12 replies to this topic

[Ice]

Looks like no one has done it Terry

[WhiteA9XS]

 K frame will sag with heavy springs under racing conditions , Kent engineering in Melbourne reinforced one of mine , 3mm plate inside the lower part from top to bottom full length .

 

 I believe they unpick or grind the weld and bend open to get the plate inside . 

[Bigfella237]

Is it only the UC K-Member that does this or do they all need to be reinforced when fitting heavy springs/shocks etc.?

 

I thought the only difference was the location of the upper control arm mounting holes... are UC's made from thinner material as well?

[WhiteA9XS]

 Bigfella , the mod I got done was for an LX crossmember  ,  UC crossmember is very similar but I,m not sure about the thickness ..

 

 1200 lb springs and curb hopping will bend them under the sump , result = lots of camber ! 

[Bigfella237]

Thanks Shaun, very interesting...

 

I've been looking at a couple of K-Members and it looks like there's about six individual pressed sections that make up a member:

 

the main upper section (that bears the spring load);

the lower half (that the LCA's front pivot mounts to);

the two upper towers (that the UCA mounts to); and

the rear 'legs'.

 

It would be a lot of work to remove all the factory welds and separate the pieces and I reckon you'd have to make a solid jig if you ever wanted to get it back together in the right place, looks like there'd be a lot of stress on that top pressing as there's so many twists and turns in it.

 

What I was thinking would be easier is to cut a vertical 'slot' in the top and bottom of the main section (across the section under the sump), insert a profiled plate and re-weld the plate into the slot top and bottom?

 

It's only really the horizontal part of the K-Member that you'd need to brace, I doubt the vertical towers on either side would fail, or at least I think you'd be bending chassis rails and sheet metal before then.

 

I don't think it'd be real hard to do but you'd definitely want to talk to an engineer about it first, I know long straight continuous welds are frowned upon due to stress cracks but the only way to stitch-weld the plate in would be to separate the two halves, and even then you could only stitch-weld one edge while it was apart?

[Bigfella237]

While we're on the subject, I've been giving some thought to modifying the K-Member so the whole thing mounts into the vehicle up to an inch forward of its factory location, and then move the engine backwards on its mounts the same distance to its original position.

 

This would gain a slight advantage in weight distribution but would also extend the overall wheelbase, however a lot of that effect would be nullified by being able to increase the castor (possibly using UC upper arms) without the associated tyre to inner guard clearance issues on full lock.

 

I'd like to know exactly how far rearward the wheel actually moves between a zero-castor setting and a mega amount of positive castor, I reckon it might be more than you realize, even to the point where the wheel no longer looks centred in the wheel arch?

[WhiteA9XS]

 Andrew , you can get about 4 to 5 degrees caster on a stock front end with longer top arm bolts and spacers and at 5 degrees its starting to get hard to steer at lower speeds . I currently use 4 with a radial slick and its good .

 

 Have a talk to kents , they might let you know how its done , I,m sure they just peeled the lower bottom section open enough to put the plate in and stitch weld inside top .

 

Good luck   

[myss427]

Yes, I have strengthened mine by cutting off the base and running a 6mm thick plate on its side over the entire width. Then I made 6mm upright gussets (triangulated to plate) that ran inside, up to where the top control arm mounts are located. Finished it off with a 6mm base plate on the bottom, never sagged since, done this mod over 15 years ago!

[76lxhatch]

I'd like to know exactly how far rearward the wheel actually moves between a zero-castor setting and a mega amount of positive castor, I reckon it might be more than you realize, even to the point where the wheel no longer looks centred in the wheel arch?

Visually its not really an issue. I've managed to get roughly 6.5 degrees of caster, around 5.25 degrees is achieved with the shims and UC upper arms, keeping under the maximum of 0.5" with plenty of room on the standard bolts (I have two nuts on each). The rest is gained with an offset front bush in the lower control arm which brings the bottom ball joint forward a touch again, and also fixes the excessive negative camber for road use.

It does have some effect on clearance at the firewall though, especially if your have big tyres and its tight in that area already. But its not hard to make room if you don't mind a bit of cutting and welding.

You need a straight subframe to get the absolute most out of the shims, if you need to put much more in one side than the other to even it up then you start having to compromise a bit more.

[Bigfella237]

Thank you sir, any idea on where we can buy offset bushes? Do you happen to have the part number handy?

 

I looked on both the Whiteline and SuperPro websites and although both say offset bushes are available, they don't list them for either HQ-WB or LH-UC LCAs, but maybe I just didn't look hard enough?

 

(Apologies for hijacking your thread too Terry, I promise we'll get back on topic soon)

[76lxhatch]

I originally saw them listed on the old Noltec web site, these appear to be the same ones (rear trailing arms use the same items as front lower arms):
http://www.whiteline...t_number=W52491

The price was a bit steep for me and I wanted to stick with Superpro so I machined down some old IRS Commodore offset crush tubes and bored out some standard (90 hardness) bushings to suit:
http://www.gmh-toran...e-8#entry849759