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PostPosted: Mon Jul 15, 2013 7:32 pm 
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Joined: Fri Jul 12, 2013 7:04 pm
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Hi all

Again maybe a silly question from some one who has not ridden for a while.

I'm building up a 1989 peugeot athena frame with period parts.

I'm looking at wheel rims, now I'd like to go for mavic 4 or 2cd's but what I am finding is that some are 650c and some are 700c.

Can some one explain in simple terms what the difference is ?

Also I would like thin tyres so again how do I know the size's

Thanks in advance

Paul


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PostPosted: Mon Jul 15, 2013 8:17 pm 
Old School Grand Master
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Joined: Fri Oct 14, 2011 8:41 pm
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Location: Cumbria
700c is the standard modern clincher / tubular size. Old sprint rims and tubs are also 700c

650c was the small front wheel size on Lo-Pro bikes.

I think the thinnest clinchers are 23mm, not a lot of air in them though which usually means a rough ride, people with more experience will be able to help more on that one:)

Shaun


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PostPosted: Tue Jul 16, 2013 10:33 am 
rider | rBoTM Winner
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You can certainly get 21's and possibly 19's but only in the more 'exotic' tyres. Why use a narrow tyre? Modern thinking has it that slightly fatter tyres are more efficient - and a lot more comfortable! I tend to stick to 23's as a good all-round size, even for time trialling these days. Inner tubes are easier to fit into fatter tyres as well.


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PostPosted: Tue Jul 16, 2013 10:50 am 
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I used to run on 18s back in the days when the roads had less craters covering them, wouldn't dare today for fear of smashing the rims. 23s on everything now


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PostPosted: Tue Jul 16, 2013 10:53 am 
Gold Trader / PoTM Winner / RB Rider
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My basso has Michelin 28s uncool?


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PostPosted: Tue Jul 16, 2013 12:04 pm 
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Quote:
I'm looking at wheel rims, now I'd like to go for mavic 4 or 2cd's but what I am finding is that some are 650c and some are 700c. Can some one explain in simple terms what the difference is ?


The 700c/650c name is just that, a name, it is not a measurement. BITD it used to be a guide to the approximate diameter of a wheel and tyre combo, but no longer works as a system.

Look out for ETRTO numbers.They look like this: **-***. This is the width of the inside of the rim section followed by the diameter of the bead seat, where the tyre bead sits in the rim. This is generally about 12mm smaller than the outside diameter of the rim. This numbering is used on both the rims and the tyres. Match the second, larger number for a tyre/rim fit.

The 700c rims are 622mm in diameter at bead seat, usually marked **-622. This is the normal size adult roadbike size.
The 650c rims are 571mm at the bead seat. Much rarer, usually found on the front of Lo-pros, front and back on some Tri bikes, and on small adult bikes.

To work out which you need for your bike, either measure the existing wheels, or the axle to brake distance on the frame. If you add the rim radius to the likely brake drop, that will give you a rough distance from axle to brake hole, that you can measure off the frame: (622/2)+45mm=356mm for 700c, (571/2)+45=331mm for 650C.

On tyres, again, the ETRTO number will help. Look for something like 23-622 or 22-571. The first number is the width of the tyre on a standard rim, the second is the rim diameter which it will fit. All tyres should be marked with this number.

All the best,


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PostPosted: Wed Jul 17, 2013 10:41 am 
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Joined: Fri Jul 12, 2013 7:04 pm
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Thanks for the responce's guys. I don't remember it being this complecated back in the day lol.

I think I am going to go 700c with a 23 tyre. Trying to get some nos old school Mavic 4cd's at the moment.


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