Looking through the photos of my old anthracite XK8 convertible I noticed that it has a pair of braces that run from the firewall area to the shock tower. I noticed the same thing on the XK8 and XKR convertibles currently in Bring a trailer. I'm using one of their photos because it is clearer to see what I mean than on mine. The XKR coupe does not have this.

I was wondering if fitting them on my XKR coupe would have any effect on handling? Can they be installed? I was also wondering about the aftermarket braces that cross the engine, but I don't think one like that would fit under the bonnet.

 

Great question. I'm looking forward to the discussion. My 98 convertible has the braces. Seems like all the serious suspension upgrades from yesteryear had the shock to shock cross brace, was looking at a 1965 Shelby GT350R engine compartment the other day - same thing installed.

Has technology outgrown them? Is it lack of space? Could it be its just not worth the effort anymore?

Thanks for posting Glandaniel.

John

 

In most unibody cars, the body itself takes the upper a-arm suspension loads. That would flex the chassis and affect suspension geometry.

Our cars use an independent chassis sub frame for the a-arm's, so those loads do not transmit to the chassis in the same way.

It wouldn't do any harm to add a brace, but don't expect it to suddenly taughten your suspension.

 

Coupes bodies flex less than OTS or convertibles.
I had a 1966 'E'Type coupe and my buddy had the OTS. My car would go around turns that would wreck his car.
He drove my car and then realized how stable the coupe was compared to the OTS.

Open the doors on a coupe, Look through the interior and you see an oval. A conv or OTS will look like a 'U'.
An 'O' is generally stronger than a 'U'.

The underside of the X100 Conv also has 'crossbars' and steel tubing links for strength.

bob

 

These can still be found in new performance car such as M3/M4 and the new GT350R. The F-type convertible have that same brace I showed in the picture above but not the strut tower to strut tower brace. The bimmers I mentioned have a carbon fiber piece that starts at one strut tower circles the periphery of the front of the engine and reaches the other strut tower.

However, the Corvette zr1, AMG GT, the Camaro ZL1, Hellcat, and many other cars lack them. Don't know why.



So, adding a brace would do little more than be eye candy?

I'm aware the coupes are more stable. I was wondering if adding the reinforcements convertibles have to a coupe would produce any further improvements?

 

If the parts diagrams are any indication retrofitting to coupe would certainly be possible but hardly time/ cost affective due to the complexity of the attachment method at firewall.
The torsional specs for the coupe have been published somewhere (can't remember where) and they are quite impressive, not sure any noticeable improvement would be had.

 

Those braces compensate for losing the roof on the convertible. Since the coupe has a roof, very little if any gain would be had by adding. In my opinion, the convertible could use even more bracing.

 

Yes, I remember the thread. I think I remember someone said that the torsional rigidity rivaled a Mclaren F1.

I agree. My coupe feels like a very different car to the convertible I had.

If it's too complicated to fit and would have a negligible effect than I think its not worth it.


What about putting the coupe on a diet? Has anyone done this?

 

 

So, where did you find the cross tower brace?

 

No help for you but when I searched high and low there are none for the 4.2, only 4.0.
wj

 

I bought this one HERE for my car. I have a 6.7L LS motor in there and it fits just fine. I can give you some measurements if you need them to see if it would work for you.

 

The only possible improvement for a convertible would be to add a full cage, essentially recreating a roof structure. It would then be better than a coupe as it has the extra convertible compensation structures much like years ago in the American market where racers looked for the convertible models with their box, perimeter frames and other body bracing already in place.

For a while I was considering a 2000-2002 XKR Convertible and doing the above in an elegant fashion to make it look almost factory. Perhaps one day.

 

I strongly disagree with that.
The x100 conv has a tremendous amount of cowl movement (shake)
This bar lessens it enough that it is noticable.
wj

 

I had a ‘67 Cutlass convertible which had a box beam frame while the sedan, hardtop and coupe had I beam frames. All 442s had box beam frames. That year the 442 was not a separate model but an option so you couldn’t tell from the VIN. Unscrupulous sellers would clone a Cutlass convertible into a 442 convertible.

 

My father purchased new a 67 442 2door hardtop. Bench seat with the Hurst Shifter. Elegant car. I grew up in that car.

 

Okay, partial hijack, but I'll stop with this post.
The 1965 4-4-2 had a 330 CID engine. The numbers represented four barrel, four speed and dual exhausts. After than went to 400 CID and 442 meant 400 CID engine, 4 barrel and dual exhaust as there were manual/automatic transmissions options. So if you had the four speed guess you could call it a 4442. I sold mine to fund by FFR Cobra build. Miss the car.

 

The first car I bought was a 1969 442 convertible with a 350HP 400ci motor and a Muncie M22 tranny and a 3.91 10-bolt posi rear end. It was Trophy Blue with a white top and a light blue interior I had the car 5-years and drove it everywhere. I really LOVED that car. But I do really LOVE my Jag as well so I am good to go I will have to dig up a pic of it.