All Porsche 928S4 and onwards use the same belt. It is a HTD belt. Actually since MY 1984 the HTD belt is installed. Differences are only in construction. Each brand tries to explain specific benefits from their construction materials.
Nobody says how long a belt lasts. None of the suppliers I looked up. But all say about 60.000 miles (100.000km). A general understanding is that the car does 20.000 km/year which means a belt should not get older than 5 years. Many notes on rubber timing belts say similar ageing: 5 years. 928INTL says 60.000 km is a good idea. My GTS belt was swapped at the Porsche Center at 66.000 and 10 years age. That seems like a real good time.
Sqare teeth cam gear Round teeth gear
As everything wears, so does the cam gear.
This shows how the edges of the sprocket wear and reduce the surface that the belt grips on.
Conti CT 584 HTD 2086, 9,525 Meters, teeth 219 www.contitech.de
or for the square teeth early 928 modes (up to 1983)
Conti CT 600 , 9,525 Meters, teeth 219
Dayco www.dayco.com DY95109 DY5060390
"DAYCO TIMING BELT -- Timing Belt (Camshaft), Self-Lubricating Fabric Provides Exceptional Resistance To Abrasion, Resulting In Extended Pulley And Belt Life, The Molded COG Design Runs Quieter And Is More Economical Than Chain Drives, Our Premium, High Modulus Glass Fiber Non-Stretch Cord Delivers Precise Length Stability To Keep The Engine Running Smoothly Over The Life Of The Belt, The Belt Compounding And Tooth Configurations Are Designed For Specific Applications Ranging From Normal Service To High Performance And High Temperature Engines"
Gates www.gates.com T196
GATES TIMING BELT -- A High Quality Timing Belt, Pitch 0.375" x 81.125" x 1"
Gates is the only manufacturer approved by virtually every major OEM to
provide timing belts for new engines.
This means that Gates is able to cover the aftermarket with timing belts that are OE-equivalent or better in service life and performance.
Gates also has the largest selection of timing component kits for the aftermarket, with 75 percent of its kits being specified for import vehicles. Each kit for 1974 - 2004 model years contains all the parts needed for a timing belt system replacement: one or more timing belts, idlers and/or tensioners, and detailed instructions
Porsche Spare part number Nr. 928 1051 571 0, 573 0, 574 0, 575 0
Porsche 928 4.6 S 8.83 - 7.86 228 KW Coupe
9.79 - 7.83 221 KW Coupe
928 4.9 S 9.85 - 5.94 212 KW Coupe
S S 4 8.86 - 7.91 235 KW Coupe
928 5,0 GT 1.89 - 7.91 243 KW Coupe
5.0 S 4 KAT 8.86- 7.91 235 KW
5.4 GTS 8.91 -11.95 257 KW
Conti Timing belt: Timingbelt by ContiTech.pdf
5098 XS - 58219 x 1 HSN
1982-> : 4.5 16v
1982-> : 4.7s 16v
1984-> : 5.0s 16v
1986-> : 5.0gt 32v
1991-> : 5.4 32v
•Number of Teeth: 219
•Width: 25,4 mm
Belt Drive / Timing Belt