International2cvFriends.com :: View topic - �Negative camber on the back

Joolz wrote:

You possibly know better than me, but I had always assumed that it was just a case of bending the arms, and although any negative camber when the arm horizontal will be gradually converted to toe in as the suspension is compressed, I suspect the amount is negligible.

Now the science bit! :geek:

If a wheel has 2degs of neg camber when the suspension arm is horizontal, then it would have 2degs of toe in if the arm could be raised to vertical. Assuming that a race car has about 3" of suspension travel(that's a guess), and that suspension arms are about 40cm long(another guess, and excuse me mixing my units) then the arm rotates through about 10.5degs at full travel, this would convert less than 0.25 of a degree into toe in. I assume such a small amount has very little effect.

Cutting and welding the rear axel is probably more accurate, did you have any trouble bolting it back on, Spanners?

Author:	Russell [ October 2nd, 2009, 9:02 pm ]
Post subject:	Negative camber on the back
Probably a Q for the 2cv racing folk, I'd like some cool looking negative camber such as Hollis' car sports in the pic below: Now, my first thought was 'I'll make an arm bender and just bend them up, then make sure they are still in alingment'. Then, I realised this is a stupid idea, isn't it? If I just bend the arms it'll only be aligned when the car is at the hieght it's set to at rest when I bent it? as soon as the wheel moves up or down it'll effectively toe in or out won't it? so, is the arm bender tool that all the racing guys have purely there to straighten the arms after damage has occured, or do they also use them as I've described above, and does it actually work, or will it not make it handle bizarrely as the outside rear wheel will toe in under cornering? Is the only real option to cut the rear axle in the middle and reweld it into a shallow 'V' shape. I only wan't to do this because it looks cool, yes, maybe I'm a fashion victim, maybe I'm an idiot, but there you go.

Author:	Simon Crook [ October 2nd, 2009, 10:14 pm ]
Post subject:	Re: Negative camber on the back
I believe that we bend them a very little bit at a time, takes 3 to 4 people and takes a little time - the arm bender I have is very simple, wheel with an axle stand welded to it, then a scaffold pole - if I get a chance I will get the degrees of bend for you.

Author:	Russell [ October 2nd, 2009, 10:20 pm ]
Post subject:	Re: Negative camber on the back
So on your car the axle isn't cut and rewelded? IIRC this is a bit illegal in 2cv racing isn't it? I know it's common practice in Belgium though. Is yours simply the arms themself that are bent?

Author:	spanners [ October 2nd, 2009, 10:42 pm ]
Post subject:	Re: Negative camber on the back
My axle is cut and welded into a "V". This is permissable as I read it-there is no specified way of modifying the rear camber-it's "free" http://www.barc.net/competitors/regulat ... sVer02.pdf Just scroll down to the relevant bit.

Author:	Joolz [ October 2nd, 2009, 11:09 pm ]
Post subject:	Re: Negative camber on the back
You possibly know better than me, but I had always assumed that it was just a case of bending the arms, and although any negative camber when the arm horizontal will be gradually converted to toe in as the suspension is compressed, I suspect the amount is negligible. Now the science bit! If a wheel has 2degs of neg camber when the suspension arm is horizontal, then it would have 2degs of toe in if the arm could be raised to vertical. Assuming that a race car has about 3" of suspension travel(that's a guess), and that suspension arms are about 40cm long(another guess, and excuse me mixing my units) then the arm rotates through about 10.5degs at full travel, this would convert less than 0.25 of a degree into toe in. I assume such a small amount has very little effect. Cutting and welding the rear axel is probably more accurate, did you have any trouble bolting it back on, Spanners?

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Negative camber on the back http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=892	Page 1 of 2

Author:	Russell [ October 2nd, 2009, 11:17 pm ]
Post subject:	Re: Negative camber on the back
Joolz wrote: You possibly know better than me, but I had always assumed that it was just a case of bending the arms, and although any negative camber when the arm horizontal will be gradually converted to toe in as the suspension is compressed, I suspect the amount is negligible. Now the science bit! If a wheel has 2degs of neg camber when the suspension arm is horizontal, then it would have 2degs of toe in if the arm could be raised to vertical. Assuming that a race car has about 3" of suspension travel(that's a guess), and that suspension arms are about 40cm long(another guess, and excuse me mixing my units) then the arm rotates through about 10.5degs at full travel, this would convert less than 0.25 of a degree into toe in. I assume such a small amount has very little effect. Cutting and welding the rear axel is probably more accurate, did you have any trouble bolting it back on, Spanners? Thanks for that Joolz, in my mind while I was mulling it over today I'd assumed it'd be quite a lot more than that, although I'd like to go a bit more than 2 degrees camber, it still doesn't seem a lot of toe-in. I've also always wondered about how, once the axle is cut and bent, you get those long bolts back into it? perhaps you could cut the bolt and reweld the thread at an angle?

Author:	samfieldhouse [ October 3rd, 2009, 1:41 pm ]
Post subject:	Re: Negative camber on the back
sorry to be a dunce (again) but Russ, what am I looking for in that picture, I'm guessing negative camber is the wheels 'tilting' outwards or inwards?

Author:	Neil [ October 3rd, 2009, 2:02 pm ]
Post subject:	Re: Negative camber on the back
Sam, this is some fairly hefty negative camber displayed by this Lada Samara: also quite often witnessed on lowered air cooled Volkswagens.

Author:	Russell [ October 3rd, 2009, 2:08 pm ]
Post subject:	Re: Negative camber on the back
Yep, Neils picture shows it but far more pronounced than I want to achieve! Not as bad as this guy though...

Author:	Sean [ October 3rd, 2009, 3:59 pm ]
Post subject:	Re: Negative camber on the back
2 ways bend the arm or cut and weld crosstube Rambo had arm bending sesh at snet this year then broke its arm and cracks were appearing on the other one this was caused by having a brace to the back plate welded in and it became a stress point after the bend The other car that wasnt there this year has the cross tube cut and welded. If you stuck in at school you can work out the cut using triganometry to find the ammout to cut out at the top or as i did cut the tube grind out a clearance then place spacers under the bolt holes and stand on the tube to get the desired angles then tack, check, ajust and weld it closed my son did the trig for me as he is very good at maths think it was H= tan X* where x is the angle of camber and H is the ammount you want to lift the feet in relation to a fixed point mid way along the tube at BDC Paul Robertsons rule of thumb was "cut it with a grinding disk thats the right thickness" all fitted back on as its not really crazy angles were working with here. Lotus turned up to race one year and they had some mental looking geometry on their car cant remember how it did. Sean

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