bairnn

i have an older road bike with some 27" wheels that need to be replaced, I was wondering if i could put 700c wheels on this bike with no problems... I have 700c wheels from another bike and was looking to avoid buying new 27"

Raiden

Definitely maybe, possibly probably not.

Depends on how tight the geometry is on the frame, how long the fork is, etc. The issue is how far the brake calipers will reach. Some tightly-designed frames can be swapped to 700s with the addition of long-reach brake calipers, and some need long-reach calipers to reach the 27" rims. Got a picture? Straight-on shots of the front and back brake calipers, with the wheels installed, would be ideal.

mawtangent

I run a 700 front wheel on my '86 Schwinn Traveler (the original 27 wheel that came on the bike is slighter greater in diameter than a 700), the design of the brakes allowed for the movement of the brake pads to work with the 700. You might just want to try out what you got and see if it fits.

Road Fan

Basically you need to be able to move the brake shoes 4 millimeters lower in the caliper slots, so they will squeeze on the 700c rim instead of the tire. If your calipers are long enough to allow that, you're golden. If not, you'll need to get some longer-armed calipers. Remember the 700c rim is actually smaller than the 27 inch rim, by 8 mm in terms of diameter.

badamsjr

+1 It might be a good idea to look into long reach dual-pivot calipers. Tektro has a few to choose from. Kool Stop salmon pads are also a good upgrade. I made this switch on my Schwinn World Tourer, but realized that the drivetrain was unique (Shimano that has freewheel built into the bottom bracket vs rear wheel hub), so ended up putting the 27" wheels back on with new tires. Left the Tektro dual-pivot brakes w/KS salmon pads, though.

The thing I found with the KS salmon pads is that they leave MUCH less debris on the rims than Shimano and other brands of pads I had tried. It gets old having to clean that detritus off the rims! Now I do a 'start-of-season' and 'end of season' check of rims/pads, and have a lot less cleaning to do!

P.S. Those 27" wheels are STEEL by the way, so the KS salmon pads were a 'must' in my mind. I know, I know, my mind aint what it used to be, but I thought it might be important to be able to stop if I needed to.

cappuccino911

iput 700c on my 83 nishik century with it's original diacompe brakes with no issues, just a pad adjustment. If your bike has those old school brake block style of pads you will probably want to go with a modern brake pad for better stopping power. I have a combo of the salmon/black pad on my bikes and they do stop much better for me.

Retro Grouch 

So test fit the 700c wheels that you already own and see for sure exactly what you are going to run into.

Yemff

Yes its possible, 27" wheels have an ISO of 630mm, and 700c have an ISO of 622mm. So the rim is smaller by 8mm in Diameter or 4mm in Radius, so there is a chance your calipers will reach the extra 4mm. If not you can get long reach calipers, such as shimano br-600 or br-a550 for $15-$30 each

EM42

also your pedal could be 4mm lower this might not seem much but there is a possible pedal strike on steep turns if ridden as fixed gear please note of this.

mustachiod

i had 3 different bike shops tell me i would need to buy new brakes if i wanted to switch from 27 to 700. i didn't have access to any 700s to try at the time. turns out they were ALL wrong.

just try it and see

Steve Katzman

You say you have an older bike. You might want to check the spacing between the rear wheel dropouts to see if they match with the current standard of 130mm (5.12"). Some older bikes, depending on their age, might have less so it might pay to measure first. Not to say that the frame couldn't be "adjusted" to work but it is something to consider.

fietsbob

+1 , the dropout issue
over the years rear wheel axle widths have widened, so the dropout spread had to follow,
to make room, as the # of 'speeds' were added..
... 5, 120,.. 6/7 , 126 ... 8, 9, 10 ,11 road , 130 & mountain bikes 135mm ..

Adohrn

Since you already have the wheels just give them a try if the frame is steel. If aluminum or Carbon don't try this. Most steel frames can accommodate one size up (ex 126mm spacing to 130mm) without having to cold set frame. You might decide to cold set latter, but for now it won't do any harm it just might require a little extra effort to get the wheel in. If the brake pads contact the rim correctly your golden. If they get close lets say 1 to 2 mm short a small round file can be used to extend the slot on many calipers. Just make sure you don't remove any great amount of material as this can weaken things. Its a judgment call. If your brakes are pricey collectibles I would go ahead and just buy long reach calipers.

The 4mm you loose can cause pedal strikes. Not common but not unheard off. Usually the result of a bike with long crank arms and little clearance to begin with. Doing some testing at low speeds would not be unwise.

Road Fan

The pedal strike issue is really just a matter of inherent clearances and how hard you ride, and you're the only one who can assess that. The lateral clearance WILL be less, but that really might not be a problem. A lot of well-respected 700c racing bikes have BB drops between 7 and 8 cm even with 175 mm cranks AND with narrower tires that have smaller radii.

Another significant factor is whether you will use wide old school rattrap touring pedals, much narrower old school road pedals like the old Campagnolo Record Strada (or Pista, for that matter), or a clipless pedal with a really small platform, like maybe a Crank Bros or an Eggbeater. I'd bet the difference in width between these pedals is a lot more significant in lean safety than the 4 mm difference in rim radius.

And even if the clearance is compromised, if you ride road non-competitvely you can learn to raise the inside pedal as you corner, not pedaling through corners.

LeicaLad 

I've had no problem with two older French bikes in going to 700c, but these were relatively tight geometry "racing" frames. Now, I have an even older British frame built for 27" wheels + fenders, and the reach is really long.

To complicate things, I have really been wanting to do a 650B conversion to get the really big fat tires. But, with my frame that was originally built for 27" wheels & fenders, the reach may simply be too long for a 650B wheel.



This is a 700c wheel and Zeus calipers.

From my ballpark measurements, it may take a 72-73mm reach brake to fit a 700c wheel in there. I don't have a 650B wheel to try (although I'm looking in the NoVa area!), although given the reach needs of a 700c wheel, it looks very dubious that a 650B wheel will be a viable option.

My original hope was to run a 650B wheelset with 42mm Grand Bois Hetre tires.

My question is: If a 650B wheel is not an option on this frame, does a fat 700c, say 35mm, at least approximate the ride of a 650B 42mm? How would it be that different (in subjective terms)?

I'd consider hunting for ultra-long reach brakes, but I suspect that if a reach that extreme is required, it just isn't going to look right nor feel right, either riding or braking.

Comments and advice sincerely sought.

Thank you.

dabac

One option(which actually is easier if the reach is way off) is to use what Sheldon Brown calls a drop bolt. It's basically a tab with two holes in it. One hole allows it to be bolted to the fork crown/brake bridge, the other hole is used to attach the brake to the tab.

But I've also seen pictures of someone doing same thing to the brake arms, to drop the brake pads even lower. That guy claimed that it worked OK, but YMMV.

Mr IGH

700C wheels can fit a 27" wheeled frame in 99.9& of the time. I worked at a high end bike shop in the late 70's early 80's and did the conversion many times. On about 5% of the bikes I had to file the brakes a few mm to get the shoes to drop all the way. I've never seen a single bike that couldn't be changed with the original brakes. 4mm is less than 1/6"....

LeicaLad 

Hmmm. Well, that photo above clearly shows one of the 0.1%. I couldn't file those brake enough to reach those 700c wheels.

Mr IGH

Agreed, it's strange to see the shoes all the way down on any frame with the wheels the frame was designed for, what brand/application is that frame? By the 80's most low and medium cost frames/bikes could take both as the market switched over from 27" to 700c. Racing/Sport bikes with close reach brakes and 700C wheels are a different case. Those frames can have issues with 27" wheels due to lack of clearence.

LeicaLad 

Okay, to be clear, this frame was designed for 27" wheels + fenders. It's my 1963 Hetchins Mountain King.

What you see is a 700c wheel in the fork. Big drop problem moving from 27" to 700c. Long reach brakes would do, but I'm still wanting to put a 650B wheel in there to see just how far the reach would have to be. And if ANY brake would have that kind of reach. The question of (width) clearing a 42mm tire is another issue.

MikeWinVA

A drop bolt to bring the caliper closer to the wheel is probably the best bet. Lengthening the brake arms further in a similar manner is going to effect the amount of stopping power you have by changing the fulcrum of the brake.

LeicaLad 

Exactly. Good point to worry about. Unfortunately, the drop bolts are now amazingly pricey – when you can find them.

OR, I give up on the 650B idea. sigh.


p.s. - I like your Burke quote!

phoebeisis

If you have relatively low cost calipers you can just extend-rat tail file- the slots a bit if they are a mm or so short.
Usually you can do this switch easy enough on older bikes with no filing at all.
Charlie

LeicaLad 

Well, Mr. IGH already made that observation above. And we have an example here where that obviously won't work.

Anybody know a source for reasonably priced drop-bolts?

MikeWinVA

https://www.sheldonbrown.com/home-drop.html

Material costs only. You should be able to find all the needed parts at Home Depot or Tractor Supply.