1" headtube with 1-1/8" fork adapter

[2Phast2Delirious]

I'm trying to use a 1-1/8 in MTB fork on a kids bike with a 1 in headtube, but couldn't locate any information in the forum. Has anyone here done this? I was quoted $300 by a local bike shop for parts and labor, but he assured me it would be much cheaper if I did it myself.

https://www.danscomp.com/mission-conversion-headset-black-11-8-mn2050blk/p1128265?gad_source=1&v=1121372

1 inch to 1 1/8 threadless conversion headset Retro Ryder | eBay

Retro Ryder Head Set. We get lots of queries in regards to this head set; will it work on a 97 gt Avalanche, or a 92 Rock hopper, or a 1982 Univega Alpina Uno etc. Hope you understand.

www.ebay.com

It's for my wife and children, who are all under 100 pounds and 5ft tall. My wife adores my sons Micro Surron eBike (Juanito), but hates the dirt bike look. She really wants this design.



Meet DookieCati...

 

[Ianhill]

I think the bike shop left you to it knowing that the rake of the fork is going to be extreme and the frame will likely snap even with only 100 pounds in weight on it.

The problem u got is not only is the headset cup the wrong size but the fork is way to long it adjust the angle of the fork in the headset if its too steep the frame will snap no doubt, the headset adapters are pretty rasy to come by but od advise getting a fork that suits the wheel size unfortunately sorry to bum out the idea.

 

[Chalo]

Note that the headset in your link is only for American sized 1" head tubes: old Chicago Schwinns and other American-made bikes, 70s-80s BMX bikes, and some beach cruisers. The vast majority of 1" frames won't accommodate that headset, or a 1-1/8" fork of any kind.
Are you sure that the bores of that frame are 32.7mm? 30.0mm and 30.2mm are far more common.

 

[2Phast2Delirious]

Are you sure that the bores of that frame are 32.7mm? 30.0mm and 30.2mm are far more common.

Here's what I measured. Please note I'm using a crappy tool from Harbor Freight.


Headtube outer diameter 34mm



Headtube Inner diameter 29.5



MTB fork O.D. 28.5




From SR Suntour website:

80 mm travel

Left Side
COIL w/ Preload Adjuster

Crown/Steerer
AC4C

Stanchion DIA. (Material)
28mm

Bottom Case Material
Al Alloy

Brake Mount (Max Rotor DIA.)
Postmount 160mm Direct / V-Brake

Steerer tube
1-1/8" (TS), STKM

Weight
2660g

Stanchion tube finish
STKM, Cr-plating

Axle (Option)
9-100mm Dropout

 

[amberwolf]

The danscomp link doesn't provide any specs for the races, so I don't know what their OD and ID are, and thus I don't know whether they could fit what you have.

It's pretty likely that their ID is designed to fit your fork, but they'd have to be VERY VERY thin walled races to fit between the headtube you have and the fork steerer, since the difference is less than 1mm. the picture on the site doesn't shows the wall thickness, but I imagine it is significantly more than that.



If it's the same unit as this
https://missionbmx.com/products/conversion-headset

then they don't have any specs either, and don't even say what sizes it converts to or from, except that it is for a 1-1/8" headtube...so it probably would not fit your 1" headtube.

PRODUCT RUNDOWN
Upgrade your standard 1 1/8″ headtube frame to an integrated style headset with the Mission Conversion headset! Uses stronger Campy type sealed bearings and includes dust cover cap, spacer, and steel fork bearing race.

PRODUCT SPECIFICATIONS
HEADSET TYPE: Standard 1 1/8"
BEARING TYPE: 41.8mm x 45 Degree
INCLUDES: Headset, Spacer, Star Nut, Fork Cap
WEIGHT: 5.3oz

The ebay link doesn't say it's wall thicknesses either, and the image doesn't show them, but if the headtube part of the races is the same thickness as the bearing / cap area, I doubt it would fit between tube and steerer.

EDIT: further down the page is a note

The internal diameter or I.D. that you head tube NEEDS to be for our product to work is:


32.5 mm​

So it can't fit your headtube.

 

[docw009]

With an ID of 29.5mm, and a 1 1/8" steerer being 28.575 mm, that leaves .4 mm for the cup's shoulders. Seems way too thin for me, You need someone to machine a pair of custom bearing cups that fit on the outside of the headtube.

Here's a steel fork with a 1" steerer tube. You could braze on some disk brake tabs.

NEW! ABSOLUTE 20" BICYCLE STEEL SUSPENSION 1 INCH THREADED FORK IN SILVER. | eBay

Steerer: Threaded 1" (22.2mm ID). Steerer Length: 200mm (102mm Threaded). Material: Steel.

www.ebay.com

 

[2Phast2Delirious]

then they don't have any specs either, and don't even say what sizes it converts to or from, except that it is for a 1-1/8" headtube...so it probably would not fit your 1" headtube.

Thanks for the link! I'm going to look for a headset adaptor of some kind. After spending roughly 30 minutes looking for every item and adapter, the owner of the bike business and his son declared that it could be completed. He's charging me so much because of his connections and expertise in finding unique parts. He did mentioned something about a custom bearing/headset.

 

[2Phast2Delirious]

Here's a steel fork with a 1" steerer tube. You could braze on some disk brake tabs.

I appreciate the link; I'll keep it handy. I've located several functional forks from China (Zoom brand), but I would really love to use these forks.

 

[amberwolf]

Another option is to change the steerer tube in the fork, but it's not something I've ever done.

When I was faced with this issue on CrazyBike2, I just welded a new headtube on of the right size. Lasted a decade of everyday use before I retired the bike, IIRC.

If your frame is steel, that's a relatively easy option, but if it's aluminum, it's more complicated.
https://endless-sphere.com/sphere/t...arts-cargo-ebike-crazybike2.12500/post-390482

 

[amberwolf]

Here's a steel fork with a 1" steerer tube. You could braze on some disk brake tabs.

https://www.ebay.com/itm/393061191214

As low-end as the Suntour fork he already has is, it is lightyears better than that ebay fork, as a functional suspension. I've had both types, and the ebay one would probably work better if it were welded together so it can't move at all than using it as a suspension.

 

[Ianhill]

The major issue i see is that suntour fork is for 27.5 wheels and theres a 16 inch in there by looks, so the front end will be much higher than the standard fork altering the angle of the headset tube putting the frame under massive stress.

Ive seen downhill frames snap juat going from a 140mm travel to 170mm thats not even half the increase this fork would give you.

My fix would be get a kids bike with a steel frame and the desired fork size cut the headtube off yours swap them over witb the donor bike and run its bearings headset cups the lot but please dont try fit the suntour it will end in tears.

 

[2Phast2Delirious]

The major issue i see is that suntour fork is for 27.5 wheels and theres a 16 inch in there by looks, so the front end will be much higher than the standard fork altering the angle of the headset tube putting the frame under massive stress.

Ive seen downhill frames snap juat going from a 140mm travel to 170mm thats not even half the increase this fork would give you.

My fix would be get a kids bike with a steel frame and the desired fork size cut the headtube off yours swap them over witb the donor bike and run its bearings headset cups the lot but please dont try fit the suntour it will end in tears.

Thank you for keeping an eye out for me. You might be correct, however the bike mechanic examined it with the swing arm attached and declared that it would work without breaking. It is only slightly taller than the original forks with 18-inch tires, about 4 to 5 inches and is similar to the Schwinn Stingray Mantis and OC custom chopper bikes (he also showed his custom low-rider bike to me, complete with an unusually tall fork.). It will be used for short rides in parks and on trails once or twice a month. If I do go through with it, I'll double-check every time I ride it. May be I'll add some welding for support.

Don't let my pseudonym fool you; I am not a reckless speed demon. Many of my eBike builds are street-legal/semi street-legal and more for show than go, haha. DookieCati will be powered with a 36v/48v 350w/500w 15A controller with a top speed of 15-18mph.

The wife wants to ride this at the upcoming ES8-Con event in a few weeks since we had so much fun at the last one.

 

[Ianhill]

I attend something simular in uk around 10000 people attend yearly, wish u the best with it and fingers crossed she gets to ride the bike and have a blast keep on modding fella sure u get something sorted with it keep us updated

 

[2old]

Observe DW's numbers above again. I wouldn't dream of attempting something so sketchy on the front end of a bike considering the potential ramifications of failure.

 

[PaPaSteve]

Have you considered downsizing the fork steerer tube from 1-1/8" to 1" ?

1" steerer

You may need a crown race ring to fit the bearing race

or

new Suntour fork

 

[2Phast2Delirious]

Have you considered downsizing the fork steerer tube from 1-1/8" to 1" ?

1" steerer

You may need a crown race ring to fit the bearing race

or

new Suntour fork

I appreciate the links and terms very much. I have to admit that I am a bit remedial when it comes to custom bicycle parts and am still learning about them all. It appears to me now that the bike shop will undoubtedly replace the fork steerer and crown race ring.

I will be attempting to remove the fork steerer.


Thanks again!!!

 

[PaPaSteve]

I appreciate the links and terms very much. I have to admit that I am a bit remedial when it comes to custom bicycle parts and am still learning about them all. It appears to me now that the bike shop will undoubtedly replace the fork steerer and crown race ring.

I will be attempting to remove the fork steerer.


Thanks again!!!

There will be YouTube videos showing the steerer being pressed out the bottom of the crown.
It may require some cutting or machining of 1-1/8" steerer to accommodate the 1" version . . . making an adapter of sorts.

 

[Chalo]

There will be YouTube videos showing the steerer being pressed out the bottom of the crown.
It may require some cutting or machining of 1-1/8" steerer to accommodate the 1" version . . . making an adapter of sorts.

When I've replaced a 28.6mm steer tube with a 25.4mm one, I have to turn a whole new steerer on the lathe so I can get the (usually 30mm) fit to the fork crown, a 26.4mm crown race seat, and 25.4mm outer diameter all on the same tube. As often as not, I've started with a solid rod so the highly stressed lower end of the steerer can be extra thick walled. Like I'll drill the bottom few inches out with a 1/2" drill, then come in from the other end with something between 3/4" and 7/8".

Mostly in the past I used vintage suspension forks with bolted crowns, but I have used a hydraulic frame press to push out old steer tubes and install new ones.

This particular bike is so goofed up, with the fork loaded at such an unfavorable angle, that it would be a good idea to make a solid steer tube to minimize its chance of bending. Also those suspension forks aren't going to suspend anything other than a frontal impact.

 

[Papa]

As often as not, I've started with a solid rod so the highly stressed lower end of the steerer can be extra thick walled.

Not sure what the lower steer tube wall thickness (at the crown) is for a budget 1" suspension fork, but I can say that a quality 4130N 1" steer tube inner walls in road forks are typically tapered (thicker at the crown, thinner at the stem), Approx. 2.70mm at the crown and approx 1.5mm at the top. Additionally, Gardner Martin's Production Tour Easy LWB 'bents used road forks w/1" steer tube - combined with 58* of steer axis and approx 2.5" of fork offset. This combination did not seem to over stress the steer tube, but the fork blades just below the crown started developing cracks. Switching to unicrowns solved the problem.

Corrected error..

 

[PaPaSteve]

Pressing the 1" steerer out of the original fork crown could be a good start.
Theoretically, the original is strong enough for the job.
Make an adapter by removing and machining / cutting the lower portion of the 1-1/8" steerer so the 1" presses into it.
Then press the new assembly back into the SunTour crown.

While this image appears to show a large fork angle it could simply be an illusion.
Note the seat angle and an angle mismatch between the steerer and head tube.

 

[2Phast2Delirious]

While this image appears to show a large fork angle it could simply be an illusion.
Note the seat angle and an angle mismatch between the steerer and head tube.

Here's a more accurate angle of the steerer tube and headtube. There will be a slight angle because I'll be using a 14" eBike swing arm/rear assembly... unless I find a larger swing arm



Here is the OG swing arm. Do you know the name of this type of swing arm or a specific bike that uses this mono suspension swing arm? It is similar to the Stealth Bomber.

 

[amberwolf]

Note that if you want to reduce the angle the fork will be at, back to something closer to what it originally was, and also reduce the front end height, you can build clamp-on dropouts to put on the fork at the height the axle of the wheel needs to be to put the front end height back to original.

I did this on my first 'bent build ReCycle, though I welded them onto the steel lowers instead of clamping them on, as there were no 20" forks available to me that had any suspensive properties at all, but I did have a crappy 24" fork (very similar to the 20" fork linked by docw0009). To use my 20" wheel in it and still have rim brakes, and keep the front end where I wanted it, I simply put dropouts where I needed them, leaving the originals still there.

I never finished the bike so it never got any long term testing, so I don't know if it would've worked ok. (one thing I didn't know anything about then was trail, and it probably changed that. I don't remember how the trail worked out and don't have any locally stored pics of it anymore. If I find any on the old Electricle blog pages I'll link or edit them into this post. )

I did use the fork itself on CrazyBike2 (mounted backwards for reasons I don't recall), but I don't think I ended up ever trying the added dropouts as I was using the size wheel the fork was for.

EDIT: found the psot with them. Keep in mind I knew very little of actual bicycle design at the time, so it's pretty likely there are serious flaws with it...

Pics Of Parts, and Progress

I'm still working out a few things, but today's post includes pics of progress on the recumbent-from-scrap bike, as well as pics of donor fr...

electricle.blogspot.com

 

[Papa]

I'm dubious you'll be able to determine accurate steering geometry with half-a-bike. It really needs to be, at lease, partially assembled and sitting on both wheels, on a flat and level surface.

 

[PaPaSteve]

Geometry . . .
Longer forks will 1) add more wheelbase and 2) more castor ( trail ) which in one way reduces the weight on the front tire but secondly the longer castor adds more steering torque into the handlebars so probably a minor overall change in actual function.
Very likely the rider will adapt easily especially if it's a mod they ( she ?) requested.
A top level rider who is takes the maximum from the tires might not appreciate this set up.

 

[2Phast2Delirious]

@PaPaSteve @Papa @amberwolf
You can see why I had to acquire larger forks by looking at this updated photo of Sir-Juanito (mini SurRon), which has an identical setup with the stock 18-inch forks. We felt that it should be higher even though we initially had 20". I think that 24" would be ideal, but we decided to go with 28 instead, hehe. However, I am a novice, so feel free to correct me.

@Chalo When it came to Juanito's pedal to seat ratio, you were 100% accurate. "How TF am I suppose to pedal?" my wife asked as soon as she sat down on the bike. Forgot completely that these weren't the original pedal cranks. I'll order the shortest BMX/MTB cranks I can find, but if you have any recommendations for a great brand, style, or size, please share them with me!