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 Alex Holzl
A.k.a.: Big Al
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| posted on September 21st, 2004 at 11:14 PM |
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:cry mummy!!
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gayanne
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| posted on September 22nd, 2004 at 08:12 AM |
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| Quote: | Originally
posted by Craig Torrens
| Quote: | Originally
posted by gayanne
Hey Waltermitty,thanks for those words,best way to explain bumpsteer is that two wheels are playing tuggle war against each other.One tyre wants to go
one way the other goes opposite and causes the car to come unstable at high speeds.AS the car lifts at speed the steering becomes light which pushes
the arms out causing toe out on both sides .When you slow down the car becomes stable.This is a very technical side of set up.JVLRacing
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you have absolutely NO idea...............do you? Naughty boy Craig your homework for tonight is to read a book called How to make your car to
handle.This will tell the attitude of the car not the holes in the road that make your car go bump! now, way ive explained it is whats happening with
my car.WATER IN THE HOLE you shit sterer.JVL
[Edited on 21-9-2004 by gayanne]
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VWCOOL
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| posted on September 22nd, 2004 at 09:30 AM |
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Bumpsteer, as its name suggests, is a condition where the car deviates to some extent from the driver's intended path due to bumps - suspension
movement. Similar compromised handling charateristics can also be caused by body roll on corners and when braking (many cars' suspensions tend to
'dive' at the front and lift at the back when the brakes are applied which can lead to unwanted steering behaviour)
A mis-match between suspension and steering geometry - due to careless design or inappropriate modification - is always the cause. Most cars suffer
from it to some degree, although good designs keep it to a bare miniumum.
To keep this explanation reallly simple, LP and BJ Beetles are (technically, at least) most prone to it, due to the very simple design of the front
suspension, with the suspension working in one 'plane' (along the centreline of the car) and the steering in another (across the car). When the
wheels rise and fall due to road surface irregularities, or when diving under brakes, the wheels tend to steer themselves slightly, independent of
steering input, due to the mis-match (for want of a better term) between the arcs of movement of the tierods and the arcs of the trailing arms.
In stock ride-height Beetles, the gemonetry is set-up so wheels tend to toe-in under brakes, which assists stability. Beetles that are lowered with no
extra attention to steering/suspension geometry, tend to toe-out making them liable to 'dart around' under brakes. It's all made worse by the fact
Beetles have a short- (drivers side) and long (passenger side) tie rod design. The two different lengths mean there are two different radius arcs
described when the suspension moves, meaning the the wheels tend to toe in (or out) at different rates. All good fun!
To my knowledge, the very best suspension set up for eliminating bump steer is an upper and lower A-arm set up with rack and pinion steering and
anti-dive characteristics built in. Far better than struts, or the old Beetle geometry - but it costs more to manufacture from an OE point of view.
Having said that, careful modification within the architecture of a standard Beetle front end can reduce bumpsteer and roll-steer, and increase
high-speed stability, giving very good handing both on-road an on-track.
Technically, none of this stuff is very hard - especially for a car intended for circuit work with limited suspension travel. Nissan (Fairlady) and
Lotus (Elan), to name two, got this stuff right decades ago. High speed stability can be improved by increasing caster, but that's another subject
matter altogether... Get the rack placement wrong, or the tie-rod/suspension arm relationship wrong, and you might as well be playing Meccanno with
bits of tube...
[Edited on 21-9-2004 by VWCOOL]
[Edited on 22-9-2004 by VWCOOL]
Pay your debts, CxxT
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gayanne
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| posted on September 22nd, 2004 at 10:07 AM |
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Good effort writing VWCooL,its spot on but each car reacts differently.The way ive explained it is what is happening with my car.Your last paragraph
mention about the steering which was my problem.What ive done is changed height of the steering tie rods.JVLRacing
[Edited on 22-9-2004 by gayanne]
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Secoh
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| posted on September 22nd, 2004 at 10:25 AM |
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gayanne I think you need to look at the toe in (both at static and at slight raised such as what happens under acceleration and high speed) castor
angles, and possible aerodynamic lifting of the car. If you arent running an air dam at the front then chances are the front is lifting at speed,
causing it to feel unstable.
If it aint broke,
Make it go faster!!  |
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VWCOOL
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| posted on September 22nd, 2004 at 11:21 AM |
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I agree - the handling problems you are having, JVL, probably aren't related to bump steer. Not may bumps on a track... It's aerodynamics. You need
to hunker the front down at speed - not have it lift! Maybe you have the centre of aerodynamic pressure in front of the centre of mass of the car,
which will make it tend to dart sideways immediately it gets 'not square on' with its direction of travel due to minor surface irregularities etc.
It's possible to get a BJ Beetle to track straight qnd be stable on-road, at upwards of 180km/h with mildly-modified factory geometry...
Pay your debts, CxxT
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BiX
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| posted on September 22nd, 2004 at 11:39 AM |
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you must fix the problem not the result of it. find out if its aero or geo thats causing the bump steer. no ppoint in trying to fix the bump steer if
its the car floating casuing the problem.
I have no sympathy for my car, only the wallet that pays for it!
Go hard or go home!!!!
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HotRodMatt
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| posted on September 22nd, 2004 at 11:46 AM |
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| Quote: |
EasternCreekdrag strip 13.4 with a problem called bumpsteer which caused me to back of at the 600ft mark
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A half track powered run giving at 1/4mile ET of 13.4????
Judging by other cars that come off the power at half track and have similar full track ETs that would have put the 1/8th at about 6.25 seconds?
One would be imagining a 9 or very low 10 second car...
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Che Castro
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| posted on September 22nd, 2004 at 01:50 PM |
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i thought craig was being sarcastic 
Anyway we should all chill out a bit 
Jon
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VWCOOL
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| posted on September 22nd, 2004 at 02:07 PM |
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handling
No, I think Craig was being serious. It seems that gayenne:
a) has a problem with his car's handling and
b) Has a problem with the understanding of the problem, IYKWIM
I attempted to clarify what bump steer means - and that itshould have very little to do with straight-line stability - and also to point JVL in
another direction, that of his car's aerodynamics, to possibly help him diagnose his car's evil handling.
After all, if many of us can get a $500 Beetle to handle on-road and on-track with a few well-spent dollars and tricks, surely gayenne can expect
similar from a purpose-built track car?
Pay your debts, CxxT
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gayanne
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| posted on September 22nd, 2004 at 02:58 PM |
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| Quote: | Originally
posted by HotRodMatt
| Quote: |
EasternCreekdrag strip 13.4 with a problem called bumpsteer which caused me to back of at the 600ft mark
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A half track powered run giving at 1/4mile ET of 13.4????
Judging by other cars that come off the power at half track and have similar full track ETs that would have put the 1/8th at about 6.25 seconds?
One would be imagining a 9 or very low 10 second car...
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Hi Hot rod that what happen at 660ft not 600ft my mistake, the car done 8.4 at 660 with backing of.JVLRacing
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gayanne
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| posted on September 22nd, 2004 at 03:46 PM |
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Hey thanks for the help VWCool iam sure i will take this on board.The car does have an undertray ,runs 0 toe,+5 caster.There are no real accurate way
to get bumpsteer right without a bumpsteer gauge soon to by one.Ive been using test program from abook toget accurate as possible.The aero ive spent
big money on with smoke testing (a long story) i will check it again.At this moment i need to get the car to be reliable and that takes bum in seat
time and more dollars. But i will check everything .JVLRacing
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VWCOOL
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| posted on September 22nd, 2004 at 07:22 PM |
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A bumpsteer gauge will tell you that you have bumpsteer - but you already know that (if, in fact, you have bumpsteer) but I don't think it will tell
you how to fix it. You can see bumpsteer by hoisting the car... the wheels will toe out/in as the car is raised and the suspension droops. Fixing
bumpsteer requires a good look/analysis at the geometry of the front end - the relationship between control arms/tierod pivots and their lengths etc
etc etc
Pay your debts, CxxT
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gayanne
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| posted on September 22nd, 2004 at 09:44 PM |
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| Quote: | Originally
posted by VWCOOL
A bumpsteer gauge will tell you that you have bumpsteer - but you already know that (if, in fact, you have bumpsteer) but I don't think it will tell
you how to fix it. You can see bumpsteer by hoisting the car... the wheels will toe out/in as the car is raised and the suspension droops. Fixing
bumpsteer requires a good look/analysis at the geometry of the front end - the relationship between control arms/tierod pivots and their lengths etc
etc etc
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[Done all of that where car was toeing out when jacking and adjusted control arms and shim tierod arms lot better then
before.JVLRacing
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Secoh
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| posted on September 23rd, 2004 at 08:36 AM |
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surprised you run 0 toe, even on a road car (RWD) you run a touch of toe-in to compensate for slack in materials, which brings it back to 0 when in
motion.
If it aint broke,
Make it go faster!! |
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restocal
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| posted on September 23rd, 2004 at 09:57 AM |
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JVL, the car is a credit to you. It's amazing you've designed the suspension from scratch. I'm sure it will take some time to get the bugs out.
All the hillclimb guys do is bind up there standard suspension so the thing handles like a go cart. That Torrens blokes car handled like crap at Oran
Park.
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VWCOOL
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| posted on September 23rd, 2004 at 10:06 AM |
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So does my HSV... I think you'll find that Craig's car is set-up for winning hill climbs - something it does very well! - not high-speed track work!
Pay your debts, CxxT
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gayanne
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| posted on September 23rd, 2004 at 06:34 PM |
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Yep always learning,refuse to be a arm chair expert thanks for the support.JVLRacing
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Cam
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| posted on September 25th, 2004 at 04:22 PM |
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Alex, why the hell did you guys go drifting at a Porsche track day? Hope you didn't get in the way of anyone going for club points :P
Just remember you can drift anything  http://drift411.com/forums/index.php?act=Attach&type=post&id=119
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Alex Holzl
A.k.a.: Big Al
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| posted on September 25th, 2004 at 11:29 PM |
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hahha im in the lead in that one!!!
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Quoll
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| posted on September 26th, 2004 at 10:40 AM |
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So do all you guys have IRS with some sort of LSD?
Or is some one still running with an open box and swing axel (Like me )
I'd be interested in a comparision in times between swingaxel and IRS |
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Oasis
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| posted on September 26th, 2004 at 10:54 AM |
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Thay are all IRS. Dieter has a slippery diff, and was running slicks. I gon't know about the rest.:thumb
"Tell him 'We've already got one'"
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Alex Holzl
A.k.a.: Big Al
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| posted on September 26th, 2004 at 05:55 PM |
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we are all irs and with LSD. Swing axle is not the best for a quick track car.
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waltermitty
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| posted on September 26th, 2004 at 08:36 PM |
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Alex you should know that wih my background I am unbeatable in a golf cart.
Mitty
23 windows ...8 too many!
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Alex Holzl
A.k.a.: Big Al
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| posted on September 26th, 2004 at 08:38 PM |
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ahhahhaa yeh yeh we'll see about that!!!
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Oasis
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| posted on September 26th, 2004 at 08:53 PM |
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I'm good in a shopping trolley:tree
"Tell him 'We've already got one'"
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Craig Torrens
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| posted on September 26th, 2004 at 09:09 PM |
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| Quote: | Originally
posted by restocal
JVL, the car is a credit to you. It's amazing you've designed the suspension from scratch. I'm sure it will take some time to get the bugs out.
All the hillclimb guys do is bind up there standard suspension so the thing handles like a go cart. That Torrens blokes car handled like crap at Oran
Park.
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HEHEHEHEHEHE....handled like crap and still did 54's with a standard gearbox and no LSD...................if you bind up your suspension you
certainly won't WIN hillclimbs,,,,,,,,,,show's you have NO IDEA as well !
Give up Retro.
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Alex Holzl
A.k.a.: Big Al
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| posted on September 26th, 2004 at 09:15 PM |
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lol
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restocal
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| posted on September 27th, 2004 at 09:58 AM |
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LSD
Jnr Holzl,
You're a bit young for LSD but what are you using, Quaiffe or ZF?
You should be under 2 minutes with all that horsepower?
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Alex Holzl
A.k.a.: Big Al
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2332cc of pure BALLZ!!
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| posted on September 28th, 2004 at 10:56 AM |
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im using a ZF, how old do u hav to be? im happy with my time seeing as im only on street tires and i still hav abit of under steer only my second time
on any race track and was my first at eastern soo im sure lap times will improve as i sort the setup of my car.
Alex
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