Maxxis Maxxcross MX-SI Tires

I am not going to sit here and blow smoke up your asses and tell you that I venture very far offwhen it comes to my personal choice in tires. Dunlop and Pirelli have dominated most of my personal riding time when it comes down to racing. However, I do test different brands of tires A LOT when it comes to production testing and run into the occasional “pot of gold” as far as lean angle traction goes. It is tough for a tire manufacturer to make a motocross tire that is great on durability and great on traction. You have to pick a side, people! Yes, you may get a blend of both but I can guarantee you that one will outweigh the other when it comes to rubber on your motorcycle. I will also be honest with you, I wasn’t a huge fan of the previous generation Maxxis Maxxcross tires. When brand new they were decent and I could live with them. But anything over a couple hours I found myself looking for lean angle grip and had problems with side knobs chunking way too soon in my opinion. Fast forward to the summer of 2023 and Maxxis has introduced a brand new performance tire that was developed with “The King” Jeremy McGrath once again exclusively for us die hard moto guys called the Maxxcross MX-SI. The SI features changes with its tread design from the ST. The main points for the MX-SI is that the mold/tread pattern design has been improved to provide better block rigidity. The biggest point of improvement for the Maxxis engineers was to increase stiffness from the ST.  At first glance it almost looks like a Pirelli Scorpion MX32 tread pattern design with a slightly different side wall/side knobs, but once evaluated closer you can tell the difference. I ran a set of 80/100-21 and 120/90-19’s MX-SI’s for just over ten engine hours and wanted to compare these new MX-SI’s with the older Maxxis Maxxcross design. I will be doing some more back to back tire tests soon, because I know how all of you love comparisons.

Rear Tire:

I found that the first thing that impressed me was that the Maxxis Maxxcross MX-SI rear tire offers great forward bite (traction) under acceleration (out of corners) in intermediate/soft terrain through ruts and coming out of corners. The Maxxis side knob design works slightly better under lean angle compared to the ST and traction is one of the MX-SI’s (rear tire) strong suits, as the rider is able to get on the throttle sooner (while leaning) without washing out (compared to the ST). You are also able to start your lean sooner (than any other Maxxis tire I have tried in the past) while coming into a corner and the MX-SI remains planted to the ground. Braking predictability is also increased as it gives the rider confidence to pivot and throttle out of flat corners without much hesitation. Previous Maxxis tire compounds would step out (or wash out) on you once you completed your braking and were back on the throttle, but the MX-SI lets you pivot/lean under throttle through flat corners adequately. One complaint I had is that when the track surface was freshly watered/slightly hard, I couldn’t get as much predictability from the rear tire as I wanted. It gave me a pushing or loose feeling rear end until the track tacked up somewhat. Running the correct air pressure in the MX-SI tires is crucial as I found the happy setting at 13 psi for most conditions. If you find yourself washing a little on intermediate terrain don’t be scared to go to 12.5 in the rear. The stiffer nature of the MX-SI carcass still absorbs bigger bumps/square edges well despite it tougher carcass on paper. When you normally get a harder carcass tire, the rider usually feels harshness or deflection when the track deteriorates but Maxxis did a good job at keeping most of that squish feeling at a friendly level for the average consumer. I did notice around the 8 hour mark that the Maxxis rear tire performance gets less predictable and feels much like a worn Pirelli MX32 mid-soft tire, which to me is to be expected, but nonetheless needs to be noted. The Maxxis MX-SI rear tire loses most of that “predictability” (when 8 hours old) on lean angle (coming into corners), which causes the rear end to wash/slide out easier under throttle. I do want to note that some of you MAY NOT FEEL THIS! I am super sensitive to tire consistency as I was brought up in the Doug Dubach era of tire testing for days on end. Kudos to Maxxis for making a rear tire that doesn’t chunk before the 10 hour mark. I have chunked some Pirelli MX32 Mid-Soft tires before the ten hour mark (under normal intermediate terrain), but as of right now the Maxxis rubber hasn’t broken apart . If you are using the MX-SI rear tire on pure sand, the lifespan of the tire goes up exponentially, so just know this. Also note that if you’re using this tire in hard pack conditions the compound/knob will wear much sooner. This is by far the best rear tire Maxxis has put out to date so a job well done to the guys one there! Weight: 120/80-19 = 12 lbs.

Front Tire:

I am kind of a nutball when it comes to front tires! The Maxxis MX-SI front tire is much better for front-end feel and lean angle traction than the ST, in hard pack conditions. The MX-SI front tire actually can now bite not only in soft soil, but also in looser hard pack soil as well. I notice more traction on the hard pack side compared to the ST. When the ground is soft with traction I don’t notice a much better feel on the SI compared to the ST, but when the track gets the good dirt pushed off, the SI is much better. The MX-SI front tire will accommodate the moderate front end steering rider and is able to be leaned into corners fairly aggressively. The contact patch feel on lean angle is much wider on the MX-SI than a Bridgestone Battlecross X20 or 30. I actually got to ride the X20/30 front tire back to back with the SI and noticed a more predictable initiation into corners with the SI. Previous generation Maxxis front tires were NOT even in the conversation, but now we can at least have an option when choosing a front tire amongst the other big four companies (Dunlop, Pirelli, Bridgestone, Michelin). Acceleration on lean angle traction (on the MX SI) is not quite as predictable as it is on de-cel however. If accelerating on a fast sweeper, the front tire does want to “hunt and peck” somewhat. What is “hunt and peck”? Hunt and peck is a testing term we use when the tire feels like it is moving underneath you and doesn’t feel planted. Or another word would be a narrower contact patch feel. Off-throttle planted sensation is great, but on-throttle sensation, I notice the front tire moves around and deflects a little more than I would like. When the track had just been freshly watered (wet slick) and was slick on top (think of the second moto in late afternoon at a Southern California type of track) the MX-SI also loses a little predictability. On dry slick this tire gives me more confidence, but when watered that contact patch feel goes down more than I would like. This kind of condition would give the front end a vague feel (pushing sensation) as the bike would have a tendency to slide the front-end through flat corners more. I found that going up slightly in air pressure helps this out tremendously and gives the front end less push. The best recommend air pressure is 13.5 psi as I get a little more predictability in wet slick conditions with this pressure. The wear of the MX-SI front tire is also much better and hasn’t shown signs of chunking yet, which is also another improvement for the Maxxis brand. You can go down in pressure on a softer track (12.5) but I stick with around 13-13.5 mostly here in So. Cal. Weight: 80/100-21 = 9.12 lbs.

The Maxxis SI is a better tire than the ST. Plain and simple! How does it rank against a Dunlop MX34 or Pirelli MX32 in performance? Stay tuned, I will be doing this test shortly. If you like the Maxxis product, you will love this new SI tire. Another tip of that hat to Maxxis on the price point as well, which is better than when I complained about it earlier with the ST! $97.00 for the 80/100-21 and $117.00 for a 120/80-19 is in the ballpark of other top players in the soft to intermediate category now!

Any questions please free to email me at kris@keeferinctesting.com