318-Tyres, 26” X  2 ¼” 

Beaded-edge tyres 

Introduction:
The British Neracar Model A is provided with so called ‘beaded-edge tyres’, tyres without the two steel wires that wired tyres have. The steel wires are intended to keep the tyres in the bead seats of the wheel rim.
Beaded-edge tyres are very flexible, which means that they accept some degree of tolerance in rim dimension. These tyres have to be kept inflated to the correct pressure, in order to prevent the risk of loosing the tyre when going through a curve.

Definition:
Beaded-edge tyres are mounted on hooked-bead rims. They are marked with an overall diameter code and a nominal section-width code, separated by a cross (x). An example of such a marking is 26x1.375 (Wikipedia)

 Confusion:
For Neracar model A (and Model B by the way) the Drawings, Parts Lists and the Instruction Books ‘Wonderful Wheeler’ and ‘Motoring on two Wheels’, all mention for both wheels, front and rear, and for tyres as well as for wheel rims the size of 26” X  2 ¼”.
Ken Philp’s book however reads 26” X 2  ½”.
Both rims have the same seat-diameter , but a small difference in widths .

 Wired (non-beaded-edge) tyres:
Example:
A wired tyre with dimensions 26” X 2” has an outer diameter of 26” or 660 mm.
A wheel rim with dimensions 22”- 2” has an outer diameter of 22” or 559 mm.
A 26” x 2” tyre and a 22” – 2” wheel hub belong together.
Remark: A 22”- 2” rim is often called 26” X 2” however! This is incorrect, but easier to remember!
If a Neracar had wired tyres:
A  26” X 2 ¼ ” tyre will have an outer diameter of 26” or 660 mm and needs a rim dimension with a seat diameter of 26” – (2 X 2  ¼ “)  = 26 “ -  4  ½ “ = 21  ½ “  = 546 mm.

 Beaded-edge tyres:
Let’s take our Neracar rim and tyre as an example.
The wheel rim is listed as 26” X  2 ¼”, but it should now be called 21 ½” – 2 ¼”.
This rim will need a tyre with the dimension of 26” X 2 ¼”; this type of tyre is no longer being sold however.
Because of the floppiness of beaded-edge tyres, these rims can also be fitted with either 26” X 2” or 26” X  2 ½” tyres.
As beaded-edge tyres are more or less square, a 26” X 2” tyre on a specified Neracar rim will have a diameter which is somewhat smaller than 26” and will be a bit narrower.
By the same token will a 26 X 2 ½” tyre on the specified Neracar rim have a diameter which is somewhat larger than 26” and will be a bit wider. The tyre of course must fit in the mudguard.
My Neracar is fitted with tyres that read  26” X  2 ½” to fit 26” X  2 ¼” rim; the tyre has an outer diameter of 700 mm = 27 ½” and the rim has an outer diameter of 575 mm = 22  ½ ”. This shows that rims and tyres have a wide range of toleration.

 Bottom line:
Our Neracar will have :
23 ½” – 2 ¼” wheel rims (often called 26” X 2 ¼”) with 26” X 2 ½” tyres, as 26” X 2 ¼” tyres are no longer available.

Additional questions and supplies:
Additional questions, beaded-edge tyres, wheel rims and various parts for vintage motorcycles can be obtained from:

 Bert Pol Vintage Motorcycles
‘t Weegel 37
8055 PZ Laag Zuthem
The Netherlands
Tel. and Fax: +31 529 497417
Website: http://www.bertpol-vintagemotorcycles.com/
E-mail: b.m.pol@planet.nl