Differences in sprint rate between petrol and diesel?

Hey everyone.

I've got my two front suspension shocks off at the moment ready to fabricate my own spacers to give it some lift, one thing i'm going to do though is replace the springs as i'm going to have new springs sprayed red and at ten years old i expect the old ones are sagging a bit now.

One thing i'm unsure of though are the spring rates. I'm thinking if the springs have a heavier rating for the dieseled engines, and i fit these to my petrol, they'll give a bit more lift?

i.e. do the petrols have lighter rated springs
i.e. do the diesels have heavier rated springs

have you checked with your insurance company about them accepting modified vehicles ?

They accepted my modifications so far (engine, exhaust, bodywork, lights and other bits and pieces) so can't see why they'd not allow this. If they don't i'll change insurance.

crewebiker said:

They accepted my modifications so far (engine, exhaust, bodywork, lights and other bits and pieces) so can't see why they'd not allow this. If they don't i'll change insurance.

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i'm just imagining the conversation you might have with the insurance assessor after you've just had a prang

"where did you get those lift spacers from as we might need to get them tested under construction and use regs"

don't worry it's just me being pessimistic

What modifications?

since when was the last time an insurance inspector checked the springs.

Just anti-bling them and nobody will give a second glance


Not sure if they're different, I'd say they were all the same in petrol and diesel, same payload and axle ratings,

Northern Irelander said:

since when was the last time an insurance inspector checked the springs.

Just anti-bling them and nobody will give a second glance

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ya know, the one they send round to the garage where your mangled vehicle has been recovered to to they can check the garages estimate before they approve the repair bill ....

or the plod accident investigator ......

Northern Irelander said:

Not sure if they're different, I'd say they were all the same in petrol and diesel, same payload and axle ratings,

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After having a look on Paddocks spares, the rear springs seem to be the same for all but it lists different front springs for the petrol or diesel. It even lists different springs for air con or no air con?

The difference will likely be in the free length. The spring rate will be the same as the max front axle loads are the same for all models but the ride hight for each unladen weight is maintained by the springs free length, hence the difference with AC fitted. You could ring them and ask which model has the longest springs, if it turns out to be diesel or KV6 then you can assume they will give some lift with a lighter engine.

Aye, good idea to give them a ring, however i'd be surprised if it went on free length as the struts are likely to be the same length.

As far as bikes go, if you're a heavier rider you fit a higher rated spring, and you should never fit a longer spring than the available free thread by squashing it down.

Not sure if motors use the same principle though?

Here's a bit of info on the KV6 which mentions the free length principle. I'm guessing that this is how they achieve the same bump stiffness across all engine variants with standard suspension. As long as the strut is designed to accommodate the longest spring without becoming coil bound at full bump then there wouldn't be an issue. Of course the springs may be stiffer as well but I can't find anything to confirm that.

On vehicles fitted with air conditioning, the front springs are approximately 5 mm longer. This maintains the correct
ride height with respect to the additional weight of the air conditioning equipment.
On 'Sport' derivatives (2004 MY), the suspension is 30mm lower and the springs and dampers are 30% stiffer than
standard models.
The following spring data table shows the colour codes, spring free length and the number of coils applicable to each
model:
Front Suspension
Model Spring Colour Code Spring Free Length Total No. of Coils
KV6 without A/C YELLOW/BLUE 367mm (14.45in) 6
KV6 with A/C YELLOW/WHITE 371mm (14.61in) 6
Models with sport suspension
(2004MY)
GREY/ORANGE 308.5mm (12.03in) 5.5