Easy 1" threaded to 1 1/8" fork mod

[Indyjps]

So, I had a pile of parts laying there, and it occurred to me that this may work.
1" threadless is a pretty tight slip fit into a 1 1/8 suntour fork headtube. Chop off the 1 1/8 headtube, slide it over the 1" headtube, some rosette welds. Done.
Measure and proceed on your own, tubing wall thickness may vary.
Lots of these low end mtn bike forks hanging around as donors.

BTW, the fork legs are 25.4 and appear to industrial chromed, also a good donor size.

 

[Indyjps]

My general plan is the cut the alum collar off the suntour fork, and get an extra long 1 1/8 steer tube. Convert a 1" threaded to an extended ht (ht corrected) 1 1/8 threadless fork.

This should let me clunker a former suspension bike frame to rigid fork and not have to use shorty cranks. Have to figure out how to secure the fork bearing crown up the tube. Dont know if it will take enough heat to weld without warping.

It might be ugly. We'll see. Might look OK if I can figure out a springer mount below the headtube instead of above.

 

[Lindsay97]

You could try using headset spacers under the fork bearing crown or even some tube with 1 1/8 internal diameter. There's also the option of running a second thread less stem under the headtube to use as a springer mount.

 

[GuitarlCarl]

You could try using headset spacers under the fork bearing crown or even some tube with 1 1/8 internal diameter. There's also the option of running a second thread less stem under the headtube to use as a springer mount.

+1
I have used spacers under the crown race too. Can solve a variety of issues, from crank scraps, to a cleaner head set look, to just kicking the whole stance up n' back a bit.
So, sleeve the whole thing right? Drill a couple/few holes in the sleeve beforehand and weld it to the inner... That's what you meant originally eh? Then it's all 1 1/8th parts... Hmm, what does the crown race ride on? A nice fat 1" headset washer or two. Cut the 1 1/8th sleeve into three pieces, lower 3rd for the spacer to gain the height you lose without suspension, fat 1" washer next then the 2nd sleeve to hold the 1 1/8th race sitting on the washer, then the 3rd sleeve to fit your headset height! I've got a lower end Trek with a heavy suspension fork I'd love to remove... this is the ticket for guys with plenty of mismatched parts... Thanks for letting me think out loud on your thread.


Carl.

 

[Indyjps]

Still a work in process. Open to ideas. Was condidering keeping a piece of the original alum fork there for spacer height and to retain race.

 

[Captain Awesome]

Was considering keeping a piece of the original alum fork there for spacer height and to retain race.

What I was picturing in my head. Not sure how well it would work out

 

[Kevin Burns]

Im not sure what your trying to do. I take it your trying to use a 1 1/8th inch fork steer tube in a 1 inch head tube? if that is it, this is really simple. In BMX we used 1 inch head sets at one time long ago, now everything is 1 1/8th so what we have is a 1 inch head tube, a quill stem, and a 1 1/8th fork and head set.
This is easier than it reads.

1) The quill stem.
Remove the quill stems long bolt and the compression chuck, replace the quill stems long bolt with a longer bolt to clear the bottom of the forks crown. The bolt you get should be the same threading as the quill stems long bolt and chuck.

2) Quill stem modification.
Cut the quill stems shaft/neck at a greater or shallower angle to allow the chuck enough room to contact the inner diameter of the fork steer tube.

3) Reassemble the quill stem bolt and chuck.
Now put the longer bolt into the quill stem, screw the chuck up to the bottom of the quill stems steer shaft (neck) the bolt will be long so don't worry.

4) Inserting the quill stem into the 1 1/th fork steer tube.
Place the quill stem into the fork as normal while holding tension on the long bolt to keep the chuck up to the bottom of the quill stems shaft but keep it loose. Now tighten it up so the quill stem is taught against the fork but still loose. Add a washer, and a nut under the forks crown and tighten it up. What ya just made was a compression bolt to tighten up the stem inside a 1 1/8th fork and the head set.

I don't know what size your head tube is. I assume it is 1 1/8th. I use a 12.00 head set because I don't need the threaded 1 inch being the mod I just did. if your frame is a 1 1/8th this head set is similar to a 1 inch track head set in that it comes down over the top bearing, perfect for compression-ing. Neco 1 1/8" Chrome Threadless BMX MTB Headset w/ star nut. This head set will center everything perfectly. This head sets top downward facing cup has a grove machined into it that a 1 inch volcano will fit perfectly into thus centering the bearings and fork as well.

I use the 1 inch top volcano bearing race upside down on this head set. It works.

or if you want too,

1 inch head sets will work in a 1 1/8th inch head tube as well by using the 1 1/8th inch cups.
take the 1 1/8th inch cup and cut off the cups matting walls "the round part that goes into the frames head tube." They make the perfect spacer for 1 inch down conversions from 1 1/8th.
Also the loose ball headsets will usually run on the 1 1/8th fork bearing seat, if it is a little tight no worries the cups ball bearing surface will wear in and it will free up.

I hope that's what your trying to do. if not still good info for someone.

 

[Kevin Burns]

If your trying to use a 1 inch threaded fork in a 1 1/8th head set that's really easy.
Buy the headset I mentioned above. Only use the top bearing cap, and use the 1 inch volcano upside down. Place the 1 1/8th head set top cup over the bearing and use the 1 inch head set volcano upside down crew the it onto the fork upside down. This will tighten the head set while aligning everything, use the washer as normal and top lock nut as normal boom your done.

 

[Indyjps]

Ive gone that route as well. If you dig thru 1 1/8 cups and 1" cups. A 1" cup will almost seat into a 1 1/8 cup. A little filing and a bench vice will seat them together. Your choice if you want to add some weld.

I havent worked on this any further. The goal was to use 1 1/8 steer tube on 1" fork to keep 1" fork look and use a modern 1 1/8 stem.

I have tried to slip this over another set of forks and it wouldnt go, so its not a slam dunk.

Ultimately, this will be a leaf spring- springer with 700cc 1" main fork and 1 1/8 headtube, 1 1/8" stem. Long fork to take up height on a previous suspension frame. Its definately the long path and im recreating the wheel, for no good reason other than I feel like doing it. But it will be a new aluminum frame dressed out as an old school bike.

 

[Indyjps]

Finally worked on this again as I was cleaning up the garage for winter. Steer tube from mtn bk forks with the fork legs cut off with cut off wheel. Started to file to shape. This lets me keep the bearing seat. Ill leave the aluminum "plug" to gain height to use these in place of a suspension fork.