I've had some drama with my front splitter, which failed again after i repaired it (see here https://radicalsportscarregistry.com/radicalforum/general-discussion/front-diffuser-wear-and-integrity/#post-8112). My 1 layer piece of small fibre lovingly laid across the crack failed after about 15 minutes of running and at speed the whole thing was skimming the ground again. The cracks are now larger either side and i've got a job to properly repair it, use mesh, sheet steel to strengthen etc..etc........
anyway back to the purpose of this post. Once i've repaired my front diffuser, What do i need to set to ensure that under no circumstances will it ever skim the floor again? I'm not fussed about performance, im' not racing it, i'm happy to go with factory settings and start from there.
- ride heights. I've read the manual and can see the drop height settings. It also says in section 6.1 (RSX manual) "the front pushrod is jigged from production at 230mm". What length are they measuring, is that from the centre of the rose joints on either end of the pushrod? Or from the tips, end to end? or something else?
- the factory Hankook sheet says i need to set the front drop height to 163mm either side, which = 77mm chassis height = 57mm calculated ride height at lowest point on chassis. Fine. How does one actually adjust the drop height, is it simply via the pushrod only on the front?
- Preload, do i set this first before ride heights?
- how do i set preload to 0? I think the procedure is: with car resting on its wheels, i unscrew the collar under the spring until its loose and the spring is free to rotate, then i tighten until there's no more gap and the spring can't be moved by hand - is that the point where preload is 0?
- does a preload setting of 4 = 4 full rotations from 0? (compressing spring)
- only after messing around with the front diffuser stays did i realise that this affects how the front bodywork aligns with the holes....if i only adjust the front stays then it messes up the alignment for the side fittings with the main bodywork. I'm guessing therefore i should adjust both front + rear stays in turn so the front diffuser from front to rear of it move up or down in heigh in unison, therefore there should be no issue with alignment to bodywork - correct?
my current thinking is - if i set my drop height to as per the hankook factory setup sheet, and i ensure my front diffuser heights all round are no lower than 40mm, then the bottom of my front diffuser should not be touching the ground at any point.........am i right?!
thanks
@rojid I will reply later with some more detail. What is important here is the order in which you undertake the set-up given you seem to be starting from scratch. It's important to get some things set before others as one has a big effect on the others.
What I wanted to point out was that @DavidF had replied to your other 'front diffuser' post with some details including... "I usually shoot for about 45mm (50mm is OK too) from the ground in front, and then whatever it takes to make a good fit with the nose sides so that it aligns in place without bending and without requiring pulling to fasten the zeus fitting. So maybe 55-60mm in the rear sides."
So in answer to your last dot point - follow DavidF's instructions above and you will be OK. The trick when setting the diffuser heights is to get the height under the front skid plate (right under the crash box 'nose') set up first, and then adjust the sides. You will definitely have to adjust both the front and rear stays during the procedure... and the correct setting is to make sure that the outside edges of the splitter are perfectly level when finished. As DavidF says in his earlier reply above, a good starting point is 45mm in the middle (under the skid plate) and then adjust the sides until the bodywork fits well (and I would add, while keeping the outside edge of the splitter level with the ground). DavidF is correct, when done this way on my car the outside edges end up about 10mm higher than in the middle at the front - so about 55mm on my car.
As mentioned though... none of the above splitter set-up can be done until you establish the correct chassis heights and rake... so setting the front splitter is normally the last step in the process.
after about 15 minutes of running and at speed the whole thing was skimming the ground again.
Is there a hole or crack in the front of the splitter? The problem could be that it is pressurized with air at high speeds, causing it to expand and then drag on the ground.
anyway back to the purpose of this post. Once i've repaired my front diffuser, What do i need to set to ensure that under no circumstances will it ever skim the floor again? I'm not fussed about performance, im' not racing it, i'm happy to go with factory settings and start from there.
Yes. The factory ride height and 40mm to 50mm clearance between the ground and the front of the splitter should prevent the it from dragging on the ground. Lowering the ride height overall would provide a racing advantage, but it is not easy to do. I achieved 2mm lower with my car using the desired rake setting (+18mm). To go lower, it would be necessary to reduce the length of the pushrods. For cars that have fixed rear pushrods, the ride height is even less adjustable.
- the factory Hankook sheet says i need to set the front drop height to 163mm either side, which = 77mm chassis height = 57mm calculated ride height at lowest point on chassis. Fine. How does one actually adjust the drop height, is it simply via the pushrod only on the front?
Yes. If you have fixed rear pushrods, then adjust the front pushrods to achieve the factory setup rake. 163mm is not criitical. If your rear is say 215mm, then set your front to 166mm to set the rake to +18mm (57mm + 18mm = 75mm. See table in owner's manual.)
- ride heights. I've read the manual and can see the drop height settings. It also says in section 6.1 (RSX manual) "the front pushrod is jigged from production at 230mm". What length are they measuring, is that from the centre of the rose joints on either end of the pushrod? Or from the tips, end to end? or something else?
The length of the pushrod is measured from the center of the rod end bushings. The way the manual and instructions are written seems to imply the 230mm is the desired length, but I don't think this is critical. The pushrods are intended to be adjusted independently, and so I never worry about making them equal or exactly 230mm. The desired rake setting determines the ultimate length of the pushrods.
- Preload, do i set this first before ride heights?
Yes. The exact order described in the owner's manual is correct. It is important that once the front preload is set, do not adjust the front perches again.
- how do i set preload to 0? I think the procedure is: with car resting on its wheels, i unscrew the collar under the spring until its loose and the spring is free to rotate, then i tighten until there's no more gap and the spring can't be moved by hand - is that the point where preload is 0?
Set the preload at full droop (car resting on chassis stands, not on the ground). If you were to set the preload when the car is sitting on its tires, then the springs would have negative preload which bad because at droop, there would be a gap between the damper springs and the coilover perch. The damper springs should maintain contact with the coilover perch throughout the full range of suspension travel.
0 preload means the perch just slightly snug against the damper springs and no more.
- does a preload setting of 4 = 4 full rotations from 0? (compressing spring)
Yes
my current thinking is - if i set my drop height to as per the hankook factory setup sheet, and i ensure my front diffuser heights all round are no lower than 40mm, then the bottom of my front diffuser should not be touching the ground at any point.........am i right?!
Not necessarily. It could be that your chassis geometry is set to factory specs, but that a body part drags on the ground for some other reason.
