Ideas For Improving Rear Suspension...

[Guest Nuno205Rallye]

Don´t know if someone already posted these images over here, but here is what the French Tuners are doing for the rear suspension for Race/Rally aplications.

 

 

 

I've read posts from many people asking how to reinforce lateral support for the rear suspension arms.

 

This is what KRS Competition does for the 205 Rallye Evolution :

 

 

Notice the thick plates between the arm and the wheel hub location?

 

Its a Camber ajusting wheel axle (stub pin?)

 

 

Here is one for the adjustable ARB (notice they welded the axle to the arm):

 

 

Here is a picture for the modified rear beam tube to take the triangulated lateral reinforcements and the (outside the tube) adjustable ARB:

 

[hengti 2]

looks well engineered

 

looks rather expensive

 

 

just out of interest - what sort of benefits do they claim do you know?

[Rippthrough 98]

All that and still the cast arms.

I would have fabbed up some ally items to start with

 

That and sorted the damper/wheel movement ratio

[Jonmurgie 2]

suck me sideways, that all looks sooooooo damned nice must cost a packet though!!

[pug_ham 240 3 Cars]

All that work & still using the Torsion bars, why not go to coilovers instead?

 

A quick google for KRS Competition came up with a picture of a nice front subframe with tubular lower wishbones & the ARB bolted directly to them.

http://fullpowerteam.superforum.fr/ftopic7...TCT-ACAV-RS.htm

 

Graham.

[Sandy 189]

Alot of competition regs insist that the original spring arrangement/type is retained. Even on "Evolution" or "modified" class cars.

 

The way people get away with coilovers here, is by retaining the torsion bars, either connected or with the splines ground off one end.

 

The thing that bother me about that set up though, is the massive perforation of the cross tube. All that trouble with the brace and it will surely flex the tube instead of the arm? The inner bearings now being in a weak area.

Edited March 18, 2006 by sandy309

[niklas 1]

Flex in the arms is not as bad as it sounds!

When you load the car really hard, you get a lot of lateral weight transfer which leads to the outer rear arm flex inwards which will give the outer wheel toe out.

And if we have an increasing toe out on the rear wheel that takes most (all!) of this weight transfer then we will have our all-so-desired oversteer!

 

What is a lot more interresting for racers is the adjustable arb, as a normal tarmac setup is a lot harder to drive in the rain.

[pug_ham 240 3 Cars]

Alot of competition regs insist that the original spring arrangement/type is retained. Even on "Evolution" or "modified" class cars.

 

The way people get away with coilovers here, is by retaining the torsion bars, either connected or with the splines ground off one end.

 

The thing that bother me about that set up though, is the massive perforation of the cross tube. All that trouble with the brace and it will surely flex the tube instead of the arm? The inner bearings now being in a weak area.

Yeah, I wasn't thinking straight in the early hours of the morning & forgot about the fact that they probably couldn't modify it to that extent & stay in the same class. I've also heard of people running coilovers keeping the TB's but with one end disconnected in some way like you describe.

 

As for the design, not sure it would weaken the cross tube that much as its all machined properly but it does open the inner bearings to the elements. Maybe they've found a better sealed bearing to replace the current style with.

 

I'd like to see it up close & see everything in practice though.

 

Graham.

[Sandy 189]

Try bending a pipe, then cut big holes in it like that, and try again. You'll see what i'm getting at.

[Butler 0]

Doesn't one of the 206 models come with that bracing as standard, maybe the SW, sure i have seen it before.

 

Love the adjustable ARB

[tom_m 0]

Notice the thick plates between the arm and the wheel hub location?

 

Its a Camber ajusting wheel axle (stub pin?)

 

 

i think this little lot is simply a rear track increase, there doesn't appear to be any additional camber on those blocks, and the stub axel wouldn't be straight if there were, would it? its gaining additonl width on the rear without spacers or the 309 beam.

[niklas 1]

Doesn't one of the 206 models come with that bracing as standard, maybe the SW, sure i have seen it before.

 

Love the adjustable ARB

 

Yea both 206 SW and GTI180 have the "toe control arms"

[base-1 17]

All that and still the cast arms.

I would have fabbed up some ally items to start with

 

They're rallying though, ali shatters and ends the event right then and there, whereas steel bends so you can at least drive back to service

[pug_ham 240 3 Cars]

Try bending a pipe, then cut big holes in it like that, and try again. You'll see what i'm getting at.

I already know what you are getting at but its cheaper to have a built in weak spot if you catch a rear corner that twist a shell if its to stiff.

 

Although you can't exactly tell from those pictures I don't think the slot is machined in any further than 1/3rd of the total centre tube diameter, certainly less than half & if done with the correct research (which I'd hope they've done) it shouldn't weaken it very much at all imo.

 

Graham.

[Sandy 189]

The idea that that perforated tube will flex less than the standard cast arm, I find very dubious. If the tube was braced to the floorpan near the inner bearings, i'd be happier.

[Rippthrough 98]

They're rallying though, ali shatters and ends the event right then and there, whereas steel bends so you can at least drive back to service

 

Cast steel vs fabbed ally?

I'd take the ally.

[Powers 13]

A complete Maxi f2000 beam as shown in the picture is £1900 plus the carrage and taxes.

The ally blocks and longer stub pins are used to widen the track, more than a 309. However most F2000 cars utilise the 306 beam, which is allowed in the regulations.

[Guest Nuno205Rallye]

i think this little lot is simply a rear track increase, there doesn't appear to be any additional camber on those blocks, and the stub axel wouldn't be straight if there were, would it? its gaining additonl width on the rear without spacers or the 309 beam.

 

 

 

The way to adjust camber is inserting a metal gasket between the arm and the machined block that you see in the pictures.

 

It's a solution taken from the Renault Clio 172 Cup Car. The 172 has got the stub axles bolted to the suspension arms by 4 bolts in a square arrangement, there is available from RenaultSport sets of these gaskets that range from something like 0,5mm slim side/ 1,0 mm fat side and so on...

 

 

That way you can adjust the rear camber (and also toe in) by replacing the gaskets. When I had my Clio 172 I had various sets of these gaskets

 

The cut out tube will not flex whatsoever, because of the torsion bars and the (now mounted outside) ARB serve has an efective reinforcement to the tube. If you bent the tube, you would have to bend the torsion bars and the ARB.

 

As a surplus, the Body is reinforced with a 2mm stell plate moulded and welded where the rear beam bolts on to.

 

For a road car, or even a Track car, I would not go so far down the road. Rallying is a different matter, from one stage to the other conditions may change enourmously, that alone justifies such an amount of adjustement.

 

Here are some more pictures for the front suspension:

 

Front subframe seam welded

 

 

Complete front subframe with tubular wishbones and ARB directly bolted to them:

 

 

Machined front pivots:

 

 

 

Tubular wishbone

 

[Powers 13]

All the parts Krs sell are very high quality, unfortunatly the prices are extorsionate! For the price of those wishbones you could by a 306 gti-6, puts it into comparison.

[Rippthrough 98]

All the parts Krs sell are very high quality, unfortunatly the prices are extorsionate! For the price of those wishbones you could by a 306 gti-6, puts it into comparison.

 

 

I know rose-joints aren't cheap but christ!

A bit of tube and some welding + tapping.

[Anthony 1,000]

They're rallying though, ali shatters and ends the event right then and there, whereas steel bends so you can at least drive back to service

The standard cast arms will snap rather than bend if you hit something hard enough, namely usually fast sideways efforts into curbs (seen the results a few times, and I think Cybernck did it on his competition car a year or so back?)

[Sandy 189]

The cut out tube will not flex whatsoever, because of the torsion bars and the (now mounted outside) ARB serve has an efective reinforcement to the tube. If you bent the tube, you would have to bend the torsion bars and the ARB.

 

Really? The torsion bars are continually in bending as they aren't on the same axis as the arm pivots and being made of spring steel, the offer resisitance sure, but aren't "stiff". The ARB offers no bending resisitance of any value. I'm no rocket scientist, but i'm of adequate experience to see the bending resistance of the standard cast arms being greater than the perforated tube. My experience of Spars on sailing yachts has taught me how important it is to maintain the wall integrety of a tube in bending. That set up puts all the lateral force into a twisting moment on the end castings of the axle, if the torsion bars did offer the stiffness in the way you describe, the bending is back into the arm again! the only tangeable benefit i can see to that arrangement, is to resist the de-cambering of the trailing arm by twisting, which is a dubious benefit against how much the cross tube is weakened and loads in the end castings increased. The geometric stability of the axle is quite possibly as bad or worse than original.

Edited March 21, 2006 by sandy309

[Guest Nuno205Rallye]

Really? The torsion bars are continually in bending as they aren't on the same axis as the arm pivots and being made of spring steel, the offer resisitance sure, but aren't "stiff". The ARB offers no bending resisitance of any value. I'm no rocket scientist, but i'm of adequate experience to see the bending resistance of the standard cast arms being greater than the perforated tube. My experience of Spars on sailing yachts has taught me how important it is to maintain the wall integrety of a tube in bending. That set up puts all the lateral force into a twisting moment on the end castings of the axle, if the torsion bars did offer the stiffness in the way you describe, the bending is back into the arm again! the only tangeable benefit i can see to that arrangement, is to resist the de-cambering of the trailing arm by twisting, which is a dubious benefit against how much the cross tube is weakened and loads in the end castings increased. The geometric stability of the axle is quite possibly as bad or worse than original.

 

 

If you bent the tube, the distance between anchorage points in the torsion bars and the external ARB would change.

 

Unless it would be a large enough impact, I'm not seeing possible to flex the tube, flex both torsion bars and at the same time strech one and compress the other. The force vector exerted by the suspension arms is in the same plane has the torsion bars. The torsion bars do not flex in normal suspension travel (not a large amount) they do however (and has the name suggests) twist.

 

And believe me, the 205 body will bend much much sooner than the rear beam tube does, even in this cut out form.

[Sandy 189]

I'm not talking about impacts, i'm considering the lateral loading on the wheel transferring to the arm and bending it (or twisting it?), in relation to the horizontal moment the arm would transfer ultimately to the tube by way of that triangulation arrangement. The torsion bars aren't only twisting, they're bending as well because they're significantly offset from the rotational axis of the arms. And in such a situation will only offer a nominal resistance on the horizontal plane, as they're already distorted. The ARB can't offer any meaningful resistance to horizontal bending of the crosstube at all.

[pug_ham 240 3 Cars]

The section of the beam where the cut-outs are made is inside of the body mountings for the beam so it would have to be a serious impact to bend the tube even with these cut-outs imo. The shell would be beyond use if you managed it imo.

 

Graham.