any suspension gurus on here? harsh ride

[dieselnutjob]

I have being doing some further investigate into the terrible ride quality on the 607.  This is a big 1725kg car so it should be easy..

 

I have been comparing spring rates with the Rover 75 and 406 as these cars have a reputation for a compliant ride quality, and the difference isn't that great.  The spring rates on the 607 appear to be about 15 to 20% stiffer than the 75, but the car is 8% heavier (though this might be more at the back that on the nose).

 

My 607 has always been a bit firm, and was bouncing on certain rippled road surfaces (end of Marylebone high street as it goes up onto Paddington flyover) and the shocks were leaking.

 

Last summer I put a pair of new Bilstein B4 shocks on the front which stopped the bouncing but now the ride is just harsh.

 

Specifically it's okay on the motorway, and things like speed humps are okay, but potholes or lines/joints in the road surface at 30mpg are terrible.

 

How do I tell whether these shocks are coming through the spring or through the shock absorber?

 

What would the ride be like if I put a softer spring in with the same shock absorber?

 

Should I get some rubber in there? for example a layer of rubber could be put between the top of the strut and where it sits on the inner wing

 

The handling of this car is amazing; I've never had something that cornered so flat, but I would really prefer better comfort as I'm not really a quick driver and most of my driving is on the M25 or around towns.

[scooters]

 

 

The handling of this car is amazing; I've never had something that cornered so flat, but I would really prefer better comfort as I'm not really a quick driver and most of my driving is on the M25 or around towns.

 

This - I suspect the stiff suspension that allows it to go round corners on rails is causing the harsh ride. The trend in modern cars over the last 10 years has been towards increasingly hard suspension and thinner tyres - sportieness. If you are used to chod then it makes for a harsh ride.

 

when of course most of us sit in traffic jams and drive on motorways and towns where comfort is more desirable.

 

In the urban road hell that is Edinburgh (council spunks road budget on trams EXTRA!) the only vehicle I like to drive is the CX.

 

If road holding and comfort is your quest then the best mechanical combo is a jag in XJ 6/40/300 flavour or a hydropneumatic car - a CX, BX, XM, some Xantias and C5s etc although the harder trend exists here as well

[Split_Pin]

Bilstein B4's are uprated items, no doubt for bump and rebound, so this deffo explains the mega crap ride. As such they will have a different rate to the softer springs and everything will be oscillating at different frequencies causing the whole lot to should 'Oh Merde!'.

 

I'd get some dampers that have been designed to work with the standard springs. Are OEM items too expensive?

[gordonbennet]

I delivered a good number of 607s when new and they stood out for the compliant ride.

 

If it was firm with the previous buggered shockers then i'd be wondering if it still has OE springs.

 

Still running standard tyres and wheel?

[Barry Cade]

I remember reading, many years ago- and I'm sure it was LGK Setright-  that Peugeot were the only car company to actually design and produce their own shock absorbers. Don't know if this was the case when the 607 was built, but tells a story. Remember Springs control the stiffness and shocks  (or dampers) damp the ocilliation of the spring. Stiff shocks will damp the action of the spring giving a harder ride but really do not allow the springs to absorb the bumps as they were designed to. First line of suspension is the tyres- Peugeot and VW seemed to hold on to high profile tyres for longer than most.

[dieselnutjob]

I don't think that Peugeot still make their own shocks.  My guess is that this was back in the 505 days.

 

The springs are colour coded and matched what I would expect on the parts database (i.e. one of three options all of which appeared correct).

 

I thought that the Bilsteini B4 was the comfort oriented "good quality OEM" option, according to their website.

 

Tyres are 225/55R16 winter tyres with 32 PSI in them, so very slightly under inflated.

 

I measured the spring rate at about 19700N/m (about 108 lb/in), and with front axle loading at 960kg.  Is that a particularly hard spring?  I have no experience.

 

There are loads of people on various forums complaining about hard ride on the 607. One story is that prototype ones would swap ends and so Peugeot hardened up the front to counteract it.  Certainly if mine is pushed it will understeer and doesn't seem as neutral as my 305 was.

[Pete-M]

Pug made their own shocks for the 205 GTi. Don't know about ány later ones.

 

Billy Steins Bobble Reducers will give a harsh ride on most things.

[dieselnutjob]

The b4 is the oe replacement that Bilstein list but they are slightly uprated (maybe 10%). Under advice I fitted a set along with Eibach springs to my old mk2 Golf and the ride was shocking on anything other than very smooth roads.

 

isn't that likely to be the Eibach's as much as the shocks?

 

what I really want to know is this, is 19700N/m a stiff spring for a 1725kg car with 960kg on the nose? or not?

[willswitchengage]

You will need to match your shocks to your springs. Stock shocks will be designed to create the correct response re the derivative of your springs. Put in stiffer springs and you will get a bouncy ride as the spring rate isn't being restrained effectively enough. Your car will handle worse as a results due to massively fluctuating thee contact forces

[willswitchengage]

Manufacturers spend billions getting the best ride response, halfords and kids with baseball caps don't have the same budget

[carlo]

Yes I remember when the 607 came out; it didn't handle particularly well and Peugeot made some hasty revisions to it.  The car came out in my last year of selling Peugeots, I remember it as having really good seats, but not a particularly marvellous ride.

 

One thing I have begun to notice with my 405s, and this may apply to you, is how much perception can influence your impression of something like the ride quality.  I came out of my last 405 in October into another one, and was immediately struck by its inferior ride quality.  I have terrible back problems and pick up on these things.  However I can recall similar impressions on previous occasions when I have changed a car I have had for a while and really grown into.  The point is once I had decided the ride was worse I could think of nothing else, every bump seemed to send a shudder through me and the whole car.  Everyone else who drove it wondered what all the fuss was about, and I have to say that, now, after a couple of months, it seems quite OK!  The more I think it's not too bad really the better it gets, in fact I bloody love it now more than my last one.

 

But then I am a silly old sod really.

[dieselnutjob]

That's interesting and probably true.

 

That said, I would think that knowing the weight of a car, weight distribution, and the type of handling / ride balance that one is after, it would not be too difficult to calculate a spring rate that would achieve it.

 

I'm sure that Peugeot can achieve that, it's just that their objectives would be different to mine, i.e. they probably wanted journalists to say that it handles as well as a 5 series etc.

 

My objective is different.  I want to slush around in relative comfort.

 

This shouldn't be such a black art.

[dieselnutjob]

I managed to do some maths / science on this.

I bought a used strut on ebay with the same spring to play with.

I found that the spring totally uncompressed is 38cm, and 17cm with the car on it.

I know that the front is 960kg, that a wheel and tyre is 23kg and a strut is 7kg.  I will guess another 10 for the hub, brakes and drive shaft.

So that gives me a spring rate of 480-40kg / 38-17 = 2.095kg/m or 117lb/in

There is a suspension frequency calculator here

http://www.racingaspirations.com/apps/wheel-frequency-calculator

 

plug those numbers in and you get 1.09Hz or 65cpm

Their advice is that 60-80 is "normal" and 80-100 is "sports".

 

hmm time to have words with Bilstein I think

[DSdriver]

I would change the shocks for a set of Spax adjustables. That way you can adjust them on the car to suit your style of driving.

Being used to the ultra-comfort of the DS as my daily driver when I got the XM I was worried that maybe the spheres were knackered because the ride is a bit bobbly. A short trip as a passenger in a Mercedes A class set my mind to rest though. Do those things have any suspension at all?

[twosmoke300]

No it's just the dashboard bouncing around

[Lacquer Peel]

Aren't these based on the XM platform? Just convert it to hydropneumatic suspension, I'm sure it'll be easy*.

[wackywacerwill]

Get small wheels then fit big tyres.