Hey, Just got a 888rt and have not ridden it. Just wondering if it was good and some of it's weaknesses and some of it's strengths.
888rt Good????
- Thread starter mtbfreerider19
- Start date
good question to ask BEFORE you get a fork.
bad question to ask AFTER you get a fork.
bad question to ask AFTER you get a fork.
by 888rt, I hope you mean rc, I have no idea what a 't' would stand for.
888 Disadvantages:
Super tall fork with the factory 'm' crowns (the 8" fork is 2" longer ac than most 7" forks). Get go-ride, risse, or new marzocchi drop crowns and your golden.
The compression adjustment doesn't really do much. If you have a steeper head angle you may find this to be a problem, the vast majority of people don't. Marzocchi does make an aftermarket piece to help with this (see go-ride.com).
A tad heavier than a boxxer or fox.
888 Advantages:
You aparently already own one.
Marzocchi reliability.
Very supple fork with excellent small bump sensitivity.
Value. i.e. low price compared anything that could be considered better.
I have one on my dh bike, and at first considered swapping it for a Fox 40 rc2. I've since been very impressed with it's damping ability and durability. I have no desire to switch to another fork.
888 Disadvantages:
Super tall fork with the factory 'm' crowns (the 8" fork is 2" longer ac than most 7" forks). Get go-ride, risse, or new marzocchi drop crowns and your golden.
The compression adjustment doesn't really do much. If you have a steeper head angle you may find this to be a problem, the vast majority of people don't. Marzocchi does make an aftermarket piece to help with this (see go-ride.com).
A tad heavier than a boxxer or fox.
888 Advantages:
You aparently already own one.
Marzocchi reliability.
Very supple fork with excellent small bump sensitivity.
Value. i.e. low price compared anything that could be considered better.
I have one on my dh bike, and at first considered swapping it for a Fox 40 rc2. I've since been very impressed with it's damping ability and durability. I have no desire to switch to another fork.
umm.. dido
i don't follow. how do compression adjustment and head angle relate?Biscuit said:
Mostly to how the fork dives under braking.mandown said:
When you hit the brakes and your weight shifts foreward, the fork compresses (especially on steep stuff) making your suspension less capable. Extra compression damping helps the fork resist diving.
A slacker head angle isn't as affected by the weight shift and doesn't need this extra damping, allowing the fork to be tuned for bump compliance.
Head angle affects how the fork compresses against bumps also. If you think about the actual angle of impact and the direction the fork compresses, a slacker front end will be more effective at absorbing hits.
i see what you are saying. however, i still don't think that the head angle and the compression adjustment are directly related. if the fork's basic compression characteristics are fine for a rider's weight and frame geometry then the ability to adjust the fork is meaningless since no adjustment is needed. a more realistic situation is that the rider will need to adjust his compression for many factors other than head angle. if the fork's design limits the adjustment range, head angle is going to be one small part of how the fork feels.Biscuit said:
i agree the head angle is a factor in how a fork feels. it may influence the rider's desire to adjust compression. however it has nothing to do with the forks range of adjustment.
For the most part I agree with you.
I was trying to sau something more along the lines of this:
Any combination of heavier rider, rougher terrain, riding style, steeper head angle may leave the rider wanting more compression damping.
My old dh bike with a 67 degree head angle, compared to my current rig with a 65 degree head angle, needed much more compression damping to keep the fork from diving. So, same rider, terrain and style. Geometry made a noticeable difference in the way the suspension reacted to bumps and braking forces.
Would most people notice it... I doubt it. But I've become kindof a tech/setup snob lately.
I was trying to sau something more along the lines of this:
I certainly wish the 888 had more noticable compression adjustment, but it seems to be dialed right out of the box (post break in period) for the vast majority of aplications.mandown said:
Any combination of heavier rider, rougher terrain, riding style, steeper head angle may leave the rider wanting more compression damping.
My old dh bike with a 67 degree head angle, compared to my current rig with a 65 degree head angle, needed much more compression damping to keep the fork from diving. So, same rider, terrain and style. Geometry made a noticeable difference in the way the suspension reacted to bumps and braking forces.
Would most people notice it... I doubt it. But I've become kindof a tech/setup snob lately.
odd. i would think that a slacker head angle would move the fork closer to parallel with the ground, making front-to-back forces (like braking) more influential.
That's a really good point.mandown said:
Feel free to disagree with me, but my thinking goes like this:
The majority of braking forces come from the center of mass (your body - just in front of your belly) pivoting around the rear axle.
You pull the brakes and the resistance of the tires causes a foreward weight shift that generally pivots around the rear axle. That circle would have a radius of your wheelbase, basically turning your bike into a giant lever.
Your center of mass (body) resists the foreward weight shift and applies force on the "lever" (bike) pivoting around the rear wheel.
The arc of that radius would apply the force mostly in a downward/vertical direction following the arc.
As you pointed out, the front wheels resistance would still place a lot of horizontal load on the fork, which is why forks flex and creak when braking. A slacker head angle would be more affected by this force.
In my head it seems that, since the fork is more vertical than horizontal (i.e. steeper than 45 deg) the direction of that force wouldn't significantly compress the fork, it would lead more to flexing.
This is all just a theory in my head. I havn't drawn anything out or done any math to support it. It just seems to make sense to me.
Feel free to point out flaws in my logic.
i thought about the arcing weight shift theory. however, the way i see it, the arc only works if that is how you let your body weight shift. if you hit the brakes and your torso gets thown forward, with your legs extending and your arms bending at the elbow, then i can see the arc. on the other hand, if you have the strength to keep your arms from bending at the elbow and you keep your weight back behind the seat and low over the tire, then the force is more of a front-to-back as i described earlier.
other factors to consider will be braking in corners (i know brake BEFORE corners, not IN them) or even just riding through corners. if you have a berm, you can hold yourself centered but the curvature of the corner will have an impact on the forks compression. tight corners will probably compress the fork more on frames with slacker head angles. tight corners will probably flex forks from front to back on frames with steeper angles. maybe i am oversimplifying, but that is how it appears in my head.
of course, applying similar logic, hucking to flat would require more compression damp on steeper head angles to resist the vertical force. such hucks would put more flex stress on slacker angles.
dropping to tranny would probably require more compression damp on slacker head angles. such drops would put more flex on steeper head angles.
does this sound right to you?
other factors to consider will be braking in corners (i know brake BEFORE corners, not IN them) or even just riding through corners. if you have a berm, you can hold yourself centered but the curvature of the corner will have an impact on the forks compression. tight corners will probably compress the fork more on frames with slacker head angles. tight corners will probably flex forks from front to back on frames with steeper angles. maybe i am oversimplifying, but that is how it appears in my head.
of course, applying similar logic, hucking to flat would require more compression damp on steeper head angles to resist the vertical force. such hucks would put more flex stress on slacker angles.
dropping to tranny would probably require more compression damp on slacker head angles. such drops would put more flex on steeper head angles.
does this sound right to you?
also, i see your idea about the braking forces pivoting around the rear axle (hence using your rear brake on a moto when you are in the air to bring the front end down). braking while in the air has different forces than when you are on the ground. while on the ground, you are using both your front and rear brakes (in most cases). this creates more of the back-to-front weight shift i described above. i think this holds for using front brake only, rear brake only, or a combo. if you use just your rear brake. you do have the forces pivoting around the axle. however you also have your body weight being thrown forward (like hitting the brakes in the car and having your body press against the seat belt). if you use only your front brake. the pivot becomes the front wheel. in either case, i think the force from the weight shift will be tangental to the arc around either axle. the force will translate to the fork to differing degrees depending on which arc you pivot from (or blend of the two) AND how you hold your body through the weight shift.
somebody with a degree in physics get in here and clear this up for us.
somebody with a degree in physics get in here and clear this up for us.
the RT was the budget version for 04, so the 888VF for 05. no ajustments, with dual SSVF valving the vs HSCV openbath system of the R/ RC. the RT also comes in either 170mm or 200mm.mtbfreerider19 said:
honestly, for the money you should have sprung for the 888r/ RC.
i didn't pay for it i traded my Boxxer ride for it.
ya i also got the one with 200mm
The whole huck to flat vs. huck to tranny thing makes sense.
The problem I see with cornering forces is your wheel is free to spin (unless your braking or hitting bumps in the corner) so front to back flex would be minimal, the only real movement would be compression from the massive g's your pulling.
The addition of a front brake throws additional moments into the mix, but the rotational forces are still there.
Weather or not you allow your weight to shift doesn't make sense to me.
First, if you allow the shift you are only deferring the application of force (unless you allow yourself to be thrown off the bike). The only affect it has is the change in the location of the center of mass when the force is applied, which would significantly affect the reaction.
If you do not allow your body to shift the tangential force is applied immidiately to the bike (i.e. the lever). If I could draw a picture I would, but imagine an upsidedown 'T'
like this => __I__
At each end are your wheels. If a horizontal load is placed on the top of the "I" (your body resisting a weight shift), while the wheels are resisting foreward motion, the bike/lever/T would want to rotate, and move foreward at the same time.
Your brakes/tires are resisting the foreward motion. So, your fork would a) flex resisting the foreward motion; b) compress from the rotation.
It seems that the only thing we are debating is how much of that force is distributed horizontally vs. rotationally.
The compression/decompression of the suspension, changing the length of the fork/wheelbase as well as the changing location of the center of mass as the suspension compresses and rider moves with/against the weight shift. This is way more complicated than I had originally imagined.
I'm guessing there would be some sort of a sliding curve.
The problem I see with cornering forces is your wheel is free to spin (unless your braking or hitting bumps in the corner) so front to back flex would be minimal, the only real movement would be compression from the massive g's your pulling.
I disagree. In the air, the momentum from the spinning wheel is grabbed by the brake and transferred to bike rotation. The same thing happens on the ground but the bike isn't as free to rotate.mandown said:
The addition of a front brake throws additional moments into the mix, but the rotational forces are still there.
Yes, body position does have a huge impact on the direction of the forces.mandown said:
Weather or not you allow your weight to shift doesn't make sense to me.
First, if you allow the shift you are only deferring the application of force (unless you allow yourself to be thrown off the bike). The only affect it has is the change in the location of the center of mass when the force is applied, which would significantly affect the reaction.
If you do not allow your body to shift the tangential force is applied immidiately to the bike (i.e. the lever). If I could draw a picture I would, but imagine an upsidedown 'T'
like this => __I__
At each end are your wheels. If a horizontal load is placed on the top of the "I" (your body resisting a weight shift), while the wheels are resisting foreward motion, the bike/lever/T would want to rotate, and move foreward at the same time.
Your brakes/tires are resisting the foreward motion. So, your fork would a) flex resisting the foreward motion; b) compress from the rotation.
It seems that the only thing we are debating is how much of that force is distributed horizontally vs. rotationally.
This hadn't occurred to me before. It seems you would have a combination of horizontal and two rotational forces. One pressing the front end down, one lifting the rear up. Since 70% of your braking forces come from the front wheel this would cause a whole mess of moments.mandown said:
The compression/decompression of the suspension, changing the length of the fork/wheelbase as well as the changing location of the center of mass as the suspension compresses and rider moves with/against the weight shift. This is way more complicated than I had originally imagined.
I'm guessing there would be some sort of a sliding curve.
I'm PM'ing this thread to dw since he's the smartest guy I know. And he designed the dw-link which has a lot to do with what we're talking about. (www.dw-link.com)mandown said:
I think people are trying to get this thread back on topic...Sorgie said:
Bastards.
i gave it a new homeBiscuit said:I think people are trying to get this thread back on topic...
Bastards.
http://www.ridemonkey.com/forums/showthread.php?p=1844889#post1844889