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]

Coil binding is a crutch, plain and simple.

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