Progressive Springs

Submitted: Tuesday, May 27, 2003 at 17:11
ThreadID: 5137 Views:1571 Replies:8 FollowUps:2
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Hi Guys

I have noticed on a couple of occassions on this site mention of progressive springs.

Could anybody explain how they work and what if any advantages they have.

I have a TD 100 series cruiser and the back end is somewhat soft, would progressive springs help out here without raising the vehicle beyond its factory height (insurance issues)?

Thanks in advance.PT
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Reply By: desert - Tuesday, May 27, 2003 at 18:55

Tuesday, May 27, 2003 at 18:55
Hi Paul. Progressive rate springs are a bit of a wank. They are merely a coil that has two or three coils wound closer together thus shortening the coil helix over a given length. This is supposed to make the spring have a soft and a harder rate in the one spring. More often than not, the closer wound coils simply compress together and you end up with a spring that has the top coils squashed together and the other, open coils doing the work. I have experimented with about 8 sets of front coils on my GU and have found that the progressives do not "progress" to the harder rate because the soft coils are bound together. In consultation with my spring maker, we have come up with a single would coil that rides soft as well as giving the lift I wanted. Most after-market springs offer increased lift by going to a larger diameter wire, which also increases or hardens the ride. I was not happy with this, so designed my own which offer the lift without too much increase in rate. Rule of thumb, as far as the after-market is concerned, if you want lift, then you have to go to a heavier coil to hold it up. I believe, my springs now do not follow this rule and have managed to get lift and keep the supple, factory ride.
However, if your 100 series has torsion-bar springs, then sorry, you are out of the game at this stage.
AnswerID: 21223

Reply By: Suzuki Viagra - Tuesday, May 27, 2003 at 22:25

Tuesday, May 27, 2003 at 22:25
I've used preogressive springs in the past without the troubles discussed here. The question is how much variation between the hard part of the spring and the soft part - some cheaper progresive rate springs are wound hard sof hard, where there's a huge difference between hard and soft. Better ones gradually change pressure down and then back up, or up and then back down.

He's right about standard afetrmarket coil springs. The best thing you can do is think about what you want to do, what loads you want to carry, do you want a towbar or winch etc then talk it over with someone who's prepared to listen.

I'm using 2" lifted Kings springs and they're just way too hard for on road use so I'm going to get my original springs reset the way I want them.
AnswerID: 21243

Reply By: bozo - Wednesday, May 28, 2003 at 00:17

Wednesday, May 28, 2003 at 00:17
I love the progressive rate springs that I fitted to my GQ, nice ride and still tows my racecar without the rear end sagging.
AnswerID: 21254

Reply By: Member - Michael - Wednesday, May 28, 2003 at 03:29

Wednesday, May 28, 2003 at 03:29
Progressive springs simply are usually a taperd coil of spring steel thinner at the top and getting thicker in the wire diameter down the wind or some manufacturers use less windings at the top more at the lower two thirds so you ride on the lighter less rigid upper part of the spring most of the time.The vehicle with normal weight compresses the ligher top spring but when weight is added eg trailer or camping gear,the spring is compressed further on to the thicker spring section.That is why its called progresive its used by most of the big manufacturers and works very well.This is only on coil springs as i know and most real four wheel drivers know leaf is the only way to go.Only kidding if i have not explained it clearly enough e mail me at i will see if i can find a diagram for you thats clearer.I posted a forum question about my anger at 100 series in particular about the saggy back end with headlights blinding me on country roads and yes this would greatly help.You can legaly have a raised height of 50mm.Your insurance co should have no probs with it.MikeGotta get out there. Debbie and Mike
AnswerID: 21259

Reply By: Member - Bill- Wednesday, May 28, 2003 at 11:14

Wednesday, May 28, 2003 at 11:14
Paul, for your problem you could also investigate "polyair" or "coil rite" air bags which fit between the original springs and give them varying rates of extra support depending on the load by varying the level of inflation. You in fact get an almost infite variable rate spring. They are well proven. Cost is around $350 and they are a DIY job for anyone with basic skills.Regds

AnswerID: 21276

Reply By: Hax - Wednesday, May 28, 2003 at 16:33

Wednesday, May 28, 2003 at 16:33
I also discussed this option with my mechanic and he basically said 'nice in theory but not so good in practice'.

He explained that if you are planning on predominately city road use then progressive coils will give a softer more comfortable ride when the vehicle is lightly loaded. All progressive springs will lower your ride height when you have any weight in the vehicle which means any lift that you were trying to achieve for offroad use will be sacrificed. Most people probably will have some load in the vehicle when they want to go offroad as all that gear adds weight.
AnswerID: 21292

Reply By: Hedonist - Wednesday, May 28, 2003 at 18:56

Wednesday, May 28, 2003 at 18:56

I had the same dillema with my 100 series - I specifically did not want a lift, just the ability to load up without the back end sagging. I settled on polyairs (and a set of OME nitrochargers) and my only regret is that I didn't do it 60,000 km ago...

AnswerID: 21306

Follow Up By: Member - Paul T- Wednesday, May 28, 2003 at 21:11

Wednesday, May 28, 2003 at 21:11

Did you replace the springs as well as add the polyairs or just add the poly airs?

How are the nitrochargers etc for ride both on ride & offroad?

What sort of cost for the nitrochargers?

Can you use an onboard compressor to inflate the polyairs or do you need more grunt from a garage compressor etc?

My cousin had a set of air units (not sure of what brand) and he had no end of problems with them.

Thanks and cheers

Paul PT
FollowupID: 13891

Follow Up By: Hedonist - Wednesday, May 28, 2003 at 22:06

Wednesday, May 28, 2003 at 22:06

I kept the standard springs. The nitrocharges were $600 installed + $400 for the polyairs, installed (ARB). I have only just had them fitted a couple of weeks ago but the difference in handling from the factory dampers is pronounced. :D

The polyairs operate at between 5 and 30 psi and are good for up to 400kgs of additional support. They can be pumped with a bicycle pump if necessary. In part I made my decision based on testimonials from other long term satisfied users (Especially camper-trailer / caravan types!)

FollowupID: 13895

Reply By: Member - Graham - Wednesday, May 28, 2003 at 19:37

Wednesday, May 28, 2003 at 19:37
It always comes down to some compromise, I had tried a set to replace the bow legged lineal ones, one trip loaded up it handled worse than before & went back and exchanged for lineal (couldn,t get better service) yes being H/D & lift when loaded works well & comfortable. It does pay to get guys who are prepared to listen. My 80 sits pretty level unloaded or loaded
My thinking is , every day, your only in the car for maybe an hour at a time but when away, your there for 2 to 4 hrs. when your out to enjoy yourself nothing worse than being nakered when you get there.
AnswerID: 21313

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