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PostPosted: Tue Jul 10, 2012 5:25 pm 
Dirt Disciple
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Location: South East UK
Just wondering how much difference there is between a 700c & an old school 27" sprint rim.

I'm using an old pair of wheels for general riding that have 27" rims. & I'm looking at putting a better pair together for some fun entering a few time trials. If I were to opt for some 700c wheels, would I be needing to adjust the brake blocks etc, or could I simply swap the wheels over ?


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PostPosted: Tue Jul 10, 2012 5:49 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
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Location: New Forest, UK
The 700c rims will be 4mm smaller in radius. You'll need to adjust the brake blocks undoubtedly. In many cases you will also need new brake callipers, but that's a 'try it and see' matter.


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PostPosted: Tue Jul 10, 2012 6:02 pm 
Road Moderator
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Unless you fit big fat tyres and perhaps some guards 700c inplace of 27" will look odd.


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PostPosted: Tue Jul 10, 2012 6:08 pm 
retrobike rider
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Rob,

By " 27"sprint Rims" do you mean tubular/glued-on/sew-up tyres, or lightweight old British 27" x 1 1/4" tyre/tube rims?

Rims and tyres are best measured by the inside diameter of the tyre bead, or the outside diameter of the bead seat of the rim.
This is the ISO/ETRTO system:
Image
(Ignore the 559mm measurement, that's mountainbike 26".)

700c rims are 622mm in diameter at the tyre bead seat, roughly the centreline of the braking surface, about 14mm smaller than the outside diameter of the whole rim.

This is the same size as all 27"/28" tubular tyre/glued-on/sew-up rims.
So, if you are just looking to change from older tubular tyre wheels to 700c tyres/tubes, you won't have to move the brake blocks, the rims are the same diameter. :D

If you have the old British 27" x 1 1/4" tyre/tube rims, they are a little bigger, at 630mm diameter at the bead seat.
So you'll have to move your blocks down by about 4mm to work with any modern 700c tubular tyre or tyre/tube rims. (630-622)/2=4mm

Hope that helps.

All the best,


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PostPosted: Tue Jul 10, 2012 6:22 pm 
Dirt Disciple
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Hi thanks for the responses.

What I have are old 27" glue on tubular tyre rims.

What I'm trying to find out is whether I can use either 700c "glue on" OR 700c "tyre + tubes" without having to do any adjustments ?

It seems that you're saying I can use tube + tyre 700c as a direct swap with my existing glue on wheels, but is that also the case with 700c glue ons ?


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PostPosted: Tue Jul 10, 2012 6:56 pm 
retrobike rider
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Yup, Rob..that's right.

You won't have to make any changes if you're changing between tubular tyres/glue-ons and 700c tyres/tubes..
As far as I know, tubular/glue-on tyres have only ever been the 700c/622mm size*, not the Imperial sizes.

Tubular tyre/glue-on rims (old or new) and the 700c/622mm tyre size both stem from the French set of tyre sizes found on racing bikes of all sorts.
Interchangeable, so that they could switch between everyday wheels and race wheels without any fiddling....what you want to do.

The problems only arise when the old British 27 x 1 1/4"tyre size is thrown in :roll:.

PS: Just to confuse things...your 700c/622mm tyres might say something like 28"x 1" on them. Don't worry about that...look for the XX-622 number on the label.
PPS: *Tubular tyres are actually available in about half a dozen other smaller diameters too ...but don't worry about that for the moment either.:D

All the best,


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PostPosted: Tue Jul 10, 2012 7:06 pm 
Dirt Disciple
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Location: South East UK
thanks Dan

Next question..... If I were to get some "racing" (not overly competitive at my age) wheels made up, is there a big advantage in having glue on tyres or is it possible to get 700c that are as light & repseonsive as the glue ons ?

I have a pair of 28 hole campag record hubs & was hoping to use them, for the racing wheels, but am not really sure whether it's better to go with a tube/tyre or glue on type rim.


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PostPosted: Tue Jul 10, 2012 8:23 pm 
retrobike rider
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Personally I wouldn't bother with tubs these days...there used to be a big difference in weight and performance, but now...unless you're fussed about that last few hundred grammes per wheel.

Get some decent light tyre rims in 28 spoke (under 400g easy enough), double butted spokes, light inner tubes (60g) and the best most supple tyres you can find. I like Veloflex and Vittoria, but I'm sure everyone here has their own favourites.

All the best,


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PostPosted: Tue Jul 10, 2012 10:21 pm 
Old School Grand Master
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Location: Cumbria
I was in this cunnundrum and decided to think about DRC ST17's

http://www.jejamescycles.co.uk/drc-st17 ... d1079.html

or Mavic open sport

http://www.jejamescycles.co.uk/mavic-op ... .html#info

A tad heavier than 400gramme but should take the odd rut in the road well enough :D

Shaun


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PostPosted: Wed Jul 11, 2012 10:02 am 
Retrobike Sponsor
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There are plenty of clinchers that perform as well as tubs. Some tubs are excellent though apparantly (I have not tried then though).

IOf you want a tubular feel for your clinchers then wide rims are needed like the velocity A23.


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