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BigJimnyMeet (North) 2024 (12 Jan 2024)


BigJimnyMeet 2024

14th July 2024
Parkwood Nr. Leeds

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This section on other websites has led to arguments and contention. People are posting pictures of their pride and joy and therefore CONSTRUCTIVE comments only please!

Discreet but capable

  • Lambert
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14 Feb 2019 05:32 #203181 by Lambert
Replied by Lambert on topic Discreet but capable
Sorry but you're misunderstanding your own explanation. The length of the drop links is not how you adjust the resistance of the anti roll bars. On a Jimny the anti roll bar is a fixed rate item. It only has one hole in each end of the lever arm therefore the effect of the lever is static and unadjustable. If you raise the relative position of the chassis to the axle the anti roll bar is then no longer sat with the arms level to the chassis and the drop links are no longer vertical. This creates 2 main problems. First the way any forces are transferred through the links and chassis bushes is in a plane they aren't designed to accommodate causing severe wear. Secondly as the suspension flexes there is a greatly increased risk of the link and lever arm becoming straight to each other and even going beyond that and inverting which is very very bad. What your adjustable drop links do is give you the means to re level the lever arms so that the system is operating as it should. They also have the added benefit of being much more robust than the factory ones meaning that they transmit the forces more efficiently into the arb. In order for the effective rate of the bar to be tuned you would need lever arms with multiple holes at various distances from the mounted axis of rotation of the bar at the chassis end. These will then alter the leverage ratio where a set of holes near the rotation axis make the bar seem firmer and a set of holes away from the rotation axis make it feel softer.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
ADOS Attention Deficit Ooooh Shiny!

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14 Feb 2019 09:38 - 14 Feb 2019 09:42 #203190 by sniper
Replied by sniper on topic Discreet but capable
Lambert, I think it's you who has the wrong end of the stick.........

Raising my car has increased the preload on the ARB, the distance between the axle and the lower point of the ARB is now greater than it was. The link length is the same so the tension it is under is greater.

This has affected the suspension negatively (adding a spring where there shouldn't be one), to a certain degree you can negate this increased ARB "bounce" by increasing the damping rate.

Increasing the damping rate will only go so far (and not that far) to negate the preload or spring. The damper pushing against the spring....

If you look back in my build post, when I changed to Superpro ARB bushes, there was a change in the ARB behaviour, I was able to address it by increasing the damping.

I said that I could tune out some of the effects of the increased preload by increasing the damper rate, I didn't say that you tune your ARB by fitting adjustable links, which I stand by. I shall be trying later today.....If I cannot achieve the desired effect, then adjustable links will be required.

Don't know where adjusting the resistance of the ARB has come in to it... that was never a stated aim.

"Only had a short drive on a tight and twisty back road and it feels different, a tad twitchy on the steering but I think that's because the lift has tightened the anti roll bar. I might be able to adjust the dampers to address it or it's another spend on adjustable drop links."

I think you've grabbed my phrase "tune it out" and taken that to mean much more, a few clicks of adjustment on the dampers, if that sorts it, great.
If not, then it's £80 worth of shiny bits..... Superpro adjustable drop links. They will adjust to remove the preload or "tune it out".......

I use the word "tune" to confer the small adjustment of one component which may affect the behaviour of another component.

I can't see where or why you would disagree with that, I'm proper confused pal....

sniper
Last edit: 14 Feb 2019 09:42 by sniper.

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14 Feb 2019 10:27 #203194 by Jezz
Replied by Jezz on topic Discreet but capable
:laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :unsure: :dry: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh: :laugh:

It's been fettled just a tad.

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14 Feb 2019 10:35 #203195 by Lambert
Replied by Lambert on topic Discreet but capable
The anti roll bar is a spring acting against itself. It is attached to the car via 2 bushes that allow it to rotate relatively freely on an axis of rotation of parallel to the axle. It is not solidly affixed to the car. It acts by compensating between the loads applied to it at each end by the axles flex via linkages attached to the return arms which are essentially fixed length levers. At rest on level ground there is no tension in the anti roll bar. It has no static load bearing capacity. The relative length of the linkages has no bearing whatsoever on the effective length of the lever arms. The only way to preload the bar is if you're going to artificially lengthen one linkage more than the other but doing so is monumentally dangerous as the car will no longer have an equal roll response in both directions.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
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14 Feb 2019 11:41 - 14 Feb 2019 12:15 #203199 by sniper
Replied by sniper on topic Discreet but capable
You are missing the point..... I understand that there is no preload designed into the ARB. Once a load (roll) is applied, forces along the ARB are torsional, the load fixes one end and the ARB applies force to the other.

My problem is that the axle is now further away from the ARB, this has changed the angle and tension on the standard length drop links. They should be vertical and under no tension. These angles have been changed by moving the bottom datum (axle) lower, this has pulled the ARB down and made the drop links sit at an angle. These small changes have caused a spring action across the ARB, that is what I am addressing.

If the drop links are extended so that the roll bar and the drop links are back in their neutral position, the spring that I'm experiencing will no longer be there. It couldn't be simpler...... restoring the ARB to normal position.

If the dampers can't absorb that spring, lengthen the drop links to remove it. Both links will be fitted at the same length.

I can't explain anymore than I have done, sorry.

Adjustable drop links are used on most tuned suspension systems, they can also be adjusted to help with small corner weight changes, they are a very common piece of kit. Why do you think they have no impact ?

Have a look at chassis dynamics by Sam Borgman at Torque Developments.

sniper
Last edit: 14 Feb 2019 12:15 by sniper.

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14 Feb 2019 12:28 #203203 by Jezz
Replied by Jezz on topic Discreet but capable
When the preload gets to much.


It's been fettled just a tad.
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14 Feb 2019 13:40 #203205 by Lambert
Replied by Lambert on topic Discreet but capable
It was the use of terms like preload that were causing my issue. Now that I understand that its an alignment issue then yes longer links to restore the correct orientation and operation of the anti roll bar is what you need. If you correct the alignment and are still having problems with the springs and dampers controlling the movement of the axle it's not entirely impossible that something is bent that shouldn't be. Fix the anti roll bar first and see what changes. Plenty of others have similar lifted cars and seem to be happy with their dynamics but yours doesn't sound happy with itself.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
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14 Feb 2019 14:54 #203209 by sniper
Replied by sniper on topic Discreet but capable
I've put a few miles on it and couldn't understand what had happened, took a look underneath and the castor correction bushes have been fitted in the opposite orientation to the correct fitment.

God knows how he got it wrong..... I took a picture with me and showed him, the front bush to the top and the centre bush to the bottom. He must have just held the radius arm upside down. The garage was very apologetic and has booked me in to rectify it on Monday, gratis.

Lets hope that this rotates the drop link mount and resolves the whole issue. From what Lambert says, few others have had a problem.

sniper

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14 Feb 2019 15:14 #203210 by Lambert
Replied by Lambert on topic Discreet but capable
Oh my God! I'm actually crying with laughter! That's appalling! It also explains a lot! Wow! At least you found it.

Temeraire (2018 quasar grey automatic)
One of the last 200ish of the gen3s, probably.
ADOS Attention Deficit Ooooh Shiny!

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18 Feb 2019 16:35 - 18 Feb 2019 16:37 #203407 by sniper
Replied by sniper on topic Discreet but capable
After painting a picture a child could follow..... the garage has got the castor correction right and the car drives very well.

Good lad Dave, dropped a clanger but sorted it and ate humble pie with grace....

On a negative note, he found that a front shock was leaking and giving poor performance.

This damper was delivered late, as it was received damaged at Jimnybits having been supplied from AVO. It took a few weeks to get to me and I suspect that the original damaged unit was repaired and then sent on.

I can identify the unit as it was supplied with a different colour bush to the others and comment was made at the time. It's inside the 12 month warranty by only a few days, but 12 months is 12 months.

We'll see how it goes, Russ has always been cool. I got a discount on my diff as recompense for the original problem...

I'm still going to have to buy some dampers to "get by on" whilst the AVO is repaired / replaced. So it's going to cost me, even on a free repair...

sniper
Last edit: 18 Feb 2019 16:37 by sniper.

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18 Feb 2019 17:45 #203411 by jackonlyjack
Replied by jackonlyjack on topic Discreet but capable
Glad you got the bush situation sorted pal
sorry to read about your front shock problem
If you're thinking of getting something to get you by
I am sure the vit mods ones are actually rear MK3 astra shocks with the bush sleeve drilled out

Jack
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19 Feb 2019 06:13 #203428 by Quasi
Replied by Quasi on topic Discreet but capable
Did the Eibach springs come with any specifications, such as spring rate and free length?

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