The V8 Owners Forum -

I have a Granada Cosworth rear end, one of the dampers sprung a leak so I bought a new pair.
The new ones weren't pressurised like the old ones (the old ones rapidly extended by themselves when removed) and the suspension was a lot softer and often bottomed out.
Now knowing that I needed different dampers, I bought a pressurised pair but Sods Law prevailed and they weren't as pressurised as the originals and I still had bottoming out when loaded.
Rather than spend out on yet another pair of dampers that may not work (unfortunately I didn't think to take any part numbers from the original leaky dampers) I thought I'd try a pair of those rubber split doughnut things that you thread in between the spring coils - they were cheap (~£10), seemed to make the suspension stiffer and cured the bottoming out.
BUT, the back end now feels a bit bouncy and underdamped - does it sound likely that the rubber bits to could increase the effective strength of the springs to the point where they overpower the dampers?

If you need better dampers, you need better dampers.

A spring / damper / mass system has a oscillation frequency. If you change any of those three, the frequency will change.

You can see that when 'Barry' has lowered his VW Polo, and it bounces along the road. The frequency is too high, and it is underdamped. Barry doesn't realise this and thinks it looks cool. Really he's just fitted stiffer springs and not changed the dampers.

The manufacturer goes to a lot of effort to get a good balance between tons of conflicting requirements, and factors in lots of other more nuanced areas, such as not hitting the bump stops.

The best solution is to stick with what the original manufacturer intended if you can still get the bits!

Chris.

Cheers for the replies, looks like I'll have to keep hunting for some original spec dampers.

what car is the Granada cosworth rear end in? If not a granada then the standard dampers may not be ideal?

Tom.

Its in my trike (4.6 Rover & LT77), the ride and handling was spot on before I renewed the dampers. I'm assuming the old leaky ones were the originals but who knows?
I'm going to have a look and see if there's a Granada owners club, with any luck they'll know.