(Top) Replacing wear and tear components is a part of dirt bike ownership. (Center) The Mid-Soft 32 rear tire offered great grip and feel but the knobs started to break off at around five hours of riding time. (Bottom) A one tooth larger rear sprocket (49) made the engine feel snappier and eliminated engine stalling in slow corners with the engine lugging at low rpm.
Replacing wear and tear components is a part of the fun of owning and riding a dirt bike. The stock tires and chain drive and sprockets are a few parts that require routine replacement, so we sourced a set of Pirelli’s latest motocross tires and a chain and sprockets from Renthal for our 2012 Honda CRF450R motocrosser.
Although Pirelli has been slow to gain traction within the American motocross scene, worldwide it’s seen much success with its updated-for-2012 Scorpion tire. With about 15 hours on the meter we replaced the worn-out knobbies with a Pirelli MXMH 554 Front Tire (Mid-Hard 80/100-21) and a wider Pirelli MXMS Rear Tire (Mid-Soft 32, 120/90-19).
One of the big features of Pirelli’s off-road tires is the wide range of constructions to choose from based on terrain or handling preference. The 554 model is the “intermediate” tire option and it features a flatter, less angular profile when compared to other brand-name MX tires. The tread pattern is designed to maximize the contact patch when straight up and down and at lean. The 32 is designed for use in softer, looser terrain and uses a unique tread pattern designed for riding in gravel and light sand or mud.
We spent most of time riding at Southern California’s Zaca Station (deep loam in the morning, hard pack/sand in the afternoon) and Perris Raceway (soft-to-intermediate conditions all-day) and the tires proved to work well there. The carcass has a good rigidity balance and didn’t feel overly stiff or soft and grip levels were as good as anything else we’ve tested. Durability-wise we got a fair amount of riding time on the front tire, but the knobs on the rear started to chunk after about five hours of riding. Overall the tires performed well, but we wish we could have gotten a little more time out of the rear Mid-Soft.
Although the stock chain and sprockets were in decent shape after 15 hours, we experienced a propensity to stall the bike in slower second-gear corners. To fix the problem we lowered the gear ratio by fitting a one tooth larger Renthal 520 Ultralight Off-Road Rear Sprocket (49). This would allow the engine to carry added rpm at a given speed as well as improving acceleration slightly. While we were at it, we fitted a Renthal 520 Ultralight Front Countershaft Sprocket (stock size – 13) and a fresh gold Renthal 520 R1 Works Chain.
Not only did the change in gearing eliminate the low-speed engine stalling issue, it also improved acceleration and made the engine feel more ‘snappy’. For only $52 it was a noticeable improvement and a worthy upgrade for those looking for added performance. We were also impressed by how resistant the R1 chain was to stretching. Over the course of the summer we amassed upwards of 25 hours on the Renthal set-up and, at our novice pace, the components are wearing evenly and still have hours of life left in them.
(Left) The carcass of the updated Pirelli Scorpion tires offers good rigidity balance and isn’t too hard nor soft.. (Right) The Renthal gearing proves to be more durable than stock with the chain requiring less routine maintenance due to stretching.