Dummy Shock Length 25Mm Bars

[allanallen 528 2 Cars]

As title really, bit of a long shot but has anyone got any lengths/ settings for 25mm bars?

[Anthony 1,000]

For what height Allan?

 

From memory, somewhere around 280-285mm gives around 30mm lower on a 205.

 

It's been a while since I've done a beam with bars that big, but that should be in the right ballpark.

[allanallen 528 2 Cars]

A guesstimate height really, probably around -40mm. It's for a beam I'm building for a customer, I don't have the full car. The beam was lowered but it had 18mm bars so I couldn't really suss out what height it was.

 

That's helpful though cheers Anthony, I can probably take some measurements off my 309 and make am educated guess.

 

Pain in the arse building big bar'd beams

[petert 550]

290mm as a start point, depends how high or low you want it

[allanallen 528 2 Cars]

as above, about -40mm peter.

 

Where does 290 put it in your experience?

[petert 550]

About that. Certainly race trim level. It only takes 10 mins to change it if you're not happy. My dummy shock has holes in 5mm increments. Just remember to make sure you have the back higher than the front by 20-25mm otherwise roll centre will be wrong.

[allanallen 528 2 Cars]

Lol, cheers.

 

I know it doesn't take long to reset (well a bit longer due to the size of the bars) but as I've already said I haven't got the car and will be posting the beam. I wouldn't have started the thread if I had the car!

 

I've got an adjustable dummy shock using a length of threaded bar, very simple to make and you can set your ride height with much more precision than you can with a 5mm incremented one.

Edited March 25, 2015 by allanallen

[Mac Crash 78 1 Cars]

No point to create a new thread for this so I try to find one that is relevant... I've assembled the beam (first time, having read the pinned article on the front page dozens of time) and I'm using a threaded bar which is a replica of the GTi damper and has the same size of holes respectively. The beam has 23mm bars and a 25mm ARB, I've set the dummy shock to 300mm between the centres (hoping this is near to standard as advised by Anthony, if not then it's okay, everything is new and greased and I don't mind the practice part.

 

Achieving the ride height was easy enough once I figured out fine adjustment was best made from the thinner end of each bar, the torsion stud end with more splines and I checked several times, each side is 300mm, I even fitted the dummy shock to both sides just to sure. The beam sits level on the bench (no drums or disks fitted) with the bottom of each radius arm touching the bench. The problems started with fitting the ARB, eventually after rotating it several times and trying different positions on the splines I managed to get the holes for the bolts on the end plates to line up, almost, almost as close as I can achieve and having to put a little pressure on the n/s plate to allow the bolt to go in. Maybe about 1mm - 2mm off... can't seem to get it any closer.

 

n/s plate has been modified to allow access to the torsion bar, assuming this is for changing the bars without the need to remove the end plate?

 

Having fitted the ARB, the beam no longer rests fully level on the bench as it did before, the n/s radius arm is about 2mm - 3mm off the level of the surface, is this because of the tension on the ARB and is this correct? should there be load on the ARB with the beam on the bench? Not sure where I am going wrong?

Edited August 29, 2016 by Mac Crash

[jord294 87]

290 seems to ring a bell for a beam I set for forum member

[Mac Crash 78 1 Cars]

Andy, thanks... 300mm might be about right then, need the back to be close to standard and a bit higher than the front, using bilstein coilovers which are adjustable but limited to how low they can go...

 

It must be okay but surprising that movement of the rear ARB is controlled only by those 2 x 13mm bolts on the end plates.

[allanallen 528 2 Cars]

If you think about it most of the force acting on the arb end plates won't be going through the m8 bolts, it's a twisting motion so it will be transferred into the rubber bushes and the centre of the pin, it's not a lever motion acting on the bolt itself.

 

If that's as close as you can get the arb to line up there's not a lot else you can do. Yes it will alter the ride height slightly as you're putting some preload into the bar, in reality you probably won't notice.

The proper way to do it would be to set the arb with the car on it's wheels on level ground with you in it.

[welshpug 1,622]

if the ARB was machined exactly as per original specification it would be very easy to get it aligned, unfortunately most of the aftermarket ones don't seem to be, I even had an ARB without any threaded holes in it.

[jord294 87]

if the ARB was machined exactly as per original specification it would be very easy to get it aligned, unfortunately most of the aftermarket ones don't seem to be, I even had an ARB without any threaded holes in it.

Totally agree Mei

 

I've seen far too many 'uprated/hybrid' arbs, where either o/e levers are too slack over the aftermarket arb, or won't even start to go over the splines

[Mac Crash 78 1 Cars]

Thanks all... preload was the word I needed to use, Al.... I knew there would be a reason and centre of the pin makes sense... I'll spend more time with ARB and keep rotating the splines one by one and see if I can mate it dry on the bench without any load, no matter how slight on it.

 

Andy/Mei... understand what your saying... the o/s end plate slides on easy, seems a perfect interference fit, the n/s is tighter and needs pulled/pushed on the end plate, but still seems to fit correctly... the TB's are from the same people and no problems fitting them...

[welshpug 1,622]

o.e arb has a notch on the nearside end, you align this with the bolt hole, then the splines will match up and the opposing end plate will match the trailing arm if they're both accurately set.

[Mac Crash 78 1 Cars]

o.e arb has a notch on the nearside end, you align this with the bolt hole, then the splines will match up and the opposing end plate will match the trailing arm if they're both accurately set.

 

Bugger.... this ARB has a notch too... now I get it.... I'll let you know, thanks Mei

[Mac Crash 78 1 Cars]

End plates line up perfectly now with the bolt holes, no pre-load and both radius arms level on the bench, thanks again...

[joris_andriesse 8]

On 3/25/2015 at 7:01 AM, allanallen said:

I've got an adjustable dummy shock using a length of threaded bar, very simple to make 

Hi Allan,

Do you have by any chance a picture available to show how that looks like/is being made?

[allanallen 528 2 Cars]

7 hours ago, joris_andriesse said:

Hi Allan,

Do you have by any chance a picture available to show how that looks like/is being made?

Something like this….

 

[pug_ham 240 3 Cars]

12 hours ago, joris_andriesse said:

Do you have by any chance a picture available to show how that looks like/is being made?

 

This is what my dummy shock looks like.

 

Centres from some old shock bushes welded to a tube & onto an M10x1 thread so I have 0.5mm adjustment in shock length.

 

g

[joris_andriesse 8]

10 hours ago, allanallen said:

Something like this….

 

This picture doesn't work. Is it something like Graham's example?

[petert 550]

One of mine.

[wicked 103 3 Cars]

On 3/24/2015 at 10:14 PM, petert said:

Just remember to make sure you have the back higher than the front by 20-25mm otherwise roll centre will be wrong.

What do you take as reference for measuring the diff? 

I'm about to swap my 21mm for 23mm bars... 

[petert 550]

13 hours ago, wicked said:

What do you take as reference for measuring the diff? 

Just near where the sill rolls over, you'll notice there is a protective layer. I use the top edge of that. Thanks to Stu8V for use of his pic from Driver's Cars.

 

Edited March 16, 2022 by petert

[petert 550]

15 hours ago, wicked said:

I'm about to swap my 21mm for 23mm bars... 

It's a massive jump from 21mm to 23mm. Enjoy!