Suspension Progressive Springs - Handling Characteristics?
#26
Originally Posted by meb
So, these are called Micro Cellular Progressive Jounce bumpers - I like the old name, but I guess different requires a different name. These, as you described, are progressive in nature.
The million dollar question, does the Mini incorporate these?
The million dollar question, does the Mini incorporate these?
Originally Posted by meb
Niether my Type-R or Civic Si had these bumpstops.
Originally Posted by meb
why does the writer of the article suggest cutting this style bumpstop? And if so, Would the top, or stiffest rate portion, be the portion to cut? Otherwise the transition from spring to bumpstop could be somewhat abrupt...
I have to admit I've retrofitted a lot of older cars with the cut-off bits from these nifty high-tech bumpstops, with excellent results--so I am very happy to have friends who lower cars professionally.
#27
Like you guys have been saying, the bump stops do give the suspension a progeressive rate. We are still tuning my Civic Si, but Koni makes a bump stop that might end up on the front of mine. We'll see after we get some data after next event. Race teams don't use progressive rate because they don't know how to for the most part. There are a few who aren't allowed to, like your NASCAR guys, who also aren't allowed to use any bump stops.
#28
BFG9000
The more I think about this subject, the more I wonder about how lucky I was; I simply threw the old bumpstops away. Every new kit - mostly Koni - came with new bumpstops.
Orthomini Jr
What model year is your Si?
The problem with these types of bumpstops, from a racing or street modification perspective is, when the springs are changed the relationship between the progressive bumpstops and the springs change - they were designed to work together. Race teams may simply discard these for this reason alone...their new set-ups are more than likely not compatible...one would think.
The more I think about this subject, the more I wonder about how lucky I was; I simply threw the old bumpstops away. Every new kit - mostly Koni - came with new bumpstops.
Orthomini Jr
What model year is your Si?
The problem with these types of bumpstops, from a racing or street modification perspective is, when the springs are changed the relationship between the progressive bumpstops and the springs change - they were designed to work together. Race teams may simply discard these for this reason alone...their new set-ups are more than likely not compatible...one would think.
#29
#30
Okay, call me dense. I still do not understand the intimate relationship between bumpstop, spring and damper. How does a bumpstop make a linear rate spring progressive when it really controls the damper's movement? I wrote in a previous post, progressive damping. I was quite literal with my choice of words.
I'm not disaggreeing with anything, I just, well...don't get it yet Perhaps there is something more subtle at work here.
Michael
I'm not disaggreeing with anything, I just, well...don't get it yet Perhaps there is something more subtle at work here.
Michael
#31
The spring rate of the spring itself did not change. If it was linear, then it's sill linear. However, the effective spring rate that is used by the car is from the combination of the spring and the bump stop. Therefore the effective spring rate is linear for the first portion of compression, then it becomes progresive when it contacts the bump stop.
#33
Originally Posted by meb
How does a bumpstop make a linear rate spring progressive when it really controls the damper's movement? I
Visualize what a spring does for a dampener. It controls the dampener's movement. A stiffer spring is "stronger" and will move that dampener much more strongly. A weaker spring does not move the dampener as strongly (notice I didn't say the word "quickly", but used the word "strongly"...BTW, is that even a word??).
Now visualize what a dampener does for a spring. Internal to the dampener is valving and some sort of medium that passes thru the valving: oil, inert gas, etc. Changing the dampening via valving or changing the medium will affect how quickly the spring can collapse and expand.
Now think for a moment how a car would handle if either the spring or dampener was removed from the car. With just springs the car would have a rideheight, but would be exteremly "bouncy" like a pogo stick, moving from extreme compression to extreme extension. With just dampeners, the car would fall to the ground collapsing the dampeners.
OK. So think a moment about the bumpstops. They're external to the dampener and they're not changing the valving or medium the valve moves thru. The bumpstops are exerting pressure onto the movement of the dampener just like springs exert pressure on the movement of the dampener. So bringing this together, the squishy bumpstop has the same effect as a quishy spring.
p.s. If this helps make more sense: the bumpstop doesn't make the overall spring rate progressive, better stated, it causes the overall spring rate to become dual-rate.
#34
matma92ser
I'm confused perhaps by the words being used...then it becomes progressive...by it you mean the damper?
dominicminicoopers
Yes, I'm beginning to understand. I'm very keen about matching spring and damping frequencies. But I've neglected in my thinking, the two-way relationship between spring and damper - thanks for isolating these, big help; a strong damper with a light spring rate will cause very sluggish responses. A light damper with a heavy spring rate will cause an unsettled condition - essentially one of your points; the frequencies of each must work with some degree of sympatico. I've only written the previous a half dozen times, employed it for twenty odd years...you would think I would remember.
So a spring of a given rate, presumably well matched to a proper damper, will yield different compression and rebound characterisitcs due to how the damper is allowed to move thru its compression and rebound stroke...characterized by the bumpstop. So, as always, a spring is controlled by a damper, whose movements (frequencies) are further refined by a progressive rate bumpstop.
I can see where this would make for a comfortable riding car; indeed, lighter spring and damping rates can be used with equal or greater control of a less civilized set up. But, a question still remains; these 'systems' are designed to work together...their frequencies are matched. As soon as one of these is changed - the spring comes to mind - the system is upset. I only throw this out there because this system is apparently delicate. Indiscriminate spring and or damping rates will affect more than ride. Hell, just changing the bumpstop will alter how this system works.
Originally Posted by matma92ser
The spring rate of the spring itself did not change. If it was linear, then it's sill linear. However, the effective spring rate that is used by the car is from the combination of the spring and the bump stop. Therefore the effective spring rate is linear for the first portion of compression, then it becomes progresive when it contacts the bump stop.
dominicminicoopers
Yes, I'm beginning to understand. I'm very keen about matching spring and damping frequencies. But I've neglected in my thinking, the two-way relationship between spring and damper - thanks for isolating these, big help; a strong damper with a light spring rate will cause very sluggish responses. A light damper with a heavy spring rate will cause an unsettled condition - essentially one of your points; the frequencies of each must work with some degree of sympatico. I've only written the previous a half dozen times, employed it for twenty odd years...you would think I would remember.
So a spring of a given rate, presumably well matched to a proper damper, will yield different compression and rebound characterisitcs due to how the damper is allowed to move thru its compression and rebound stroke...characterized by the bumpstop. So, as always, a spring is controlled by a damper, whose movements (frequencies) are further refined by a progressive rate bumpstop.
I can see where this would make for a comfortable riding car; indeed, lighter spring and damping rates can be used with equal or greater control of a less civilized set up. But, a question still remains; these 'systems' are designed to work together...their frequencies are matched. As soon as one of these is changed - the spring comes to mind - the system is upset. I only throw this out there because this system is apparently delicate. Indiscriminate spring and or damping rates will affect more than ride. Hell, just changing the bumpstop will alter how this system works.
#35
Originally Posted by meb
I can see where this would make for a comfortable riding car; indeed, lighter spring and damping rates can be used with equal or greater control of a less civilized set up. But, a question still remains; these 'systems' are designed to work together...their frequencies are matched. As soon as one of these is changed - the spring comes to mind - the system is upset. I only throw this out there because this system is apparently delicate. Indiscriminate spring and or damping rates will affect more than ride. Hell, just changing the bumpstop will alter how this system works.
p.s. I asked my dealership's techs about the bumpstops and the tech actually said the MINI doesn't need the front bumpstops whatsoever. The tech recommended even removing them. Wierd huh?
#36
The whole idea behind progressicve rate lowering springs is that they won't bottom out the suspension any earlier than stock springs would. Now if the shock is not able to handle the harmonics of that spring then thats a different story.
A normal, round bump stop will make the setup dual-rate. What shape is going to make a bumpstop progressive? There is a trick on weight transfer between the corners that I don't think I'm allowed to discuss unless someone is paying me to tell them. We (R&H) like to overshock cars most of the time, we also exclussivly use Bistein's in our setup's. In our experiance on shorttrack, asphalt or dirt, Bilstein's are good for about 0.15 seconds over anything else, and a digressive rate bilstein is good for 0.3 seconds over a linear Bilstein. On a 1/4 mile track three tenths is the difference between the pole and not making the field.
The suspension as a whole.
A normal, round bump stop will make the setup dual-rate. What shape is going to make a bumpstop progressive? There is a trick on weight transfer between the corners that I don't think I'm allowed to discuss unless someone is paying me to tell them. We (R&H) like to overshock cars most of the time, we also exclussivly use Bistein's in our setup's. In our experiance on shorttrack, asphalt or dirt, Bilstein's are good for about 0.15 seconds over anything else, and a digressive rate bilstein is good for 0.3 seconds over a linear Bilstein. On a 1/4 mile track three tenths is the difference between the pole and not making the field.
I'm confused perhaps by the words being used...then it becomes progressive...by it you mean the damper?
#37
Originally Posted by meb
Okay, call me dense. I still do not understand the intimate relationship between bumpstop, spring and damper. How does a bumpstop make a linear rate spring progressive when it really controls the damper's movement? I wrote in a previous post, progressive damping. I was quite literal with my choice of words.
The shock rate must match the bumpstop+spring+bar rate, and it's not a big deal if you have adjustable dampers.
#38
#39
Originally Posted by orthomini_jr
Or Bilsteins
Sorry if I'm a little biased, but that's what happens when you're trained by the man that Earnhart Sr. nicknames Mr. Bilstein
Sorry if I'm a little biased, but that's what happens when you're trained by the man that Earnhart Sr. nicknames Mr. Bilstein
On the original topic: as meb pointed out, most aftermarket "progressive" springs are dual-rate springs. You see the softer coils stack solid and then the rate changes to the stiffer rate of the remaining coils, much like the tender spring on coilovers. OEMs like Ford on the Taurus actually use evenly spaced coils with costly variable thickness wire and/or variable diameter coils; those are truly progressive in rate. Smaller diameter coil=higher rate, same effect as thicker wire. Beehive/barrel shaped springs for the Mini may therefore actually be somewhat progressive after all...
Originally Posted by dominicminicoopers
p.s. I asked my dealership's techs about the bumpstops and the tech actually said the MINI doesn't need the front bumpstops whatsoever. The tech recommended even removing them. Wierd huh?
#40
Imagine those Japanese cars that already sit on their bumpstops at rest and can have 4" of wheel travel by compressing the bumpers further.
This seems like a perfect way to fine tune the suspension - sitting on the bumpstops at rest. Why don't we see more of this within the aftermarket world? Expensive?
orthomini jr
There is a trick on weight transfer between the corners that I don't think I'm allowed to discuss unless someone is paying me to tell them.
Do tell! I can imagine that using different types of bumpstops ( length and progressivity - is that a word?) might help with weight transfer...
Thought of something else too; the 4" bumpstops in the above example seem to me to work thru the entire range of suspension movement, giving one what appears to be a tremendous amount of design control. I would think this would be a much lighter set-up as well??? I know I've danced around that comment above a few times, is this true?
This seems like a perfect way to fine tune the suspension - sitting on the bumpstops at rest. Why don't we see more of this within the aftermarket world? Expensive?
orthomini jr
There is a trick on weight transfer between the corners that I don't think I'm allowed to discuss unless someone is paying me to tell them.
Do tell! I can imagine that using different types of bumpstops ( length and progressivity - is that a word?) might help with weight transfer...
Thought of something else too; the 4" bumpstops in the above example seem to me to work thru the entire range of suspension movement, giving one what appears to be a tremendous amount of design control. I would think this would be a much lighter set-up as well??? I know I've danced around that comment above a few times, is this true?
#41
When we're setting up a Late Model on dirt we don't/can't go with a Bilstein that is made for a certin car. We're using a 46mm Bilstein with the valving that we need. For instance a ZV, which is a digressive rate, I think a 3530.
The TC is a Twin Tube shcok that doesn't even get mentioned to us. Otherwise, on a normal car, if you're running sticky race tires then we're going to put you on the sports. If that doesn't work well enough then you'll have to pay the $65 to get the shcok revalved the way we want it.
We don't use bumpstops for weight transfer, we use shocks.
The TC is a Twin Tube shcok that doesn't even get mentioned to us. Otherwise, on a normal car, if you're running sticky race tires then we're going to put you on the sports. If that doesn't work well enough then you'll have to pay the $65 to get the shcok revalved the way we want it.
We don't use bumpstops for weight transfer, we use shocks.
#42
Originally Posted by BFG9000
....
On the original topic: as meb pointed out, most aftermarket "progressive" springs are dual-rate springs. You see the softer coils stack solid and then the rate changes to the stiffer rate of the remaining coils, much like the tender spring on coilovers. ...
On the original topic: as meb pointed out, most aftermarket "progressive" springs are dual-rate springs. You see the softer coils stack solid and then the rate changes to the stiffer rate of the remaining coils, much like the tender spring on coilovers. ...
Last edited by flyboy2160; 07-06-2005 at 06:17 AM. Reason: spelling
#43
Agreed. But, spring and damping rates are closely guarded by manufacturers...makes this subject appear as a black art.
We don't use bumpstops for weight transfer, we use shocks. I simply thought you were referring to bumpstops, given the subject matter, and, what appeared as an innuendo to me.
We don't use bumpstops for weight transfer, we use shocks. I simply thought you were referring to bumpstops, given the subject matter, and, what appeared as an innuendo to me.
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