measuring shock length

[Mojoman]

If I wanted to replace my shock with another unit how would I measure the length? Do I need to take the shock out of the frame and measuring the lower mounting eye centre to the upper mounting eye centre or can I just measure as it is in the frame in the pic? Do I keep the pressure in the shock or release it and 'stretch' out the shock?

[covie]

The ghost rt5700 xfusion shock is 100mm as far as i know.

[Mojoman]

The ghost rt5700 xfusion shock is 100mm as far as i know.

What do they mean on the CRC site when it says 190mm - 51mm stroke?

http://www.chainreactioncycles.com/Models.aspx?ModelID=70137

 

Or the RS one with 165mm - 38mm stroke?

http://www.chainreactioncycles.com/Models.aspx?ModelID=53319

[Super_mil]

The 190mm is the distance between the two mounting bolts (known at the eye to eye length)

The 51mm stroke is the length of the shock can move

 

[patches]

The ghost rt5700 xfusion shock is 100mm as far as i know.

 

That's 100mm travel, which tells you nothing about the shock. many different shock lengths can give you 100mm travel. It's all dependent on the linkage design

 

What do they mean on the CRC site when it says 190mm - 51mm stroke?

http://www.chainreac...x?ModelID=70137

 

Or the RS one with 165mm - 38mm stroke?

http://www.chainreac...x?ModelID=53319

 

Not THOSE are the important figures.

 

The 2 numbers you will need in order to make a correct shock choice are the eye-to-eye and the stroke... (as illustrated by Super_mil and his MS paint wizzardry)

 

You might get away with only measuring the eye-to-eye as some shocks only have 1 stroke length option for that specific eye-to-eye. But just to be safe, know both. You also don't need to take the shock out to measure becasue the linkage should be designed in such a way that if there is no load on the frame, no stroke is being used (ie. shock fully extended)

 

The Ghost RT5700 uses a 190mm shock length, and 51mm stroke.

 

 

One thing not to forget is the mounting hardware. Your X-fusion hardware may not fit the DU bushes on your new shock. You may have to get new hardware to install the shock.

Edited October 29, 2012 by patches

[Johan Bornman]

The 190mm is the distance between the two mounting bolts (known at the eye to eye length)

The 51mm stroke is the length of the shock can move

 

 

Stroke length is not quite as you indicate. On a fork, we call it "travel" and on a shock, "stroke." I dunno why.

 

However, your stroke is shorter than the damper body. It has to be, there is stuff inside there that will prevent full stroke. On your picture, I'll estimate stroke to only be 85% of what is indicated there. That would be the official stroke too, not just effective stroke.

[patches]

Stroke length is not quite as you indicate. On a fork, we call it "travel" and on a shock, "stroke." I dunno why.

 

However, your stroke is shorter than the damper body. It has to be, there is stuff inside there that will prevent full stroke. On your picture, I'll estimate stroke to only be 85% of what is indicated there. That would be the official stroke too, not just effective stroke.

 

Simple... becasue they're not the same thing!

 

If a fork compresses to use up 72mm of it's stroke, the wheel front wheel moves (or travels) 72mm. But if a rear shock compresses to use 72mm of it's stroke, the travel of the rear wheel could vary greatly depending on the levereage ratio.

 

Take my 4X bike for instance. 100mm travel 165/38mm rear shock. Mojoman's XC bike uses bigger rear shock (190/51mm) ie. a lower leverage ratio, to achieve the same travel (100mm). therefore the travel is the same, the stroke is not.

 

As for Super_mil's illustration. He's pretty much spot on (give or take a 2mm). A more accurate illustration could not be drawn on a photo using MS paint.

 

The stroke does infact use up nearly all of the exposed part of the dampener shaft. there may be a mm or 2 extra, but certainly not 15%. To check this, simply bottom out your rear wheel and see where that sag ring sits. I know on my Fox DHX 5 Air it actually falls right off when rear wheel is bottomed out. I've also measured my RP23 and the specced stroke is 38mm. The measurement of the area (indicated in red on Super_mil's picture) is 40mm.

[Mojoman]

Thanks all. So to confirm then different shocks will also use different bushings? There is no standard here? And new shocks do not come with the required bushings?

[patches]

Thanks all. So to confirm then different shocks will also use different bushings? There is no standard here? And new shocks do not come with the required bushings?

 

yup! different shock brands have different mounting hardware standards. And no, a new shock will not come with the hardware, simply because the hardware is also frame specific and it would be a waste/too much effort for a shock manufacturer to sell the shock with all the different mounting hardware varients for all the different frames.

 

But speak to the agents for wichever brand you choose, and they will be able to help you out.

[Brian Fantana]

Thanks all. So to confirm then different shocks will also use different bushings? There is no standard here? And new shocks do not come with the required bushings?

 

Certain shocks can use the same DU bushings. You need to confirm whether your shock's DU buhsings can be used with the new one.

 

The size of the DU bushing used will determine which size(diameter) of mounting hardware will be suitable.

 

Most of the shock manufacturers make DU bushings and mounting hardware, so it will be best to use the same brand as the shock.

 

If you go the Fox route, try to get the new style mounting hardware. See here: http://www.thehubsa....nting-hardware/

Edited October 29, 2012 by Brian Fantana

[Mojoman]

_{Thanks everyone.}

[Johan Bornman]

Simple... becasue they're not the same thing!

 

If a fork compresses to use up 72mm of it's stroke, the wheel front wheel moves (or travels) 72mm. But if a rear shock compresses to use 72mm of it's stroke, the travel of the rear wheel could vary greatly depending on the levereage ratio.

 

Take my 4X bike for instance. 100mm travel 165/38mm rear shock. Mojoman's XC bike uses bigger rear shock (190/51mm) ie. a lower leverage ratio, to achieve the same travel (100mm). therefore the travel is the same, the stroke is not.

 

As for Super_mil's illustration. He's pretty much spot on (give or take a 2mm). A more accurate illustration could not be drawn on a photo using MS paint.

 

The stroke does infact use up nearly all of the exposed part of the dampener shaft. there may be a mm or 2 extra, but certainly not 15%. To check this, simply bottom out your rear wheel and see where that sag ring sits. I know on my Fox DHX 5 Air it actually falls right off when rear wheel is bottomed out. I've also measured my RP23 and the specced stroke is 38mm. The measurement of the area (indicated in red on Super_mil's picture) is 40mm.

 

Point taken. I'm now standing and no longer sitting on my brain.

[Super_mil]

Here are the different bushing sizes and the shocks....

 

--12mm DU Bushing which Fit – Answer Manitou, Rock Shox models (Bar, Ario, MC3, MC3R, and Pearl), and X-Fusion (Vector, O2, & Glyde) Shocks

 

--1/2 inch DU Bushing which Fit – Fox, Cane Creek (all but Double Barrell), Romic, Marzocchi Roco, 5th Element Coil, Rock Shox (Monarch and Vivid), and X-Fusion H3 Shocks

 

EDIT to add: I stole the above info from one of the mtbr forum poss.

 

BUT if you are going to go Fox, get the new plastic spacers. A lot less friction in the system due to the plastic used. I really wanted to try this out a couple years ago with vesconite bushes/spacers, but the cost to get a set machined was what stopped me from trying it out. Definitely the way to go since it's be self lubricating and much more resilient to dust, water & mud. I see fox claim like a 50% reduction in friction in the system... .

Edited October 30, 2012 by Super_mil