Jag IRS coilover setup

[Nick 427]

Hi guys.
Am setting up my suspension for an attempt at participating at the Nationals this year and at the moment am running stock jag coilovers.
Will be swapping over to adjustables with new springs.
Now for my question. Do I need to run 4 x coilovers or can you run just the one shock per side with the heavier spring and get away with it. Has this been done ?
Without issues.
Thanks in advance.

[Treeve]

It’s been done but the 2 shocks setup is part of resisting torsional loads through this suspension. I always recommend people stick with it instead of trying to fit one that’s twice the size.

[pormgb]

When I installed a Jag Rear end on my replica, I researched using one shock per side. As stated, it's not worth the risk to save money, although some Hot Rod builders go that way. Jag LCRs have lots of weak spots, and proper balance at the shock mount is critical.

[Gaz64]

Originally Posted by Treeve

It’s been done but the 2 shocks setup is part of resisting torsional loads through this suspension. I always recommend people stick with it instead of trying to fit one that’s twice the size.

Yes, fully agree, that is why they were designed that way.

The control arms don't have to fight against springs on only one end of the arms. Control arm bushes have no chance with only one heavy spring.

Gary

[dave295]

Great question Nick.

I won't even think of trying it based on the advice received above.
Cheers
Dave

[csx4995]

what spring rate is everyone using? I went with #350 and it'sa little too firm.

[Nick 427]

Originally Posted by csx4995

what spring rate is everyone using? I went with #350 and it'sa little too firm.

Thanks for the input guys. Looks like 4 new coilovers.
Re spring rates if you get on the Ridetech website they have a handy springweight calculator. Based on the weights and dimensions of my car it came up with 500lbs per corner. So 2 x 250lbs springs per corner.
It must be accurate as the shock supplier came up with the same spring rate based on the same info I supplied them.

[stephen low]

Nick

The advice above is no doubt accurate but there are plenty of Victorian cars that have had this conversion over a long time and I've not heard of any shock/suspension system failures.

It also has to be remembered that the cobra carries far less weight than the original Jaguar, perhaps this is a mitigating factor.

Anyway, my car's journey to date and I am happy with the handling and engineering.

Single adjustable shock with 400lb spring to rear of control arm. Original springs were 250lbs each.



Heavier drive shaft, double rose jointed training arm and adjustable lower hub to control arm adjustment. This combination made rear end alignment a dream



Inboard disc conversion to XJ308 outboard disc amendment with larger piston option. The car has significantly increased braking capacity as a result and no access issues to the rear brakes the inboards pose.



Anyway if you have build time, it would be worth a chat through the Victorian club on this option.

Cheers

[Bender]

Hi Nick. The rear arms look good. What brand shock are you using?
Thanks Neil

[Danr55]

If you are going to be accelerating hard, you will want at least 350# springs on all four. Anything less you risk rubbing the tires on the inside of the wheel well.

[Treeve]

If you go to outboard discs then you really need to consider going to the original two spring setup. By removing one spring you are forcing the bushes etc to carry all of the acceleration loads. Then with the outboard brakes you are now putting your torsional loads back through a single spring too. Jag engineers didn’t put two springs for a laugh and to make their cars more expensive. They did it because they understood the load paths in their design.

[CHANMADD]

You all missed the question. Is it ok to run one heavier spring per side. He did not say he was going to run only one spring ..just different rates.....Please read.In other words one stock Jag shock and spring and one adjustable per side.

[joyridin']

Originally Posted by CHANMADD

You all missed the question. Is it ok to run one heavier spring per side. He did not say he was going to run only one spring ..just different rates.....Please read.In other words one stock Jag shock and spring and one adjustable per side.

From his last post "Thanks for the input guys. Looks like 4 new coilovers."

Sounds like 4 instead of 2 to me!

[Nick 427]

After speaking to several shock companies the idea of running 1 adjustable together with 1 standard jag shock per side was not recommended.

(As far as running one Adjustable and one standard shock, this is doable, but it may be difficult when you’re trying to get tuning sorted out. If the standard shocks are progressive valving while ours are digressive, you may not be getting the ride you want out of them)

Anyhow I pulled the trigger on 4 coilovers and 4 springs.

Thanks for all the input.

[Donunder]

So, after all the research Nick, which shocks did you settle on?
I ask because my forty year old Jag originals are becoming a bit floaty and I'm also in the market.
The brand I keep hearing about are Vikings.

[Nick 427]

I looked at a few brands (AVO,QA1,Gaz) purchased Vikings.
I got a deal on shocks and springs from the Castlemaine Rod Shop.
Haven’t tested them so can’t comment on ride yet.