused corrosion here but it is worth checking.

If you do end up changing springs, beware that there are European discount sites offering springs listed for all models as a blanket. In other words, rationalisation has caused a single spring to be offered for 147s, both 3 and 5 door, 156, 156 Sportwagon and the GT all as a single part number. AFAIK, the replacement aftermarket springs are now focused for a 156 saloon/sedan with standard suspension (not factory sports) so it is likely a spring from a spring manufacturer will result in a change of ride height. Some specialists still have the correct springs and obviously they can be made but I think that it is probably not the springs causing the issue.

Modification should not be necessary and is more often than not simply a way to treat the effects of an underlying problem. Check the car thoroughly and provide rode height measurements (wheel centre to 12 o'clock position of wheelarch).
 
#25 ·
Often the rear spring support can corrode
There is a rubber diaphram incorporated into the lower spring seat (the rubber part fitted between the steel spring seat and the spring). This diaphram fits quite closely around the damper tube (which passes through a hole in the diaphram). This creates an enclosed hollow space below the diaphram and above the steel of the spring seat. This space probably entraps moisture, possibly salty depending on where you live.

This moisture probably mixes with accumulated road gunk / dirt and forms mud (which also may block the small drain holes in the metal part of the spring seat). In a cold climate this mud may well remain wet for extended periods of time. This would be especially bad if the mud were also salty. Because the 'cavity' is fairly enclosed, it isn't well ventilated and any crap which gets in probably finds it hard to get out. Even pointing a hose at it probably wouldn't dislodge much mud / dirt / crap.

It might be a good idea to substantially enlarge the hole in the diaphram, or cut the diaphram away completely, to ventilate the accumulated mud etc...

Regards,
John.
 
#20 ·
Thanks for the input, Fruity.
The climate here is much drier than Mediterranean, so corrosion is generally not much of an issue.
Ok, so Measurements:
I checked all the wheels, and the static measurements are identical (within close tolerances of a few mm)
Height from centre to arch = 380mm
Height from tyre surface to arch = 50mm
The car stands perfectly flat, no stinkbugging or sagging in the rear.
The images attached (hopefully) will show what it looks like (Yes, she needs a wash). The rub marks are clearly visible, but only on the left.
 

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#21 ·
Yes, the car does sit nicely. The figure given is what it should be AFAIK. There are always slight production tolerances hence uneven rubbing side to side.

I didn't know the GT was so close for clearance but it obviously is. In your case it is possibly a combination of an oversized tyre which is not helped with the Michelin PS4 (or earlier). They are broad, square shouldered tyres which grip and handle very well but are physically big for each nominal size.

I cannot say whether the correct size would give clearance or whether you may have to consider something a little less sporting also which would not have such a massive rim protector overhang as your Michelin Pilots currently have.
 
#22 ·
Your idea of a spacer at the bottom of the spring is something I suggested a while back for people who wanted to lower their 156 Sportwagons. The aftermarket lowering springs are the same for saloon and Sportwagon versions so the Sportwagon sags at the rear.

My idea is to make a spacer from fibreglass matt/paste which sits between the rubber diaphragm and the bottom of the spring. If plastic bags, for instance, were used, they could be peeled off when it is set and as long as there was some kind of inner lip, the spring should not dislocate but it means the rear ride height will be increased. Obviously it would also need small drainage channels filed out of the bottom to aid drainage.
 
#27 ·
That sounds like something I loose. Its not a bumping sound like a strut top or a metallic rattle like an ARB link. It's really difficult to say and I don't want to suggest the wrong thing. Just be really sure the bushes at either end of the trailing arms are good. The front bush into the floor is a void/compliance bush. It is meant to have movement. The rear bush into the hub assembly should have no movement. OE bushes are a pain to fit so I used Strongflex PU bushes. It is difficult to check these bushes due to lack of lever points but no movement is what is desired. Any movement- change the bush.

There was a thread on here a few weeks ago about a member who was experiencing rear suspension noise but I think that turned out to be a mounting.

If it is the rear struts then ideally you should use an aftermarket sport strut like Koni Str.T. It seems struts for factory sport suspension are no longer available from outwith specialist supply.
 
#28 ·
Exactly. To be it sounds like something is loose, at first I thought my springs aren't compressed enough and are just bouncing around, but I highly doubt that's even possible.

Second video which shows the noise once more - a bit exaggerated, but still. Goes away intermittently or at least mutes itself whenever the car is soaked with water. It rained last 2 days ago, but the sound is still much less than usual. Weird!

I'll check all bushes but the shop did change most of them without making a difference. Truly odd issue and going directly for expensive items such as struts is definitely not my forté.
 
#29 · (Edited)
@Fruity - an old thread, but still finally got some information about the KW springs I have, in case there is another person out there with the same set. The spring set has the following code: KW 250 15 023 and is made by Eibach - It is a Pro Kit in yellow disguish. I have attached their spec sheet - absolutely identical to Eibach, even says Eibach on manufacturer.

Picture of the stance has been added. Furthermore, a full car with 4 occupant (total of 300kgs) results in 3.5cm lost on the rear arch, leaving me with 2cm roughly between wheel and arch. No rubbing though.

Car still feels a bit floaty to me - I have ordered some new drop links as mine seem tired plus the top mount story (installing new KYB on both sides) , but besides that what can I get to improve and get a more planted feel? Front shocks are B4, rear are Sachs. It's does firm up while pushing in corners, but while simply cruising, it's a bit of a softy. Just a characteristic of the springs, perhaps? How are your Eibachs?
 

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#34 · (Edited)
@Fruity Car still feels a bit floaty to me - I have ordered some new drop links as mine seem tired plus the top mount story (installing new KYB on both sides) , but besides that what can I get to improve and get a more planted feel? Front shocks are B4, rear are Sachs. It's does firm up while pushing in corners, but while simply cruising, it's a bit of a softy. Just a characteristic of the springs, perhaps? How are your Eibachs?
Is it a stock 14mm rear ARB? If so then don't worry much about how well it is working, it is so soft that it does almost nothing. Replacing worn drop links will reduce unwanted noise (knocking), but not much more. I've driven my 147 with the stock rear ARB removed, and couldn't feel a difference to with it in place. On the other hand, fitting a 20mm rear ARB was a huge improvement, with a very substantial beneficial affect on handling, roll, and steering response, and surprisingly little adverse affect on harshness.

For a "more planted feel" you need good and reasonably stiff dampers (not significantly worn, and not way too soft to start with...). The front dampers (OE or 'stock rated' other brands) are way too soft even when new. My understanding is that the B4 Bilsteins are more or less a 'stock replacement', but may be better dampers than the OE fitment (and may be at least a bit stiffer, don't really know, but not unlikely). The OE rear dampers are much better, but still a bit soft for my taste. I have 'stock replacement' TRW rear dampers, and they are good enough if not as stiff as I'd prefer (but not soft enough that I can justify replacing them with B6 as I simply had to do with the front end, i.e. replace new but way too soft TRW 'stock replacement' with B6).

My car felt much more 'planted' after fitting the 20mm rear ARB, so that helps too.

Regards,
John.
 
#30 ·
I'd get some new rear dampers. Do you know how old they are/how many kilometres they've done?
My 156 easily dropped 3-4cm with just 50-60kgs in the boot.

Go for a stiffer rear strut as well, as it will improve handling.
 
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#31 ·
@tishobg, that looks nice.
147s didn't have the factory choice between normal and sports that 156s did. I'm not sure if that is good or bad but I have noticed KYB list struts for 147 and 156 with normal suspension. They specifically exclude 156 with sports suspension.

On that front, do you have a part number for the Sachs rear struts?

As everyone is different in preference, I'll not say B4 is too soft for uprated springs but I think that is what B6 is specifically for as well as an upgrade to factory springs. B8 is really for significant lowering.

My JTS has Koni Str.T front struts and Boge rear (specifically for sports suspension). The cr is nicely taut without being crashy or overly hard but it is firm. From what I read on here, B6 is probably a little firmer but my set-up is fine with the exception that possibly a little more damping would be better in situations when the car gets airborne which is frankly best avoided anyway.

It is very different from the TS which has factory sports struts. There is a lot more body movement with the TS which regards to body movement, pitching and roll.
Uprated struts seem to be the first thing to fit, even before lowering springs.
 
#32 ·
Today my brother in law brought his 156 (1,6 ts sportkit ordered as such in 2001 with still factory struts with 130.000 kms) so I had the chance to take some measurements and photos from both the 156, and my (normal) 147. At last I decided (and already bought eibachs, and now I'll go for the totally alfa spacers and then the struts. Here is the question. I want something not far from the factory struts. I don't care so much about road performance (from which I'm already satisfied) but for comfort mainly. That said I don't mind about ''tight'' behaviour, but I dread suspension ''knocking'' hard in every bump or (worse) the vertical ''ditches'' on the road which make me drive at pace rate. You wrote about BOGE (now referred as SACHS-BOGE). Do you have their part number? (front and rear for sportpack). I've also seen TRWs for sportpack suspension in alfaworkshop but as TRW is not a strut manufacturer I doubt their reliability. If boge ''lifts'' the car by 1cm then I won't need rear spacers as 2 cm lower is very good. I don't know. I hope you can tell me. One thing is for sure. I won't go for B6 as I drove an 147 with eibachs and B6 some weeks ago. In front things were decent, but the rear suspension didn't seem to be working at all. I think with two persons in the rear seats it would be OK, but since I usually use the car alone they are out of question. I read about KONI special active but I think that like FSDs they must be for normal height cars.
 

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#33 ·
I took some measurement as well with my -30mm Eibach-manufactured KW springs on my 2003 147.
Front - 350mm from wheel centre to arch.
Rear - 360mm on left and 370mm on right - perhaps the way I parked affected that or the squished strut mount on the 360mm side.

That's with 30mm lowering. I read some FAQ on Eibach Pro Kit height on a 147 GTA and 350/370mm sounds about right for a Pro Kit. They don't seem to have sagged.
@Fruity, what do you think?
@gnik61: Your normal 147 seems a bit low for standard springs. About 2cm in general higher than mine - are you sure you got 100% accurate measurements?
 
#39 ·
Yes I took the measurements for both cars in my absolutely flat garage. The thing with 147s height is, that I've never seen even two cars with the same height. The other problem is that in 156 with sportpack, the distance from the front bumper to the ground is 16,5 cm while in the normal 147 is 14 cm. This means that if you lower the 147 3 cm, the ''close encounters'' to the ground (in bumps etc) is inevitable. I also measured the side gaps in 147. So if you want the wheels to fill the wings symetrically you have to lower it 1,5 cm which I think is acceptable. Furthermore I drove the 156 (with factory sportpack) for some kms around my house (not in the highway). The rear suspension is perfect (according to my taste). It feels ''firm'' but with no strange noises. I can't judge the front, because the car had the stock suspension for 140.000 kms and it was obvious that it needed new struts (though not urgently).
 
#36 · (Edited)
Link to TRW parts catalogue;
https://www.trwaftermarket.com/en/catalogue/

Link to ZF Friedrichshafen which includes brands such as Sachs, Boge, Lemforder, Stabilus and TRW which are owned by ZF;
https://webcat.zf.com/?SPR=4

What I find interesting with regard to struts is that sometimes (even after excluding normal or sports suspension) there can be variation in strut length.

Unfortunately only TRW appear to be produced for our cars and Sachs/Boge parts are all but run out. I was told my Boge rear dampers for JTS, part number 32.D.18.F were the last 2 in a warehouse in Sheffield. I may very well have bought the last pair available in UK Corporation.

Anyway, have a play and input different cars. That can be quite illuminating but be aware that as Sachs and Boge brand struts are being run out, TRW seem to have fewer part numbers= rationalization = parts which are approximately right rather than exactly right. Part of the reason may be no need for exact OE specification on older cars and also producing parts to a lower price point due to type of owners who have 10-20 year old cars.

I like to see if 147 is more like 156 normal or sports. What I've found is the 147 does indeed to have more commonality with 156 normal suspension rather than sports which seems to go against the 2003 147 comfort pack suspension of softer springs and firmer dampers. I could go on but I'd bore and befuddle even myself, let alone anyone else.
 
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