A combined adjust for rebound and compression is enough, cause the main usage for the car is street use.
It will be good, if the housing of the shocks is aluminium, cause this is light weight and does not rust.
The springs can not be defined yet. First I have to measure the wheel load and do a little calculation - and not to forget to ask around for some hints from the experienced guys.
Discuss the measured weights and then define a Kg/cm ( or N/mm ) value, which can be tested will be the best way to get quite well setup.
What I actually know is, that I will need some helper springs. Using them has two advantages:
1. If you unload the wheel, the spring can not fall off the spring seat.
2. I do not want to use helper springs, which have only a few Kg/cm just to keep the main spring in place. The helper spring is much more dynamic than the big main spring. It´s block weight ( do not know the correct naming ? = Kg/cm x open length in cm ) should be set some kilo below the wheel load - so the helper spring will press down the wheel very fast if you drive over a bump in the road. This will result in a better control and less wheel spin if you have to accelerate on a bumpy road...
It took me a while searching for new shocks. The forum ( thank you MarcosGaza, TZ, and Super Charged gt400, ...) gave some good hints, so my favorite should come from England: AVO, Spax or GAZ.
The original shocks are not adjustable and have different length for front and rear.
--> I found a ebay shop named gaz-racing ( absolu_hzw6108ujom@members.ebay.co.uk ), who can offer every type of shock or spring from GAZ you like - to a really good price !
For example:
He offerd me
4 shocks GAZ gold pro + helper springs + main springs = 500,- GPB
4 shocks GAZ Gold pro + helper springs = 400,- GPB
I have ordered GAZ Gold pro 2,25", 2x 14" + 2x 15" open length + helper springs for 400,- GPB
The shocks are with spherical bearings (uniball) and with alu distances, which are fitting for the Marcos.
Even the inner diameter is 1/2" and not 7/16 as used on the Marcos. I have drilled the bracket of the frame to 1/2" and for the lower wishbone I made some alu distances with 7/16 hole.
About the spring rates
The normal GAZ package for the Marcos Mantula are
GAZ GP adjustable with 300lbs/inch for the front and 180 lbs/inch for the rear.
On an ealier car, the BMW M3, which had 1200Kg weight, I used a Bilstein shock with 300/300 ( rebound / compression) setup and 220 Kg/cm ( 1230 lbs/inch ) for the front and 180 Kg/cm ( 1000 lbs/inch ) for the rear.
This setup worked very well with normal street tyres and with slicks. OK - it was not very comfortable on the street - but cornering with it was awsome !
I can not compare these setup directly with the Marcos, cause the weigth of the car and the mounting postition of the springs are different - but I tend to go to much harder setup than GAZ.
My intention:
The car shall be carried by the spring and the shock is only to damp the spring.
With such a setup it is not neccessary to have a anti-roll bar in a street car. Mostly the anti-roll bar will be used to prevent the rolling over the lateral axis of the chassis, but exactly this shall be prevented by the main spring.
The anti-roll bar - if one is mounted - should be used for a fine, detailed adjustment to different tyres or asphalts or wet and dry conditions...
My goal for the suspension is ambitious - maybe I have to backpedal and start with a coplete new setup I will know after teh Marcos is in the street.
It is always a adventure to create a working suspension...
There is one good phrase by Pirelli, which still rules:
Power is nothing without control
To convert between the worlds:
lbs/inch X 0,1786 = N/mm or Kg/cm
Conversion table: lbs/inch ↔ N/mm (Kg/cm)
| lbs/inch | N/mm |
| 100 | 17,5 |
| 120 | 21 |
| 150 | 26 |
| 250 | 44 |
| 350 | 61 |
| 450 | 79 |
| 550 | 97 |
| 650 | 140 |
| 750 | 132 |
| 850 | 149 |
| 900 | 158 |
| 1000 | 175 |
| 1100 | 193 |
| 1250 | 219 |
| 1500 | 263 |
| 1750 | 307 |
| 2000 | 351 |
| 2500 | 439 |
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