Timing Belt Tooth and Surface Options
Timing Belt Tooth and Surface Options
Polyurethane timing belts can be customized with tooth-side coatings, back-side covers, and specialty surface treatments to optimize performance for specific applications. The most common options are PAZ (tooth-side polyamide for noise reduction) and PAR (back-side polyamide for wear protection), but a wide range of backing materials can also be applied to either surface.
This page covers the standard coating and configuration options available on all polyurethane timing belts from Texas Belting. For the full catalog of 18+ backing materials, see the backings and covers guide. For machining, drilling, and welded attachments, see modifications and machining.
- PAZ: polyamide on tooth side (noise reduction)
- PAR: polyamide on back side (wear protection)
- PAZ-PAR: polyamide on both sides
- DL: backing on tooth side
- DR: backing on back side
- T-Cover: thick PU layer for machining
- Options combinable on same belt
- Available on all T, AT, ATP, HTD, STD profiles
PAZ and PAR Polyamide Coatings
PAZ and PAR are the most commonly specified timing belt options. Both use a thin polyamide (nylon) fabric bonded to the belt surface. They are available on virtually all belt profiles and pitches.
| Option | Surface | Material | Thickness | Benefits |
|---|---|---|---|---|
| PAZ | Tooth side | Polyamide fabric | 0.5 to 0.8mm | Reduces noise 3 to 5 dB, lowers tooth/pulley friction, increases tooth wear resistance |
| PAR | Back side | Polyamide fabric | 0.5 to 0.8mm | Reduces back-side friction over idler rollers and support rails, extends belt life |
| PAZ-PAR | Both sides | Polyamide fabric | 0.5 to 0.8mm per side | Minimum friction on all surfaces, ideal for drives with toothed pulleys and smooth idlers |
DL and DR Backing Designations
When heavier backings (rubber, foam, PVC, felt) are applied to a belt, the DL/DR designation system identifies which surface receives the backing.
| Designation | Meaning | Common Backings | Purpose |
|---|---|---|---|
| DL | Backing on tooth side (Deckung Laufseite) | Supergrip, felt, foam, silicone | Product handling on tooth side; conveying against toothed surface |
| DR | Backing on back side (Deckung Rückseite) | Linatex, Supergrip, T-Cover, PVC | Product conveying on back side; machinable surface for custom profiles |
T-Cover and Thick PU Backings
T-Cover and D15 are thick polyurethane layers bonded to the back side of the belt. Their primary purpose is to provide a machinable surface for creating custom product-holding features through CNC machining after bonding.
| Option | Description | Typical Thickness | Best For |
|---|---|---|---|
| T-Cover / PU-385 | Thick PU backing layer | 3 to 5mm | Standard machining depth for pockets, slots, channels |
| D15 | Extra thick PU backing | 5 to 15mm | Deep-profile machining for complex product-holding shapes |
For details on machining capabilities (CNC milling, drilling, routing), see the modifications and machining page.
Common Coating and Backing Combinations
The table below shows frequently specified coating and backing combinations with their thicknesses and typical applications.
| Combination | Surface | Material | Thickness | Typical Application |
|---|---|---|---|---|
| PAZ only | Tooth side | Polyamide fabric | 0.5 to 0.8mm | Noise-sensitive drives, medical equipment, office machinery |
| PAR only | Back side | Polyamide fabric | 0.5 to 0.8mm | Drives with back-side idler contact |
| PAZ + DR Supergrip | Tooth + back | Polyamide + rubber | 0.5mm + 1 to 2mm | Quiet drive with product conveying on back side |
| DL Supergrip | Tooth side | Rubber | 1 to 2mm | High-friction product transport on tooth side |
| DR Linatex | Back side | Natural rubber | 2 to 3mm | Maximum grip for inclined conveying |
| DL Felt | Tooth side | Wool/synthetic felt | 1 to 2mm | Delicate product handling (glass, electronics) |
| DL Foam | Tooth side | PU or PE foam | 2 to 5mm | Cushioned handling, fragile product transport |
| DR T-Cover | Back side | Thick polyurethane | 3 to 5mm | CNC-machined product pockets and channels |
Frequently Asked Questions
PAZ is a polyamide (nylon) fabric bonded to the tooth side of the belt. It reduces engagement noise by 3 to 5 dB, lowers friction between the teeth and pulley grooves, and protects the tooth surface from wear. PAR is the same fabric applied to the back side, used when the belt back runs over idler rollers or flat support surfaces. Both are 0.5 to 0.8mm thick.
DL (Deckung Laufseite) designates a backing applied to the tooth side of the belt. DR (Deckung Rückseite) designates a backing on the back side (non-tooth side). These codes are used in belt part numbers to specify which surface receives the backing material. For example, "AT10 DR Supergrip" means an AT10 belt with Supergrip rubber on the back side.
Yes. PAZ, PAR, DL, and DR options can be combined. A common combination is PAZ on the tooth side for noise reduction and a Supergrip rubber DR backing on the back side for product transport. This creates a belt that is quiet in pulley engagement while providing high-friction product conveying on the back surface. Contact Texas Belting at 888-203-2358 with your combination requirements.
PAZ tooth-side coating typically reduces timing belt engagement noise by 3 to 5 dB. In noise-sensitive environments such as medical equipment, laboratory instruments, office machinery, and pharmaceutical cleanrooms, PAZ can make a significant difference in operator comfort and environmental noise compliance. PAZ is also recommended on double-sided belts where teeth engage on both surfaces.
Yes. When the back side of a belt runs over idler rollers, tensioners, or flat support surfaces, friction generates heat and wears the polyurethane surface. PAR provides a durable, low-friction barrier that protects the belt and reduces running temperatures. In applications with multiple idlers or long back-side contact spans, PAR significantly extends belt service life.
Supergrip rubber backing provides a coefficient of friction approximately 50% higher than bare polyurethane (0.8+ vs. 0.5 to 0.6 on steel). This makes it the standard choice for inclined conveying, product transport requiring positive grip, and applications where products tend to slide on the belt surface. For the full range of high-friction backings, see the backings guide.
PAZ (thin polyamide fabric) has a negligible effect on power capacity. Thicker DL backings (rubber, foam, felt) reduce capacity by approximately 5% to 10% because the backing material sits between the belt teeth and pulley grooves. Back-side (DR) backings have no effect on power capacity since they do not contact the pulley tooth engagement area.
Yes. PAZ, PAR, and all DL/DR backing options are available for virtually all belt series including T-Series, AT-Series, ATL, ATP, ATN, Move, Imperial, HTD, and STD profiles. Some restrictions may apply for very small pitches due to the thin belt cross-section. Contact Texas Belting at 888-203-2358 for specific availability.
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