IRS Springs

[Migge]

BTW I know many guys just running one coilover each side.

[StuBaker]

Hmmm, interesting. Is that Hawks?

[Migge]

I know guys with RAMs and DAXs running just one per side.

[cobraboy]

interesting. Is that with two dampers and one spring, or one spring, one damper ?

[StuBaker]

Some of the Hot Rodders in the US use one spring at 500lb.
I guess damper calculations are even harder? If you have one damper doing all the work will it get hot?
Also found some info on bounce frequency... oh no!
Got my shims and nuts today so will start assembly this week.
Made a camber gauge from 50mm ally angle with a plum bob. 1/4 degree is 2mm at 460mm radius so should have reasonable resolution.

[Michaels Garage]

Did you eventually come up with a solution to the ride height?
With my Hawk supplied shocks wound as low as they go, the car still sits too high and the springs come loose when jacked up.
I’ve tried removing one spring from each side and keeping 4 shocks and the car does sit lower with the spring properly located and not rattling loose, but are they possibly under too much load, they look too compressed.
Also it still doesn’t sit as low as I’d like it too.

Is the solution a longer springs with lower load rate or shorter shocks and springs?

[StuBaker]

Not yet I'm afraid, only got the IRS back in last week.
Just waiting for some screws to fit in my new (used) seats before I put back the exhaust and get her on the floor.
I have noticed however how close the n/s forward spring is to the chassis rail now. I can't understand why. Yet.
I'm now thinking 2" dia springs now to get more clearance.
I wouldn't fit shorter shocks as you'd restrict the range of movement. But it's not yet something I've considered. I'm looking at longer lower poundage springs. E Types had approx 10" 250Lb springs and are heavier than our cars.
Please note I am not a suspension specialist and I am only going on personal research on similar IRS set ups in the UK and the US. I'm sure you aware that altering spring and damper rates may upset the balance of the car adversely.
It is my unverified opinion that the 4 springs should be 9", 250lb. to give the ride height I require. I believe, looking at the E type service manual, that correct ride height is when the drive shaft is parallel to the ground. This may not be visually correct for the Hawk but I haven't yet measured that.
If you have 4 x 400lb 8" springs the same as mine I'd expect a single spring to compress to about 5". ??
So you could probably jack it up but it would be nearly coil bound?
Anyway, I want to get mine on the ground and set up camber then look at the springs. In the absence of any hard facts I'll talk to Gaz directly.
New 2" coilovers will be a £600 investment I think so needs to be done scientifically.
OR single 9" spring at 500lb - more economical trial.
I'd leave both dampers in though.
Hopefully I'll have her all together this week.

[simonjrwinter]

I ended up with 500lb springs on the back of my last Hawk. The standard (350lb?) springs enabled the outer U/J to kiss the chassis on big bumps (I’m a big chap so that didn’t help) I tried 400, before settling on 500lb springs. Incidentally, even with much harder than standard springs, the car rode beautifully and certainly wasn’t “over-sprung” (is that a word?)
THT, who sold it for me, remarked it was possibly the nicest driving Cobra they’d ever driven…….and they’ve driven a few!

[cobraboy]

I have the following springs for sale if it helps anybody.
Used for set up only.
1 pair 2.25" ID x 9" x 500lb £20.00
1 pair 2.25" ID x 10.5" x 550lb £30.00
1 pair 2.5" ID x 9" x 500lb £30.00
All plus shipping.

[cobraboy]

I have the following springs for sale if it helps anybody.
Used for set up only.
1 pair 2.25" ID x 9" x 500lb £20.00
1 pair 2.25" ID x 10.5" x 550lb £30.00
1 pair 2.5" ID x 9" x 500lb £30.00
All plus shipping.