Holden front end mods

[Taily]

indeed so... Yet unlike you I don't rely on unproven heresay from the internet.

For everyone else with an open mind here are both sides of it.

I'll eleborate, if you cut stock springs they will be slightly stiffer but still too soft for the reduction in travel from missing coils, the stock coils add much needed wire length, not stiffness is what I was trying to say. The reduction in height is not compensated by the increase of stiffness...

If you imagine a coil as a long bar with one end stuck in a wall:

Make the bar shorter and it will be harder to bend from less leverage and harder to twist as there is more twist per distance of material... make it longer and it will be easier to bend from added leverage and easier to twist from less twist per distance of material.

Thats the way i see it, there's formulas to work out spring rates, but in essense the manufactured rate of the spring doesn't change ie; a 500lb wire coil is still a 500lb wire coil, yet I still think the reduction in height is not compensated
by the stiffness gained from cutting coils and by the time the stock spring is stiff enough from removing coils (any noticeable change without measuring equipment) it would not be captive or effective in travel (would coil bind).

Looking at the practicality of it: Take some stock springs at 330mm cut to 300mm and compare to some low king springs at 300mm and 30% stiffer, not that I like or endorse them, it is just their data straight from their catalogue.

kings springs:
- 30mm drop which is 10%.
- 30% stiffer

stock springs at 330mm and cut 30mm off:
- 30mm drop which is 10%
- 10% stiffer is my guess?

Now the legality of it:

Everyone needs to be careful about public advice that contradicts what is contained within the various acts in reference to altering installed components by welding or friction cutting fitted components, or reducing the suspension travel by more than one third (a standard spring W series Holden has a front suspension travel of only a shade over 90mm before the bumpstop first touches - how you measure installed spring travel depending on the variant) - however do not confuse jounce and rebound with suspension travel as they are two very different things. So standard front coils that have had an amount of wire removed that results in a reduction of travel of more than30mm in the eyes of the (RMS at least) is outside the Act and is not a permissable modification. HOWEVER.... Should you install manufactured lower springs that reduce the ride height in this way then the suspension travel value changes doesn't it?

The better option (of the lot) is to retain full suspension travel (bear in mind that suspension travel is the one safeguard against the inherrent cracked chassis issues our busses have) and fit either approved dropped spindles or a combination of lowered (not cut) coild and dropped spindles. As I mentioned earlier they also have another benefit in they realign the tie rod end pin centre closer to an ideal point which improves bump steer imessureably (much nicer on the road).

Hopefully that spells it out in a way that most will understand. It gets to be a slippery slope if you get caught cutting suspension components however the reason many AIS and insurance peeps turn a blind eye and don't want to know (until they can use it to deny your claim) is that nobody wants to deal with the legal burden of proof that goes along with identifying modified components.

[Gm nut]

indeed so... Yet unlike you I don't rely on unproven heresay from the internet.

For everyone else with an open mind here are both sides of it.

I'll eleborate, if you cut stock springs they will be slightly stiffer but still too soft for the reduction in travel from missing coils, the stock coils add much needed wire length, not stiffness is what I was trying to say. The reduction in height is not compensated by the increase of stiffness...

If you imagine a coil as a long bar with one end stuck in a wall:

Make the bar shorter and it will be harder to bend from less leverage and harder to twist as there is more twist per distance of material... make it longer and it will be easier to bend from added leverage and easier to twist from less twist per distance of material.

Thats the way i see it, there's formulas to work out spring rates, but in essense the manufactured rate of the spring doesn't change ie; a 500lb wire coil is still a 500lb wire coil, yet I still think the reduction in height is not compensated
by the stiffness gained from cutting coils and by the time the stock spring is stiff enough from removing coils (any noticeable change without measuring equipment) it would not be captive or effective in travel (would coil bind).

Looking at the practicality of it: Take some stock springs at 330mm cut to 300mm and compare to some low king springs at 300mm and 30% stiffer, not that I like or endorse them, it is just their data straight from their catalogue.

kings springs:
- 30mm drop which is 10%.
- 30% stiffer

stock springs at 330mm and cut 30mm off:
- 30mm drop which is 10%
- 10% stiffer is my guess?

Now the legality of it:

Everyone needs to be careful about public advice that contradicts what is contained within the various acts in reference to altering installed components by welding or friction cutting fitted components, or reducing the suspension travel by more than one third (a standard spring W series Holden has a front suspension travel of only a shade over 90mm before the bumpstop first touches - how you measure installed spring travel depending on the variant) - however do not confuse jounce and rebound with suspension travel as they are two very different things. So standard front coils that have had an amount of wire removed that results in a reduction of travel of more than30mm in the eyes of the (RMS at least) is outside the Act and is not a permissable modification. HOWEVER.... Should you install manufactured lower springs that reduce the ride height in this way then the suspension travel value changes doesn't it?

The better option (of the lot) is to retain full suspension travel (bear in mind that suspension travel is the one safeguard against the inherrent cracked chassis issues our busses have) and fit either approved dropped spindles or a combination of lowered (not cut) coild and dropped spindles. As I mentioned earlier they also have another benefit in they realign the tie rod end pin centre closer to an ideal point which improves bump steer imessureably (much nicer on the road).

Hopefully that spells it out in a way that most will understand. It gets to be a slippery slope if you get caught cutting suspension components however the reason many AIS and insurance peeps turn a blind eye and don't want to know (until they can use it to deny your claim) is that nobody wants to deal with the legal burden of proof that goes along with identifying modified components.

So now you do agree with me, cutting a coil will increase the spring rate ....... good to learn new things hey!

[Taily]

So now you do agree with me, cutting a coil will increase the spring rate ....... good to learn new things hey!

Nope, read my post even closer next time. Again you are confusing rate with stiffness. I said the rate of the spring doesn't change and it doesn't, as you shorten the wire that same weight of the vehicle must be supported by the remaining coil wire (load factor increase by the % of coil wire removed) and this is why it 'feels' stiffer. You are splitting hairs trying to make me agree to something that isn't true. Most people attend this extra 'firmness' of the ride to the spring, but it is more likely to the combination of shock nearing bottom out at installed height and the twist in the bushes that people don't seem to bother backing off before lowering their car. Besides, a shorter spring has to work harder, work hardens quicker and ultimately doesn't last the distance.

If you know so much about rate then remind me again how it is measured? Ahh, you forgot that?

I'm not wasting any more time on this, you're obviously someone who believes in everything he reads on the internet and just in it for the shit stir, I called you out on your claim that you were supposedly a qualified engineer and you were strangley silent...

Bollocks !! How can cutting a spring increase its rate ?

All you have done is to reduce its height (both free & installed), the rate will remain the same unless somebody heat treats it.

Most guys, lower their car by too much. Most do it for looks, not necessarily to improve the handling.

Take a leaf out of the car manufacturer's books & lower it by say just 1-inch, but increase the spring rate at the same time. This is why an HZ RTS car in stock form handles so well. Even the HZ GTS, one of Holden's best handling cars of the era, wasn't dropped on its guts.

The big trick is get the increased spring rate matched to the shock absorber's damping rate. It's almost a 'black art', look at how much time the V8 Supercar teams spend to get that extra 1% over the opposition, simply by altering spring & shock rates.

I doubt any insurance company would lose any sleep over a car which had cut springs, unless it was lowered to a ridiculously (illegally) low ride height. It would then qualify for a defect anyway.

Dr Terry

Spot on Dr Terry!