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  #81  
Old 06-08-2010, 10:53 PM
Full-Race Geoff Full-Race Geoff is offline
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Quote:
Originally Posted by logr View Post
Geoff, Are you 12.5 longer due to a longer LCA?
When I had the ratio off with a longer traction rod, it was amazing how loose the car was. Drifters take note.

Isn't it interesting that the STOCK ration Traction to UCA gives the best/least toe change. Nissan engineers must be fairly sharp.

After lowering my car and looking at everything, it seems that the rear lower control arm is almost level but the upper arms are at quite an angle. Will lowering the ball joint do much for roll center/anything given that it is almost level when lowered? I believe the camber gain will still be there either way and I can't see it helping bump steer either.

Thoughts?

OOPS i edited my post -- i posted 12.5mm -- i meant +6.5mm !! = ~1/4" as in epsteins charts. i wrote 1/2"

dont worry about the angles of the arm -- worry about bumpsteer for a given wheel travel range, and then keep the hub there. to keep the hub in that position while you adjust roll center, you must lengthen the LCA accordingly. but there is no need to look at the angles of the arms and come to any conclusions

Last edited by Full-Race Geoff; 04-11-2011 at 05:01 PM..
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  #82  
Old 06-08-2010, 11:25 PM
cheeky14 cheeky14 is offline
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Thanks for the insight Geoff
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  #83  
Old 04-11-2011, 01:32 PM
Black R Black R is offline
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This is much delayed I'm sure, but did you try 12.00" length ruca?

What would be the effect?
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  #84  
Old 04-11-2011, 04:58 PM
Epstein Epstein is offline
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I haven't owned a 240sx in a while now.

If you look at the graphs, the trend is there but it's just not clear. The three lines rotate clockwise if you look at the 12.50" vs 12.25" graphs. With a 12.00" Ruca, it would rotate even farther clockwise, where bumpsteer would be minimized with a traction arm between 8.00 and 8.25". That combination would give you a pile of camber, though.
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  #85  
Old 08-19-2012, 11:05 PM
cheeky14 cheeky14 is offline
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Hey Guys, so i got around to bumpsteering the rear of my S14, i have the Def/Skullworks rear sphericals on Z32 knuckles & peak perf. arms/SPL parts RUCA, stock lower cont. arms with Nismo bush. my rear center hub to edge of fender heights are about the same as Epstein,

The RUCA arm length is about 12.25 & trac. arm is 8.25 (this is my starting point) my initial readings from static height to 1in. bump, .155" toe in & in droop .95" toe out

I adjusted the Ruca to 12.25 & trac. arm to 8.50 & my readings are out of wack compared to what Epstein came up with on the graph for these length; 0-1" bump .100" toe out, droop .162" toe in, then i tried different lengths on the trac. arm & it seems like running the trac arm all the way short made the readings lower & making arm longer readings are higher,

the veh. has not been in any accidents. i played with camber eccentric(set full neg.) toe eccentric set in the middle, will keep trying to get readings as low as the 12.25/8.50 graph.

Have you guys had similar results (i know different static heights will affect readings)
Any suggestions????

Last edited by cheeky14; 08-19-2012 at 11:08 PM.. Reason: clarifacation
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  #86  
Old 08-20-2012, 05:40 AM
Full-Race Geoff Full-Race Geoff is offline
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can you share some more info, maybe post a pic of your setup? did you do the front end also
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  #87  
Old 08-20-2012, 07:37 AM
cheeky14 cheeky14 is offline
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I will take some pics tommorow, (i have veh. at my parents place; will make time to run over there & take pics)

thanks
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  #88  
Old 08-20-2012, 09:01 AM
Jason M Jason M is offline
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I've done lots of bumpsteer measuring on my s13 rear subframe. Running the rear trac arm way longer then the standard 240sx internet setup, or "rule of thumb" helped limit toe change. When you lengthen the upper control arm to reduce negative camber, it rolls the spindle which moves the toe arm, lengthening the trac arm rolls the spindle rearward which moves the toe arm downwards.

You have a lot of toe change. I've got my rear trac at 9+", and run 1.8-2.2 degrees negative camber, but don't remember my ruca numbers off the top of my head. I can get toe change down below 1mm through several inches of travel. I have a big thread with lots of info, if you are interested. It's in the alignment section somewhere...
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  #89  
Old 08-20-2012, 09:40 AM
Beejis60 Beejis60 is offline
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Quote:
Originally Posted by Jason M View Post
I've done lots of bumpsteer measuring on my s13 rear subframe. Running the rear trac arm way longer then the standard 240sx internet setup, or "rule of thumb" helped limit toe change. When you lengthen the upper control arm to reduce negative camber, it rolls the spindle which moves the toe arm, lengthening the trac arm rolls the spindle rearward which moves the toe arm downwards.

You have a lot of toe change. I've got my rear trac at 9+", and run 1.8-2.2 degrees negative camber, but don't remember my ruca numbers off the top of my head. I can get toe change down below 1mm through several inches of travel. I have a big thread with lots of info, if you are interested. It's in the alignment section somewhere...
I'd love to have/see all your settings for arm length, if possible. Is it in that thread? Have a rough estimate what page or post?
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  #90  
Old 08-20-2012, 10:47 AM
Jason M Jason M is offline
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I'am going to bumpsteer the front of the car & mod or build new spidles this fall. I also need to biuld some new rlca's for my s14 subframe so I can start devolping that aswell...
Here is my thread.
http://www.nissanroadracing.com/showthread.php?t=2674

EDIT: One thing I want to say about my data, is that I should of converted the Long Acre Gauge numbers to degrees, to make the numbers more relavent to the actual toe change of the tire, which changes based on tire diameter.
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Last edited by Jason M; 08-20-2012 at 11:37 AM..
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