Granny’s Nightmare – HOW TO – Make a bicycle chopper

Energy & Sustainability
Granny’s Nightmare – HOW TO – Make a bicycle chopper



AtomicZombie (who we posted about yesterday) sent in this great bike project – You know what really irritates the heck out of me? I drive all the way out to the dump, pay my five bucks to get in, and the only bikes laying around are those goofy granny bikes from the late 1970’s. Dog, what’s the deal? I need some new parts! Ok, enough whining, it’s payback time. A real chopper artist can chop any bike, even this crusty old codger cruiser. In fact, the more I looked at the bike, the more I thought it would be a sweet ride. Check out all that chrome, look at that long spindly frame, yeah, I could make this happen…

The how-to is a great a step-by-step and has dozens of photos!Normally, I do not even bother with these frames because of their “lugged” construction. Lugged frames are not really welded at the head tube and bottom bracket, they are press fit and brazed. Because of this, you cannot really salvage the head tube or the bottom bracket, and this makes the frame useless for parts normally. Even the rims are those goofy 27- inch size, too big for a mountain bike tire. Because I was planning to hack this granny cruiser into something evil, I would be keeping most of the frame in one piece, so the project was still doable.

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Chop this bike? Was I losing my marbles?

“Turn down that devil music, you crazy kids!” I could hear the bike talking to me. I thought I’d better rip it all apart before I start wearing a helmet and worrying about brakes! Photo 1 shows the old fashioned bike before hacking. These styles were easy to find at the dump or at yard sales.

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Reduced back to a pile of parts.

Here is the donor bike, taken apart for chopping. Even though this bike is older than time itself, it came apart very easily, and the chrome parts have only slight surface rust – easy to clean with steel wool. I will be using all of the original bike, as the theme for this chop will be Granny’s Nightmare!

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Fork legs amputated.

This chopper will have long forks and a slightly modified frame when completed. I did not want to change the bike so much that it loses all of its original look – the idea is to make it radical yet show its roots. This photo shows the original forks with both legs amputated right at the crown. It should be easy to build a triple tree from these forks as they are made from heavy mild steel. Back in those days, they knew how to build a bike, not like these young “whipper-snappers” today, sonny.

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Cut the ends of the forks, but save the legs.

I used the original fork dropouts, so they were cut leaving enough neat to weld to the new fork legs. Save the original fork legs, though. With those nice curves, it should be easy to integrate them back into the frame for a unique and classy look. Both dropouts should be cut as close to the same length as possible in order to insure wheel alignment.

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A pair of 4-foot long conduit tubes.

Since the long forks are the focus of the bike, and the frame adjustments will be based upon them, they are made first. I started with a pair of 4 foot long 1 inch thin walled conduit lengths as shown here. Four feet is plenty long, and if I made them much longer, radical frame manipulation would be necessary in order to prevent the “instant wheelie” effect.

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Grind the edges of the fork crown.

The original fork crown is used as the base of the triple tree. The new fork leg extension tubing will be welded directly to the ends of the crown, so it should be ground slightly to allow for easy welding. Do not take too much metal out, just enough to make a good weld that will cover 1/3 or more of the new tubing’s diameter. If you ground too much out, the fork legs would be too narrow for a front wheel, and major warping would occur to the conduit while welding.

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New fork legs tack welded in place.

Once both fork crowns are ground out, and both fork leg extension tubes are exactly the same length, lay the unit on a flat surface and tack weld both fork legs into place as shown here. Use only one solid tack weld per leg, as you want to be able to align the tubes as the front dropouts are positioned in the next few steps.

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Bolt the dropouts to the front hub.

To get the dropouts aligned in the proper place at the ends of the new fork legs, first bolt them to a front wheel as shown here. They should be secured tightly and both at the same horizontal angle. Also, make sure that flattened end that holds the axel is not bent, if it is pull it straight with a pair of pliers. The distance between the dropouts is usually 5.5 inches for a front wheel. These old bikes may be even less.

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Welding the dropouts to the fork legs.

With the fork legs tack welded to the fork crown, and the entire unit laying on a flat surface, place the dropouts onto the fork legs as shown here. First tack weld the dropouts in place, then check alignment visually by looking at the unit from all angles, especially lengthwise. If there is any misalignment, it will be easy to correct at this point with a small hammer. If you are satisfied with alignment, weld all of the fork starting with the dropouts and finishing with the cork crown and legs. Check alignment along the way as you weld.

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The bottom bracket is a little too high.

Once the forks are solidly welded, place them into the frame to have a look at what you have so far. Most likely, the bike will seem to lean back too far, and the bottom bracket will be very high. Because of the extreme fork length, the frame has been pulled backwards creating the “skyscraper” style chopper. Although the bike would be readable in this configuration, and it may indeed suite your style, I decided to lower the bottom bracket a few inches by making a small mod to the frame. Since I planned to remove the top tube and convert the frame from a girl’s frame, this wasn’t a big deal.

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Removing the top tube.

The top tube is cut from the frame right at the thick part of the lugs on both the head tube and seat tube as shown here. The frame is no longer a girl’s frame, in fact it is no longer a frame at all, as it would not even hold up to a child’s weight like this. I did not cut flush with the tubing due to the lugged frame construction, as this would make a huge mess. I planned to use the thicker part of the lugs to my advantage, as you will soon see below.

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Take a bite out of your bike.

A rather lazy way to change the angle of a welded tube is to slice a thin pie shaped wedge out of one side, then bend the tube towards that side to fill the gap. As shown here, I hack sawed a pie shaped cut into the base of the down tube so it could be bent upwards, reducing the height of the bike. Mild steel is very forgiving, and the bending process will not weaken the metal, and after the gap is filled with weld metal, it will actually be stronger than when I started.

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Filling the gap on the re-adjusted down tube.

Once the down tube was bent upwards to close the gap (easy wasn’t it?), the area was welded solid as shown in here. If you made your wedge shaped cut even on both sides of the tube, then the tube will be moved in perfect alignment with the rest of the frame.

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“Un-squishing” the fork tube to make it round.

I thought it would be cool to use only the original bicycle tubing to make this chopper, and since I had a pair of fork legs from the original bike, I decided to use them to make a nice curved top tube. The fork tubing is actually round tubing that has been squished into an oblong shape. To merge it into the frame, I “un-squished” it in the vice, welded the forks together so I would have a piece long enough to become the new top tube, and a bit left over to fill in the ugly gap on the lower lug.

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The new frame – all forked up!

The un-squished fork tubing was cut to fit in place as a new main tube, and the leftover end was welded as a gusset where the lug stub was left from the original top tube and seat tube. This little curve on the top tube gave the frame a stylish look, and would be the basis for a gas tank style gusset later on in the build.

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The slightly lower frame.

Now that the frame has been modified, place the bottom bracket about 6 inches lower than it was before. Although the frame is still tall and laid back, this would work well for what I had envisioned. Be careful with the forks at this point, without the top of the triple tree, they would not take much weight. Dude, don’t sit on the bike yet!

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Template for a stylish gusset.

I found an old cardboard box that contained bicycle safety brochures, and promptly emptied its contents into the garbage can – so I could salvage the empty box. A cool looking gusset was cut from the cardboard as shown here, and this was traced onto some scrap sheet steel.

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Cutting the gusset pattern.

The gusset is cut from the steel using a worn out cut-off disc on the angle grinder. Although a jig saw with a metal blade is best when curves are involved, this method is much faster if the curve is only slight and you have a worn out wheel like I did.

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Nuts and bolts for the top of the triple tree.

To form the top of the triple tree fork, 2 1/2 inch nuts will be welded into the ends of each fork leg, and a plate will be secured to this by a bolt. Any nut and bolt that will fit into the conduit will work.

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Nuts welded into the fork legs.

Weld both nuts flush into the ends of the fork legs as shown here. The closer to center you can get them, the better. If the nuts a quite a bit smaller than the inside diameter of the tube, just weld as much as you can, making sure they are both facing the same side of the tube and centered.

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Two plates form the top of the triple tree..

The fork will use the conventional triple tree with a top plate bolted to the top of the fork legs, but with a slight difference – it will include the gooseneck as part of the plate. Rather than making a single plate and then fastening a handle bar clamp to it, I decided to use two smaller plates that will fasten directly to a gooseneck. This way, the original bicycle parts, including the handlebars could be used.

I started by cutting a few inches of 1.5 inch flat bar as shown in Photo 21. When bolted to the nuts that are welded into the fork tube, these plates will form a cap between the gooseneck and the fork tops as will be seen in the next few steps.

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Setting up for welding.

The best way to ensure alignment when welding the triple tree plates and gooseneck is to bolt the two plates as shown here; this is how they will be in the final design. The two plates should be aligned as if they were one single plate. The round area ground away at the ends of each plate will form a joint with the steel gooseneck.

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Weld the plates and gooseneck.

Once everything is setup, all you have to do is place the gooseneck into the fork stem, and weld the 2 plates in place. It’s best to make a few solid tack welds, then check it all over, being careful not to hit the fork threads with the welding rod. Once tacked in place, it will look like it does here.

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installation of the front forks.

Once the front forks are completely welded and ground, they can be installed onto the chopper. Now the frame can take the weight of a rider – of course, you may want to install a seat first.

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Welding a seat clamp just above the rear wheel.

Options for a seat on this chopper are abundant, but what I was looking for was something that would fit the theme of the original granny bike, of course, it had to be butchered into something evil at the same time. Rather than mounting the seat in its natural position, I decided that it should go as close to the rear wheel as possible, putting it just behind the seat tube. To accomplish this silly feat, I welded the seat clamp directly to the plate over the rear wheel.

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Now, that seat is low!

Once I reinstalled the super fat spring seat, it was almost sitting on the rear tire. The nose of the seat covered up the original seat post hole, and this really looked good – almost planned! We are now 30 seconds from the first test crash!

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Granny’s Nightmare completed.

Once I rode around the block a few times making sure everything was good, I stripped the bike right back down and painted it using the original deep blue color. I buffed up the chrome parts with some steel wool, and put the bike back together, and damn it dog, it sure looked cool!

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Where is my bike, young man?

Yep, Granny’s Nightmare really worked out nice! I even reversed the front fender just to add some more wackiness to the bike, but everything looked great. The front chain ring was replaced with a huge chrome unit from an exercise bike, but other than that and some fresh tires, the whole deal was made from the original granny bike. Told you it could be done!

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KoolKat poses it up with the chop.

Besides one small incident where the seat almost fell off and started rubbing on the rear wheel, all went well with Kathy’s first test ride (was that my fault for not tightening the bolts?). The bike rode well, did not rattle, and felt pretty comfortable considering where the seat was placed.

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Back from the dead – Granny’s Nightmare lives!

The moral of this story – never say a bike cannot be chopped. When you find something in the dumpster, don’t think, “Hey, look at that scrap.” Instead think, “Dude, this thing will make a sick chop.” In fact, just about any thing made of steel can be used for parts. See that old blender? Yeah, I can use that! Granny’s Nightmare is a prime example of what can be done by simply modifying what you have and using your twisted imagination to put vision into reality. Now I better go and hide the chopper before granny gets home from Bingo.


24 thoughts on “Granny’s Nightmare – HOW TO – Make a bicycle chopper

  1. jennybean says:

    This is sooo cool!

    I have to say, though, that my father, who is a welder has always warned us kids that bicycles should never ever be welded– if a frame on one of our bikes got bent or something, that was it– we got a new (or new used) bike. He says that they can never be done to his satisfaction that the joint won’t come undone with the possible impaling involved…

    I know this really isn’t in the spirit of make, but I guess it has been pounded into me so much that it’s the one thing I don’t fiddle with– lol!

  2. Bre says:

    This totally rules… Where’s my old bike with the banana seat?

  3. keinescheisse says:

    Gotta admit, older bikes make the best choppers. The typical bmx style bike just has too many straight lines whereas older style cruisers already have such great curves. And we all know that the best things in life have great curves.

    Great Curves

  4. DubNitrous says:

    Killer Putt…

  5. Patman462 says:

    Thats an amazing idea. I only have 2 questions. Question 1. How long did it take you to make it. Question 2. the bike i am going to chop has gears. there are only three but can I still use it

  6. Patman462 says:

    Does anyone have any ideas of how to make it longer because in the photo of Kathy riding the bike, her arms aren’t extended fully. I would like my one to be longer. Any ideas???

  7. custombuilt says:

    Hey Patman462 i know how to make it longer, ive been building bicycle choppers before the ones came out in stores. Patman462 you can still use it if it has 3 gears. I use to use stick to weld my choppers together, now i use TIG it is SO much better than stick and the welds look professional. Check out my choppers on my website

  8. Ganja says:

    Hey! I was at school, and did not know what to do.
    I surfed for a while on the internet, and guess what? I found this site. I was serching for: ”How to make lowrider chopper bicycle”.. And i found this site.
    I was blessed by love, I was sure, this is my bike. SÃ¥ i ran out, and look’d for some old granny bikes, and i found one, after one hour in the blizzering cold of Norway, so i followed all the instructions, and at the end, i had a perfect lowrider bike.. Thanks alot to the man that made this site, it gave me alot of joy!

    Anything you wonder about? Or want to se pictures of it? Send me a e-mail, or add me at your MSN messenger,
    Here is my e-mail:


  9. Anonymous says:

    wow this bike’s amazing..
    i’m trying to make my own one but with
    a rusty old bike..
    it’s a bit tricky with all the rust..
    i gotta grind all the rust..
    it’s a nice thing that there are way to make this bike.
    thank you..

    Brian from Indonesia

  10. mike says:

    Iwas stoked at your website.pretty awesome.Iposted earlier but didnt think they were going through.sorry for the multiple posts.I run A small operation in huntington beach called hole in the wall modified of my specialties is converting stock beach cruisers into cool looking chopped creations &its great to see there are others like yourself doing the same thing.Iwas buying my triple tree frontends from shops,but now that I see your great idea for fabricating them from stock forks I may never buy another one. thats awesome!I love your website, you have great ideas. thanks for the tip. I would like to send a couple of pictures of my work if youre interested. my E-mail address is…thanks from hole in the wall

  11. says:

    hey auwsome chop! im thinkin of buildin 1 soon, and by the way, GWABA

  12. hislogue says:

    It’s so cool~ Great !

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