jam996

I installed a set of JRZ RS suspensions, set the specs to gt3's and a good alignment as well. Handles great on highways, but as soon as there is any type of imperfection on road, there is metal knocking noise from front end.
Could it be the 2 springs setup?
On bumpy roads its as if all front end is loose, way too much noise.

Mike in CA

Mu experience is that this kind of thing is the trade off you sometimes have to deal with when installing performance or race type suspension on a street driven car. The idea behind the two springs is that one is softer to handle the initial bounce and provide a better street ride while the stiffer spring comes into play when there is more compression and you want more stiffness on the track. I don't know why there isn't some kind of insulator between the springs to prevent the springs from clanging together, if that's what you're hearing. A single progressive rate spring might also do the job assuming one will work with the JRZ setup.

mobonic

id check the pressures of the shock.. that does not sound right ( I have JRZ, RS pro's)

mooty

that may or may not be the issue.
BUT if you have main spring and helper spring, you need a bearing in b/n them so each spring rotate individually without binding.

JRZ is not something easy to DIY. you need a suspension guy to install and align it. and there are very very few guys who are qualified to do jrz, moton, ohlin and such.

if you want to do single spring, you need it all around, not just front.
also single spring will be less progressive thus harsher riding. i dont run helpers on my race car. but i wont even drive the race car in and out of the garage. i push it. it's brutal.

btw, the shocks and springs (helper and main) is not designed to bang against each other and make noises. your mechanic is not up to speed with jrz's, i fear. jrz with proper install and spring rate is dead silent and smooth on road and on track.

mglobe

+1

There should be a seat between the helper and the main. You can look and see if it's there. If it is not, that could be the problem. These should not make noise.

jam996

turned out to be sway bar links

jimack

I came across this thread and wanted to correct something that is wrong. A helper spring is NOT to provided any type of progressive spring rate, it's sole purpose is to prevent the spring from unseating when the suspension is in full droop. JRZ and other high-end dampers are made with lots of suspension travel, more so than the length of the spring. When your car is sitting on the ground, the helper spring is actually fully compressed and thus not adding to the spring rate.

Mike in CA

Your explanation makes sense. Thanks for the clarification.

rickgrande

I am replacing the KSport coil overs on my 996 C2 this week and replacing them with JRZ RS Pros. out of curiosity, where did you mount the rear remote reservoir so it is accessible in your non-race car?

Spokane5150

Shock Valving is specific to the spring rate, weight of the car and driver (Sprung Unsprung) and tuned to a preferred type of driving performance (Circle Tracks, Drag or Road Course). If you change springs then you'll need to re-tune the valving for proper performance. This JRZ system looks to have some rebound and compression dampening adjustments but it's typically only adjustable within a small window based on the valving perameters. Car suspension is a little different than motorcycles but tuning, re-valving shocks/forks for motocross on many dirt bikes for over 25 years gives me a little knowledge and incite into this process.

I suspect that your suspension has been installed improperly. You shouldn't have any knocking noises when hitting bumps. I had this same issue on an Audi that I installed new shocks and spring on and it was a Mechanic (me) error. I installed a spacer/washer improperly and in the wrong place so every time I hit a bump it caused a knocking noise.

I do agree with MikeCA that you compromise when you're trying to have the best of both Worlds; suspension for track or street. Example: In motocross suspension the Japanese designed progressive linkage with linear spring rates which is ideal for tuning. The linear spring rates made it easy to modify the valving and adjust dampening for different tracks. Interestingly, KTM went to progressive linkage last year because pro's and armature racers had difficulty tuning their progressive spring rate suspension. Our cars have progressive spring rates which I'm sure are difficult to tune compared to F1 and even the Carrera GT. Anyway, the springs are there to hold up the car and driver and keep the car from bottoming out. More spring rate for tracks and less for cruising down the road. It's the valving that changes the way the car performs on any given track and/or street but the valving is tuned to the spring rates as well. You guys that race probably set up your corner weight and tweak your rebound and compression dampening to improve performance on different tracks sort of like I did in motocross. These suspension guys use tons of science, trial/error data, FM and experience to tune suspensions with spring rates, oil viscosity, progressive linkage, progressive spring rates and valving.

So basically....don't go jacking around with the springs on an out-of-the-box suspension system or you'll screw everything up big time.

Porsche and other manufactures uses a simple valving adjustment when you hit the sport mode or suspension button. I think it is only a compression adjustment but I could be wrong.

911 Suspension


Carrera GT Suspension