Tyre and tube sizing

em2010

Hi everyone, I'm a newbie here so please excuse what is probably a stupid question.
I've just returned to cycling after many a year so could someone please help by explaining the tyre size I have so I would know what size innertube I need.
The tyre is marked thus-

( 42x622 ) 700x40C.

Now correct me if I'm wrong but I think 622 is the actual diameter of the wheel in mm, it being a standard 700C, I found that on Google, but I'm confused regarding the 40-42, if it's the width of the wheel why are there two numbers, they can't both be right can they?

Finally, given those numbers can some helpful person tell me the tyre size and tube size so I know what I would need.

Many thanks.

:?
It's all too much for me, I've only just got used to metres and inches.

topdude

Ok, your tyre is 700x40c which means it is approx 40mm wide and is suitable for the normal clincher style rim.
Tubes need to be similar to the tyre ie, 700x32-47 for example, 32-47 being a range of width that the tube is suitable for. see the link below.
http://www.chainreactioncycles.com/Models.aspx?ModelID=18907

Your next question is going to be what is Presta / Schrader ? Look on Wikipedia

em2010

topdude, thanks for the reply and info, so if 700x40C is the tyre size then would I be right in thinking that 42x622 is the wheel size ?

The valves I know about, they were around years ago when I was cycling in the good old black and white days.

Lillywhite

em2010 wrote:

.........700x40C is the tyre size then would I be right in thinking that 42x622 is the wheel size ?

700 (mm) is the nominal wheel diameter and 622 relates to the ISO number.

Everything you need to know is covered here:-

http://www.sheldonbrown.com/tire_sizing.html

em2010

Lillywhite, thanks for your input, I read the page you link to, and yes, thankyou, the Aspirin is working.

It gives as an example an ISO for a road tyre 700x20C as being 20-622, that I understand, but why then on my tyre does it change from 700x40C to 42x622, I still don't understand why there are two different sizes- 40 and 42.

Sorry if I'm just not getting it, but I just want to understand these sizes. :?

Lillywhite

em2010 wrote:

but why then on my tyre does it change from 700x40C to 42x622, I still don't understand why there are two different sizes- 40 and 42.

That seems strange, you havn't told us what the make and model of the tyre is so difficult to comment further. The smaller numbers correspond on all the tyres that I have on all my bikes.

However, since you only need a replacement inner tube then one that that suits 32-47, as the OP has recommended, would fit the bill.

According to this, 42-622 doesn't exist. :shock:

http://en.wikipedia.org/wiki/ISO_5775

PeeDee

Hi, tyre and wheel sizes are a real quagmire, bogged down with years of proprietary, national and historical baggage. You can generally rely on the ISO numbers for component compatibility, all the rest of the purported sizing codes you have to regard as 'nominal' at best.

The only sure way to know a wheel or tyre's exact dimensions is to look up the manufaturers specification, or else find one and measure it.

Having said that, exact inner tube sizing is not critical, anything roughly the right size will do.

em2010

Thanks all for your input.
Lillywhite, all I can find on the tyre is this,

INNOVA (42x622) 700x40C 1A-2066-3 Inflate to 50-75PSI (345-515kPa)

I've now ordered some spare tubes, I've gone for 700x28-45B+C, following the advice I reckon that's about right.

It's interesting that the ISO specs don't even show 42x622, looks as if the manufacturers are as confused about sizing as I was, I say was because thanks to all your help, guys, I think I'm beginning to see the light.

Thanks again.