front and rear shocker selection

i've started looking at different types of shock absorbers and would like a little help in selection
their seems to be two main types either shockers that will take either 1.9" diameter springs or 2.25" diameter springs any preference on which is best most shockers seem to come with either single adjust bump and rebound or a twin adjuster
i,m looking at either gaz/avo or spax shockers i have measured the total movement on the rear suspension and it varies distance between centre to centre of shocker mount bolts of 7 inches fully closed and a total travel to 17 inch fully open i realise that the suspension will never travel this full distance but what length shockers are people using open and closed lengths the total travel on the front suspension is again from centre to centre closed to open is 9 inches to 15 inches
the questions i would like answered are
1. 1.625" bodys or 2" body
2. single or double rebound is double worth the money
3. sugested open and closed lengths for front and rears
4. what lbs/ins rated springs are you useing
i would like to thank you in advance for this rather long winded explanation and for everyones help so far
chris parker

Hi Chris,

Here are pictures of the Spax dampers & springs that are standard fit for GTD. The dampers are shown fully extended, the longer ones being the rear.

Hope you can get what you need from the pictures.

Regards,

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If these pictures are to small, PM me & I'll send you hi-res copies.

I thank you as well Julian. From the photos, I gather the front springs are 11" and the rear are 12". Both appear to be 2-1/2" ID.

The shocks appear to be 15" and 16" extended. Is that correct? What about springs rates for the front and rear?

Thanks

Bill D
Los Angeles, CA

Chris
Make sure of the travel available by measuring the travel at the shock mounts, wheel travel is always more unless you have a strut suspension. A good starting point is to have the shock 40% compressed at ride height, most shock specs will give you compressed, extended, and mounting heights so that you nay be sure the shock has enough travel for the setup you have. Alos, keep in mind that the ride height setup will also reflect on what spring you might use, if the shock is compressed say 2 inches at ride height and you are using a 400# spring then the shock is already supporting 800# and may be too long for your application. Another factor is that some shocks require the spring be compressed at assembly, and this adds a certain amount of preload to the shock even before you reach ride height. Fineally since it is a given that your shocks are inboard of the actual wheel center, the suspension has leverage on the shock, travel will be less than actual wheel travel, and you need a higher spring rate to compensate for this, The "motion Ratio" will allow you to pretty closely calculate what spring rates you need, and with a little fiddling you can tune the suspension rather well.
Good Luck
Phil