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Bumpsteer elimination


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#21 zzzzed

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Posted 21 January 2009 - 08:21 PM

Wold it be lowering the rack? If so this would mean steering colum mods as well. I hate being left in suspence lol

#22 NZeder

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Posted 21 January 2009 - 08:31 PM

I'm pretty sure I know what Mike is referring to - it's the oldest method in the book.
Get a hold of a book buy 'Fred Punn' & all will be revield...

Your on to it  ;D

Wold it be lowering the rack? If so this would mean steering colum mods as well. I hate being left in suspence lol

well not quite - this was discussed earlier also and the answer was again given on this site....ok little hit. Visit the members project section. There is are two projects that talk of these issues but one I am talking about is a car from NSW and post 78 and 83 talk about the issue in question and the best solution - as it fixes the issue and also had the side effect of fixing another issue.

Not sure why so many people miss this and go for the move the LCA or install spacers - only reason I can think of is they don't want to spend the time it takes to test different setup - but the result will be the same and it is opposite of what you think.

#23 zedevan

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Posted 22 January 2009 - 09:49 AM

any ideas on the price of the product mentioned in posts 78 and 83? i could only find reference to the fact it was expensive!

did you end up making your own then NZeder - or order them through the said company in NSW?

i am confused as to how this is the oldest method in the book, or is that just because i have no idea how their product is different to the stock items?

#24 NZeder

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Posted 22 January 2009 - 10:44 AM

I went for the items made by the NSW company. Cost....... well for the cut and shut of the original part like they do in Japan around $350 AUD. But for the custom billet unit more than double that. I did not want something that was weld in this area and I am sure when I come to get my car engineered for the road the engineer will be pleased that I went with the billet unit. It might be a lot of $$ but it fixes the problem and is still only 10% of the car cost me to purchase in the first place (forget all the $$ that have gone into other suspension, brake parts - hell might be around 10% of those parts too)

Given my project has been 11 years in the making a few $1000 each year makes up for alot of parts ie what I don't spend in petrol with it off the road goes into good bits ;)

#25 620Z

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Posted 22 January 2009 - 11:55 AM

After moving the LCA on my car I installed rose joints & small spacers on the end of my steering arms per attached. Reasonably priced and my car has absolutely no bump steer. Drives like a normal car! The car is now safe to drive on those rough raods without running off into the bushes or gripping the wheel like my life depended on it. you know what i mean.   ;)

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#26 zedevan

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Posted 22 January 2009 - 11:57 AM

is this something Arizona Z Car makes a correction for too?

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#27 Zedman240®

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Posted 22 January 2009 - 12:12 PM

I have seen the AZC version but it incorperates a spacer with it. Its not in the pic zedevan (hidden by the tyre). Would the AZC be a good one? Heard it speeds up steering response too.

#28 NZeder

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Posted 22 January 2009 - 12:55 PM

is this something Arizona Z Car makes a correction for too?

Posted Image

He does not fix the issues with his part you are thinking of. Most of the US guys are still doing the same thing - move the LCA and or spacers between the steering arm and strut aka Roll Centre adjusters (don't call them bumpsteer spacers as they really alter the roll centre and a side effect is a lower end of the control arm = you have to move the arm more to get bumpsteer but the issue is still there if you can more the arm enough while on the road or the track.

My point is don't move the problem - fix it.

After moving the LCA on my car I installed rose joints & small spacers on the end of my steering arms per attached. Reasonably priced and my car has absolutely no bump steer. Drives like a normal car! The car is now safe to drive on those rough raods without running off into the bushes or gripping the wheel like my life depended on it. you know what i mean.   ;)

Yes you have removed the bumpsteer you can feel I can also tell you that looking at the pic of your result it will still be there :( it is just so high up in the suspension travel that you will never find it unless you run without springs. Again the same point don't move the problem fix it.

My mates race car has the same setup as you ie rose joint and special tapered bolt and we thought we had it when the setup looked like yours. However the end result was very different as we found with the setup like yours bumpsteer was still there in the upper part of the travel. Do a google on how to make a quick and dirty tool to measure the bumpsteer. Make the device, remove the springs from your car and using a jack while someone is in the car holding the steering wheel locked in the straight ahead position (this is key to a good reading from your home made device) and move the suspension through the travel and monitor the changes in toe both in and out aka bumpsteer. Now have a play with your rose joint location with a number of different size spacers etc moving the steering arm up and down and record your results - I think you will find some unexpected results like we did.

As stated we thought we had it when the setup looked like yours but it can be improved on :)

#29 stevo_gj

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Posted 22 January 2009 - 01:09 PM

Wiki says: "Excessive bump steer increases tire wear and makes the vehicle more difficult to handle on rough roads."

Isn't moving it so that you can't feel it about as good as getting rid of it entirely?

I must be missing something...

#30 Lurch ™

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Posted 22 January 2009 - 01:11 PM

My only concern with the steering arm mod Mike mentions is changeing Ackerman slightly, but that might not be of much concern...

#31 620Z

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Posted 22 January 2009 - 01:37 PM

I am a bit with you Stevo. I won't be bothering going any further on my steering apart from installing a (Power Steering) Rack which I have at home. I don't feel any movement or wondering anymore. To me problem solved. I guess I might be offering some readers a slightly cheaper and less sophisticated fix. You might be right that it might not be perfect Nzeder.
But if I had bottomless pockets etc I would be going down the double wishbone set up etc. But I think I would just get a new car before going down that route. Besides if I did do the DWBone fix I would be lucky to pick up half a second around the track. 10K or more for a possible half a second. Hmm Not high on my priority list at the moment. Just view my set up as an alternative.  ;)

#32 NZeder

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Posted 22 January 2009 - 06:36 PM

I re-read my suspension book and moving the LCA does have some benefits. This relates to the length of arm and how it changes as it move up and down ie appears to get longer thus changing the toe and camber settings and thus bumpsteer - the steering arm mod also as the same effect on the toe issue but no so much camber.

This all gets complex and ackerman is very complex. I recall one local zed racer told me he never had any bumpsteer issues on his car every with no mods at all. However he was running 600lb springs in the front = suspension was not moving much = never causing issues anyway. Not a road car I might add.

For a road car the LCA and spacers are the most affordable solution. Next step is the setup like ZZZ8 with a rose joint and new tie rod setup that allows you to move the point of the steering and tie rod join. The new steer arm is the most $$ and can get the same result as ZZZ8 solution. I have gone the arm method as the local road rules don't like rose joints on the steering - it can be done but there can be too much paper work and hoops to jump so I have gone this path for now. Who knows I might end up with the ZZZ8 mod depends if I change the purpose of the car from road part time track to track and part time road.

#33 stevo_gj

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Posted 22 January 2009 - 08:17 PM

For a road car the LCA and spacers are the most affordable solution.


Just want to check you mean LCA OR spacers, right? :)

#34 NZeder

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Posted 22 January 2009 - 09:00 PM

Just want to check you mean LCA OR spacers, right? :)

yes OR not both

#35 RBZ 260

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Posted 23 January 2009 - 12:48 PM

im still waiting for this top secret thingy.  ::) now theres lot of do's and don't or mask's etc..... in simple terms please!

dont get it whats the big secret but anyway:

The best solution the steering geomoetry to be parallel to the lower control arm? YES/NO (not asking how its done just whats the ideal)

I had this issue while my Z has power steering and different hubs etc....... geometry was close or bit better than stock (what the wheel alignment guy told me)  but it still bumpsteered madly till i replaced the front tyres with new ones and the problem gone away totaly. now did it mask it or the issue from day one was dodgy tyres?

Even though it drives nice now this being my first and only z i ever driven im not sure how they handle. to me handles fairly good for the suspension i got comparing it to my s14 200sx. But maybe its not as good as it should be. hence the interest in this topic.





#36 NZeder

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Posted 23 January 2009 - 02:35 PM

no big secret you stated that answer already - just different ways of getting there and each with different merits. Some changing other things for the better others for the worse - and it does depend on what you are willing to compromise on remove bumpsteer and upset the front to rear roll centres (and what that brings) etc.

Basically we are trying to fix issues that are in the design of the factory setup that you find only when you lower the car.

Maybe the ideal solution is remove the McPherson strut and spend $$$ and install a custom double a-arm/wishbone setup but that is a lot of work and engineering for how much gain?

I see guys spend lots of time and $$ installing S14 or R32 rear end into a 240z (sorry Gajin) when the issue is not the rear suspension setup in the 240z the front has more issues than the rear + why add all that extra S14/R32 (whatever) weight? Sorry I don't get that one.

#37 RBZ 260

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Posted 23 January 2009 - 02:54 PM

Nzeder

thanks for clarifying that.

im kinda the black sheep since i have mazda rx7 hubs and front struts with few other tricks to make it all work. initaly i thought that was the main issue for the bumpsteer but the geometry seemed fairly good to compensate for all that.

though the car is not super low but it is lowered a fair bit.  the steering arms and control arms are almost parallel when sitting on flat ground. if bit lower it would be perfectly parallel.

my steering guy sugested to change my dodgy tyres and it most probably disapear. which it did.

at the moment is very good to drive. i can drive it fast on rough roads and still go straight. Before that anything above 75kmh  i had to wrestle with it.

thanks for pointers so i was on the right track.



#38 reverendzed

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Posted 13 April 2009 - 09:01 PM

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.

#39 Cdr Zero

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Posted 13 April 2009 - 10:19 PM

Now isn't that amazing... Geez you wonder how much dodgy auto guys end up costing you in the end hey...

#40 620Z

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Posted 14 April 2009 - 08:33 AM

Shit loads! I've met plenty over the years.
Good to hear the car is driving a lot better Rev.




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