|
|
|
 |
 |
 |
You are not logged in. Would you like to login?
Offline
Hey everyone, My names Ben, Im an automotive engineer and fabricator, My background is from being a dealership mechanic to building rollcages, engine conversions etc. But my suspension setup knowledge is rather limited.
I have a bagged Toyota Hilux/pickup (not sure what you call them, Im from NZ), I have a Toyota Soarer IRS unit that I want to graft into the back, I want to narrow the origional subframe and then use it to build a jig for making the control arm mounts in the new RHS rear clip similar to this one
Now I have a couple of questions, I'll post a pic of the setup Im using below
In the pic the vehicle would be travelling to the right, so the right of the pic is the front ofthe setup. Now what Im wanting to know is why the upper control arm is angled the way it is? is it to do with antisquat? and if I put this setup into a ute will I need to copy this angle or will I be better off running the arm pivots parallel?
Also is there any other issues you can think of that I might need to keep an eye out for?
Cheers
Ben
Offline
Ben,
Welcome, your in an area I have done little research in (wishbone). However when you start changing geometry it's best to have your facts straight. You know that and that's why your asking. I found this link below that has pics of the upper control arm UCA and I see it is angled in more ways than one. I would guess it is for added anti-dive/squat.
Ralphy
Last edited by Ralphy (11/02/2011 4:27 am)
Offline
first of all welcome to the forum!!! I find the first picture interesting, I have seen lots of IRS units where the half shaft serves as the upper control arm, but this is the first one I have seen where it is the lower. I see your set up has the upper UCA and links as a LCA are you planning on running it that way or use the half shaft as a lower control arm??
As to your questions the angle of the upper arm is going to add a little bit of for and aft arc in to the suspension travel. assuming the arm is parallel to the ground at normal ride height than as the top of the hub mount would move forward (to the right) as the suspension travels either up or down. which would be the opposite of anti squat. So I would guess that the arm angled down at normal ride height?? If so that would be as you thought, some anti-squat. It also could change caster through suspension travel depending on how stable the lower links are.
as to your question:
DVSLUX wrote:
Now what Im wanting to know is why the upper control arm is angled the way it is? is it to do with anti-squat? and if I put this setup into a ute will I need to copy this angle or will I be better off running the arm pivots parallel?
That is a loaded question. A lot of people would say "that is how it was done by the factory" but unless you are setting up everything just the way the factory did than that line of thinking does not work.
It sounds to me like you are modifying the entire IRS set up so I think I would simplify things and make the control arms perpendicular to the car. than you can add in the other things like anti-squat by making other suspension adjustments.
Offline
Toyota Soarer...that's our Lexus SC300/SC400 over here. Seems to be pretty typical of '90s Toyota/Lexus RWD design.
It's got three separate lower links; it looks like the main camber-control elements are the upper arm, the rear lower arm and the front trailing link - the axis of the inner pivots of those links is more or less parallel to the upper arm inner pivot axis - while the front lateral link is there mainly to control toe but it's rather difficult to visualize the exact interplay of all their arcs. If I'm right it's geometrically a fair bit like a DEW98 Lincoln LS/Jag S-type rear.
If I were you I'd set the thing up at normal ride height position, bolt a 2ft (okay, 600mm for you folks) long stick onto the hub parallel to the ground as a toe reference, stick a magnetic protractor on there vertically as a camber reference, and measure camber and toe change through 2-3in of bump and 2in of droop travel.
Then just bolt it up and run it if the track width is right and it clears everything. I wouldn't go fiddle-futzing with the upper arm angles unless I had some way of modeling everything it does in software. You'd probably find out more about the ins and outs of that design at some of the MkIV Supra, etc. forums if you wanted to spend the time.
Last edited by JEM (11/02/2011 3:13 pm)
Offline
Hey Guys, thank you for the warm welcome and the very quick replies.
Ralphy, thank you for that link, the subframe, arms and hubs are exactly what Im using.
Daze, I will be keeping the lower arms, this setup uses CV shafts that wont handle the stresses of being used as a control arm as well. As for how the upper control arm sat at ride height origionally Im not sure at all, being from the soarer/SC400, it came out factory with airbag height adjustable suspension (which is a similar setup to what Im going to run) so I would have to assume its desgined for multiple ride heights.
I know what you mean about the "this was how the factory did it" mind set, I have came accross this and have also thought it myself, I mean the manufaturer spent a lot of money and time designing this system to work correctly, but as you say, its no longer sitting in a soarer.
Yes, the way Im doing it I can pretty much set it up how ever I want it.
Jem, I think I do need to do your suggestion of using a long stick etc on the hub and find out exactly what is happening throughout the suspension travel.
Now how important actually is it to have anti squat? if it ends up with nothing at all what side effects am I going to have from this?
Thread StarterOffline
Two things I see, first the upper is set to pivot forward this shortens the wheel base under jounce. Not sure how the forward lower trailing link mounts, but if it's set horizontal the wheel base will shorten. So does the hub move forward or does it rotate? It depends how that lower is mounted. Second it appears the front lower toe rod is way longer than the rear this would cause the rears to toe out under jounce maybe. Performance wise two conditions your not looking for. Pictures do not tell the whole story you really have to see it set up in the car. Just like real-estate location, location, location!
1 of 1