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Bumpsteer elimination


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#41 xa1973

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Posted 14 April 2009 - 07:12 PM

Shit loads! I've met plenty over the years.


Ditto!!

And some real fine weasle stroppers at that.........

Thank flock I can do 90% of my own stuff........

#42 Toecutter

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Posted 14 April 2009 - 10:33 PM

Rev, you should post his details here. I'll look him up soon!

Sulio

#43 620Z

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Posted 15 April 2009 - 08:39 AM

Yeah Sulio get yours done before the Grampians drive.

#44 Toecutter

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Posted 15 April 2009 - 02:05 PM

Yeah Sulio get yours done before the Grampians drive.


just what I was thinking mate.

#45 Cdr Zero

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Posted 23 May 2009 - 11:13 AM

I really had enough of this whole 'bump steer' issue which was made even worse after doing some front end work on the springs, everytime there was even the hint of unevenness in the road my Zed followed it every time...I just had to hang on for the ride.  I was about to fit some bump steer spacers that Sulio had given me to try and while I was looking on the net at exactly how to fit them I noticed some info from a guy that said most of the time bump steer issues can be corrected or at least made tolerable by getting an 'old school' wheel guy to do an alignment and adjustment.  well I know one of these guys so I took the car to him and picked it up 2 hours later with bump steer problem 98% fixed!  He said that the guy who had aligned it before didn't get it right which was causing the issues...now it drives where I tell it to drive! No spacers required!
Rev.

Well I got new tires and a wheel alignment yesterday from Jax Quickfit tyres in Belconnen, and it's almost like a new car!  No bumpsteer at all, it's phenomal!  :) 

#46 Kodie

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Posted 06 November 2009 - 07:21 AM

Im dreadging here a bit, forgive me!

This thread is very confusing. lol!

Anyways, after reading through this basically the whole idea is to get a good wheel alingment and if the issue still exists due to be lowered beyond the limits of the standard suspension geometry then get a set of shortened steering arms?!


#47 NZeder

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Posted 06 November 2009 - 07:39 AM

if the issue still exists due to be lowered beyond the limits of the standard suspension geometry then get a set of shortened steering arms?!

Not quite - basically the fix is relocating the steering arms and or the lower control arms. The spacers move the lower control arms so the geo is almost back to the factory location however this does alter the roll centre which might be fine on a road car but a race car might have issues with this. The other fix is relocating the lower control arm mounting point. This as the same effect as the spacers - back to almost factory location but again roll centre altered. The other and more costly fix is new or altering (as in cut and weld) the steering arms which relocates the steering connection point (ie where the tie rod joins and thus changing the relationship with the lower control arm but not altering the roll centre)

Other have fixed the issue with custom tie rod ends using rose joints (might not be road legal in Oz but here in NZ it is ok with an engineering cert) and relocating the steering arm via a threaded tapered thing - not sure what they are called but here is pic
Posted Image

#48 Kodie

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Posted 06 November 2009 - 08:49 AM

Dont suppose you have a picture or diagram of the cut and weld required? You also mentioned a company back up a bit that makes a billet set, dont have there info do you?

#49 NZeder

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Posted 06 November 2009 - 01:33 PM

Not sure about the cut and weld - I did not like that idea :( anyway Stewart Wilkins Motorsport in NSW is the company in question - I have purchase a number of parts from them over the years and they are good to deal with. Here is a link to there site.

http://swmotorsport.com.au/

#50 Kodie

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Posted 06 November 2009 - 05:37 PM

cheers for that

#51 thehelix112

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Posted 13 November 2009 - 01:43 PM

Wow.  Lots of good information here, lots of not so good information too.

Modifying the front roll centre for a race-car is not necessarily bad, its just another tuning tool.  NZeder is right in as much as changing only the front one alters the relationship between front and rear, again, another tuning tool.  The downside of course is that its far more difficult to alter the rear roll centre so you become limited in what you should do with the front by the rear.

Other thing that perhaps bears mentioning is that you may be limited in how much you can space the outer tie-rod end attachment to the steering arm by your wheels.  I have 14" wheels on my zed in the states, and its awfully close:
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Also, I fail to see a reason why you can't use both the strut-spacers and adjust the inner LCA pivot.  The spacers adjust where in the bump-steer curve the suspension travels, the inner LCA pivot alters the bump-steer curve.

NZeder is on the money.  Make something to test the bump-steer and test it.  I need to, just haven't gotten around to it.  Excited to see what I might find. :)

Dave

#52 NZeder

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Posted 13 November 2009 - 06:14 PM

A mate emailed this link today - this is very well written and I recommend those interested in bump steer should have a read.

http://www.speedwaym...f/910-82700.pdf

#53 Riceburner

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Posted 21 February 2014 - 07:00 PM

Thread revival!!!

After seeing this linked in Vorns thread I went through it again twice, it becomes confusing with no conclusion.

My questions are:
1) Can you run roll centre spacers and raise the inner control arm pivot point? They do exactly the same thing don't they
2) If you raise the inner pivot point will you need longer arms to retain the same camber setting?
3) Are adjustable steering arms part of the solution to try and get them on the same arc as the control arm?
4) If yes to question three, are these suitable? http://www.zccjdm.co...OUTER_TIE_RODS_

#54 mossy

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Posted 22 February 2014 - 07:06 AM

I'm interested in this answer too, the only thing I think I understood is you can't run the spacers and raise the LCA together, it has to be one or the other.  Maybe Mike can post a pic of the part he installed?

#55 Riceburner

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Posted 22 February 2014 - 08:21 PM

I'm interested in this answer too, the only thing I think I understood is you can't run the spacers and raise the LCA together, it has to be one or the other.  Maybe Mike can post a pic of the part he installed?


Re-reading again, I see Helix says the inner pivot alters the bump steer curve. The spacers alter where in the curve the suspension travels.

So, doing both the spacer and inner pivot you will move the bump steer curve further than the original setup which was not ideal to begin with? But also perhaps a tie rod similar to the type pictured above to match the new angles.

There's also the question of control arm length, as I understand it if you go higher on the crossmember this will increase the distance from the inner pivot to the bottom of the strut. This would require a longer control arm to keep the same camber you had prior to the mod  :-\


#56 PeterAllen

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Posted 22 February 2014 - 08:55 PM

... This would require a longer control arm ...


The nominal relocation of the pivot bolt holes is not only18mm higher but also 6mm outwards, negating the need for longer arms. As 'Enzo' stated you are best to decide on the ride height and wheel/tyre setup of your particular car and then determine where to drill the new hole.

#57 Riceburner

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Posted 24 February 2014 - 11:10 PM

Thanks Peter.

Also is there a way to determine what height the shims need to be on the modified steering arms pictured above?

#58 mossy

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Posted 26 February 2014 - 10:23 AM

Thinking about getting some of these from Nagisa Auto in Japan

http://www.nagisa-au...0_s30_130z.html

I think this is what they look like though

http://www.jdmjunkie...s-arrived-here/
http://minkara.carvi.../blog/31281257/

#59 PeterAllen

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Posted 27 April 2014 - 02:15 PM

I drilled another cross-member today and took some photos of the process:

Mounted the cross-member on the mill.
Drilled new holes 19mm higher and 6mm outwards.
Made and fitted new spreader plates - the old ones were mangled when chiscelled off.
Filled the old holes with weld.

I still need to dress it all and have it media blasted prior to painting.

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#60 Riceburner

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Posted 28 April 2014 - 06:35 PM

Thanks Peter, It's always nice to have some pictures for the simpletons(me) amongst us  :)




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