anyone want to get rid of there standard sports pack spring?

[Hail22]

Saying an engineer from fox racing is "hypothesising" might not go down to well... but yes, that is correct.



For a start, the bump stop is there to prevent bottoming out the damper. The silasto-type bump stops (basically foamed polyurethane)are what most OE manufacturers are moving towards, other than on leaf springs and specific chassis-mounted bump stops. Yes you are correct, the winding is a fixed rate until the last portion of travel where the spring helps to decelerate the piston in the damper/stiffen the ride on the compression stroke.

You are correct though Greg, if a spring is used that doesn't match the damper then it is going to decrease the life of the damper for sure and the reboud stroke is the bad one to try and have not matching because of the spring forcing the piston through the damper with more force than normal. BUT, this is only going to decrease the life of the damper if the damper overheats and aerates itself.

So in conclusion...Spring or Coilovers...I am sort of having a "cold war" moment here...whether to attack one option...or the other

[kaanage]

the winding is a fixed rate until the last portion of travel where the spring helps to decelerate the piston in the damper/stiffen the ride on the compression stroke.

this is only going to decrease the life of the damper if the damper overheats and aerates itself.

And here we have the essence of why the dampers can still fail with progressive springs - if Joe Racer installs lowering springs on his car (sorry ladies for the exclusion), it is more than likely that he will spend some portion of his time tearing about the 'burbs and twisties where the cornering forces will compress the springs in their OE rate portion.

So far so good. But as well as the cornering force loading, the springs also have to absorb mid corner bumps which are far from uncommon and this will often force the spring into the higher rate region where it is necessarily MUCH higher than for a linear spring (since we want the fully compressed rate to be identical to the full height OE spring).

In the compression phase, the damper actually has an easier time since the spring is deccelerating the unsprung assembly in conjunction with the compression valving. But the compression damping factor is far less than the rebound damping factor so the damper isn't working very hard in this phase anyway. In fact most cars used to have no compression damping.

When the spring rebounds, that higher rate section will expand first, trying to accelerate the unsprung assembly in droop and the rebound valving of the damper becomes overtaxed until the higher rate section is fully expanded and the OE spring rate takes over for the rest of the droop travel and the rebound valving of the damper operates at its designed flow. How long and often the damper operates in the overloaded state depends on how hard the driver is leaning on the suspension and how bumpy the corners are but it is in this range of motion that the flow rate in the rebound valving can become excessive, leading to cavitation which then aerates the oil and fades the damper leading to the overheating. The excessive flow also wears the valve assembly.

With higher rate linear springs, the dampers are always overloaded in rebound but at a much lower level so the dampers will wear but in a more predicatble manner.

So in conclusion...Spring or Coilovers...I am sort of having a "cold war" moment here...whether to attack one option...or the other

I still maintain that changing springs alone is a compromise that it not worth doing. Either change springs along with matched (or adjustable) dampers or go to a quality coilover - some coilovers have dampers that are no better or are actually worse than OE (which is why than can be so cheap vs springs + dampers as who would buy a crappy damper on its own?).

[PUZ213]

well all we can see from this thread is that there's a doubt in springs, but there's no questioning about installing coilovers. So I guess to be safe, coilovers, but if you wanna risk it, then springs.

[kaanage]

I'd say crappy coilovers are as bad as lowering springs alone.

[gavs]

When the spring rebounds, that higher rate section will expand first, trying to accelerate the unsprung assembly in droop and the rebound valving of the damper becomes overtaxed until the higher rate section is fully expanded and the OE spring rate takes over for the rest of the droop travel and the rebound valving of the damper operates at its designed flow. How long and often the damper operates in the overloaded state depends on how hard the driver is leaning on the suspension and how bumpy the corners are but it is in this range of motion that the flow rate in the rebound valving can become excessive, leading to cavitation which then aerates the oil and fades the damper leading to the overheating. The excessive flow also wears the valve assembly.

With higher rate linear springs, the dampers are always overloaded in rebound but at a much lower level so the dampers will wear but in a more predicatble manner.

Not true. Yes the spring rate is higher at the most compressed range of the spring, but how much higher is it, realistically and at this point, you're going to be on the bumpstops regardless. It is literally the very last instance of spring travel with the higher spring rate to stop the suspension from slamming into the bumpstop at maximum force. As i had it put to me 15 minutes ago, if you put 100kgs of extra weight in the car (like an extra passenger), then that too will effect the way your suspension works and cause premature wear. Running incorrect tyre pressures and having the wrong tyres, or different wheels, these to can also effect the performance. In my opinion and along with 4 other suspension engineers, you are not going to blow up your dampers or have them completely deteriorate overnight by putting in lowering springs, even progressive rate ones. in fact, the concensus was that putting in progressive rate springs (only in th erear) could be better for the car due to the potentially softer middleground of the spring which will give more better ride compliance.

Aftermarket dampers that are 100% perfectly matched to the springs you put in is the way to go, or linear rate coilovers if you're willing to spend upward of $1200 plus fitting. as kaanage said, cheap coilovers are just as bad or worse than unmatched springs.

My opinion, go with Eibach, h&r or KW lowering springs. If you're dampers wear out after 100,000kms, big deal. They're wearing out from the day the car gets put on the ground. Mot cars should have the dampers replaced at 100,000kms in normal city driving conditions regardless. The dampers in my golf were cactus at 80,000kms when I bought it because it spent most of it's first owners life on corrugated dirt roads.

[kaanage]

I guess we are talking about the degree of progression here - the scenario you speak of has the higher rate acting as a bump stop while all lowering spring kits that I have come across have either a linearly higher rate or the higher rate operates over a fair portion the spring travel.

Yes, if the spring operates almost all the time in the low (OE or less) rate region, then the dampers have an easy life and possibly an extended life if the rate is lowered vs OE. But this is very rare IME. YMMV
Check the pictures here http://www.eibach.com/prokit.html and here http://www.weitecsuspensions.co.uk/uk/sport_springs.php and this
and you will see that the higher rate portion of the spring travel (where the coils are more open) is MUCH more than just a bump stop aid.

[Hail22]

*brain farts*

Can we dumb it down for those who have had long days and want a simple cut version to assist in purchasing.

Sure when it comes to exhausts, wheels, air filters, body kits then I know a bit depending on vehicle etc.

However with this spring vs Coilover debate i'm begining to drift to the (AWWW BEEP IT! i'm keeping it standard).

Cheers

[gavs]

Sorry hail, I think that Greg and I are on the same path, just in disagreement regarding the specifics of the technicalities behind spring design.

In my opinion along with my colleagues, there is no drastically adverse affects associated with going to an aftermarket lowering spring. Go for it

[gavs]

Kaanage, yeah, without all the information of all the spring designers out there, there's a good chance you're right, but with all dampers, they have to cater for extremes in the operating conditions so I am sure that the stock dampers will have the adequate bleed controls to cope with higher compression/rebound forces related to drastic surface changes. If they don't, then it's pretty pisspoor on vw's behalf because even ford do it on the territory and that is a heap of crap car at the best of times.

[Hail22]

So KW, H&R, Eibach are the ones to be looking at/going for or is it all based on personal preference on the company/price?

Also should i look at buying a rear sway bar?

Regards