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Cal-look/High Performance => Pure racing => Topic started by: Jøran Larssen on June 20, 2007, 11:59:20 am



Title: Advise regarding rear suspension before EBI
Post by: Jøran Larssen on June 20, 2007, 11:59:20 am
My car looks like it is to soft at the rear when launching. I have got original torsion bars and adjustable (60/40, 50/50, 40/60) Carrera shocks.

I am considering replacing the torsion bars with a set of Sway a Way 24 11/16" Lng 26 mm dia that I have got, and a set of red Konis.

Take a look at the two pictures below. Will it make sense to replace the torsion bars, or is it a set of harder shocks that will do the trick?

Or can it be a combination with the ofset of the Ercos?     

(http://www.rallybilden.se/BugrunMantorp070610/bugrunmantorp_070610_158.jpg)

(http://www.rallybilden.se/BugrunMantorp070610/bugrunmantorp_070610_159.jpg) 


Title: Re: Advise regarding rear suspension before EBI
Post by: richie on June 20, 2007, 21:56:00 pm
Definately looks to soft there.The torsion controls the down movement,the shock controls the up,the 26mm bars and red konis would be a good combo,see you next week,cheers richie,uk


Title: Re: Advise regarding rear suspension before EBI
Post by: Jøran Larssen on June 20, 2007, 22:39:11 pm
Thanks Richie. I guess I will have to spend the weekend in the garage then. See you at EBI.

Cheers
Jøran


Title: Re: Advise regarding rear suspension before EBI
Post by: Rasser on June 21, 2007, 00:27:08 am
funny you should post this...

At Bugrun last weekend we talked about your car looked "uneven" running down the track. Looked like the one side was lowered more than the other. Don´t know if you ever noticed that yourself - but it did look a tiny bit scary ;-)

anyway, if you´re changing to new 26mm torsion bars this problem should dissappear as well.


Title: Re: Advise regarding rear suspension before EBI
Post by: Jøran Larssen on June 21, 2007, 07:21:45 am
I noticed that myself when I looked at some videoclips. It is actually softer and lower on the right rear side  :-\


Title: Re: Advise regarding rear suspension before EBI
Post by: richie on June 21, 2007, 09:17:44 am
I noticed that myself when I looked at some videoclips. It is actually softer and lower on the right rear side  :-\

Drivers weight :o    cheers richie,uk


Title: Re: Advise regarding rear suspension before EBI
Post by: Roman on June 21, 2007, 09:53:07 am
Definately looks to soft there.The torsion controls the down movement,the shock controls the up,the 26mm bars and red konis would be a good combo,see you next week,cheers richie,uk

No, the torsion bars adjust how much you squat and the shocks adjust how fast it will get there. 
Make a simple test:
1: Stand on the rear apron and measure the ride height.
2: Remove the rear shocks and measure again.
You will get the same ride heigt in both examples.

Test #2:
1: Jump up FAST on the rear apron.
2: Remove the rear shocks and do the same as above

Can you see how it goes even under the level of 1: without shocks but goes back to the same level as 1:
This is called Underdamped Oscillator.
Here is a link for those who would like to study more:
http://hyperphysics.phy-astr.gsu.edu/hbase/oscda.html


Yes, I am a math nerd, I have studied math, physics and contol tech at the univeristy...


Title: Re: Advise regarding rear suspension before EBI
Post by: richie on June 21, 2007, 21:18:58 pm
Definately looks to soft there.The torsion controls the down movement,the shock controls the up,the 26mm bars and red konis would be a good combo,see you next week,cheers richie,uk

No, the torsion bars adjust how much you squat and the shocks adjust how fast it will get there. 
Make a simple test:
1: Stand on the rear apron and measure the ride height.
2: Remove the rear shocks and measure again.
You will get the same ride heigt in both examples.

Test #2:
1: Jump up FAST on the rear apron.

Just damaged my rear apron,you going to pay for fixing it? :-)



2: Remove the rear shocks and do the same as above

Can you see how it goes even under the level of 1: without shocks but goes back to the same level as 1:
This is called Underdamped Oscillator.
Here is a link for those who would like to study more:
http://hyperphysics.phy-astr.gsu.edu/hbase/oscda.html


Yes, I am a math nerd, I have studied math, physics and contol tech at the univeristy...


Dont agree,you changed the force by jumping on the apron, but bow to your superior knowledge :P

cheers richie,uk


Title: Re: Advise regarding rear suspension before EBI
Post by: Jøran Larssen on June 21, 2007, 22:18:44 pm
I noticed that myself when I looked at some videoclips. It is actually softer and lower on the right rear side  :-\

Drivers weight :o    cheers richie,uk

Only water for me the next week then  ::)


Title: Re: Advise regarding rear suspension before EBI
Post by: Russell on June 21, 2007, 22:46:04 pm
Me too water will help.

However have tried the jumping on the rear apron but cant help but think this is false situation, when you launch off the line the rear wheels are drving forward therfore trying to push the torsin bars down, but at the same time the front of the car is lifting giving an opposite reaction....... If you only push down on the rear valance you will only have one effect !

Im not a maths person but from a practical point of view we have 2 forces on launch and only 1 when jumping....

Could it also be that the rear tracking is out slightly ? or could it just be the way the gearbox is made i.e one sided ?

If all this sound rubbish, please just hummor me !


Title: Re: Advise regarding rear suspension before EBI
Post by: richie on June 22, 2007, 09:24:24 am
I noticed that myself when I looked at some videoclips. It is actually softer and lower on the right rear side  :-\

Drivers weight :o    cheers richie,uk

Only water for me the next week then  ::)

Water  = Tea   :)  cheers richie,uk


Title: Re: Advise regarding rear suspension before EBI
Post by: lowfastbus on June 22, 2007, 13:09:15 pm
Not wanting to hi-jack this thread, but on the subject of rear suspension...

Do you pre tension your car with limiter straps? or do you mount them without tension...
How long do they usually have to be?

I'm lowering my car a few cm's for EBI because it has a dangerous positive camber, especially when I lift the pedal.  This should get fixed with the straps...hopefully ::)


Title: Re: Advise regarding rear suspension before EBI
Post by: ALIEN on June 22, 2007, 16:18:34 pm
On my Alien bug i got coilower shoks.. they give the car positive camber.. so i got wire sraps, to hold the car in right posision..

I think it woorks..

or im i wrong?

Alien


Title: Re: Advise regarding rear suspension before EBI
Post by: Jøran Larssen on June 22, 2007, 22:40:19 pm
I ended up with some positive camber after adjusting my car today. It's not exactly what I wanted, but it will stay like this for EBI. As a safety precaurtion, I added a set of limiter straps. Anyway, it is much stiffer at the rear now  :P 


Title: Re: Advise regarding rear suspension before EBI
Post by: Gunter on June 23, 2007, 23:03:02 pm
friends it all makes sence
the only thing I can't figure out now is that I have the distinct idea Chimay is very small for two racers next to each other
what do you think ?

Gunter


Title: Re: Advise regarding rear suspension before EBI
Post by: richie on June 24, 2007, 20:40:18 pm
friends it all makes sence
the only thing I can't figure out now is that I have the distinct idea Chimay is very small for two racers next to each other
what do you think ?

Gunter
It does look narrower than i am used to but we just have to stay in our own lane :o and it will be fine :D  cheers nrichie,uk


Title: Re: Advise regarding rear suspension before EBI
Post by: Roman on June 25, 2007, 08:51:35 am
I have limiter straps. I used to have McKenzies, but I recently changed them to steel wires and wire locks so I can adjust the length.
On a bug 22" usually fits good and they should be so short that you have to put them on AFTER the engine is installed and it is back on the ground. When I lift the rear end with the straps on the axles are almost straight.

If you have stiffer bars there is no need for preload. A 28 mm bar should slip just over the stop when you install them if you have a type 1 trans. If you have a bus tranny you should have about 6 mm of air between the stop and the bar.


Title: Re: Advise regarding rear suspension before EBI
Post by: oldbug on June 25, 2007, 10:15:07 am
hi guys,
due to the building of a car, could you please give me informations ?
Where to find QA1, red koni shocks, limited straps (summit or other) ?
Models, names and references of this parts ?
regards
Laurent


Title: Re: Advise regarding rear suspension before EBI
Post by: Roman on June 25, 2007, 10:35:25 am
Look at my recently placed for sale ad, everything you need is there!  8)


Title: Re: Advise regarding rear suspension before EBI
Post by: oldbug on June 25, 2007, 11:27:15 am
thanks, look at my question on your ad. ;)


Title: Re: Advise regarding rear suspension before EBI
Post by: lowfastbus on June 27, 2007, 07:17:42 am
Roman,

I have 8mm and 10mm steel wire and wire locks, would this be any good??

thanks
Jelle