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Does the GT swingam fit the FJ09?


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1 hour ago, OZVFR said:

Hard acceleration pulls on the top of the rear sprocket trying to bring rear wheel closer, and causes it to push on the rear spring so wheel lifts.

Clear as mud.

Looks like it's more than that, had some time to look into it. This website explains it pretty well:

There are two forces that work to extend the suspension to counter squat during acceleration. One is driving force from the rear tire, which pushes the axle forward, while the other is the drive chain, which pulls the axle forward and down in the direction of the top chain run.

motorcycle anti-squat forces

The three forces we are concerned with during acceleration are weight transfer (green), driving force (blue) and chain pull (red).

Driving force acts horizontally on the axle, and is equal to the amount of acceleration. If the swingarm slopes up from the axle toward the front of the machine and the pivot, driving force will extend the suspension; however, deep in the travel the swingarm may slope down toward the front of the machine, and driving force will serve to compress the suspension further.

Chain pull force also acts on the axle, and its direction also changes as the suspension moves through its travel. The magnitude of the chain force is proportional to the driving force in relation to the rear sprocket size and rear tire diameter. Chain pull generally serves to extend the suspension (picture the chain attached to the axle itself rather than the sprocket, and the effective line of force runs below the swingarm), but like the driving force and swingarm angle, may work to compress the suspension at extreme travel.
https://www.datamc.org/data-acquisition/suspension-data-analysis/anti-squat-geometry/

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Keith Code proves rear suspension lifts under 'normal' acceleration, i.e. on the flat, with a pointer fitted to a bike. They then go for a spin and film what's happening. If the rear of the bike went down, very powerful bikes would be spinning up left, right and center. You'd be lessening the desired push into the track for the drive forward. The desired geometry pushes the tyre into the ground.

Because the front lifts significantly under acceleration, many people see this as the rear squatting. It is in fact lifting, just less than the front.

Treat yourself to watching a few dyno runs online. Watch the rear of the bike when they go for it through the gears. All will be clear..

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Thing about a dyno is ……..the motorcycle is held in place unlike the real world.

In the real world…..the motorcycle moves forward when acclerating.

Another thing that effects how mototcycle handles is the location of the center of gravity. 

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19 hours ago, kilo3 said:

It's that the opposite? Since the chain front sprocket is higher than the pivot point of the rear swingarm, it's going to expand the suspension under acceleration.  Don't super fancy race bikes have cams on their swingarms to adjust the height in relation to the frame?

I also might be full of crap but I do like physics.

Well, heres some reading suggestion for ya685111A2-E0EE-4454-9A75-8DA4A18E6EA8.thumb.jpeg.9456df39dee92c7414c907a892373183.jpeg

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Edited by duckie
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10 hours ago, duckie said:

Thing about a dyno is ……..the motorcycle is held in place unlike the real world.

In the real world…..the motorcycle moves forward when acclerating.

Another thing that effects how mototcycle handles is the location of the center of gravity. 

Yes good point. It's not a real world demonstration. But the rear doesn't go down.

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13 hours ago, Manxkiwi said:

Yes good point. It's not a real world demonstration. But the rear doesn't go down.

You are correct……buy it only goes up cause the the motorcycle is not allowed to move. You can get the same effect by putting your front tire against a wall and slowly let the clutch.

To believe a stationary motorcycle suspension is gonna act like one on a moving motorcycle is wrong. 
Ive read about anti squat…..but nothing about anti rising…..why is that?
 

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  • 1 month later...

Hi all

Thanks everyone, I have learnt a lot from the chat on this thread. I replaced the swingarm at Christmas and have now done a few rides .... and I really like it.

I sourced a 2018 swingarm and required extra bits from France and with airfreight it was cheaper than buying one locally in Australia,,,. The swingarm is 89mm longer, the linkages are the same but the linkage mount on the swingarm is 5mm wider. Beyond a 12 link longer chain the only other adjustment was to wind on 4mm more rear pre-load on my Mupo GT1 shock with 11.5k spring to get a similar rider sag setting.

It tracks through corners better, absobs bumps more easily (our roads are even more shite after record rains) and I can wind on power earlier and hold my line out of corners. It was initially less agile tipping into the corner but that changed when I added the 4th mm of preload and it is now close to what it was with the standard swingarm.

I am now very, very happy with my squat.

Cheers

Stephen

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2 hours ago, stephen falco said:

I am now very, very happy with my squat

Glad the extra 3 1/2 inches worked out for you, it's more than satisfying when your modifications give you the required outcome. Might think about slightly narrower bars for mine now,

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3 hours ago, stephen falco said:

I have learnt a lot from the chat on this thread. I replaced the swingarm at Christmas and have now done a few rides .... and I really like it.

Beyond a 12 link longer chain the only other adjustment was to wind on 4mm more rear pre-load on my Mupo GT1 shock with 11.5k spring to get a similar rider sag setting.

I applaud you for trying something different and not being afraid to experiment. 👍  Small adjustments can make big improvements.

I never ride without a 13mm wrench and a straight slot screwdriver to adjust my shock or forks.  I cant count how many times I have pulled off the road and made a quick one-click adjustment, some times I like it and other times I change it back after awhile.

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***2015 Candy Red FJ-09***

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  • 3 weeks later...

Hi all

I learnt a little more about my swingarm. It is the Police model, B56-22110-00 MT09TRP REAR ARM COMP which at 710mm is the longest available, about 95mm longer than my 2017 model Tracer's.

The one I thought I was getting was the 18-20 model B5C-22110-00 REAR ARM COMP which at 670mm is about 55mm longer.

I learnt that beause the Pyramid Plastics rear hugger I ordered wont fit. lol

Anyone interested in a brand new hugger at a very good price??

Cheers

Stephen

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4 hours ago, stephen falco said:

I learnt a little more about my swingarm. It is the Police model, B56-22110-00 MT09TRP REAR ARM COMP which at 710mm is the longest available, about 95mm longer than my 2017 model Tracer's.

There’s some information I was completely unaware of previously:  a unique swingarm for police model bikes.  Who knew?  🤷‍♂️

95 mm is about 3.75 inches… that is a huge difference!   I’m glad you’re happy with the results; I don’t think I would be brave enough to take that big of a swing at it. 

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