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Help: Lowering the front end

 
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Qik Nip  



Joined: 16 Jan 2015
Posts: 115
Location: Kentucky

PostPosted: Sat Nov 12, 2016 9:00 am    Post subject: Help: Lowering the front end Reply with quote

Well I've sucessfully lowered the rear end and as the instructions I found here stated it was indeed a two time endeaver! The first attempt resulted in a seriously lowered car (6").
I've settled on 3.5" and now need to attack the front end to wit:
What is the max lowering I can accomplish while preserving my zero camber, max caster target?
It seems that the camber adjustment range of the eccentrics is about +/- two degrees. But based on my experiments it looks as though the geometry of the 924 (it's a '79) doesn't effect much camber change as the suspension moves up and down through its range. Is that factually correct? If so, that will make the task of matchinmg the rear ride height a lot less onerous.
Rick
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 695
Location: Maysville, Colorado

PostPosted: Sat Nov 12, 2016 1:17 pm    Post subject: Reply with quote

Check out the Newhill garage website. It did a section on measuring the camber change on an early 944 for spec racing. I have read that the camber change is quite low, but bump steer starts creeping into the equation.
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Qik Nip  



Joined: 16 Jan 2015
Posts: 115
Location: Kentucky

PostPosted: Sun Nov 13, 2016 8:15 am    Post subject: Reply with quote

Mike:
Thanks. That was really helpfull. Per the article I found on their site, my causual observation was confirmed...very litle camber change in compression!
Rick
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daniel  



Joined: 18 Jun 2009
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Location: Sydney, Australia

PostPosted: Mon Nov 14, 2016 12:58 pm    Post subject: Reply with quote

As a rule of thumb, do not let the control arms go past horizontal
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924RACR  



Joined: 29 Jul 2001
Posts: 8063
Location: Royal Oak, MI, USA

PostPosted: Mon Nov 14, 2016 11:41 pm    Post subject: Reply with quote

Yes, but sometimes the benefit to handling (lower CG) outweighs the negative of camber change - especially if you run stiff-enough springs, limiting the travel.

For straight-line top-speed stuff, the bump-steer's probably more important.

Rick, will they let you mess with geometry enough to reduce the bump steer? Rod ends in place of stock tie rod ends, and long bolts with spacers to adjust...
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Qik Nip  



Joined: 16 Jan 2015
Posts: 115
Location: Kentucky

PostPosted: Tue Nov 15, 2016 1:58 am    Post subject: Reply with quote

924RACR wrote:
Yes, but sometimes the benefit to handling (lower CG) outweighs the negative of camber change - especially if you run stiff-enough springs, limiting the travel.

For straight-line top-speed stuff, the bump-steer's probably more important.

Rick, will they let you mess with geometry enough to reduce the bump steer? Rod ends in place of stock tie rod ends, and long bolts with spacers to adjust...


Vaughan:
You're correct about bump steer in this situation, but I already have pretty stiff front spings and after I cut them sufficiently to drop the front three inches they will get even a stiffer! So the front end which doesn't move much now, will be even less compliant. In addition I have double adjustabler Koni's on the front set on full stiff (both rebound and compression).

My primary consern will be to preserve maximum caster while acheiving zero camber. Regarding caster however, if I have to use all of the camber adjustment to get to zero, will I loose caster?

As for the steering linkeage, yes I can modify it. On that point, can you expand your thoughts in the last sentence? I'm unsure what exactly you're referring to.
Rick
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924RACR  



Joined: 29 Jul 2001
Posts: 8063
Location: Royal Oak, MI, USA

PostPosted: Tue Nov 15, 2016 5:15 am    Post subject: Reply with quote

Not sure where you'll end up with the caster/camber adjustment. Obviously, adding in adjustable plates for same at the top of the struts will help, if legal for your class and in budget.

Regarding the latter... if you drill though the steering arms on the knuckles (turning the tapered hole into a straight through hole), then replace the tie rod ends with normal racing-style rod ends/Rose joints/Heim joints, then you can drop them down lower than stock with a spacer and a long through-bolt, fixing the geometry and removing the additional bump-steer.
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Rasta Monsta  



Joined: 12 Jul 2006
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PostPosted: Tue Nov 15, 2016 5:59 am    Post subject: Reply with quote

You'll also have to check the rules on bump steer modifications...not legal in all classes.
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