could someone please give me a complete but reasonably simple explanation as to why this adjustment would be carried out ?. Pros/cons, is there a formula/method of working out how much?. Is it as simple as shortening the damper rods and turning a new thread on them ?. Any info appreciated thanks.
I can't see a good reason to adjust droop other than to stop springs dislocating etc. It doesn't affect load transfer and as long as body roll isn't extreme it has no bearing on the loading of the tyre. If the wheel is about to leave the ground it has zero load on it and is contributing nothing to lateral grip. Whether it's on the deck or in the air is irrelevant if there's no load on it.
When I swapped from KW Competition to AST I went with more droop on the rear, principally to try and keep the inside rear on the ground in corners. I can't give any science, but I definitely prefer it now to how it was previously and I'm holding more apex speed than before although that change was made at the same time as other changes so can't say how much, if any, was attributable to rear droop. I was advised at the time that it was worth getting it set right to try and keep the rears in contact.
Don't want to knock personal experiences,always good to have first hand feedback but the theory doesn't support it. The Lateral load a tyre can generate (grip) is proportional to vertical load, that's why aero works. No load = no grip It's kind of irrelevant anyway on a light car with stiff springs. think that If a mk2 is 1000kg then max rear corner weight is maybe 200kg. with 440lb/in springs rear will only settle 1 inch with the mass of the car on it. So anymore than 1" of droop is zero spring load, only the mass of wheel/tyre holding it down which is small. takes very little cornering/braking to unload that instead rear. And to have more than 1" you'd need to have helper springs to keep it all together. Again not saying the theory translates 100% but it's the last suspension setting I'd be thinking about,very little influence compared to geometry, spring rates,arbs etc.
Limiting droop on the rear of a VW Golf is done for a few reasons . The most important ( In my opinion ) is so when we run Toe out on the back axle which does help the car turn you get the weight off the inside wheel which will be pointing in the wrong direction , and let the outside wheel help the turn . It will also limit the amount of weight thrown to the front and should stop a lot of roll on to the front outside tyre . . Some people build their shocks with droop limiters in , some use simple cables . the best way is to convert the shock top mount to a Rose joint or rubber bush and fit an adjustable top mount ( U bracket held in place by long thick threaded rod through the body ) ( Hope I am making this clear a picture would save a thousand words ) Anyway you can adjust the car up or down ( and corner weight it in seconds with out playing with the shock and spring set up at all . This method also makes it quick and easy to raise the rear when it rains .
Don't want to knock physics facts,always good to have mathematical feedback but my bum dyno doesn't support it. My tiny brain works on the basis that a tyre not touching the ground can not have equal or more grip than a tyre touching the ground, even if it's a tiny amount, it's still more. I like a planted rear end so prefer the inside rear to stay on the ground where possible.
Rear droop is important for braking and off power entry into corners, front droop is for on power. Its also essential for managing traction over crests and driving over divots rather than bumps. It's a point where suspension travel ends and the cars weight takes effect, it is directly proportional to the springs and swaybars used and is governed by the amount of travel permitted in the lower arm. Unwinding coil overs wont create more droop as it's a sprung load required to push the arms downward. Shockerboy pointed out a way of controlling the droop, otherwise it's set to the maximum travel of the arms from the factory.
http://www.clubgti.com/showthread.php?230797-Golf-Mk2-TFSI-racer/page9 > Post 209 VWM rear topmount , its one way to adjust droop OR make the lenght of the damper adjustable , best with a RH/LH rod for ease of adjustment
That is the type of thing but it looks like it still uses a shock with a Pin on top , The problem there is that when you run the car low the axle line tends to move forward and backwards as the car hits bumps ( Rear axle arches forward as the mounts are 400 mm forward of the axle line ) , this will strain the top pin if the bearing inside isn't designed perfect and eventually the top pin breaks , If a shock with a top adjuster is used the pin is hollow and weaker , so be careful , If you use a U bracket and a shorter shock with a Bush or rose joint on top the shock can pivot freely at the joint and no stress on the shaft causing Stick ion ( Additional resistance from the shock due to lateral forces on the rod as it enters the body of the shock .) This is un measurable and affects damping forces
I can see several reasons to limit droop but I really don't see a good reason to artificially add droop. Using longer shocks etc. reduces bump travel which I think is more useful than droop. I always come back to the fact that once that corner has lifted more than the static "sag" then there's no load on it. If it feels better then the effect must come from some other mechanism. a stiff antiroll bar will limit droop also.
Maybe should have said, this is a production gti car so no uprated roll bars etc. the reason I asked the initial question was I've heard people in the series talk about rear droop but didn't know how it affected the handling, as my car is now I can raise it in the air and pull the shocker/axle down a good 6/8 inches before it reaches its stop, by which time the spring has left the top spring plate etc.
Ah sorry I misunderstood, in that case I'd say it would be a good idea to limit the droop to keep the spring on the pearch. Could do this with cables or similar but shorter shock would be better idea. Spring being loose could cause very dodgy handling if it doesn't relocate properly. Also must be very crashy?
^^^ Most cars ( also race cars) run with dampers who are to long...as a result you get lots of droop and often get rattle spings as they become unloaded, this can be countered by raising the upper pickup point or lower the lower pickup point ( altough this has it limitations) ( Idealy the spring get seated against the upper platform while damper/ wheel is unloaded) To explain it might be good to have a look at Formula cars and use some thinking and convert this to Touring cars. Dampers get fitted with either soft springs, who are preloaded ( as on roadcars ) or `` Train ``spings are fitted ( btw laptimes are often very similar with many different setups) When more preload is set, ride hight increases. but you want to keep ride hight as before, so now you shorten the Pushrods ( who link the lower wishbone at wheelside to the damper via a rocker) and now you are back at ride hight.... to do this on a normal road/ race car you need to shorten the damper or move the pickup points On a Touring car . something as 70 mm free damper stroke at the rear and ca 100 - 120 mm at the front should be more than sufficient for circuit / hill climb, etc and droop something as 2 3 cm > spring loaded by corner weight Formula cars have droop limiters both at front and rear
