Decathlon’s Rockrider ST-100 is a ‘leisure’ mountain bike with 80mm of front suspension, 21 gears, strong V-brakes, and surprisingly good tyres for casual messing about in the woods and the odd bit of gentle trail excursion. It’s not designed for more aggressive riding and the sizing is a little out but it does offer a lot of fun for £230.
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The Rockrider ST-100 frame is made from 6061 aluminium with large obvious welds and a distinctly bent seat stays behind the seatpost that gives an indication of potential comfort designed into the frame. The seat stays have rack mounts on both the top and bottom and a set of mudguard eyelets which is useful if you intend to ride the bike to work, college or school. The bottom set of fixing mounts are occupied by the derailleur protector but longer bolts will allow both a mudguard and rack to be fitted.
Perhaps more importantly for the intended leisure audience is that the ST-100 is available in two colours, dark grey and fluo yellow for the unisex version and a white-and-pink version for the women’s version. Both versions are available in five sizes from XS to XL with 27.5-inch wheels with the smallest XS model coming with a 26-inch wheels. The women’s model also benefits from a slightly different saddle.
Decathlon lists two slightly different versions of the ST -100 on its site with the only difference being the fork, but both forks offer 80mm of travel with preload being the only adjustment available. This might be a running change due to supply issues caused by the COVID-19 pandemic.
Rockrider presents the ST-100 as 'your first mountain bike' or perhaps first ‘touring’ mountain bike and states that it is not designed for XC, Trail, Enduro or BMX style riding – which presumably means jumping. I read that as it’s designed for leisurely use around local parks, bridleways and forest centres to get you out in the fresh air to experience a little bit of off-road in your neighbourhood. However, looking at the pictures on the Decathlon site the company seems to suggest that rooted, dusty trails could be ridden on the Rockrider so using that as my guideline I took it to Ashton Court in Bristol - a popular trail centre with a non-technical trail that only becomes difficult if you push the bike hard and fast. You will often see a family on the trail at the same time as a Strava nut so it’s really suitable for anybody and perfect test for this bike.
My first impressions of the bike, other than that bright colour, are that it is pretty small for a large. I’m fairly well centred in the size range at 180cm (174-184cm) but I would have happily gone up a size (or two if they had made an XXL) so it's definitely worth double checking the size before you buy - which is the standard advice as always.
Setting the bike up was simple. Pretty much everything worked smoothly out of the box with just a very slight toe-in adjustment to the V-brakes to stop some hideous squealing. A simple task with a hex key for an ex-shop rat like me, but you might need help here if this is your first bike. They shouldn’t squeal, they should just stop. Once adjusted I was rewarded with a decently powerful brake set-up, albeit it was dry during the test period.
Adjusting the SR Suntour Rockrider fork was fairly straightforward as there was only a preload adjustment to play with on top of each leg. Bizarrely the left leg had 12 clicks and the right leg had nine. I'm not sure what that is about but winding the preload adjuster balances the amount force required to make the fork move versus the weight of the rider. With it unwound all the way, the fork dived too quickly for my body weight so opted for three clicks back from open on both legs which seemed to provide the right balance. With 9-12 clicks, you should be able to find an acceptable level between the fork diving and it providing some support when you're riding. There are no mudguard mounts on the fork which means you'll need a clip-on style mudguard if you intend to commute with it.
Shifting duties are taken care of by B'Twin-branded shifters and rear mech which, according to the site, are Microshift units and they worked rather well which was a pleasant surprise. As this is likely to be your first foray into mountain-bike-style gearing, they are simple to use and offer a useful gear number indicator on the twist-grip shifter which might be helpful to some users.
The ST-100 has 21 gears for you to choose from, the right-hand lever controls the rear derailleur with gears 1-7 marked on the shifter, and the left hand lever controls the front derailleur with rings 1-3 marked on the shifter. The ST-100 comes with a derailleur protector as well which is a useful addition for excitable children dropping their bikes in a hurry. This way the protector takes a beating not the derailleur.
The chainset is a black triple option with a chainring guide to help prevent chewed jeans. It's a classic set-up comprising 22-, 32-, 42-tooth rings giving a sensible spread of gears. The 22T front ring mated to a Shimano 28T rear cassette means that the ST-100 offers a good hill climbing gear so you should be able to get around most family trails and parks without too much trouble.
The B'Twin twist shifters do rob the handlebar of space (versus a band-on style trigger shifter) and it’s not the widest bar to start with at 620mm. I think a 700mm + bar would offer a little more control to enjoy the trails and that would seem a simple and cheap change on the spec sheet for Decathlon.
Both stem and handlebar are from an older design standard where the bar clamp diameter is 25.4mm whereas most mountain bike bars have been 31.8 for a decade or more. This is worth mentioning as the options for wider 25.4mm handlebars are not as common should you chose to upgrade later. You could of course choose to swap the stem and bar at the same time but that would incur extra costs.
Both the wheels are alloy rimmed and anodised (not painted) with 28 spokes which means that those V-brakes will grip much better than on cheaper bikes with painted rims. Again, this is good specing and while visually similar on the shop floor will provide much better grip weeks and months down the road, sorry trail.
It's worth noting that while the Rockrider ST-100 comes fitted with a quick-release front wheel for easy removal, it has a bolted rear wheel so you will need to remember a 15mm spanner alongside a mini tool (tyre lever and tube and pump) when you got for a ride otherwise you might get stranded or have to walk home if you get a puncture in the rear wheel .
The ST-100 is clearly designed to allow you to look up and enjoy nature as you ride past it. It is not designed to be hustled along family trails in an XC or Trail fashion and I would wholeheartedly agree with the Decathlon usage category here.
Riding along the smooth trail around the outer edge of Ashton Court, the Rockrider ST-100 was in its comfort zone. It can cope perfectly well with a well-groomed trail with smooth rollers and berms with the head-up position providing plenty of visibility and giving you a chance to adjust your speed with strong-performing brakes and grippy tyres.
There is official geometry for the fluo yello version but it looks to have the same frame as the women’s ST-100 version with a 69.5-degree headtube, 73-degree seat tube and a reach, on this Large version, of 429mm. That is pretty short by modern XC mountain bike standards and very short by Trail bike standards of 2022; but this is neither of those style bikes and is designed for a more leisurely head-up and more upright position than a more aggressive mountain bike.
The geometry is really quite conservative and makes the bike feel pretty short and steep. This has no real impact on riding around the streets, taking in the odd towpath, or park but it does mean that any extra enthusiasm from the rider is not rewarded by a bike that’s eager to go faster.
Pushing the ST-100 harder into the trail sections highlights the design limitations of a leisure bike. The position is not conducive for such riding and I felt dangerously over the front on several fast corners. Small drops of a few inches were handled without too much complaint from the fork but the frame held no prisoners and hammered me for riding too hard. The 6061 tubing is probably plain gauge throughout and there is little compliance designed into the frame, despite those bent seat stays, so consistent hits to the rear wheel are felt through the saddle.
The extra-long small-diameter seatpost does offer some level of compliance from these hits and was a wise spec choice but had Decathlon specced a large-diameter (and therefore stiffer) seatpost, I suspect I might have needed to see my physio afterward.
The Rockrider All Terrain DRY-branded tyres provided the largest surprise on the test being fast rolling and predictable at sensible angles not to mention offered a lot of confidence when picking up the speed on the famous Ashton Court ‘Quarry run’. The dry grip was plentiful and I had a lot of fun blasting the berms.
Decathlon says the bike is designed for up to rides of 90 minutes which is an odd design parameter and I’m not sure why it put a time on it – our test bike didn’t turn into a pumpkin after that time and the saddle was still comfortable. It was, however, evident that the frame was not very forgiving - maybe that's what they were referring to on the site.
The ST-100 is a well-specced bike for its asking price and one that should outlast a lot of its direct competitors. GoOutdoors, always one to offer great bikes in the past especially with its loyalty card giving you great discounts, has a Compass Lattitude at £220 down from £350 with an even steeper head tube, 21-speed and a suspension fork, but only in M or L. They also offer a Barracuda Montana with a similar spec but with a front disc brake in S and M. Spend a bit more money and there is Barracuda Colorado at £280 with twin discs and 24-speed gears. Halfords offers an Apollo Evade in S, M or L with Twin disc brakes at £235 but the forks are not adjustable and the geometry looks even steeper than the Compass or the Rockrider.
The ST-100 is pretty alone in offering five sizes and a selection of colours and the V-brakes are not as good in the wet as good disc brakes. Cheap cable-actuated disc brakes do not cover themselves in glory typically either. It also appears to be marginally lighter than many of its competitors at 15.6kg for a Large.
The ST-100 is an honest leisure-use off-road bike that will reward you with fun in the local park and along the bridleways. It is not a ‘mountain bike’ by Decathlon’s own definition so no XC or Trail riding and certainly no BMX jumping à la Kye Whyte. It could do with a wider bar, a rear QR axle to match the front, and a geometry tweak to make it more rewarding off-road but, for the money, it’s a good option for your first off-road bike. Just make sure you check the sizing.