Even with the extra camber eccentrics I've only ever been able to get about 1.5 to 2 deg neg camber on Jezebel, and I really wanted more.
I'd seen a few posts on here about bending the top torsion arms on a BJ beam to get greater neg camber.
There was no real info on HOW to do it tho on here, stf, samba etc., and asking direct questions hadn't gotten my much either... so I just decided what the hell - time have a
crack.
Here's how it went if anyone's interested...
Step 1: Do some maths.
At it's simplest, the way the steering knuckle mounts is basically this. (drawing not to scale, but the measurements are good. Obviously the top and bottom rectangles are where the ball joints mount into the arms).
I wanted to add about 4 degrees of neg, which high school maths (Sin = Opposite over Hypoteneuse) and a bit of stuff in Excel tells me I should aim for a bend to bring the balljoint in 8mm.
Best of all since my camber eccentrics have ~12mm of adjustment in them, so with only an 8mm bend I could still get back to my current 1.5 deg neg if I wanted (beyond actually to right around 0 camber)
Step 2: Get and measure some arms.
Pictures tell a thousand words, right ?
1 x shiny, straight top arm with new balljoints already pressed in - thanks Marcus !!!
Measured square at just shy of 271mm to the center of the ball joint.
Step 3: Bend some arms.
1 x 20T shop press
1 x 25mm steel plate as a work surface (I wanted something that wouldn't bend after all)
2 x Cast steel dolly's to act as supports to bend in the valley
Quality shed time = priceless.
Measure and marked to get the load from the press midway between the two support points, and some very tentative pumping of the handle later...
Step 4: A bent arm.
Measured square at just on 263mm to the center of the ball joint, which means 8mm of bend... gotta be happy with that !!!
Step 5: Rinse and repeat for the other side.
Step 6: Fit and check measurements on the car.
Before - original non-bent arms with adjusters at max neg camber (-3.5). Without a spindle adapter and properly levelling the car off it's not the most accurate method of measuring, but good enough for before and after at least.
After 1 - freshly bent arm, adjuster at minimum neg camber (-2.5)
After 2 - freshly bent arm, adjuster at max neg camber (gauge maxes out at -6 deg... but should be about -8 deg I think)
Step 7 : Crack a coldy !!!
Now just pull my finger out and bolt up the other side, then get a proper wheel alignment done !!!
😀
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I thought about shortening the top tube Nils, but renotching the springs in only 8mm per side didn't really look doable to me... looked to need to be 10mm or more to get a good notch with my springs at least.
Other benefit is this way is pretty easily reversed too - just change back to the stocko arms.
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sander288 wrote:Nice; I wonder how braking up front will be affected with the change
I'm going to go with about 4 deg neg - obviously would have to affect the braking due to the smaller contact patch, but hopefully not too severely.
Great to know you still had good braking Paul with 4.5 deg neg... nothing like having a bit of experimenting room !!!
😀
Some of the regulars at Mt Cotton run as much as 6 or 7 deg neg. Obviously the extra weight they have up front would help in the braking area, so don't think I'll be able to get anywhere near that aggressive...
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'60 KG Coupe - resto kinda started
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HappyDaze wrote:Good work there, Dave. That's the sort of stuff that this forum should be about, IMHO.
Cheers Greg.
I'm by no means a guru, but I figure should still share what I've tried, what worked and what didn't...
😉
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Craig Torrens6 times Australian, 7 times State Hillclimb Class Champion
I have run about 3' camber on my race bug for some time now, the current experiment is to give it a whole lot more caster and have less camber when the wheels are neutral. The caster also gives camber as soon as you turn the wheels. I'm using 3 sets of caster shims on the bottom tube with offroad braces on the bottom arms and shock tower extentions that fasten onto the roll cage.
sander288 wrote:Nice; I wonder how braking up front will be affected with the change
I run 5 degrees of neg camber on my Beetle with no adverse braking affect.
If you can ever get a photo of a car under heavy braking you will see the tyre distortion more than adequately makes up for the lost contact patch.
4.5-5 degrees,wow. I run 3.5 and get pretty even temps across The tyre when I do a supersprint so I have never tried more. What do you find it helps with having 5 deg col?? You run a 205 tyre?
Bit of a hijack here but has anyone done about Bumpsteer?
cnfabo wrote:4.5-5 degrees,wow. I run 3.5 and get pretty even temps across The tyre when I do a supersprint so I have never tried more. What do you find it helps with having 5 deg col?? You run a 205 tyre?
Bit of a hijack here but has anyone done about Bumpsteer?
Cheers Fabo..........
Yes we all run a 205 width tyre in the Hillclimb series.
We must account for the fact that we rarely get our tyres up to temp as they start cold and most Hillclimb tracks are only 45 odd seconds.
Tyre pressure is crucial to grip, i often change pressures at the track, up or down 1 psi can make a huge difference.
Had a Test & Tune session at Mt Cotton yesterday, and definitely happy with the change.
Running 4 deg neg for the moment - Jezzi feels much more pointy and can actually feel her sort of roll onto the tyre on turn in. Needing a bit more effort on the wheel has lead me to changing my style slightly - more short sharp movements now compared to a gradual winding on and off of lock previously.
Didn't have a pyro to check temps, but the wear pattern looks nice and even across the face so I think the 4 deg neg has to be close to right.
Best of all I chipped away at my times each run, by end of the day lowering my PB by another 0.25 seconds - so obviously shed time well spent !!!
🙂
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Yeah, someone else came up with that theory too Greg, but admit it wasn't something I'd heard of before.
My thinking is probably just me taking time to warm to the different feel and style, but whatever it is I'm happy to take the 50.53 s... now the new target for the year is a 49 !!!
😀
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Join a car club - get car peeps
My toys
'70 Hillclimb Bug 'Jezebel' w/- Haltech EFI - http://bit.ly/VwTNtQ
'60 KG Coupe - resto kinda started
01 New Beetle - gf's car, but I turn the spanners
Sides wrote:Yeah, someone else came up with that theory too Greg, but admit it wasn't something I'd heard of before.
My thinking is probably just me taking time to warm to the different feel and style, but whatever it is I'm happy to take the 50.53 s... now the new target for the year is a 49 !!!
😀
It,s nice when all that thinking and work in the shed, turns into real measurable gains.
Good one Dave.
i agree with the change of styles as ive done a fair bit of circuit stuff with the same car and ive found that the adaption of style is the biggest improver of times!
