Triumph Bonneville Motorcycle Chain Sizes Explained
First off, we should explain that this article is written around Triumph motorcycle chains for the modern Triumph retro range of motorcycles, from 2017 onwards, covering the T100, T120, Scrambler, Street Twin, Speed Twin, Thruxton and Bobber variants.
The Triumph Bonneville range of motorcycles (2017>) use different chain sizes across the range, all based on a 5/8-inch (15.875mm) pitch. These Triumph motorcycle chains are commonly referred to by Triumph OEM and aftermarket manufacturers (such as D.I.D), by the prefix “5” (representing 5/8 of an inch).
The distance between the inner chain plates (Width) and number links (Length) varies from model to model, explained later. We’ll start with the triumph motorcycle chain pitch measurement.
Chain Pitch Measurement:
Example: 520 specification chain, the ‘5’ refers to the pitch.
The pitch is the distance between the centre of the pins that hold the links together, as shown below.
The pins are 5/8 of an inch or 15.875mm apart, which is common for Triumph motorcycle chains across the Triumph liquid cooled retro range of motorcycles.
Inner Plate Measurement:
Example: 520 specification chain, the ‘20’ refers to the distance between the inner plates.
The internal width between the plates is also measured in 1/8 inch. It’s a little confusing but essentially the 5‘20’ in this case represents 2.0 x 1/8’s of an inch which is equivalent to 6.35mm.
If the chain was a 5’25’ the 25 would represent 2.5 x 1/8 inch which is equivalent to 8mm.
Chain links:
The final measurement is the length of the chain, measured in links.
May sound simple, but you only count the complete links; starting with the first complete link and then finishing with the ‘connecting link’ at the end. It’s easier just to count the even numbers, in increments of 2; all Triumph motorcycle chains should have an even number of links.
Triumph Motorcycle Chain 520 Type
Suitable for:
- T100 (2017>) [102 Link]
- Street Cup (2017>) [102 Link]
- Street Scrambler (2017>) [102 Link]
- Street Twin (2016>) [102 Link]
Synonymous with 900cc Triumphs
Internal width between plates: 1/8 inch.
The “20” indicates 2 x 1/8 inch = 1/4 inch (6.35mm).
Total width: 20mm to 21.5mm.
Triumph Motorcycle Chain 525 Type
Suitable for:
- T120 (2017>) [100 Link]
- Bobber (2017>) [108 Link]
Synonymous with 1200cc Triumphs
Internal width between plates: 1/8 inch.
The “25” indicates 2.5 x 1/8 inch = 5/16 inch (8mm).
Total width: 22.6mm to 23.7mm.
Recommended Triumph motorcycle chain maintenance
Sealed Chains:
Use exclusive oils that are seal-ring safe for cleaning and lubricating drive chains. Clean the chain by wiping it with a soft cloth dampened with an O-Ring/X-Ring safe cleaner and dry it completely every 300 miles (500 km) to prevent surface rust and ensure maximum performance. Do not use steam, thinner, volatile solvents like gasoline or benzene, or a wire brush on the chain. Lubricate the chain every other use with an O-Ring/X-Ring safe lubricant.
Replacement Schedule:
Sealed chains should be replaced when stretched by 1% of their length, and non-sealed chains by 2% of their length. For a 120L chain, this means 0.75 inches for sealed chains and 1.5 inches for non-sealed chains. Rust, stiffness, or missing X-Rings may cause premature chain failure. Replace the chain and sprockets if you notice any of these issues, excessive elongation, or abnormal noise during use.
Corrosive Materials:
If battery acid contacts the chain, replace the entire chain as it may compromise its integrity. Clean the chain promptly if it comes into contact with corrosive materials like rock salt.
Replacing Sprockets:
Replace sprockets when wear approaches the maximum permissible limit or if they sustain damage that could affect safe riding. For replacement enquiries, contact your local Triumph dealer service department.
Overall Condition:
The overall condition and quality of the chain system impact sprocket performance and lifespan. Check for wear, adjustment, and alignment when replacing sprockets. Avoid changing the chain size, type, or sprocket tooth number and size as specified by your motorcycle manufacturer for street-legal use.
PLEASE NOTE: The information in this article is to be used as a guide only. If you are not a qualified mechanic, please instruct a professional to carry out work on your behalf.
For advice, please contact your local Triumph dealer service department.