Swingarm Multistrada 1260 on Multistrada 1200? - Page 2 - Ducati.ms - The Ultimate Ducati Forum
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post #11 of 26 (permalink) Old Aug 7th, 2019, 3:32 pm
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@TallOne :
Actually I already changed the springs with stiffer ones, but it's a good idea to do more detailed analysis of the bike and measure all the parameters: so far I trusted the shop who changed the springs, you never know...
did you feel like the stiffer springs cost you touring comfort. I'd like to go heavier but with Sachs I'd need to go to a single rate spring which I'm worried will cost me more in touring comfort than I'd gain in handling.

Unless someone knows of a spring mfgr doing heavier dual rate springs for sachs (I'd sort of given up on that)

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post #12 of 26 (permalink) Old Aug 7th, 2019, 4:09 pm
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I don't know how much longer the ~one~ swingarm is over the one on your bike. But you can extend your wheelbase rather easily by lowering the rear and raising the front. That will also increase your rake (relative to the road) and your trail. Both of which will increase stability.

One other thing to note; going with a longer swingarm will soften the rear end. there will be more leverage against the rear suspension which will create a softening effect (similar to installing a rear spring with a lower spring rate). At the same time it will also increase what is known as "compliance" with the road's surface.

I have actually gone to the trouble of lengthening swingarms in the past. I have actual experience with the cause and effect issues involved.

You may wish to start by reconfiguring your bike's suspension to lower the rear and raise the front ... that will increase the distance between the axles (aka "wheelbase"). It will also increase the rake up front ... for instance, a bike with a 60 inch wheelbase will increase rake by about one degree for every inch the rear is lowered. The trail will also increase, which will also slow the motorcycle's responses.

IMPORTANT: When you measure your wheelbase when doing these types of reconfigurations, DO NOT measure the distance between the two axles. Instead, set up a carpenter's square on the floor so that the vertical arm of the square is aligned with the center of the rear axle and mark the floor where that vertical arm of the square meets the floor .... then do the same with the front axle, marking the floor where the vertical arm of the carpenter's square aligns with the center of the front axle. Then, measure the distance between the front and rear marks on the floor, and record that figure (write it down). As you make changes to the suspension (lowering the rear and/or raising the front) do the exact same procedure and record any changes as you make changes to your suspension set ups. Using a square to mark the floor where the axles are is the correct (and only correct) way of measuring your wheelbase.

If you've only lowered the rear, make certain to place the bike so that the carpenter's square at the rear aligns with the initial marks you made on the floor and observe where the front axle is now relative to those initial marks ... this will tell you how far forward you've moved the weight bias.

If you only raised the front, make certain to place the bike so that the carpenter's square at the front aligns with the initial marks you made on the floor and observe where the rear axle is now relative to those initial marks ... this will tell you how for rearward you've moved the weight bias.

So maybe lower the rear by an entire inch, and raise the front by another full inch. Take notes, take measurements as you go along, and make note of the bike's response to the changes.

Also remember that installing a longer swingarm is going to change the F/R weight bias ... by quite a bit! If the ~other~ swingarm is (let's say) 2 inches longer than the one currently on your bike, you've just moved roughly 600 pounds 2 inches forward relative to the rear wheel (weight of bike plus weight of rider).

Some things to think about.

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Last edited by Rex Coil 7; Aug 7th, 2019 at 4:22 pm.
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post #13 of 26 (permalink) Old Aug 7th, 2019, 8:19 pm
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@Rex Coil 7
I don't know how much longer the 1260 swingarm is over the 1200 either but I do know that the stock 1260 15/40 chain is 114 link whereas the 1200 15/40 is 108 links.

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post #14 of 26 (permalink) Old Aug 7th, 2019, 10:53 pm
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@Rex Coil 7
I don't know how much longer the 1260 swingarm is over the 1200 either but I do know that the stock 1260 15/40 chain is 114 link whereas the 1200 15/40 is 108 links.
So that suggests roughly 3 links longer (6 links halved). Just estimated, that is ~about~ 2 inches .... roughly so.

Is the specified wheelbase of the two bikes 2 inches or so in difference?

The point there is that I'd guess that Ducati didn't just stick two inches on the rear of the bike, I'd guess that the frames, engine placement, swingarm pivot location, and headstock placement have all been moved around to create a specific weight bias on the longer bike. That said, sticking the longer swingarm on the shorter bike will not replicate the longer motorcycle ... it will create an entirely different machine altogether. As I previously pointed out, a longer swingarm will improve "suspension compliance" which will serve to keep the rear tire attached to the road surface ... which we all know means better traction and handling in all situations (accelerating, braking, cornering). Compliance may have been at least part of Ducati's goals (rather than just sticking 2 inches on the ass end of the longer bike) ... and that can be determined by looking at how Ducati distributed the longer swingarm's increase in length.

That said ....

... I know the manuals for the Supersports, Monsters, and Superbikes all have fully dimentioned frame diagrams near the back of the manuals. Perhaps these Multistrada manuals also contain such data. If so, it would be pretty simple to check engine placement, headstock location, swingarm pivot location, and so on in comparison with each of the two Multistrada models (the one with the shorter swingarm compared to the one with the longer swingarm).

That would be deeply valuable information to study before attempting to attach a longer swingarm to the shorter bike.

Some of that extended swingarm length may have also been applied towards moving the swingarm pivot closer to the countershaft sprocket's center without moving the weight bias too far forward. The closer the swingarm pivot is to the countershaft center the less the bike is upset during acceleration and engine braking, making for a more stable motorcycle when throttling up and throttling back. The closer the swingarm pivot is to the countershaft sprocket center also means that the chain's length will vary less throughout the entire rear wheel travel, meaning a bit more chain tension may be used without worry of binding the rear suspension since the chain's tension will vary less throughout the rear suspension's travel. A bit less chain slop provides smoother throttling up and down without ~jerking~ the bike and upsetting the bike's attitude and destabilizing it, which is especially advantageous while cornering.

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post #15 of 26 (permalink) Old Aug 8th, 2019, 2:13 am Thread Starter
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Originally Posted by DaveK View Post
did you feel like the stiffer springs cost you touring comfort. I'd like to go heavier but with Sachs I'd need to go to a single rate spring which I'm worried will cost me more in touring comfort than I'd gain in handling.

Unless someone knows of a spring mfgr doing heavier dual rate springs for sachs (I'd sort of given up on that)
No, it's still comfortable. I don't remember which stiffness I have now, but I can look it up if you need it. the new spring they put on my shock absorbed is indeed not progressive.
I think that adventure bikes have softer springs than most touring bikes, so if you don't need to go off road it's a good improvement to increase stiffness in favor of touring and sport performance.
Perhaps it would help as well to lower the bike a little, for the same reason....

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post #16 of 26 (permalink) Old Aug 8th, 2019, 8:09 am Thread Starter
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Originally Posted by DarR View Post
@Rex Coil 7
I don't know how much longer the 1260 swingarm is over the 1200 either but I do know that the stock 1260 15/40 chain is 114 link whereas the 1200 15/40 is 108 links.

The wheelbase of M1200 is 1529mm, the wheelbase of M1260 is 1585mm, as reported in the user's manuals. So, the swingarm of M1260 is more or less 56mm (2.2 inch) longer; it's not exactly 56mm since they also increased the trail of a few mm and increased the steering head angle.

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post #17 of 26 (permalink) Old Aug 8th, 2019, 10:10 am
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Originally Posted by EffeRed View Post
The wheelbase of M1200 is 1529mm, the wheelbase of M1260 is 1585mm, as reported in the user's manuals. So, the swingarm of M1260 is more or less 56mm (2.2 inch) longer; it's not exactly 56mm since they also increased the trail of a few mm and increased the steering head angle.
Longer wheelbase of the 1260 does not mean that the swingarm is longer. That is an assumption until it's proven true. For example, increasing roughly just one degree of rake ("steering head angle") comes to about one additional inch of wheelbase.

If Ducati were to apply the additional 2 inches of wheelbase to the swingarm, that would move about 600 pounds of weight forward to the front wheel (wet bike weight plus decked out rider weight). That would be a massive ... massive ... weight bias change. It would also move close to 600 pounds farther from the rear wheel ... which could make the bike downright dangerous for some riders (greatly increasing the likelihood of a high side) since the rear tire would be more likely to spin under power when exiting a corner, then catching (and winding up the bike like a spring), snapping the rider right over the handlebars.

I still highly suggest comparing the frame dimensions of 1200 and the 1260. Those figures may be available in the manuals of both bikes, usually found near the very back of the manuals. It may be correct that the 1260's swingarm is, in fact, longer by an inch or so ... but far better to actually and factually know that rather than making assumptions that may produce a dangerous condition.

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post #18 of 26 (permalink) Old Aug 8th, 2019, 12:10 pm Thread Starter
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@Rex Coil 7

Thank you for your advice, I agree I need to spend some time doing measurements. Any way you can easily see at a Ducati dealer (if you can see the 2 models together) that clearly the swing arm is way longer. This is also supported by the fact that the chain is longer as well.

The fact that it is longer has impact on the mass distribution as well as on the stiffness of the suspension as you said before: I will need to change the spring of the shock absorber.

The thing is, influencing the position of the center gravity w.r.t. the contact points of the wheels is the actual aim of the change. I know this quite well since I made my graduation thesis on the topic: if you want to reduce the instability of the wave mode oscillation that happens at high speed, you need to increase the distance from center gravity and rear wheel contact point. Same effect is if you reduce the distance between center gravity and front wheel contact point. Since it would be very difficult to move the position of the center gravity, as well as move the front wheel closer to it, the easiest way is to move the rear wheel backward.
Unfortunately a steering damper has a marginal effect on this problem, since the frequency of the waving is rather low. I guess this is why Ducati didn't put a damper on the 1260.

You can see the effect of changing the distances between wheels and center gravity on this video:
This is about trailers, but the principle is the same.

And yes, there are several cons in this change, I totally agree. But this is about finding a compromise: after all if I want to load the bike like a mule :-) (with panniers and top case) I can either accept to reduce the speed, or sacrifice some handling in favor of stability.
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post #19 of 26 (permalink) Old Aug 8th, 2019, 1:26 pm
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@Team Gorgonzola :

I really wish I could say the same about my bike...

I have been riding bikes for 31 years, I did lots of crazy things with many bikes. When I read posts like yours I really don't know what to think, I should be able to do the same! I tried several options, I even focused on my riding style to be more neutral on the handle bar (I come from a racing bike, which allows to be more aggressive of course).

I don't doubt that you, as many others, can have a lot of fun with this bike. For some reasons it's not working for me, maybe my riding still is still not ok.

But maybe I'm not the only one with this issue, otherwise Ducati wouldn't bother to increase the pitch of 50mm. So, I'm gonna give it a try!
Maybe the suspension/tire brand and pressure, combination does not work for you. Been riding 2 up with the wife and luggage. The front felt lighter and leave the ground under heavy handed acceleration, and in general the bike felt softer and less responsive, especially on twisties, yet, handling was solid and predictable. I ride angel GT f35/r32

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post #20 of 26 (permalink) Old Aug 8th, 2019, 3:38 pm
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@Rex Coil 7

Thank you for your advice, I agree I need to spend some time doing measurements. .... (etc)
Ok, you seem to totally know yer shit so I am quite confident you'll make the proper choices.

I admit that I become over-concerned anytime I see someone talking about moving things around on their motorcycle, especially a motorcycle that is to be operated on public roads where the stakes become FAR higher in the event of a problem. Track bike, or dirt bike? ... Pffft ... have at it! But public roads are loaded with unintended victims in the event someone goofs around with their bike's dimensions without having some idea of WTF they're doing,

Dig in! Be sure to report your findings here in forum. I'm very interested to know how things went. If for no other reason than posterity.

Best of luck ... I hope you can get your bike to make friends with you.



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