not sure if it works the same as a golf/rabbit but if so then it would make it 105lbs front and 115lbs rear.
Sounds a bit light for a car this weight though.
See if you can get spring numbers fo others with steel suspension.
ie, if yours is a V6 then the V8 should hav harder front springs at 7L6 411 115 K for example.

 

not sure if it works the same as a golf/rabbit but if so then it would make it 105lbs front and 115lbs rear.
Sounds a bit light for a car this weight though.

Erm....no...

I have both... A Treg and a MkIV Jetta... The wire thickness of the Treg's coils are about double that of the Jetta. And the Treg weighs almost double. I broke two Mickey Mouse spring compressors the last time I removed the springs on the Treg.

I've got all the part numbers for the various springs used on the Treg (there are quite a few) but unfortunately no other info. You're right though, if I could get at least a starting point, that would help.

Where did you get the spring rates for the Golf/Rabbit from?

 

No, I did not meen that it had the same springs as a golf!
I ment that the last 3 digits of the part number are the rate of the spring.
Thats how it works on a golf and it might be the same for a treg.

Taking the part no. you gave above that would make the front springs 105kg/c.

Have a look at other part numbers for trucks of the same year but v6 and v8 etc and see if these 3 digits change but everything else stays the same?

Why do you want to know anyway? you want to lower it?

 

Oh!!! Sorry, my bad. Didn't even see that. I'll have a look at the other part numbers/applications and see what I can come up with.:dance:

The reason why I want it is a long sad story:

A year ago, I had a set of springs made because I wanted to raise the car about an inch. I took the springs out and gave them to a spring manufacturer to use as samples and told him I want the free length 30mm longer than standard, with the same stiffness. He made the springs and when I got them back he told me he also "reset" the old springs to the longer length. (I assume he heated them and stretched them a bit.)

Needless to say, I was a little p'd off about this because I wanted to have the original springs should I change my mind or something goes wrong, but I didn't throw my toys.

To cut a long story short, 3 of the 4 new springs sagged and the 4th one broke, while I was in the desert in Namibia, 300km from the nearest workshop!!! We made a plan and I managed to get back home ok and as soon as I did, I put the original springs back.

Now, 1 year later, they are also sagging...

I've now located a more reputable spring manufacturer and I'm going to try having another set made. The problem is that I can't use the original springs as reference because they're stuffed up and a new set of original springs will set me back around $600.

Luckily I took measurements of the ride height in all the various configurations I had, so at least I know where I'm going, but I'd like to give the spring stiffness to the supplier so that I hopefully can get the ride more or less the same.

I have various options now:
1. Buy original springs and fit spacers to increase the ride height.
2. Have a set of springs made to original spec and fit with spacers to increase the ride height.
3. Have another set of longer springs made.

I can have the springs made for around $200, but the question is, am I going to burn my fingers again? Don't know why I always end up digging a hole for myself...

 

right, you are going wrong with making longer springs.
To be fair to the original supplier, if you asked him to make springs 30mm longer and that is what they did then it's your bad that they havent worked. If you asked for ones 30mm longer they have basically made you a set that are the same as thesprings you had(when new).
If these are sinking they are not strong enough for your applaction.

What you need is stronger springs not longer.
To do this you would have to:
Mesure the length of the springs (that have sagged) while fitted to the truck. do this as they are now (fitted with your normal load on board)
Mesure the current ride hight and decidehow much you need to lift it by.
Have a look at the seats for the coils, do the springs go around the seats or inside the seats.

Now, send the springs and the info to the spring maker.
They will then need to test the springs on a compressor and work out how much stronger they need to be to get the lift you need.

For example, one rear spring is 400mm long when fitted and you want to lift the back of the car by 100mm. The spring may go out to 600mm when removed from the car. They will put it on the tester and squash it back down to 400mm. If this takes a force of 100kg to compress then, to lift by 100mm (25% of original) it needs to be a 600mm long spring that takes 125kg to crush down to 400mm.
To make one of these they will either use wire 25% thicker or 25% stronger.
Most places will go with thicker as stronger wire is more prone to snapping and gives a bouncy ride. This is why you need to know how the spring sits on the seat, if it drops over somthing and you make it thicker on both sides it won't fit. The guys need to know whether to keep the internal or external size of the spring the same as original.

 

I hear what you're saying, but I don't agree 100%. Like I said, luckily I measured the ride height every time I made a change.

I assume you have taken a look at the suspension setup of the Treg...? For the sake of those who haven't, it's a "coil-over" type setup, ie. the spring and damper is assembled together, so in it's "free" condition, the spring has a pre-load on it. It's very difficult to change the wire diameter because all the spring seats (top, bottom, front & rear) actually hold the spring on the inside and outside of the wire.

F=k.x for a linear spring (we'll assume this is a linear spring). The "free" length doesn't change, because it is determined by the length of the damper. So to fit a longer (30mm) spring in the same condition, you have to apply a bigger load to it. Since the weight of the car doesn't change but the preload is higher, the car sits higher. Whether you add a spacer, or fit a longer spring, the end result should be the same. The only difference I've realised now is that a spacer is probably more controlable. My initial assumption of 30mm longer spring wasn't too far off. When I fitted them new, it raised the car by 23mm (left front) and 26mm (right front). The rears were less (around 15mm) because the rear dampers sit at an accute angle. (Mistake No.1 on my side)

The car had 75,000km on the clock when I started messing with the springs. In this distance, the springs sagged on average 5mm compared to a new car. The longer springs sagged almost 35mm in 3 weeks and like I said, one broke. I asked for the same number of coils, wire thickness and spring rate, only longer. I cannot see how the springs could not be strong enough.

Secondly they've taken my original VW springs and stretched them 30mm. I've driven about 13,000km with them now and they didn't brake, but also started sagging. The car's ride height is about the same as stock in the front now and about 10mm lower at the back, so the rear springs are now SHORTER than stock. If the load is the problem, why didn't the original springs also sag 35mm in 3 weeks...? Heat treatment of springs is critical during manufacture and IMO, that is where the first supplier went wrong.

I agree with you that I probably need a stronger (stiffer) spring, but the reason why I shy away from this is because I don't want the ride to become harsh. Most of the aftermarket kits for 4x4's (Old Man EMU, Ironman etc.) use a spring with a higher spring rate, but this is because they assume most people want to carry bigger loads as well. The ride with the 30mm longer springs was the same as with the original springs. I couldn't feel any difference.

In any case, this is why I want the spring rates for the original springs. Then I can sit with the spring supplier and we can decide which way to go.

I basically had the same idea as you suggest with measuring the springs now. I'm going to measure the fitted spring length as is, then raise the car with a jack until the ride height is where I want it, and measure the spring length again. Then I can tell the guy: When the car sits on the spring the length is x. It should be y. If I have the original spring rates we can then decide if we can achieve this height change without changing the spring rate, or not. Or alternatively we can make a set of springs as close to the original VW springs as possible and fit spacers.

Hope this makes sense. Thanks alot for your inputs. It's nice to be able to pick a second brain. You're helping me out big time.

Oh, one more thing. I checked the other Touareg spring part numbers. All the front springs end with 105 and the rears with 115. Only the last letter changes, so there's no link between part number and spring rate, unfortunately.

 

Don't know if this is any help but your PR codes = the following:

0YA weight category rear axle weight range 1
0YB weight category rear axle weight range 2​

I think your front should be something like:

0JA weight category front axle weight range 1​

0JB weight category front axle weight range 2

Maybe your dealer can help more with what "range" would equal?

 

I think your front should be something like:

0JA weight category front axle weight range 1​

0JB weight category front axle weight range 2

Yip, sorry. My mistake. My Part No.'s & PR Codes are:
7L6 411 105 K (FRONT) PR-1BA+0JA
7L6 511 115 F (REAR) PR-1BA+0YB

For the '04 Treg, there are 7 different front springs:
7L6 411 105 K (1BA+0JA)
7L6 411 105 L (1BA+0JB)
7L6 411 105 M (1BA+0JD, 0JE)
7L6 411 105 T (1BA+0JF, 0JG)
7L6 411 105 S (1BE+0JA)
7L6 411 105 Q (1BE+0JB, 0JC)
7L6 411 105 R (1BE+0JD, 0JE, 0JF, 0JG)

...and 6 different rears:
7L6 511 115 F (1BA+0YA, 0YB)
7L6 511 115 K (1BA+0YC, 0YD)
7L6 511 115 Q (1BA+0YE, 0YF)
7L6 511 115 M (1BE+0YA, 0YB)
7L6 511 115 N (1BE+0YC, 0YD)
7L6 511 115 P (1BE+0YE, 0YF)

1BE is "sports-type suspension", whatever that means...
0JA-0JG is front axle weight range 1-7
0YA-0YF is rear axle weight range 1-6

hotponyshoes, you're right. You could possibly fit a slightly thicker wire by modifying the spring seats, but once again, I'd like to avoid that if possible. The front and rear setups are very similar, except that the rears are angled inwards alot more. The top mounts are basically next to the rear diff.

I'm at the bottom of the weight ranges, as I have an R5 with not too many weight adding options, so the easiest would've been to go up a weight range or two. Problem is my local dealer don't keep these in stock and I'll have to pay up front if I want them ordered and I've got no idea what difference each weight range will make. At $150 a spring this isn't really an option. Now, if I had the spring rates....

I do agree with you that the springs are overloaded and that's why they're sagging, but I still believe it's got nothing to do with the design or length of the spring. It all boils down to manufacturing processes and materials used. I don't carry heavy loads or tow a heavy trailer. It's normally just me and a bit of kit. The most cargo I've ever had in the Treg was less than 400kg.

If it takes a load of, say, 200kg to compleatly compress (bind) a spring you could make a spring a mile long and it would still only take a load of 200kg to crush it.

I disagree with this. If the spring rate is the same for the two springs and you put the same load on it, the compressed length of the longer spring will be more than the compressed length of the shorter one. The difference will remain constant, because k is constant. However, this does not necessarily apply anymore when the spring comes close to its fully compressed length. The material could come close to its plastic limit and start deforming. The theory also falls apart when the pitch of the coils are extreme, but for this case, where the long spring is only 6.7% longer I think it's still a safe assumption to make.

I do agree with you that I'll probably end up with a slightly stronger/stiffer spring. The question is, how am I going to obtain the extra stiffness. But I'll leave that up to the manufacturer.

Incidentally, the spring seats are common for all models with steel suspension, regardless of the weight range. This means that the wire thickness is the same for all. The only way they could change the stiffness is by changing the material structure with heat treatment, or by adding more coils.

 

Those will be the 3 digits that change then,
So, 0JA (weight range 1) could be a V6 and 0JB theV8.

If you have a V6 you could fit V8 springs to it. If you have a V8 you could be stuck as I think all V10's come with air suspension

Regarding the spring length, I see what you are trying to do but,
if your springs are sagging you are overloading them. period.
A spring has a memory,it always trys to return to the length it was when it was made. Now, under normal use a good quality spring, like the oem's you had first, will last for many many miles, like 300k+.
Problems arise when you take the spring out side of its normal operating range, ie, you over-compress it. The structure of the spring then distorts and it is not able to regain its original length.
This is why you got 75k out of the original springs and only 3 weeks out of the longer ones you had made.
As they were longer but no stronger the same load just compressed them further and weakened them quicker.
As you say yourself a linear spring will act equally to the load applied upon it.
If it takes a load of, say, 200kg to compleatly compress (bind) a spring you could make a spring a mile long and it would still only take a load of 200kg to crush it.
Spring length only depends on the reach of your suspension travel. 4x4's have longer springs so they can get over big rocks etc.

Sorry, but the only way around it is to up the strength of the spring to handle the load at theride hight you want. On the up side, if you put 500kg in the boot of your car and make the springs as above, the ride will be pretty damm closeto an oem ride.
The problem will be when you take the 500kg out of the boot, thats when you will get a bouncy ride.
If you are in the habit of doing this or towing somthing heavy regulary then a part-ex for a treg with air would be worth considering

 

Also, just had a look at the steels on a V6 petrol (2008yr)
You could make the springs thicker, on the front have them wound thicker to the inside of the coil. So keep the O/D the same.
The only things on the shocker are some bushes that locate the springs that could be turned down if they are not soft enough to compress into the spring.
The main function of these is for noise isolation so the only harm you will do is increase the noise of the car but I doubght you'd notice unless you where on a really smooth road.
Didn't look at the back ones as shes currently parked over a puddle!

 

Here's a pic of the front upper spring mount. The concept for all the others are more or less the same. As you can see, it's custom made for the wire dia. and you'll have to modify this to change the wire thickness.