|   suspension spring question | confused
Mar 16, 2003 3:51 PM | | a linear coil spring: does it remain truely linear to the end of its stroke or does it ramp up a little? when you get near coil bind, do all the coils touch at the same time or will it progress from say the bottom up?
Some guy i know argues that linear springs still ramp up even at the end of the stroke. |
| re: suspension spring question | Monte
Mar 16, 2003 4:15 PM | | They should be linear till the end. Or at least very close, unless it's a special die spring which should be really really close to linear all the way. All the coils should be pretty closely spaced near coil bind, within tolerances of metalurgy.
Monte |
| re: suspension spring question | confused
Mar 16, 2003 4:47 PM | | ok, then does it sound right that a 500x2.o spring needs 500 pounds of force to move 1 inch and another 500 pounds to move the second inch for a total of 1000 pounds of force to compress a 500 pound spring 2 inches? |
| Correct'o mundo.... | Monte
Mar 16, 2003 5:03 PM | | that's a linear progression. A progressive spring would need say 500 for the first inch, then an additional 600 for the second, 700 for the third and so on as an example.
Monte |
| well, just to be an... | zedro
Mar 16, 2003 5:28 PM | | springs arent 100% linear, but close enough for our purposes. Springs that are 'assumed' to be linear are measured within their operating range.
I also heard somewhere that the coils we buy are usually only 5-10% accurate anyways. |
| Right'o.... | Monte
Mar 16, 2003 6:06 PM | | that's what I meant when I said "within tolerances of metalurgy". I might have used a better description, like "within 5% or 10%". Or something like that.
Monte |
| Zedro........ | please
Mar 16, 2003 7:59 PM | | I have a friend who says his 2001 (I think) Kona Stinky 5 inch travel bike is so close to a Turner RFX/5 Spot that the differences cant likely be felt.....One thing he says is the Linkage V2 program means very little in showing the faults in a bike because he says the rider and spring and shocks add too many variables, and allows the tuning out of faults with springs and damping. He says the spring though maybe claimed linear is nowhere near linear. Saying its a way rising rate. I think he's full of crapola, but I would like to hear your thoughts on this. |
| i dont know exact figures... | zedro
Mar 16, 2003 8:24 PM | | i would have to bench test a couple of springs for the extent, but its not way huge (is that a number? ;).
One thing for sure is that a progressive spring cannot take the place of a decent linkage activated shock, since the latter also has an important effect on damping.
Also other things are going on with the RFX as far as drivetrain performance, and i doubt any seasoned rider would confuse the twos handeling. Using shocks as a band-aid to bad designs is not ideal, and not entirely feasable. Every mechanism has a limitation, so all aspects of the suspension have to be designed for. I'm not quite sure what your friends point was; does he think suspension design is random and its upto shock tuners to clean up afterwards?
I should note that Kona changed their 5" Stinky designs in 2001 to an absolute garbage shock rate. As an example, i used a 450# spring on my '00 Stinky, correctly set up for light DH purposes. But using a 500# spring on a 2001 Stinky, i could bottom it out hopping up and down in the parking lot. You would be hard pressed to tune a shock so it went back to the previous years feel. |
| i dont know exact figures... | ok
Mar 16, 2003 8:31 PM | | he is 185 pounds with a #600 spring on now and the starting force is high, meaning it feels stiff early then it bottoms easier than expexted, that is what I felt and he even said he can bottom it easily which goes to further support your statement about 00 vs. 01 stinky. What about pedaling between the RFX and the 01 Stinky? |
| yup... | zedro
Mar 16, 2003 9:02 PM | | thats it, that is what a regressive rate is. I think designers do it to fool people into thinking their suspensions dont bob as much, even tho its at the expense of a supple suspension.
I've never tried an RFX, although it has the reputation of being one of the best pedallers and bikes of its class. It uses a Horst type suspension, and is supposed to be very neutral under power, whereas the Stinky likes to compress a bit. But all in all, the bikes are not in the same league.
BTW i would suggest a rocker upgrade for the Stinky (dangerBoyCNC or BETD). It will correct the problem and add an inch or more to the travel. |
| Over a large range | Dougal
Mar 16, 2003 10:03 PM | | Over a large range the coil springs are linear. But both at the start and at the end of the travel they're progressive.
This is the result of individual coils binding, making the spring stiffer as it goes through stages.
At the start all coils are moving, often even the end mitred part coils are, these have a very soft rate.
A few millimetres into the compression, the end coils have bound and the spring will be pretty much linear for the majority of the stroke. This is where the spring rate should be measured.
However near the end the coils will again ramp up one at a time, increasing the rate until the spring has fully bound.
As for the RFX/Stinky. The friend is defending his purchase. I've ridden 5spot/RFX light's (one of each) and I've ridden several Kona stinky's. There is no comparison in pedalling or braking behaviour. In a perfect world we'd all be riding the Turner.
Spring and damper settings cannot change the behaviour resulting from suspension geometry without having major negative impacts on the suspension performance.
Dougal.co.nz |
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