Rear crossmember

[squiglyzigly]

I think the rear crossmember is an overlooked component that is easy to improve if you have access to a welder.
It’s a fairly flimsy open box design that I think should be boxed in like Lancia did on the Delta and Thema.
Seeing as the transverse tie rod links mount centrally it makes the flimsy design vulnerable to twisting under hard cornering. As well as giving the rear suspension a more solid base when cornering I think it can be easily modified to stiffen up the rear chassis a little, a bit like a lower strut brace.

I’ve already made one for my HPE but that is some way off of being driven.
So this week I had to drop the rear crossmember to gain access to the fuel pipes that have started leaking on my VX coupe and whilst I was there I decided it was time to strengthen the crossmember and test my theory.

So this is my freshly painted idea.

[squiglyzigly]

As the spare wheel well is only around 20mm above the center of the crossmember so I fabricated a small sturdy bracket that bolts the center of the crossmember to the spare wheel well.

Then bolt it all back up and give it a spin.

As expected car car felt significantly different. The immediate feeling was a bit like some kind of mass-damper had been fitted to the car. It feels more sturdy and better built. I know my car has a good rust free chassis as I’ve been under it for over 30 years (Not continually of course, I do come out for tea and beer) and purchased the car from a customer based on the condition on the chassis.
Then as I drove down the nearby roads admiring this new found sturdiness over speed bumps and pot holes I came across a roundabout.
Tip it in, squeeze the throttle and it digs in like a razorshell. It feels like the car has undergone a small all over upgrade.

All in all, I like it and there’s no downside.

[Nigel]

Hi again Ian,

Based upon your findings I'm sure I'll be doing something very similar to mine.

I like the additional centre support as well. The HPE probably has a deeper distance
to cover, but that's doable.

Cheers, Nigel

[WestonE]

Spot on Ian

This reminds me of John Followell trying to stop his rear cross member flexing. Which of course they all do.

Eric

[JohnFol]

I've been following with interest . . . . 

I have access to plasma cutter, welder and 4 post lifts etc. courtesy of this place
http://www.thisisyourgarage.com

Only caveat for me is fabricating the extra mount and strengthening brackets.

[squiglyzigly]

Hi chaps,
Since doing this on my VX coupe I have subsequently carried this out on my Berlina.
I decided it was easier to replace the fuel hoses on the Berlina with the crossmember removed so I killed 2 birds with one stone.  It was easy enough to leave all the outer suspension connected (car on axle stands) and remove the 2x long center bolts for the tie rods and drop the crossmember from its 4x outer stud/nuts on the chassis rails.
Before strengthening you can easily flex the crossmember back and fourth by hand whilst still bolted in place. After boxing it in and ‘without’ a center mount to the floor it is rock solid.
The first road test in the Berlina was much the same results as the coupe. Everything just feels more solid.
I’ve had this idea kicking around in my head for decades, just wish I had done it earlier.

Cheers Ian

[WestonE]

Hi John
 
May I recommend CAD. That is Cardboard Aided Design. Literally make the bits in cardboard i.e. cereal box with lines drawn for fold or cut. Version 3 seams to work for me most of the time. Those round pressed holes Ian is showing use a press tool you an get from Frost Restorations.

I like the idea the rental facilities and that looks like fun.

Eric

[JohnFol]

Yep, not too far and the guy is a bit of a classic enthusiast. Of course the on site cafe and pool tables help.

Not been there yet but my brother has with an assortment of cars. Tempted to say, if anyone is up there I might drop in to say hi

[JohnFol]

Did you also reinforce where the suspension arms bolt to?

[squiglyzigly]

Hi John,
No I didn’t reinforce the bolt holes. Didn’t see the point as I’ve never seen one cracked or damaged. I don’t believe it’s an overly stressed point that will flex or oval out unless the bolts aren’t done up properly.
I’ve seen plenty of cars that have been jacked up and subsequently the arms have bent, but still no damage.
Inside the crossmember I did weld the spacers in place to make assembly easier. And should the bolts ever seize inside (of course the bolts were reassembled with plenty of grease) it will be easier to remove them with the spacers securely welded.

Cheers
Ian