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Converting a 20 inch frame to a 24 inch?  RSS Feed

#1 2017-02-21 8:48am

osbmx
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From: Dallas, TX
Registered: 2016-12-12
Posts: 60
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Converting a 20 inch frame to a 24 inch?

This may be blasphemous. But, I really want a retro 24 Mongoose gussetted frame. Nobody that I am aware of does this. So, I was considering taking a basket case frame and doing this.

Obviously the forks would be simple. just purchase a 24 inch threaded set. Then I assume find a talented fabricator/welder to modify the rear. Has anyone here attempted this?

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#2 2017-02-21 9:04am

muol
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Re: Converting a 20 inch frame to a 24 inch?

This member got his Hutch XL-24 stretched out to 26":

http://bmxmuseum.com/bikes/hutch/85413

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#3 2017-02-21 9:16am

psychoduddycycles
Pro MemberWAYYYY in the red since 1983
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Re: Converting a 20 inch frame to a 24 inch?


Sometimes, to make a paradise, you gotta release a SERPENT.

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#4 2017-02-21 12:19pm

osbmx
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From: Dallas, TX
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Re: Converting a 20 inch frame to a 24 inch?

Oh WOW! Anyone know of someone who can do this for hire?

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#5 2017-02-21 1:19pm

saskbmx
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From: Regina, Saskatchewan Canada
Registered: 2014-06-23
Posts: 4521

Re: Converting a 20 inch frame to a 24 inch?

that example is really cool.

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#6 2017-02-21 1:34pm

socaldude
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From: Waipahu, Hawaii
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Re: Converting a 20 inch frame to a 24 inch?

Those two examples don't look too bad. If you have someone do it, give them an actual 24" frame you like as well. Most of the customs just lengthen tubes and don't take into account b/b drop. If you just want it to look bigger, that's cool. But if you want it to ride nice, make sure it's done right.


Duane@shootsbrah.com

Would love to find my old Dirt Bike.  It was stolen in Pompano Beach, Florida in about 1996.  It's a '92 with the block graphics on a Green frame.  Pitchforks, Slam bars, GT (DK-style) stem and GT/Profile cranks.  Superlace hubs.  Would really love to put this back in my collection.

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#7 2017-02-21 5:55pm

rareair
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Re: Converting a 20 inch frame to a 24 inch?

Contact Johnny True Torch (Santa Ana, Ca). He does custom stretches quite a bit.  His website- http://truetorch.com    He's also on this site as member: bwheels


Wanted: Sugino bottom bracket for Redline 400 cranks
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#8 2017-02-22 12:15am

Crashman
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From: Mount Pleasant, MI
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Re: Converting a 20 inch frame to a 24 inch?

First of all, don't do it. The problem is that most people who have done it have ended up with a raised bottom bracket, and that makes a shitty BMX bike (though lots of MTB guys like it for rock crawling and stump humping or whatever they call it).

Now, if you're going to do it anyway, you're going to want to drop the bottom bracket two inches, to make up for the extra two inches of clearance from the axle to the ground. I guess you could do that without altering the angles between the top tube and down tube by lengthening the front end around 5 or 6 inches...

Did Mongoose have a shorter 20" frame? A shorter frame would have a steeper downtube angle so you don't have to lengthen it as much to drop the bottom bracket.


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#9 2017-02-22 12:17am

Crashman
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From: Mount Pleasant, MI
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Re: Converting a 20 inch frame to a 24 inch?

Oh yeh, from there you'd want to lengthen the seat stays by 2", but the chain stays by like 3"-4", to raise the axle slot in reference to the bottom bracket.


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#10 2017-02-22 12:18am

Crashman
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From: Mount Pleasant, MI
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Re: Converting a 20 inch frame to a 24 inch?

Or, you could just make your own frame and get shorter triangles at the right bottom bracket height by changing the angles of the tubes big_smile


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#11 2017-02-24 3:20pm

vwzx
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Re: Converting a 20 inch frame to a 24 inch?

You could also get a modern frame that looks similar, have a gusset welded to the frame and get an old school sticker set for it. Just a thought.


83 Skyway TA
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#12 2017-02-24 3:24pm

Crashman
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From: Mount Pleasant, MI
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Re: Converting a 20 inch frame to a 24 inch?

If I were building a 24" frame as a tribute to a 20" frame, I'd replace the 1" tubing with 1 1/8" to make it look more proportional.


Wanted: Inexpensive lot of cheap 7/8" bars for grandkid's bikes. I will paint as needed.

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#13 2017-02-24 3:24pm

vwzx
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Re: Converting a 20 inch frame to a 24 inch?

My plan was to get a mid school mongoose menace 24" and sticker it with the early 80s prism mongoose decals. You can still run the old school parts with it. It doesn't solve your gusset need though.


83 Skyway TA
88 Free Agent cruiser
89 Auburn
92 PK Ripper

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#14 2017-02-24 3:30pm

Shotgun
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From: Tortugas Pines
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Re: Converting a 20 inch frame to a 24 inch?

Just get a Mongoose Two Four, have a gusset fabricated and weld it in.http://uploads.bmxmuseum.com/user-images/207817/img_472758b0c14c2f.jpg

You could make a solid gusset and sticker it up as a Jag 24 inch cruiser. That would be really cool as the Jags are looptails with the same drop outs as the Two Four:
http://uploads.bmxmuseum.com/user-images/207817/img_472858b0c1f39d.jpg

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#15 2017-02-24 3:39pm

BMX*Racer*1983
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From: New Jersey
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Re: Converting a 20 inch frame to a 24 inch?

C4 Chip can do this


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#16 2017-02-24 5:49pm

ricar
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From: Waterdown On Canada
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Re: Converting a 20 inch frame to a 24 inch?

You would be better having a frame made to your specs. Any frame builder should be able to copy gussets to a reasonable degree. Maybe not stamping or laser cutouts, but the basics and depending on what you want to spend. Also if you need 4130 or can get away with DOM. It would be pretty awesome to build a frame to look like the old goose but with modern strength.


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#17 2017-02-24 7:51pm

rareair
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Re: Converting a 20 inch frame to a 24 inch?

vwzx wrote:

You could also get a modern frame that looks similar, have a gusset welded to the frame and get an old school sticker set for it. Just a thought.

That's exactly what I'm doing to one of my mid school cruisers.  I've welded gussets on the head tube, fabricated an old school brake bridge to mount side pull calipers (was cantilever type) and even machined a 1" seat clamp to fit the 25mm mast.  You can see my project here-
http://bmxmuseum.com/bikes/diamond_back/90617

  Wish there was a way to mount an old school stem to a threadless fork.  But it's a fun project until I can gather up enough funds to have Johnny True Torch custom stretch one of my Turbo's cool


Wanted: Sugino bottom bracket for Redline 400 cranks
Wanted: Diamondback Turbo stamped seat post
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#18 2017-02-25 8:13pm

Minx20
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From: Delray Beach, FL
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Re: Converting a 20 inch frame to a 24 inch?

vwzx wrote:

You could also get a modern frame that looks similar, have a gusset welded to the frame and get an old school sticker set for it. Just a thought.

This /\

An example of a modern frame that you could easily add gussets and other goose characteristics to would be Firemans 24

Take a look at my two / Six tribute bike and you can see how similar the geo is. The 24er is a good choice to use for what you want to do.

Last edited by Minx20 (2017-02-25 8:14pm)

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#19 2017-02-26 4:37am

DamageInc
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Re: Converting a 20 inch frame to a 24 inch?

I knew I had seen some cruiser builds in the past. I kept poking around because it was eating at me. One is the above listed 24, then there's these 2 26ers. Pretty cool stuff.
http://bmxmuseum.com/forsale/62415
http://bmxmuseum.com/forums/viewtopic.php?id=221959
http://bmxmuseum.com/forums/viewtopic.php?id=550498
http://bmxmuseum.com/forums/viewtopic.php?id=563909


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#20 2017-03-05 9:29pm

vwzx
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Registered: 2012-11-20
Posts: 529

Re: Converting a 20 inch frame to a 24 inch?

rareair wrote:

vwzx wrote:

You could also get a modern frame that looks similar, have a gusset welded to the frame and get an old school sticker set for it. Just a thought.

That's exactly what I'm doing to one of my mid school cruisers.  I've welded gussets on the head tube, fabricated an old school brake bridge to mount side pull calipers (was cantilever type) and even machined a 1" seat clamp to fit the 25mm mast.  You can see my project here-
http://bmxmuseum.com/bikes/diamond_back/90617

  Wish there was a way to mount an old school stem to a threadless fork.  But it's a fun project until I can gather up enough funds to have Johnny True Torch custom stretch one of my Turbo's cool

Very cool. I like it. I think pork chop sells tuff neck stems that look old school but are 1 1/8.


83 Skyway TA
88 Free Agent cruiser
89 Auburn
92 PK Ripper

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#21 2018-06-05 10:05am

snooze
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From: London, UK
Registered: 2008-06-06
Posts: 573
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Re: Converting a 20 inch frame to a 24 inch?

I have a 24" frame I'd love to stretch, anyone know someone in the UK?


Snooze * Wake up * Get busy

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#22 2018-06-05 6:04pm

Indyjps
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From: Chicago
Registered: 2016-09-07
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Re: Converting a 20 inch frame to a 24 inch?

http://www.ratrodbikes.com/forum/index. … 867/page-3

This guy is doing a run of 10 26" mongoose frames,  might contact him for a 24".


MTNBKSUK

Location: Chicago Burbs

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