Subrame bushes effect on ride?

[Spetz]

Hi everyone,

Can someone tell me how much of an affect the bushes that mount the subframe onto the chassis have on ride quality?

I have a 2003 Mitsubishi Diamante which I find isn't soft enough over bumps.
Most bushes have been replaced with new genuine ones and I run Sachs shock absorbers.

The subframe bushes are the original ones at 155,000 miles

 

[Johnny2Bad]

Polyurethane bushings (aka "Bushes" in Oz speak) are stiffer and should tighten up the road feel. OEM bushings are typically softer and made of a synthetic rubber that is subject to both movement-wear and UV-deterioration. So at 155K miles it might be replacement time.

When you stiffen up the frame (including subframes and box sections of a unibody car) then that leaves the work of ride quality and handling to the suspension, where it properly belongs. But it will also reveal any suspension issues that may exist. Shocks that can be custom valved and spring rates calculated based on vehicle weights and dynamics work best.

 

[dlundblad]

It has a lot to do with ride. I am assuming your steering and therefore suspension is hooked up to it?

 

[Kira]

You say your stock setup "isn't soft enough".
EVERY poly bush I've seen claim tightening-up as a feature.
I do not know how you'd go about "softening" a bush's performance other than drilling neat holes through it.

Maybe use a heated rod to melt clean holes through whatever material the bushing is made of.

You don't want ragged edges because that is where tears will start.

 

[Spetz]

I did not replace bushes with polybushes.
I stated that I replaced them with genuine ones (i.e., factory Mitsubishi bushes).

Yes the suspension and steering (other than the top mounts) are connected to the subframes.

But as it feels stiff going over bumps, how much of this is to do with the spring/shocks transmitting energy via the strut tops to the body and how much of this would be via the subframes attached to the chassis?

 

[maxdustington]

Originally Posted By: Spetz
I did not replace bushes with polybushes.
I stated that I replaced them with genuine ones (i.e., factory Mitsubishi bushes).

Yes the suspension and steering (other than the top mounts) are connected to the subframes.

But as it feels stiff going over bumps, how much of this is to do with the spring/shocks transmitting energy via the strut tops to the body and how much of this would be via the subframes attached to the chassis?


When you say stiff over bumps I immediately think of springs that are too stiff. Both my car and my sister's car both have lowering springs and you can really feel how stiff they are compared to stock springs when you hit dips in the road.

 

[Touring5]

I guess it depends on the suspension design and bushing material.

I can tell you that on my BMW wagon the rear subframe bushings deteriorated and the ride was terribly harsh (new shocks didn't help much). I replaced the bushings and the difference was like night and day. This seems to affect the wagons more than the sedans, so on your vehicle YMMV.

FWIW, the original bushings were oil-filled rubber and over time the rubber cracks and loses all the fluid.