Making a custom spacer for under the steertube

[whereswally606]

So I have a scott ransom 10 which is a carbon frame. I have its alu cousin the ransom 30 with some 200mm bomber stantions which give the correct DH geometry. I bought a carbon fibre fork (non suspension) and this has a really long head tube which is good. My desire is that I want to space the headtube under the steerer tube to make the geometry and thus ride of the frame back to where it should be.



I cant find any examples of people doing this online, is my google search fu out of whack or am I the only one stupid enough to try this.

 

[ferret]

Placing a spacer under the head tube will dramatically increase the stress that the fork's steerer is subjected to.
Not safe.
Even if the bike's static geometry is identical, a rigid fork will ride very differently to a 200mm travel fork, so I don't think there is purpose doing it regardless of the safety concerns.

Avner.

 

[2old]

+1 especially with CF; you might consider altering tire width (bigger front and smaller rear to effect what you need.

 

[whereswally606]

if the spacer was ill fitting/fitted i'd agree however if it was machined from alu and held tight all in I don't think it would compromise the strength other than increasing the moment about the pivot which is not to much due to the angle. The ride might not be the same as with suspension forks at the front but at least the action of the rear shock would be kept similar to the original as it is preserving that horizontal line which you can see from front to read axle through the bottom bracket. Without using the spacer this line ends up above the bottom bracket and the rider feels like they would easily go over the handle bars.

I thought about changing for a 24" wheel but I like to pedal and this would affect that not only through changing the cadence but the height of the pedal from the floor/ kerb increasing the chance of hitting either with the pedals.

I feel like this is one of those questions where I will only find out through having ago.
I once shimmed a 1 inch to a 1 1/8inch steerer on this frame (girvin girder style fork) that was an awful idea and it was truly dangerous. This idea is different and I believe a lot safer.

 

[WoodlandHills]

Are you talking about a spacer under the crown race of the fork? If so what about one of these:
Salsa Cane Creek +3mm Crown Race

https://www.universalcycles.com/shopping/product_details.php?id=68918.

I have used them with no ill effects. It's not much of a lift, but I can feel it in the handling.... At least I think I can!

As far as there being additional stress making the the whole thing unsafe, this is SOP when converting a 1 1/8" straight head tube to accept a tapered 1 1/2" steering tube. Sometimes just the Cane Creek EC 40/44 lower bearing cup will not lower the assembly enough and the tapered steering tube on the fork will contact the inside of the straight head tube: moving the steering tube 3mm lower by using the Salsa crown race fixes this. Cane Creek and Salsa are both reputable companies with a lot to lose if they sold unsafe products......

 

[ferret]

The danger is the moment increase.
The moments on the steerer are caused not only from the weight of the rider acting on the angled fork. They are also caused by hitting bumps (especially in a rigid fork) and from braking.

If you want to safely decrease the chances of going over the bars, try the following:
Reduce rear shock sag (less pressure ).
Move the saddle backward on its rails.
Raise the stem with spacers/fit a raiser handlebar.

You can fit a 29" front wheel if you are looking for an "out of the box" solution.

Avner.

 

[Keith Pegg]

Not sure however you may find a 29" fr fork to replace the 26" and also for more use a 29" wheel.

Good Luck,

 

[whereswally606]

Those spacers are $20 each = ouch. Yeah agreed a 29'er fork with or without the 29er wheel might get me there. At the moment I am going to just put some bombers on it and sort the rest of the bike out just to get it rideable. Later I can do this. Might by even 3d print my own carbon fibre spacer. We shall see. Thanks everyone for the advice I even talked to my local bike shop north west mtb just off roscoes roundabout near stockport. They were pretty helpful too.

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