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Rear suspension linkage plates - anyone modified them?

78K views 201 replies 82 participants last post by  MissedApex  
#1 · (Edited)
Edit: For those interested in these plates, there's a group buy for them here: *OPEN* GB #2: '06-'08 D675 Rear Suspension Correction and/or Ride Height Plates - Triumph675.Net Forums

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Talking about the triangular linkage plates (see attached image). The image is not taken from my bike btw.

I've often speculated that the 675's stock suspension action is too harsh, in that it rises too quickly.

For a quick explanation of what's going on, the swingarm, when the suspension is compressed, rises up. This effectively lengthens the distance between the dogbone mount point to the bike frame, and the top-triangle swingarm mount point. The pivot point between the dogbone and the triangle will move up. The further you compress the suspension, the faster it'll move up, effectively squeezing the rear spring even faster.

This is what makes the bike's rear suspension a rising rate system.

Now, the issue seems to be that you need to give a fair amount of pre-load to the 675 to get it to sit far enough down in the rising rate stroke to make the rear feel more compliant. This is exactly why we have that strange behavior with the 675's rear suspension. To actually make it feel softer to ride, you need to increase the preload. The problem with this of course is that in doing this, you're also eating into your top-out range. This reduces the rear suspension's ability to extend far enough to deal with going over rises well without the rear feeling all "wobbly", or even leaving the road when it normally shouldn't. In a nutshell, some top-out range is a good thing.

So, it would seem to me that the way to "fix" the 675's rear suspension issues would be to lengthen the distance between the two right-hand triangle pivots (the triangle-swingarm pivot, and the triangle-dogbone pivot). This will reduce the rate at which the suspension will rise. We would also need to lengthen the dogbone-triangle pivot and triangle-shock pivot distance correspondingly.

I need to pull out the ruler and do the proper trigonometry math, but it would appear that in leaving the top two triangle pivots alone, but dropping down the dogbone pivot about 2mm along the arc of the dogbone swing should be pretty close to what's needed to soften the action of the rear suspension without altering the ride height of the bike. This should allow for a wider range of supple action before the rate rises and becomes harsh near the top of the stroke.

Anyone messed around with anything like this before? Experiences?
 

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#100 ·
2009 model

Hi everyone

I have been following this thread with great interest. It seems that many people think there is a problem with the rear suspension on the Daytona. I am very impressed with the work done by Flux, he has come up with a simple and cost effective solution.

I have a 2009 Daytona, so in the interest of science I have measured up the linkage. I am assuming that the frame and swingarm are the same as the 2008 model but they could be different.
A= 69mm
B= 65mm
C= 72mm
Link= 146mm
Shock= 303mm
My bike has the same 4mm spacer on the upper shock mount. The shock is different but the spring looks the same, it has the same no of turns and the wire looks about the same size. The factory pre-load setting is the same as on the 2008 bike.

What`s it like to ride? I am 11.5 stone, for people living in the colonies thats 161lb and for people in the Eurozone it`s 73Kg. On factory settings it feels better and more compliant than the 2008 bike that I test rode. But there was nowhere near enough sag, front or back. The rear would top out under hard braking and the front would skip over bumps on the power. I reduced rear pre-load by one turn on the rings and front by one line. The bike is now more composed and the steering is nice and neutral but the rear suspension now feels harder and the bike gets kicked off line by bumps in the road. Reducing high speed compression does help but the bike is still too high at both ends, if I take out more pre-load then the back will get even harder.

Conclusions: The 2009 bike has the same problem as the old model, the only real difference is the shock. Triumph appear to have set the bike up to suit a heavy rider on a smooth track, It is not so good for a light rider on the road.

Slow-Lemon
 
#103 ·
TK, sag decreased by 11mm you say? Something very odd there. I had rider sag increase by 10mm with the stock shock, and 9mm with my aftermarket shock. Never, ever, had it decrease.

Grab a ruler and do a quick check and confirm that the swingarm to dogbone pivot distance (center to center of the bolts) is approx 79mm. That's the most important thing to get right. Also verify that the dogbone to shock pivot distance is 74mm.
 
#104 ·
So finally got a chance to fit the standard plates and go for a ride.

Ride Height

After putting the plates on, i had a ride height decrease of 7mm, so i had to add half a turn of preload to bring it back to within 1mm. Dont know if this is normal or not, but the Ohlin TR602 on the back may have something to do with it

The Ride

Took the bike through some crazy bummy road around newcastle, the back is alot more compliant and i was more comfortable going faster. It was still bummy, and i could feel the rear working hard. Nothing like the stock plates however, with the massive sit lauching. I still did get tiny sit lauches going over massive bums, so i may have to play with the rebound settings a little to see how that feels. Any ideas??

Thanks [flux] for all the work you have put into these plates :thumbsup:
 
#106 ·
Eden, I've talked to Zeno and he told me that he fitted you with a spring suited to ride Easter Creek fast, which will translate in really bad ride on the road. If you have any issues he's cool with giving you free adjustments. I'm bit picky, so I go to him for free adjustments anyway :rofl: Your spring is way too rough for road riding. Now my sprink in my Elka shock is perfect for road riding, but not hard enough for track...

I think if you ride roads you should see zeno again and tell him to tweak your suspension.
 
#105 ·
Thanks E-K, althought they're called bumps, not bums, unless you're riding a different kind of "bike". :biggrinjester::whistle:

Yeah, they won't transform the rear suspension into dirt-bike-like bump handling, but they will make it more compliant and smooth out bumps to be less harsh than they were before, just as you found. Can still launch the rear over crazy bumps.

The 7mm ride-height decrease after installation is "normal" in the sense that it doesn't surprise me, especially with an aftermarket shock. There's simply too many variables to get it right for every user's scenario. If adding half a turn of preload to return it to normal is what was needed, then you did exactly the right thing.

If you're wanting to handle crazy bumps even better, then backing off high-speed compression damping a touch (if you have that dial on your shock) otherwise backing off rebound one click, and maybe even adding 1/4 turn of preload to keep it even further up in the softer linkage rate range may help there. It's a compromise though. Soften the rear up too far and the bike will start to pitch and push the front coming into corners. No matter how much you tweak, at the end of the day you have to accept that there simply will be bumps that cannot be dialled out without losing out in other areas of bike stability, and so you've just got to bite the bullet. If I can see big bumps coming, I just support my weight on the pegs and keep my weight off the seat,

Thanks for the feedback mate. Appreciate it.
 
#110 ·
Ok i have a question (sorry if i may have missed the answer while skimming through this thread) has anyone who have installed FLUX's plates still have the stock shock and spring and how does it feel? Seem's like everyone here has an aftermarket shock with the plates...i would love to have an aftermarket shock but that is way down the line so the stockie is gonna have to do for now...thanks
 
#118 ·
Flux, have just read this post and am very impressed with what you have done. I am setting my bike up to race this year and will start the season with the standard rear shock. I am hoping to upgrade to a performance aftermarket shock as and when I can afford it. However I would like to fit and try your plates. I work for an engineering company who could easily make these plates. If possible could you PM me the diagram with drawings and dimensions etc....(any format is fine). I only the need the drawings for the same height plates. This will purely be for me and nobody else as I can save myself money by using material from work and a machinist. Thanks Chris
 
#119 · (Edited)
Hi binman,

There's an update to this. I took the new plates to the track on my bike. I push moderately quick myself (mid-pack, fast group), but am horribly out of practise as it was only my second time at the track in three years.

While the plates were perfect for road use, at the track their added rear-end top-out was causing issues for the front end when front trail-braking aggressively into corners. The rear end was coming up too much causing the front end to want to fold. Mind you, this was also exacerbated by the too-soft fork springs I had fitted (0.90kg currently fitted for road use instead of the 0.95kg that I need for track use for me).

Still rambling with this, I also have a 675 street-fighter conversion bike for road use. One of the things I did with that bike was to have 10mm of fork gold showing above the triples, and put one of my 20mm drop plates in the rear. ie. the bike sits lower than stock, and the weight is more rear biased. Bike balance on the 675 fighter is sublime, whereas on the 675 sporty it always feels top-heavy, in part due to the forks being set flush, so it sits about 10mm higher than stock.

Due to this, in my experience the practise that many do (myself included on my sporty) of having 0mm fork gold showing above the triples to gain more front-end stability is the wrong thing to do. Keeping the forks at 7-10mm gold showing, and dropping the rear (meaning rear axle-ducktail distance) down by 15-20mm works MUCH better for overall bike balance.

So, what I've done for track use is this: I've designed a set of race-plates that drop the rear down by 25mm when first installed, but you HAVE TO compensate for this by increasing the rear preload, and in doing so, we get back to a more desirable top-out range. The reason for this is that the plates add to the top-out range, which is undesirable for track use. By making them lower, and jacking up the preload, this does two things:

1) Brings the linkage rate back into the more linear portion of the range
2) Reduces the top-out to more standard/acceptable levels for track use

I reduced the linkage length in these new plates to compensate for 1) above, so the action is stiffer than what my first generation plates provide, but still more supple than the stock plates. Basically a for track-use middle-ground.

I have the first cut of these new plates in my hand as of yesterday and will be installing them and testing them out in two weeks. I need to wait that long as my sporty bike is waiting on some parts and is in pieces at the moment.

I'll update with how that goes. I don't really want to give out specs and dimensions before I've tested it, and I don't really recommend the old modified plates for track use unless you're using the 10mm or 20mm drop plates and jacking up the preload. I can provide you with the old 10/20mm drop plate specs if you like, and you're in a hurry, otherwise I will likely be making a batch of these track-plates by end-March/early-April.
 
#127 · (Edited)
I also have a 675 street-fighter conversion bike for road use. One of the things I did with that bike was to have 10mm of fork gold showing above the triples, and put one of my 20mm drop plates in the rear. ie. the bike sits lower than stock, and the weight is more rear biased. Bike balance on the 675 fighter is sublime, whereas on the 675 sporty it always feels top-heavy, in part due to the forks being set flush, so it sits about 10mm higher than stock.

Due to this, in my experience the practise that many do (myself included on my sporty) of having 0mm fork gold showing above the triples to gain more front-end stability is the wrong thing to do. Keeping the forks at 7-10mm gold showing, and dropping the rear (meaning rear axle-ducktail distance) down by 15-20mm works MUCH better for overall bike balance.
Just wanted to add a data point here - I have a set of the plates, and waffled over which ones to get when Flux did these up originally. I chose -10's first, but the batch had issues and ended up going with -20's instead the second time around, figuring I could get an adjustable Soupy's link done up to tweak it +/- from there if needed. Dropped the front so I had 10mm gold showing and much preferred the resulting balance. Was still playing with fork height when Winter settled in. Running 8mm showing right now, and liking what the lower CG and bit of added trail do for the bike. Had to crank the the preload down a bunch from stock with the plates, and have about 38mm loaded sag on the rear, with zero preload on the stock fork springs for my 160+/- in-gear lbs. Mine's been all for on-road use, and can see where Flux is going with his new, firmer track plates. Swingarm angle might be less than optimum for whacking it open on the edge of the tire on track, but on the road that's really not an issue, and clearance is still plentiful. Unless you're heavy, you'll run out of tire well before you drag anything.
 
#120 ·
Not to be an ass,

But what changed in the last week or so when you told me that I should get stock height plates for best cornering performance, and that you weren't making anymore so I was SOL.

^Looks like both statements were false.
 
#121 ·
Not to be an ass but, read the above post again.

"While the plates were perfect for road use, at the track their added rear-end top-out was causing issues for the front end when front trail-braking aggressively into corners."

There ya go chief. The original plates were designed for street use and I can personally attest that work very well to that purpose. The new plates he is making are probably only for his personal benefit on the track. He has no obligation to make the plates for others. But since he is generous and is NOT looking to make money on this he has posted his designs for all to take for FREE. If you want them that bad, go to a machine shop and have them made. But don't bitch at [FLUX].
 
#122 ·
Thanks SMB.

I had that track day on the 26th Jan. I'd observed some issues, and me being me with a problem to solve, wanted to solve it. On Saturday 6th of Feb if you must know, I'd decided to figure out what was going on, thought that maybe the plates had something to do with it, and sat down and designed some new plates to account for what I thought the issue might be.

When I went to my machinists on Monday the 8th of February, I was told by them that they're very likely to shut down by the end of March this year. I'm pretty shocked by this, it's a 30 year family business that's going under due to all manufacturing work being shipped off to China nowadays.

So, it became crunch time. I'd had a few racers ask me if the old plates would be good for track/race use. I wasn't wholly sure, but if I was going to do something about it, it would have to be really soon.

These plates that I'm getting made up will be stiffer than the old plates, and will not handle bumpy public roads as well. They'll be better than the stockers for public roads though.

TBH, I really don't enjoy taking orders and writing out forms and sending stuff overseas. It takes about 10 minutes of my time per plate set and I'm a busy family man.

Shit, I just thought that if I'm going to make a few new plates for myself that I'd suck up my selfish attitude about spending time mailing them out to people, and put it out there to determine if there was any interest in me making up a batch before my machinists fold and shut down.

So yes, something DID change in the last week mate. If you got your knickers in a twist over it, tough. Shit changes.
 
#123 ·
hey Flux,

Hate to take up anymore of your time....but could you send me the designs for the street plates you designed with stock height? email is wuzertheloser@gmail.com. I'm very interested in adding this to the bike as there's too many little bumps in the road where I ride. Still can't afford an aftermarket shock so I figure this is the next best upgrade :)

Thanks so much!
 
#124 · (Edited)
The MasterCam file for the plates is at the machinists. I just walked in with a set of dimensions that amounted to the following:

4.0-4.5mm thick 5083-H321 alloy plate. Can use 6061-T651 or 7075-T6, but hard anodising for corrosion resistance of those alloys is a must. 5083 has some fairly desirable properties and can be used bare, although I did get them Type II anodised for both looks and added protection.

10.0mm diameter holes
7.0mm of material around the holes (implies a 12.0mm radius of the outside curves)
18.0mm material width for the cross-beams between the holes

The hole distances are:
A = Distance from Shock Unit Pivot to Swing-Arm
B = Distance from Shock Unit Pivot to Dog-Bone
C = Distance from Dogbone to Swing-Arm

For the standard drop plates:
A = 69.5mm
B = 74.0mm
C = 79.0mm

For the 10mm drop plates:
A = 69.0mm
B = 69.0mm
C = 79.5mm

For the 20mm drop plates:
A = 70.0mm
B = 64.0mm
C = 80.0mm

For the 40mm drop plates
A = 70.5mm
B = 54.0mm
C = 81.0mm

Note that the above dimenions are all for the old plates. Not the newer track-based plates that I'm working on now. The reason that the 10mm distances is slightly difference to the standard/20/40mm progression sequence is the 10mm plate was refined after the first batch of std/20/40's.

So there ya go. I just went to a machine shop with those dimensions, took a stock plate in as an example, and said "make this please". They drew it up in MasterCam in under 10 minutes, using 3 circles to start with to find the intersection points to locate the hole centers, and then did a series of radius circles (5.0mm and 12.0mm radius) around the centers, tangential lines to define the straight edges between the holes, and 18mm parallels to generate the beams, a 3mm cutting radius on the internal triangle cut-out corners, and then cleaned up the un-needed lines. I was impressed with how quickly they drew it up. Easy to do if you want one.
 
#126 ·
So where are you at with the 'development'/production FLUX?

For 'spirited' street riding and occasional track use (with the stock shock for the moment) which of the above options would you recommend? You seem very happy with the lowered both ends (20mm rear, 7-10mm front) on the 'fighter - is that your preferred option? Have you come across any compromises as a result?

I don't think the track version would be the best for me, as I'm only a very occasional track day rider, and only new to the bike, but I'd love something that makes the rear more compliant on the road.

Is the current/next batch just going to be the track version, or were you getting some more street ones done as well? Either way i might grab a set for future use...

Very impressed, and grateful, for all the work you've put into this. I can mock up a CAD drawing using your dims and get a set machined, but the modelling and formulae you've been working with boggle my brain! And obviously it's easier for me if someone else is doing all the legwork!

Cheers mate!
 
#128 ·
I've fit the track plates and did some adjustments.

Right now I'm waiting to get some time to take the bike out. Should be able to within the next few days. Won't be at a track though, so I'll have to make do with one of the roads I like and give it a push (in safety).

Pretty big changes to the bike with what I've done. Before I had 0mm of gold showing, and the rear was still coming up too far and making the front too steep, and the whole bike felt top heavy.

The plates I'm trying now are somewhat radical. I've pushed the forks through to 11mm of gold showing (about the limit), and the rear-end has been dropped by 17mm, for a net 6mm drop at the rear. Actually, after plate installation the rear had been dropped by 25mm, but that was on purpose as I knew that I needed to add preload to get the rear rider sag back to normal levels. Rear rider sag is now at 30mm, before it was 45mm, so sag is where it should be again and should prevent the front-end pitching that was giving me grief at the track before.

All of those values are very close to what I had planned for, being within 2mm of what I was targetting, so I can refine the design and get it closer with the next set.

Basically, if I were going to make these plates, I'd offer them in 5mm and 15mm drops. What I've put on my bike was targetted as a 15mm drop (ended up being 17mm). The drop here is measured as net rear drop AFTER preload has been adjusted (I added 1.75 turns) to bring rider sag to 30mm.

A 15mm drop plate is what you'd use to experiment with either a lower CoM, like I'm doing at present, or allow you to run a 190 section rear tyre without the front getting too steep. A 5mm drop plate would allow you to run with the forks in the 0-5mm gold showing range while still setting the rear rider sag in the 25-30mm range for track use, and would be for those who like the bike with a higher CoM. The problem I also find with a higher CoM is that the bike both wheelies and stoppies a little too easy. A lower CoM really helps to keep both the front and rear on the ground more often.

As for ground clearance with the way I'm running it now, I'm using Sato rears, and have the pegs set back by 10mm, and up by 20mm. A quick inspection with a photo would suggest that the rear brake lever would touch down first on the right, and the left-side engine casing would hit first on the left, and we're talking at around 60-65 degrees of lean for either, so I don't think that's going to happen.

With stock pegs, just remove the hero knobs for track use, which will add about 12mm of peg clearance if grinding the pegs is an issue.
 
#129 ·
I didn't mean my question to sound dickish, I was honestly wanting to know what happened since I spoke to you last. Despite me "trying not to sound like an ass" it came out wrong.

I'm definitely watching your progress closely, and I'm pretty excited to see where it goes, unless I'm on your poo list now. Your data and methodical approach speaks for itself.
 
#130 · (Edited)
It's cool TD. You did come across as a bit snarky, but the internet can be like that. No dramas.

Well, I won't be doing any further testing for a while. Broke my left tibia yesterday when some old coot decided that it'd be a good thing to stand on the brakes mid-corner because RIGHT NOW would be a good time to do a U-turn. Was doing about 45mph, I was a couple of car lengths back, touched the brakes on a bumpy road mid-corner, and was on my arse so quickly that I'm still stunned about it. Bike (yes, the 2008 BotY bike) landed on my leg and broke the tibia.

Bike ain't so pretty now. Will likely need to get the leg pinned.

Lesson learned: When choosing whether or not to buzz by some old guy, DO NOT be polite and wait for a good opportunity. Buzz the fuckers asap before they get you!

Realistically, it's my fault and I accept that. Doesn't change the fact that it was a really shitty way to go down, ambling along and being brought undone by bumps when on the brakes.

Leg was sore. Picked up the bike and rode it home, which was one hour away. Parked the bike and wife came outside after 5 minutes to find me sitting on the ground 'cos I was unable to walk inside. Took me to hospital, and X-ray revealed a serious break in the lower tibia. In a cast for now pending specialist attention.

Shit happens I guess. Could've been worse. Will be out of action for 12-13 weeks.
 
#131 ·
Shit happens I guess. Could've been worse. Will be out of action for 12-13 weeks.
Sh1t [FLUX] sorry to hear about that. Pretty scary stuff.
Hope the leg mends well and quickly.

I'm just around the corner from you, if you need a hand with anything give us a call.

Johnno.
 
#133 ·
Riding it home like that was HARD CORE :notworthy:

I know how that kind of crash goes, my first race in St. Louis I had an excursion on the back straight, on the brakes, in the bumps. Had NO IDEA what happened, but the front washed out so quick it was over. It didn't even lock up, it just left the building.

I got lucky though, was doing about 90mph, no injuries. Though I doubt I would have come out so pretty off the track.

That's a cryin' ass shame though. Hope your time off is reasonably productive. You had any thoughts about your next BotM?
 
#135 ·
Lucky it's only the leg... pin it, then back on the bike in only a few weeks like a pro:rofl2:

Sorry (yes, really) to hear about the crash. I was looking forward to the latest development of your plates.

Maybe you can be a pit bitch for a while and see how (SLOW) the other half rides. hoping to get down to the Island again in March and April so it won't be far from you.

Hopefully you get some special service from the missus... but not until she finishes with the lecture.

Chin up, there's now plenty of time to take the piss out of others while you plot you next attempt at world domination....
 
#136 ·
That's crap man, no-one deserves that. Stoopid old bastard.

Heal up quick, and get back on that awesome stealth weapon ASAP.

I'll be joining you on the rehab list soon - getting a knee reco revisited, hopefully just arthro and minor procedure.

Sorry to hear, hope you and the bike patch up OK.
 
#138 ·
Thanks for the well wishes guys. Really appreciate it.

Still half-spaced out on pain-killers here, so forgive any rambling.

As for the plates, well I did get some testing in, but I was planning on a track day on the 22nd of March to get a proper assessment at Phillip Island. That's not going to happen now, and I'm going to have to find new machinists if I'm going to get these done, which is now looking like towards September/October time-frame.

Overall, I was pretty happy with the new plate setup. It was definitely more firm than my original plates. The rear end wasn't as smooth over really bumpy stuff, and I have one corner with a huge dip in it that really stresses out the rear end on any bike I've ever ridden over it. With the old plates, you noticed that dip but without any serious jolting, and with the track plates, it gave a jolt but it was well damped and controlled. Still a lot better than stock though for which the bike almost leaped up over the rising edge of the dip and gave you a good thwack in the nuts for your trouble too.

On one of my favorite roads where the surface really is as good as, if not better, than many racetracks, the rear end was well controlled and the front was more "sure". The bike being lowered by around 15mm overall though, with a greater rear weight bias stopped the bike from feeling top heavy. Overall, it did remind me more of the classic Japanese style bike balance. I tried trail-braking deep into a couple of corners, but the road is not the racetrack so it's hard to do that with any real confidence, but my initial feeling was that my old issue of the front end wanted to fold had been mitigated, at least to the level that I was trying. Stiffer fork springs, which I have planned, should fix it fully.

Overall, I was very happy with the way that they turned out. I really would like to try them at the track for myself first though, before saying that I was happy with them.

In the meantime, keep your bikes rubber-side down, and I'll update with any development, which are likely to be slow for the next three months.

Cheers.