Marzocchi forks - no sag, but dive heavily when braking

trevorfuller

I've just built up my first full sus bike (only ever ridden HT before), and am having a few problems with getting the front suspension set up correctly.

Rocky Mountain Slayer Cult frame, Fox RP3 rear shock and a Marzocchi All Mountain I (2006) fork on front.

The main problem is that when I sit on the bike there is no sag on the front forks. They don't drop at all. Yet when I brake they dive quite heavily (tho they don't bottom out).

Firstly I'm wondering if there is not enough positive air in my rear shock. The sag is about 40% of the shocks travel. Would the rear shock being to soft effect the sag on the front forks? Secondly I could reduce the positive air in the front forks to increase the sag, but I'm worried that this would effect the already soft compression when braking? And thridly perhaps my weight is shifted too far back on the bike?

Any tips any of you have on setting up a the shocks on a full sus bike and weight distribution woudl be very welcome.

Cheers,
Trev.

nicklouse

do you want 40% sag on the back?

it will slacken the head angle which will increase the stiction in the fork.

get the bike set up first.

trevorfuller

do you want 40% sag on the back?

No. I've got a hi-pressure shock pump beign delivered, so that's first job hopefully tomorrow.

Hopefully that will make some difference.

ddoogie

40% at the rear is a bit too much. No wonder your forks aren't at the correct sag point; none of your weight is forward.

When setting up the sag on forks, you should have all your weight over the front in the "attack" position (standing up, weight forward). If you measure sag whilst sat down you wont get the correct amount.

The Brake dive sounds like a low-speed compression damping issue. I'm not familiar with Marz AMs, do they have a low-speed compression adjustment?

Diplomat

Try here for the full manual.. you definitely need to adopt the trial and error method to set these up for your riding style.
I have the 2005 AM 1's on my Reign and it took a while to find the right set up.

Although, as DDOOGIE says, you need to sort the rear shock too!

http://www.marzocchi.com/Template/listS ... mit=Search

trevorfuller

Cheers for the help guys.

I'll get the rear shock sorted first as soon as my pump arrives, then take it a step at a time form there with the front forks.

It's could be that they only seem to dive so much when braking because they go from nothing, to having my full weight + the braking force applied. Perhaps when I get the rear and my weight distribution sorted correctly the diving may not seem so harsh...

Oh, and the AM I's have a TST control which adjusts the compression damping, but this only has a limited effect at the moment, again possibly because of all my weight being thrown forward onto the forks.

I'll get the back sorted out then re-evaluate the front I think.
Cheers again.

Diplomat

Sure you'll get it sorted out.. you'll find the AM 1 settings about halfway through the manual. Just download and print off the pages you need or you'll be spooling off pages for ever!!

Splasher

Need to get the rear sorted and then get the sag at the front at about 30%. The TST should have a dramatic effect. Try turning it fully clockwise(the fork should fully lock), then backing it off one click. The fork should stand up under braking much better in this position (called AM+ if I remember correctly).

aphex2k

15-25% sag depending on the style of riding. 40% is too much.

mmm_pie

aphex2k wrote:

15-25% sag depending on the style of riding. 40% is too much.

No, 40% is fine for DH.

trevorfuller

Cheers for the help all.
After getting the shock pump on the rear shock it seems it was only infalted to about 140psi, I've pushed this up to just over 200psi to get the recommended ammount of sag in the user manual (14.2mm apparantly...)

The front shocks did have slightly too much air in them as well, but only slightly.

Anyway the riding position is much better now, my front forks sag nicely and the change in fork length when braking is much less drastic. All in all, a good improvement.

nicklouse

it is supprising what a correctly set up bike feels like.

ddraver

seriously...you should stand up over the front of the bike to set up sag

nicklouse

ddraver wrote:

seriously...you should stand up over the front of the bike to set up sag

No

"be in riding position." if you want to cover most MTB disiplins.

Xc is normally standing up over the front

Splasher

Have you tried stopping hard on the front brake in each of the 5 TST positions to see the difference it makes. I doubt you'll notice much in DS, - or AM position but in + you should find the fork stands up much better and in CL it's locked.