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Lowering front end


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12 hours ago, Sweeper said:

Works great! I think mine was about 8mm.


Sent from my iPhone using Tapatalk

 

Did mine ~8mm as well.   

Raised the back as well by putting a few washers on the top of the rear shock

 

No ill effect at high speeds (200+++ :goofy:)

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It is a common modification, probably because it is so easy to do.  In theory it should create some instability, but so can fitting different tyres, so the best thing to do is (1) check where you're at now and (2) change it a specific amount and see if you like it.  

 

That's the front.  The rear is more complicated, depending on whether you've got a 3rd or a 4th gen.

 

Ciao,

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Ah!!   Just remembered you have 3rd gen.......

 

And they have a different way to mount the rear shock

 

3rd Gen

3rd.JPG.48417a980c2c9c914a838654c87d79a0.JPG

 

So you cannot out in washers (on part #1) like you can with the 4th Gen

4th.JPG.97d622c082159913222aec951e244443.JPG

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Not on a '92 VFR750FN you're not!  That is a nice job someone's done on the linkage design, but it only works for the RC36-II, which has a completely different rear suspension design.  

 

In order to raise the rear of an RC36-I, you have a few options:

 

1. Get a new shock, either with a custom length a bit longer than stock, or one with enough height adjustment to make a difference.

2. Get a shortened dogbone linkage, but you'd probably have to make or have this made (requires welding of steel, but is quite simple).

3. "Flip the eccentric", meaning rotating the chain adjuster all the way around so the axle rides in an arc at the bottom, rather than at the top (requires countersinking one of the brake caliper bracket fasteners).  However, this raises the rear quite a lot (30-40mm, IIRC), so the stands will be too short...

4. Machine a custom top shock mount.  I've only done this on my bike, which has an RC30 swing arm, but it should work with the OEM swing arm.  See below:

 

20161109_162523y.thumb.jpg.7cadd3607c34b77c8eebf0b3bfa73ea8.jpg

 

Ciao,

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Is that so? ?is it that much of a difference?  I dont remember were i found the project, and might have forgot what year he did it to. 

So, for me, i'll manufacture a shorter dog-bone. 

 

 

Someone got input on how much shorter gives what raise? 

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It's roughly 1:3, so 10mm shorter = 30mm higher.  With an M10 bolt through the linkage, you can see there won't be enough metal to simply re-drill; you need to weld up and re-drill.  I think Thurn in Germany might sell a linkage?

 

Ciao,

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That's because you keep looking at RC36-II parts!  It's this one you need:

 

99-UH0036.JPG

 

€159

 

Ciao,

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I wasn't suggesting you do!  The OEM one looks just like that, but is about 10mm longer (and has bearings and seals).  I've heard of people getting fancy and make them adjustable (using LH and RH rod ends), but that's probably overkill for a street-ridden VFR750.

 

Ciao,

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As a short legged guy, I wanted the lower the whole bike, so I lowered the front by lowering the tubes about 10 mm. For the rear, I shortened the linkage about 10 mm causing about 3 cm lower rear. So if you want rise the rear, I believe you have to extend the linkage, not shorten it...

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Did you do the work yourself?  Nearly all bikes with similar suspension configurations are lowered by increasing the length of the dogbone, and raised by decreasing it.  I know I have the measurement somewhere for the Thurn linkage, but I can't find it now.  

 

[NEW STUFF]

Okay, I re-installed my Tony Foale software just for this purpose (haven't used it for a while).  Just look at the "Rocker and link" section in the images below for the moment.

 

RC36-I OEM linkage (I think that's the right measurement, but it doesn't have to be to illustrate the point):

5a7255a0f054e_RC36-IIRearSuspension-1.GIF.de5e8dcdbd4c44f3f0de6cf45cc82f6b.GIF

The tyre is flat on the floor.

 

RC36-I with 10mm shortened linkage:

5a7255e869577_RC36-IIRearSuspension-2.GIF.712195391d7597eddb852e904964694b.GIF

The tyre is now below the floor, which obviously cannot happen, so it really means the bike is raised by ~34mm with a 10mm shorter link.

 

RC36-I with 10mm extended linkage:

5a725611f2b31_RC36-IIRearSuspension-3.GIF.ba1286d98cd09c34f13e148610acfb01.GIF

And similarly here, the bike actually gets lowered by ~34mm with a 10mm longer link.

 

(The dogbone we're talking about is the green bit.)

 

Ciao,

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22 hours ago, JZH said:

Did you do the work yourself?  Nearly all bikes with similar suspension configurations are lowered by increasing the length of the dogbone, and raised by decreasing it.  I know I have the measurement somewhere for the Thurn linkage, but I can't find it now.  

 

Ciao,

+1

 

 

regarding you guys telning me to just raise forks Max 10mm, why so?

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Why what so?  Lowering the front has "generally" the same effect as raising the rear.  You can probably lower it even more than 10mm in the front, but if you go too far you can experience issues with fender/radiator clearance and even ground clearance when leaned over.  Raising the rear is the preferred method, if practical, but lowering the front is much easier to do.

 

Ciao,

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