Adjustable lower trailing arms discussion.

[Crazy2287 1,886]

It's that time again,

 

Lower trailing arms, I'm about to make me some. But i'm throwing this out there before i put money down incase it's a dumb idea. =P

 

So the bees knees rose joints will cost about 72-85 bucks each for the 5/8ths - 3/4 size respectively(im thinking 5/8ths would be strong enough?).

Was going to use 1 of them on one end of some 26mm OD with 3.2mm wall tube, This will allow about 1" of adjustment at 0.71mm increments (is that enough?).

On the other end i would mount a receiver to take the standard size bush. I was leaning towards a rubber bush but i have a spare set of nolathane here i'll probably run first.

With this, i should be able to make both lower arms for about $200 inc $50 for the bushes.

 

So you don't have to picture it in your mind i found one similar to my thoughts on the google machine, just imagine it has a receiver for a polyurethane bush at the bare end:

 

 

The other options is to keep the current style bush, in either nolathane or rubber, fabbed onto the same 26mm OD 3.2mm wall tube at each end. with a turnbuckle type thing machined up out of a piece of rod and stuck in the guts like this one here:

 

Opinions, ready, set, GO.

[mcfly94 169]

Sounds good!, help with them lowered cars, will they be polished , and what about upper arms

[Tyler06 266]

Not for a falcon but funny enough ive been researching the second setup for the corty. But i wanna do it to the top arms, obviously a different setup but i think the top arms will accomplish more and fix the cortys angle probs.

[Tyler06 266]

Sounds good!, help with them lowered cars, will they be polished , and what about upper arms

 

If you were to do both top and bottom then you could run the risk of adjusting the diff one way to far eg. Backwards or forwards but if you do one set your really only changing the pinion angle. Both could be done and lots have done it but you have a bigger margin for error. Thats just my opinion and view but..

[mcfly94 169]

If you were to do both top and bottom then you could run the risk of adjusting the diff one way to far eg. Backwards or forwards but if you do one set your really only changing the pinion angle. Both could be done and lots have done it but you have a bigger margin for error. Thats just my opinion and view but..

I meant top over bottom, whats better anyway?

[Crazy2287 1,886]

Lower arms are straight, Easier to access. So just a little easier to make and use.

The reason i'm doing it, My lower arms are ratshit from when i use to take the car 4x4ing when i was a teenager. Sliding it over rocks. And the nolathane bushes have had the dick. So it's due replacement.

The reason im fabbins adjustables is the car sits quite low. If i ever do get around to taking the car regularly(ish) to the track i want to make sure that pinion angel is right to avoid leaving a tailshaft on the track.

I'm not sure on the grip changing abilities at this time.

 

Happy to talk about all factors, especially the proposed design type and materials.

If i'm under-engineering or making a bad decision it's best to find out now, considering the nature and criticality of the part.

[mcfly94 169]

Lower arms are straight, Easier to access. So just a little easier to make and use.

The reason i'm doing it, My lower arms are ratshit from when i use to take the car 4x4ing when i was a teenager. Sliding it over rocks. And the nolathane bushes have had the dick. So it's due replacement.

The reason im fabbins adjustables is the car sits quite low. If i ever do get around to taking the car regularly(ish) to the track i want to make sure that pinion angel is right to avoid leaving a tailshaft on the track.

I'm not sure on the grip changing abilities at this time.

 

Happy to talk about all factors, especially the proposed design type and materials.

If i'm under-engineering or making a bad decision it's best to find out now, considering the nature and criticality of the part.

Yeah that makes sense.

I reckon the finish should be polished.

My be up for this too!

[Crazy2287 1,886]

LOL you cracker Fly, I'm not making them for everyone. Making them for myself because i'm a selfish bastard.

 

But don't worry, you can anticipate a how to thread with material list at the end of the evolution. with a good machine shop they will be piss easy to make yourself.

[mcfly94 169]

LOL you cracker Fly, I'm not making them for everyone. Making them for myself because i'm a selfish bastard.

 

But don't worry, you can anticipate a how to thread with material list at the end of the evolution.

oh gay!

 

sick mate!, (sick subwoofer), but I thought you liked making things for people

[Tyler06 266]

LOL you cracker Fly, I'm not making them for everyone. Making them for myself because i'm a selfish bastard.

 

But don't worry, you can anticipate a how to thread with material list at the end of the evolution.

Selfish bastard!!! We have become a custom to wen crazy designs we all win lol

[mcfly94 169]

Selfish bastard!!! We have become a custom to wen crazy designs we all win lol

Your not wrong there, love my spacers!

[Crazy2287 1,886]

Yeah but you forget. It took me 18 months to get the first shock spacer out my door.

That said, It's really hard to get the spacers. and when you can tehy are way too exxy. IMO $170 is too exxy but the cost of having them in alloy doubles the manufacture $$$.(im a fishass)

But You can buy the trailing arms off the net. They usually cost 300+ though.

 

PS.. not polished. They r gonna be fkn BLLLAACKKKKKKK

[mcfly94 169]

Just had look on mc Donald bros racing website and its $385 for xe/au lower tubular adjustable trailing arms and $365 for upper. It would be worth it if you can cut those costs down

[Tyler06 266]

Just had look on mc Donald bros racing website and its $385 for xe/au lower tubular adjustable trailing arms and $365 for upper. It would be worth it if you can cut those costs down

 

Did someone mention a fishes asshole lol

[Thom 6,654]

Hey q, personally I would go fixed,lower control arm (boxed would be better than standard) with an adjustable top arm ( I realise harder to make) the top arm would greater effect pinion angle and your roll centre due to the higher load they take over the lower arm, btw what diff cover are you running? Some au's have the Watts link mount 10mm lower down which also lowers you centre of gravity/ roll centre an make a cast improvement in the twistys & drive out of a corner/ launch

[Thom 6,654]

When you set your rear suspension up you want the pinion to start to point down as the diff travels towards the body, this counteracts the natural tendency of the pinion to try and "climb" the crownwheel and plants the rear tires to the pavement (hopes this makes sense as I'm very drunk right now)

[Campo 869]

Any idea which diff hats are different Thom?

 

Also, Crazy, some diffs (EF-EL possibly from memory? Its e series for sure) have numerous holes to put the standard bottom arms in, which alters pinion angle also.

[Thom 6,654]

From what I can gather seems to be mostly series 2& 3 au's with a live axle have the spindle for the Watts link lower down

[Campo 869]

Is there any easy way to tell the difference?

[Thom 6,654]

Not really you just have to measure them

[Crazy2287 1,886]

I've been interested in finding one of those rear housings for a while. But couldn't remember what model diff they were on.

 

I don't understand how which arm is adjustable, will alter the handling effect. I haven't measured but they both look like they are the same distance from the lateral centerline of the diff. Have you got a link or can you explain with a bit more depth?

[Wes 214]

If you think you can make them and make them well for $200.00 being the tinkerer you are, I know you'd love making them and I say go for it. But I think your costs will shoot up past that.

 

May as well go to page 3 of this catalogue and be done with it http://www.mcdonaldbrosracing.com.au/pdf/pricesus.pdf

[Tyler06 266]

If you think you can make them and make them well for $200.00 being the tinkerer you are, I know you'd love making them and I say go for it. But I think your costs will shoot up past that.

 

May as well go to page 3 of this catalogue and be done with it http://www.mcdonaldbrosracing.com.au/pdf/pricesus.pdf

Thanks for that i didnt know they did the cortina ones ;-) i wont bother making any i will just buy their adj ones for top and bottom haha

[ILIED 316]

Here's an idea.
Go to a joint that does fabrication work for powerstations or other plant with boilers.
Get yourself some ChromeMoly tube. Comes thick as fuck wall thickness. I'm using some to make some lowercontrol arms for my F100 (still leaf spring).

Places with boilers use crmo cos it has better temperature stability, btw.

 

 

Once you've got this, consider not using a turnbuckle.

I understand that yes, with a turnbuckle you can make the adjustments on ramps, but if you just use a righthand thread, you can lift her up on stands, unbolt from the diff, make the changes and then bolt it back up. It'll be cheaper than buying a left-hand tap and a right hand tap, and you wont need to purchase two turnbuckles.
I'd use a fine thread, so you can make smaller adjustments. (180degree turn is half the threadpitch, so like 1-2mm).

 

It might be shit for the first bit, having to keep putting the car on stands, but I dont think you'll be changing it too much after that.

[Crazy2287 1,886]

Fuck yeah Wes, Good link that one! Cheers. I did see em on there but i never saw a price listing, that's not that bad for an aussie shop! I'll price parts up probably next week. Depending on what i can get and how much machine work is needed will dictate the cost a lot.

 

I'll only use mild steel thick wall tube as the moly tube suffers embrittlement when you weld it and requires retempering. I don't have the gear or the experience to temper something that size and criticality.

 

Agree on the turnbuckle. If you' on flat ground i would be able to change the lower arm without jacks. Only unbolt 1 arm at a time and twist the end and you could adjust with the weight on wheels.

I'm still torn if i should use rose joints, or go bushes on both ends.

As mention in the first post adjustments will be in 0.7mm increments if done as a single adjuster.

 

Turn buckle style won't be any harder. Just drop the 1" bar and the 3/4 pipe to the machine shop and have him cut an internal thread on the pipe and turn down and cut a threat to fit it on the bar. Good thing with that is the CnC machine can turn a thread of whatever pitch i want.

I have spoken to the machine guy already and i remember thinking "shit thats cheap" Can't remember what it was but i'm thinking it was in the order of $30 so all the machine work would be under 100 clams. Materials will cost 20-30 bucks. + the bushes/rose joints.