sereneseven

just because a shock allows x amount of shock travel doesn't mean you would want to use all of it, and if your seting up your adj. coilovers for track use (the only reason you would IMO) the bumprubber gap and amount of droop should be one of your first concerns especially if your running compromised spring rates (too soft) since the car is being driven on the street also. In fact most "coil overs that i have seen have far to much travel to be usefull on a track so you have two options to bring them into a more desireable range. preload the springs enough to bring the droop into a managable range and then use packers under the bump rubber to get the air gap back or use another form of mechanical droop limiter (straps or chains for the old schooler).

Black91n/a

But you're assuming that having more than a bare minimum amount of droop is bad. Why do you think that's the case. A suspension with more droop will keep wheels on the pavement in more situations than one with limited droop. Artificially restricting droop can cause you to lift a tire during a turn, which make it useless, which is bad. If the tire isn't in contact with the ground it's not adding to the cornering forces and you'll be slower.

The only reason I can see for placing spacers under the bump stop is if it's got insufficient compressed length to prevent the shock from bottoming. Most droop limiters are to prevent damage to the shock from side loadings when the shock's nearly fully extended, as the force couple is acting on a much shorter distance, so to resist an equivalent moment, the forces are higher.

GoRacer

iTrader: (2)

Ack, a couple of you guys have me lost. Are you two refering to old skool M2 Koni/GC style setup when you talk about bump stops and Droopy rubbing tires at the Gap? ...cause I never included those.

Black91na - Would love to see pictures and a write up, so I understand what you are saying and i'm sure there are others that would like to as well.

Looks like Rynberg understood my intention of the thread but i'm not really shure if everyone else did?

I realize that the old skool Koni/GC setup is considered a coilover but I wasn't using them or including them in the thread. Today you can buy a set of coilovers for as little as $850 (+tax&ship) which is about the same price as Tokico+eibach, Gab+H&R or Koni+GC and they are hight/preload independant as well as including pillow ball mounts. Please mention which setup you are refering to in the replies.

I would also like to know when you guys preload are you compensating for springs that are too long or too soft? I'm not shure if you can choose spring length or rate on the old skool setups other then different brands.

My current Buddyclubs have a short stroke damper and 10kg/10kg (225mm length) springs. My old JIC SF1's had 10kg/8kg (now they are 10kg/7kg) but unshure of the length did not have independant hight/preload adjustemt. You would actually raise/lower the springs which took away damper travel and if you raised the cars hight instead of lowering it then you simultaniously compressed the springs cause unwanted preload. Don't you want to adjust preload seperately and acurately? If the coilovers have helper springs then you can squish the helpers negating any help they would have provided. I was going to replace the springs on my old SF1's with (shorter 6") 8kg/6kg but it was too much money and I got a deal on the Buddy's, so I swapped them instead.

sereneseven

Well I tell you I have had many discussions on this with a lot of very smart people and between all of us to be honest we have yet be able to come up with a complete explaination for it but i'll give it a shot....by running limited droop or zero (mainly in the front) you are forcing more total weight to transfer to the loaded corner and the grip level that can be gained by the loaded tire will achually out way the potential loss from the unloaded tire. I will also say that all of our testing has always been done on full race slicks...with that said this method my not work on a treaded tire as well... at the same time with this type of set-up suspension travel can hurt you because if you allow to much compliance on the primarily loaded corner the vehicle it will not spread the weight to opposite end as well.


the bump rubber is alot more of a tunning aid then you are understanding....in fact i would bet that 90% of the cars here that hit the track are riding around on them alot mor than people realize...most people think of the bump rubber as a safety net to protect the car which is what most are designed for on a street car however as soon as you put slicks on and try to race you should realize that thats what your riding around on when you really start loading up the car. and if you get them gapped right they can help a cars predictability a ton because they can help deaden things like snap oversteer and momentum slides.

Black91n/a

I also hang out on the Miata.net forum, so I'm well aware of using bump stops as a handling tool, but especially when really low on race tires, I'd be more worried about preventing rubbing and other potential damages (control arms hitting the frame is a super low Miata issue too) than with setting it up perfectly for bumpstop height for a handling tool. Using longer, progressive bumpstops would be a better option there IMHO, as you're not really sacrificing much/any travel. Ground Control sells a couple different varieties.

That's very counter intuitive about increasing grip that way, I never would have thought that that's the case, since that's not how rubber usually reacts, as usually lower pressures equal more grip, unless there's an increase in area that is associated with the load transfer that more than offsets that effect. But doesn't it also cause problems at turn exit when the unloaded tire suddenly becomes loaded? Because to do what you're describing it'd have to be very heavily pre-loaded, so the impact of the tire becoming loaded again would be rather harsh and abrupt, as there's little to no travel in which this happens. I'd think that that could really uspet the car in certain situations, like when curb jumping.

There's a decent explanation of what I'm talking about as to how to set it up here:
http://www.sportcompactcarweb.com/pr...ilvia_part_iv/

Dave Colman is a pretty sharp guy, and he's currently employed by Mazdaspeed NA, so I'd think he knows what he's talking about.

sereneseven

yes there are a ton of different bump rubbers around in differing sizes and spring rates and yes to get them set right takes a lot work but when you get it right its worth it even on a non aero car.

like I have said I am not the best at explaining how droop limiting works but let me try again

to simplify the situation let make two tires LF/RF going in a straight line the LF is loaded with 100lbs as well as the RF 100lbs now you enter a RH corner with droop in the car and lets say 25 percent of the weight is tranfered to the LF so now the LF is 125 and RF is 75...in the same situation with say zero droop the car will transfer 50 percent of its weight giving the LF 150 RF 50, the extra weight on the left front has now lets say doubled its grip while the RH has only lost say 25 percent so your total grip is 25 percent higher. it has to to with tire hysteresis.........and yes this is very incomplete explaination...sorry but it would take would take a few pages to fully explain.

as for backing this info up.... droop limiting has been around for a long time and is still winning championships I can tell you that damn near every dp, p1,p2, gt1,gt2, promazda....car that has one a championship in the last few years have worked very hard on the droops. ond over the those last few years I been imployed by more than one top five team and have spend to many hrs. working on the cars with this kind of set-up to remember, I will also say the close to %30 of the testing I have done in the last year has been dedicated to droop and bump rubbers.

as for the auther of the this thread...sorry this has gotten totally off track mine purpose for posting in here was to express that your method of set-up ignored the piston placement in the shock and didn't seem that you were fully understanding why there are two ways to adjust the RH.

GoRacer

iTrader: (2)

^ I just mistated the title, so it's getting confusing but I don't mind the replies they are welcomed as they will help other with race setups and old skool type coilovers.

Let me just restate the purpose I had in mind was to properly adjust ride hight with new coilovers being installed. Raising hight by the srpings also changes preload but raising from the perch does not. The damper hight can be adjusted by your self in the garage with hand tools. So hopefully with these tips it will save people time and they will be very close to a proper corner balance for free.

I forgot to post all the pictures and forgot the front setup. Since the fronts are longer the total span for top of perch to top of springs is 12" to acheive a 26" floor to fender lip stance. I also did not take in to account spring sag which is 1/4". Maybe this is the droop sagy sag you guys are refering to. Should I include the 1/4" sag in to preload?

Black91n/a

Well you've obviously got me far outgunned with credentials, I'm still learning. It's not that I doubt you, it's just not something that I would have come up with on my own.

For a dual purpose car that sees road use and track use, what would you do? I'd think that the extra droop travel would be good for all those situations that just don't arise on track. Especially since the droop limiting is only for a slight increase in grip, and for a dual use car that's not really that much of a concern, since there's not really anything at stake when it comes to getting the last few % out of the car.

sereneseven

well to be honest I wouldn't work to hard on droops and bump rubbers because your really not competing for anything more than a good time and bragging rights and the amount of work required is phenomanal compared to the gains to be had....but droop and bump are things that should be at least monitored and kept track of so you can at least justify that changes you do make to the car are really what you think they are. I.E. say you just spin the S.P. up untill it touches the spring and then you decide to put 100lbs stiffer spring in and you put the S.P. at contact again, well now you have increased the bump rubber gab and decreased the droop which if you've been riding around on the bump rubber when loaded this change can achually feel like you softened the spring rate. when you first set-up you should measure the amount of shock travel till bump rubber at RH and make sure that your even side to side and keep those #s so if you decide to change spring rate you can adj. the spring perch back to the same hight and thusly make only a spring change and not a spring change and a droop change and a bump rubber gap change.

obviously on a street car you will want droop in the car so you don't end up paralized which means you will have to compromise...but its something to think about at the track if you want to try some stuff just keep track of the piston position relative to the body so can get back to where you started and play around with both droop and bump rubber gap. you can make little slotted rings of delrin that just snap on the shock shaft for spacer(packers would be what they're called) you would be amazed how much of an difference it can make and considering your going to be running on softer springs than ideal do to the multi purpose car the bump rubber can be your best friend for speeding up the cars set point which can help with predictability a ton.

obviouslly if you have coilovers which only have the S.P. as RH adj. its a little more complecated because you would have to fab mechanical droop limiters in order to achieve the adjustability which is a very complicated endevere so I would'nt even worry about it. but do to springs being all over the place as far as they're repeatability, you should still measure the bump rubber air gap and if its off side to side make some packers to even it up.