found a good readout-
J, JJ, K, JK, B, P and D : Tyre bead
profiles / rim contour designations.
No, my keyboard letters weren't stuck down
when I typed this. The letter that typically
sits between the rim width and diameter
figures stamped on the wheel, and indicates
the physical shape of the wheel where the
tyre bead meets it. In the cross-section on
the left you can see the area highlighted in
Like so many topics, the answer as to which
letter represents which profile is a long and
complicated one. Common wisdom has it
that the letter represents the shape. ie. "J"
means the bead profile is the shape of the
letter "J". Not so, although "J" is the most
common profile identifier. 4x4 vehicles often
have "JJ" wheels. Jaguar vehicles
(especially older ones) have "K" profile
wheels. Some of the very old VW Beetles
had "P" and "B" profile wheels.
Anyway the reason it is an "awkward topic
to find definitive data on" is very apparent if
you've ever looked at Standards Manual of
the European Tyre and Rim Technical
Organisation. It is extremely hard to follow!
There are pages and pages (64 in total) on
wheel contours and bead profiles alone,
including dimensions for every type of wheel
you can think of (and many you can't) with
at least a dozen tabled dimensions for each.
Casually looking through the manual is
enough to send you to sleep. Looking at it
with some concentration is enough to make
your brain run out of your ears. To try to
boil it all down for you, it seems that they
divide up the rim into different sections and
have various codes to describe the geometry
of each area. For example, the "J" code
makes up the "Rim Contour" and specifies
rim contour dimensions in a single category
of rims called "Code 10 to 26 on 5deg.
Drop-Centre Rims". To give you some idea
of just how complex / anal this process is,
I've recreated one such diagram with
Photoshop here to try to put you off the
From the tables present in this manual, the
difference in dimensions between "J" and
"B" rims is mainly due to the shape of the
rim flange. This is the part in the diagram
defined by the R radius and B and P min
parameters. Hence my somewhat simpler
description : tyre bead profiles.
Note that in my example, the difference
between "J" and "B" rims is small but not
negligible. This area of rim-to-tyre interface
is very critical. Very small changes in a
tyre's bead profile make large differences in
mounting pressures and rim slip.
"A" and "D" contour designations come
under the category of "Cycles, Motorcycles,
and Scooters" but also show up in the
"Industrial Vehicles and Lift Trucks"
category. Naturally, the contours have
completely different geometry for the same
designation in two different categories.
The "S", "T", "V" and "W" contour
designation codes fall into the "Commercial
Vehicles, Flat Base Rims" category. The "E",
"F", "G" and "H" codes fall into the
"Commercial Vehicles, Semi-Drop Centre
Rims" category. Are you beginning to see
just how complex this all is?
I think the best thing for you, dear reader, is
a general rule-of-thumb, and it is this : if
your wheels are stamped 5 J 15 and you buy
5 K 15 tyres, rest assured they absolutely
won't fit. Car Bibles : The Wheel and Tyre Bible Page 4 of 4 Rims: B vs J - Automotive tire/wheel engineering - Eng-Tips
so... the B or J sizes are not revalent to width. i10 has simply 4 inch rims.