Why Do Downhill Bikes Have Short Reach? (fast answer)

Condensed Answer: Downhill bikes have a shorter reach than enduro MTBs to keep the bike nimble despite its long wheelbase and chainstays.

If downhill bikes had the same reach as other MTBs, the bikes would become too long.

Also, downhill bikes are not used uphill and don’t have to provide maximum comfort when climbing.

Definitions

Reach. The term reach refers to the horizontal distance from the center of the bottom bracket to the middle of the head tube. (image above).

The reach has a direct impact on how big a frame feels. Two frames can be of the same size, but the one with the longer reach would create the feeling of a larger bicycle.

The Geometry of A Downhill Bike

The geometry of a downhill bike has the following characteristics:

1. Long Chainstays

The chainstays are the two rear tubes the closest to the chain (hence the name). The length of the chainstays is a very important measurement as it has a profound effect on how the bike behaves.

Downhill bikes have chainstays notably longer than those found on XC and enduro bikes. The average chainstay length of a downhill bike is about 445mm whereas that of XC and enduro models is about 430-435mm.

Downhill bikes have longer chainstays to increase the bike’s length (wheelbase) and therefore stability while simultaneously reducing the chance of “looping out” (the bike sliding in front of the rider).

Longer chainstays, however, make the bike less nimble and increase the effort needed to lift the front wheel for the performance of tricks such as bunny hops and manuals.

The table below compares the chainstay length of popular downhill, enduro and XC bikes.

DownhillChainstay LengthEnduroChainstay LengthXCChainstay Length

Mondraker Summum450mmCannondale Jekyll 1435mmNorco Revolver FS 2430mm
YT Industries Tues 29440mmCanyon Torque CF 8428mmSage Optimator425mm
Commencal Supreme DH439mmGT Force Carbon PRO LE434mmTrek Supercaliber 9.7430mm
Specialized Demo438-443mmNukeproof Giga 290 Carbon Factory445mmMondraker Chrono Carbon430mm
Santa Cruz V10 MX435-445mmOrbea Rallon M-Team440mmScott Spark RC435mm
Canyon Sender 6 430-446mmPivot Firebird Pro XT/XTR – Air431mmSanta Cruz Tallboy436mm
Nukeproof Dissent 920 Comp445-455mmRocky Mountain Altitude C90 Rally Edition425mmCannondale Scalpel Carbon SE436mm
Trek Sessions 29 9.9452mmSanta Cruz Bronson CC X01 AXS438mmSpecialized Epic EVO438mm

Average:441-446mmAverage:434.5mmAverage:432.5mm

2. Slack Head Tube Angle

The head tube angle is the angle formed by the head tube and the ground. Since downhill bikes are built for overcoming obstacles during a descent, they have a slack head tube angle.

Or in simpler words, the front wheel is further in front of the rider. As a result, the wheel has an easier time overcoming irregularities. There’s also a reduced chance to go over the handlebars since less of the rider’s weight is on the front wheel.

Out of all MTBs, downhill bikes have the slackest head tube angles ranging between 63 and 65 degrees.

Part of the reason for the extra slack HTA angles on downhill bikes is the dual-crown fork which is longer and therefore taller than standard single-crown forks.


The table below compares the head tube angles (HTA) of downhill, enduro and XC bikes:

DownhillHTAEnduroHTAXCHTA
Mondraker Summum63.5°Cannondale Jekyll 164°Norco Revolver FS 267.4°
YT Industries Tues 2963.5°Canyon Torque CF 863.5°Sage Optimator69.5°
Commencal Supreme DH63°GT Force Carbon PRO LE63.5°Trek Supercaliber 9.769°
Specialized Demo62.7°Nukeproof Giga 290 Carbon Factory63.5°Mondraker Chrono Carbon70°
Santa Cruz V10 MX64°Orbea Rallon M-Team64°Scott Spark RC67.2°
Canyon Sender 6 63°Pivot Firebird Pro XT/XTR – Air64°Santa Cruz Tallboy65.7°
Nukeproof Dissent 920 Comp63°Rocky Mountain Altitude C90 Rally Edition65.5°Cannondale Scalpel Carbon SE67°
Santa Cruz Bronson CC X01 AXS64.5°Specialized Epic EVO66.5°
Average:63°Average:64°Average:67.8°

Conclusion:

The average head tube angle of downhill bikes is the slackest, but that of enduro bikes is very close behind. Unsurprisingly, XC bikes have a significantly steeper head tube angle facilitating climbing and the assumption of a more aerodynamic stance when pedaling.

Comparing The Reach Of Downhill, Enduro and XC Bikes

The table below compares the reach of popular downhill, enduro and XC bikes:

DownhillReachEnduroReachXCReach
Mondraker Summum450 mmCannondale Jekyll 1450mmNorco Revolver FS 2448mm
YT Industries Tues 29429 mmCanyon Torque CF 8465mmSage Optimator421mm
Commencal Supreme DH445mmGT Force Carbon PRO LE455mmTrek Supercaliber 9.7440mm
Specialized Demo446mmNukeproof Giga 290 Carbon Factory455mmMondraker Chrono Carbon426mm
Santa Cruz V10 MX402.5mmOrbea Rallon M-Team460mmScott Spark RC441mm
Canyon Sender 6 440mmPivot Firebird Pro XT/XTR – Air468mmSanta Cruz Tallboy450mm
Nukeproof Dissent 920 Comp460mmRocky Mountain Altitude C90 Rally Edition449mmCannondale Scalpel Carbon SE430mm
Trek Sessions 29 9.9461mmSanta Cruz Bronson CC X01 AXS455mmSpecialized Epic EVO436mm
Average:441.6mmAverage:457.1mmAverage:436.5mm

Note: The reach depends on the frame size. In most cases, the numbers in the table are for medium frames.

The data reveals that on average downhill bikes have a 16mm shorter reach than enduro bikes. Meanwhile, XC bikes seem to have the shortest reach for that particular frame size.

The Need For Short Reach

The slack head tube angle and the long chainstays make downhill bikes longer than other MTBs. That coupled with the fact that downhill bikes are not meant to be climbers, is a strong incentive to keep reach shorter and preserve some of the bike’s liveliness.

The Relationship Between Reach and Height

The taller the rider, the more reach is needed for assuming a comfortable position. For example, 415mm of reach would be too little for someone who is 6’2″ or taller. The downside of riding a frame with an extra short reach is the upright position and the feeling of being restrained.

That said, sometimes even tall people purposefully choose smaller bikes for the ability to throw them around with greater ease.

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