18 October, 2011

27" Wheels and Measuring Brake Reach

We get occasional requests for 27" rims or wheels. It wouldn't be hard for us to make 27" rims, but I don't think it's a good idea. Converting old 27" bikes to 700c is simple and almost always my preference.

A bit of background; 27" wheels were used mostly on American market mid and lower-range production bikes. There are some exceptions, but top-end frames with 27" wheels are relatively rare. The popularity of 27" wheels waned in the late '70s or early '80s when 700c became the near-universal road bike size. Today there are few choices of good quality 27" rims or tires and I don't know of a single new bike that still uses that size. The main reason to switch to 700c is to gain access to many more high quality tires and rims in more widths. 700c rims and tires are available in almost any bike shop anywhere in the world. You'll also gain a bit of extra tire or fender clearance.


These two wheel sizes are actually very close. 27" wheels have a bead seat diameter of 630mm, while 700c wheels are 622mm. That's only a 8mm difference in diameter or a 4mm difference in brake reach. This makes conversions simple.
A 27" wheel hiding behind a 700c rim
First check to see that your brake pad slots, both front and rear, have 4mm of room for downward adjustment. On many bikes conversions are simply a matter of installing wheels with 700c rims and adjusting the brake pads. But if the frame/brake combination does not allow sufficient downward adjustment you'll need brakes with longer reach. Since the brakes on most 27"-wheeled bikes are marginal, it would be wise to replace them in any case. Old single-pivot side-pulls are pretty weak in comparison to modern dual-pivot brakes. Even the famed Campy Record calipers can't compare to modern brakes such as the modestly priced Tektros.

If your brakes don't have sufficient adjustment the first thing to do is determine how much reach is required. Brake reach is simply the distance from the center of the brake bolt to the center of the brake pad. Since the pads can be adjusted up and down the reach for the brake is given as a range. Short reach brakes typically have a reach of 39-49mm, long reach is 47-57mm, and extra long is 55-73mm; always go by the actual reach specs, not by the nomenclature.
Brake reach
It's easy to determine the required brake reach. Simply measure the distance from the brake bolt hole to the center of the rim's brake surface as shown below
Determining required brake reach
So far I've written about caliper brakes, but there are some 27" touring bikes with cantilever brakes which typically don't have much adjustment. You can usually switch to Tektro CR720 brakes, which have about 12mm of adjustment, for conversions. I say "usually" because some bike companies were rather casual about correct canti-boss placement.

When converting you can either buy rims and lace them to your existing hubs or buy new wheels. With the availability of VO Raid and PBP rims you can retain the classic look of polished rims. We also offer a 126mm spaced freewheel rear wheel and a matching front that are perfect replacements for many bikes. 

I'm sure that there are some who will want to keep their bikes as original as possible. For a high-end production or custom frame that you view as more of a collectible than a user, this makes sense. Otherwise I would get a second set of 700c wheels for riding and keep the originals for display.

26 comments:

Doug said...

I've had success using Shimano M732 cantilevers, from the late 80s and early 90s, for this purpose. These are the the wide-profile Deores you see on decent MTBs from the era. They had just enough adjustment to allow me to fit 700s on my '83 Schwinn Voyageur (that has since died, sadly). I really like them, as they are fairly easy to set up and look quite nice in polished aluminum.

Of course when the excellent Tektro CR720s are so inexpensive,there's less of a reason to go hunting for vintage parts.

Anonymous said...

I ride 27" Araya rims on Campy hubs. They are on a Hungarian Csepel that had 27's from the factory and not for the US market. The original rims were Weinmann on Sachs hubs. I use Mafac racer center pulls.

Don said...

The Pashley Guvnor lists 28" wheels as part of its retro vibe. I think the rims have gold detailing. Makes me wonder who the Pashley is for.

camp6ell said...

OTTOMH, you can get good Conti, Panaracer, Specialized, Vittoria, Michelin 27" tires, all of which I've used and liked... sure, they only come in sizes 7/8 - 1 3/8, but that's a pretty damn reasonable choice, even if you can get more brands/sizes in 700.
The other thing about "upgrading" to 700s is the frame/fork clearance becomes much bigger, and more often than not, it was already pretty big anyway, so it looks a little goofy.

Anonymous said...

When converting a 27" Miyata to 700c, I found by installing the rear brake backwards in the brake bridge (on the inside of the rear triangle), it provided the extra reach required. There were zero issues with it, and it also looks cool and is certainly a novelty.

Anonymous said...

Camb6ell, Those companies may all make 27" tires, but they are mostly lower-end models. The best racing and touring tires are often made only in 700c (and 650b in the case of Panaracer)

The difference in frame/fork clearance between 700c and 27" is about 1/8"

Tarik Saleh said...

Don,
The Pashley Guv'nor are even bigger tires than what chris is talking about , they are roadster size 28"=635mm, vs 27" =630mm and 700c=622. Lots and lots of old english, indian and chinese roadsters run that size.

Nanseikan said...

Was ruminating on the differences between 27" and 700C after riding a friend's Giant CRX and then returning to my beloved Viscount Aerospace Victor. Riding the Giant I had to be more careful of pedal strike. Obviously that 8mm difference is significant when you're used to it. Not that I pedal around corners all the time...

Personally I stay with 27" because it's historically part of the bike, even though Viscounts were production bikes and not that special. Panaracer make 27" tyres in 1", 1 & 1/8" and 1 & 1/4" which is a fine range for me. I'm no lycra monkey so I don't need a super-wide range of spiffo tyres. And who knows? Maybe there'll be a 27" revival? Anyone read Jan's blog where he was reminiscing about 10 years ago when 650b tyres were hard to find? b

dwainedibbly said...

Great post!

Don't forget that many quality touring bikes used 27" wheels well into the mid-1980s. The theory was that if you had to replace a tire in Middle of Nowhere, USA, you could probably find a 27" replacement where a 700C replacement would be tough to find.

Anonymous said...

Re: Pedal Strike. I'm not so sure the difference here would be "obvious," when relative to other things. I mean, it's not an 8mm difference in height off the ground, it's only 4mm. Tire size, bottom bracket drop, crank arm length, and pedal thickness each individually could make more difference than that in how far your pedal is off the ground. And I suspect the various things that go into how far out your pedal sticks to the side (bottom bracket length, crank Q-factor, and how long the pedals are) makes at least as much difference.

That said, keeping a bike more original is probably a perfectly good reason to stick with something. But if I ever get a classic frame with 27" wheels, I will almost certainly convert to 700 when the time comes to replace the rims.

Christopher said...

My first and favorite fixed gear has 27" wheels mostly because they were the best/least expensive wheels I could afford at the time (ie: free).
I love them but should they ever need to be replaced, I would go with 700's for the convenience.

Calvert said...

Each of my bikes is a distinct case.

My main reasons for going to 700c wheels.
1/Fender clearance--older production bikes usually have little of it.
2/More wide tires available for 700's

My main reasons for staying w/27" wheels.
1/Ride'em if ya got'em---use'em up
2/Already has fender clearance
3/Kevlar-belted Vittoria whitewalls on my wall
(w/xlnt ride qualities)need a 27'' rimmed bike
4/Believing-the-ride-is-smoother-on-a-larger-wheel placebo effect

My 85 Schwinn Voyageur (canti brakes) has 27" x1 1/4 Wober rims, IRC tires. An under-rated frame with an under-rated rim size. You can still find them cheap.

The '85 Trek 720 (canti) came with 27" rims.
It now has 700's. The shoes don't grip the rim at precisely the best angle, but stop the bike efficiently w/o requiring regular adjustment.
I wonder if the Tekros would be worth considering when I run out of tires or wheels for the Voyageur and need to switch to 700's.

About half of my center-pull classics have 27" rims but they would look just as good with 700's.

Anonymous said...

I currently ride two bikes with 27"
wheels - an early '80s steel frame with Araya wheels, used for commuting and touring, and a '87 Santana Soverign with it's beautiful Columbus fillet brazed frame, Wolbler Super Champion 58 wheels. Over the years I have used Specialized Armadillos, Panaracer Paselas, Schwalbe Marathons and Conti Gatorskins. All are excellent tires, with their own pros and cons. Over the past three years we rode our tandem through numerous brevets, fleches, a Super Randonneur series, an R-12 and I don't know how many centuries, all on Conti Ultra Gator Skins, with exactly zero flats. I disagree those who state that there aren't any quality 27" tires anymore. To me, it is a myth perpetuated by those who don't run 27" tires, are unaware of what's available and, therefore assume there aren't any good ones, out there.

masmojo said...

Chris, Change from 27" wheels??? next you will be suggesting people get rid of their BioPace chain rings!!! LOL!

Triangle Bicycle Commuter said...

On my 1987 Cannondale the Dia-Compe brakes had enough reach to make the switch to 700C.

Here is a picture where you can see the brake pads near the bottom of the adjustment area.

Jack - a Triangle Bicycle Commuter

Chris H. said...

I am converting a 27" to 700 due to many of the reasons given here but mostly because I have a bunch of used 700 tires. My one issue is using the rear brake. I cannot get it to function as a center pull. I like the look and feel of the center pull but Surly cable stop hangs too low off the binder bolt. Any suggestions? The straddle cable is not that long so there is minimal change available there. As a fallback, I can use a dual pivot but not my first choice.

Anonymous said...

Chris, considered having a drop bolt made so I can replace my 27s with 700c and still use my Campy centerpulls?

Jack

Pimadude said...

I recently converted my 1970's era Schwinn Paramount P-15 (definitely a "quality" bike) from the original 27" wheel size to a 700c. I used the Tektro R556 nutted-mount brakes that are sold by VO for the conversion. I've been more than happy with thisy conversion.

The availability of 700c tires in many sizes and types far exceeds those available for the 27" wheel size. For example, try buying a Grand Bois Cypres or Cerf tire in a 27" size!

Anonymous said...

Anonymous said... Re: Pedal Strike
Well reasoned, well said, but in response to piffle so you could have synopsized by saying: Pshaw! However, here's a thought in the other direction. When I converted an old Crescent to fixie (for training purposes, not part of the current StingRay nostalgia (not that I'm immune but for that I ride a StingRay)) I discovered the aggressive front geometry trapped my front wheel in the toe clips. Picture complete loss of steering and both wheels locked in the middle of a turn. That's not an issue with a freewheel but hard to escape if you can't stop pedaling! In that situation a combination of (slight) cleat reposition, shorter clips and switching to 622 rims with low-profile tires can alleviate a potentially catastrophic problem.

Unknown said...

CR720s almost never work for that!

Most 27" wheeled touring bikes can be converted to 700c successfully, but Tektro CR720s will almost never do the trick on an old 27" wheeled touring bike -- or even on a 700c wheeled old touring bike. For example my '83 Specialized Expedition came stock with 700c wheels, but CR720s don't come close to hitting the rim!

The problem is not the height of the cantilever bosses, it's the width.

Back around 1980, touring bike forks were built to clear a 32-35mm tire and fender, and brake posts were set just wide enough to be able to remove that wide of a tire from the fork.

Then mountain bikes hit the scene, and you had to be able to stuff a much wider tire between the brake posts. So the brake post spacing widened, and new brakes were built with this wide spacing in mind. New touring and 'cross bikes also adopted this wide post spacing.

As a result, If you put a newer canti brake on an older fork, the brake will want to put the pads in at far too narrow of a spacing. This would work if your rim was 5mm wide, but not on a real rim, so you'll rotate the brake back -- and now the pad is hitting way above the rim. It looks like the brake posts are too high, but really they're too narrow.

So if you're trying to convert, or even just build up an old touring frame, use a brake whose design dates back to before the MTB era like the frame was designed for-- at least, something with smooth posts instead of threaded. Smooth post Dia-Compe 981/982/983 have always worked for me, The current Dia Compe GC 999 has an eccentric adjustable pivot that may also help. Using a wider 700c rim also helps compensate for the worsened angle of attack of the brake pads.

VeloWrench said...

I have a 1979 Trek 910 that has been repaired and repainted by TREK in the 80's. When I bought it I replaced the original fork with an early 700c Trek OCLV and built 700c wheels for it. Now I want to have it painted and decaled back to it's original aesthetic and have decided along with that, I'll swap the fork for the original and go back to 27" rims.
I think the larger size is sort of cool. I've never held much respect for the 27" format, always thought of it as outdated and inferior. But Now I'm not so sure. With all the arguments in the MTB world for 29'er wheel size over 26", wouldn't this also be true for 27" wheels on the road? Lower angle of attack over obstacles? Faster rolling? I agree with keeping the original format as a means of maintaining the original design of the bicycle as it was intended. Bring back the 27"
And besides, why are we having this discussion when Velo Orange seems so enamored with 650b? What is the less supported standard?

TSVDP said...

You all should have a buy and trade area, wow, that'd be cool, like a bulletin board.

Anthony said...

I'm sticking with 27" wheels on my 80's Cannondale... They ride smoother because of the bigger diameter... and they look waaaay cooler! I don't need expensive high end 700 tires$$$$... I'm not Lance Armstrong!!!!!

Anonymous said...

There are lots of really, really nice old bikes that were built up with 27" clinchers. Besides, for me and many others, bigger is better when it comes to wheels. Seems to me that there is a golden opportunity to corner the market by offering a really nice 27" inch rim (maybe a built wheelset?). Sure it is currently an out of production spec, but isn't a lot of what you guys sell based on the great oldies???? I have no interest in converting any of my classic bikes to 700c. Not gonna do it, wouldn't be prudent. You can count me in for a pair to start.

Anonymous said...

VO wont entertain any requests for 27" wheels. This is amusing, because they seem so bent on classic bikes. Also notice, they entertain no requests for a 31.8 quill stem; again, they bag on the modern cycling mentality but don't support us with older bikes in a current market. Don't get me wrong, I'm a fan of VO - and at the least VO doesn't have the arrogance of Rivendell - but put up the classic bike facade if you aren't going to support the people who are trying to hold on to the classics.

Anonymous said...

I loves me a 27" x 1 1/4" ARAYA 16A(5)that came on my SCHWINN VOYAGEUR II back in 1976. These straight walled (NON CLINCHER) double walled 22mm width rims are made of a beautiful alloy that you just cannot find today at any price. I can't stress enough the quality of these Jap rims (495 gms) and high flange loose bearing Sunshine hubs w/ double butted spokes. Combine the added weight, larger wheel diameter, and wide 1 3/8" (that's 35MM to you'all) 66 TPI tires and...well, the word luxury comes to mind. You just wait, someday you be paying big bucks on eBay. Right after some bike idol mentions how nice they are and how he just discovered them. I'll have none of my four, superior quality, 27" wheelsets for sale.