nobbie Posted January 4, 2014 Report Share Posted January 4, 2014 Hi Tony/guys, It been a while since I've been in, hope everything in WIM land is still good. Is that Vmax still in the corner of the workshop? I've just changed the shocks on my mk4(g) Astra Gsi, to spax, along with Eibach Pro Lowering springs. I've put the car on a new hunter hawkeye system, and they have 3 setting to match to, standard, sport and rough(I think). The car is now lowered, so decided on using the std settings, but not weighting the car. The camber was still out, so have installed the camber bolts now, and will be getting it tweaked again. I wondered whether that was the right setting. What are the differences between them? Thanks Quote Link to comment Share on other sites More sharing options...
Tony Posted January 4, 2014 Report Share Posted January 4, 2014 STD settings are redundant now since the suspensions not stock.... Does your car have a rear beam or is it interdependent suspension? Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 4, 2014 Author Report Share Posted January 4, 2014 Rear beam, fixed and std. Miss my Scooby, that was fully adjustable:( Quote Link to comment Share on other sites More sharing options...
Tony Posted January 4, 2014 Report Share Posted January 4, 2014 Fixed beam means the rear camber has a near vertical drop so no gain. In this event the front camber would need to be dialled out leaving a front to rear disparity of around a degree. Example if the rear camber reads -30 or half a degree then the front needs to be around -1 degree 30'. Working from that platform you have options.... Remove -30' front camber she will push corner-in, add -30' she will oversteer corner-out. It's all fictitious until we know where the rear camber stands but the general law of a degree disparity normally works across the marques..... Please do not set the chassis to stock settings..... The chassis is not stock so the settings no longer apply. Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 4, 2014 Author Report Share Posted January 4, 2014 So theoretically, if the rear camber is circa -1 40', so to push corner out, the front would need -2 70' to push corner in -2 10'. Middle ground being -2 40'. Seems an a lot of neg on the front. These settings say the rear is spot on range, the front looks like it's looking for -45'. But that's standard range, which this isn't. Would it be feasible to run as matching camber front & rear? Quote Link to comment Share on other sites More sharing options...
Tony Posted January 5, 2014 Report Share Posted January 5, 2014 The rear won't be sitting with a camber that low...... Thing is to much camber is a bad thing, it actually reduces the tyres contact patch. Cambers force is compressive at the front and on your car because of the beam it's something of a spectator at the rear. Ideally the front camber should work within the radii of the front lower arm and steering arm during the suspensions bump/ droop transitions. This way the tyres contact patch is maintained, thus grip. Manipulating how much grip the tyres have front/ rear or as it's known "saturation coefficient" handling traits like under/ over-steer can be dialled in or out. For example the cars we have in BDC ( British Drift Championships ) only run -3 degrees front camber and normally 0 to -30' rear camber depending on the driver. Exactly how much front camber would depend on where the rear sits. I would think it's around -45' to -1 degree after lowering. In this event a front position of -1 degree 50' would work fine but saying that the camber gain on bump ( suspension ) compression would need to be found. Remember there is little to no camber gain on the rear with a beam. Another consideration is the front castor position? It's not directly adjustable on your car but it's position will change if you change the rake of the sprung chassis. Reads a bit odd i know but the castor trial moves through two pivotal points and in your case it's the upper ( sprung ) suspension turret and the lower ( unsprung ) lower swivel/ ball joint. If you change the rake then you also change the angle of the pick-up points. So what! You might think..... Well if the rake is reduced the castor position will extend and the opposite would be said if you increase the rake. Well your probably still in the realm of "so what?". The castor angle has many duties the main one being directional stability and steering weight. If the angle is reduced the steering will feel twitchy and light. Example, if you drive a car in reverse there's zero castor assistance and we all know how that feels.In opposite to much castor would make the steering heavy and over reactive return. Problem is the rake, camber, castor, gain on bump/ drop all correlates to a finite point?...... Ok this is where things get messy. The actual front camber position/ bias to the rear. The actual castor position generated by the rake and the saturation coefficient all have to work as a team when you turn! Now your thinking... What now?.... Well lets assume the rake is level and you have a rear camber at around -45'. The front camber is set to -1 degree 40' and the castor is at mid tolerance, let's say +4 degrees for a power rack. In this event we could assume the lower wish-bone and steering arms are horizontal, not perpendicular!! If so then the yaw would accelerate the Ackerman angle...... So still on the "what now front" what's this Ackerman jobbie?... It's front camber migration? Working as a team the camber, castor, toe and Ackerman work to extenuate the lock and camber migration on both the inner and outer front wheels. Example: On a left turn the inner wheel is at +21 degrees lock the outer -20 degrees lock. The NSF camber has migrated from -1 degree 40' to -40'. The outer wheel has migrated from -1 degree 40' to -2 degrees 30' or there about. The reason for this is each wheel front and rear takes a difference radius during a turn but on the modified car the harmony between the angles needs to be respected.... Welcome to wim 3 Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 5, 2014 Author Report Share Posted January 5, 2014 Everyday a school day. I'll play with some settings and see how we go. As the rear is fixed I'll get that double checked and work from there. A lot to tweak, but not much to adjust so will have to have a play. The compression gain is an interesting factor. Quote Link to comment Share on other sites More sharing options...
Tony Posted January 6, 2014 Report Share Posted January 6, 2014 On the modified car actual settings are born on the fly? It's not until we know where the non-adjustable rear camber sits then we could establish the rest of the settings. I have theorised the front camber positions but it's simply that for the moment. Historically lowering coils run a much higher rate than OEM coils, so it can be assumed camber gains on bump will be low, nevertheless they need to be witnessed to conclude any static settings. Changing the suspension/ centre of gravity/ roll centre does conclude with geometric chassis calibration but there's no law set in stone to where the calibration goes. As said DO NOT set the chassis to OEM positions, if you do then your de-tuning the modifications plus the handling would be pants. If you can please post the current rear camber positions. Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 6, 2014 Author Report Share Posted January 6, 2014 My rear settings are(from a Hunter Hawkeye); Camber -1 38' on the left, and -1 43' on the right. Toe 18' on the left, and 20' on the right Current front settings are; Camber -50' on the left, and -1 45' on the right. Caster 3 50' on the left, and 3 57' on the right Toe 0 both left and right. I have installed camber bolts now on the front, as the fronts can't be adjusted without, so back to get a re-set on sat/sun, but wanted to make sure they were working to the best settings they had. I was thinking that a -1/-1 20' on the front would be a good compromise, but maybe not. Quote Link to comment Share on other sites More sharing options...
Tony Posted January 7, 2014 Report Share Posted January 7, 2014 Looking at the rear camber i would set the front to -1 degree 30'. Any deeper will take out the tyres and bearings. I am surprised at the rear camber though. Quote Link to comment Share on other sites More sharing options...
Tony Posted January 7, 2014 Report Share Posted January 7, 2014 Oh i forgot to say don't put any ballast in the car like the data will ask for. Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 7, 2014 Author Report Share Posted January 7, 2014 I'll make sure when it's rechecked the rears are properly attached etc, before committing the settings. Think i've got to do an inner CV gaiter first. Yay. Quote Link to comment Share on other sites More sharing options...
Tony Posted January 8, 2014 Report Share Posted January 8, 2014 Horrible things to fit! Quote Link to comment Share on other sites More sharing options...
nobbie Posted January 18, 2014 Author Report Share Posted January 18, 2014 These are the settings we've gone for, on a Mk4 Astra Gsi, Spax Adj Gas Dampers, and Eibach Sportline Kit, Lowered -45-50mm Front, and -35mm Rear. Left Front Right Front Camber -1 15' -1 13' Caster 3 45' 3 48' Toe 0 0 Left Rear Right Rear Camber -1 37' -1 37' Toe 20' 15' Fingers crossed, and we'll see how we go. Thanks again Tony. Quote Link to comment Share on other sites More sharing options...
Tony Posted January 19, 2014 Report Share Posted January 19, 2014 The numbers are good, nice work. Quote Link to comment Share on other sites More sharing options...
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