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Old bicycle, new wheels - building a drop bolt to make the brakes fit.

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Picture of Old bicycle, new wheels - building a drop bolt to make the brakes fit.
I have an old bicycle frame which I love, but it desperately needed some new wheels. Old frames like this use 27" wheels. Most replacement wheels aren't built to modern standards and the tire selection is just terrible. New wheels are smaller (700c) and are too short for most brakes to reach the rim properly. The solution is a set of drop bolts!

I first read about this on Sheldon Brown's website, but he doesn't show how to build them. This instructable fills that gap.

Please note - If you build them and your brakes fail, don't come after me. Your bike was built to use a certain size wheel with a certain size brake. Change these things at your own risk.

A note about wheel sizes: I am using a set of 26" mountain bike wheels on a frame designed for 27" road wheels. The long-reach brakes shown here will reach a set of 700c wheels from the stock mounting location, but I didn't have another "spare" set of 700c wheels lying around. I did, however, have a set of mountain bike wheels. This bike is primarily used for a trainer so I don't have to mess with taking my favorite road bike off the trainer every time I want to go for a ride in the real world. The smaller wheels drop the bottom bracket and increase the risk of striking a pedal on the ground during a turn. If you mount a set of smaller wheels, always be aware of this when making turns.
 
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Step 1: Tools You Will Need

Picture of Tools You Will Need
Below is a list of parts and tools you will need:
  • Aluminum bar stock - I bought mine at the local hardware store for about $7. Don't go too narrow or too thin. It has to handle the force of stopping you!
  • Bolts and lock nuts - be sure to measure the size of the bolt on your brakes and get the same size from the store.
  • Aluminum tubing (not shown). It should be big enough to slide one of your bolts through and thick enough to handle the clamping force of the brake.
  • A hacksaw (for cutting the bar stock)
  • A drill and the right size drill bits (match it to the size of your bolts).
  • A wrench or two.
  • Some sandpaper or a file (not shown).
Since I had most of the parts lying around, the only real cost was the new bar stock - about $5.

Step 2: How low should it go?

This is the trickiest part of the process. You have to figure out how low your brakes should drop from the original mounting location for the brake pads to reach the rim. This will vary by frame, fork and brakes. It might be best to break out the measuring tape, but I chose to hold the brakes and the aluminum stock in approximate position and mark the bolt locations and cut lines with a pencil.

Step 3: Time to cut and drill

Mount the bar stock in a vice or get a really good grip and get after it with a hacksaw. Cut the bar stock to your estimated length. After you cut it, take it back to the bike and check the location for the first bolt hole you must drill.

Once you know exactly where you want the first hole, use a punch to create a starting point and then mount the stock back into the vice. The punch isn't necessary, but it helps to keep the drill bit from wandering when starting the hole. 

Double-check the second hole location before drilling it. Once two holes are drilled, triple check the hole locations by mounting the drop bolt on the bike and sliding the brake into place. The brake pads should align with the rim. If the holes are spaced incorrectly, there will not be enough pad adjustment on the brakes to make them align with the rim. If that happens, start over.

Step 5: Time to bolt it all together.

The brakes should have a couple of nuts which prevent the brake from rotating when tightened. Slide the first one on the brake bolt with the grooves pointed toward the brakes. Next, slide on the drop plate. 

The next piece(s) to slide on are the spacer(s). It is probably best to cut a piece of aluminum tubing to the correct length, but a stack of washers or nuts will do. The only tubing I had on hand was too short, so I added a couple of nuts to fill in the gap. The idea is to make the stack long enough so the drop plates fit snugly against the fork. 

After the spacers, slide on the second drop plate and the final anti-rotation washer with the grooves pointed toward the final nut. Place the final lock-nut and tighten, making sure everything is aligned. 

Finally, slide the brake into position so the holes in the drop plates align with the brake mounting hole in the fork. Slide a bolt through and tighten with a lock nut. 

Make sure the pads will reach the rim and align properly. Now install the brake cable and it is ready to go!
tigerbomb82 years ago
use kerosene for lubricating and to prevent clogging of the hacksaw teeth
TB-one can use ANY oil,no flames !,but oil the blade and material to be cut first,then add oil while cutting...
chive on?
Advar2 years ago
This is a great idea! I was thinking of doing something opposite that- 700cc rims on mountain frame. Thoughts?
i have already done something like this! I took an old huffy dual-suspension mtb and put 700x28 wheels on it. i had the same problem, going from V stop brakes to conventional
bicyclebuck (author)  Advar2 years ago
That might be more of a challenge. Most older mountain bikes have cantilever or v-brakes. There are two mounting posts that serve as pivots for the brake arms. You would have to extent the mounting point for the brake pads on the brake arms themselves to make it work.

I think the biggest challenge would be dealing with the travel and leverage issues. If you managed to mount the pads higher on the existing arms, you would have less leverage for braking. If you built longer arms, you could maintain the same leverage, but the brake lever travel would increase drastically.

V-brakes have this "problem" and that is why you can't use v-brake levers with cantilever brakes and vice-versa. The manufacturers adjust for the difference in travel by making v-brake levers pull more cable than cantilever brake levers.

I think I have written "lever" way too many times....

True and good advice... so much for disc brakes, then, too.
well you could get disc compatible MTB hubs laced to a 700c rim. I've seen it done quite a few times.
Hmmm, food for thought. Thanks :)
bicyclebuck (author)  Advar1 year ago
There are also 130mm disc hubs out there. They are hard to find, but they are available. You can also downsize some MTB hubs by changing out the spacers for thinner ones. You just have to be careful about not messing up the distance between the disc and the frame too much. If you start with a pre-built MTB wheel, you might have to re-dish the wheel to get it centered in the frame.
You should take into account the spacing. the spacing is also slightlydifferent....a MTB has a rear axle spacing of 135mm where as aroad wheel has I think a 120mm spacing....front on a MTB is 110mm where as a road is 100mm I believe. You may be able to fit them in though.
bicyclebuck (author)  Furball_Fidelis1 year ago
You are right about the spacing. If it is a steel frame, there is enough flexibility to fit larger hubs in small frames and vice-versa. If you like it well enough, a steel frame can be cold-set in order to keep the new spacing. You can find the technique all over the web (including Sheldon's site). Just don't try this with an aluminum frame. Moving the stays around on an aluminum frame can cause cracks.
bicyclebuck (author)  Furball_Fidelis1 year ago
You are right about the spacing. If it is a steel frame, there is enough flexibility to fit larger hubs in small frames and vice-versa. If you like it well enough, a steel frame can be cold-set in order to keep the new spacing. You can find the technique all over the web (including Sheldon's site).
while i don't know what the prices might be , Call on Coker Tire in Chattanooga TN and see if they can help you with the rubber part !

Buchanan's can be reached via the web and can probably help with the rims
bicyclebuck (author)  gearhead19512 years ago
The great thing about using 26" wheels is the availability of tires. Higher pressure "street" tires are available for mountain-bike rims just about everywhere!

For those folks out there riding knobbies on the street - take heed! You don't have to sound like a mud truck when you are riding down the road!
but,that's the only sound people hear when I'm riding my bike,unless I pedal backwards so they hear the loud clicking of my freehub. I liek the sound,
Got a brand of those higher pressure tires you like? I am making an e-bike and I want to keep rolling resistance down as much as I can and I am going to be riding on pavement for 90% of the time.
Maxxis hookworms.One of the best street tires with little rolling resistance.
I know this is late as a late thing. But I love scwalbe marathons. They are armoured against punctures and run very smooth. If you're going for a bit watt ebike i would look at getting some fat franks
bicyclebuck (author)  Spokehedz2 years ago
There are a lot of options out there. I've used Kenda Kwest (26x1") and Specialized Nimbus (26x1.5") on a couple of different bikes with good results. There are a lot of Kwest clones - Panaracer, Hutchinson, and even Nashbar makes a version. I don't know who is copying whom, but they all have the same tread pattern.

Just keep in mind that rolling resistance is a complicated subject. Tire width, rubber compounds, casing flex, tire diameter, tread design, and even aerodynamics all play a role. Also keep in mind that you must find a balance between comfort and performance. For example, I much prefer 36mm tires on my road bike simply because the roads I ride are anything but smooth. Larger tires use lower pressures, making the bike much more comfortable over bumpy roads.

Below are a few links to sites you should review before making a decision on what tires to buy.

http://sheldonbrown.com/tires.html
http://www.bikeradar.com/gear/article/bicycle-tires-puncturing-the-myths-29245/
http://www.terrymorse.com/bike/rolres.html
http://www.rouesartisanales.com/article-1503651.html

Good Luck!
BicycleBuck
velojym2 years ago
When I built my single speed "ramp rat" bike (for to ride around on the airport tarmac), I used a Bridgestone frame meant for 27" wheels. 700c worked very well with some inexpensive mid/long reach brakes from Nashbar. As for using 26'ers... glad you got that working well! I probably wouldn't have even thought of it.
bicyclebuck (author)  velojym2 years ago
This frame was built for 27" wheels too. The brakes you see here are long-reach that I picked up somewhere - I think it was e-bay. I had this frame built-up with 700c wheels from my primary road bike after I trashed the frame (always check to make sure your trailer can't get loose). I bought a nice cyclocross frame to replace the road bike, so this frame went back to the hook on the wall. Then I realized that I had a spare set of 26" wheels from my mountain bike....
graydog1112 years ago
Very nice. I faced the same problem building my electric 3 wheel handicap vehicle. I mounted a clamp brake for one of the rear wheels and use a motorcycle wheel with drum brake on the front. I used stainless steel for most of the frame and the rear brake mount. I would advise using blue Loctite on the nuts so they don't come off. You can still tighten and loosen nuts with the blue, but DON'T use the red Loctite,or you will have to heat it to red hot to remove the nuts.
3 Wheel cart.jpg
LowEnergy2 years ago
Very nice instructable and nice solution. I might have done this instead of buying long-reach brakes if I had seen this to see how nicely it can work out!
bicyclebuck (author)  LowEnergy2 years ago
Thank you for the kind comment!
rimar20002 years ago
Would not it be more logical to use the right size wheels?
bicyclebuck (author)  rimar20002 years ago
Perhaps. But there are a couple of problems with that. The correct size wheel for this frame is 27" and these are getting more difficult to find. All those that I have found are single-wall rims. Modern rims are double-walled which makes them much stronger.

The second big issue is finding 27" tires. These are also difficult to find and the selection of tread styles and rubber compounds is quite limited.

The two most common wheel sizes these days are 700c (road) and 26" (mountain). These sizes offer the biggest selection in both wheels and tires.

Besides, I had a "spare" set of mountain bike wheels lying around which were just begging to be put to use.
Phil B2 years ago
How have your drop bolts worked out in use? Is there any chatter or lateral movement, especially where the brake caliper attaches to your brackets?
bicyclebuck (author)  Phil B2 years ago
No chatter whatsoever. If I didn't know that they were there, I couldn't tell by their performance. I have more noise and chatter from the cantilevers on my primary road bike.