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Discussion Starter · #1 ·
Hi there

Just recently installed FGK 202 Ohlins 30mm cartridges, and I'm having a weird issue.

My spring rate was calculated by ohlins based on my weight, riding conditions etc, so I'm pretty sure the springs are good.

Here's the problem. I cannot change my front sag number at all. I have the preload at the recommended setting.. I had a friend measure from the fork seal to the bottom of the fork, with the front wheel off the ground.
Then measured the same two points with me on the bike, gear on, riding position.
Sag is 42mm.
increased preload by 3 full turns to try to decrease the sag to around 35mm.
Took the measurement with the front wheel off the ground again. Exactly the same as before I adjusted the preload. (that can't be right can it?)
Sat on bike again, STILL 42mm sag.. wtf..

Maxed out preload.

free sag, (wheel off the ground) STILL unchanged.

Sat on bike. Still 42mm sag.

Am I doing it wrong?

The right height increased at the front with more preload, but it did absolutely nothing to change the sag numbers.

I have the recommended oil level, (160mm I believe) and I'm bottoming out the forks, even with preload maxed out. Like I said before, the springs should be stiff enough.. Maybe I need to change the fork oil level to 150mm.. Anyone know what most race teams have their oil level at?

I tried increasing compression.. didn't really help. Bike is diving too much under braking, too soft feeling in the front.

Any help would be awesome.

Thanks
 

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billdozer
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when the wheel is off the ground you should have the same measurement every time, no matter what adjustments are made to preload or anything else. Free sag is the amount the suspension settles under just the weight of the bike.

and how do you know ride height changed?
 

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Discussion Starter · #3 · (Edited)
when the wheel is off the ground you should have the same measurement every time, no matter what adjustments are made to preload or anything else. Free sag is the amount the suspension settles under just the weight of the bike.

and how do you know ride height changed?
Ahhh.. excellent.. Well that part makes sense then.

Ride height.. it feels slightly higher, turns a little slower, exits wider. However, I could be wrong, if something else caused that.

So, any idea why the preload being at max or zero has absolutely no effect on the sag?
 

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"The Dude abides .. "
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you have to account for stiction when measuring fork sag. There is a lot of surface area of the seals omn the lower tubes. This means you won't get consistent measurements with you on the bike.

you have to measure TWICE, once after bouncing on the bike and letting it rise, then again pulling up on the front and letting it settle. ADD those 2 numbers, then DIVIDE by 2 and this gives you your sag accounting for stiction.

As posted earlier, your extended off the ground # will always be the same. BUT, are you pushing on the front wheel with your foot to account for the top out spring? THAT is your starting extended number..

Also, it may take more than 3 turns to raise the front, and it sounds like you have too soft of springs. WHAT ARE the springs in there? you said "They are right", well, i don't know about that.
 

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Discussion Starter · #5 · (Edited)
you have to account for stiction when measuring fork sag. There is a lot of surface area of the seals omn the lower tubes. This means you won't get consistent measurements with you on the bike.

you have to measure TWICE, once after bouncing on the bike and letting it rise, then again pulling up on the front and letting it settle. ADD those 2 numbers, then DIVIDE by 2 and this gives you your sag accounting for stiction.

As posted earlier, your extended off the ground # will always be the same. BUT, are you pushing on the front wheel with your foot to account for the top out spring? THAT is your starting extended number..

Also, it may take more than 3 turns to raise the front, and it sounds like you have too soft of springs. WHAT ARE the springs in there? you said "They are right", well, i don't know about that.
Thanks for your reply.

Sorry I wasn't real clear on the preload/ride height. I ended up settling for I think about 12mm (12 turns clockwise from 0) of preload, just for now. Preload maxes out at 18 turns (18mm)

That would be enough to raise the ride height wouldn't it? Anyways, I'm not too concerned about that.. I can always adjust the ride height once I get the forks working properly.

So, these having the "top out" feature, would that make setting the sag more or less irrelevant? Would I just tune based on feel and forget about sag?

My spring rate is 9.75 (1.0 and a 9.5). All suited up my weight is about 190lbs

even with preload up to 12mm, and 3 extra clicks of compression from the recommended compression setting, I'm using the entire fork travel (I have a zip tie after every "lap" it's all the way at the bottom, no wheelies or anything, just normal (fairly aggressive, but not jerky) braking.

If I come down a little too hard from a wheelie, (which I try to avoid) it bottoms the crap out of the forks, with a "clunk".

On hard braking, I feel like it definitely "dives" too much.. feels way too soft.

As for the bottoming out issue, I figured I could add a few mm of oil, to increase the effectiveness of the air spring, but that won't effect the initial feel as I believe that only comes into play towards the end of the stroke.

I'm 99% certain that 9.75 is a pretty normal spring rate for someone of my weight, but I don't understand why it feels so soft, uses up all the fork travel, and applying more preload (or less preload for that matter) does almost nothing to change the soft feel and the stroke being entirely used/bottoming out.

Here's what makes zero sense to me: 2mm of preload feels the same as 16mm of preload as far as softness and travel goes, which suggests that maybe it's just malfunctioning and I'm really not adding or removing preload when I turn the adjusters. However, I can feel the spring when I wind it on, and the ride height changes, (which means the preload adjusters are indeed doing something to the springs..)
 

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Parts Pimp
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Thanks for your reply.

Sorry I wasn't real clear on the preload/ride height. I ended up settling for I think about 12mm (12 turns clockwise from 0) of preload, just for now. Preload maxes out at 18 turns (18mm)

That would be enough to raise the ride height wouldn't it? Anyways, I'm not too concerned about that.. I can always adjust the ride height once I get the forks working properly.

So, these having the "top out" feature, would that make setting the sag more or less irrelevant? Would I just tune based on feel and forget about sag?

My spring rate is 9.75 (1.0 and a 9.5). All suited up my weight is about 190lbs

even with preload up to 12mm, and 3 extra clicks of compression from the recommended compression setting, I'm using the entire fork travel (I have a zip tie after every "lap" it's all the way at the bottom, no wheelies or anything, just normal (fairly aggressive, but not jerky) braking.

If I come down a little too hard from a wheelie, (which I try to avoid) it bottoms the crap out of the forks, with a "clunk".

On hard braking, I feel like it definitely "dives" too much.. feels way too soft.

As for the bottoming out issue, I figured I could add a few mm of oil, to increase the effectiveness of the air spring, but that won't effect the initial feel as I believe that only comes into play towards the end of the stroke.

I'm 99% certain that 9.75 is a pretty normal spring rate for someone of my weight, but I don't understand why it feels so soft, uses up all the fork travel, and applying more preload (or less preload for that matter) does almost nothing to change the soft feel and the stroke being entirely used/bottoming out.

Here's what makes zero sense to me: 2mm of preload feels the same as 16mm of preload as far as softness and travel goes, which suggests that maybe it's just malfunctioning and I'm really not adding or removing preload when I turn the adjusters. However, I can feel the spring when I wind it on, and the ride height changes, (which means the preload adjusters are indeed doing something to the springs..)

A couple things to help you better explain to us what is happening:

Ride height is referring to geometry of the bike. The position of the forks in the triple and the length of the shock effect ride height

Rider sag is the measurement from the bottom of the dust seal to the end of the chrome tube on the fork with you on the bike.

Preload doesn't change the spring rate. The spring rate is always the same. Preload changes the amount of weight it takes to initially compress the spring.

I know your track and riding conditions, and on a short slow track with abrupt hard braking sections over and over you will run through travel. You do always want to use as much travel in the fork as possible. When the front end is pinned on the hydraulic lock/bottomed out, you will get vibration feedback into the grips. The bike won't hold as straight of a line on the brakes either. It will feel like you have warped rotors. That's the best way I can describe it.

Clunking coming down off a wheelie could be a need to torque the steering stem or maybe the ram air duct moving too. Just throwin that out there.

What you describe saying the bike transitions slower and harder when you increase the amount of preload in the forks is on par with what you should be feeling when you run less sag in the front without compensating on the shock as well. Without the bike being raked a bit and not having the spread from front to rear there, the bike will turn less sharp and transition slower from left to right.

The method for measuring sag that Greg mentioned is the race tech method I believe. Its a real precise method since it accounts for stiction. I used to stand by that method but after speaking to ohlins and being advised to just measure the extended amount then rider sag to get a baseline I started to simplify things. I generally have the opportunity to work with a customer trackside throughout the day to fine tune off of a baseline.

In the end Harry I believe you have the correct springs. We weigh the same and have the same spring rate on the bike.

What is the measurement fully extended on the forks? My 30 mil kit is one of the early ones and I see my forks are shorter than a lot of people running newer kits. So strange. And what is the position of the forks? How much above the triple? What tires are you on?

Geometry greatly effects weight transfer too.





:YEA
 

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"The Dude abides .. "
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good read above..
bottom line you need to add fork OIL at this point. I run .975 (not 9.75 ;) as well at some tracks, and i'm 165lb, but that is party due to my pace, and using some wicked good tires.
OIL LEVEL (went over this recently in another thread in this forum) is what you control bottoming with after you have the right spring rate, and geometry (see CSD's post above).
Try 5ml of oil at a time to each fork leg. It's very easy..

DO ONE AT A TIME, or the bike will fall all the way down and you won't get it back up high enough to get a stand under it without help. all you need to do is loosen the triple pinch bolt, spin the cap off, and pour in some fork oil (5wt). Repeat on other side. If still bottoming, add 5ml more. If bottoming bad now, may just start off with 10ml to start.
 

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Discussion Starter · #8 ·
Yep, sorry about my delayed reply.. I'm going to come back and answer some of Ant's questions in the next few days (just got caught up with work). Awesome advice, Chief! Thanks very much and, you as well Greg :)
 

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Discussion Starter · #9 ·
A couple things to help you better explain to us what is happening:
What is the measurement fully extended on the forks? My 30 mil kit is one of the early ones and I see my forks are shorter than a lot of people running newer kits. So strange. And what is the position of the forks? How much above the triple? What tires are you on?
Alright, sorry for the delay, I got round to playing with the suspension again finally, today.

So as of right now, I have 7.5mm of gold tube showing above the triple. My forks extended (wheel off the ground) measure at 124.5mm when measuring the chrome (from under the fork seal, to the start of the caliper).

As for the rear, I removed the 3mm spacer when I installed the Ohlins TTX GP shock, and underneath at the adjustment area beneath the blue adjusting nut, I see 4 threads showing.

This is real embarrassing/strange, but for some reason the preload IS doing what it should do with regards to sag now. I have no idea, what was going on before. I guess we must have been doing something wrong.. double/triple checked.. weird.

So, I guess the only issue I have is the bottoming out.

I think 35mm of sag is just about right.. I think as you said, Ant, that the springs are right.. I think I need a bit more oil in the shocks to fix the bottoming out.

I set preload and compression up (Forks and shock) to the recommended specs for a baseline and next time I ride I will fine tune.

Tires at the moment are Dunlop Q3 180/55/17 - 120/17/17

What do you think?

good read above..
bottom line you need to add fork OIL at this point. I run .975 (not 9.75 ;) as well at some tracks, and i'm 165lb, but that is party due to my pace, and using some wicked good tires.
OIL LEVEL (went over this recently in another thread in this forum) is what you control bottoming with after you have the right spring rate, and geometry (see CSD's post above).
Try 5ml of oil at a time to each fork leg. It's very easy..

DO ONE AT A TIME, or the bike will fall all the way down and you won't get it back up high enough to get a stand under it without help. all you need to do is loosen the triple pinch bolt, spin the cap off, and pour in some fork oil (5wt). Repeat on other side. If still bottoming, add 5ml more. If bottoming bad now, may just start off with 10ml to start.
LOL, yes, .975 then. me too. haha.

I will definitely add 10mm of oil in each fork (it's pretty bad, so 10mm should be good I'm guessing)

Thanks for all of the help!
 
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