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Discussion Starter · #1 ·
I posted earlier when I joined the site to say hello. I have found a tremendous amount of useful info on here using the search function. I cannot find anything concerning my perticular problem. I bought a 98 bird that has been lowered. I didn't mind the ride until I went on a 3hr ride last week. On the roads that aren't so smooth, the ride was down right un-enjoyable. The bike just bounced and bounced. I was planning on putting it back to stock height. (I have long legs) But this ride put that at the top of my to do list. I looked at the triangle on the suspension. The PO told me that is where it was lowered and could be put back to stock height easily. I have searched and I know what needs to be done with a stock one. The triangle on my bike has 4 holes and I do not see any indication of what was the position for stock height. Does anyone know if this is aftermarket and how should I proceed??? Thanks for all the info so far. I cannot stress how dissapointed I was in the ride. After an hour into it I was tempted to go back home and ride my 88 hurricane 1000f instead.

Oh, the forks have not been lowered.
Thanks.
 

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On the triangle plate that the shock is bolted to there should be an arrow.
What direction is this arrow pointing in mate?
 

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Usually when something is lowered you do tend to sacrafice comfort for handling so a bumpy ride isnt uncommon in most situations to bike tends to feel the roads a little more for the shock being
compressed more than it should decreeses its opreration to absorb bumps,dont let that get you down once put back to normal height you will see the diff.
 

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Can you clarify something for us so we can help find a solution. In your title you say it is a "bumpy" ride, which may indicate a stiff suspension setup - but in your post you say it is a "bouncy" ride, which may indicate a soft setting. You could try removing and inspecting the triangle plates to work out correct orientation, return shock to correct settings for you (set sag, etc) and maybe set C/R damping settings to a midline point. If this is an improvement, then we may be on the right track. If not, your shock might be shagged - they don't last, relatively, all that long. You also mentioned that there are four holes in the triangle plate. Unfortunately I'm not at home to be able to check, but I thought there were only three holes in these plates. Hopefully the PO didn't follow in Teslacoil's footsteps and drill his own holes.
 

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Discussion Starter · #7 ·
thanks for asking for clarification Paul. The ride is bumpy, not bouncy...it doesn't feel like a worn out shock. The triangle appears to have 4 original holes. It doesn't appear to have been drilled by an amatuer.
 

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Could be too much preload. Also, have a look at the damping setting - it could be turned up too high. I find that it is a fine line between enough damping to keep the ass from bouncing in high-speed corners and having your teeth rattled from your head.
 

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Sorry to hijack this thread but just thought I would add my .02 since I am also a fairly new owner and have been trying to work out the ideal height for me. When I first got the bike, it was at stock height 32" seat height and the ride was fine. I just felt it was a little tall as I could barely flat foot it with legs stretched and wearing my combat boots. :) I then did the suspension plate (aka triangle) mod which lowered the bike 1". I think the bike was much better for me as I felt comfortable knowing that I could touch ground with both feet firmly planted at stop lights etc. Ride comfort and control did not diminish as far as I could tell.

I then lowered the fronts this past weekend about .5" (5/8" to be exact) which meant the bars were that much lower as well. I know that lowering the seat 1" and the bars slightly less than 1" should not result in too much more reach but that is how it felt. I also felt that the seat to peg shortened distance was more pronounced (less comfortable) after lowering the front, although I am not sure why. I want to add that I lowered the front since I read about the poor effects that changing the bike's geometry if I only lowered the back and not the front and so I wanted to get it back to oem as much as possible.

I have to say that the bike felt less comfortable than when the fronts were at their stock height and rear was lowered. There were other factors as it was much colder and much windier the day I rode it so I cannot tell for sure whether the ride was comparing apples to apples, but it certainly seemed harder to make those right turns (and I am not talking about severely sharp turns either... just regular run o' the mill turns). Colder weather also probably had some effect on tires which never seemed to have the grip I would like. I rode for about 70 miles hitting no higher than 80mph for short straights and much slower for the turns. And yes, the bike felt a bit bumpier since there is less compression when the front was lowered.

I will continue my search for seat/suspension nirvana for me, but will do so in as inexpensively as possible meaning I do not intend to get new shocks/springs. Those should be my constants although I realize that lowering does impact the travel of shocks/springs. The whole intent in starting to mod was to simply lower the seat height and not lose comfort and ride-ability/flickabilty (if the 500lb BB could ever be described as truly flickable). I am not an engineer but thinking about the points being made, I am not convinced that lowering the fronts are necessary to retain "optimal geometry". Would not a person's weight affect the sag/seat height differently from another who weighed less or more? I suspect that manufacturers opt for a geometry that accomodates the most number of folks given varying heights, weights, etc. So in effect the optimal set up from the factory is nothing more than the one with the least amount of concessions for the average rider. Thus, even if I lowered the rear and changed the stock wheelbase ever so slightly (I did not measure but I presume the mod lengthened the wheel base as that is what I think a dogbone link would do), I doubt that lowering the front is an absolute necessity.

All things being equal, I would think lengthening the wheel base and/or lowering the center of gravity (cog) would improve straight line stability. Conversely, shortening wheelbase and/or raising cog (e.g. 6mm shim mod) would improve turn ins. Again, each would depend on other factors (condition of shocks, weight of driver, etc). So I would try all different combinations and take note of your observations. Again, whatever feels right is what is right for you. I will try to ride my bike at its current lowered height a few more times (in warmer nicer weather) to make sure yesterday's ride was not an aberration, but if it still feels awkward, I will raise the front back up.
 

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OK lets start with the triangle plates

goodpizza said:
The triangle on my bike has 4 holes
Now are you referring to 4 mounting holes or just 4 holes?

If you are referring to holes then unless my maths is letting me down the std triangle plate does have 4 holes ......
Metal

This is a std plate and in the orientation that it should be in std ride height position with the annotation and arrow pointing forwards.
If your triangle plates do not look like this then they are
1 Non std.
2 Originals that have been hacked about.

The dimensions between the mounting holes as shown above are 78mm - across top 76mm top left to bottom 72mm bottom to top right.

My gut feeling is that the poor ride quality is due a lack of damping in the shock (std shocks don't last more than 20K miles here) but it should also be noted that even by turning the triangle plates you are changing the distance and/or accelleration of the shock internals so working the shock outside of its design range (trying to move too little/much oil in too quick/long time). This can have the effect of either giving too much damping or no damping at all .............. so you end riding on the shock spring only ................... which makes for an 'interesting' ride.

I would put the suspension back to normal, and then manually 'bump test' the shock to see if the rear end rises and settles in one movement and if not (several bounces or returns very quickly) try the adjuster (usually minimal usefulness!) and if the rear end is still bouncy look at a shock rebuild / replacement.

Sorry didn't change the background on the CAD box (hence black background) but these show the effect of the std triangle plate dimensions and what happens when you start changing dimensions - I needed hundreds of these when 'playing' with Ducks suspension!
 

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Resident Eh?hole.
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OMG. Teslacoil strikes again. Someone has gone and drilled another hole. :facepalm: The lower bolt needs to be run through that lower hole to restore ride height - the hole it is currently in should not exist.
 

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Discussion Starter · #13 ·
insert string of explicatives here...I was afraid that hole was drilled after closer inspection. Will it be safe you think to ride it like that?
 

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I'm afraid I don't have the background to answer that. The man to ask is TheDuck as he is an engineer (don't worry, he's okay, he is one of the rare ones who gets his hands dirty :)) who deals in stresses. He will likely be along shortly with a spread sheet and a CAD drawing. ;)
Personally, I would probably replace the triangles (because I ride like a jackass and would be worried about it letting go) even though there is likely nothing to worry about.
 

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OMG. Teslacoil strikes again.
that was exactly what I thought ................ but structurally there shouldn't be an issue with the mod if the triangle plates are left bolted through that new hole. I would not however run the plates with the 'dog bone' bolted back in its original location, I would change the plates before going there. (there is a good technical reason but I won't bore you with it!)

That said I would be checking the top face of the dog bone and the bottom of the shock to see if they have been or could make contact. As the swing arm moves from full droop to full bump the distance between the dog bone and shock bottom changes and if you increase / decrease ride height by a large amount as here there is a real chance of contact. A 'professional' lowering would almost certainly have involved changing the dog bone and shock angle to avoid this problem.

Having now seen the change I can now be certain that the shock will not be working as it should so if the damping is still good you won't be getting a good ride ....... which is where this thread started!

Personally I would bin the triangles now ...................

No spreadsheets, cad or FE needed here Shewie which is no doubt a bonus to us all! :smilebig:
 

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...And that, ladies and gentlemen, is why this site is so damned awesome.

(there is a good technical reason but I won't bore you with it!)
Why stop now? (ba dum bum) Come on, Pete, you had to know that one was coming. :) I think I can see the reason, but I actually enjoy your lessons so please let fly.

No spreadsheets, cad or FE needed here Shewie which is no doubt a bonus to us all! :smilebig:
I was counting on some kind of stress map showing how weak the area around the new hole would be if the bolt/bone was replaced to the original location. :eyebrows: I thought you had a CAD generator built into your watch.
 

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Oh well the time has past, I had logged off when you posted Shewie!
Strangely I knew a repost was on its way, Ghazzah has 'trained' me well to line them up ready to be shot down :clap:

In quick summary, with the 'mod' all that has been created is redundant material (top left hole to bottom hole) so there is still a good load path in that direction. The minimum edge distance (new hole centre to edge of plate) appears to have been maintained so resisting forces as the dog bone bolt 'pushes' against the inside of the hole. Bolt bearing should be OK.

If the dog bone was to be re-attached to the correct mounting hole there is a hole in the load path. This can be no big deal, the loads will flow round the hole (think of a fluid going round a post stuck in the ground ...... not quite the same due to turbulence issues but the same principal) but without knowing the magnitude of the loads and their initial direction (which change with every position change of the suspension) you cannot be certain. But then you get into the field of fatigue. Aluminium is poor in fatigue ........... which is why so much effort is put into fatigue in aircraft design ........ you know it will crack with repeated loading cycles (if the loads are high enough) and you even build in 'crack stoppers' to contol the cracks! In order to protect against cracks starting, very fine surface finishes are used since a crack will start from an irregularity ........ like the inside of a home drilled hole. With that hole in the load path you have therefore the material conditions for a crack to start. If the loads are low a crack might not start but with that extra hole present the plate will be more susceptable to sideways loads that the plates also resist. So the 'big question' here is the magnitude of the loads and these cannot be determined without a very detailed examination of the shock.

So for the sake of safety I would bin the plates.

There you go Shewie, 'engineering judgment' and a bit of theory ............ much better than a coloured picture based on ficticious loads!
 

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Thanks for that, Mr. Nye. (Actually, it is probably more appropriate, given the avatar, to call you Beakman) :) Look up an old program called Beakman's World for an explanation

One thing I had not even thought of was side loading on the plates. Do you think there would be much if there was no slop at the bolts.
 

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Tee Hee, Beakmans hair hasn't any grey in it, bet he dyes it!

IMHO there shouldn't be significant side loading if there is no wear in any part of the system and everything is perfectly aligned, it should 'float' on the collars that pass through the bearings and the only side loads will be those induced by irregular tightening of the bolting making the plates heel on the ends of the collars.

Thats the theory, but have look at the photo that I posted of a triangle plate earlier, paying particular attention to the area to the left of the bottom bolt hole. Badly scuffed due to contact between the dog bone and the plate. One or more of the bearings in the linkage must have been worn[SUP]1[/SUP] allowing a bit of twist to be introduced and that was the result ................. one of the reasons that I clean and re-grease all the linkage bearings at least once a year.

So my view is that side loads will exist to some extent but the magnitude will depend on the overall condition of the bike and how hard it is used.

1 Might have been frame alignment, swing arm alignment/bent who knows, but something wasn't right!
 

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Pete, what's your thoughts on rotating the plates from a technical point of view?
I realize it changes the ratio of the shock linkage but how and what are the results?
Case in point: I lowered my bike by rotating the plates and rode it for a year.
I then had a Penske built to allow for both + and - length adjustment, rather than their standard + only adjustment so I could return the linkage to standard orientation. It was hard to define the difference as I went to a completely different shock, but I did maintain the same ride height.
Thoughts?
Cad drawings?
Oh no, not him again...lol
Thanx
Hank
 
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