julians Posted June 19, 2002 Share Posted June 19, 2002 A bit long this one, but just looking for a few considered opinions. Can anyone give me a ballpark figure for a nice track oriented ride height setting. Not too bothered about absolute values more concerned the the difference between front and rear, just need something to start with so I can optimise it later on. The build manual reckons it should be around 15mm higher at the back, but it doesent mention whether this is optimum for a K car or a crossflow or a VX, or whether this is a road biased setting or not. BTW, my car is zetec engined (which I guess makes it most like a crossflow in terms of weight distribution), with 260lb front springs (narrow track), and 215lb rears. At the moment the rear is around 2.5-3cm higher than the front (because I cant make the rear platforms any lower without the springs going slack at full droop), and I'm experiencing a fair bit of understeer on the track. Toe is set to 25minutes out, camber is set at around 1degree -ve. Front arb is 5/8th, rear is set on second from softest setting. The car seems to initially point into the turn quite sharply, but soon washes wide. Its strange really because the understeer appear to get less the harder you push the car. I was considering trying softer front springs, but thought I'd check out the ride height options first. I know that raising the rear is generally supposed to induce oversteer, but is there a point when there is too much weight on the front and understeer starts to become more prevalent again. Cheers for reading. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 20, 2002 Share Posted June 20, 2002 Your rear spring rate is way higher than I would recommend. What diff do you have? Any rear steer effects you have are going to be minimised because you have the car so stiff. Finding a balanced way to soften up the car will give you a much more manageable drive on track. It is a mistake to presume that track suspension settings need to be *hard*. If the suspension doesn't move, it isn't doing anything. Peterid=teal> 253 BHP K-seriesteeth.gif, no gearboxbum.gifid=red> Link to comment Share on other sites More sharing options...
Chelspeed Posted June 20, 2002 Share Posted June 20, 2002 Avoiding the springs going slack might be the way to go in an ideal world but if they do it's not catastrophic. I would think a ride height thats 30mm too high at the rear will cause far more bad things to happen than the springs going slack once in a blue moon over a humpy back bridge. Link to comment Share on other sites More sharing options...
julians Posted June 20, 2002 Author Share Posted June 20, 2002 I'm using a 3.92 LSD from a sierra (cosworth is it?) , I had considered that it may not have been modified for the correct preload (which I presume is what you're getting at), but I dont know as i didnt build the car. Is there an easy way to check whether its been adjusted for a seven or not. The rear spring rates were recommended to me by caterham, apparently the superlight racers use them to fairly good effect. They dont feel too stiff, ride quality is not a problem for me. I recently changed to these from the standard progressive springs in an attempt to cure the understeer, doesent seem to have made much difference though. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 20, 2002 Share Posted June 20, 2002 The only racers who use those springs are the Supergrads and they don't get a choice. Caterham have given you a bum steer. There are far more optimal solutions. The diff is going to cause some understeering problems and has almost certainly not been modified. Peterid=teal> 253 BHP K-seriesteeth.gif, no gearboxbum.gifid=red> Link to comment Share on other sites More sharing options...
julians Posted June 20, 2002 Author Share Posted June 20, 2002 I presume altering the diff is not a job for anyone other than a diff/gearbox expert. I think I'll wait till it breaks or until I have to remove the diff anyway before I get it looked at. What spring rates would you suggest for the rear? I was under the impression that stiffening up the rear would increase oversteer, wheras softening it will increase rear end grip and hence more understeer. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted June 20, 2002 Share Posted June 20, 2002 If everything is so stiff that the car doesn't roll and the rear steer doesn't work, then you have stopped the chassis from working on your behalf. The stiffness is only one fo the factors you need to consider. Just had a conversation with Phil Stewart who does the diff rebuilds... ... and he runs 215lb/in rear springs. ... and also reckons the diff preload and ramps will sort you out. Those diffs don't break - probably the single most reliable component on the car, so prepare for a long wait. Peterid=teal> 253 BHP K-seriesteeth.gif, no gearboxbum.gifid=red> Link to comment Share on other sites More sharing options...
julians Posted June 20, 2002 Author Share Posted June 20, 2002 Cheers Peter, probably a job for over winter then. Link to comment Share on other sites More sharing options...
captain chaos Posted June 21, 2002 Share Posted June 21, 2002 Peter, Are you saying that Phil S runs 215lb rears on his Vx? I tried 185's on my Vx and my teeth nearly rattled out! Link to comment Share on other sites More sharing options...
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