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Old 7 Nov 2017, 06:34 (Ref:3779174)   #1
Trikes
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Join Date: Jan 2014
Australia
Australia Hobart
Posts: 43
Trikes should be qualifying in the top 10 on the grid
Rear Alignment Questions

Hey Guys Been a while. My Proton Satria GTi has been getting a hammering lately in the Hill Climbs. I know I'm improving as I keep lowering my PB's. This brings to my latest pickle. Recently I had Adjustable Rear Control Arms fitted with an alignment. The car is quite grippy now in the rear.

I recently competed (Hill Climbs) at three Meets in two weekends. The car copped a hammering. At one meeting it was regularly on two wheels thru a series of 5 corner 'S' Bends then at the last meet it was air born twice in the last three runs.

So the rear has 'settled' some 30mm lower and I'm wondering do I just wind it back up 30mm as that's where the alignment was set or will winding it alter the alignment???
Reason for wanting to go back up is the Turn In has changed since lowering itself. I now turn in, lift a little, then have to turn in some more to make the Apex.

Or do I lower the front 15mm and only raise the rear 15mm (I have ground clearance). (This FWD luvs 30mm of Rake). And get another alignment.

Strut type C/O suspension every corner.

Thoughts???
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Old 10 Oct 2018, 22:49 (Ref:3856007)   #2
sambeeb
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sambeeb should be qualifying in the top 10 on the grid
You're in a satria aren't you. I also hillclimb a FWD (with a rear beam though) and have had some pretty solid advice from a pretty solid race engineer lately that has helped transform my car. Based on what I've been told and have subsequently learnt I'd say that the turn in has changed as the rear ride height has dropped because the rear roll centre (and CoG) has moved downward. The flatter roll axis has the car more stable in the rear and therefore less pointy at the nose. If it has toed in at the rear as the ride height has dropped then that would have a huge effect too. I'd move the rear ride height back up to where it was. That'll get the rear roll centre back up (effectively stiffening the rear with geometric roll resistance) and making it livelier in the rear which will help you make the apex. Your car has rear IRS yeah? If the higher ride height gave you some total rear toe out then that would also explain how it wanted to turn better when the ride height was up a bit at the back. Don't drop the front or you'll just mangle your front roll centres if its a mac strut front end.
Mine is a rear twist/torsion beam. I'm running 2 degrees neg camber and 3.2mm rear toe out (total) and the thing just wants to turn now. The advice I've been given and what I have found is that toe out is huge when it comes to how little lock you'll have on at the apex. Provided you are adding camber at the same time (which really helps offset the high speed instability of rear toe out) then the car just comes alive.
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