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 Post subject: Rear Shock length
PostPosted: Tue Jan 11, 2011 9:08 am 
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Joined: Sun Jan 09, 2011 1:26 am
Posts: 175
Images: 6
Location: Melbourne, Australia
Hi Folks,
I'm building a replica TT2 and require the length of the rear shock eye to eye.
The frame is a Steve Bridge replica based on a Verlicchi with a replica round tube swingarm.
The width of the flanges both on the frame and on the swingarm measure 23.0mm. What brand of shock would you recommend and would they have eye widths slightly shorter than the above dimension? Thread size is M10.

Please feel free to list the brands and spring rates based on a 90kg rider suited up.

Thanks,
Steve

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"...Honey, it's only a project bike...."


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 Post subject: Re: Rear Shock length
PostPosted: Tue Jan 11, 2011 9:52 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Hello Steve,
The shock length can vary from frame to frame. (as I learnt)
My frame is from Old Racing Spares in Italy and will have different dimensions to others.
Also the swing arms are different.
The learned gents here suggest to have a swing arm droop of 12 degrees, while maintaining your 24 degree fork rake.
So a different length from eye to eye for different frames and swing arms.
I had all sorts of handling issues with mine until the gents here set me on the right track. Now it's excellent.
I used a Wilbers shock, but any fully adjustable quality shock would be good. (adjustable length is good)
I suggest to set your frame with a motor or bare cases bolted up and the swing arm attached, to a level bench or floor, fit your triple clamps and forks, and wheels. Then measure the fork rake, and set the swingarm at 12 degrees droop, then measure eye to eye for your shock.

The rest of the measurements you asked for I will dig through my reciepts and tell you what I used.
(although digging through reciepts always scares me)

Graeme


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 Post subject: Re: Rear Shock length
PostPosted: Tue Jan 11, 2011 10:03 pm 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
A simple engine stand that you can build the whole bike on makes things easy.

Image

graeme


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 Post subject: Re: Rear Shock length
PostPosted: Thu Jan 13, 2011 1:20 am 
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Joined: Sun Jan 09, 2011 1:26 am
Posts: 175
Images: 6
Location: Melbourne, Australia
Hi Graeme,
thanks for the PM & your knowledge.
That is the perfect solution since I expect this project to take a while.
I'm correct in understanding the swingarm droop is from the horizontal using the pivot pin as a datum?

Besides accumulating the parts, I'm also in the process of building a new home and a workshop for me and my stuff. It's been in the planning stage for a long time. I dare not dismantle the engine when I have to move twice over. But, I will use the joined engine cases as a starting point to dry fit the frame and swingarm and measure the centre to centre distance. Does the image you supplied show the swingarm at 12 deg?
I hope the weather and recent floods are not affecting you personally or anybody close to you.
Thanks again.
Regards,
Steve

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"...Honey, it's only a project bike...."


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 Post subject: Re: Rear Shock length
PostPosted: Thu Jan 13, 2011 3:01 am 
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Joined: Sun Nov 07, 2010 10:54 pm
Posts: 425
Location: Brisbane
Hello Steve,
The picture with the engine stand was taken before the boffins here enlightened me. It's probably 6 to 8 degrees.
I used a '95 750 SS as the doner and made the stand to hold both wheels 25mm off the bench. Then removed the SS frame and front and fitted the TT2 frame and 748 front, still with the wheels 25mm off the bench. Then carried on building a TT2 replica (but a little off the factory recipie) (ok, a lot off)
So I ended up with an SS with 24 degree rake in TT cloths.
This didn't handle well, so I asked for help here. And learned some geometry truths.
Now the difference is amazing.

Yes 12 degrees from horizontal, the length of your forks will also alter the angle.
I started with 24 degree rake, and then set the swing arm to 12 degrees, then check the trail and see how the chain lays over the swingarm at the swingarm pivot.
Depends what front end , wheels, frame , swingarm etc you use.
Other more knowledgeable gents here may have better ideas.

graeme


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