News:

The ORG - 100% FREE advice!

Main Menu

6.9 Handling

Started by TJ 450, 20 September 2010, 08:36 AM

WGB

The two most irritating features of my 6.9's handling have been

1) the level of bump-thump over a 450 steel suspension - not helped no doubt by the 16 inch 225 section tyres
2) level of bodyroll on going around a left hand bend - Right hand bends are very flat and full of confidence for some reason.

The nicest feature is the absorption of very large bumps superbly.

I have rebuilt my front suspension with replacement of all joints with the exception of the two firewall mounts for the sway bar and am about to do a total rear end rebuild of all bushes as well as do the 560 driveshaft conversion.

I have already replaced all the rear subframe mounts (The leading edge subframe bushes were the biggest improver of the rear end roll`) and replaced both rear strut ball joints.

The second biggest "roll improver" was to remove the rear seat and take the slack out of the top bushes - what happens is the lower rubbers compress and leave a gap between top mount and chassis which does nothing for the roll.

My main question is - how important are the main swaybar bushes?

I would think these are critical and I see there is an updated rear swaybar bush which has now superseded the old part - I had been considering replacing miy roll bar bushes with nylon type uprated ones..

It would in my opinion be vitally important to make sure the bushes and joints are up to scratch before suspecting the hydraulics - as far as roll is concerned - as roll control with the hydraulics appears to be only governed by the effective damping rates.

Bill

TJ 450

Interestingly, the sway bar bushes don't seem to wear to any great extent. The difference may be marginal with new rubber ones, but urethane ones will improve the performance I reckon (harder compound).

Perhaps the hydro suspension does rely more on the rubber parts than conventional.

I agree with the higher level of bump-thump... I thought it was just my car though. I must have thought the grass was greener on the other side. ;)

As for the tyres, wider would definitely be better for cornering... MT's car is a good example of that.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

Big_Richard

wtf is bump thump ?

Please explain

TJ 450

MT, bump-thump is referring to the system's inability to damp higher frequency bumps vs. those of lower frequency.

I believe this may just be a compromise to allow a firmer ride than Citroens of the period for example.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

koan

Quote from: TJ 450 on 26 September 2010, 09:20 AM
MT, bump-thump is referring to the system's inability to damp higher frequency bumps vs. those of lower frequency.

That would explain something I experienced years a go, a section of scarified tarmac on the freeway but done crossways not the usual way caused really severe vibration. Didn't seem to matter if I hit it at 80 or 30 kmh.

koan 
Boogity, Boogity, Boogity, Amen!

Big_Richard

That phenomenon would then be exaggerated by excessive sprung weight then, ie, having bigger, heavier wheels and tires than stock.

i have 235/60/r14 tires from memory and i don't think i've ever noticed this issue but perhaps you can point it out to me when i put my seats back in, in the next couple months.

TJ 450

#36
I haven't thought about it a great deal, but I don't know that a larger degree of unsprung weight would reduce the effect. I think any benefits would be counteracted by the assumed lower profile of the tyres.

Certainly, it would be interesting to see how your car behaves though, plus the seats will be nice indeed.

Additionally, the 6.9 handles well on dirt roads... just watch those corrugations though. ;)

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500