STACK vs BUMP !!!!!

[Dirtwizard]

Which one is better ? in what conditions ?
Bump seems really touchy

[F22 RAPTOR]

"Stacks"(2-Step Spring) will handle bumps better and isn't as harsh on the chassis and suspension components. Bumps and coil binding in my view are junk engineering and dangerous, especially on an unpredictable changing surface like dirt. JMO

[big88fan]

I wouldn't go as far as saying coil bind is junk but it is not what you want to run on a rough track if its smooth and slick its hard to beat but just a few ruts can make it extremely hard to drive and it is very hard on the lowers and shocks

[modfan83]

Coil bind is absolutly not what you want to do on dirt. Coil bind takes everything out of the suspension and makes the tires contol everything. The dual spring setup is the way to go with the rf. Just make sure you think about the rest of the car when runnning the dual stage spring!!!!! Bumpstops work great on super smooth slick tracks but are hard to dial in esp. when any type of ruts are present.

[F22 RAPTOR]

Save your teeth, save wear and tear on your car and either go, "Stacked"(2-Step Spring) or "conventional", but "coil binding" is about as crude a setup as can be conceived of, short of welding the suspension in place or utilizing some low rider hydraulics. You can make just about anything be fast under the right conditions, but that doesn't make it the best thing to do or safe. More than likely if you went "Coil Bind" you'd eventually have something fail in the RF and risk injury or destroying your car or both, NOT worth the risk hoping for that just the right condition. Cars have suspension and utilizing it properly has been proven over and over again to trump a wagon, most any day.

[Dirtwizard]

It wasnt that long ago when alot of guys that were fast only needed 3 wheels.
Ive seen a bunch of races where the left rear never sits down .
Weight will transfer whether the suspension moves or not

[MasterSbilt_Racer]

It wasnt that long ago when alot of guys that were fast only needed 3 wheels.
Ive seen a bunch of races where the left rear never sits down .
Weight will transfer whether the suspension moves or not

No one is disputing that. The problem is that you need give in the suspension and the approriate amount of damping to handle even small irregularities in the surface. The tires do not have the appropriate properties.

[poppy]

Stacked spring setup with the lock out is the only way to go. Started running it last year and wow, I liked it a lot. Real easy to keep that right front pinned down but still on a spring.

[sj valley dave]

Familiar with a coil bind set up and a bump stop set up, but how does a stacked RF set up work.....??

[joedoozer]

Familiar with a coil bind set up and a bump stop set up, but how does a stacked RF set up work.....??

I am not sure myself. But I would assume it to be a soft spring on top of a stiffer one. The soft spring enough to support the car on level ground and down the straight. And then in the corner when weight shifts to the RF, it collapses under the load. Eventually binding and then pushing on the stiffer bottom spring. Allowing it to stay pinned over on the RF. I wonder would this be a decent idea for someone not running a easy-up shock on the LR or a pin-down shock on the RF? To help with LR hike, and weight transfer.

[lovindirt66x]

So how does one setup a RF bump stop, and when and where to run one with what shock and spring?

[Matt49]

There seems to be a lot of confusion about all of this and some of it is terminology.

Running on a bump stop does NOT imply that you are trying to achieve coil bind. The idea is to hit the bump stop (between the shock body and the lower spring seat) BEFORE the coil-over binds. The problem still remains that this can be very sudden and unpredictable, especially in anything less than perfect conditions (very smooth track). And if you are actually getting coil bind before the bump stop, you could be in real trouble.

A stack spring setup is just that: two springs stacked on top of one another to achieve a different spring rate without suffering from spring bowing. One would probably never want to "stack" two springs with the intent of causing one of them to coil bind as it would be unpredictable as the WHEN it would happen.

Dual-stage coil-over (which I think is what everyone is trying to explain) is totally different. It's hard to explain without a drawing but picture your shock standing upright with your shaft facing down as if it was installed on the car. At the bottom (sitting on the spring cup) you would have your "primary" spring which might be a 10" 700# spring. Then above that you would have a slider. Above that would be your "secondary" spring which might be a 4" 700# spring. Obviously, this would put the slider on the body of the shock. Just above the slider, you would have a jam-nut that threads on the shock body and is somewhere between the slider and your actual adjuster nut at the top of your secondary spring. It is completely inside the secondary spring so that spring can compress around this jam-nut.
As both springs compress, they compress with a rate (in this example) of 254#. Until the slider hits the jam nut and then you are on a 700# spring only because the secondary spring can't compress anymore. But you did NOT coil bind it, you just stopped it with the slider hitting the jam-nut.
You can adjust how far the jam-nut is from the slider to change the timing/travel of when the spring rate for that corner changes.
This setup allows a softer RF spring for corner entry on slick tracks which keeps the car from getting too free on entry. But then once the RF is pinned on the stiffer spring it provides tighter corner exit.
At least that's the idea.

[F22 RAPTOR]

It wasnt that long ago when alot of guys that were fast only needed 3 wheels.
Ive seen a bunch of races where the left rear never sits down .
Weight will transfer whether the suspension moves or not
Sometimes things aren't as fast as they seem, just a dramatic display of brute HP.


I am not sure myself. But I would assume it to be a soft spring on top of a stiffer one. The soft spring enough to support the car on level ground and down the straight. And then in the corner when weight shifts to the RF, it collapses under the load. Eventually binding and then pushing on the stiffer bottom spring. Allowing it to stay pinned over on the RF. I wonder would this be a decent idea for someone not running a easy-up shock on the LR or a pin-down shock on the RF? To help with LR hike, and weight transfer.

Almost. With "Stacked"(2-Step Spring) you do have a lighter spring combined with a heavier spring which gives you a lighter combined rate than either spring alone. However, you should never have the lighter spring actually "coil bind", you should use a jam nut that stops the travel of the of the lighter spring allowing the heavier spring to engage and support the weight when you throttle up and climb the bars. Coil binding is bad for springs and bad for suspension parts, bad for the chassis and not real great for the driver. Having the suspension ever go solid in compression is bad news, sure there is an instantaniuos spike in traction at that wheel, but it is quickly lost without some sort of dampening and a spring to absorb the energy and inconsistantcies in the racing surface. I'm no fan of on the hook setups, but if your gonna do it, do it right and do it as safe as you can.

[poppy]

F22 you are correct, I run a 700 on the bottom and a 400 on top, so you have a very soft spring rate on the RF until you hit the jam nut which is before coil bind, then you are only on the 700 spring. One of the advantages is that it is really easy to keep the RF pinned a around the track. It pretty much just falls down until the jam nut comes into play. We have also found that we hardly ever play with bite, I adj the jam nut as track conditions change. Cannot imagine every going back to a single spring.

[cushionbumper]

@poppy, can you expand on as the track changes how you would adjust the jam nut?
Thanks, CB

[Dirtwizard]

There is some confusion here Bump,Stack,Coilbind are 3 totally different setups.
Not counting the lock-in, lock-out deal

[MasterSbilt_Racer]

There is some confusion here Bump,Stack,Coilbind are 3 totally different setups.
Not counting the lock-in, lock-out deal

If you are ignoring the two-step hardware on a stacked spring, it is really just a soft spring. No sense categorizing it any differently.

[moonshine]

I unload and stay on my bump stop unless the track gets real rough. We don't run the typical bump stop that most people are on, that looks like an accordion. We run asphalt style bumps stacked on top of each other with 2 different rates. It's not harsh at all. The spring we run is just strong enough to get the car from the hauler to the track. If it gets real rough then we'll go to the 2 stage, but to me it's a little tricker than the bump. I know alot of people think they are crutches but I love the way the car turns in with them.

[poppy]

if you have 1 1/2 mesurment from the jam nut to the slider by making that a 1/4 of a inch longer/more 1 3/4 gives you more soft spring, which you would want on dry slick like wise making it 1 1/4 would work well on tacky where you do not need to pin the RF as hard.

[F22 RAPTOR]

If you are ignoring the two-step hardware on a stacked spring, it is really just a soft spring. No sense categorizing it any differently.
Exactly true. Stacked and 2-Step Spring are two different animals. I forget to say it sometimes because thats the only way I see, "Stacked" is 2-Step Spring. I'm definitely in the camp that thinks "bumps" and "coil binding" are crutch's and junk engineering, although coil bind is the absolute worst, no offense intended. I guess in a few years will be discussing whether "welded" or "bolted" in place are the way to go... At least bumps are tiny little rubber springs...

[MasterSbilt_Racer]

Exactly true. Stacked and two step are two different animals. I'm definitely in the camp that thinks "bumps" and "coil binding" are crutch's and junk engineering, although coil bind is the absolute worst, no offense intended. I guess in a few years will be discussing whether "welded" or "bolted" in place are the way to go... At least bumps are tiny little rubber springs...

A coil-bound spring just has too much "give". You really need a high-modulus, high yield material for your stops. I recommed a nickel-based superalloy like Inconel 718. ;)

[PayinDaPurse]

Poppy your inbox is full :p

[Moreland24]

if you have 1 1/2 mesurment from the jam nut to the slider by making that a 1/4 of a inch longer/more 1 3/4 gives you more soft spring, which you would want on dry slick like wise making it 1 1/4 would work well on tacky where you do not need to pin the RF as hard.

So basically when you lower the jam nut to allow the car to roll more when the track slows down, (and assuming since your not worried about the wedge when making this adjustment), you are more focused on this allowing the car to put more weight on the RR to tighten the car (mainly entry and mid corner).

[poppy]

That is correct, and I figured out how to empty my inbox. It is way easer to show someone with all the pieces than to explain it. i also think that the spring package I run in the rear. I like a real soft stacked spring set up in the rear. Along with pinning the front you need to get the weight there in a hurry also.

[MasterSbilt_Racer]

So basically when you lower the jam nut to allow the car to roll more when the track slows down, (and assuming since your not worried about the wedge when making this adjustment), you are more focused on this allowing the car to put more weight on the RR to tighten the car (mainly entry and mid corner).

The wedge won't change when you move the nut he is talking about.

[Moreland24]

Right, not static wedge. Just dynamic wedge, right?

[MasterSbilt_Racer]

Right, not static wedge. Just dynamic wedge, right?

Yes and no. You get on the heavy spring at a different point so somewhere between ride height and fully down on the rf there will be some difference. When the car is on the rf, it should basically be the same.

If total travel is the same, dynamic wedge will be the same at that point.

[cushionbumper]

@poppy, check you pm.
Thanks, CB

[29racin]

so i read the whole thread and now am really confused..... stacked and dual stage ARE 2 different things. stacked with a slider does what? (just gives a really soft rate) correct. Dual stage with a jam nut does what? ( qiuck weight transfer and hold down)correct? What are the best rate for the dual stage set-up and do i want for a gap to the jam nut? If I am incorrect please ellaborate for me... thank for the input.. I run 3/8 dirt. DRY.

[F22 RAPTOR]

so i read the whole thread and now am really confused..... stacked and dual stage ARE 2 different things. stacked with a slider does what? (just gives a really soft rate) correct. Dual stage with a jam nut does what? ( qiuck weight transfer and hold down)correct? What are the best rate for the dual stage set-up and do i want for a gap to the jam nut? If I am incorrect please ellaborate for me... thank for the input.. I run 3/8 dirt. DRY.

Stacked = 2 springs stacked one on top of the other with a slider gives you softer combined rate.

2 Step Spring = Same as "Stacked" only you have a jam nut that halts the travel of the slider at a set point of travel and thus changes from combined softer rate to what ever heavy rate spring you are running in the stack.

So running the 2 Step Spring lets you have your body roll on the RF of a light weight spring, which gives you less dynamic cross and increased side bite. However when you throttle up and push over on the RF harder the heavy spring engages and gives you more dynamic cross/bite to drive off corner. Can be best of both worlds if you hit it right, in theory. :cool:

We use to use the 2 Step Spring setup, back in the days before the hook setups, to help lift the frontend under accel to transfer the weight better to the rear. Now its used to pin the RF instead of just having it lay over and collapse, which gives good side bite on entry, but lacks dynamic cross to accel off. Good luck.

[Dirtwizard]

Yes , and thats the million dollar question

[Moreland24]

Yes and no. You get on the heavy spring at a different point so somewhere between ride height and fully down on the rf there will be some difference. When the car is on the rf, it should basically be the same.

If total travel is the same, dynamic wedge will be the same at that point.

Ahhhh, ok I see...

[29racin]

what i s recommended spring rates to use on 2 stage set-up. now i use a 400 or 375. this will also help on throttle corner entry?

[cushionbumper]

@poppy, check you PM
CB

[cushionbumper]

poppy, check your pm.

[throwindirt1]

we currently run a 375 on rf and would like to try the stacked spring setup, what springs would we need to replace the 375?

[big88fan]

Well for those who have always said the bump stop setup doesn't work I now have to totally disagree with you my car handled the best it ever has and on a tacky rough and super slick track it was awesome so those of you still searching for an advantage keep looking.

[fastford]

you tell them big88, ive said 0n here bef0re th0se bad m0uthing the bump st0p d0nt kn0w h0w t0 use it

[F22 RAPTOR]

I never said the bump couldn't or didn't work, but I did say it was unnecessarily harsh and can be difficult to get right. It also breaks a lot of stuff and can result in a roll over and totaling the car, but hey if you guys like it and don't mind getting on your lid, have at it. It is slightly better than coil binding, which is stupid. A bump, at least, is just a small rubber spring. To each his own.

[01racing]

do you need to run alot of rebound with the stack ?

[MasterSbilt_Racer]

do you need to run alot of rebound with the stack ?

Yes you do.

[big88fan]

I don't see how it can break stuff at least with the bump stop we run they are over 4" long. Running alot of rebound seems like a bad idea unless the track was as smooth as glass everytime you go over a bump it would keep the tire from making full contact with the track.

[F22 RAPTOR]

I don't see how it can break stuff at least with the bump stop we run they are over 4" long. Running alot of rebound seems like a bad idea unless the track was as smooth as glass everytime you go over a bump it would keep the tire from making full contact with the track.

Thats my point, to make it really go, it needs to be tied down and so you end up with not much travel. You find a hole or a rutt the wrong way and all that energy is driven into the chassis and suspension components. Look if you like it and it works for you thats great, but I have my opinion and you have yours, thats all. Bump is way better than coil bind, I'm just not a fan of either.

[fastford]

i use a bump stop that is 3in long, at a height of 1 1/4 in it has 1400 psi and can compress a little further however it never does, i cant see this being any harsher on equipment than a stacked setup useing the common 700 lb primary spring which means once it hits she spanner it would have to travel 2 inches to reach the 1400lb mark, as apposed to 1 3/4in on the bump, not really much difference. this is my personal assessment the bumpstop is the simplest way to try the lastest craze of the soft right front if your track is slick and smooth, this is when i prefer bump over the stacked, however on a rough and heavy track, i feel the stack has a slight edge in that it want disrupt the car as much but is a moderate amount harder to tune. as far as rt fr rebound on the bump, i start with 50psi gas in shock and 60 percent rebound if the car has a slight throttle push when i pick up the throttle, i start increasing rebound, if it has a bad push then theres a lot of options,decrease wedge,raise lower left bar, trail lf rear which idont like,and list goes on and on ,i hope this helps some

[MasterSbilt_Racer]

At what point does a bump stop become a rubber spring? ;)

[fastford]

At what point does a bump stop become a rubber spring? ;)

at the point when the shock body touches the slider on top of the bump stop, re suspension has all the data on there web site that shows the psi of there bump stops at different heights

[MasterSbilt_Racer]

at the point when the shock body touches the slider on top of the bump stop, re suspension has all the data on there web site that shows the psi of there bump stops at different heights

I was just being a smartazz. What dirt guys are now calling bumpstops, I would just call a spring. To me, a bumpstop stops the suspension travel. More or less, the height remains fairly constant no matter how much force is applied to it. That was what the original bumpstops used in various forms of motorsport were.

[F22 RAPTOR]

I was just being a smartazz. What dirt guys are now calling bumpstops, I would just call a spring. To me, a bumpstop stops the suspension travel. More or less, the height remains fairly constant no matter how much force is applied to it. That was what the original bumpstops used in various forms of motorsport were.

I was wondering what happened to you, LOL. I guess technically whats being run isn't a bump stop, but dang if I know what to call it except what you said, "a rubber spring". A true bump stop is something low riders drive around on, thats why you see them stuck on speed bumps.:cool:

[racin29]

yes they should be called suspension bushings that is what they are, anyways something else to keep in mind when running a suspension bushing like the one mentioned before, its 1400psi at 1 3/4 that divids out to a 800lbs spring but then you have to add your actual spring on top of that so say you have a 375 on the rf once you reach the suspension bushing your spring rate goes up to 1175, something to keep in mind for the ones wanting to try this out

[fastford]

theirs one more point i wanted to make about the bump stop setup, or rubber bushing spring or what ever you want to call it, it acts more like a progressive spring,the stacked setup is still linear after it hits the primary spring ,i think this is the stacked setups main advantage on a rough heavy track. both these setups are good once you understand them, but they are not for the beginner, here is an example, a guy at our local track that just moved up to limited late model this year and had been running top ten all year, decided to try the bump stop, his car would not turn left in a 40 acre field on throttle,he got lapped by the top 3 cars, who were all on bump stops, it scared him so bad he said he was taking it back off,he was to inexperienced to understand what was happening.