Tony Posted April 11, 2009 Report Share Posted April 11, 2009 Pre-2000 they had adjusters installed.. as for the lock!! on full lock it looks like the wheel has fallen off The SR migration you need to do in your head by watching the angles move, i also have the roll force lever to help me but i still prefer to watch the migration lock-on-lock. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 12, 2009 Author Report Share Posted April 12, 2009 So what's happening to the tyre to cause roll-over wear ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 13, 2009 Report Share Posted April 13, 2009 So what's happening to the tyre to cause roll-over wear ? I'm going to do me best to explain this but it won't be easy, hence the pictures i posted.... Deep breath our example has NSF -1d 29 camber 2d 56 castor +18' toe There's nothing remarkable going on, on a left turn, as for right...... At 20 degrees the camber has migrated with an additional -13', the castor has retracted around 3 degrees and there's an obvious disparity in the toot (only visible by the toe angles) The SAI has declined (more angle) and it's position is more set-back in a transverse/ perpendicular position. Since the camber has migrated and there's more declination in the SAI then the SR has moved to the wrong position IE: outside of the steering pivotal axis. This position suspends the cars weight incorrectly distorting the tyres contact patch conically, meaning the inside of the tyre holds to much weight and the conical distortion allows the tyre to "roll over" transversely, this is also called "pneumatic slip angle". Point to remember is that the SR is to far "outside" of the pivitol axis not inside! Quote Link to comment Share on other sites More sharing options...
CIH Posted April 13, 2009 Author Report Share Posted April 13, 2009 "Steering pivotal axis" ? Quote Link to comment Share on other sites More sharing options...
CIH Posted April 14, 2009 Author Report Share Posted April 14, 2009 This is what I noticed when I was playing with toe in Forza; Quote Link to comment Share on other sites More sharing options...
Tony Posted April 14, 2009 Report Share Posted April 14, 2009 This is what I noticed when I was playing with toe in Forza; Looks like the toe setting screen? The steering pivotal axis is the area that's governed by the ball-joints turning range, the suspensions articulation (bump/ droop) and the actual geometric angles. See it as the design limitations and your geometric focal point. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 15, 2009 Author Report Share Posted April 15, 2009 That wasn't so hard to grasp! As for Forza, look at the plus/minus positions. Putting in a positive firgure results in Toe-out. Terminology is wrong. (I think ? isn't it ? ulp!) Anyway, running what the game describes as a "-" toe figure, the cars behave exactly as desribed with toe-in ie; progressive oversteer on throttle, not to mention far better traction. I can make a concious descision to either drift round a corner or use a proper racing line. Only problem is it's much fun pushing the limits, looking for an awesome reply of the drift, my times have taken a beating . Not to mention the "car". Currently running a 270bhp Nissan Silvia S14 (actually a tuned yank 240SX SE 2.4 N/A) to "clubman" spec Quote Link to comment Share on other sites More sharing options...
Tony Posted April 15, 2009 Report Share Posted April 15, 2009 Toe angles.... let's say toe out generate lateral displacement of the tyres sidewall, in the case of toe out it would be the inner wall..... Depending on the degree of toe out you can control the tyres saturation limits where at saturation the tyre will loss grip..... and saturate. The lateral displacement in the longitudinal plane is more or less undiscernable until thrust or deduction of thrust is applied/ denied, this encourages a snap reaction from the tyres sidewall making the car move erratically one direction and/ or the other. This "snap" reaction is desirable in motorstorts and plays a major roll in "progressive" oversteer, where the progression is controlled by the application of thrust plus the transitional lateral forces applied to the tyres limits during the addition of inertia. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 16, 2009 Author Report Share Posted April 16, 2009 so does the tyre's sidewall store energy during such displacement ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 16, 2009 Report Share Posted April 16, 2009 so does the tyre's sidewall store energy during such displacement ? Massively..... Under acceleration the lateral forces twist the sidewall until either thrust is reduced or the tyre saturates losing all traction.... Domestically this condition could be described (rwd) as pulling one direction under acceleration then the other during deceleration. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 17, 2009 Author Report Share Posted April 17, 2009 Do different sidewall charicteristics change this effect ie; soft micheclin, stiff bridgestones or silly stiff Rft ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 17, 2009 Report Share Posted April 17, 2009 Do different sidewall charicteristics change this effect ie; soft micheclin, stiff bridgestones or silly stiff Rft ? Yes, the harder the wall, the less lateral compression is desired front and rear..... All i do is set the toe's to 0 then pull down the car and watch the tendency's, once established i calculate the static figure for a dynamic 0 Quote Link to comment Share on other sites More sharing options...
CIH Posted April 17, 2009 Author Report Share Posted April 17, 2009 I take it that's for the front ? btw, isn't it nice when you make a judgement-call based on tyre wear and the geo reading confirms it ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 17, 2009 Report Share Posted April 17, 2009 I take it that's for the front ? btw, isn't it nice when you make a judgement-call based on tyre wear and the geo reading confirms it ? No front and rear depending on the complaint/ tyre/ mods to the car..... And yes it is nice to predict in advance of a Geo, that's what makes an exceptional operator Quote Link to comment Share on other sites More sharing options...
CIH Posted April 17, 2009 Author Report Share Posted April 17, 2009 I wouldn't have thought there'd be many cars that would run a dynamic 0 toe on the rear (regardless of mods etc) ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 17, 2009 Report Share Posted April 17, 2009 All domestic cars desire a zero dynamic toe... Static positions calculate, drive/ bushing compliance and rolling resistance. Incorrect domestic dynamic toe fills a whole host of complaints, from tyre wear to oversteer and nervousness in the steering. As a modified tuning tool toe is great, domestically incorrect toe is a nemesis. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 19, 2009 Author Report Share Posted April 19, 2009 Do different sidewall charicteristics change this effect ie; soft micheclin, stiff bridgestones or silly stiff Rft ? Yes, the harder the wall, the less lateral compression is desired front and rear..... All i do is set the toe's to 0 then pull down the car and watch the tendency's, once established i calculate the static figure for a dynamic 0 And stretched tyres with no give in the "sidewall" ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 19, 2009 Report Share Posted April 19, 2009 Do different sidewall charicteristics change this effect ie; soft micheclin, stiff bridgestones or silly stiff Rft ? Yes, the harder the wall, the less lateral compression is desired front and rear..... All i do is set the toe's to 0 then pull down the car and watch the tendency's, once established i calculate the static figure for a dynamic 0 And stretched tyres with no give in the "sidewall" ? Need a calculated zero on bump and rebound (pull down/ push up) and watch the tendency on the screen..... A little math then you have the perfect static toe value. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 20, 2009 Author Report Share Posted April 20, 2009 but presumeably they have see no/minimal lateral compression with a distressed sidewall ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 20, 2009 Report Share Posted April 20, 2009 No, that's a dynamic thing.... I'm more concerned with the compression/ bump tendency which is a consistent arc whatever the lateral accel Quote Link to comment Share on other sites More sharing options...
CIH Posted April 21, 2009 Author Report Share Posted April 21, 2009 Got hold of an Autodata Alignment manual btw. Last years so it was cheap but atleast I have all the rideheight measuring diagrams and what not. Quote Link to comment Share on other sites More sharing options...
Tony Posted April 21, 2009 Report Share Posted April 21, 2009 Got hold of an Autodata Alignment manual btw. Last years so it was cheap but atleast I have all the rideheight measuring diagrams and what not. Good for you.... look at that and study it every time, there's loads of info there your not aware of. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 22, 2009 Author Report Share Posted April 22, 2009 so most (if not all) manufacturers aim for dynamic zero toe ? That is, to eliminate any toe based handling shenanigans ? Quote Link to comment Share on other sites More sharing options...
Tony Posted April 22, 2009 Report Share Posted April 22, 2009 Yes.... Static toe in/out is dependant on the effect of the drive on the bushings compliance during thrust..... A FWD normally has a static toe out, this is because as thrust is applied the front will compress the bushings then pull the car... The actual position for the static toe out is not law because there is an element of wear in the bushings. You do not need anything other than zero dynamic toe unless specific handling traits are desired where tyre wear is not a concern. In addition to all that is the toe tendency, just to complicate things. Quote Link to comment Share on other sites More sharing options...
CIH Posted April 22, 2009 Author Report Share Posted April 22, 2009 same with something faily agressive ? Like, say, a 330CI with IIRC +20 minutes total rear toe ? Quote Link to comment Share on other sites More sharing options...
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