Bored the other weekend (rear beam triangulation).

You don't need to do either...I'm pretty certain.
By altering the mounting positions of the pick up points by no more than 30mm in any one direction you can have the tie bars clear the tank and exhaust on a lowered Mk3, with clearances of 5mm or so...Or so my calculations would suggest.

Problems with the basic design on a road leagal car are that the handbrake cables need to pass where the 'towers' are..so you need to move the towers a bit - alter the angles to give you clearance - the Kit Cars didn't have standard rear brakes/cables, the tie bars hit the tank underneath and the rear or the rear exhaust box...also you couldn't run an aftermarket rear ARB like the Eibach bar - not that you will need to!

The tank clearance can be gained by lowering the pivot point from the centre of the beam, by approx 30mm.
Not ideal...sure, and not as strong without work..so this lowered tie point then needs boxed in and webbed to give strength back to the area.

Problems with hitting the rear of the exhaust box / exhaust piping can be got round by moving the 'tower' pick up point as far forward as you can - not central as per VW, and fabricating the 'towers' 90mm 'tall'. This *should* give 5mm clearance to the inner rim of the wheel (16" BBS RXII wheel), 5mm clearance to the exhaust box, 5mm clearance to the tank on a low Mk3.

Of course..only time will tell whether a morning spent with a tape measure, lengths of tubing, rulers, tape and rose joints will all work out...

 

I can see that when running super sticky tyres, the rear beam may deflect...which I don't want, in line with what you say above.

Having the tie bars go straight back, not on towers, should stop any toe changes...and strong box section turrent should stop combined toe and camber changes...so I'd rather stop any unwanted changes where possible...then set the static camber / toe to give me the characteristics I want under full load.

Time will tell, I guess..

As for rear beam angles...I prefer toe out at the rear and some negative camber. I trail brake a lot, and find very slight toe out helps throw the rear round.

 

Just me 2 cents about this thread.
For those who don't know I used to weld 300ish beam axles a day at toyota.
Very similar design to the mk2 golf axle.
There was a thread on vortex a while back about plating the gap between the top and bottom of the back edge of the beam.
My opinion was that was dumb, the reason being that the angular stress absorbed by the beam would instead be absorbed by the welds connecting it to the axle arms.

I like ideas like in this thread because they add rigidity to the axle while taking stress away from the beam to additional metalwork.
The only thought I would add is stiffening the middle of the inside of the beam.

 

looks nice that. you should start selling them.
i was going to make one but.......
couple of questions tho.
what backbox do you have and do you have a standard fuel tank?
these are the couple of things that didnt measure up when i looked in to it, and it wouldnt go on
hopefully your answer may tempt me to get the welder out again

 

It is a nice job but I'm not convinced its needed - its unsprung weight also so important - they were fitted to Golf Mk2/3 rally cars that like hitting grass banks and as such, these tie bars would stop the axle bending - but they werent fitted to the Evo 1 Ibiza's....which were developmentally superior to the golfs. And they were not fitted to some GpA circuit golfs either. Go figure.

 

Bill you are right, the Lupo did run with these, and they did work. As you rightly say, the first set did get bent which proves they are doing something, and it was these stiffeners that transformed the Mk5 Diesel of Mike Neuhoff from top 5 runner to race winner in 2002. Our second generation of the tir bars were a different ball game...they were never going to bend :-)

There is some nice fab work in those pictures, but I would be careful about those rosejoints necking out when the beam twists...they look like they have almost run out of travel in one direction already....also there is a problem with the axis that they are working in because as the beam twists they will try to lengthen and try to force the trailing arm outwards which may bend the rods or break something.

I would like to experiment with a damper in there instead to damp the passive rear wheel steer instead of stopping it.

 

Oh and we were on road tyres in VW Cup, not slicks.

 

No backbox on my car and the fuel tank sits where the spare wheel well used to be

 

that would explain that then.
thanks.

 

VW used to have some plate at the centre point, possibly just to mount the bracket on, but possibly to reinforce.

There are definitely two schools of thought on this. Agree with the rally usage being to strengthen, first and foremost.

Vortex used to see arguments for and against on circuits.

Then there were beam strentheners pictured on this thread here (post 6) which seemed to exist instead or possibly as well as the tie bars. Could be a regulations thing - who knows?

The Ibiza kitcar Evo 1s didn't have the cross brace on the rear axle, but IMO that car was far less developed than the mega Evo 2 back axle. I have seen evidence that there were strentheners on the rear trailing sections of Ibiza Evo 1s though, similar to those on the linked post ^^.

IIRC, John Quartermaine's ex-Sorg Motorsport DTC yellow Mk3 Golf from the VW Cup had the rear stabilisers, yet others didn't.

VW UK definitely put them on the Neuhoff Mk4 Golf TDI - there's an article in CCC / Race Car Engineering or similar documenting it all - from around 2002.

For race use, all down to driver preference I suspect.