Ducati.ms - The Ultimate Ducati Forum banner

1 - 20 of 34 Posts

·
Member
Joined
·
7,733 Posts
Discussion Starter #1
I was never able to get my head around the concept that when one raises the rear ride height, one needs to dial in more chain slack to avoid damaging the counter shaft bearing etc. No explanation from anybody seemed able to offer a cogent explanation as to why 30mms slack was not relevant across all ride heights. You lower the height, or your raise the height, and adjust the chain back to 30mms, and you should be okay as it's all relevant was my opinion. Tonight, I took some time, and put my theory to the test, and as far as I'm concerned, I am correct: 30 mms slack is sufficient for all ride heights.

My ride height is raised so I have approx 5mm's between a new tire and the ground once on the center stand. I keep my chain slack at about 35mms to be safe. Tonight, I tensioned the chain to 29mms slack, and removed the shock and link arm so I could then freely move the swingarm through its arc, from lowest point to highest point, and guess what? Theres was NO binding feeling at all; just a nice smooth arcing motion. I then blocked up the rear wheel at the point where the three points of the counter shaft, swing arm pivot, and rear axle aligned, as per a 4' level. And guess what? Theres was still some flex, not much, but still some flex that was *easily* produced with a little squeezing of the top and lower run. But, it was very taunt, no question.

So, what does all this mean? Well, I'm a phucking skeptic and need to see things with my own eyes if I can't conceptualise it in my head, and I'm glad I took the time for this little experiment to finally set my mind at ease about my chain tension and the possible horrid outcomes of mashing my countershaft bearing because I may be a mil or two too tight.

Will I adjust my chain slack at 30mms? No, (and I wouldn't recommend it for anybody) I will continue to dial in a little more, but if I'm at 32 or 33mms, I won't continue to finely adjust tension and align chain run to get 35mms *exactly.*

If anybody would still like to offer an explanation as to why one needs to dial in more slack when raising the rear ride height, and how my observation is incorrect, please do so, but please, make sure it actually explains things in a way that makes sense. I'd love to hear it.

YMMV. :)
 

·
Registered
Joined
·
887 Posts
If anybody would still like to offer an explanation as to why one needs to dial in more slack when raising the rear ride height, and how my observation is incorrect, please do so, but please, make sure it actually explains things in a way that makes sense. I'd love to hear it.

YMMV. :)
Phrickin' eh, it ain't rocket science but just because you cannot conceptualize it doesn't mean everyone else is wrong. Sorry if this comes across kind of strong but we have been over it so many times in the last 5 years it ain't even funny.

I repeat myself but if it will help out a fellow rider, it's all good.

1) Chain tension is set with the swing arm hanging at the lowest point of swingarm travel (the swingarm relative to the ground when lifted).

2) When you raise the ride height the lowest point of swingarm travel is adjusted lower.

3) Thererefore the chain will measure more slack even though the slack at the point the swingarm pivot, axle and countershaft all line up has not changed.

4) Because of point #1 above, the new spec for chain slack must be more than it was before the ride height was adjusted.

5) End of story unless you have something everyone else has overlooked.
 

·
Registered
Joined
·
1,395 Posts
This might help you conceptualize it: on MX bikes we measure chain slack as 3 fingers midway top of swingarm with rider sitting on bike. Key word here is top of swingarm (chain tension is greatest on top).
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #4 (Edited)
Phrickin' eh, it ain't rocket science but just because you cannot conceptualize it doesn't mean everyone else is wrong. Sorry if this comes across kind of strong but we have been over it so many times in the last 5 years it ain't even funny.

I repeat myself but if it will help out a fellow rider, it's all good.

1) Chain tension is set with the swing arm hanging at the lowest point of swingarm travel (the swingarm relative to the ground when lifted).

2) When you raise the ride height the lowest point of swingarm travel is adjusted lower.

3) Thererefore the chain will measure more slack even though the slack at the point the swingarm pivot, axle and countershaft all line up has not changed.

4) Because of point #1 above, the new spec for chain slack must be more than it was before the ride height was adjusted.

5) End of story unless you have something everyone else has overlooked.
As I stated above, my ride height is raised. I adjusted slack to 29mm, which is less than spec of 30/32mm and certainly less than "a little more." There was no binding through out the swing arm's action, ie from its lowest to highest point, shock and link arm removed, and at the point of alignment, there was still some defection easily generated even with 29mms of slack. Please explain which of your 5 points above explains that if it aint' phricken rocket science eh. (Nice to see you break cover)
 

·
Life is too short to worry !
Joined
·
2,650 Posts
My Scottish penny's worth :))

Take the engine sprocket as 'A' the swingarm pivot point as 'B' and the rear sprocket as 'C' and imagine they all sitting on the same horizontal plane.

If you take the distance from A-C it will be 'X' but if you then lower point 'C' , as would happen if you increased ride height , distance 'X' will become gradually lower as it moves closer to 'A'. Taken to its extreme , if you were to continue swinging the arm completely round , to the opposite side , then 'X' would become A-C less A-B.

Now imagine the chain is running straight from A-C (No slack) and you decided it needed 10 mm slack to function properly. Having set the slack you then decide to change the ride-height which then moves 'C' closer to 'A' and the chain would have more "apparent" slack even though nothing had changed so potentially you might decide to reduce it to the original 10mm ?

Only problem is then when the suspension moves up under compression the distance A-C returns to its original and the slack disappears , possibly to less than nothing.

It may help visualise this description to draw the 3 points out so you can "see" what happens to the distances , you can even measure them if it helps.

(In practical terms the chain would intermitantly put pressure on the drive-shaft due to suspension movement potentially causing it to fail)
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #6 (Edited)
This might help you conceptualize it: on MX bikes we measure chain slack as 3 fingers midway top of swingarm with rider sitting on bike. Key word here is top of swingarm (chain tension is greatest on top).

MX bikes have much, much longer suspension travel so I guess this is why we're seeing concentric swingarm pivot-countershafts these days as they always have the correct chain tension if I understand their advantage.
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #7 (Edited)
My Scottish penny's worth :))

Take the engine sprocket as 'A' the swingarm pivot point as 'B' and the rear sprocket as 'C' and imagine they all sitting on the same horizontal plane.

If you take the distance from A-C it will be 'X' but if you then lower point 'C' , as would happen if you increased ride height , distance 'X' will become gradually lower as it moves closer to 'A'. Taken to its extreme , if you were to continue swinging the arm completely round , to the opposite side , then 'X' would become A-C less A-B.

Now imagine the chain is running straight from A-C (No slack) and you decided it needed 10 mm slack to function properly. Having set the slack you then decide to change the ride-height which then moves 'C' closer to 'A' and the chain would have more "apparent" slack even though nothing had changed so potentially you might decide to reduce it to the original 10mm ?

Only problem is then when the suspension moves up under compression the distance A-C returns to its original and the slack disappears , possibly to less than nothing.

It may help visualise this description to draw the 3 points out so you can "see" what happens to the distances , you can even measure them if it helps.

(In practical terms the chain would intermitantly put pressure on the drive-shaft due to suspension movement potentially causing it to fail)

Well the thing is, I put the swingarm through its motion, and aligned the three points, with less than recommended slack, and there was no binding, and still some deflextion at the most extented position of the arc.

I'm not saying anything more than what my experiment/observation means to me, and my maintenance routine, as I think I was clear I'm not recommending, just reporting, but, consider this too: Ducati owner's manuals for the ST4s and the ST3s do not state one must dial in more slack after raising rear ride height. The manuals do instruct the owner on *how* to raise/change ride height, and *how* to adjust the chain tension, *and* there *are* warnings about differences in handling caused by changing ride height, and warnings that an improperly tensioned chain will cause tranny damage, but nothing, nothing from the manufacturer telling owners of ride height adjustable bikes that they must dial in a "little more" slack when they raise the ride height. It's not unreasonable to think Ducati itself does not see this as an issue, only that the chain is kept in the recommended adjustment range and that the rider is aware of handling differences. Now, I think if this is a major issue for raising the rear, which is what most owners of bikes so equiped *will* eventually do, then Ducati, in order to avoid huge warranty loses, would at least say to bring it to the dealer to have the rear raised so the chain can be properly tensioned.

I will continue to dial in a little more slack, as it's best to have a slightly loose chain than one that's slightly tight, but as far as I'm concerned, recommended slack *is* relevant across the ride height range.
 

·
Registered
Joined
·
887 Posts
As I stated above, my ride height is raised. I adjusted slack to 29mm, which is less than spec of 30/32mm and certainly less than "a little more." There was no binding through out the swing arm's action, ie from its lowest to highest point, shock and link arm removed, and at the point of alignment, there was still some defection easily generated even with 29mms of slack.
Please understand that measuring chain slack is very inexact. The harder you press on the chain, the more slack you will measure. What you measure as 29mm deflection I might measure as 34mm deflection.

You adjusted your chain correctly by checking that there was no binding as the swingarm moves through the tightest area (as long as you remembered to rotate the rear wheel and check at multiple points).

The important point here is simply that the *measured* chain slack will vary with changes in ride height even though the actual tightness of the chain at the point of maximum tightness has not changed.

Don't pay attention that Ducati does not mention this fact in the owners manual. Plenty of things go unsaid in the owners manual.
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #9
Please understand that measuring chain slack is very inexact. The harder you press on the chain, the more slack you will measure. What you measure as 29mm deflection I might measure as 34mm deflection.
That's understandable, different folks use different means and come away with different measurements, but I think we all measure deflection at the lower run's half way point at the tighest point in the chain.

You adjusted your chain correctly by checking that there was no binding as the swingarm moves through the tightest area (as long as you remembered to rotate the rear wheel and check at multiple points).
Oh I didn't adjust it that way, I was just checking the SA's action with a raised ride height and no extra slack. I adjusted it back to "my" 34mms slack. I just wanted to get finally a sense of security that my adjustments are not too tight and I'm glad I did because now I'm much more confident in my "sense" of chain adjustments.

The important point here is simply that the *measured* chain slack will vary with changes in ride height even though the actual tightness of the chain at the point of maximum tightness has not changed.

Don't pay attention that Ducati does not mention this fact in the owners manual. Plenty of things go unsaid in the owners manual.
Actually, Ducati has a range for chain tensions for the ride height adjustable ST's, ie 32-34mms, and for the fixed link ST3's like mine, (I upgraded to a Penske shock) 32 is on the SA and 30 is in the manual. I agree, manuals may not say a lot of things, but in the context of giving owners instructions on how to raise ride height and adjust the chain, one might think they would at least mention to use the bigger slack measurement with the rear raised. Other than to warn about transmission damage from an improperly adjusted chain, they really don't say much else. I think one would have to have his chain strung like a cam belt to cause damage to the countershaft sprocket, and I don't think too many riders are that daft, though apparently it can happen. (that's why I needed to check :) ) Like you said, we all get different measurements.
 

·
Chilehead
Joined
·
6,982 Posts
It's actually quite simple.

The OEM slack is measured with OEM settings.

Change those settings, and you will find that in order to achieve the OEM slack at the OEM settings requires more than OEM slack at the new setting.

Basic high-school level trig will confirm this.

Tom
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #11
It's actually quite simple.

The OEM slack is measured with OEM settings.
Okay.

Change those settings,
You mean raise the rear ride height?

and you will find that in order to achieve the OEM slack at the OEM settings
You mean new settings?

requires more than OEM slack at the new setting.

Basic high-school level trig will confirm this.

Tom
I'm not a math guy, high school or otherwise, but if it's that simple, then there's a formula right? Can you formulate this?
 

·
Mr Leakered
Joined
·
8,824 Posts
I was messing with chain tension just last Thursday myself after I installed some new bearings. I have raised my ride height and have struggled with the chain tension measurement also. This is mainly due to the visible droop when on the centerstand. I just looks odd.

In my own method, my minimum adjustment is one flat of the adjuster bolt. Also, I gave up measuring because I simply found that allowing the chain to have a little flop to it on the bottom run while locked in gear is all that was necessary. This was what the OEM settings equated to, i.e. chain tension with stock ride height.

So, setting the tension as such, then sitting on the bike I noted that the chain tensioned up considerably. Too much for my comfort. Since I was sitting on the bike it was not possible to measure. I adjusted the tension by taking out one flat of the adjuster bolt. Sat bake on the bike, got the flop that I typically expect in the tightest section of chian.

After torquing up everything, I checked the centerstand slack. At the half way point, the chain comes close to the swing arm, but doesn't touch. Currently, I found very little difference between the tightest and loosest sections.

Have a good one.
 

·
Registered
Joined
·
1,029 Posts
Okay.



You mean raise the rear ride height?



You mean new settings?



I'm not a math guy, high school or otherwise, but if it's that simple, then there's a formula right? Can you formulate this?
Oscar Has A Heap Of Apples can be used if you know the angle and want the length of a side.
O/H=Sine, A/H=Cos, O/A=Tan. O stands for Opposite. A stands for Adjacent. H stands for Hypotenuse.
A squared + B squared = C squared where C is the Hypotenuse can be used if you now the lengths of the sides and you want the angle. This only works on right triangles.

The Swingarm will be your Hypotenuse. A line parallel to the swingarm bolt perpindicular to the ground will be your opposite in this case. and a line parallel to the ground the same height as the rear tire axle will be your Adjacent.
 

·
Registered
Joined
·
2,732 Posts
This is so confusing! I'm going back to my BMW!

Seriously though, just give it about 3/4" of play at the tightest point on the centerstand. The tension has held for 7,000 miles so far.
 

·
Registered
Joined
·
2,732 Posts
You are blessed with a few extra loonies then. Does he have you roll forward to check for the tightest point?
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #17
Oscar Has A Heap Of Apples can be used if you know the angle and want the length of a side.
O/H=Sine, A/H=Cos, O/A=Tan. O stands for Opposite. A stands for Adjacent. H stands for Hypotenuse.
A squared + B squared = C squared where C is the Hypotenuse can be used if you now the lengths of the sides and you want the angle. This only works on right triangles.

The Swingarm will be your Hypotenuse. A line parallel to the swingarm bolt perpindicular to the ground will be your opposite in this case. and a line parallel to the ground the same height as the rear tire axle will be your Adjacent.

Okay, so that's somewhat helpful, I guess. :eek: Now, for guys like me who aren't as well versed in math as you, can you put this into step by step instructions using actual parts on the bike. I don't understand how I can get a line that is both parallel and perpendicular at the same time as this is what the above seems to infer. But, will this give me a way to determine how many more mm's of slack I will need if I raise my ride height by "X" amount of mm's? Could I generate a "reference chart" using "trig", for example, ie ride height raised 4mm's, add 1 mm slack?

If it's that simple, (for math guys) then I have to ask, "why hasn't it been done before?" :)
 

·
Member
Joined
·
7,733 Posts
Discussion Starter #18
This is so confusing! I'm going back to my BMW!

Seriously though, just give it about 3/4" of play at the tightest point on the centerstand. The tension has held for 7,000 miles so far.
Yes, but what, for the purposes of this thread, if you raise your ride height? What would your slack then be? (3/4's of an inch seems very tight to me, as an inch is 25mm's and the specs are 32-34 for a ST4s)
 

·
Registered
Joined
·
1,029 Posts
You can see the triangle in the attachment.

I don't know how you could use this to calculate exact chain tension. I was just giving you the trig functions to calculate the sides and angles of the swingarm and how they change with ride height. Use them at your own risk. If you get the relationship figured out please share the info.
 

Attachments

·
Registered
Joined
·
2,732 Posts
Yes, but what, for the purposes of this thread, if you raise your ride height? What would your slack then be? (3/4's of an inch seems very tight to me, as an inch is 25mm's and the specs are 32-34 for a ST4s)
I would make my chain tension the same regardless of ride height setting.
My 3/4" play is just pressing up on it to the point of no resistance. The manual illustrates total up and down movement at 32mm (ST2 is 30mm for some reason). So for me that's what it works out to, I just use that method because it seems more consistent. I might push/pull harder one time to the next.
 
1 - 20 of 34 Posts
Top