Rear linkage - more analyzing...

[sredish]

I'm trying to figure this out. I understand that rear shock linkage changes the leverage ratio as to how the shock is compressed and this in turn makes the shock react differently.

Now, what I have a problem understanding is this. Surely, a shock can be valved and worked to provide the correct dampening and rebounding at a given ratio to perform the way it should based on the linkage that's there, just as the front shocks are properly valved and setup. I don't understand why the linkage would be required to obtain the proper feel of the rear shock when you can simply valve it to certain specifics. Now, if the linkage is an inexpensive way to get a shock to perform better, then I can understand, but if a revalve is required then whats the point.

I've always played dumb about this but I'm about to get my rear shock reworked by Todd @ TCS and I have complete faith in his ability to do magic on shocks. My fronts are absolutely simply amazing and I've ran shocks valved by PEP and Elka as well, they've all be great, but you know how you just feel the shocks and to me, these shocks perform better than any other set I've had. The Elkas had to be sent twice to get the valving where it should and they were nice when finished, but I was always dialing trying to find the "perfect setting". I don't want to get in a long debate about shock builders, just a more specific discussion of the linkage.

Thanks,
Scott

[TrX450rKiD]

The stock linkage, no matter the valving on the shock, didn't give a consistant leverage ratio .. at least thats the way I understand it ...

[kong49]

I don't think the problem is with the leverage ratio it's with the actual angle of the shock.
A revalve won't fix the angle of the shock.

[Cracker]

Originally posted by sredish@Aug 9 2005, 03:48 PM
I'm trying to figure this out.* I understand that rear shock linkage changes the leverage ratio as to how the shock is compressed and this in turn makes the shock react differently.*

Now, what I have a problem understanding is this.* Surely, a shock can be valved and worked to provide the correct dampening and rebounding at a given ratio to perform the way it should based on the linkage that's there, just as the front shocks are properly valved and setup.* I don't understand why the linkage would be required to obtain the proper feel of the rear shock when you can simply valve it to certain specifics.* Now, if the linkage is an inexpensive way to get a shock to perform better, then I can understand, but if a revalve is required then whats the point.*

I've always played dumb about this but I'm about to get my rear shock reworked by Todd @ TCS and I have complete faith in his ability to do magic on shocks.* My fronts are absolutely simply amazing and I've ran shocks valved by PEP and Elka as well, they've all be great, but you know how you just feel the shocks and to me, these shocks perform better than any other set I've had.* The Elkas had to be sent twice to get the valving where it should and they were nice when finished, but I was always dialing trying to find the "perfect setting".* I don't want to get in a long debate about* shock builders, just a more specific discussion of the linkage.

Thanks,
Scott

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I was in the same boat. Wanted the linkage and all. Todd talked me out of it and said the shock can be done the way I want it without the linkage. Only ridden it a few times so I can't reall give an opinion on it yet.

[sredish]

TeeDee, you better sure as **** give me a report. My rear shock will be going out Thursday or Friday to him. I'm not worried about how good of a job he'll do, but I still want to hear how you like it. Do you have the dual rate conversion? Is it revalved as well? What's your sag, when you lift the rear completely up and then let it droop on it's own?

Scott

[Bad Habit]

The problem with the rear linkage, or more accurately, the reason for replacing the rear linkage is not so much to do with obtaining the proper leverage ratio and progression (although it does do that). It has more to do with the location of the suspension travel in relationship to the frame. The rear end has a good amount of travel as it comes, but alot of it is extended travel, not compressed travel. Ideally, you want the frame to be around 1-1/2" off the ground when the shock reaches it's mechanical compressed limit. The way the R comes, that number is closer to 4" (from what I remember). A redesigned linkage can move the shocks relative position higher in the frame, so to speak, as to put the range of travel in a better position. No amount of work done to the stock shock alone is going to change the position of the travel. The compression and rebound speeds can be tweaked to compensate, but that is all they are doing, they are not directly addressing the problem at hand.

Maybe Gabe can chime in here, he can explain it alot better than I can.

[WayFastWhitie]

the rear linkage is a way to make the shock more "progressive" i.e. the shock is gets harder and harder to compress as the swingarm goes up. they have diff linkages so the rearend wont "buck" so it lessens the "progresiveness" of the shock. thats why they revalve the rear shock. get it? lamens terms: the spring rate goes up as the swingarms goes up :)

[Bad Habit]

Originally posted by WayFastWhitie@Aug 9 2005, 08:50 PM
the rear linkage is a way to make the shock more "progressive" i.e. the shock is gets harder and harder to compress as the swingarm goes up. they have diff linkages so the rearend wont "buck" so it lessens the "progresiveness" of the shock. thats why they revalve the rear shock. get it? lamens terms: the spring rate goes up as the swingarms goes up :)

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But a properly designed linkage will do more than just change the progression rate. Changing the progression just to make the suspension action softer is not necessarily the best approach. The suspension is that stiff because it is reaching it's compressed limit, which is what you want.

[sredish]

Well, I've got some linkage here I picked up from Kid, so I'm going to get my rear shock revalved by Todd then try it with and w/o the linkage... we'll see...

[450r38]

I had my rear shock revalved by Todd at TCS with the dual rate ZPS and had the same question as to the linkage and was told it was not needed. So I did not get it and ran it for a couple of months that way and yes it did help but was still not right, had some bucking still going on. Ended up having JH racing revalve the shock for the GT Thunder linkage and man did that help, cured almost all of the bucking and gave me a lot more confidence in the handling. This revalve was still with the dual rate setup.
My suggestion is to get it valved right away for the linkage you will end up with it anyway and it will cost less in the long run.

[86atc250r]

Dan's right...

The linkage has a couple functions. Firstly, it sets up the leverage ratio and curve.

On a stock Honda linkage, as the suspension reaches the end of it's down travel, the linkage starts compressing the shock more quickly - this gives it more bottomming resistance.

More importantly, for what we're all trying to cure, is that the linkage can be altered to place your 9 or 10" of suspension travel where you can actually use it.

Think of it like this. Lets say you have 10" of travel. Your fully bottomed out frame to ground clearance is 4", which would not be uncommon on a stock suspended 450R with 20" XC tires. That makes your extended frame to ground clearance 14". A typical XC setup for an aggressive rider sits at about 8" frame to ground with the rider mounted on the quad.

This leaves only about 4" of down travel before you bottom HARD --- which causes, guess what..... THE BUCK.

On another note --- if you're going to be measuring frame to ground clearance, be sure the chassis is level when you do it. Since the front spindles and rear axle are the pivot points, raising the front suspension will cause a substantial rise in frame to ground clearance on the rear, and vice versa.

Another thing to attempt to do when setting your suspension up is to make sure the front somewhat matches the rear --- i.e. don't make the rear bottom at 1.5" and top out at 11.5" while at the same time having the front bottom at 3.5" and top at 14".. Although that would produce much better results than the reverse scenario....

Getting these basics right for your particular setup will put you well on the way to a great handling machine, especially considering these basics are largely overlooked.

[86atc250r]

BTW - DO NOT have TCS set that shock up for the stock linkage then mate it to the GTT linkage and expect the results to be anything but poor.

If the GTT linkage was only changing the travel location in the chassis, that might be OK, but it's significantly altering the leverage ratio & curve at the same time, and that will cause your newly revalved shock to become WAY too soft, bottom easily, and possibly break parts or hurt yourself.

[Smoker]

From what I understood the stock linkage was too progressive late in the travel and that's what causes the "buck", I think the TCS valving is to help compensate for the linkage rate but does not properly cure it. Not knocking TCS, I'm sure the improved revalve is a lot better than stock, but again, it is not curing the progression problem in the link.

[sredish]

Alright. I don't know why I fight it so... but maybe I'll let Laz do the valve work for me.

Gabe thanks for the explanation. I see what your saying about frame height and all. One other question for you. With a dual rated rear spring, how should my sag in the rear be setup. Right now, there's a lot of sag but someone said with the dual rate setup there will be quite a bit of sag... I'm going to get the shock valved and then try this linkage out, then go to adjusting and playing.

Thanks guys.
Scott

[86atc250r]

From what I understood the stock linkage was too progressive late in the travel and that's what causes the "buck", I think the TCS valving is to help compensate for the linkage rate but does not properly cure it. Not knocking TCS, I'm sure the improved revalve is a lot better than stock, but again, it is not curing the progression problem in the link.*

I haven't done the math, but the progression rate seems very similar to the other Honda rears, in fact, the 450R linkage setup is VERY similar to the 400ex linkage setup, so similar in fact, that I actually use the front 450R link as part of my 400ex setup, with excellent results. The problem is that the progression comes on too soon because the suspension bottoms high in the travel. You can have 35" of travel, but if it's not where you can actually use it, what good is it?

No amount of valving, springing, black magic, or marketing is going to overcome the lack of travel where you need it.

Alright. I don't know why I fight it so... but maybe I'll let Laz do the valve work for me.

You don't necessarily need Laz to do your work, any shock tuner worth his salt should be able to configure your shock to work with his link with the right information and a little attention to detail --- if he can't I'd be really suspect of his abilities.

In fact, there are several well known people marketing Laz's links nowadays. Personally though, if I'm going to go with one of his links, who better to set up my shock?

FWIW, my very first set of aftermarket shocks were TCS. That was a good while ago, but they were decent shocks -- in fact, I'd say that at least the rear was a good deal better than what Mark Baldwin of PEP built for me later. However, now, after having owned at least one (and in come cases, three) of practically everything, Laz does all my shock work.

Gabe thanks for the explanation. I see what your saying about frame height and all. One other question for you. With a dual rated rear spring, how should my sag in the rear be setup. Right now, there's a lot of sag but someone said with the dual rate setup there will be quite a bit of sag...* I'm going to get the shock valved and then try this linkage out, then go to adjusting and playing.

Don't worry about sag - sag settings are for dirtbikes. Concentrate your efforts on frame to ground clearance. If your travel is where it needs to be (i.e. something like 1.5" of bottommed out and 10.5" of extended if you have 9" of travel), then with your frame height set properly (around 8" for xc, little lower for mx) "sag" will be right where it should be regardless of a multi-rate spring setup. Also be aware that with the 450R stock shock being so short, some builders like to stay away from multirate spring setups on it.

The trick is getting the travel where it's supposed to be in the chassis & getting your shock builder to pay enough attention to get you the right spring rates to match your setup and weight. This is one of the reasons "ZPS" is so popular - it allows a level of adjustability that allows for proper frame height settings without having the springs be dead on (which can be a problem in itself).

For the money that we all pay for suspension and shock components I think it's absolutely ridiculous that we don't get better matched setups and don't have more attention paid to detail than what we do....