Evo rear travel 6 inches. NOT.

[jimbo]

I'm going to raid my Evo for parts so I'd figure I measure the travel while it's still in one piece.  The Evo will be made whole again later with lessor parts.

I measured the travel from 2 different points and got 2 different answers.  

One method yielded 4.5 inches and the other yielded just under 6 inches.  Ironically I thought the measurement point that yielded the 6 inch would be more accurate.  6 inches is way more than the 4.7" of the factory spec. so I don't know what to think.

Bike is a 2000 Evo with the original NR2 shock.  

Measurement methodology:

I turned the bike upside down and got the wheels the same height by adjusting the seatpost.  Used a level to make sure the tires were the same height.  I disassembled the shock and made wooden stick models of what i2i would be if fully compressed.  I ignored the bumper so this would be full theoretical compression.  

Methodology 1:

With the shock mounted I measure the distance from the ground to the ground contact point.  Remember the bike is upside down.  I took the shock off the bike and stuck a scissors jack under the back tire.  I lowered the back tire till the i2i on my wooden model matched up.  I took another measurement from the ground and the tire ground contact point.  Comparing the measurement points, I get 4.5 inches.

I had a couple issues using this method.  The swingarm pivot to the ground contact point is roughly 45 degrees, This means that the vertical travel I'm measuring ignores the horizontal travel as the swingarm compresses.  The other issues are I set the front fork at 5 inches when leveling the bike upside down.  The stock 4 inch setting would have had the pivot angle less severe yielding more vertical travel.  I didn't think of that till after doing everything.

Methodology 2:

Same setup as above.   I'm trying to minimize the horizontal travel so I need to bring the measurement points close to being level to the pivot.  This method should bring the travel to a more vertical position.  I measure the distance from the pivot to the contact point on the tire.  Angle from the contact point to the tire contact point is about 45 degrees.  I lock the rear tire in place for this test.  I mark a point on the wheel that is the same distance from the pivot to the tire contact point that is slightly higher than the pivot.  That point should be below the pivot when I fully compress the swingarm.  I remeasure everything and get just under 6 inches.  I really though this methodology was the most accurate.  Now I'm not so sure.

My tests ignores the travel of the an arc and that the contact point changes as the suspension compresses.  I maybe wrong but I thought the difference would be minimal.

Thought?

I have a Cannondale Gemini with a similar pivot design.  I’ll measure that using the same methodology when I get a chance.

[Matno]

Kudos for your effort. We are an obsessed bunch, are we not? I think I prefer to just enjoy my ignorance and assume that the travel is what I think it is. I just stick with the calculations that others have done using pivot point, mount geometry, math that I could do in junior high better than I can now, etc.

Subjective tests like the ones you did can yield weird results. If I grab my saddle and my rear wheel and flex from side to side, it feels like there is AT LEAST an inch of sideways flex. (I've done the same with all three carbon swingarm 5000s in my family). However, when I securely immobilized my frame and tried to flex the rear wheel/swingarm, I got NO movement. Go figure. I can definitely feel it when I'm riding, but I got used to it a long time ago. Kind of like "suspension" for those crooked landings I seem to be fond of...

[Ionit]

This Guy says it's 4.7 inches. I find drawing a scale model helps. This way you can check each measurement with some good old visual evidence.

Hey and what do you know here is a link to an evo for sale.
http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&category=98083&item=7170667515&rd=1&ssPageName=WDVW&tc=photo

[jimbo]

Kudos for your effort. We are an obsessed bunch, are we not? I think I prefer to just enjoy my ignorance and assume that the travel is what I think it is. I just stick with the calculations that others have done using pivot point, mount geometry, math that I could do in junior high better than I can now, etc.

I incline to agree with you.  I initial thought it was going to be easy.  Didn't think about all the angles I would have to deal with.  

I think the ass (feel) method is best.  My ass tells me the Gemini has more travel.  Unfortunately, I still need to test the Gemini because I so damm curious of my weird results with the Evo.

I guess we can't let things alone.  I've got a new DH wheelset with Maxxis 2.7s and Kenda 2.6s ready to mount.  We got a DH race in 2 weeks so I can't wait to see how these compare to the freeride set I use now.  I'm raiding my Evo because I got my Planet-X with adjustible chain stay ready to go.  My buddy has be bugging me about the Planet-x because he wants to see how much easier it is to manual the sucker in the shortest setting.   I more curious about how it jumps at the jump park.  I want to covert my old steel hardtail to a single speed...............................

It NEVER ENDS!!!!

[Simon]

According to the linkage simulator programme I'm using an Oz with a standard i2i shock fitted using a

1.5" stroke yeilds 102mm (4") travel

1.75" stroke yeilds 118m (4 5/8") travel

2" stroke yeilds 134mm (5 1/4") travel

looking at the programme it measures the distance of the full arc travelled at the rear axle centre.

Simon.

[rapiddescent]

it's pretty hard to measure travel isn't it!  The way I did it all those years ago with the long travel kits was to remove the spring and measure the vertical travel using a pen inserted into the rear QR that draws on paper!  This is whilst having the whole frame in a bike stand.

The assumption is of course that the spring itself has enough compression length to use the whole shock stroke.

An 856 gets about 2.8" for example.

callum
rds