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> R6 rear shock conversion, and nifty spring compressor tool
rotortech
post Mar 8 2010, 08:20 PM
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This is mainly to say thanks to realrazor for tips on R6 shock conversion. Since I weigh 190 lb I went ahead and changed to the FZR spring. I have fit up the shock and the modified dogbones then saved the fun stuff for last. After modifying, ruining and then throwing away automotive type spring compressor - I went shopping for a decent tool.

Here's the tool. I bought it from eBay. There are several sellers of the same tool. I got this one for $35 NO SHIPPING. It has little plastic shoes over the steel hooks to keep from knocking the paint of of the spring. The FZR spring is no sissy. I had to use an open end wrench on the frame of the tool. It bent the frame a bit but did not disable it. I would say that this spring is the limit for this particular tool. It worked well and I would recommend it for occasional use.



This is a picture of the tool when using it on the spring. That's the FZR spring mounted on the R6 shock.'



And here is the R6 shock with the original R6 spring next to it. The springs are identical except for the diameter of the wire that the spring is wound from. R6=.425" dia and FZR=.625"dia. That little difference made a huge difference in the rate. I didn't measure the actual rates but I did the calculation to get some idea of the magnitude. Stock FZR spring calculated rate is 50.5 kg/mm and the stock R6 calculated rate is 35.2 kg/mm.



Thanks again for those who came before me. I have heard others gripe about not being able to get a decent spring compressor so I thought some of you could use this. I would just recommend that you use a little oil or grease on the threads and at the thrust washer. Worked fine for me.


--------------------
Read this first then ask questions:
CPR for the FZR

Rotortech
Indianapolis

1994 Yamaha FZR 600 Purchased as project bike Jan 2010
Finished 10 July 2010 My Build Thread with pictures here.
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JRK5892
post Mar 10 2010, 02:41 PM
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can you by chance do a write up on the install as you do it? the more i see this the more i want to do it!


--------------------

Joe Knapp
www.thepowderpro.com
Chicago IL
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Brutal Tooth
post Mar 10 2010, 07:42 PM
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for those of you out there, getting a REAL r6 tail looks ALOT better than the airtech crap mod. I think that stuff should be banned. There are a few ppl who have the real vs fake, and its quite clear what is what. Target30 from FZRonline has a real tail, see his if you are thinking about converting.
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majordomo490
post Mar 14 2010, 05:43 PM
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Tell me how do you mathematically calculate spring rate based on guage?
Doesn't coil spacing and material effect the rate?
This stuff is too advanced for me!
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rotortech
post Mar 14 2010, 07:00 PM
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major,

From the Eibach website here is a little information:

A coil spring is really a torsion spring--the wire twists as the spring compresses. The material's reluctance to twist is what supplies the resisting force. A common misconception is that a coil spring "sags" losing spring rate over time, but a look at the components of the equation for the spring rate of a coil spring will show you that is not likely if the spring is properly designed.

Spring Rate = F/S = Gd4/8ND3 where: (this means d to the 4th and D cubed in this equation)
F = spring force.
S = spring deflection.
G = torsional modulus of the material.
d = wire diameter.
N = number of active coils.
D = mean (average) coil diameter.

There are online calculators that allow you to just fill in the coil diameter, wire diameter and the active number of coils (don't count the ones that are ground flat at the ends). To be honest, I didn't spend a lot of time on this calculation and I think I used the wrong torsional modulus for G. But the % difference between the two springs was my main point. The R6 spring is way too soft to use on the FZR geometry unless you are really a light weight.

JRK5892 - I just did what reelrazor already said to do. You have to drill out the top R6 bushing from 10 mm to 12 mm and add two spacers to center the top shock mount in the frame. You also use the pivot from the FZR and throw away the pivot and dogbones from the R6. Then you need to make or modify some dogbones. I did it the way reelrazor showed us by making them adjustable. Once I have the set up dialed in I can make simple flat ones at just the right length if desired. I am not planning an additional writeup but will answer any questions that you have.

My post here was to share this tool with you guys because I have read some complaints about some of the other spring compressors out there. This thing was cheap and worked fine for me. The tool was very secure and safe to use.

I haven't been working on this project for about a week (it's killing me!) due to abdominal surgery. I am pretty sure that I will sneak back out to the garage while I am "healing up" at home this next week. I did manage to get most of the heavy suspension work done prior to surgery. Wish me luck. I still want to get this bike out soon.

Brutal - The tail shown in my picture is a real R6 tail with hotbodies undertail. I traded this to MLS for the entire stock tail because I wanted to go back to stock on this project. His installation looks great. Just search for member MLS. One tip - the guy who installed this tail on my bike filled the gap at the gas tank buy chopping the "horn" part of the front seat and installing it in front of the R6 seat. It looked very natural there.


--------------------
Read this first then ask questions:
CPR for the FZR

Rotortech
Indianapolis

1994 Yamaha FZR 600 Purchased as project bike Jan 2010
Finished 10 July 2010 My Build Thread with pictures here.
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skeeds
post Mar 15 2010, 05:17 AM
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ive already done the r6 swap just trying to track down a spring and then im off. the standard spring is stupidly soft for the bike and its killing me not being able to ride her. i got my dogbones from ebay (uk) it was ajack up kit for a different bike cant remeber which one but they took the height back up no problem.
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majordomo490
post Mar 18 2010, 05:42 PM
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Thanks rotor.
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