While not the first or only people to fabricate a chain retention device, MRP is arguably the first to do it properly. When the System 1 was first produced in 1996 it set a precedent for chain guides. When a lot of other people were installing spring loaded derailleur tensioners or chain stay mounted rollers, MRP began to produce the simplest solution to what turned out to be a not so simple problem. As time passed, bike designs evolved, and so did the rider's skill. Their line of guides also expanded to include the System 2, the many options of the System 3, and the latest design, the MRP G2
I've spent the last few months trying to do my worst to the G2. Want to know how it worked? Read on......Overview
The goal of the G2 was to produce a light weight chain guide that provided more protection, while still retaining the security that MRP has become known for. A complete redesign was in order to produce the stoutest guide possible.
Obviously the first change that you'll notice is the lack of an outer chain guide plate or bash guard. The bottom bracket and crank (more specifically the spider/chainring tabs) have long been the weakest link in any guides design. No matter how tough a plate is made, it is only as strong as the crank it's attached to. The conundrum though is that there needs to be some sort of protection of the chainring for any rider that is pushing themselves, regardless if that's racing, jumping, or just pinning about in general. The answer was to mount the guard itself onto the boomerang, which can be built tough and if worse comes to worse, is cheaper to replace than a crank set.
Poly skid plate. Notice the 3 attachment points
The guard itself is a polycarbonate affair that sits just inboard of the chainring and extends out far enough to cover a 40 tooth ring. If you don't think your bird legs can turn that over, or you're at a course that demands a smaller ring, you're in luck as the G2 will work with 36 or 38 tooth rings also. It is attached to the boomerang at three points
using easy to find chainring bolts. How and where it connects to the strengthened boomerang is key to the G2's ability to roll with the hits. More accurately, how it slides
over the hits. Instead of simply placing the poly skid in front of the ring, it extends all the back to envelope and protect the lower guide pulley. The result is not only having added protection and strength, but also knowing that you won't "hang up" on whichever obstacle you have found yourself upon.
Backside of upper boomerang with relief channels and slot
If the skid plate is strong then the boomerang that it's attached to needs to be able to take a shit kicking. MRP's 5 mm think alloy boomerang is a step beyond what was offered before. Instead of a simple flat unit, both ends of the boomerang have reliefs machined into the back side that both reduce weight and allow for the upper and lower guides to be slid up and down without twisting out of line. The skids three attachment points that spread out to cover the entire lower section of the boomerang also add strength and stiffness to one of the most vulnerable areas on a bike.
The Keepers Of The Chains differ from other MRP guides in that the top unit is no longer a urethane pulley wheel, but a resin cage enclosed over the chain. MRP saved a considerable amount of weight as the pulley wheels were attached using M6 steel screws, as well as rolling on two sealed bearings. The new cage style system is held on with a much lighter single screw and nyloc nut. Light is right but the biggest benefit may be how easy it is to clean debris and mud through the guide's cutaway. The lower guide still spins on a sealed bearing, but it's a toothed pulley wheel instead of the larger smooth units found on the System 1, 2, and 3. The chain is sandwiched between part of the poly skid plate and the resin outer shield. Just like the upper guide, it is held in place a single screw.
Installing a chain guide can be a daunting task for someone who does not do it often. In fact, I would say that after wheel building it is the most time consuming part of putting any DH bike together. There are guidelines of course, as to how many spacers to use and where to put them, but in the end it comes down to trial and error in most cases. Removing cranks and bottom brackets gets real old after the third of fourth time and it's not something that I look forward to doing on a regular basis. I'll admit I was pretty happy with my System 3 Carbon
and I let the G2 sit on shelf for a few days before finding the time to put it on. When I did find the time though I discovered that I didn't need much of it after all. Granted it will be different from bike to bike, but on my personal 224 I needed no spacers. Nothing under the drive side B.B. cup and nothing between the boomerang and the ISCG tabs means that my chain line remained as close to original as possible. Always a good thing.
Once the G2 was attached to the bike it was easy to adjust it to the proper angle due to the lack of a plate to get in the way. Instead of needing to remove the crank to access the countersunk screws, I could reach right through to make any adjustments that were needed. In fact, if I had needed to use a few spacers between the boomerang and frame I would not have even needed to remove the crank arm. Very easy so far.
The upper guide is held together with the same screw that holds it onto the boomerang. Fit it over the chain and set it at the appropriate height
For those of you who do your own work this guide will be perfect. I've had to install nearly every guide that's out there numerous times and the G2 has been the most pain free so far, even easier than the System 3.
How Does It Work?
Removing my trusted System 3 and installing the G2 may have been easy, but it took a leap of faith to make the swap on my end. I had no troubles with my System 3, so why change? Having the added protection of the poly skid plate while still keeping the weight down was a big draw for me. In use the G2 was invisible until I needed it, which is the first sign of a good product. I never lost a chain, and don't expect to anytime soon. That's the obvious job a guide needs to perform, but what about the not so obvious? I had it mounted to a Cove Shocker for a bit, a bike that has quite a bit more chain noise than my current ride, an Orange 224. The G2 on the Shocker produced a much quieter ride than other guides I've used. The upper guide kept the chain in check and off the frame more than the standard roller which was nice. A silent bike always feels like a faster bike.
I got another chance to install the G2 again when I made the switch back to my trusty 224. Again, no spacers were needed and I was able to preserve the Orange's excellent chain line. One issue I was concerned about was contact between the chain and upper guide. With a urethane roller set at the height there is very little friction or wear, how would the resin cage do over time? Following MRP's instructions I made sure the chain was inline with the split in the cage, centered perfectly over my Wipperman chain. The cage is actually just wide enough to allow me to go from one extreme to another on my cassette without it making any real contact with the inside of it. I use my DH bike for a lot more than shuttle runs, so a free running drivetrain is pretty important to me. There are guides on the market that are designed so that the chain makes contact with the retention device at one extreme of the gear range, small beans to some but unacceptable to me. That's not to say it never rubs. After a few months of use I can see where the chain has come in contact with the cage and left a very small amount of wear. At this rate it would take many years before I would need to replace the part.
The poly skid plate has also come in handy on more than one occasion. Every now and then I'll misjudge something (don't we all?) and come up a wee short. It shows no signs of slowing down, let alone even a nick or chip. The extra length of the skid plate towards the back of the guide has prevented any damage to the lower roller and it has kept spinning smoothly despite my best efforts. As I would have hoped everything is still as straight as the day it was installed. If disaster does strike, all parts are available separately so you'll only need to replace what is needed.
There are other guides on the market, some that look similar to the G2 and some that don't. A few details set the G2 apart from the pack though. The first is the amount of protection you get with the G2. The poly skid plate is used on other guides but none of them take it as far as MRP. The G2's armor extends farther back to fully protect the lower pulley and keep things running smooth. If it's there it may as well protect the entire guide and not just the chainring alone, right? The other advantage the G2 has is the lack of drag. This thing is damn smooth, and that's not what I expected from a guide that uses a stationary upper cage instead of a roller. Follow your instructions and install it properly and it will run drag free for you also.
If you have read my other reviews than it's no secret that I am a fan of MRP products, but if there was something better out there I would be using it instead. Just keeping a chain from falling off is a relatively simple task, a guide needs to be able to do that and more. The G2 runs smoothly, keeps the noise to a minimum, and protects your drivetrain from any abuse you may try to inflict upon it. Available to fit both ISCG and ISCG '05, as well as bikes without chainguide tabs, you now have no excuse for loosing chains.Price
: Approx. $220 CDNLooking for more info on the G2 or other guides from MRP?
Mike "Kakah" Levy