Timing Belt Sprockets & Pulleys

Timing belt sprockets and pulleys are toothed wheels that mesh with synchronous belts to transmit power without slip. Texas Belting stocks 5,500+ timing pulleys in Houston: HTD 3M/5M/8M/14M, PowerGrip GT2/GT3, Poly Chain and trapezoidal MXL/XL/L/H, in finished bore, QD and taper-lock hubs, plus bar stock and flanges.

Shop timing pulleys by type

On this page: Pitch ID · 8M PD/OD · HTD vs GT · Bushings · Flanges · Design rules · Houston · Mistakes · FAQ

How do I tell what pitch my timing pulley is?

Measure from the center of one tooth to the center of the next with calipers, then check the tooth shape. Straight-sided, shallow teeth mean a trapezoidal inch pitch (MXL, XL, L, H); deep, rounded teeth mean a curvilinear metric profile (HTD, GT or Poly Chain). The table below turns that measurement into a profile.

From a worn pulley, count the teeth, measure OD, bore and face width, then confirm pitch tooth-to-tooth. If the belt is shredded, count pulley grooves instead.

HTD 8M pitch diameter and outside diameter chart

Pitch diameter (PD) on a timing pulley is calculated, not measured: PD = (tooth count × pitch) / 3.1416. The PD sits at the belt's pitch line, slightly outside the pulley body, so PD is always larger than the outside diameter (OD) your calipers read. On HTD 8M pulleys the published OD typically runs about 1.37 mm (0.054 in) below PD.

8M shortcut: PD in inches is almost exactly tooth count divided by 10 (36 teeth = 3.609 in PD).

Published chart values; ODs at a few tooth counts vary slightly by maker. Verify OD before ordering.

Our HTD sprocket collection stocks 8M tooth counts from the low 20s past 90T in plain bore, QD and taper-lock hubs.

Are HTD and GT2/GT3 pulleys interchangeable?

Only partially, and only in one direction. Per the Gates interchange guide, GT2/GT3 belts may replace HTD belts on existing 8M and 14M HTD drives; Gates sanctions this as replacement only, not for new designs, and rates 5M GT belts on HTD sprockets as not recommended. HTD belts should not run on GT sprockets at any pitch, because the deeper GT groove leaves the HTD tooth incompletely engaged. GT2 and GT3 interchange freely across generations.

Interchange guidance follows the Gates belt/sprocket interchange guide. Verify dimensions before ordering.

QD bushing, taper-lock, finished bore, or bar stock?

Larger timing sprockets mount on a split tapered bushing instead of a fixed bore. QD bushings use a bolted flange and mount standard or reverse for tight installs. Taper-lock bushings sit flush inside the hub for a narrower assembly. Match your shaft to a series below, then order the sprocket machined for it.

Standard published catalog values (Martin bushing data); verify against your bushing brand before ordering.

Finished bore sprockets ship keyed and set-screwed for standard shafts. MPB (minimum plain bore) pulleys carry a small pilot bore your shop machines to size. Bar stock is a machinable toothed length for custom widths, hubs and one-offs. Our Powerhouse line covers common HTD and MX sizes at value pricing.

Do both timing belt pulleys need flanges?

At least one pulley in every synchronous belt drive must be flanged, because a running timing belt develops a slight side thrust that walks it off an unflanged drive. Both pulleys need flanges when the center distance is 8 or more times the diameter of the smaller pulley, or when the drive runs on vertical shafts.

On short centers, normal practice flanges only the small pulley. If a flange was pressed off or damaged, we stock 770+ replacement pulley flanges.

Minimum tooth count and teeth-in-mesh rules

A synchronous belt must have six or more teeth in mesh with the smaller pulley to deliver its rated horsepower; below that, capacity drops sharply: one tooth's shear strength is a fraction of the belt's break strength. Minimum pulley size matters too: 10 teeth is the published floor for MXL, and recommended minimums rise with pitch and shaft speed.

• High ratios reduce teeth in mesh. A small driver wrapped under 180 degrees engages fewer teeth than its count suggests; check mesh above about 3:1.
• Match belt width to pulley face. A belt overhanging a narrow sprocket loads its outer teeth unevenly.

Timing pulley supplier in Houston, TX

Texas Belting & Supply stocks timing belt sprockets, pulleys, bar stock and flanges in our Houston, TX warehouse. Most stocked sizes ship same day; quotes typically turn around within one business day. We serve the Texas Gulf Coast and ship nationwide. Call (888) 203-2358 to confirm availability.

Common timing pulley selection mistakes

• Matching pitch but not profile. An 8 mm measurement could be HTD 8M, PowerGrip 8MGT or Poly Chain 8MGT; confirm tooth form before ordering.
• Ordering by OD instead of tooth count. OD varies with profile and maker; tooth count plus pitch defines the pulley.
• Reusing a hooked sprocket with a new belt. Worn, hooked or shiny-flanked teeth chew through a fresh belt; inspect sprockets at every belt change.
• Boring past the bushing limit. Bushings and MPB hubs carry published maximum bores; machining past them thins the taper and it slips under load.
• Removing flanges on long-center drives. Past 8x the small pulley diameter, or on vertical shafts, both pulleys need flanges.

When to call

• Poly Chain drive design, tensioning, or roller chain conversions
• Obsolete, metric or OEM part numbers that need a cross-reference
• Custom machining from bar stock: nonstandard bores, widths, hubs
• Drives that keep shredding correctly sized belts

Call (888) 203-2358 or send us what you have; belt markings, tooth count and shaft size are enough to start.

Frequently asked questions

Related products and guides

Last updated: July 2026