Thread: Twin shocks

on fast corrugated gravel with occasional washouts etc I think I would prefer overdamped which will tend to fade a little anyway... than underdamped wallowing????

When we did the same trips in the old disco (same boat trailer) less load obviously in vehicle I was using the tough dog rear dampers and they worked really well.

The 130 rides 100% better over the broken cape roads probably due to wheel base but after the rear dampers fade it gets a little unsteady... Im gonna go with Justins experience on this one and sort out a second set of rear dampers.
Thanks all for input... I guess if I dont like it two bolts and its back to single damper.
Steve

Originally Posted by Dougal

The reason it feels more composed over corrugations is because the wheels are skipping over the top of them.
Overdamping makes the vehicle feel tighter to drive, but that's not traction.
Traction is the force on the contact patch between tyre and ground, the more even that is the more traction you get. Overdamping it means you spend a lot of time with short peaks of high force and very little in between.

The easiest place to see this happening is stopping distance on smooth gravel roads compared to corrugated or potholed roads. The more supple your suspension, the smaller the difference in stopping distance is.

Dougal my friend, I know the difference between composure, balance, traction and yadda yadda yadda. I've spent enough years in motor racing to come to terms with all of this very well. I can see that you wont come to terms with these findings, and don't know how to explain it so that you can understand, that an increase in damping from the consumer level damper gives more traction on rough terrain by increasing axle control - consumer shocks are just plain soft because they have to be for comfort and are not even remotely close to controlling the axle, let alone over controlling the axle. I've found and said this, JC has found and said this and Cal has also found this. This is what is working in practise.

Originally Posted by Dougal

The reason it feels more composed over corrugations is because the wheels are skipping over the top of them.

Huh? That's a bit of an oxymoron isn't it? Wheels skipping over corrugations would feel far from composed to this black duck.


Anyways, if you're carrying a heavy load, you need to uprate the springs, and to dampen those stiffer springs you then need heavier damping, simple really.
Where the problem lies with many shocks is the way they over do the compression, to attempt to 'assist' the spring, giving you a harsh jarring ride yet still allowing float because the rebound is inappropriate.

Hi Simon;

Looking at the same set up myself , having Bilsteins on as my first shock , would any standard shock do as a 2nd shock for load sharing reduction on compression and rebound off the rear?

or have i missed the point ?

I guess if you use a different rate shock, then most of the load would go to the stiffest one

If the difference was large then the lighter shock would be pretty much a waste of time.

Originally Posted by Disco_owner

Hi Simon;

Looking at the same set up myself , having Bilsteins on as my first shock , would any standard shock do as a 2nd shock for load sharing reduction on compression and rebound off the rear?

or have i missed the point ?

G'day mate, have to see you out on the track again!

You could supplement the Bilstein with any shock and it will increase the damping rate, but by how much depends on the extra shocks valving. I'm not sure that you should use any standard shock, but one that matches in length to the Bilstein so that you don't accidentally shorten the suspensions travel or cause damage to the additional shock from it being too long or too short.

Originally Posted by Slunnie

G'day mate, have to see you out on the track again!

You could supplement the Bilstein with any shock and it will increase the damping rate, but by how much depends on the extra shocks valving. I'm not sure that you should use any standard shock, but one that matches in length to the Bilstein so that you don't accidentally shorten the suspensions travel or cause damage to the additional shock from it being too long or too short.

sorry mate , I should have explained myself a little bit better , What I meant was a standard shock of the same length as the Bilstein , and idea is to increase the dampening rates, which you have covered already.

and with regards to the track look forward to joining you fellas again for anther fun day out soon.

Originally Posted by 100I

Huh? That's a bit of an oxymoron isn't it? Wheels skipping over corrugations would feel far from composed to this black duck.

It's quite simple.
Drive over corrugations slowly, the whole vehicle feels each one. Drive faster and faster and you'll only touch the peaks.
It's about frequency response. Damping reduces the speed (and frequency) that the wheel can move at. Resulting in in contacting the ground less often at higher frequencies.

Stability and traction are not the same thing. Acheiving a suspension setup that acheives both is the difficult part.

Slunnie's motor racing observations are correct, but he didn't mention that your average racing can has suspension that's twice as stiff (twice the natural frequency) as your average road car.
That needs a lot more rebound damping to control.
The difference in spring and damper rates between track racing cars and rally highlights the differences quite clearly. To travel quickly on a rougher road, you need a much higher frequency response.

My background in suspension tuning is mountainbikes, the scenario is quite similar to motocross with the biggest difference being chassis weight.
Making a 2.5" wide tyre stick to a dirt track shows you quite quickly and easily what costs traction, overdamped rebound (esp the high speed circuit) is a killer.