Upgrading an Old 1-1/4" Cannondale to a Modern 1-1/8" Fork (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Fri, 15 Mar 2024

Upgrading an Old 1-1/4" Cannondale to a Modern 1-1/8" Fork

My (beloved) mountain bike is an old 1993 Cannondale M700, which I've customized fairly heavily over the years. I know people say the new (enormous, heavy) mountain bikes are more capable, but I'm not convinced. I've ridden Dave's new Specialized and while it's a nice bike (and I love the modern trend of an 11-speed cassette with a single-speed front), it's heavy and slow-steering and honestly, it didn't tempt me to replace the Cannondale.

But one thing about the 'dale that could definitely use replacing: the fork. It came with a lightweight rigid fork (Cannondale called it a "Pepperoni fork"), but about a year after I bought it, they had a fork recall, where for a modest fee you could get a Rock Shox Quadra 10 instead of a rigid fork. My fork wasn't one of the ones recalled, but a friend's was, and since he had already ugraded to front suspension, he offered me the Quadra. It was easy to install, and I've been riding with it ever since.

A Quadra 10 was considered decent back in '94, but suspensions are one bike component which really have improved in the intervening years. I've replaced the elastomers but even so, the Quadra has never really been all that good.

I've thought about buying a better suspension fork, but on an old 'dale that's complicated: Cannondale used a 1-1/4" steerer tube, while almost all other manufacturers used 1-1/8". So it's almost impossible to get a suspension fork the right size.

[Measurements of original headset parts from a 1993 Cannondale M700] I've been dithering over this for a year or two, mostly because I wasn't sure what was involved with adapting a 1-1/4" steerer tube to a 1-1/8" fork. I took the 'dale's front end apart, took photos and measured everything, but that turned out not to be terribly helpful because nobody publishes measurements of the various adapters to help you see what might fit where. I didn't want to order a suspension fork only to find out that the project was impossible.

But that problem solved itself when a friend who no longer rides gave us an old mountain bike that had a Manitou SX Carbon. Initially the fork was locked up, but after some rebuilding and adjusting, it seemed to work fairly well, and it's apparently quite light, so it seemed like it might make for a nice test as to whether this Cannondale fork upgrade project was worthwhile. (If it works, I'll buy another fork and get the other bike working again, since it's a pretty nice bike in its own right.)

What Sort of Adapter?

There are two types of adapter you see recommended for this sort of conversion. First, there are simple head tube reducer shims for as little as $20; you'll see a lot of people recommending a set by "Problem Solvers" which is the same thing for a lot more money.

[Headset reducer shim, not curved, compared with fork seat, which is] It seemed to me that since I already had headset bearings, the shims should be enough: one shim sitting on the top bearing, one under the bottom bearing, and the new fork should slide right in. The problem with that theory? All the shims I could find looked like they had right angled seats, not the curved seats that currently made contact with the bearings.

So how are they supposed to be used, if not with the existing bearings? With a 1-1/8" sealed headset, maybe? I never found anything explaining that.

[1-1/4 to 1-1/8 Cannondale Headset Reducer Tube Adapter 1.25 1.125 EC37] [1-1/4 to 1-1/8 Cannondale Headset Reducer Tube Adapter 1.25 1.125 EC37] The second option, for a bit more money than the shims, are reducer headsets like this 1-1/4 to 1-1/8 Cannondale Headset Reducer Tube Adapter 1.25 1.125 EC37 inset which includes a stack of parts and bearings, for about $45. (There were a lot of similar ebay listings, but this one specifically mentioned Cannondale.) But the ebay page listed some measurements that didn't seem to correspond to mine, so I sent a message asking about that. I got back a series of replies that were way above the usual level of communication you find on ebay, confirming that this part should work, with a diagram of where all the parts go and pointers to several youtube videos demonstrating the install Headset Remove and Install, Make a Headset Cup Press).

That kind of service and helpfulness made the choice easy: I ordered the headset reducer. I also ordered a headset removal tool as shown in the Remove/Install video. I figured I could make the install press myself.

Disassembling the Old Front-End

Disassembly was easy. First, remove the front wheel. If you're confident this is going to work, either remove the brake cantilevers from the fork, or at least unhook the brake cables, so the brake cables (which will stay on the bike) are no longer connected to the fork (which won't).

Remove the handlebar from the stem. With most quill stems that means removing the grip, brake lever, shifter and anything else from one side and sliding the bar out. Stems for the new threadless headsets have a piece you can unbolt that lets you take the bar off without any of that hassle, a great idea.

Remove the stem.

[Two 40mm wrenches to unlock the lock nuts on a Cannondale headset] Unlock and remove the two 40mm nuts below the stem. You'll need two wrenches: one needs to be a thin 40mm open-end wrench, like the flat sort made specifically for bike headsets, plus another wrench that can accommodate 40mm (another headset wrench works, or a huge crescent wrench).

Slide the fork out of the headset. Assuming your Cannondale is like mine and has a headset consisting of two caged bearings at the top and bottom of the head tube, remove those bearings and wipe off some of the grease.

[Banging on the headset remover with a rubber mallet] Now it's time to use that fancy headset remover. I had to bang on it pretty hard with a rubber mallet to get the existing bearing races out. It also came in handy during the next step.

Pressing in the headset

Now it was time to press in the lower and upper cups of the new headset.

[A Great Big C-Clamp] Although I was fairly sure I had some 3/8" threaded rod, I wasn't sure where, and while I was looking for it, I noticed a Great Big Metal C-Clamp. Seemed like Just The Thing.

Nope! I don't recommend using a clamp. It slides and rocks around and it's extremely difficult to keep things straight. It became clear very quickly that I wasn't going to be able to keep the cups from going crooked.

I went back out to the garage and looked harder until I found the threaded rod, along with a bunch of Great Big Washers that I keep around for making welded metal art. I stacked nuts and washers on the threaded rod, and the lower cup pressed right in with my homemade headset press tool. It started to tilt at one point, but I was able to fiddle with the tool to apply more pressure on one side and get it going straight again.

[home-made bike headset press in action] The upper cup? Not so much. I tried four times and every time, it went crooked. I gave it up for the evening and settled in to do some serious web searching. Mostly I found people saying "do it carefully and it should go in straight", which wasn't very helpful, but I did find one specific suggestion: make the tool so that one end is fixed at a right angle so you're not trying to keep control of stacks of washers at both ends..

[home-made bike headset press] A couple people suggested gluing the nut in place, but I just used another nut on the other side of the washers. I re-greased the seat face and tried again, very slowly. And this time, finally, I did get the upper seat to go on straight, with only one mid-course correction needed.

Aheadset Complication

Now the headset was in place, ready to accept the new fork. The only complication: the new fork was still on the other bike. I removed the front tire and the stem, removed the V-brakes from the posts on the fork, and lifted the frame, expecting the fork to slide out. Nothing.

[Top piece of Aheadset showing plastic compression ring] It turns out the donor bike has an "Aheadset", which includes an upper compression ring of plastic surrounded by aluminum. I couldn't find much on Aheadsets, largely because of Google's crappy search: even with "aheadset" in quotes, Google helpfully decides I must have really meant "headset" and feeds me a long list of sites that don't include the search term "aheadset". And other search engines are worse. If somebody would please start a search engine that only shows pages containing all the search terms, I'd switch to it in a hot minute. Sorry, end rant.

Anyway, I eventually found a discussion thread that was actually about Aheadsets: one person used a screwdriver to pry off the aheadset lock ring, while a few others said just to hit the top of the fork harder with a rubber hammer. A third mentioned using a penetrating lube. So I used all three tips: I spritzed some WD-40 on the plastic ring, pried it a little with a screwdriver (but I only moved it about 1/4" that way), then held the frame in my left hand while smacking the heck out of the top of the fork with my rubber hammer. That did it (though I do wonder how I'm going to slide that ring back onto whatever fork eventually goes on the donor bike).

I'm happy to report that the Manitou fork slid right into the reducer headset.

Brake Woes

The main job was done! But there were a lot of little things left to do.

One of my big worries was brakes. I'm a fanatic about brakes. Over the years, I rebuilt the 'dale's brakes many times until I finally got it dialed in: XTR cantilevers, Scott red pads (now available as Kool-Stop), and good levers — I thought I remembered the levers being XTR, but they're actually Dia-Compe Power Control 11. (Levers make more difference than you might think.) The difference between these brakes and stock is night and day. When Dave raved about his new modern bike's hydraulic disk brakes, I tried riding it, and the disks worked ... about as well as my 'dale.

I was worried that I wouldn't be able to move my cantilever brakes over to the new fork. The fork has bosses, but they're made for V-brakes, not cantilevers, and I didn't know if the two types of bosses were interchangeable.

I put one cantilever on, mounted the front tire, and the cantilever was in just the right place. Relief — but only for a moment, because it turned out the fork is still missing something just as important: the cable hanger.

The old Quadra 10 had a cable hanger built in to the fork arch (the part that connects the outer lower forks and is attached rigidly to them). On the Manitou, the arch appears to be hollow carbon fiber; drilling through it to add a cable stop doesn't sound like a good idea.

I really didn't want to transplant the V-brakes from the Manitou's donor bike: braking was a weak point on that bike, and I find V-brakes even more fiddly to adjust than cantilevers. But it seemed like the only option, so that's what I did. And they actually work pretty well. Not as well as the old XTR cantilevers and Scott pads, but much better than on the other bike. Maybe it's the Dia-Compe levers. They make a terrible noise during braking that makes me worry for my rim, and they have a tendency to rub: I can see I have a long period of brake adjusting ahead of me. Maybe I'll eventually come up with a way of adding a cable hangar.

The bike is back together now. (Well, mostly; I had to reassemble it after I realized I'd been putting the stem on wrong for a threadless headset.) The new fork definitely makes a difference on the rocky local trails, especially while braking over rocks, and I love that I can adjust the stem to any length or rise I want. I worried a little that the steering would be slower because the new fork has more rake than the old one, but it steers fine for what little test-riding I've done so far. (Today it snowed, so it'll be at least a week before the local trails dry out enough to ride.) I can't wait to try this rig on Potrillo Canyon Loop.

[ 16:48 Mar 15, 2024    More bike | permalink to this entry | ]

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