1800: How low should I go?..

[classicswede]

Originally Posted by 142 Guy

Second thing to keep in mind is that shorter springs typically come with higher spring rates. With a shorter spring you have lost wheel travel and need the higher spring rate to keep the suspension from hitting the bump stops all the time. On my 142 I had some short single rate Lesjofors springs (25 mm drop in ride height) and they were brutal. Any sort of traffic control strip would get the rear end air born unless you slowed to around 10 km/hr. Keep the spring rate in mind when you select springs. If you install shorter springs with a higher spring rate do not install ARBs at the same time. Test first. The higher spring rates will give you an automatic increase in roll stiffness and adding ARBs may make the car brutal on anything less than perfect pavement.

I ditched the Lesjofors on my 142 and installed the Amazon cars springs for the 140 on my car. Much more pleasant to drive.

You are right about not doing anti roll bars untill after doing springs and dampers as for most drivers once they are done there is no reason to change the ARB setup.

Lowering springs do need to be stiffer than standard spring rate. Too stiff and the ride is harsh and too soft and the ride is harsh. Typically too stiff is harsh at low speed and too soft is harsh at speed. Most Lesjofors spring sets tend to be at the too soft end of the scale. (140 sets are on the stiffer end of right for the front and softer end of right in the rear but they might of changed since I last tested a set) Dampers that are matched to the weight and spring rate are also important as over damped will harsh and under damped will be harsh! Get it wrong and the ride is harsh, both springs and dampers need to be in the window.
Due to the low weight in the rear of the car progressive springs are usually better in the back, they are not softer as often stated. It is the increase in travel and the the soft section when the wheel is unweighted that helps

[Puntah]

Thanks, that's helpful.
Looks like I'm after 40mm progressive lowering springs with some suitable shocks. On my previous car I fitted 40 mm lowering springs, IPD front ARB and Bilsteins and poly bushes all round. The car certainly behaved better on cornering but you could feel every single variation on the road surface! This time I hope to get the same cornering but perhaps a more comfortable drive generally.

[Derek UK]

Poly and comfort don't usually make good bedfellows but poly density does vary. Volvo's original rubber bushes were OK. NVH wasn't such a big issue as it is today. Modern/current rubber bushes, even from Volvo, don't tend to be as good as they were originally. Bottom line, maybe soft rated poly bushes the best choice except on the body end of the Panhard rod when I'd still pick the original rubber one #87033
As spring is actually a torsion bar so if you shorten it the stiffness increases.

[Puntah]

Thanks Derek,
That's helpful info - I hadn't realised there were different densities of poly bushes.
On DOY, I fitted a 'new' rubber bush on the steering idler and it failed MOT within a couple of years.

Gordon

[Nullifie]

Lowering a P1800 decreases the driveability of the car if the road isn't smooth enough. I did bring my P1800 up to the original level (from being lowered by old springs) for my exhaust did stop me a few times (not mentioned the times the exhaust scatched the road). But my P1800 is in use as a car not as a sunday-toy: transporting things in it (up to an engine) and also using bad roads (if road is the right word for them).

[Derek UK]

Gordon. If you look at Simon's comment on the Brookhouse site re idler bush it's possible that you used the one that he now doesn't recommend.