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 HS618
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| posted on May 3rd, 2010 at 07:13 PM |
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Rear Suspension Tuning
A photographer approached me at the Nitro Championships at Sydney Dragway last week (I was running the beetle) and offered me a photo of my beetle on
the dragstrip from a previous meeting. As I have way too many, I initially refused. He said it was an interesting one, so after viewing it, I bought
it.
The real question is: Would you accept rear suspension (or clutch) tuning advice from the guy who set this up?
Ross, this is what your car would act like with no rear suspension and your current clutch!!
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HS618
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| posted on May 3rd, 2010 at 07:20 PM |
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I need help , but in this case it's the picture!!!. I'm to insert - the picture currently is 541 kb and I need to compress it (it's a JPEG)
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HS618
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| posted on May 3rd, 2010 at 07:55 PM |
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If I keep trying, it will eventually work
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 vw54
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| posted on May 3rd, 2010 at 08:28 PM |
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Great pic Henry How come the rear is off the ground ?????
at least its straight
So do u remember which run it was how was yr speed and ET ????
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1303Steve
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| posted on May 3rd, 2010 at 08:30 PM |
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Hi Henry
As they say a picture is worth a thousand words, I think the flux capacitor is turned up too high and its about to take off.
So it looks like the drivers side wheel is getting a bit of negative, seems to be still launching straight.
Steve
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SuperOwen
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| posted on May 3rd, 2010 at 08:42 PM |
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More pies and chips to balance it out?
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71-BEETLE-SEDAN
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| posted on May 3rd, 2010 at 08:44 PM |
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AH mine does that, na not really im joking but you could win some bets with some ricers to be first one to get a rear tyre off the ground, make some
cash on the side
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HS618
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| posted on May 3rd, 2010 at 08:46 PM |
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From what I have seen on the forum over the years, there are lots of people that could tell me what the problem was and how to fix it.
Knowing the car and how it sits, both wheels were unloaded in the picture with the right side obviously quite unloaded.
The problem has since been fixed (permanently) as it ran a 12.27 @107? mph in time trials at the Nitro's. (Those close know that I don't want it
running that quick and that will take longer to rectify.)
As to what run it was Dave, I don't know, but it was time trials at Bracket Attack #5 during qualifying with good traction. None of the runs (in the
60') were out of the ordinary on the day- H
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Dak-A-Tak
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| posted on May 3rd, 2010 at 09:14 PM |
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Henry , Sorry I missed your call . Thats a better et , right in the middle of S/ST mate . Quick ET's feel good !
Maybe ? , Torsion bars to big , not enough power to hold the suspension down under power ,or The shocks had bottom out , make a shock setting change .
You have made a few passes now Henry on new car , how many ?
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HS618
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| posted on May 3rd, 2010 at 09:43 PM |
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Great guesses Pete, unfortunately, no Christmas Tree although there is 1 there that deserves an honourable mention(not enough power).
I'm away at the moment, so the numbers aren't official, but Im up to about 38 (including 1/8 mile tracks) and still learning and kicking myself in
the butt when I make stupid mistakes
In regard to being in the middle of Super Street, I would rather have more space between me and the quick cars before they leave the line as it costs
a lot of money and consistency to run beside them!!!!.
On a smile side, I set the invisible wheelie bars higher!
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SuperOwen
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| posted on May 3rd, 2010 at 09:51 PM |
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Do you run straps or something to limit suspension droop on the rear? Its a neat pic anyway!
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HS618
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| posted on May 3rd, 2010 at 10:08 PM |
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Rear end consists of stock '68 semi auto pan (converted to manual), short 26mm torsion bars, double spring plates (thanks Dave), alloy spring plate
covers, heavy gas shocks (stock length) with spherical ball ends, no limiting straps, standard Kombi bump stops with the first bump cut off (at that
meeting), no bars across the shock towers and down to the forks - fairly normal, actually.
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 matberry
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| posted on May 3rd, 2010 at 10:18 PM |
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Hi Henry, thanks for sharing.
With your ride height and bars etc, I'd say to run the Kombi bump stop without cutting, even some hose clamps to stiffen them up (and give tuning),
and or bigger bars. Looks like the squat is rebounding the tyre off the track....can't be good for axles and tranny......must be strong with 38
passes on em  .
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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HS618
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| posted on May 3rd, 2010 at 10:28 PM |
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Matt, knowing what fixed the problem MORE bump stop clearance would have helped. Tightening up the rear end would have added to the spring rate which
would have probably produced more lift. I use stock axles with standard kombi CV's. On the drive back from the finish line, the gearbox still sounds
good although at 50 runs, the whole set up (engine / gearbox) will recieve a major crack testing exercise
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matberry
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| posted on May 3rd, 2010 at 10:31 PM |
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Cheers Henry, no wonder I have so much trouble with a quick 60'.
Matt Berry Motorsports...air cooled advice, repairs and mods Ph 0408 704 662
OFF-ROAD,CIRCUIT,DRAG,STREET,ENDURANCE
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Thinker
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| posted on May 3rd, 2010 at 10:39 PM |
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just a thought but i would imagine you have balanced suspension and may need to unbalances to allow for the engine torque it will be trying to lift
drivers side of the car.
maybe!!!
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HS618
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| posted on May 3rd, 2010 at 10:46 PM |
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Matt, everybody does it different, that doesen't mean that some setups are right and some are wrong. Every set-up is different, respond to similar
changes differently and as Dave B says, the fun is in the tinkering. The worse thing with the photo is that I couldn't feel the unhappy reaction of
the car from inside.
I'm more than happy with my 60's now as they are staying reasonably consistent regardless of track conditions
At the moment, everyone is clutching at straws, but I'm learning from this post - Thanks
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HS618
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| posted on May 3rd, 2010 at 10:52 PM |
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As for balanced suspension, having had more burgers in my lifetime than the fat controller, I had to bias about 1/2 degree in the spring plate on the
driver's side to compensate for my weight. As the vehicle doesn't use a spool, I am not too concerned with accurate or biased rear corner weights
and I know that was not the issue - Thanks
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westi
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| posted on May 4th, 2010 at 12:30 AM |
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side wall of the tyre.spring back as the tyre grew.just a guess.
down sharon.
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SuperOwen
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| posted on May 4th, 2010 at 08:16 AM |
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Too much bump stop adding to the spring rate and bouncing the car? Is there a jar of jelly beans for the right guess?
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dangerous
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| posted on May 4th, 2010 at 08:49 AM |
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I have not seen your car run on a good track,
but THAT, combined with the tall gearing and low power,
would make it very difficult to keep the rear suspension under compression through the whole of first gear,
unless you can control it with the clutch.
There is no doubt from the picture that the car is in maximum rebound at that point.
The issue is not whether the cause of the rebound is the shock, tyre or spring rate,
but why it unloaded(rebounded) in the middle of first gear in the first place.
Too much clutch is where I would start.
....but my guess is you have already sorted that out by using a fresh clutch.
(sintered iron clutch discs can actually increase their torque capacity after use, thus inducing bog,(ie too much clutch).
| Quote: | Originally
posted by westi
That's mad Alan.
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OLD-DOG
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| posted on May 4th, 2010 at 01:19 PM |
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Henry...you can take this to the bank...you know that you need something to cushion the torque reaction.Compressing bump stops etc only compunds the
lift problem.If there are limiting devices preventing progressive shock load absorbtion you induce lift.
I need the type of clutch that I use to hold onto the torque.I have no bump stops,no limiting devices & YOUR 28 mil bars & mine leaves flat
except for maybe 50mil of front wheel clearance sometimes.I have the engine out & the clutch.By the amount of colour & clutch dust that 3 puk
& 3,000lb plate is just adequate.Whilst cars are climbing their forard motion is being impaired..That engine of yours must be reasonably strong or
have you lost weight or is it Butler driving it ???Ross
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Menangler
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| posted on May 4th, 2010 at 05:31 PM |
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Hey Henry,
It's photo shopped, the photographer did it so you would buy the photo 
Dave
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HS618
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| posted on May 4th, 2010 at 05:50 PM |
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Ross, the answer to your last question is: ..........none of the above!
Dave, if he photoshopped it, he only did half a job!!
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rose
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| posted on May 4th, 2010 at 06:41 PM |
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That's a great pic
[img][/img]
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OLD-DOG
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| posted on May 5th, 2010 at 10:25 AM |
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HENRY..Menagler is on the money he wins the jelly beans !! There is no way due to the weight transfer to the rear when wheelstanding to have daylight
under that rear RH tyre...unless you have tyre shake giving tyre distortion & that isn't going to happen in your case....
I would blame commercial extortion & my sympathy towards the anguish that has been caused..Ross
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HS618
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| posted on May 5th, 2010 at 09:10 PM |
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Dave B.was on the money, the clutch was too violent for the low power and good traction I have, causing rapid compression of the rear suspension. The
compression could not be maintained and due to the shocks being heavy on compression and light on rebound, allowed rapid spring rebound forcing the
rear to rise and the momentum of this action raised the rear
Lowering the clutch clamp torque allowed the clutch to slip at a somewhat constant amount, (in relation to my engine torque) then gradually clamp. As
the track at Sydney Dragway is well prepared, I can't spin my 26"x 6" inch slicks, so to keep the engine RPM's at usable torque, I need to
"spin" the clutch
At the Nitro's, the car was a (slow motion) dream to drive - and the 60' reflected that. As the meeting progressed and the traction increased (with
all the rubber laid down by the Group 1 vehicles) the 60's were still reasonably consistant.
Now , all I need to do now is find out after how many runs does the clutch need to be serviced.
Thanks for all your inputs and I hope we all learned something along the way. - H
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Dak-A-Tak
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| posted on May 5th, 2010 at 09:56 PM |
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Thats what I said !Rapid spring raise .
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mactaylor
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| posted on May 6th, 2010 at 04:07 AM |
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woulld one of those black magic discs be of any use?
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dangerous
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| posted on May 6th, 2010 at 05:17 AM |
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| Quote: | Originally
posted by mactaylor
woulld one of those black magic discs be of any use?
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Hi Mac,
Henry is already using a black magic disc.
The actually increase their torque capacity after some use,
which was the problem making the car bog.
| Quote: | Originally
posted by westi
That's mad Alan.
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