Difference in Shock setup for MX vs. XC

[Zingnut]

I am wondering what is the physical difference in a shock setup for MX vs. XC.

If there are two shocks setup identical with weight, sag, number of springs, length of arms, both have rebound and comp adjustments, and all the other little things including manufacturer. But one was setup MX and one XC.

Is that all in the valving, or are the spring tensions different.

im pretty sure its all valving :confused:

[cdalejef]

Yep, its all in the valving and spring rates. There are no visable differences on the outside.

[Zingnut]

Cool, At least I was on track with my think'n. Thanks for the fast replys!!

Originally posted by Zingnut
Cool, At least I was on track with my think'n. Thanks for the fast replys!! what are you trying to do u old man

[wilkin250r]

Like Jeff said, both the valving and spring rates are different.

I think many people order MX when they should be ordering XC. XC will still allow you to jump, but it will me much softer over small stuff.

[LS@GtThunder]

Originally posted by Zingnut
I am wondering what is the physical difference in a shock setup for MX vs. XC.

If there are two shocks setup identical with weight, sag, number of springs, length of arms, both have rebound and comp adjustments, and all the other little things including manufacturer. But one was setup MX and one XC.

Is that all in the valving, or are the spring tensions different.

Each shock company has a differant approach to this.

There are several issues.

1. Extended length
2. Compressed length
3. Spring rates
4. Spring rate curve
5. High speed compression valving
6. Low speed compression valving
7. Rebound valving

Each shock company takes a differant approuch to these issues.

Here is how I setup the shock differantly for my bikes.

1. Extended length - for mx , I use a longer extended length for 2 reasons - one is that the tire is smaller and I want more wheel travel before it bottoms to help absorb the big hits from big jumps. If the extended length is to long in the front for XC the bike will handle very sloppy and transfer to much weight to the rear when accelerating out of corners in the lower gears. This makes for a bike that is hard to ride in the woods. If the extended length is to long on the rear - the bike will transfer to much weigh to the outside front tire when slowing down going into a corner making the bike corner badly and giving the bike the feeling that the back end is trying to pass the front end. If the rear extended length is to short like the early GasGas bikes - the bike simply will have a very poor ride as there is very little wheel travel to absorb any bumps.

[LS@GtThunder]

2. Compressed length - I run a shorter compressed length for XC due to the taller tires. If the compressed length is to long on any bike - the shocks will bottom out to early giving a poor ride. If the compressed length is to short - your frame will hit the ground on any hard hits.

3. Spring rates - I run very nearly the same spring rates on the front and slightly higher spring rates on the rear for MX.

4. Spring rate curves - I do not run differant spring curves for MX or XC but I do change it for differant levels of riders as those who do not get much seat time need a smoother progression in spring curve to keep from tiring to quick.

5. and 6. Compression valving - I run the same high speed compression valving for both MX and XC but will change the slow speed compression valving when more bottoming resistance is needed for an aggressive rider that does not do his jumps correctly. If the high speed valving is to stiff you will have a harshn ride when hitting kicker bumps on both MX or XC - High speed valving is related to high shaft speeds when hitting sharp kickers or the initial impact when landing off a large jump where as low speed valving is more related to the final stages of of movement just before the shock reaches full compression.

7. Rebound valving is directly related to the spring rate that is used. The only other time that I change it is if more lift is needed as in a supercross type jump.

All of the above does not mean that I use the same springs and valving all the time. It simply means that I run very close percentages in how it related to travel ratios.

Example1: If your front average ratio is 2/1 and everything else is the same as another bike that has a ratio of 4/1 - then the valving resistance and spring rates will be double on the 4/1 setup.

Examply 2: On a no link rear end - it may take 2-3 springs to creat the spring rate curve at the wheels as what a progressive linkage has with a single spring.

To make everything work the same on 2 differant bike may take a very differant setup of the shocks.

Answer to your original question - you better ask the guy who built the shocks that you have a question about as all shock companies have a differant approach.

[Zingnut]

Wow, Now that was an education.

The question was pretty much in general and not dealing with my application. Just always wondered. I have an XC setup now which works great for my riding abilities.

That was very cool to finally get a better understanding into these shocks. I have always been wanting to tear into them and learn the internal workings. I may be starting to get brave enough...

Thanks a million for the explaination, hope this helps others too.

~Jeff

[JOEX]

Originally posted by Zingnut
Wow, Now that was an education.

Thanks a million for the explaination, hope this helps others too.

~Jeff
:macho
Thanks for asking the question, I was wondering the same thing. I have no intention of tearing into them myself but I like to know how things work;)

Thank you Lazarus for sharing all that info. I know every time I have a question for you over the phone you are prompt to answer and tell me everything I need to know. That is why I've been sending you some business your way lately. I think this thread needs to go under the "tech articles"

[wilkin250r]

Couldn't have said it better myself.

Ok, in all honesty, I'm humbled. I couldn't have said that at ALL. I thought I had the monopoly on long, technical posts. Laz, are you trying to muscle in on my territory?;)