How To Add Rear Camber On 205 / 309 / 306

[ben25 0]

Someone have ask me about how I'm goning to add negative camber on my 205 this winter.

So I've take this on a french forum, I'll try to translate and explain it in a comprehensive english for you :

 

To have camber on a rear 205/309/306 axle you should have :

 

2 x 207 rear hub (from a 207 with rear disks ( around 40£ at peugeot ) Pics

8 x "conical screw" m10X150 with "flat head" 30 mm long, grade 10.9 or 12.9 (strong screw) Pics

3 x taps M10X150 Pics

 

Disasembly the rear pin axle from the trailing arm, and cut your pin axle at around 2cm like that :

 

After you should cut the existing form on the trailling arm to "plane it" , and you should re-bore , and use taps to convert the M8 for M10x150

 

Do the same for the 207 axle , rebore the hole to 12.5 or 13 mm and make 45° angle for the flat head screw.

 

A pic of the arm complete

 

This is finish : (here there is not any shims)

 

After you can add here (see pics) some clio 3 cup shims to add camber and/or toe as you want...

 

After : replace the 2cm stud pin cutted in his position to prevent from dust coming in the rear arm...

 

You can use 307/C4/207 rear calipers and disks, it seams to be the same (not sure)

 

When you add shims, the flated head screw are going to have a deformation, but a test has been done by a french guy who have 4° negative camber and it has been tested on a couple of trackday without any problem.

A pic to illustrate :

 

 

I hope It'll help some track lovers to do the same modification...

Edited November 22, 2011 by ben25

[Tom Fenton 1,542]

I don't like it. All the wheel bearing and weight being put into a small cast iron area originally intended to carry the drum backplate or caliper carrier.

 

Much better is to have the rear arms machined as per Bridgecraft/CRF450.

[welshpug 1,657]

is the cast arm weaker than a plate steel 207 torsion beam Tom? or even the clio item.

 

 

can;t see the reasoning for the cut off piece of stub axle

Edited November 22, 2011 by welshpug

[Tom Fenton 1,542]

No idea, still I don't like it. In addition I would have thought that the 207 has a spigot for that stub to locate on, so that the bolts only clamp it up, not support all the load as well. Even spotfacing the fixing points would be better than the loose fitting countersunk screws.

[Baz 421]

I don't like the countersunk screws not being 'home' properly, i'm sure it could be done a little better somehow? Edit; as above!

 

Chopping off of the original stub axle is just to use as bung for the holes left in the trailing arms, waste of a stub axle IMO!!

Edited November 22, 2011 by Baz

[B1ack_Mi16 67]

It might seem a bit dodgy, agree, but it ain't very much force this will see in a rather lightweight 205 at least.

 

Not sure what clamping force those bolts are up to, but if someone just could calculate the frictional capacity of the connection that would be interesting. Normally 0.25 is a ok friction factor to use on steel vs. steel contact.

 

I agree though that the 4 holes are supposed to take the braking loads only on their standard function, so it would be interesting to do a finite element analysis on the end the arm to see how stressed the metal will be. That cast iron is not the best to load up with rather high stress levels.

[ben25 0]

To resume this mount it is exactly the same principle that the rear axle of a clio cup :

 

And the idea to cut the old axle is just an option to make an easy "stopper"

[B1ack_Mi16 67]

Just some quick calcs.

 

Lets assume the M10 bolt has an effective OD (threads removed) of 8mm.

 

Area 16mm2.

 

Yield stress of bolt, 900MPa. That equals a clamp force at bolt yield of 14400N = 1468kg.

 

Lets say you only torque up the bolt to 70% of yield stress, then the force is 1027kg each bolt.

 

Set of 4 bolts will then clamp with 4110kg.

 

A friction factor of 0.25 will give a capacity of 1027kg

A friction factor of 0.15 will give a capacity of 616kg

 

Not sure how often the rear wheels see 616kg of load on track? On a rallycar I would be more sceptical though.

 

So unsolved issue would be the part of the 205 arm that it bolts to.

[allanallen 528 2 Cars]

Not my cup of tea either I'm afraid.

 

Once you've factored in the cost all the 207 bits (calipers,bearings,discs,pad,cables?),there's cheaper and better alternatives that bolt straight on.

[BlueBolt 156]

there's cheaper and better alternatives that bolt straight on.

 

 

Where and what?? ??

[Cameron 16]

Just some quick calcs.

 

Lets assume the M10 bolt has an effective OD (threads removed) of 8mm.

 

Area 16mm2.

 

Yield stress of bolt, 900MPa. That equals a clamp force at bolt yield of 14400N = 1468kg.

 

Lets say you only torque up the bolt to 70% of yield stress, then the force is 1027kg each bolt.

 

Set of 4 bolts will then clamp with 4110kg.

 

A friction factor of 0.25 will give a capacity of 1027kg

A friction factor of 0.15 will give a capacity of 616kg

 

Not sure how often the rear wheels see 616kg of load on track? On a rallycar I would be more sceptical though.

 

So unsolved issue would be the part of the 205 arm that it bolts to.

 

You're forgetting that you also have the bolts in shear, so the force it could withstand is equal to the frictional break-away + shear of the 4 bolts.

 

Each wheel seeing 600kg would be equivalent to about 3.5 x it's normal load (3.5g) and seeing 1000kg would be around 6 x normal load (6g). If you then factor in the shear strength of the bolts then you can withstand even more.

[SurGie 54]

Commercial M14 grade of bolts will be more than enough.

[allanallen 528 2 Cars]

Where and what?? ??

 

 

 

Bridgecraft trailing arms are re-machined standard arms that give 3 degrees of negative camber. They use the standard bearing,caliper+mount, disc etc.

We also machine and sleeve front uprights to give negative camber to your spec.

 

Pm CRF450 if your interested.

 

Al

Edited November 22, 2011 by allanallen

[Tom Fenton 1,542]

Commercial M14 grade of bolts will be more than enough.

 

Mis information.

 

Check out ISO898 part 1.

[welshpug 1,657]

Part 1 does not specify properties for fasteners that have head geometries that reduce the shear strength of the fastener, such as low head screws and countersunk heads. It also excludes set screws, which are covered under part 5.[2]

 

https://en.wikipedia.org/wiki/ISO_898

 

 

M14 isn't what was used here either.

[johnnyboy666 195 1 Cars]

surely it would be better, instead of countersunk, work out the angle of camber you are going to have and then have a flat recess at the correct angle and use flat seated bolts

 

that makes sense in my head, but is kinda hard to explain without pictures

[johnnyboy666 195 1 Cars]

and why not go 12.9 m12 or so just for peace of mind

[johnnyboy666 195 1 Cars]

here is an admitedly piss-poor atempt at explaining what I think is a better idea

[SurGie 54]

Ignore the M, i meant 14 tensile rating which is stronger than the 12.9. Thats if you can find a place that sells them big/long enough that is.

[B1ack_Mi16 67]

You're forgetting that you also have the bolts in shear, so the force it could withstand is equal to the frictional break-away + shear of the 4 bolts.

 

Each wheel seeing 600kg would be equivalent to about 3.5 x it's normal load (3.5g) and seeing 1000kg would be around 6 x normal load (6g). If you then factor in the shear strength of the bolts then you can withstand even more.

 

I know, but I like beeing conservative

 

and why not go 12.9 m12 or so just for peace of mind

 

That won't help much if there is not sufficient meat outside the holes in the trailing arm. So it could just as well weaken the connection.

[allanallen 528 2 Cars]

here is an admitedly piss-poor atempt at explaining what I think is a better idea

 

You can't start putting a shim on that side of the caliper bracket as you'll space the wheel bearing out. You could machine the angle onto the bracket itself but that will be a more specialist job which most people couldn't do in the garage.

[B1ack_Mi16 67]

Bridgecraft trailing arms are re-machined standard arms that give 3 degrees of negative camber. They use the standard bearing,caliper+mount, disc etc.

We also machine and sleeve front uprights to give negative camber to your spec.

 

Pm CRF450 if your interested.

 

Al

 

The good thing with the 207 and shim solution is of course that you are able to fairly easy actually adjust your rear geometry, which is not an option if you have the spindle hole re-machined.

[ben25 0]

I see that there are lots of reactions on this topic. That's good

Here in France a complete second hand rear axle of a 207 cost about : 150€ , so you keep disks, pads, calipers, hubs, and buy some shims and screws and it's ready to mount.

So it's a cheap alternative to KRZ or TRICompetition or machining rear axle solutions...

 

Remember :

-it's exactly the same mouting than clio 2/3 cup and furthermore on clio 2 cup the mounting is 2x m8 et 2x M10 screw who are used.. and there isn't any problem in race use.

-my drawing is an exageration of the angle, in reality to have 2,5 or 3° of camber (that a good value I think for racing use) the deformation of the screw head is very small and the 45° angle permit to catch up te gap.

 

(still very exagerated)

 

In France a guy have made these shims :

 

 

1.2mm on top and 1.6mm at the bottom (so the 4mm difference between to and bottom make a result of 4.5° of camber)

I admit that it is an extrem camber but with M10x150 flat head screws grade 12.9 (reputable "unbreakable") , a couple of trackdays after (on a 205 T16, 300+,slicks), there is no issue with this mounting.

(you can reduce these measurements cause in this particular case he has done a 1.6mm at the bottom to expand rear axle without using spacers (cause each of us know that spacers are not the better way for wheel bearings))

 

So they are two alternatives : use clio 3 cup shims or machine custom shims.

I advise everyone the second choice cause clio 3 shims are sold around 30€ per pair with a maximum of 1° of camber.. So to have 3° it means 3 pairs of shims so a significant increase in the cost of this modification.

 

So I recomand to make machining customs shims and to buy a pair of clio 3 shims 30' to add some toe in.

 

An other thing is that 207/307 rear pads are the same than clio 3 , VW etc. So you can source some race pads easily, (CL or pagid for exemple)

Edited November 23, 2011 by ben25

[Bas 6 1 Cars]

Ben, could you supply the link to the french forum?

 

Has anybody have this setup on his car?

 

Do you need the 207 brake caliper or does it work with the 205 caliper?

[Bas 6 1 Cars]

Will this fit on the 205?

 

http://boutique.citroenracing.com/product.php?id_product=3605