[FLUX] Lad.... strangely enough, my local Triumph dealership here in SF has a set that they had made as a test... billet aluminium, for sale at $59.00 US... They can have them made in almost any length needed. I almost bought them for my Bike since it is oing to be track only next year. My debate is whether to try them (they are cheap enough not to matter) or whether to try the Ohlins/Penske rear shock route, or BOTH...

What do you think?

I could try to get a picture and some specs from Munroe Motors the next time I'm down there...

:thumbup:

P.S. my Stator is fried.... waiting for a replacement.

 

Thanks ggillies. I had figured that someone else out there must've been thinking down the same lines.

I'd say to do both. As in, shock + linkage plates. The reason being is that even if you change the rear shock to a quality item, it's still going to have to work hard to soften the rate's action out. Better to get the action sorted first, IMO, and on this project 675 that I've just bought, that's what I intend to try first.

So yeah, I'm definitely interested in those plates mate. Some details on the specs of them would be handy, otherwise I've got some local machine shop guys here who could make me up a few different sets to try out.

Will try to get the trig done for it in the next 24hrs to get a good idea of the required added length needed.

 

I have the Aella Casuno low down plates I did this cause Im short 5'5" I see you have STOCK spring change it out for a race tech one for your weight it helped ALOT with the harshness of the rear

http://www.triumph675.net/forum/showthread.php/aella-lowering-plates-w-25161.html?t=25161

 

It's also on the list of things to do for me...

If you get something worked out, I'd be interested to see what you come up with...(but I'll still end up doing the math myself)

And you don't need to alter the shock to swingarm distances (that would alter spring rate overall), but only the dogbone length and relative position of the dogbone pivot (on triangle) if you want to maintain the ride height.

Or longer dogbone and ride height adjustable shock for a "quick fix"

 

A longer dogbone would be the other option, but the issue with that is that it will alter your ride height, so yes, you would need to then use a ride height adjustable shock.

Thing is though is that lengthening the dogbone will also alter the spring rate, so I'm unsure where you're going with that one if you believe that by lengthening the dogbone that the rising rate will remain the same. It won't.

So, the very issue here is to alter the rising rate. The problem is that it is too harsh and rises too quickly. That IS the issue that needs to be fixed.

Just got done with all my math. Dug into ye olde trig from days of yore, and some quick application of Perl to simulate the 675's rear suspension action.

In summary, from full extension to full compression the spring rate rises about 2.3x. ie. you have to push 2.3x as hard to compress the rear by 1mm when its (almost) fully compressed as opposed to when it's fully extended. There's a nice gentle rising rate plateau for about the first half of the swingarm movement range, and then it starts to asymptote up strongly in the second half of the range, which is what gives it its harshness, and why it seems to ride better if you give it plenty of preload to try to keep it in the upper half of the travel.

On the triangle, the distance from the swingarm pivot to the dogbone pivot is 72mm as stock. The distance from the dogbone pivot to the shock pivot is 66mm.

From what I'm working out with the suspension calculator I wrote, I'm thinking that with the same stock dogbone length, these two triangle distances need to both be increased by around 5mm for a good compromise. A 3mm increase would still be a touch harsh, and a 7mm increase would suit lighter riders and/or deal with bumpy roads better.

I know it reduces the spring rate, but that's the point. I don't reckon even a 230lb rider with gear could bottom out the rear even if they used the pillion seat as a trampoline. It just gets too harsh/stiff before it gets that far.

 

Anyone messed around with anything like this before? Experiences?

hmmm VERY interesting read.

Ive lengthened my dogbone as you might know (by 1.25"), because I WANTED to alter the ride height (make it shorter). What it did do though was soften the suspension (by pulling the spring out), so it then required an increase in preload (which again increases the ride height slightly). What it did was force the spring into the more subtle part of its travel, but I agree that it also diminishes the range of motion somewhat.

OK so to maintain ride height AND set the spring up so it doesn't need all that preload you'd just have to either put a stiffer spring in...

OR

If you were to make the triangle 'taller' though, wouldn't you be decreasing the spring's range of motion during compression- because you'd have less leverage?

P.S. I didnt even know you can get custom triangles!! This might be a better way for those of us actual wanting some ride-height reduction...

Here's a pic of my lowered setup- notice the angle between the dogbone and the triangle is less than the stock setup. Sorry if this just confuses things.

 

Flux , i saw a set of plates on ebay the other day , it was from a german seller and once i looked i lost interest as i dont spruken de deutsch. they looked a little odd so i thought they may be playing with ride height for all those suffering from ducks diesease . i ll try to find the seller again and try to translate to get an idea of what they were for.


p.s. your street naked bike looks great , great starting point i mean

 

i found it flux http://cgi.ebay.com.au/Heckhoeherle...le?hash=item350124655299&_trksid=p3286.c0.m14&_trkparms=66:3|65:1|39:1|240:1318

it is a set of triangles i guess to lower the bike 25mm (1 inch). not a bad price ??? cough . local engineer could knock some out of aluminum cheaper i reckon.

p.s. if your street tripling the new red addition i saw a second had striple loom on ebay , but it was in italy , may save a shitload of wiring mods just ask canyondancer if he has any hair left ????

 

Thanks for that Tim. Am not really interested in anything that raises or lowers the ride height though.

For purposes of clarification, let's apply some labels to the triangle distances we're talking about here. All distances are center-of-hole distances.

A = distance between shock pivot and swingarm pivot.
B = distance between shock pivot, and dogbone pivot
C = distance between dogbone pivot, and swingarm pivot

The stock distances are: A = 69mm, B = 66mm, C = 72mm

Assuming that we leave the dogbone length alone.

If we want to lower the ride height but leave the spring rate alone, we would decrease B and lengthen A to compensate. C is left alone.

If we want to increase the ride height, but keep the same spring rate, we would increase B, and decrease A minorly to compensate (to keep the shock moving along the same path)

If we want to decrease the rising rate, but keep the same ride height, we keep A constant, and increase C. B is increased too, by as much as is required to ensure that the shock remains at the same height. Due to the decreased spring rate though, some preload may need to be added to compensate, but the overall spring rate will be more supple.

Thinking on it more, and analysing the rate ratios, it looks to me like an ideal sort of linkage plate would be:

A = 69mm
B = 73mm
C = 79mm

That should keep the ride height about the same, without needing to add more preload (or maybe just a small amount). That will also give about an extra 15mm of swingarm travel before the action starts to rise rapidly again, with the action in the main working range being more supple.

I reckon that'd go a long, long way to fixing the rear action issues for most users, and heck, even for the race-track. Racers will just choose rear spring rates as they require, but even they would still appreciate a more supple rising rate response, rather than being kicked off bumps.

 

Just to update on this. I've dropped off plans with some machinists I know, and will be getting 3 pairs of linkage plates made up as per the specs above.

Plates are being cut from 4mm thick 6061-T6 billet aluminium plate (not the extruded crap), which is what is used on the bike as stock, and is what almost all aftermarket shock absorbers are made from.

Should have the first prototype plates back to me before end of next week. I'll be using a set, will be giving a set to a mate to test, and I'm looking for at least one other (brave & keen) person willing to install them and set up their suspension correctly (ie. ensure that the rear rider preload is set correctly after fitting) and provide some feedback as to how the plates affect the rear suspension.

Any one willing to volunteer? Naturally a disclaimer applies here. While the 6061-T6 billet mechanically has more than enough tensile strength deal with the stresses of the suspension action, I cannot of course offer a 100% guarantee of that. This is something that you'd be doing yourself with eyes wide open and full and sole acceptance of the responsibility for the use of the plates.

 

I'd be interested in trying them out.

 

Am happy to ship them to you free of charge, but I really do need you to assure me that you'll try them quick(ish) and provide some feedback on them.

I'll first try them out myself and send over some installation instructions and recommended settings (just in case something needs to be tweaked).

If you're still keen and agree to the above, then PM me your address and I'll have them on their way to you by mid-Dec.

 

hey man Im sorry didnt get it done last weekend some things came up my, rad hose still drips a tiny bit I WILL measure the AELLA's this Saturday for you man

 

Thanks for the offer (since mine got sresssed by bad installation), I sent you a PM.

 

Inspired by FLUX I fired up SolidWorks this morning and drew this.


Then I wandered down to my shed. (the workshop I run prototyping biomecanical research equipment)


After a bit of searching I found a bit of 0.190"(4.8mm) 6061-T651 plate and did a bit of machining


A couple of hours later including coffee breaks I wound up with these. (crappy phone camera pic in low light) couldn't be buggered doing the fancy radii shown in the drawing


Will bolt them on tomorrow and see how they go, from an initial quick laying the new plates over the OEM ones it looks like the the spring will have to backed off a fair amount to retain sag and ride height,
I'm still running the stock shock, hopefully this will make the back end more compliant.

 

Good work BZ. I'm hoping I get my plates from my machinists tomorrow.

You won't need to back off the spring preload at all. If anything, you may need to add 1/8 turn of preload. Bit unsure. I tried to get it right, but that was fairly hard to calculate/estimate as the rising rate is altered slightly.

The reason why is because the dogbone-SA length is longer too, so even though the dogbone-shock length is increased, it's increased by just enough to compensate for the dogbone pivot naturally sitting lower down (towards the ground), plus a small correctional extra to compensate for the slightly reduced linkage rate. I reckon I'm within 2mm or so of being right with it perhaps erring on the lower side, which is basically a 1/8-1/4 added preload turn to fix.

 

Put my new plates on today,
The needle roller bearings in the pivot points all needed greasing as they were virtually dry from the factory.
With the spring the same as before the ride height went up 10mm as I measure it (swingarm pickup bobbin center to the rear hole where the pillion foot pegs were) but the static sag seemed to be more,
about 15mm, it used to be about 5mm, wound the spring preload back about 3/4 of a turn to get ~30mm sag with rider mounted. This brought the rrh back to 3mm less than original.
I don't have an aftermarket shock so I don't have the choice of independently setting the spring preload and ride height

I've only rode the bike round my suburban test "track" so far but the rear end defiantly feels more planted, bumps and pot holes no longer kick my arse off the seat, in fact I was deliberately riding over
every bump I could find. Need to do more setting up but I don't ride the Putty rd or the old rd on the weekend to many people including cops.

Great idea FLUX you should start selling these plates

 

Put my new plates on today,
The needle roller bearings in the pivot points all needed greasing as they were virtually dry from the factory.
With the spring the same as before the ride height went up 10mm as I measure it (swingarm pickup bobbin center to the rear hole where the pillion foot pegs were) but the static sag seemed to be more,
about 15mm, it used to be about 5mm, wound the spring preload back about 3/4 of a turn to get ~30mm sag with rider mounted. This brought the rrh back to 3mm less than original.
I don't have an aftermarket shock so I don't have the choice of independently setting the spring preload and ride height

I've only rode the bike round my suburban test "track" so far but the rear end defiantly feels more planted, bumps and pot holes no longer kick my arse off the seat, in fact I was deliberately riding over
every bump I could find. Need to do more setting up but I don't ride the Putty rd or the old rd on the weekend to many people including cops.

Great idea FLUX you should start selling these plates

Yer a legend!
Im VERY interested in the development of these plates.
Im even more happy its being dev't by Aussies
Low shipping cost yay!
I was gonna buy a 3rd linkage plate for mine (extra strength) cause mine got bent recently..

They're only US$19 each but Bikebandit wanted another US$80 to ship them.

 

I'd be happy to give these a shot also, I do however have a much lighter than stock rear Eibach spring...

Also if the plans all match up between both of you and can be e-mailed to me I can check if my machinist can make a set on his cnc machine for me to try out and that would be a quicker easier way for me to provide feedback...

edit: And in case there is concern, no, I wouldn't have more made and try to sell them from under you guys... Simply if I can help I'd be happy too

 

Thanks for the feedback guys. I'll continue to work on the specs and refine it so the ride height and sags work out right without having to fiddle. Ideally I'd like to get these to a point where we can just drop them in place, and ride away without fiddling, and fix the kicking issues all with the stock shock unit still fitted.

I feel that if we get that right, then that'll make any aftermarket shock action that much better, as the rider is no longer having to tune it for a compromise. With the aftermarket 3-way shock on my black bike, I need to have it set with a softer spring than stock, low-preload, slow-compression set a bit hard, and fast-compression set soft. This, I feel, is really just band-aiding around the issue of the stock plate's rising rate. Ideally we shouldn't be needing to build our shocks around the flaws in the rear suspension action, but that's what we're having to do at the moment.

Get the rear linkage action working right first, and then we can get to really enjoying the bike with the stock shock, or reaping the full benefits of an aftermarket shock rather than compromising as much.

 

according to you, the kicking action of the rear end is all due to the rapid rising rate of the plates. However doesnt the stiff spring that comes with the stock shock also contributes to this kicking action?? So would using these plates fix the kicking problem altogether, or would you still need to get an aftermarket shock or correct spring weight to completely rid the bike of the kicking action?

 

The stiffness of the stock spring does contribute a bit, but the fact that we can largely "tune out" the tendency to kick by raising the preload (reducing the rider sag) largely points to the main culprit being the rising linkage rate.

Reducing the spring rate, as many do with aftermarket shocks, is one solution. That however tends to make the rear a bit soft in the normal part of the range, for which the damping needs to be stiffened up to control. It all becomes a bit of a compromise.

By lengthening the linkage plates the rising rate is pushed further back along the hyperbolic curve, which gives us a corresponding equivalent softening in the perceived spring rate.

The way it was as stock, a heavier rider would tend to compress the spring more over a bump, and cause the kicking action. A lighter rider would just get kicked out due to the stiffness of the spring. The longer plates soften the spring rate enough such that the lighter rider will no longer get kicked, and the heavier rider, with a bit of added preload (once we work out the final dimensions of the plates), won't be kicked out either 'cos the linkage rate is rising less.

Seems to me that the stock linkage was designed for minimal rear compression on a fairly smooth race track. Great for smooth tracks. Not so great for everywhere else.

 

hmmm....thanks for the explanation, almost sounds like i should try these plates out before going to the aftermarket shock, but Vlad is offering such a good deal lol.

 

this lighter rider could use some help. I almost lost the bike due to a bump right at the apex of a big sweeper. I have never felt the bike react in such a violent way....
I would be interested in some, since this would be a low $$ upgrade that would enhance the riding experience.
I applaud all those who's experimentation will benefit us all.
Definitely not selfish folks here.:cool2:

 

Eden, the GB deal is gone, you are one week late

 

na Vlad said John from Elka is offering the deal until the end of the year.

 

Time for an update. I finally got the plates and fitted them to the bike.

First off, I suspect that Baba Zanetti above may have installed his plates incorrectly given his stated observations, or has different dimensions to what I originally stated. What I saw and measured was completely different to he was seeing.

First off a bit of preamble on the effects of reducing the rising rate. This also has the side effect of increasing the total swinging range of the rear wheel. It will top out a bit higher, and it will be able to compress a little further. In essence the plates grant about an extra 15mm of total swinging range, so the rear wheel arc goes from a 130mm range to about a 145mm range.

So with the stock shock unit and the stock linkage plates, and measuring from the axle to a fixed point on the ducktail:

Topped out: 580mm
Static sag: 570mm
Rider sag: 546mm

With the plates installed, but no adjustment to the shock unit at all:

Topped out: 591mm
Static sag: 571mm
Rider sag: 545mm

Here we can see the effects of the extended range that's adding to our top-out range, and also the effects of the softened spring rate due to the extra 2mm of compression between static and rider sag.

Actually these values tell me that I'd gotten my initial math for the plate dimensions pretty much spot on. They are a true drop-in replacement that leaves the bike at pretty much the same ride height when the rider is aboard.

The most important value above though is the rider sag. We want that value to be the same as before because that dictates the basic geometry of the bike when riding. As I had suggested earlier in this thread, I added 1/8th of a turn of preload and this brought the rider sag to bang on what it was before.

Too the bike out for a ride up one of the local tight and bumpy scratching roads and was immediately impressed on the way there. A number of quite harsh bumps on the way no longer kicked me out of the seat, and the bike was better controlled, especially over crests and rises with the additional top-out range on offer. I think the shock definitely needs an additional click of rebound damping though, and perhaps an extra click of compression. Seemed to take a fraction longer to settle after a mid-corner bump than before like it's extended a fraction too quickly, which is again to be expected due to the linkage changes. The same movement in the swingarm now moves the shock plunger a lesser distance, effectively reducing the damping rate, so adding some extra damping to taste may be required. I'm still not 100% convinced that it needs it (damping adjustment), it just feels different and much smoother than before.

Getting into the gnarly tight and bumpy stuff I was impressed at how much easier it was to stay on the gas through bumpier sections. Before the rear would hop and skip off the road over bumps, but now it tracked the road completely. Sure, can still feel the bumps and the rear end working hard, but it offered so much more control and feel. I reckon I went through the section perhaps as fast as I've ever done, but with a lot less effort and wrestling. Still felt a fraction loose after some nasty mid-corner bumps, so as above, perhaps need an extra click of rebound.

Overall I deem this experiment to be a total success. I would make the following tweaks to the original design to prevent the need for any rider sag adjustment at all:

A = distance between shock pivot and swingarm pivot.
B = distance between shock pivot, and dogbone pivot
C = distance between dogbone pivot, and swingarm pivot

A = 69mm
B = 74mm
C = 79mm

Increasing B to 74mm (was 73mm in my original spec) will ensure that the shock preload doesn't even need to be adjusted to give the exact same ride height (with the rider aboard) as with the stock plates. ie. a true drop-in replacement.

Altering the rear ride height for shorter riders would then be a snap by just subtracting from B. If B was 64mm, then the rear ride height will go down by 10mm, but the action would start to stiffen up, unless we increased C, and then adjusted B again to compensate.

Running the math, for every 7mm we want to reduce the ride height by, we'd decrease B by 8mm, and increase C by 1mm. It's conceivable that plates could be made up that offer stock ride height, -7mm, -14mm and -21mm easily. Could probably do -28mm as well, but you'd be compromising ground clearance quite heavily by then, not to mention that the bike will not sit as stable on its side-stand any longer.

Am happy that this little experiment has turned out well.

 

Time for an update. I finally got the plates and fitted them to the bike.
First off, I suspect that Baba Zanetti above may have installed his plates incorrectly given his stated observations, or has different dimensions to what I originally stated. What I saw and measured was completely different to he was seeing.

Glad you finally got your plates back from the machinist, must of had a long Christmas break
In reply to your critique, and a few questions
The plates are in correctly, stamped adjacent to holes with a letter punch for identification as work progressed
Dimensions were as stated in you first post,

A = 69mm
B = 73mm
C = 79mm

parts were machined on a vertical mill with new digital readout which was calibrated to NATA 3 months ago so max error in positional accuracy was less than 0.005mm
( I've been a fitter machinist / tool maker for the last 25 years so I think I got it right :wink

Question 1.
When you got your plates machined (on a CNC machine I assume) did you ask for clearance holes to suit 10mm bolt because ISO medium tolerance (usually what you get if your using Cam-Works et-al)
is 11.0mm~11.27mm even with ISO close tolerance there could be up to 1mm difference between assembled center to center distance, probably more as the bolt shanks were 9.85mm as I measured them.

I used a tolerance of 10.1 for the pivot holes and measured my ride height and sag from a different point which could account for the difference.
also I was on my own so accurate measurement of anything but static sag is hard.

Question 2.
You reinstalled the stock shock for your ride test? with the spring at the original preload?
I'm still running the oem shock with preload backed off 3/4 turn to suit my weight (80kg) which also would contribute to our measured differences.
(from the BOTM you had a Wilburs (sp?) then bought a Elka 3 way from the recent group buy which I had to drop out from due to the Aus$ crash)

A number of quite harsh bumps on the way no longer kicked me out of the seat, and the bike was better controlled.... I was impressed at how much easier it was to stay on the gas through bumpier sections. Before the rear would hop and skip off the road over bumps.....but it offered so much more control and feel.

Well it's the end result which counts and I agree with you on the improved feel the modified linkages offer even with the original shock, before doing this I was always a bit conservative with accelerating hard out of corners
after an early incident hitting some ripples and have the back end skipout inducing a tank slapper with a related brown trouser moment.

Any chance of a graphic output from the program you used to calculate the different ratio?
Just got the latest COSMOSDesignSTAR suite to play with and want to run a finite element analysis on the plates.

 

Hi B-Z,

I wasn't intended to be critical of your skills as a machinist at all, but I was just postulating as to why the observed differences. My apologies if you've taken offence, none was intended at all.

To answer your questions.

Used a 10.1mm hole diameter (this was explicitly discussed with the machinists). When installing the plates, just before fully tightening, I observed very minimal free-play of the plates around the bolt hole diameter with the bolts installed.

Bike that I did my tests on is a stock Daytona 675, which is my new project bike, as opposed to my older BotY 675 (ie. I have 2 x 675's). Used the stock OEM shock on a stock bike with the stock exhaust system for all measurements, and the ride. I did not use the modified 675 with the 3-way Wilber's shock. The Elka shock is going on the new bike today for a ride test.

At present I weigh 89kg, so not a huge difference to yourself, and I don't feel that it's enough of a difference to warrant any major preload change to achieve the same rider sags before and after. The maths is saying that a lighter rider may even need less of a preload adjustment than I used (ie. would be closer to a no preload change drop-in replacement).

Still, thinking on what you stated that you've measured, it does seem to me like you may have accidentally gotten B & C swapped during installation on the bike. Doing that would indeed produce the results that you're seeing. Alternately whomever was taking the rider sag measurements that you weren't able to spot with your own eyes messed up? No offense intended here once again, am purely and unemotionally looking for an explanation as to why the observed difference.

For the final question, yes, stock OEM rear shock was installed for test ride. Preload was increased by 1/8th turn to give the same rider sag height as before the plates. Used an assistant to take the measurements. Was able to look at and verify the top-out and static sags myself. Only measurement I wasn't able to spot with my own two eyes was the rider sag, but given that my assistant got everything else right, and the bike feels like it's sitting the same with me on it now, I have no reason to believe that they messed up the rider sag measurements.

As for my program output, I was looking at it again last night to recalculate stuff. I want to re-write it again using a slightly different algorithm to see if I can't cross-verify the results across two different mathematical approaches to the same problem, just to be doubly sure that I've gotten it right. It does concern me greatly about our observed differences and you've gotten me spending quite a deal of extra time and double and triple cross-checks, both practical and theory, to be sure that I haven't somehow messed something up.

 

The other possibility here is that the stock spring rates of our respective bikes are significantly different, with B-Z's possibly being about 10% stiffer than mine. This may well be within standard factory OEM variation, and certainly given the built-to-a-budget OEM rear shocks, may not be that surprising?