Tyres for 26 inch vintage road wheels

[philtalksbx]

My son has picked up a scruffy Raleigh Olympus for an inexpensive (hopefully) resto project. It is generally good, but without tyres fitted and he is struggling to size them.
We are getting roundly confused with ISO diameters and by visual comparison concluded that 650B road tyres (584mm ISO) are too small and 700C (622mm ISO) are too big.
Research says the bike was supplied with 26 inch wheels but if we look at a Schwalbe City Jet 26x1.5 that shows a bead diameter of 559mm ISO.
Is there a discontinued size somewhere in between?
Any help or guidance is most welcome.

 

[Smokin Joe]

26" wheels used to be fitted to what were commonly known as "Sports bikes" back in the day, budget drop handlebar bikes. I've not seen them for years.

 

[MichaelW2]

26 x 1 1/4 Inch which SJS Cycles quote as 32-597

Most 1979s sports bikes used 27x1 1/4 but the Olympus was as youth bike so sensibly used 26".

 

[Ian H]

Here is all the tyre/wheel size information. https://www.sheldonbrown.com/tire-sizing.html
Scroll down for charts.

 

[netman]

It'll most likely be the 35-590 or 37-590 (26 x 1 3/8 in old money) you'll need... still available. Also known as 650x35a. Decathlon have some.

 

[iluvmybike]

Michelin do a 26" x 1 3/8th"

 

[SkipdiverJohn]

26" x 1 3/8" - ISO 590 are freely available, as I use them on my old 3-speeds.
26" x 1 1/4" - ISO 597, are more problematic and the choice is very limited. These were once quite common on vintage racers in smaller frame sizes and are now pretty rare.

 

[kynikos]

Don't know if this helps but I've just this minute come in from putting some new boots on my 1998 Ridgeback with 26 inch wheels. Tyres are Schwalbe Marathons 40-559 26x1.50 and have gone on with a little persuasion - which is usual in my experience.

 

[SkipdiverJohn]

Don't know if this helps but I've just this minute come in from putting some new boots on my 1998 Ridgeback with 26 inch wheels. Tyres are Schwalbe Marathons 40-559 26x1.50

You have ISO 559 MTB wheels, the old USA balloon tyre bomber standard size forever.

A Raleigh Olympus was a "racer", and if it was anything like my Raleigh Arena, the wheels will be ISO 597's, the hard to find ones with only a few options of mostly cheap rubber.

 

[philtalksbx]

Thanks everyone for the info - it looks like the 597s are the most likely - there are some Schwalbe 26 x 1 1/4 at SJS that will probably fit the bill.
A lesson learned as he begins restoring old bikes for himself.