Review: Gamut P20S ‘O-Ring’ Chain Guide

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In this day in age, the chainguide holy grail consists of more than just a product designed to keep your chain on, but something that is both lightweight, easy to install, as maintenance free as possible and of course, easy on the eye. With such high expectations for component quality, sometimes you’ve just got to step outside the box and see how things can be done differently to improve on what you would once have considered nothing more than an existing design. Gamut did exactly that with their latest guide, removing the almost standard ‘sealed-bearing’ based jockey wheel or roller and instead, replacing it with an O-ring. Yeah, a rubber O-ring, like the ones you find in washing machines and just about anything that requires a robust seal. Sound good or does it sound a bit random? We’ve had this new guide on review for a few months now and this is what we found…

Words: Olly Forster | Photos: Nathan Carvell & Olly Forster

This is the sum of it’s parts as you open the box – pretty simple and almost ready to whip on your bike, almost…. If this is going on a standard chainset, you will need some longer chainring bolts which are unfortunately not included. Gamut do make some, and rather nice they are too, but with this guide, they are not?

No bearings, sealed or unsealed and no moving parts, just a rubber O-ring – to the seasoned trasher of parts and the rider with a practical disposition, this should sound hopefully like the ultimate winter guide? With the constant barrage of water, oil and grit, any sealed unit supporting moving parts will get a real battering from the elements and I’m sure I’m not the only one to either drag the trail into the lower part of their guide on more than a few occasions, but to also find a jammed bearing preventing the whole system from working correctly? This design eliminates these problems instantly!

Although the bashguard design utilised here was once highly favoured by a number of manufacturers, notably MRP and e*thirteen – who have now moved on in favour of developing their open ‘taco’ based designs… Although the ‘open’ design is inherently lighter, this bashguard option is not only tried and tested, but also removes the danger of any lower part of the guide contacting the trail and potentially damaging the frame due to forced rotation on the ISCG tabs – bending your cranks/spiders ‘vs’ damaging your ISCG tabs? No contest really and the Gamut bashguide is as tough as it is light – and it is very light! The whole guide, bolts and washers included is only 190 grams!

Pretty cool looking bashguard! Designed to not only help keep your chain on, but to also glide over rocks and trail features and being attached to your cranks, offers a degree of rotation, which could make all the difference.

The top part of the guide is consists of exactly that, a guide – the simple approach of the P20S makes it really easy to install, quiet in use and also easy to adjust…

…using this neat system where by you add these neat triangular plastic spacers to the rear of the guides and a great solution to the pain of fiddling with washers and spacers on the ISCG bolts… This design allows you to very quickly gauge sufficient clearance either side of the chainring and get you and your ride on the trail in no time. The black bolt at the top threads directly into the boomerang from the front of the guide and the white bit below acts as a guide to hold the spacers in place. Simple as really!

Gamut’s crazy light ‘Race’ chainrings are made from hard anodised 7075 alloy and feature a thicker than normal design with deeper cut teeth to ensure maximum chain contact. Available in every size from 32 all the way to 40 – including odd numbers too. We ran a 34T, which pretty much weighed it’s weight in teeth to grams, but all this comes at a cost – with an RRP of £35, it’s no drop in the ocean, but if you want quality parts to finish your ride with, you know what you’ve gotta do…

On the Trail.

With the ease of installation done and dusted, it was time to hit the dirt and see how the P20S performs in the wild and it didn’t take long to notice how quite it is, even in the sludge we’ve had to deal with recently here in the UK. Another thing you notice, and rather quickly, is the level of drag through the drivetrain… At first you may think it’s the O-ring, but no, it’s the ‘factory’ configuration of the boomerang – the O-ring certainly doesn’t improve drag, but the weigh off over a conventional design, even at this time of year, will certainly pay off for the rider venturing off the beaten track. Back to the boomerang…

We had the boomerang positioned to have the least amount of resistance through the system and you can see from the photo below, you can see just how close the lower guide it to the chainstay. Too much resistance? Running this on a 1 x 10 equipped trail bike? There is a solution…

By flipping the boomerang over, removing and re-installing all the parts to the opposite side – problem solved! In all honesty, if your using this for trail/enduro, I’d do this from the off! For DH? I’d be tempted to leave it as it comes from the box as the tension on the chain makes for responsive feel through the cranks, which I feel serves well in a stop, start discipline like downhill, but the choice is there!

Like I’ve mentioned earlier, the O-ring design is essentially a maintenance free unit and with a spare O-ring in the box, you’ll get more than a season or two out of it before you need to replace it and when you do, it’s going to be a lot cheaper than a new roller or specific jockey wheel that’s for sure, and the best thing, is that you don’t need to worry about anything breaking or seizing!


As far as chainguides are concerned, the P20S performed amazingly well and kept the chain in place throughout. Any initial issues with too much resistance on a 1 x 10 ‘trail bike’ platform, were quickly overcome, especially if you think outside the box and fully utilize the P20S’s simplistic design to your own personal needs. It’s also the Gamut’s simplicity that initially put a smile on my face, especially the the plastic guide spacers, which were spot on and seemed to take the sting out of the usual chainguide installation process. The ISCG bolts aren’t the best, but as long as you don’t go overboard on the torque, you’ll be fine and remember – non-counter sunk bolts mean you can swap the boomerang around, which is definitely worth doing like I’ve already mentioned and a pretty cool feature.

Negatives? Not really in all honesty, any that were on the horizon, soon disappeared as I set the guide up to suit both the bike and the riding. Some longer chainring bolts in the box perhaps, but riders with existing 1 x 10 or 1 x 9 set ups will already have these anyway…. The quality is tip-top and the attention to detail is of a high standard and present throughout and coming in at £100, it’s bang on against e*thirteen and cheaper than MRP. It’s light and a good looking bit of kit that definitely doesn’t detract from a sweet looking bike build, and it certainly looked the part on our long term test bike.

If you ride a lot of DH or even rack the miles up on forest singletrack where rocks, roots, sticks, ruts and mud are the norm, your bike receives a particular kind of beating that comes from below and that’s exactly where this O-ring design comes into it’s own. With no moving parts to seize from that after ride wash and with nothing to clog up with vegetation samples, the only downside is remembering that dirt builds up between the chainring and the bashguard, but a cassette brush makes light work of that!

All in all, the P20S represents a fantastic chainguide that would be great for anyone who spends their time away from man made trails and likes to get into the thick of it, without worrying about their bike failing due to chainguide issues. Expensive? Not especially considering the high quality manufacturing and uniqueness that makes the P20S stand out from the crowd. Ultimately a great product that should tick a lot of peoples box’s, and if your in the market for a new chainguide, then you need to check the P20S out as it could be exactly what you’ve been looking for?

Gamut is exclusively distributed in the UK by Madison and for everything Gamut, hit the logo below. Happy Trails!




In Reviews


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