froggy
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| posted on 17/12/13 at 08:15 PM |
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Bump steer advice ??
Been getting the front end ready and have the rack shortened and mocked up but am wondering wether my laser gear is the right way to go about
measuring bump steer
Setting them as I would at work lets you put the toe equally with the rack centered and locked and any toe change will show up on the front gauges
with good accuracy and any change will also show on the rear flags .
The wheels sit on cups with a bit of grease under them so they can slide .
So far I've got it thus
Full bump 2mm total toe in
Ride height parallel zero toe
Full droop 1mm total toe out
The rack is behind the axle line and the track rods run downhill slightly from track rod end to the rack . I'm not sure which way to move the
rack to improve it or if a bit of toe in under braking is a good thing , the more I read the more confusing it gets .
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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mark chandler
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| posted on 17/12/13 at 08:50 PM |
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A little toe in under braking will not hurt, when cruising the toe in compensates for the drag on the wheels so pulls them parallel when traveling,
start braking and the weight of the car is now trying to force the wheels from parallel so as the front dives adding a bit of extra toe will
compensate.
Regards Mark
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britishtrident
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| posted on 17/12/13 at 08:55 PM |
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It looks like the rack needs to be lowered on the the chassis,
For perfection you would need rose joints on the outers so you can spacer them up and down.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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drt
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| posted on 24/12/13 at 03:15 PM |
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as stated bump steer can be a good thing,
some racers prefer a little...
Not only for braking, but also to gain some toe mid corner so the car will be stable on a chosen line. etc
But if you want to minimise bumpsteer to the possible minimum,
The position of your steering joints (on the rack) can only be in 1 place.
geometrically (mathematically) determined.
I have a very simple diagram to help you establish this point.
If you want I could mail/PM it to you.
If you really want to go all the way ^^ I have heard of cars with a electronic system that tweeks the steering so that anything
from zero to ludicrous can be dialed in.
:p love the engine! what power are you hoping on? It will be quite an animal!
 with that kind of torque... 1 front wheel is bound to leave the ground... solving you bump steer 
Or as it looks like a ronchamp/haynes front design... it could bent  rendering your hard steeringgeometry effort to the bin
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froggy
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| posted on 25/12/13 at 12:34 PM |
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I've added a 6mm shim to allow the rack to come down a little but I'm going to try the current position and see how i feels .
The turbos are set for 6psi so around 375 hp with similar torque at quite low rpm as its 10-1 compression . If there was a simple way if getting a
manual box onto the Lexus lump they would be a lot more popular .
[IMG]http://i144.photobucket.com/albums/r187/froggy_0[IMG]
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Dan.
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| posted on 25/12/13 at 04:16 PM |
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Good to see the project is making progress mate :-)
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