Powered by Outside

Marz. rear suspension help - Injured

PB Forum :: Downhill
Marz. rear suspension help - Injured
  • Previous Page
Author Message
flag Visi
Posted: Jun 9, 2012 at 21:56 Quote
Last year I bought a Giant Glory towards the end of summer, begging of fall. I got the bike for $850. It has a Marz. 888 RC3 fork and Roco R rear. I rode it a few times and found a few problems but put it up during winter for Snowmobiling season. The first ride out this year I was going to take it easy since I knew I needed a new saddle since the rails were bent and the rear shock needed a new spring. That tends not to happen with me. On the last run on the last step down of the day my rear suspension bottomed out and caught the seat making me slide. I washed out and went over the bars into a tree. When I got to the ER I found out I fractured my back in eight spots on five different vertebra's and have two mild bulging discs.

Proof
Unsecure image, only https images allowed: http://i1141.photobucket.com/albums/n583/Visi34/IMG_1390.jpg
Report
Unsecure image, only https images allowed: http://i1141.photobucket.com/albums/n583/Visi34/diagnosis.jpg
Impact - Bruising and Major Swelling
Unsecure image, only https images allowed: http://i1141.photobucket.com/albums/n583/Visi34/Swelling.jpg

Unsecure image, only https images allowed: http://i1141.photobucket.com/albums/n583/Visi34/back.jpg
My question is what spring should I get? I can't double check what spring I have on the Roco right now but, I am pretty sure it is a 500lbs spring. I weight 210-215 normally. Any recomendations on saddles would be helpful too.
flag jonbikes
Posted: Jun 9, 2012 at 22:49 Quote
I'm not entirely sure what you are looking for here. Yes, you are looking for someone to tell you what weight coil to get but I feel as if you want more out of this.

I don't mean to be a dick but coil weight had nothing to do with your crash. Bike set up was the sole cause of that, if your seat were at the proper height you would have been fine. Chances are with a properly tuned shock you could probably go down a weight grade on your coil, 75% of the downhill community run their suspension to stiff. You should be bottoming out somewhat regularly, as in a couple times a day or roughly 10% of the bumps and terrain should cause a soft bottom out situation. If you have 8" of travel it's there for a reason, use it.

Your crash was certainly harsh and it sucks to see a fellow rider go down and get hurt, but to soft a coil was not the issue.
flag Visi
Posted: Jun 9, 2012 at 23:15 Quote
Why don't you just be blunt and say it was my fault....who knows it probably was. I was looking for help. I already said my saddle rails were bent and my tire hit it. I know if it was higher I would of just rode out but, I bottomed out a lot more than 10% that day. It's not like I can go to my shop and find the stoke length right now. Just getting from my bed which is the couch to the bathroom is a chore. If it sounds like I am looking for sympathy I'm not. I'm just telling my story and probably shouldn't of. BTW, I am not a pro by any means and I am not comparing myself to anyone but, look at Aaron Gwin at Val di Sole and tell me his suspension wasn't stiff. Dick, yes. Rookie, yes. Helped, not really.
flag jonbikes
Posted: Jun 9, 2012 at 23:22 Quote
Shock info can all be found online, something that you should be able to manage since you are here. As far as an answer on your coil, if you think you have a 500 now then get the heaviest one that you can find and then go a weight lighter untill you run into problems again. Be sure the bike is in safe working order and have at er. Also, bent seat rails had nothing to do with this either.
flag Visi
Posted: Jun 9, 2012 at 23:31 Quote
I've looked. Marz. doesn't make a higher spring rate. Their website sucks and I can't find any useful info. That's why I am asking. I know other companies might fit but I don't know of any other brands would work. I know if my seat was higher I probably would of rode out just fine but, that wasn't the case.
flag jonbikes
Posted: Jun 9, 2012 at 23:35 Quote
If marz doesn't make a heavier spring you could try a fox. I'm nearly positive a manitou coil will not fit, but the fox might. Other options are switch shocks. A shock with a better damping system can be tuned to not blow through travel whilst maintaining proper small bump compliance and still use its full travel on larger hits without a harsh bottom out. You could look at an air shock as well.
flag kizzapalooza
Posted: Jun 10, 2012 at 23:50 Quote
Maybe later on before you ride again, take the coil off the shock then put the shock back on. Without the spring you can cycle the bike through its stroke to make sure the saddle doesn't hit the tyre.

As for the injury, yeah they're not nice, especially spinal injuries. Lucky to not damage the nerve though, 8 fractures on 5 vertebrae? Lucky. Just make sure your bike is set-up safely as blaming the bike is not a confidence inspiring excuse.
flag Visi
Posted: Jun 11, 2012 at 0:48 Quote
I agree, I got lucky with how things turned out. Thanks for the info on the shock cycle. I was already thinking about just taking the shock completely off to see where the tire ended up.
flag orangeracer
Posted: Jun 11, 2012 at 8:54 Quote
Frist take the spring off the shock and cycle the suspenion thought all of its travel and make sure theres nothing getting in the way(not so important on the front). next put the spring back on and turn all compression dampening off all the way, and get on the bike (when your in shape to agin) with all your normal ridding gear. this is the part where you may need help from someone els. But jump on the bike cycling thought its travel and stop, then mesure how far the bike is in its travel and depending on what type of ridding you do you want to use any where from 25-10% sag. if you can get that with turning the spring preload say with in 10 turns your spring weight is probally ok. if thats all set and you cant stop bottoming with the high the high speed compresson turnd up you may need to look at getting the shock vavled for your weight or a better shock with bottom out control.
I hope that helps and hope you get ridding sooner then latter.
flag jonbikes
Posted: Jun 11, 2012 at 10:22 Quote
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.
flag orangeracer
Posted: Jun 11, 2012 at 18:52 Quote
lol. Yes, He's right no more then 2-5 turns on a bicycle to set sag. i let my motocross mind take control for that part, thanks for catching it. just to be sure i double checked what Marzochi says for there shocks and they say no more then 5mm on the preload colar. donno how may turns that is but keep it in mind.
flag jonbikes
Posted: Jun 11, 2012 at 23:07 Quote
That's still not entirely correct. In the moto world it may be more openly accepted as the proper method of setting sag (to add preload) but it still has the same effect as it does on a mountain bike shock. The fact that there is much more weight involved also needs to be taken into account with a motocross bike.

When you have a spring such as one found on a shock and you compress it the reaction to this is stored energy. Say you take a 350# coil and compress it one inch, since moutain bike coils are rated in pounds per inch one could then safely say that the coil in question has 350 pounds of stored energy. This energy is trying to push back and extend the spring to its original length. How hard the energy is pushing back directly relates to the shaft speed of your shock on the rebound stroke, which also directly relates to the force pushing oil through the rebound circuit of the shock. When the same coil is at its full length there is no stored energy, no energy trying to force oil trough the rebound circuit of the shock. This decrease in force as the coil returns to its original length allows the shock to naturally slow near the end of the rebound stroke, giving you a vey very soft return to neutral. Say you turn the preload collar down half an inch past the point of contact with our 350# coil, that means at rest there is 175 pounds of stored energy in the coil. This eliminates the natural slowing and easing of forces at the end of the rebound stroke and gives you a very harsh feel in the rebound stroke when the shock is nearing its neutral position. If you look at air shocks this is a major issue because you obviously have a lot of stored energy in compressed air, and you have say 175psi in the shock when it is in its nuetral position. There you go, same problem. This is where the negative air spring steps in, it balances the forces to trick the shock into thinking that there is no stored energy in the air spring, allowing you to have that smooth rebound stroke that you get with a coil shock. If an air shock did not have a negative spring it would top out constantly and be so harsh it would likely shake you clean off the bike. This principle goes for any shock or fork, and any other shock absorbers outside the two wheeled world that opperates on the same basic principles as the shocks that we know.

And theres your reading lesson for the next two years!
flag Visi
Posted: Jun 12, 2012 at 2:50 Quote
So what you are basically saying is when you tighten your preload collar up it adds that amount of energy stored depending on what weight spring and how much you tightened up your collar up to the end of your rebound at full length?

Say your have the same numbers...

350 Lb spring and it is tightened up a half an inch. That would give the last inch of rebound only 175 Lbs and the other 175 Lbs has to go somewhere to right? Since the spring is rated for 350 Lbs. and only 175 is being used. Would and are you suggesting that the other 175 Lbs would be transferred somewhere else, like through the tire to the ground? This would make sense to me.

Also, say you have a 3.0+ spring. Since the the spring is being compressed three plus inches at full stoke or bottom out is the force of stored energy exponential or multiplied?

350 x 3 = 1050 Lbs.
350 ^ 3 = 42875000 Lbs (Not likely)

Or could it be something like this?

First inch would compress 3 times.
Second inch would compress 2 times.
Third ince would compress 1 time.

((350 x 3) + (350 x 2) + (350)) = ((1050) + (700) + (350)) = 2100 Lbs
flag jonbikes
Posted: Jun 12, 2012 at 4:20 Quote
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.
flag Visi
Posted: Jun 12, 2012 at 12:52 Quote
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
  • Previous Page

 


Copyright © 2000 - 2024. Pinkbike.com. All rights reserved.
dv56 0.011587
Mobile Version of Website