Raising fork tubes in the clamps

Michael Moore

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While I have the 2014 CTX forks apart I thought I'd determine just how much the stanchion tubes can be pulled up through the clamps before things begin to touch.

With the top of the stanchion (not the cap, the actual tube) at 8 mm (5/16") above the upper fork clamp the fender just kisses the mounting bracket at the middle/bottom of the radiator. This is with clean/dry parts; with oil in the tubes the hydraulic lock of the bottoming cone on the damper rod might keep the sliders from coming up the last 1-2 mm.

The stanchions should be reasonably stiff but you should presume that a worst-case "braking while hitting a bump hard enough to bottom the forks" will cause them to bend back a little. The 35 mm Ceriani RR forks on my 500 Yamaha road racer would deflect 6-8 mm under heavy braking (on a smooth race track) and leave a bit of rubber on the front of the fairing. The CTX forks should be almost 2X as stiff as the Cerianis but there is an additional two hundred pounds of extra weight on the bike (and 50 pounds on the rider, sad to say) encouraging the forks to deflect.

There is room between the fender and tire (Michelin PR4) to accommodate a bit of deflection, but I'd stick with a maximum of 8 mm, why risk scratching the fender? :)

Of course, you should always confirm clearances when modifying your own bike and not go with what some guy on the Internet said.
 
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dduelin

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As a point of reference the forks on a NC700X can be raised 14 mm in the clamps and still not touch the fender to anything. If the fender has a fender extender installed the radiator mount at the center bottom just kisses the extender about 1" below the bottom edge of the factory-stock fender.
 

Michael Moore

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Yes. :)

But you've got to change about 1" (25.4 mm) of height to get about 1 degree of rake change. The CTX owners mostly seem interested, for those who are leg-length challenged, in lowering their bikes. I'm not sure how many of them would find 5/16" (8 mm) to be of significant help.

I've seen various people throwing out "it is OK to lower the bike this much" advice based on who knows what?

The compressed length of the forks and rear suspension is the same for both the NC and the CTX. The fork tubes and sliders are the same part number as are the suspension linkage parts. The NC damper has the same compressed length as the CTX, but more stroke/longer extended length to get the extra rear wheel travel. The NC uses a different damper rod and spring in the fork to get the extra travel there.

A CTX does not have an excess of ground clearance/lean angle at full bump (even worse on the DCT where the shift motor and things stick out more than on the manual shift bike). The NC has a more upswept muffler but both bikes route the exhaust under the same spot on the frame and the engine bits stick out in the same spots. The CTX foot pegs are very low and wide. The NC, with extra travel, rides higher than the CTX and will take a little longer before things start to drag, but if the suspension is bottomed at both ends I sure wouldn't want to be on either of them that has been significantly lowered.

cheers,
Michael
 

dduelin

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I'm curious...what does raising the forks do for you? Lower the bike? Change the rake?
I did some work in the forks that raised the ride height about 12 mm IIRC. In order to return the steering geometry to close to original I slid the forks up in the clamps. I'm also short so lowering the bike gets back some of what I did to raise it.
 
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