Marz. rear suspension help - Injured

PB Forum :: Downhill
Marz. rear suspension help - Injured
  • Next Page
Author Message
flag pdxmonkeyboy
Posted: Jun 12, 2012 at 14:23 Quote
I think the more valuable formula is =

Jump or drop + flat landing =(broken bike x broken body)/ (degree of flexibility / age)
flag jonbikes
Posted: Jun 12, 2012 at 15:35 Quote
Visi wrote:
jonbikes wrote:
jonbikes wrote:
You should never have more than roughly two turns on the preload collar past the point of contact with the coil. If you crank it down say ten turns it will have major adverse effects on the ending stroke of the rebound cycle.
For the first bit you are thinking of it backward. If you have 175 pounds of seated pressure from preload it then takes 425 pounds to compress the spring the first inch, and then back to 350 pounds for every inch after that.

The extra energy doesn't go anywhere, it remains stored in the coil, and thats the problem. It's still there acting on things.

A coil is linear and for the most part its simply the given weight per inch. So a 3" 350# coil would require 1050 pounds to compress 3". Im sure if you wanted to argue the fact and put the apring in some fancy equipment it woukd show it is slightly progressive, but for what we are talking about as far as I know its the way I've just described. I will however look into this later tonight, I could be wrong.


Do you mean 525 lbs instead of 425 lbs? If this is the case this 350 Lbs x 3.0 spring tightened a half an inch would now be a 408.33 lbs spring overall under these giving rules. I know that it is one spring and don't understand why it only affects the first inch of compression. I could see if there where three different springs at one inch the first only spring being affected. So why is it wrong to tighten up your collar especially since most 3.0 shocks at any weight are more than 3.0+ so the shock stroke seems like it's not an issue. All good info.

(525 + 350 +350) / 3 = (1225) / 3 = 408.33

Yes, I meant to say 525, please excuse my 5 am math.

You are thinking of preload in far to complicated a manner. It does nothing accept for compress the coil without compressing the shock, thus giving you a pressure of 175 pounds at nuetral rather than zero, nothing more and nothing less. A 3" coil will compress more than 3" before it reaches coil bind. Say you add a half in of preload, in order to bottom out the coil will be compressed 3.5" rather than three, and you require 175 pounds more force to do it. The other problem you run into with adding a boatload of preload is coil bind. If you turned down the preload collar say two inches, well now theres only just over an inch of coil to accomodate three inches of stroke.

Making any sense?
flag b45her
Posted: Jun 12, 2012 at 16:07 Quote
http://www.mojo.co.uk/Website2010/html/springcalc.html

this should help a little .
flag Visi
Posted: Jun 12, 2012 at 22:34 Quote
jonbikes wrote:

Yes, I meant to say 525, please excuse my 5 am math.

You are thinking of preload in far to complicated a manner. It does nothing accept for compress the coil without compressing the shock, thus giving you a pressure of 175 pounds at nuetral rather than zero, nothing more and nothing less. A 3" coil will compress more than 3" before it reaches coil bind. Say you add a half in of preload, in order to bottom out the coil will be compressed 3.5" rather than three, and you require 175 pounds more force to do it. The other problem you run into with adding a boatload of preload is coil bind. If you turned down the preload collar say two inches, well now theres only just over an inch of coil to accomodate three inches of stroke.

Making any sense?


Yes, makes sense. 175 Lbs. more pressure on the spring the spring when the preload collar is tightened a an half inch. The shock stroke will only go 3 inches. (175 / 3) = 58.33 lbs extra per inch of shock stroke to compress the spring at full compression. Now the 350lb spring plus the extra amount of preload added per inch at 58.33 lbs would give you a 408.33 lb spring. Correct? Say the 350 Lbs spring has a shock stroke length of 3.25" (http://www.jensonusa.com/Category/Fox-Shox-Spring-DHXVAN-30-Stroke). Now the spring will compress 3.25" before it goes into coil bind. That would mean on this particular set up that you only have a 0.25" of play with preload adjustment before the spring will go into coil bind. This is where tightening your preload collar too much will get you into trouble.


Now my question is...

Are there any MTB companies that make triple rate springs for rear shocks?

As I said before I snowmobile. Triple rate springs are the best suspension package you can get. I don't understand why they are not on MTBs.

Here is a picture of my snowmobile shock with triple rate springs.
Unsecure image, only https images allowed: http://i1141.photobucket.com/albums/n583/Visi34/ebef6076.jpg
The springs on the snowmobile shocks are:

Bottom:
(1.90 x 8.00 (Spring Length) x 160lb)
http://www.zbrozracing.com/1-90x8-00x160lb

Middle:
(2.00 x 2.75 (Spring Length) x 250LB)
[L=http://www.zbrozracing.com/snowmobile/suspension/springs/2-00x250lbx2-75-org[/L]

Top:
(2.00 x 2.00 (Spring Length) x 400LB)
http://www.zbrozracing.com/2-00x400lbx2-00-wht-red

The company that makes my shock is Exit and use individual springs for each rate.

There is another shock manufacture that make a triple rate spring that is only one spring called Raptor.
http://www.raptorshocks.com/store/products/Triple-Rate-Springs-%28Ski%29-.html

This could be awesome on a MTB rear suspension because say you have a 300Lb bottom spring for the little rollers and bumps, a 450 Lb spring for rocks, ruts, and roots, and a 550 lb spring for the jumps and drops.

Add a triple rate spring to a shock like Cane Creek with their Double Barrel with adjustable slow and fast rebounds and it could be even better.

The only problem I see is making a spring with the kind of pressure for such a small shock.
flag pdxmonkeyboy
Posted: Jun 13, 2012 at 1:24 Quote
Don't make it rocket science dude. Buy the appropriate spring for your weight, turn the preload ring till the sag is correct

You don't need a tripple weight spring you need to stop jumping to flat
flag Visi
Posted: Jun 13, 2012 at 1:33 Quote
Yeah, I understand. My bad on jumping to flat, and I will get the right spring as soon as I can. This isn't quite rocket science either. If it's used in other similar applications why can't it be used here? Seems easy.
flag kizzapalooza
Posted: Jun 13, 2012 at 1:42 Quote
Visi wrote:
Yeah, I understand. My bad on jumping to flat. This isn't quite rocket science either. If it's used in other similar applications why can't it be used here?
Because you're overcomplicating it. If you're still having troubles you've got compression adjustments - LSC and HSC!!!! As well as rebound. Razz
flag Visi
Posted: Jun 13, 2012 at 2:00 Quote
Like I said I will get a new spring. I am also planning on getting my shock re valved. I understand that it's a new idea but why is it too complicated? Basically identical shocks but used for different sports. I still haven't heard of a good reason for not having triple rated springs besides they are too complicated. It's not like I am going to get anything custom made. Just asking questions.
flag kizzapalooza
Posted: Jun 13, 2012 at 3:13 Quote
Visi wrote:
Like I said I will get a new spring. I am also planning on getting my shock re valved. I understand that it's a new idea but why is it too complicated? Basically identical shocks but used for different sports. I still haven't heard of a good reason for not having triple rated springs besides they are too complicated. It's not like I am going to get anything custom made. Just asking questions.
I meant about the weightings through several inches. You don't need them really. World cup racers don't use them, and for racing you want a linear rate anyway. Dampening takes care of small rate increases and bottom out resistance, but there's no real reason you'd need a dual rate spring. You would never need a triple rated spring especially. You just don't need it.

Oh I see. Your snowmobile spring isnt a single spring, it's comprised of three seperate coils separated by what appears to be rubber rings. For snowmobiles (which I've never even seen in person before since I live in Australia, but they're just like quads I'd guess), theres a tremendous amount of weight on the back. Then you've got that swingarm thing or whatever the technical snowmobile lingo for it is which would have to provide a lot of leverage force on the shock. That'd blow through the stroke easily, but to prevent excessive bottoming out you'd have to have a higher spring rate. so a triple rated spring is used.

Guessing you already know this seeing as its your sport, but for anyone else, and for me to relate it some more.

Downhill bikes weigh less than 20kg. Mine, which is pretty average, weighs approx 17kg. That's a lot less than an mx bike 100kg, which would be much less than however a sled weighs. MX racer's need stiffer suspension so they usually only need a single rate. Same for DH. You want a stiff set-up.

I know you're trying to find a reason why you crash. Well I guess you are. I would have if my bike was at fault, but I know I'm quite obsessive about mechanical formality, so it was just a small mistake on my part that ended with me snapping both my ulna and radius in my right arm. Just a small mistake but yeah that's how it happens. Several months out aren't fun, but you'll do it. We all face injuries and they only make us stronger mentally.
flag Visi
Posted: Jun 13, 2012 at 3:53 Quote
Since i know nothing about MTB why would you want a linerar rate? Those aren't stock shocks and it has nothing to do with weight. I'm know I landed flater than I should of, it was my fault for knowingly riding a bike not set up right, and I screwed up riding. I got injured. It does sucks. I just think it would be a cool project to try with maybe a little quicker rebound.
flag jonbikes
Posted: Jun 13, 2012 at 4:57 Quote
Man, I've just written several books trying to get you to understand how preload effects the coil and you've completely failed to manage any sort of a grasp on the subject, were talking elementary principles here. You do not need to worry yourself with thinking about tripple rated springs and all that jazz. Also, I'm curios to see how doing something like a tripple rated coil would allow you to run quicker rebound.

Shocks have adjustments forna reason, and a proper shock can tune out almost any issue.
flag pdxmonkeyboy
Posted: Jun 13, 2012 at 9:01 Quote
The reason is probably because snowmobiles and Mtb do different things over different envirOmwnts. It's been a long time since I've been snowmobiling but I never remember railing berms full of braking bumps or flying through rock gardens.

Any sort of rising rate or non-linear suspension is a function of the bike frame. Since you have some time on your hands..sucks that you got hurt dude..it really does. I would call the bike manufacturer and ask then which spring rate they would suggest.

I would also read through some shock literature in terms of which adjustments do what and how thy affect the feel of the bike. Fox shocks have some really good set up guides. But in general..

Set your pre load
Set your rebound dampening so the bike doesn't bounce
Then ride and set your compression settings (too soft and running through the travel or too harsh and bumpy)
Then fine tune your rebound dampening so that your fork and rear shock are evenly matched

The last part is VERY important so that uneven rebound dampening between your fork and shock doesn't make you wheelie or endo over jumps.

If you can scrounge up the cash, titanium springs are the way to go. They last longer, are slightly more reactive, way ALLOT less and you can dial in a bunch more preload on them without worrying about the spring binding as there is much more space between the coils.

Heal up, get fit and progressively work on your jumping skills. MTBing is sick fun and addicting as hell but trying to much to soon can lead to some pretty brutal accidents

Cheers mate!
  • Next Page

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv65 0.011404
Mobile Version of Website