Fitting a 1 1/8" stem to a 1" threaded quill steerer

Believe it or not, once in a while we have a quick look at the stats for this blog to find out what people who've wandered in were actually trying to find. Then, if we haven't got what they were after, we try to provide it (unless it's the person who keeps looking for "fabian cancellara hair care," because we really don't know anything about that). Lately, a lot of people seem to be looking for advice on modifying quill headset bikes to accept modern threadless stems - we imagine this is largely because of the current craze for modifying older bikes into fixies, either for road use or for bicycle polo.

Now, as all right-thinking road cyclists know, fixies are the chosen steed of Satan. However, it's obviously a good thing if old bikes - sometimes, rather special ones - are used for riding rather than as a place for spiders to hang webs. So here we go...

Question: Can I adapt my old quill headset bike to accept a modern 1 1/8" (28.6mm) threadless stem?

Answer. Yep. And what's more, it's both easy and cheap to do so.

The old quill-type 1" headset (left)  has now been almost entirely replaced by the modern 1 1/8" headset.
As a result, choice of stems is now limited - and 1 1/8" stems are not compatible with 1" steerers. Unless,
that is, you use an adaptor.

Preparation
All you need to do is work out what size steerer your bike uses, and the best way to find out is by measuring it with  pair of vernier calipers. First, remove the existing stem by loosening the top bolt, which is often a 5mm allen bolt but may also be a hexagonal-head (or, if the bike is really old, a square-headed bolt - in which case, you should probably offer the bike to a museum). Once done, the handlebars and stem will come away from the frame - if they don't, the wedge nut that fastens them in place is probably rusted into the steerer. Freeing it will be a simple process if you read our guide on winter-proofing headsets.

Quill system with lock nut removed to
show the steerer
(image credit: Ellywa CC BY-SA 3.0)

You will now have easy access to the lock nut, which can be removed with a quill headset spanner or, if yours is an odd size, with a big adjustable wrench. Once that's out of the way, you'll be able to see the upper end of the threaded steerer which passes through the frame's head tube to the fork - this is the bit you need to measure. It's most likely to be 1" in diameter (that's 25.4mm if you only have metric vernier calipers), in which case the internal diameter will be 7/8" (22.2mm) of an inch. However, other sizes have been used over the years; ranging from an old-fashioned French standard of 25mm (with a 22m internal diameter) to a 26mm variant used on a few old bikes from Austria (also 22mm internal) to the 1 1/4" (31.8mm) used on tandems. If you find you have either the French or Austrian size, the adaptor we'll be looking at below will probably still work provided you use a shim - but you may need to find someone with a lathe and the knowledge to use it to make one for you, as the conversion isn't common enough for bike shops to stock a suitable part. If, by some extraordinary chance your bike has a 1 1/4", you may be able to find an adaptor to fit as a threadless steerer design with the same external and internal dimensions has been used on tandems and a few old Gary Fisher mountain bikes. But like we said - it's probably going to be 1". Most are.

While you've got your spanners out, it seems silly not to take the opportunity to give the bearings a clean, replace any that are damaged or missing and relubricate the moving parts. In fact, this is especially the case if you're modifying an old bike because you may not know how long it's been since anybody last gave them any tender loving care. The winter-proofing headsets guide tells you how to do this.

Take a moment to check the internal condition of the steerer. Many are made of steel and may be rusty (especially if you had problems getting the wedge nut out): a good way to find out is to remove the front wheel and mudguard if one is fitted, then push a small piece of light-coloured rag through with a length of dowel or a broom handle - you'll be able to see rust on the rag. If it is, wrap some sandpaper around the dowel and give it a clean, then use a new piece of rag to remove bits of sand and then another to apply protective grease. Even if there is no rust, regrease the steerer anyway.

Adaptors

When the 1 1/8" headset size became the mountain bike international standard, the market was flooded with adaptors designed to allow riders to fit 1 1/8" threadless stems to 1" threaded steerers. This was partly so that owners had a wider choice of stems and partly so that people with not-very-good bikes could make them look like slightly-less-not-very-good bikes. Nowadays, the 1 1/8" size has almost completely replaced the older design which appears only on the very poorest of supermarket specials and as a result adaptors are not so easy to find.

In Britain, they can be had from Halfords for a mere twelve quid: it looks - and we're trying to be charitable here - a bit spoddy, but it'll do the job. Our experience of Halfords is that some of their stores employ very good mechanics who know their trade and will immediately understand what you're looking for, then be more than happy to order one in if they don't have one. Other stores are, shall we say, not so good; and employ people who apparently know nothing about either bikes or customer service. Fortunately, if your local example falls into the latter category, you can also buy one online and they won't charge for p&p provided you don't mind waiting four days for it. Others are available, but do be careful not to accidentally buy a 1 1/8" steerer extender - the look very similar. If you're not sure, ask your local bike shop to order one in for you.

Fitting
Clean and grease the threads of the steerer before replacing the lock nut, then adjust the system so that the steering turns easily and without any fore-and-aft or side-to-side rocking (there's more about that here). If you don't have experience in adjusting headsets, getting it just right can take a few attempts as there's a knack to be learned; but it's a simple process and you'll rapidly pick it up. Once done, you can fit the adaptor. These mimic the quill stem in having a wedge nut at the lower end, which causes the device to expand and thus locks it into the steerer - there are two types, both of which can be seen below.

Wedge nuts, also known as expansion nuts. We prefer the type on the left, simply because it looks
less of a bodge, but they work equally as well.

Insert it to your desired height, making sure that you do so to at least the minimum insertion mark to ensure it won't come free when you're riding, and bear in mind that most stems offer a degree of rise - that is, they're angled so that the handlebars will be slightly higher than the steerer tube. Fit the stem onto it - in some designs, it'll slide right on over the top but with others it may be necessary to remove the top cap first, which is done by removing the bolt that connects to the wedge (this also depends on the type of stem) - and loosely fasten the bolts to keep it in place.. It doesn't matter too much if you get the height wrong at this point because one advantage of quill stems is they're far easier to adjust for height that threadless stems. You can now tighten the bolt at the top of the adaptor to fasten the device in place, but don't bother tightening it all the way yet.

Fix the handlebar into the stem, taking care to ensure it's centrally positioned (and, if it's a straight bar, the right way up - you wouldn't be the first to have put in the wrong way up). Sit astride the bike. Does the height feel right? If not, loosen the top bolt so that you can adjust the adaptor's position in the steerer. Once the height is ideal,  tighten the top bolt to expand the wedge nut and fasten the adaptor in place. Sit astride the bike again to ensure then stem is in line with the front wheel. Once it is, fasten the bolts than pinch it onto the adaptor. Finallly, check you've tightened the handlebar clamp bolts sufficiently and the job, as they say, i a good 'un.