700c and 27 inch

hi all , i have a 27 by 1.25 inch wheel which buckled on satarday, i was just wondering if both 700c and 27 inch whells are the same sixe.
thanks

Hello,

Nope, I'm afraid they're not. You should probably post this in the mechanics and fixing bit of the forum though.

it help you to know that 27in wheels have been outdated, and now looks like a good time to switch.

the radius of 700c rims is 4mm smaller than for 27" rims. This means you need different tyres, and any brake blocks would have to be set 4 mm lower.

Readers of this forum may have noticed that I have a bias in favour of old stuff, but even so I made a point of dumping all my 27 inch wheels some years ago. And I've never regretted that decision.

It is possible (but not desirable) to use 700 wheels in a frame intended for 27's by using long reach brake callipers, or in an extreme case, by brazing cantilever bosses onto the frame.

clubman - why is it undesirable?

I ask as a new owner of a nice old 531 lugged road frame built for 27 inchers, with a plan to getting a long reach brake? Does the long reach mean too much/too little leverage leading brake fail/wheel lockup?

Cheers,

Arn.

got a couple of friends who have old frames designed for 27 inch wheels - they've used long reach brakes without any problems.
check out dia-compe 806's, and alhonga's.
seem to do the trick!

It's undesireable for two reasons:

1. A big gap between the tyre and the frame just doesn't look right. I looks like the frame wasn't designed to take those wheels (it wasn't)
   
2. Long reach brakes are more prone to juddering.
   Braze on cantilevers solve the juddering problem. If you can't get brazing done, an alternative is to use Resilion cantilevers which bolt onto the frame. These are antique, and you won't be able to get the 'split' cables they need, but that doesn't matter because you can use a mafac centre pull type hook and a straddle wire with a solderless nipple on one side. All you've got to do then is to figure out a way of making some suitable brake blocks!
   

It's undesireable for two reasons:

1. A big gap between the tyre and the frame just doesn't look right. I looks like the frame wasn't designed to take those wheels (it wasn't)
   
2. Long reach brakes are more prone to juddering.
   Braze on cantilevers solve the juddering problem. If you can't get brazing done, an alternative is to use Resilion cantilevers which bolt onto the frame. These are antique, and you won't be able to get the 'split' cables they need, but that doesn't matter because you can use a mafac centre pull type hook and a straddle wire with a solderless nipple on one side. All you've got to do then is to figure out a way of making some suitable brake blocks!
   
   

I have an Alhonga brake on one of my bikes (using 700c but designed for 27"). Granted, it looks worse than a steaming pile of poo, but I can't recall it ever juddering and stopping power is better than my other bike which runs a short drop 105 and Crosstop lever. Same rims on both.

But the Alhonga's do nothing for the aesthetics of the bike, nor does the large gap between tyre and fork crown :(

I thought allot of older frames were built to allow mudguards to be fitted for road training, also may of the old 'tracks' were not paved tight tire clearance would have been a disadvantage, they are going to be gappy.

I use deep drop brakes on my winter bike...it stops OK never noticed judder.

Why should teegan not just get a new rim? I know there is not much choice for both rim and tires but it has to be the easiest and quickest option to get the bike on the road.

I replaced the 27"s on my old puch and the existing weinmann brake work just fine - no worse than they did before anyway. Plenty of travel built in on the pads, no need to file the slots out or do anything complicated.

the radius of 700c rims is 4mm smaller than for 27" rims. This means you need different tyres, and any brake blocks would have to be set 4 mm lower.

This is exactly what I've been saying in discussions with a couple of riders and unless you are a serious restoration enthusiast 4mm isn't going to make too muck difference to the look or the ride.

Unless, of course, you are a dedicated track rider that needs the slightly larger circumference to improve that PB.