Shock and Spring selection
 

Hi All,

I haven't been on the forum much lately as I have been building my shed (yes I will post some pictures soon I promise) amoung other things keeping me from working on the cobra.

I am probably leaving it a bit late but i need to replace my springs and shocks all round. I have an early RMC (1991) with Jag Front and Rear suspension.

I am also trying to establish whether I should go to single shocks on the rear?

1. To save a bit on cost.
2. Do I really need the twin shock set up? My only concern is that they were designed for two and will I be disturbubing the geometry etc.

In any case I would like to get some opinions on some shock and spring choices. I am leaning towards QA1 (Which Model have most people used?), Alden Eagle (Thanks Zedn), and Gaz Motrosport (There is a local dealer in my suburb). They all have enough response and height adjustment for me so it really comes down to a spring choice to suit any of these. (Unless someone has another option.)

So I guess my question is what spring rates have people chosen for front and rear? (I know this has been discussed before but i guess I am asking those with Jag front and rear setups similar to mine)

Any opinion welcome.

Cheers


Tony

Why do you think you need new springs and shocks ???
A nice cruiser ?
Semi comp ?
Fairly serious comp ? --- early RMC --need to check chassis torsional #s first

These guys could be a good start for springs and shocks :- www.gsad.com.au/ ;)

Hi Mrs Flatchat,

Rear end is now bouncing and has become very soft.... a lot more than it use to be and I have noisey shocks on both sides. May not be all of them but it is one of the areas I have not touched on the car since I have had it. The springs are second hand and are pitted (Particularly the rear ones).

The idea is to set up for cruise but have the ability to stiffen / soften on the track. I have had some good feedback on QA1's giving this kind of flexibility that I am looking for.

The GSAD site looks great and will explore some more options. Thanks for this.

Cheers

Tony

Hi Tony,

I have a late model RMC with Jag under both ends. Am running adjustable Spax shocks with coil over Eibach Springs. I am only running single 425 springs on the rear and 450's on the front. So far so good. It's going to be set up for street/competition when I do the final setup.
Baz.

Tony

I too would be keen to hear if you can run singles on the rear, it would certainly be a cheaper option. Do let us know any discoveries on this score.

Cheers

Spax with 8row transverse leaf...

Hi Baz,

Thanks for the info. 400 - 450lb seems to be the going rate for many setups and was keen to see what people used for single rear setups. I will have a closer look at the spax shock as well.

Cheers


Tony

Hi Tony.looking for that edge to beat me next year at the shelbyfest are we.I run koni shocks on my car but i think my spring rates are a lot lower than the figures you posted.Do you no your front and rear axle loads.

There are lots of us who would like an edge to beat you Keith.

My lack of ability would be the first issue to address...

Hi Tony,

I am happy with the build quality of the Aldan Eagles but unfortunately havnt yet driven on them. They are made in the US, have the same adjustability as QA1 and are about $200 cheaper. I have heard story's of them failing, but you never know whether they were installed correctly as poor allignment will kill them.

Make sure that when you are comparing spring rates with people that the mounting location and angle are identical. When i got my springs, i had shortened my control arms between the shock mount and the hub. I then changed my mind in the shortening method and shortened another set between the shock and the diff. The change in leverage of about 60mm made a massive difference to the spring rate. The springs that felt about right are now way too soft (they are 400lbs). The angle they are mounted at will also make a difference.

As for one or two shocks, there a lots of kit cars and hotrods running around with single shocks without any issue. But I have also had people tell me that they cant be set up right with one. I have gone with one on my car as i cant see how there could be an issue given that it is physically imposible for the control arms to rotate.

Good luck.

Tony,

I have single coilovers on the back - KPS115 600lb springs with adjustable avo's.

Tried some 800lb springs and it felt like a go kart at the back.

The springs I'm using certainle firms up the backend, but is not too uncomfortable on the ride.

Still need to do some work on the front - separate king springs with monroe shocks at the moment.

I tend to agree with Zedn about the angle by which the shocks and coil overs are mounted.

My original front shock mounting position on the RMC provided for an angle of about 60 degrees. We altered this by changing the top mounting position to vertical. This change now allows the front shocks to move up and down in a true vertcal plane providing for a far more efficient and smoother operation.


http://www.clubcobra.com/photopost/d...unt_Small_.jpg



http://www.clubcobra.com/photopost/d...ngs_Small_.jpg



Baz

Thanks for the replies
 

Hi all,

Keith, hhmmmm yes I believe I was short done by my rear end :LOL:. I'm chasing that 3/1000's I need :D. Probably need a little more grunt I think as well.

Peter, Thanks for your info. Looks like I need to do some measurements and do the calcs to get the springs I need. Thanks everyone for your time to reply it has been a great contrast of selection you have all done. It has got me on the path now I think.

Baz the mod to the front end looks great. I will consider this at some stage I think, it would be nice to have a little more adjustment. The RMC has some limitations that I have done some work to resolve already but not to the extent of yours.

Cheers

Tony

What is the weight of a RMC?

Mine is 1,242 kgs. It's one of the heavier kits around as it has a nice big, solid chassis.


Baz

Hi Rwillia4,

My RMC is 1160kg. I am not sure of the four wheel weights. I am going to try and get this done somewhere.

Cheers


Tony

Tony, this may help with springs.
http://www.box.net/shared/gcuutlsgbd

Springs & shocks.
 

Tony,

My RMC weighted in at 600kg front & 560kg rear, totalling 1160kg .
I have just been through what you are going through now.
I wanted a cruiser, not a racing car, so I wanted a soft ride for an oldish bum.
I started with some std s/h shocks on the front with approx 460lb springs.
On the rear I splashed out for new springs with GAZZ adjustable shocks on the rear.

This front setup was too low for licensing, so I had to insert 15mm spacers under the springs to jack up the front so I had at least 100mm clearance under the lowest part of the car. ( got 105mm at the frame under the engine./gearbox )

However, this was too rigid for what I wanted, as I could feel every bump and uneven surface on the road, but I left it at it was for licensing.

Then after licensing, I started to mess around, and bought another set of 4 s/h rear std Jag shocks/springs from the local Jag dealer for $100 the lot.

I decided to put the std Jag setup (4 x std springs/shocks) on the rear, as that is what it was originally designed for, and mounted them on the inboard mountings that are 15deg from vertical.

This sat the rear a bit too low for what I wanted, so I repositioned them all to the outboard mountings which are set at 9 deg. Height is now perfect.

Now to the front.

Took the GAZZ adjustables and mated them up with the 460lb springs without the spacers. Front mounting angle is 28 deg.

After a couple of adjustments on the height, ending at spring height setting @ 210mm, its now perfect, and the rebound setting is 6 clicks in from 0, and the rebound is also perfect.

The ride is now soft and doesnt shake the car like the harder ride did, and I can easily stiffen up the front if I want to by simply adjusting the rebound rate on the little adjuster knob.

Details of what I have fitted now, is below, and its perfect for what I wanted.

Pls take no notice of the colours, they just happen to be what colours I painted them when I cleaned them up, as the springs and rear shocks are all s/hand .

STD JAGUAR COILOVERS SPRINGS. (RED COLOURED)

MOUNTED ON REAR WITH STD JAG SHOCKS.

Free Length 270 mm
Inside dia 75 mm
Outside dia. 98 mm
Weight 230 lb ???
Wire size 11.5mm
Active coils 6.25
Loaded height. 210mm

Inboard locator position = 15 deg.
Outboard locator position = 9 deg

ORIGINAL FRONT SPRINGS (BLACK COLOURED)

MOUNTED ON FRONT WITH NEW GAZZ ADJUSTABLE SHOCKS.

Free Length 270 mm
Inside dia 80 mm
Outside dia. 108 mm
Weight 460 Lb ???
Wire size 14 mm
Active coils 6.25
Loaded height. 175 / 190 without 15mm spacer.

Angle of coilover assembly = 28 deg.

Spring height setting 210mm
Number of clicks set for rebound rate = 6
regards,

Graham.

Hi Tony

It seems unlikely that your springs have actually lost tension - there is good chance that they feel that way if the dampeners have failed.

I suspect that you'll get a lot more value out of just putting in new dampeners and spending (or not) the amount that you (might have) saved on springs instead.

I don't think it is necessary to have 2 pair of identical dampeners for the rear. I would be tempted to get one good pair and see if I could salvage a couple of the originals (are they rebuildable?).

Good luck

LoBelly

Hi Boxhead, Spreadshett is great will be using this to get my spring setting sorted.

Hi Graham, Thanks heaps for the information I will be using this as a baseline and will probably keep the spring settings I have but would like a bit more adjustment for the track.

Hi Lobelly, The issue I have is there is quite heavy pitting on two of the rear springs and two of the springs are shorter (ie two springs are shorter on the rear to adjust ride height). I have another set of springs and can probably make one good set but then i would like the abilitity to set my own ride height without using spacers. Thats also why I am looking for fully adjustable shocks.

Thanks everyone for the information I think i am now on the right path. Will let you know the outcome.

cheers

Tony