Condensed Answer: A 29″ hardtail can be used for jumps but isn’t optimal for that task due to its size, weight, and overall geometry. If jumps rather than trails are a priority, a dedicated dirt jumper would be a better choice.
The Downsides Of Using a 29″ Hardtail For Jumps
- Large wheels
The main advantage of 29″ wheels over smaller wheel sizes is their roll-over-ability. Or in other words, 29″ wheels have an easier time rolling over obstacles.
This makes them better for quick riding on off-road terrain, but the extra diameter hurts the maneuverability of the bike and thus makes it more difficult to perform technical stunts.
Conversely, standard dirt jumpers use 24″ or 26″ wheels with 26″ being the most common wheel size. This is a deliberate choice rather than an attempt to remain in the past.
All parameters being equal, 26″ wheels are stronger than 29″ because the rim acts as a smaller lever against the spokes when the wheel faces an obstacle. Also, the shorter spokes make the wheel stiffer and thus more responsive – a beneficial quality for technical riding.
Another downside of 29″ wheels is that they accelerate slowly (it takes more effort to spin a larger wheel). This is a problem when using the bicycle for jumps because very often the space available for acceleration prior to the jump is limited.
Therefore, 26″ wheels excel in that situation because they’re smaller and easier to get up to speed quickly.
- Large frames
Most dirt jumpers come in one size whereas hardtails offer multiple options. The reason behind this phenomenon is simple – dirt jumpers are designed for jumps whereas hardtails have to offer comfortable pedaling.
The large frame of hardtails results in a heavy bike that’s difficult to manipulate in the air.
- Long chainstays
Hardtails have longer chainstays for two main reasons – stability and clearance to accommodate a 29″ wheel. Longer chainstays increase the wheelbase (the distance between the two axles) and make the bike more stable.
However, the longer chainstays make it more difficult to lift the front and rear wheel. Hence why it’s much easier to manual and bunny hop a dirt jumper than it is to do the same on a 29″ hardtail.
- Extra Weight
29″ Hardtails are heavier than jump bikes for the following reasons:
- Larger frame
- Extra parts (derailleurs, cassette, front brake)
- Larger wheels
The extra weight of 29″ hardtails complicates the executions of jumps and tricks.
- Overly Squishy Suspension
Hardtails are designed to conquer off-road terrain. Their front suspension reflects that and is often adjusted to adsorb even small obstacles. In the world of jumping, a soft suspension is not always desirable because it compresses too frequently, sometimes when the rider doesn’t want it, and hurts the overall feedback of the bike.
For that reason, dirt jumpers have a fairly firm suspension activated mostly during the landing of a jump.
This quality of hardtail suspension can be overcome by playing with the fork’s settings i.e. increasing the pressure if the fork operates with air.
- Super Slack Head Tube Angle
The head tube angle (HTA) is the angle formed by the head tube of the bike and the ground.
Modern hardtails have slack headtube angles in order to position the wheel in front of the rider and increase the bike’s stability when riding on mountain terrain at high-speed.
However, the slack headtube angle hurts the bike’s maneuverability at a slow speed. Hence why dirt jumpers come with a steeper headtube angle.
Cross Country Hardtails
A modern aggressive hardtail designed for trails may be imperfect for jumping due to the negatives listed above, but at least it’s strong enough to handle jumps.
However, there are also cross-country hardtails built for less aggressive terrain. Those models have major downsides that make jumping not only more difficult but potentially dangerous too. The issues are:
- Entry-level suspension
Many entry-level XC hardtails come with the cheapest Suntour forks. On the label of the fork, it’s clearly stated that the fork shouldn’t be used for aggressive riding which includes jumps. Thus, if the fork breaks, the warranty won’t cover the damages.
- Ancient Geometry
Some entry-level hardtails have a geometry that makes jumping a lot more difficult. Some of the issues are an unnecessarily steep HTA and very long chainstays. Those characteristics make the bike better for pedaling but truly hurt its jumping capabilities.
- Weak Wheels
The wheels on an entry-level XC hardtail are very likely to buckle when the bike is used for massive jumps.
- Weak Headtubes
The head tube is among the most stressed areas of the frame. If the bike isn’t built for aggressive riding, it’s possible to crack the frame due to the impact of a jump.
Summary: What You Need to Know
Aggressive 29″ hardtails can handle jumping but are not optimal for that task for the following reasons:
- Large wheels
- Large frames
- Heavy weight
- Long chainstays
- Squishy suspension
XC hardtails are harder to jump and may even break during jumps for the following reasons:
- Ancient geometry
- Non-reinforced head tube
- Weak wheels
- Entry-level forks designed for light XC terrain
In conclusion, if you want to try some basic jumps on a hardtail, you can do so. But if you desire to reach a higher level, a dirt jumper will be needed.