SPAX to QA1 on a GTD. Part numbers?

[Eric Johnson]

Hi,
I'm looking to change out the Spax units on my GTD as they are really softly sprung. Looking to go to QA1 Proma Stars. Has anyone with a GTD done the same? Where did you get them and what part numbers if you have them? For spring rates, I'm thinking around 425 front and 525 rear.


Thanks for your help!

 

[Eric Johnson]

After doing a little research I found PN DR4855B for the QA1's.

QA1 Precision Products DDR4855B - QA1 Proma Star Coil-Over Shocks - Overview - SummitRacing.com

I'm assuming I can use them in front and rear. Now with the myriad of QA1 springs available, what spring lengths should I go with front and rear? The recommended length for the shock is 10". But would like to get the exact size F and R. Will getting the wrong size spring affect my ride height? My ride height is where I want it with the current SPAX units, but the ride is not firm enough when driven with gusto.

Thanks...

 

[Mick Ridley]

Hi Eric,

I dont claim to be an expert on spring rates, etc, but I do have a reasonable understanding of what is required, there are many people on this site , who will be able to go into a lot more detail, than I can, and hopefully they will contribute to this thread..........come on guys help Eric..........

Yes getting the wrong spring rates will affect the ride height of your car, If you keep the same Spax units, and want to make your suspension stiffer, then keep the same lenght spring, but use a stiffer spring. If you measure the diameter of the springs, and count the coils, with this information, a good spring supplier, will be able to recomend a stiffer spring for you

If you use new shocks, stick to themanufactures recomended spring lenght, as far as choice of spring rates goes, speak to the supplier, tell them what you have on your car, and they should be able to recomend the correct springs for you

You say your suspension is ok apart from when you drive with more speed, is it when you are cornering , that your suspension is too soft, if so , then if you stiffen your sway bar, this will reduce body roll, and give a stiffer ride, If your suspension is too soft all the time then harder springs are what you will need

I hope this helps,

mick

 

[Eric Johnson]

Mick,

Thanks for the help. The biggest problem is elevation changes. The suspension suffers on hills at speed. When you hit the bottom of a dip, it compresses then rises up and gets super light - Not confidence inspiring. When you go OVER the top of hill it gets too light as well. Needs to be more taught. Does anyone know the length of the stock Spax coils? That would save me some work!

 

[Fred/Belgium]

Eric,

I replaced my Spax with Protech Shocks.
Very good price/Quality

These are nice chaps and very helpfull.
FYI I ordered for front following part number: GT40 2.25 ID R/J (60 ukp each back in Aug 08).
Just give them a call: +44 1225 705553

Good luck

Fred

 

[Mick Ridley]

Eric,

It maybe that your damping is not hard enough, if your Spax shocks allow you to stiffen the damping ( mine do ) try that it may stop your car becoming light on the rebound, and compressing too much when you hit the bottom of a dip

If your shocks and sprigs are old, and worn out, then new shocks, and springs are the way to go
Im just trying to help you find a solution, without you having to spend lots of money...........

mick

 

[Scott Calabro]

E

Give me a call.

S

 

[Eric Johnson]

Eric,

It maybe that your damping is not hard enough, if your Spax shocks allow you to stiffen the damping ( mine do ) try that it may stop your car becoming light on the rebound, and compressing too much when you hit the bottom of a dip

If your shocks and sprigs are old, and worn out, then new shocks, and springs are the way to go
Im just trying to help you find a solution, without you having to spend lots of money...........

mick

Mick,
Thanks. Makes sense to check that first. The shocks / springs only have 5000 miles on them although the car is 10 years old. They look like new. Just sitting around can be bad for them as well I'm sure. I've come under the impression the SPAX's aren't that good from the get go from things I've read in the forum, but I could be wrong. The ones I have are the yellow and orange types...

 

[Mick Ridley]

Eric,
Providing your shocks arnt pitted and leaking oil, I would imagine they would be ok, but you can never be sure...
Modern shocks may well have damping which would cope better with your road coditions
Im sure you will be able to improve your ride. But eventually, you will find a maximum speed you can go throught the dips, because of the g forces you will create, and on the top of the hills you will reach a point where the car just takes off

Please let me know if increasing your damping improves things

Maybe you should start a new thread asking if anyone else has had the same problem as you going through dips , and over crests of hills

mick