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Suspension analysis

 
Old 10-09-2016, 01:07 PM
  #11  
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For some reason I cannot modify my first post, but here are some results.
I have been actually doing some further research on drops and bump steer and I think I was wrong with my first statement. The bump steer kit will actually make it worse as per my calculations.
It is true that the angle of the track rod will be greater if you lower it, but, as per my calculations, the bump steer (or toe change with wheel travel) will be better (less toe change).


Nevertheless, I believe that bump steer should not be too bad in a lowered car. Other thing is that if you use wider track with new wheels, the scrub radious (or KPI at ground) will be significant and bump steer "feeling" will be multiplied.
Details about the model:
I have now lowered the car to a streetable -25-30mm front and -20-25mm rear from stock. Also take into account that my current track width is 90mm wider on the front from stock 16" OEM wheels, however the results obtained by rising or lowering the steering rack might be similar.
Here is the model with -2.4º camber and my current set-up (buddyclub adjustable lower wishbone ball joints + top adjustable japspeed wishbone).
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I have now got the front inst. centre of rotation inside the track width (OEM was quite far away when lowered), in order to obtain more camber gain with travel. However, the con is that roll centre height is a bit higher. Due to a relative high front CG, the roll moment is quite important and can make the inner rear wheel lift (or jack), so, by rising the roll centre, at least, you are able to reduce the roll moment (distance between roll centre and CG), and making it similar to the rear and avoiding rear inner wheel lifting.

So for this set-up here is the bump-steer (or toe change with wheel travel as above-mentioned):
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Here is the result with the bump-steer kit of 12mm (you can just use some high grade washers, J):
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However, if you could actually "shaved" 12mm from the steering rack and therefore increasing the angle of the steering rod (or track rod), the result would be as follows:
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That is quite interesting to find out actually. One of the gurus from S2ki (Rob Robinette) actually mentioned that he didn´t notice any difference in handling with the kit installed. I have read his blog many times and his statements are usually very well established and studied, so make your mind really
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Old 10-09-2016, 01:30 PM
  #12  
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In case you are interested in my new set-up, here are some pictures of the buddyclub front adjustable lower ball joint and the japspeed adjustable front upper arm against the OEM.

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I am planning actually to use the Buddyclub ball joint in the other way around.
These are designed to only work to give extra camber


here some pics installed at someone´s s2000:



As I have increased the track width by a good margin, I am trying to reduce scrub radious. Therefore, I will flip over the buddyclub ball joints and will use the adjustable plate to put the upright inwards (and therefore will give me less camber or more positive camber) and keeping the ball joint in the same position but closer to the wheel contact patch therefore reducing scrub radious.
I will compensate the camber with the shorter effective length upper arm (Japspeed) that will also give me less scrub radious too.

My calculations show that with the Buddyclub ball joint to the maximum inward position adjustment + maximum camber with the Japspeed wishbone + adjustment of the OEM camber GEO bolt I´ll be able to get -2, -3º camber maintaining the original 6-7º caster.
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Old 10-09-2016, 01:44 PM
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Hope you can get it close with the amount of offset you have with spacers
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Old 10-09-2016, 01:45 PM
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Originally Posted by noodels View Post
Hope you can get it close with the amount of offset you have with spacers
no spacers. Only with new wheels: Advan RG2 17x9" et30
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Old 10-09-2016, 01:47 PM
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Ok missed that,
thought you had OEM 16s
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Old 10-09-2016, 01:49 PM
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Oh yes the DIY spacers washers,
was thinking of that also, but less than 12mm
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Old 10-09-2016, 01:55 PM
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Originally Posted by noodels View Post
Oh yes the DIY spacers washers,
was thinking of that also, but less than 12mm
well, after my calculations, I´d say that you don´t need them...
Even if you are thinking of using the offset track rod ends, that will make bump-steer worse also:



Although will give you better ackermann angle
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Old 10-09-2016, 11:08 PM
  #18  
 
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Originally Posted by mantecosa View Post
Originally Posted by noodels' timestamp='1476049760' post='24080192
Oh yes the DIY spacers washers,
was thinking of that also, but less than 12mm
well, after my calculations, I´d say that you don´t need them...
Even if you are thinking of using the offset track rod ends, that will make bump-steer worse also:



Although will give you better ackermann angle
I've being saying for a long time that you just can't bolt on a spaces from a tuning shop to fix bump steer the best way is to check it with a bump steer gauge then space the rack or track rod ends like the ones above to get the best result possible
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Old 10-10-2016, 12:36 AM
  #19  
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Because of the ride height on mine (and anyone else running a very lowered S2000) you do need to run RCAs and I had to use adjustable camber arms, or you completely run out of camber adjustment.



Adjusting suspension / geo settings and using RCAs is nothing new - some good info here.

https://robrobinette.com/S2000Alignment.htm
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Old 10-10-2016, 12:53 AM
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