spacer at bottom of headtube?

[jimcav]

i think CK might make something, anyone know the proper term?
i think it would effectively slacken HTA but not sure by how much. if i put a 1cm spacer between fork and HT, how much would i be changing things--would going from existing 43 rake to a 45 rake fork offset it?
thanks
jim

[DRZRM]

CK makes a tall baseplate/race, it adds 5mm height, and they sell them directly for $20.

I've also seen a alu press in extender like the old Serotta press in that can go under the head tube, can't remember who makes it though.

[jazznap]

Ventana also makes one. I used one for a mtn bike that had fork clearance issues.

http://www.cambriabike.com/shopexd.asp?id=86829

[DRZRM]

Right, here is the one I was thinking of. "Makes most unspinnable bars spinnable"!!

http://eighthinch.com/products/freestyle/headtube-extenders/

[Dave]

5mm would change the HTA by about .3 degree and change the trail by slightly less than 2mm. 2mm more rake would restore the trail to it's former amount.

Trail = R/tanH - (rake/sinH)

[jimcav]

5mm would change the HTA by about .3 degree and change the trail by slightly less than 2mm. 2mm more rake would restore the trail to it's former amount.

Trail = R/tanH - (rake/sinH)

so frame was originally designed for 43 fork, i have a 45 fork, so could do 5mm spacers on bottom and all is right again. was hoping for 10mm but thank you very much
jim

[jimcav]

CK makes a tall baseplate/race, it adds 5mm height, and they sell them directly for $20.

I've also seen a alu press in extender like the old Serotta press in that can go under the head tube, can't remember who makes it though.

thanks

[jimcav]

Ventana also makes one. I used one for a mtn bike that had fork clearance issues.

http://www.cambriabike.com/shopexd.asp?id=86829

thanks for the info
jim

[Brian Smith]

There is a lot of support out there for the idea that maintaining a constant or near constant value for calculated (or "geometric") trail maintains the same steering feel or "handling" from one conglomeration of component pieces to another. I don't think that's always true. I'm not sure what kind of issue your 10mm spacer is a workaround for, and maybe it's a bigger issue than whatever the steering feel or "handling" will be like after the change, but I would offer another point of view: The only fork change that will geometrically produce the same steering feel or "handling" after the addition of 10mm more of spacer or headset stack on the bottom of the head tube is a fork of the same offset (some say "rake") but 10mm shorter in length measured parallel to the steering axis. In practical terms, it's not generally possible to source such variety of off-the-shelf forks, and there may even be physical reasons that a 10mm shorter fork can't be made.

Internet threats aside, it's not really a dangerous proposition to try out riding on a fork that is the "wrong" choice, it might just be instructive. All of the internet wisdom out there may be an obstacle when evaluating how the new fork works, so I thought I might suggest that the substitution may be changing more than you expect if your method is simply maintaining calculated trail.

[SteveV0983]

If you want to pick up the King one, here it is at Aspire Velotech. These guys are really good.

http://www.aspirevelotech.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=AVT&Product_Code=PHS529&Category_Code=CKBP