Instructables

Replace a mountain bike front fork for older MTBs

Do you have an older full-suspension mountain bike whose front suspension fork is a little tired? Replacement parts for it may be non-existent, and labor costs to do the work may be more than the cost of a new bike, but there is no need to clutter up a landfill with a perfectly good bike just for a better ride. Replace the entire front fork for something more modern and still not break the bank! Besides - this is the ghetto, and we make do with what we have. This is a good thing to do for a Freecycle bike, too.

Another neat thing about replacing your front fork:  you can you can spend a little extra to try out different styles and heights of handlebars to make the bike work better for you. The bike, as set up by the bike shop, may not be adjusted for you and your riding style. You can experiment with different riding positions and handlebar styles to tailor the bike for yourself.

NOTE: big props to Utah Mountain Biking and other MTB forums for information and resources.
http://www.utahmountainbiking.com/fix/
 
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Step 1: Parts and tools

I paid a visit to my local bike shop (here in the ghetto) to see what it would take to make my old bike's fork better. The bike shop guy said that I had an older 1-inch (25.4mm) threadless headset (as opposed to a threaded headset), which would make replacement very difficult since new MTB headsets are all 1 and 1/8 inch (28.6mm). I did some research and found a manufacturer that still makes MTB forks that fit a 1-inch threadless headset: RST.

I know that RST makes forks that many MTB riders consider as "entry-level" (being generous), but let's face it - my bike is 15 years old, and the technology in a new RST fork, compared to what I have, is like voodoo. Besides, RST has been around for so long and sold so much product, that they have probably managed to get a good product or two out the door by now.

The deal with the RST forks is that they can be purchased without a steerer tube, and you just order the steerer tube that fits your bike. To find out where to purchase these forks and their steerer tubes, just Google on "RST no steerer" and choose from those retailers. There are usually three RST products you will find with no steerer: The Capa, the Neon, and the Gila. The Capa is advertised as a Sport/Kids product, the Neon is advertised as more of a city/trekking (dirt road) fork, and the Gila is advertised as more Sport Cross Country Trail fork. I decided to get the Gila (although the Neon may have been a better choice, for reasons I will get into later).

I am keeping the cantilever brakes, since upgrading them will require changing the brake levers, which will require getting new shifters (since the brake and shifter levers are integrated), and so on until half the bike is replaced. My goal in this project is to keep as much original equipment as possible to keep costs down - this is the ghetto.

The parts you will need to get will depend on your headset size. You should remove the top cap from the stem and measure the diameter - ordering everything and then finding out it's the wrong size will ruin your day and take two weeks of re-ordering and delivering to correct.

You will first need to order the fork, steerer tube, and starfangled nut for the steerer.  If there's a choice, get the longer steerer tube (265 mm) to give you some freedom for adjustment. As for the star nut, you can get the nut by itself, or get a 'headset kit' that consists of the star nut, bolt, and stem top cap (these are usually listed in the "headset parts" area of the website, even though we're replacing the fork, not a headset). I got a headset kit and a spare star nut just in case I had a problem installing the star nut, but I didn't end up needing it.

So, start by getting these parts:

RST Gila T9 26" Fork, No Steerer
RST Steerer 265mm 1" 25.4mm (or 1-1/8 in 28.6mm) threadless
Star-nut, Bolt and Nylon Cap (Headset Kit) for 1" (or 1-1/8" ) steel steerer tube

In addition to the fork parts, you will need these:

Tektro Front Brake Cable Housing Stop
Replacement brake and derailleur cables
a metric M6-1.00 bolt, the longest length available at the store
a metric M6-1.00 35mm hex-head bolt (or M6-100 20mm allen-key screw if you use a Neon fork instead of a Gila)

If you are going to experiment with ride position and different handlebar styles, you should also get:

Two or three Headset Spacer Kits to fit your steerer tube
A long, adjustable-angle 1-1/8-inch threadless stem with a 1-inch handlebar clamp
RST 1-inch to 1-1/8-inch steerer shim to fit the new stem to your steerer tube (if needed)
Handlebars with a 1-inch center to fit the stem
New grips (probably need those anyway)

==========================================

Tools needed:

metric allen key set
metric wrenches
hammer
jeweler's screwdriver, flat-bladed
scrap of 2x4
15/64 drill bit
grease
hacksaw (or jigsaw with metal-cutting blade)
half-round metal file
masking tape

Step 2: Remove the front wheel

To remove the front wheel, first release the brake cantilevers by pinching the cantilevers together (as if the brakes are applied), grasping the cantilever cable's handhold, and popping the cable end out of the cantilever. Now the brakes spring open wide enough to remove the wheel. While you're there, pull the front brake cable out of the fork's cable stop (which is built into the fork brace)

Remove the wheel by undoing the quick-release, or removing the nuts with a wrench.

Step 3: Remove the cantilevers

Using an Allen key, undo the cap-screw that holds the first cantilever on the fork. Pull the cantilever off of the fork, making sure to remove the spring and any washers at the same time.

After I took it off, I used a piece of tape to attach the canti, screw, spring, and washers together (so nothing was lost) and set it aside. When removing the cantilever that's still attached to the brake cable, make sure that none of the cable parts are lost, but it isn't necessary to remove the cable (yet) - you can just let the canti dangle from the brake lever and handlebars.

Step 4: Remove the handlebars

If you are going to keep your present set of handlebars and are happy with the way your riding position feels, you don't need to completely disassemble the handlebars and stem - you'll just need to remove the stem from the fork and keep the handlebars, stem, and levers together as a unit, so skip ahead to the next step when the stem is removed. However, I decided to play with different stem and handlebar configurations, so here are the steps to disassemble the handlebars and levers.

First, pull the handlebar end caps out. If you have bar-end shifters, remove them

Then, if you have them, remove the bar end grips (the "longhorns").

Remove the grips. In this case, they are simple foam pieces, to be cut off and discarded.

Remove the brake levers and shift levers.

Remove the light(s), bell, GPS, computer(s), speedometer, map holder, bag brackets, and anything else you have from the front of the bike.

Remove the handlebars from the stem.

Step 5: Remove the stem and fork

Set the bike down on its side or invert it in a bike stand (because if the bike is upright in a stand, and you remove the stem, the fork will fall out on the ground). Make sure that there is a good table or sheet on the area below where you work, so that if any parts do fall out, they will be easily found.


Remove the stem bolt and top cap.


Remove the stem carefully, looking out for other parts that may also come out.


Remove any spacers.


Remove the top dustcap and its split wedge that secures it. This part was tricky, since it was literally wedged in place, so I had to tap on the steerer tube a few times with a 2x4 scrap to loosen it.


Remove the top headset bearings. I was lucky in that the bearings were held in a retaining ring. Your bearings may be individual balls that need to be collected. If your bearings are in a retaining ring, make sure to note which side of the bearings are on the top (hint - ball bearings should face in, toward the headset).


Remove the fork. Be careful to get any bearings or dustcaps that may come out with it, and save them in order. Again, if the lower bearings are in a retainer, note which side goes where.


The last thing we need to remove from the fork is the lower bearing cup. This is pressed on, so it will need a bit of coaxing. Usually, the fork has a little slot under the bearing cup that you can slip a screwdriver into and pry/tap it up. Mine did not have this slot, so I needed to use a hammer to gently tap a small sharp jeweller's screwdriver (electronic screwdriver) into the gap under the cup and pry it up. Pry a little on one side and then on the other so the cup comes up evenly and isn't bent, and don't scratch the bearing face! After prying it up about a centimeter, it should slide off easily.

Step 6: Prepare the new fork

Insert the steerer tube and its included spacer into the fork. Tap it in place using a 2x4 scrap until it's snug and seated so that just the outer ring shows.

Using a 6mm Allen key, tighten the steerer clamp bolts on the steerer tube. The bolts come with blue LocTite on them already, which is good. Tighten the bottom bolt a little at first, then the top, then the bottom, and keep alternating your bolt-tightening until everything is nice and secure. Google found me a document for an earlier model fork that says the bolts should be torqued to 90-95 in-lb. Since the price of a torque wrench and metric hex socket bits would nearly double the cost of this project, I decided to just, sort of, tighten the hell out of them. This is the ghetto.

Next, secure the fork in a clamp or vise (or WorkMate) and slip the lower bearing cup onto it. Using a hammer and a scrap of 2x4 to protect the cup, tap the cup onto the steerer tube. Tap it in place, first one side and then the other, alternating sides, until the bearing cup is seated on the fork crown.

Sharp-eyed readers will note that I am using a 1-1/8 steerer tube. The bike-shop guy was in fact mistaken, and my bike used the modern larger size, so this whole rigamarole with the RST 1-inch steerer was not necessary, but I felt that I should still share my research with you all. ALWAYS MEASURE BEFORE ORDERING. I decided to continue with the RST anyway, since the price is quite reasonable; after all, this is the ghetto.

Step 7: Prepare the fork, part II - the front brake cable stop

A word here about the old cantilever brakes - apparently they are dead technology these days, as most mountain bikes use V-brakes or disc brakes.  However, cantis still work, so you can save money if you retain them instead of replacing them with newer technology.  To use V-brakes with my current brake levers, I would have had to buy special cables to multiply the brake lever effort in addition to the new V-brake (total headache), and going to a disc brake would have taken so much effort and money that buying a whole new bike makes more sense.


Back in the day, the front fork had a built-in cable stop for the cantilever brakes.  However, no modern forks are made that include a built-in cable stop.  However, the Tektro Front Brake Cable Housing Stop works very well for this application.  Attaching it to the RST fork is easy if you have a Capa or Neon model – there is a metric M6 hole threaded for use in the fork brace, so just use a metric M6-1.00 20mm-long Allen-head cap screw to screw it into place.  Unfortunately, the Gila fork, for some reason, has its fork brace hole in the back of the brace and not in front.  The only remedy is to drill out this hole so it goes all the way through from the back to the front of the fork brace.  Unfortunately, this will destroy the threads, but the Tektro comes with a Nyloc nut that will work with your 35-mm M6 bolt.

 

Use a 15/64ths drill bit – it’s the closest size to metric M6.  Drill through the existing fork brace's hole – it’s very soft alloy and a good bit will eat right through it (so go slowly with this).

 

After you have drilled the hole, place the 35-mm M6 hex-head bolt through the hole, from the back to the front, install the Tektro cable stop in front, and use the M6 nylon lock nut that comes with the Tektro kit on the cable stop.  If you use the bolt from the Tektro kit, it will stick out and either interfere with the brake cable or the fork will bottom out on it when fully compressed.  If you use this bolt to attach a fender, be very careful that the bolt and fender don’t interfere with brake or fork travel.  

 

If you are planning on using a different fork than the one I used, but still need to keep the cantilever brakes for cost savings, make sure that the fork brace is stout enough that you can drill the hole for the Tektro cable stop (or that it has a hole in it already). You may have to experiment with the length of the bolt - the 35mm-long bolt is what I needed for this fork.


Sharp-eyed readers will see that I had assembled the bike before installing the Tektro cable stop - don't make the same mistake I made.  Honestly, the cable stop was just about the last straw – finally getting around to installing the brakes and then discovering that there is no built-in cable stop and no recommended part from RST was a near-disaster.  Luckily I was able to discover the Tektro part on the web, and it’s great that it fits so well on these forks.  What with the Gila’s extra travel and the fact that you have to drill it to make the brakes work makes me think that the Neon fork would have been a better choice, but my rides on forest preserve trails make me glad that I got the Gila fork to work. 

Step 8: Install the lower headset bearings

TIP - as you go, clean and add grease to the bearings and bearing races

Install the lower dustcap on to the bearing cup.

Install the bearings. If they are in a bearing retaining ring, slide that ring on to the fork and bearing cup. If they are individual bearings, install them into the headset bearing race in the frame.

Insert the fork into the frame.

Install the front wheel into the fork.

CAREFULLY turn the bike right-side-up, so that it's resting on its wheels again.

Step 9: Install the upper headset bearings

Install the upper headset bearings like you did the lower bearings.

Install the upper dustcap, and the split-wedge insert.

Install the spacers.

Install the stem, and push it down as tight as you can onto the spacers and dustcap wedge Tighten down the stem onto the steerer. This is just test-fitting, we will adjust the headset bearings later.

Install the handlebars on to the stem using the two-bolt clamp. Note that these particular bars have little white marks near the center that make it easy to center the bars in the stem - cool! Make sure to tighten both handlebar bolts equally, a few turns on one bolt, then a few turns on the other, so that all pressure is equal.

If you want, now is the time to experiment with ride position and bar height. Tape the shift and brake levers out of the way and ride a half a block or so, slowly, to see how everything feels. I found that inserting more spacers raises the handlebars, but also brings them up and back (into your abdomen), which shifts your weight too far back and makes the rear suspension bottom out. The Gila fork has so much travel and preload that I actually shifted my stem angle forward again as far as possible to compensate for the steerer height. This evened out the weight distribution and made it easier to control the bike.

Step 10: Cut the fork to size and install the star nut

Once you know where the stem should be, use a screwdriver to scratch a mark on the steerer tube just above the stem.

Remove the stem, and make another scratch mark about 1/8 inch or 3 mm below the first mark. This is where the steerer tube has to be cut.

When you cut the steerer tube, there will be metal sawdust to contend with. Some mechanics will just cover the headset with masking tape and saw away, with the fork and wheel still attached to the bike. I wanted to use a jigsaw with a hacksaw blade (poor man's SawzAll), so I took the fork apart again and mounted it in a vise for the cut.

After making the cut, file off the sharp burrs.

Take your starfangled nut and the long metric M6 bolt, and screw the bolt into the star nut. Then, using the bolt as a handle and guide, take a hammer and tap the star nut into the top of the steerer tube. The bolt helps you guide the nut straight down into the tube without twisting sideways. If it starts to go crooked, you can just straighten it by tapping the bolt sideways. Tap the star nut into the steerer until it's about 1/4 inch or 4mm down past the top of the tube. Remove the bolt from the star nut.

Reinstall the fork, bearings, dustcaps, spacers, stem, and handlebars as outlined in the previous step. This time, however, the top of the steerer tube will be a little bit below the top of the stem. Do not tighten the stem all the way this time. Install the stem top cap and screw the cap bolt into the starfangled nut.

With an Allen wrench, tighten the top cap bolt. If it's too tight, the bike will be hard to steer it will feel "bumpy" and grind as you turn the handlebars. If it's too loose, the handlebars and steerer will wiggle in the headset. Tighten the bolt until there is no wiggle, but the bars turn freely without grinding. It may take a while to adjust, because the headset's top dustcap wedge has to be driven fully into place, but be patient.

After the top cap has been adjusted, you can finally tighten the stem onto the steerer tube.

Step 11: Install the brakes and levers

Install the brake cantilevers onto the new fork. They will screw into the fork pivot bosses the same way that they did for the old fork. When installing them, make sure you plug the spring into the little spring hole as you put the cantilever into place. Grease the bosses while you are working on them.

Install the brake and shift levers onto the handlebars. If you are using the same handlebars and stem height as you had with the old fork, they should install with minimal hassle. If you have played with the ride position, the cables may now be too short, so you will have to replace the brake and gearshift cables. You will definitely have to replace the front brake cable, because the brake routing will have changed a bit. The procedure from replacing brake and gear cables is covered in other places on the web (like this: www.utahmountainbiking.com/fix/cablenew.htm ), and is beyond the scope of this 'ible, mainly because there are so many different kinds of gear shifters, deraileurs, and brake systems out there. I can tell you, if you have trigger-style index gear shifters like mine, do NOT disassemble the lever to get the cable out. Good lord, those parts can fly...


Step 12: Replacement complete

Success! Your good old bike with the new front fork is now ready for riding.

I am quite happy with how this turned out. The riding position is finally tuned to my preference, and my hands and back are not nearly so beaten up as they used to be. I also installed a "pillow" seat and removed the toe-clips - step by step this MTB is turning into a "comfort" bike, although it still handles trails quite well. I kept the "longhorn" bar ends because they are retro and they work, and the gearshifters and canti brakes work as well as they always did. Maybe I can't stop on a dime like a dual-disk setup, but I can stop quickly enough for most things.

Those readers with sharp eyes may notice that I didn't actually end up cutting my steerer tube at all. It is at the maximum height that I could use, and I think I have every spacer on the East Coast installed on the thing. Also, I ended up using the same stem that I had before, since it's about 200mm from tip to tip and it's the longest one I had on hand.

My goal of keeping as many stock parts on the bike has been met. All around, despite the troubles I ran into, I am very happy I dove into this project, since I now know how to adjust my brakes and gears as well as how to do a major bike repair. Another perfectly good bike has been saved from a landfill, and my expense has been minimal. A good ghetto project.
suit13375 months ago

it is quite funny, since i had the exact same "problem" like you: guy at the bike store said, that my bike is quite old and still uses 1 inch and in combination with my old disc break caliper there was only one fork he could order - an rst fork

just now i assembled the new fork and was just about to insert the new tube in the frame, when i noticed, the thread of the new steerer tube is too small
the old tube has printed 25,4 mm on it, the nut has printed 25,4 mm on it - but if you use calipers to measure them, you'll find out that it is not true - they have an inner diameter of exaclty 1 inch / 25,4 mm but the outer diameter is in fact 1,125 inch

so i can repeat your advice: do your measurement first and don't trust what is written on your bike, do your measurements :D

Advar1 year ago
No wonder I couldn't find any spacers!
For real though, great project, I 95.5% perfer on hand McGyverism to "buy it new". Disk brakes are fab, but pad repacement makes my wallet cry, so I went (back to) Old School. Nice 'ible :)
jwolters3 years ago
ANSWER bars?
I thought this was the ghetto?
exabopper (author)  jwolters3 years ago
Yo, I can pimp my ride if I want! Stop oppressing me! ;)
I love cantilever "center-pull" brakes like in the picture, simple and they work. I absolutely hate V-brakes. They never work correctly and one side always rubs against the rim.
mrlunna133 years ago
Hello,
I have been trying to find a goose neck like that, to mount on my seat post. What brand is it? are they outrageously expensive (most mountain bike parts are for me)? Any and all help will be appreciated.
Thanks,
Jesse
exabopper (author)  mrlunna133 years ago
This particular unit is a "Zoom" stem, and I think it's like 90 or 110mm long. I got all of my stufff online, and I think that you can get it from walmart.com if you want to. Really, you should go to Amazon.com or bikeman.com and just search for "adjustable stem threadless" and you will find tons of these, usually around $25 to $30 (or more, of course, but that's about what I paid).

Be sure to measure your seat post - most stems are made for 1 1/8 inch fork steerer tubes and 1 inch handlebars. You can get a 1 inch to 1 1/8 inch spacer for the stem if your seat tube is smaller.
bedbugg25 years ago
Interesting, I've never seen a fork with a split steerer clamp.
exabopper (author)  bedbugg25 years ago
I hadn't seen one either, and that's the main thing I wanted to share with the readers - that, and the Tektro cable stop so that the cantilever brakes could still be used.
Yeah, you can get quite a lot of converters and things for bikes nowadays, like things that can make a bike without a disc mount have disc brakes, and something that you can use to split two cables into one so you can run both brakes off one lever!
exabopper (author)  bedbugg25 years ago
One new thing I found that relates to this fork project is a through-bolt that is used to instead of the star nut to hold the  stem top cap.  However, it costs about 10 times as much as a star nut, even with the long driver-bolt that I recommend using to install it.
Another thing you can get doesn't require a star bolt is this http://www.merlincycles.co.uk/?fn=product&productId=547&categoryId=66 when you tighten it, it expands and it can be removed when changing the fork...you just have to remove the old star bolt first, and they don't like being removed! i know that from experience lol.