CT and BP patch numbers, explained.
Every repair patch carries a number, and the number is the first thing a buyer has to get right. This page explains what the CT and BP series mean, which one belongs on which casing, and how to pick a size when you are holding the tyre rather than a catalogue.
Two series, two constructions
A tyre is built either as a radial or as a bias ply (cross ply) casing, and a repair patch has to match the construction it is going onto. The two series are not interchangeable, and the number on the box tells you which family you are in before it tells you anything about size.
CT numbers are radial patches. They carry bead direction arrows printed on the patch face, and those arrows have to line up with the bead of the tyre when the patch is laid in. A radial casing flexes along the belt in one direction, and a patch fitted across that direction works loose.
BP numbers are bias ply patches. Bias ply casings are still in daily use on tractors, trailers, light commercials and a great deal of agricultural equipment, which is why the BP series has not gone away.
Both are cold repair patches - no heat and no vulcanising machine is needed to apply them.
What the number actually means
Within a run of numbers, a higher number is a larger patch. CT No.10 is the smallest radial patch we make; BP No.1 is the smallest bias ply one and BP No.8 the largest.
The CT 80 series is a separate family, not a continuation. CT No.80 is a mid-sized patch - lighter than CT No.50 - so do not read No.80 as bigger than No.56 because the number is higher. Read the two runs separately.
The number does not tell you the shape. The CT series includes both square and rectangular patches, and a rectangular one is what you want for an injury that runs along the casing rather than straight through it. We do not publish which number is which shape, because that is not something we can state from the box alone - ask us and we will tell you for the number you are looking at.
| Air Flow CT radial patches - seventeen sizes, smallest first | |
| Main run | CT No.10, CT No.12, CT No.20, CT No.33, CT No.35, CT No.37, CT No.40, CT No.42, CT No.44, CT No.45, CT No.50, CT No.52, CT No.56 |
|---|---|
| 80 series | CT No.80, CT No.82, CT No.84, CT No.86 |
| Weight per patch | 12 g at CT No.10 rising to 1,250 g at CT No.56; the 80 series runs 150 g to 550 g |
| Air Flow BP bias ply patches - eight sizes | |
| Sizes offered | BP No.1, BP No.2, BP No.3, BP No.4, BP No.5, BP No.6, BP No.7, BP No.8 |
| Pack | Trade carton, size printed on the box face. The count per carton varies with the size - the smallest BP numbers come 30 and 25 to a carton, the largest 5. |
Choosing a size for the casing in front of you
The patch has to cover the injury and then reach well beyond it onto sound rubber on every side. A patch chosen to just cover the hole is the commonest reason a cold repair lifts at the edge.
Work in this order:
- Establish the construction first - radial takes a CT patch, bias ply takes a BP patch.
- Prepare and measure the injury after skiving, not before. Removing the damaged cord almost always makes the hole larger than it looked.
- Choose a patch that covers the prepared injury with a generous margin of sound rubber all round.
- Match the shape to the injury - a rectangular CT number for a long injury, a square one for a round one. Ask us which shape a given number is if the box is not in front of you.
- On a radial, line the printed bead arrows up with the bead before the patch touches the surface. You get one attempt.
As a rough guide to where each series sits: the smaller CT numbers suit car and light commercial radials, the middle of the range suits light truck and tractor work, and the largest numbers are there for truck, bus and off-highway casings. The BP range spans the same span of vehicles in bias ply construction. A tube, rather than a casing, takes a tube patch instead - a different product entirely.
Preparing the surface
A cold patch bonds to the rubber it is rolled onto, so the surface decides the repair. The inner liner is buffed back to a clean, evenly roughened surface with a wire brush or a cutter wheel, the dust is blown off, and the patch is rolled down from the centre outwards with a stitcher so no air is trapped under it.
Rolling matters more than people expect. An edge that has not been stitched down is where the repair begins to fail.
The products on this page
Browse the full range
The products on this page come from these parts of the catalogue - each one holds the rest of the range.
Where these are used
Buying patches by the box?
We manufacture the CT and BP ranges ourselves in Hansi and supply repair shops, retreaders and distributors directly. Tell us the sizes you move and we will quote against them.
Wholesale enquiry