[ssevy]

I pulled the forks off my 99 Legend last night, and left them draining overnight. Boy does that fork oil ever stink! I have the progressive springs to put in and just wanted to double check the steps. I have read every thread, but a couple of things were not clear. How does this sound:
1- With the forks dry (no oil), drop in the springs, the flat washer, and pvc spacers. With the fork held upright and fully extended, draw a line on the pvc spacer at the top of the fork tube. Use an electric mitre box and cut the two spacers to length. (I assume if there is a slight variation in the marks for the pvc spacers for the right and left sides, you split the difference when cutting)
2- With the fork still fully extended and the spring only(?)in place, fill with oil to 120mm from the top of the tube. (This is where it wasn't clear whether to include the pvc spacers in the tube during the fill or leave them out). Pump the forks a bit to get any air out and doublecheck the oil level. Do this several times.
3-Once the oil level is set and the air is all removed, put the flat washer and the spacer back in, then put the end caps back on. These can be torqued once they are mounted back on the bike.

I noticed that the dust seals are dried out a bit, but there is no oil leakage. I also bought some of those cool bellecourse gaiters to put on. Should I replace the dust seals now, or let them go?

Last comment - I bought one of the Sears Professional model motorcycle jacks, and it works on my Legend perfectly with no spacer board or other jury rigging necessary.

Overall, pulling the forks was very easy and straighforward.

Whoops, one more question - I seem to recall something about not doing the final tightening of the lower fork brace until I compress the front end a couple of times for alignment or something? Can anyone clarify this for me?

Thanks!

 

[900.5669]

Hi ssevy,

that all sound about right to me. Oil measured with forks extended and spacers in. Pump forks to remove trapped air. Yup, I reckon you are spot on.

As for the seals, if they aint leaking, leave 'em be

You are also correct about not tightening the lower yokes until you have bounced the front end a bit to align the forks in the yokes. I always forget that bit.

A note on the fork gators, I took mine off after a while because they were trapping moisture inside. Not sure if that could be a bad thing but It bothered me. Might not be a problem but keep an eye on it.

Nicely done,

Wayne

 

[KD5QOQ]

That oil does stink!!!
The level is usually checked with the springs out and the tubes fully collapsed.
The height I have is 126mm.

 

[900.5669]

Ooops,

Sorry. I'm giving out incorrect information. Fork oil is indeed measured with forks compressed and springs removed. I remember I did it wrong the first time I changed my oil. Man that was a solid front end until I realised

Glad you picked that up KD5QOQ, I need to do mine again soon and I'd have done it wrong if not for the reminder

Sorry Ssevy.

Wayne

 

[ssevy]

Does the 126mm fork compressed fill height apply to the factory springs, or do you have the progressives? I was using Jim's directions, but the inclusion or the exclusion of the pvc spacer when measuring the oil height is unclear when reviewing his old posts - something about a concussion, I think

I did notice that the progressive springs were much shorter than the stock ones, so the pvc spacers will have to be longer than the metal ones which came out. I hope someone can clarify which method of oil measurement is the correct one, and if it is "forks extended and springs installed", does the spacer go in as well before measuring the oil?

Also, the instructions from progressive said that installing with the tight coils down might be quieter, but that the orientation of the springs did not matter. Does anyone have any experience with these springs that would cause you to disagree with that?

I also made a nice little oil measuring device from a small cork and a piece of brazing rod. I'll see how it works tonight.

Thanks for all the help.

 

[900.5669]

I can't tell you about progressive springs I'm afraid Ssevy, I'm going by the instructions for stock springs. I'm not sure on the fill height for your bike either. Its either 109mm for kayaba forks (<vin43509) or 126mm for showa forks (>vin43510)

I could be wrong (see previous post) but I would think that compressed and spring out would be the same for progressive and stock. I don't think either spring would displace more oil than the other. As long as both forks are the same you should be ok.

But don't quote me on it

Wayne

 

[Slinky]

There's a coincidence, I just came in from the garage after changing fork seals and oil. My understanding is the fork level is checked with the spring out and the tube fully pushed in.

I was surprised to find that my forks already have progressive springs installed, maybe the early ones came from the factory that way.

 

[patrol21]

correct, the springs should be removed to check the oil height as well as compressed fully. Dont' forget to draw the forks back and forth a couple of times to remove the air pockets..trust me there in their....also, let the tube sit for a few minute after pumping especially if you went with a heavier oil to give the bubbles a chance to move to the surface. Once you have the right measurement, it's just a matter of putting everything back together....

I also noticed on my 95 that the stock springs are progressive.

 

[IrlMike]

Spacer length - I would consider it this way. The spacer is to set the sag, usually at around 1/3 of suspension travel, say 40mm on ours, bike off stand with rider on board. With progressive rate springs, I would choose at least that, & no less, maybe 45mm. What was your sag before ? (If you don't know, I'd guess at 35mm.) Make a note of the difference - that must be subtracted from your old spacer length (our new spacer starting point). Now, make an adjustment to that figure for the difference in free length of the springs. But...we're not finished yet, what about the different rate of the new spring ? If you don't know the rate of the original spring is compared to, say, the 'early' part of the new progressive, you'll have to guess. Let's say the new spring is 15% lower rate over the 1st 1/3 of travel, 40mm. Therefore you'll need to add another 15% of 40, or 6 mm to your spacer length to get you back to where you were. With those three adjustments to your old spacer (stock is 100mm, I think?), you now have your new spacer length.

One more thing, when using a PVC pipe spacer the extra volume of the plastic is quite significant over the skinny metal spacer. The 'heavy gauge' pipe I used came out with a 35 mm lower oil level needed for 90mm of pipe (spacer) length. The pipe was 24mm ID, 34mm OD (25.4=1"), is that similar to yours?

And another...for reasons of lower unsprung weight (& spring momentum for valve springs) the heavier coiled section is always placed at the stationary end - top for forks.

1 more...spring volume - the difference may not be much (unless you ignore my last point..) but you could try each spring in turn when you've got about the right oil amount in & see if the level moves.

Good luck

Mike

 

[KD5QOQ]

If you doubt what I say about oil level try this: fill to 120 or 126 mm (it won't matter) while the forks are fully extended, now compress them fully and see how much spills all over your hands.
How could you expect them not to blow the seals out of the sliders once you hit the first bump?

 

[IrlMike]

+1 Jimbo

In fact, just try putting the springs in & watch the oil overflow. The extended fork method has to have the springs in before the oil is poured. I use the fork compressed (springs out) method now which is the way Haynes specs it. I've found the front can be fully dropped (wheel in place) with the bike on the centre stand. Just push it down gently & carefully then chock the front wheel.

From what I've read, messing with the air gap is a poor way to tune front forks. Go with stock. Get the spring rate & sag right then the damping. Higher rate springs (for a given weight of machine/rider) will need less damping (& vice versa). If it's not adjustable by other means, change the oil weight. Note that the actual viscosity change vs 'xx'W on the label is only reliable with a particular brand and product range. Best is a high VI or viscosity index (which won't be on the label ) which is a measure of how little (or much) viscosity changes with temperature. I've recently discovered that the forks can take a long distance to come up to a stable temperature...

When the fork legs are fully assembled, tighten the top yoke pinch bolts, leaving the bottom yoke pinch bolts, axle & axle clamp bolts just nipped up, play just removed. Push the front wheel hard a few times into something solid like a breeze block (don't use the brake, it may twist things) then tighten everything up from the top down.

(then finish off the job & check the steering head for free play )

 

[ssevy]

Thanks to all for your input. There has been so much information shared that I am feeling even more confused
I have both the Haynes and the factory manual, and I do understand all of their instructions for oil height measurement at 126mm, etc., but since I was using progressive springs, I assumed that the difference in their size would alter the oil volume, as they won't take up as much room as the stock ones did. Also, based upon all of the threads I read, there seem to be two schools of thought here, one being race tech and gold valves and one being progressive springs. As Jim was a user and an advocate for progressive springs, I was following his directions using the fork extended/spring in method for setting the oil level at 120mm. Not to disagree about one method or the other, but I assume if there was a danger of blown seals that Jim would have discovered it, as he is using the set up he described. Also, based upon his many posts, his advice seems well-informed to say the least.
Mike, your discussion of presag settings was way over my head, and while I can see what you are getting at, I guess I was hoping that I could just follow Jim's simple instructions and be done with it. Maybe it's just my lack of experience, but all of the threads suggest with the pvc cut to the top of the tube I will have a starting presag of 3/4", which I can then adjust by adding more flat washers. Honestly, I am not even sure what too much or too little would feel like, as I am doing the progressive springs to improve brake dive and front end handling, and to balance out the zx-11 shock I have in the back. Maybe I'll get the job done, it will feel better than the stock set up, but not be adjusted to an optimum level, and I won't ever know the difference. Darn, this has turned into a tough job!

 

[IrlMike]

Ok, bear with me ssevy, I'll try & explain a bit better. First off, the gold valve emulators I'm using are not relevant to the discussion of your set up. You can add them later or not, either way, not important here.

You are trying to improve brake dive & generally improve front end handling. Very worthwhile as the Kawa rear units are such a massive improvement over stock, the front end is shown up even more.

You've started by getting progressive rate springs, correct?

In terms of brake dive, this is how I see it.

The problem on our bikes with brake dive starts from the stock kind of compression damping, combined with the way weight transfers forwards on our triples. The damping is very non-linear with speed of fork movement. That means that for relatively slow fork movement under braking, there's very little damping. What's really important in brake dive is not so much the extent of it - how far the forks compress - but how steady & controlled it is, both going down & coming back up.

With progressive rate springs the movement will be quicker at first application of the brake & then begin to slow as the higher rate part of the spring comes into effect. Ideally this part of the spring will be working at a higher 'rate' (inches movenent per lb of weight) than the stock spring. This will all then be a better match with the damping rate across the range of movement, which equals better control of the fork movement.

So your forks will dive & settle back again in a more controlled fashion. Likewise the weight transfer to the front, and the tyre loading vital to smooth braking & your feel of that control.

The basic idea of sag is simply to set the suspension at a point in it's range of movement that allows sufficient movement left in each direction.

This must be appropriate to what it will be asked to do from road bumps (raised bumps) & front brake in 'compression' - & road dips (or over crests) in 'extension'. Only the spring is involved here, damping doesn't come into this.

The amount the spring is initially loaded (weighted down - 'preload') sets where, in the range of available suspension movement, any 'road' caused movement will start from, such that no situation arises where it'll hit the limit bump stops at either end.

'Somewhere in the middle' is what we'd logically choose. In practice, a bit more movement distance allowed under compression than that under extension is better - 2/3 one way, 1/3 the other.

The length of the spacer sets this 'preload' point - 'sag'. So it's just a case of measuring how far the forks compress from full extension (on the mainstand, say) to when it's resting on both wheels with the rider sat on board.

So what I was attempting to do above was to get you back to a reasonable amount of 'sag' after putting in different length & progressive rate springs. (IMO, a touch more than 1/3 compressed, based on my experience with my Hagon progressives.)

The air gap setting should not be such that it plays any significant part as a spring. Starting from atmospheric pressure, it's rediculously non-linear as the volume changes, very quickly making the forks rigid for only a small reduction in starting volume (=oil level). Triumph designed it this way, so I'd honestly reccommend the way they say to set it & the figure they give, per also the Haynes manual. That is forks compressed, springs out, 'x' mm from the top. And the extra volume of the PVC pipe wall is significant, & must be factored in to the oil level.

IMHO, a higher weight of damping (fork) oil would be well worth considering, with the proviso that you don't have to ride continuously on the crap 3rd world roads we have in rural Ireland, most paticularly, the corners. It would likely help further control brake dive movement & other slow speed (fork travel, not road speed) movement.

Hope this helps! (And apologies for any earlier confusion.)

Cheers
Mike

 

[ssevy]

Thanks MIke, that clarifies things tremendously. I did some searching after your earlier post and found some links pasted in an earlier thread to two articles on suspension setup. These explain the presag and damping pretty well, and now I understand the concept of getting the suspension preset to the part of its' travel range to allow adequate movement in both directions. I can say that playing around with the adjustments on the zx-11 shock were very noticeable, and at the extremes made the ride either way too harsh or bouncy like a car with worn out struts.
Now, I assume every setup is a compromise, as traveling with luggage or a passenger is going to alter everything. The article stated to set it up with the rider and his gear on board, so this is my plan. To accomplish this, I measure the available travel of the fork, then try and set it so it settles one third of this distance with me on board. Is this correct? Also, is the travel range of the fork what I can move with it empty and dry, or with it on the bike, and applying the brake and then compressing the fork? In other words, does the spring and oil limit the total available travel, or do they just modulate its' rate?
You mention the pvc wall thickness having an impact on the oil level. If I measure fully extended with all parts inside and use Jim's 120mm will it compensate for this? Or, are you suggesting that I use the factory 126mm and forks compressed and just try it? Again, the progressive springs are shorter, and depending on how much of the original springs were actually immersed in the oil, may have quite an effect on the oil displacement, although the increase in the spacers will tend to counteract this (again depending on how much of the spacers are actually immersed), although I have no idea as to what extent.
I guess I'll begin by cutting the spacers flush, and then measure the presag and sag once it is back together. I can always add additional flatwashers to take up more space, or cut new pvc spacers with the forks mounted.
I was also going to wipe down the exposed sections of the forks before putting my new gaiters on, and wondered if plain old wd-40 would be good for this, or maybe something else to lube up the dried by not leaking dust seals?

 

[IrlMike]

Ok, great, let's see if I can answer your questions..


Now, I assume every setup is a compromise, as traveling with luggage or a passenger is going to alter everything. The article stated to set it up with the rider and his gear on board, so this is my plan. To accomplish this, I measure the available travel of the fork, then try and set it so it settles one third of this distance with me on board. Is this correct?

Yes to all. But after checking, I've remembered the front fork travel on Tbirds etc is 150mm, not 120mm. (Sorry about that. I lost lots of info I'd saved when my PC hard drive failed 2mths ago - still having to find stuff again.) Tho' with that much travel, anywhere between 45 to 50mm sag is likely a good place to start. Don't forget to average out sag measurements for the effect of fork 'stiction'.

Also, is the travel range of the fork what I can move with it empty and dry

Yes. Oil & Spring just modulate its' rate.

You mention the pvc wall thickness having an impact on the oil level. If I measure fully extended with all parts inside and use Jim's 120mm will it compensate for this?

As Jim uses the fork extended/springs in method (IIRC) it's hard to translate that level to one using the 'Haynes' method. I tried Jim's setting some time ago & it was way too stiff for me - the air gap was clearly becoming a 'spring'. (No disrespect for Jims way of doing things - riding/road conditions & rider preferences play a big part here. Just didn't work with my situation & way of dealing with our pretty compromised stock fork set up.) So, the balance of things for me tips me toward approaching oil level by the 'stock' method & working from there.

If your PVC pipe is of similar dimensions to mine (above) I suggest you compensate at the rate of 35mm level (reduction) for every 90mm length of pipe - shouldn't be too far out. (The spacers won't probably be emersed in oil, unless your new springs are a lot shorter than the stockers.)

I guess I'll begin by cutting the spacers flush, and then measure the presag and sag once it is back together. I can always add additional flatwashers to take up more space, or cut new pvc spacers with the forks mounted.

It all depends on how much length difference there is in the springs. If the new ones are a lot shorter & your new spacers are of similar length to the stockers, your air gap above a (stock) oil level will reduce significantly. So the air volume is then in danger of becoming a significant part of the 'springing' & will complicate things horribly.

D'you see? You don't want to be trying to set sag with what amounts to two springs - one metal, reasonably linear (over the initial range over of 'sag' movement) & not affected by oil level - & one of air that is horribly non-linear & greatly affected by oil level near a critical, rather unknown point.

I was also going to wipe down the exposed sections of the forks before putting my new gaiters on, and wondered if plain old wd-40 would be good for this, or maybe something else to lube up the dried by not leaking dust seals?

I would just use some fork oil - you know it's compatible with the seal materials etc.

I can say that playing around with the adjustments on the zx-11 shock were very noticeable, and at the extremes made the ride either way too harsh or bouncy like a car with worn out struts.

If it's similar to my ZX9 shock (& I think this generally applies..) you want to start at the low end of the compression settings to allow the spring to move up nicely over bumps & let the spring give you compliance. Start with rebound damping at the high end to control 'bounce' - control the energy built up in the spring (under compression) as it extends back. (IIRC mine is set 5 clicks (of 20) up from LOW for compression & pos 3 (of 4) towards HIGH on rebound - works very well.)

If, on the front forks, you still find you have plenty of compliance ('soft') for your usual riding conditions, roads, & ride preferences, adding some more damping (by 1 grade heavier oil, say) should futher improve control during brake dive. A high Viscosity Index (likely synthetic) oil will reduce damping rate variation with temperature & can only help with the already less than ideal situation of very non-linear type of fork/damper construction. Maybe worth a few extra bucks? I'm going to use Silkolene PRO RSF 10W next. (It actually it's 'base' viscosity the same as 'normal' 15W oil - they don't make it easy for us!)

This is the crux of my situation in Ireland - I need near motocross compliance, but also must have things stiff enough for good suspension control whilst braking (& to an extent high speed, 90+mph, stability).

This is where the Racetech emulators come in. I get nice linear, adjustable, compression damping (they don't affect rebound at all). And can set compression & rebound damping independently (via oil grade) - albeit by a rather lengthy trial & error process. I'm only just getting to grips with this after removing the usually detrimental complications & interactions (front/rear) of the rear shock. But you may well not feel the need to go this way to get something quite acceptable for your situation.

Cheers
Mike

 

[ssevy]

Mike,
Again, many thanks for all of the time you have invested in my education! My understanding of the interactions of the various parts of the fork are much clearer. I actually spent some time mulling over the oil level issue last night after reviewing all of the posts, and had a thought. If I reassemble the forks using all of the original parts according to the manual to the point of actually screwing the cap back on, and then measure the actual oil level with the forks extended, couldn't I then just duplicate this same volume of air with the replacement parts swapped in? I can do the math well enough, as I would just need to determine the volume of air in the initial setup, and then factor in the additional wall thickness and length. Based upon your information, it sounds like the oil has two functions, one, to circulate through the lower fork damping system, and two, to establish the volume of air inside the fork which is the air gap. Rather than make the oil level the same in both setups, it seems logical to make the air volume the same. Your estimates of how to compensate oil level according to spacer length seem to pursue this.
I bought Amsoil medium weight fork oil to try, and it is fully synthetic, and a bit heavier than stock, so I think I am okay there. My wife made me leave the garage door open, because the drain pan full of the old stinks so much! It smells sort of like old differential fluid, with a dash of armpit thrown in for good measure
Again, I truly appreciate the time you have spent on this.

 

[IrlMike]

Great stuff, ssevy, you have the principles right there (as I understand them) & the Amsoil sounds a good go. I don't have a VI figure for it but the synthetics are usually the ones to have better characteristics.

I guess if (before assembly) you add oil, measure the level (air gap) forks compressed, no springs, then extend & add springs you'll know what 'extended method' level is equivalent to the stock setting. Do share that with us, it will be interesting to know. Without a centre stand & with forks in place, the 'compressed' method is more difficult to do & that figure will doubtless help, if folks find the extended method preferable. (So long as the spring volume doesn't skew things too much.)

Cheers
Mike

 

[IrlMike]

'Level', of course is always the distance from the top of the fork tube, just to make sure other readers definitely know what we mean.

Mike

 

[jimmyj900]

ssevy, you've probably noticed that this is a controversial subject. That's because most of the folks commenting haven't actually thought about it in depth. (Makes this subject rather like politics, doesn't it?)

So here are some notes and observations:

The figure of 120mm airspace and the spacer length I gave is for the suspension as *I* like it -- rather stiffer than most riders would be happy with -- but feel free to play with the oil level and spacer length if it's too stiff for you. (A turkey baster can be useful for more than politically correct insemination.)

A few folks on this forum have whined about the stock rear suspension being 'too stiff'. My experience is that it's about right (when adjusted properly) and the front suspension is way too soft.

Personal preference -- if I wanted to ride a comfy chair, I'd do that at home in front of the TV.

------------------------------------
The pressure in the forks at compression is determined by how much the airspace is reduced, and compressing the forks 2.35" with a 4.7" (120mm) airspace will produce a pressure of 29.4 PSIA which is twice the atmospheric pressure OR a whopping 14.7 PSI over normal air pressure. (I'd definately worry about that pressure if my fork inners were rusted junk!) Fork seals won't 'blow' even if you ram a curb hard enough to bend the forks and wheels.

I guess I should mention that some bikes used to be factory equipped tire valves in the top nuts so you could adjust the rate of the airspace 'spring'. I don't know if that's done anymore, but it was a useful suspension tuning option. (Unfortunately it required some understanding of the system to use it intelligently, so I doubt it's anything but a race option now.)

-----------------------------------
The object of installing progressive springs is to cure the excessive dive at braking. If I remember correctly, that was a very soft 3" or more on my Adventurer. With the current setup that's under 2"and a lot stiffer. Sag is a bit less now, at about 1" total with me seated but there's only about 3/4" of preload versus the stock springs 3" preload.

Back to airspace.... With 2" of compression at full braking and a 4.7" airspace, the air pressure will be less than 7psi over normal air pressure.

---------------------------------------------------
Here's the information on a stock fork tube that I measured this morning:

16.5" = full extension of tube above dust seal
11.0" = max compression length of tube above dust seal

Subtracting, we get a max travel for the tube of 5.5"

With the spring removed and the tube fully extended, air space is 10" (254mm)
With the spring removed and the tube fully compressed, air space is 5" (127mm)

The Triumph Shop Manual says 150mm travel. (overstated by almost 1/2")

-----------------------------------------------------
When you pull the caps on the fork tubes, you're going to find that there's around 3" of preload with the stock springs. Expect the caps to go ballistic if they have the opportunity. Keep pressure on them as you back them out -- if you don't you'll rip the last couple of threads off the nuts when they come loose.

If I recall correctly, there's considerably more preload force (stock) than required with the Progressive Suspension springs.

---------------------------------
Suspension damping is strictly a matter of the viscosity of the oil and the diameter of the orifice(s) that the oil moves through when the fork is extended or compressed. The rate of the spring has no bearing on damping so increasing damping requires increasing the viscosity of the oil.

-------------------------------
The overall spring rate of the front suspension is a combination of the individual rates of the spring, the airspace and the static tire pressure and volume. You need to balance all three in order to get suspension working properly and give you the ride and control you want, so expect to spend some time on this.

For example, when I increased my front tire pressure to 36 psi and raised the forks a half inch, the ride got a bit harsher than I like. So I cut down the spacers 1/8" and tried it out. I wasn't getting enough road feel, so I added a fender washer to the spacer stack and it's just where I want it now.


Jim

 

[ssevy]

Jim,
I wondered if you might be joining in eventually. My thanks to you for the info from past posts and from this one as well. This topic seems tame compared to which oil to use, but I think that is because of the complexity of the issue.

Many folks post for a quick answer and then just go and do what is advised, but I am cursed with an inquisitive mind, and so as this thread so clearly exhibits, I want to understand the "why" as much as the "how".

Your comments about pressure and the safety of the margins (psi)based upon your oil level are interesting. I will not pretend to understand the way the air volume and the springs all interact to create the effect that they do, but I am clear enough to proceed with the fork rebuild.

Your comments do bring to mind a few questions, if I may:

Why are you setting the sag at only 1" with you on board? Doesn't this restrict the fork staying on the road when you go over a bump, as you only have an inch for it to extend?

Is my thought regarding maintaining the same volume of air that I mentioned in the earlier post reasonable? In other words, is the air gap the critical variable which should be considered, or am I fine using my very first post as a starting point (which was essentially my understanding of your earlier thread)?

Based upon all of the old fork/suspension threads, I thought this was going to be an easy upgrade, but it has become much more complex, and I accept that any setting will just be a starting point, and I'll have to ride it to tweak it. Makes me wonder how the guys who send their forks out to Race Tech or any other company for a rebuild get them back properly set to their unique needs?

Well, at least this information will be available for future folks to dig into, and that's what this forum is all about.