Technical Specifications
Type: Mechanical cable-operated linear-pull rim brake 
Construction: Forged aluminum
Lever Requirement: Linear-pull type
Weight: 185g
Country of Origin: Taiwan
MSRP: $39.99

The Avid SD 7 has been a very popular brake with mountain bike owners since its introduction in 2001.  As a manufacturer of bicycle brakes, Avid has always competed with market giant Shimano, and quickly established itself as a viable option for mountain bike brakes and accessories.  Now owned by SRAM, Avid has moved on to a successful line of disc brakes, while continuing to market the SD 7 and other linear-pull designs for cross-country (XC) mountain bikes.

Features
Available in front or rear brake models, the SD 7, like other linear-pull brakes, is mounted on a pair of brake bosses or studs attached to the bike frame, using extended twin cable-operated arms to increase leverage and stopping power.  The current SD 7 features improved Rim Wrangler 2 brake pads, which the company claims will provide increased stopping power and modulation.  The SD 7 also incorporates what Avid calls Force Vector Alignment (FVA), which is said to reduce frame and fork flexing at the brake bosses while improving braking efficiency.  What this actually means is that the brake pad post on the SD 7 is behind the brake arm, rather than in front of it, as on some (not all) other brakes.  When the pads are squeezed against the wheel rim, the leverage of the pad on the brake boss is shorter, reducing the amount of frame (fork) flex at the brake bosses.

Other features include no-tool replaceable cartridge brake pads, a built-in metal cable routing ferrule or  ‘noodle’, oversized return springs, pad clearance adjusters and a bead-blasted finish.  The SD 7 requires the use of brake levers designed for linear-pull brakes.

Installation
I installed my SD 7 rear brake on a hardtail mountain bike frame.  Mounting and adjusting it took only a few minutes, despite the fact that it had been some time since I had installed a rim brake.  The instructions are clear and easy to follow.  After mounting the brake on the brake bosses, the rear brake cable is run to both brake arms and pulled taut before securing it with the cable fixing bolt.  The Avid cable fixing bolt works in tandem with a metal spacer to hold the cable without pinching or flattening it, which could cause the cable to fray and break.  The brake pad is aligned to the rim sidewall by moving its bolt up or down in a slotted housing.  To adjust toe-in or toe-out of the brake pad, the brake pad bolt is fitted with convex/concave adjustment washers. 

To operate the SD 7, I used an inexpensive linear-pull four-finger-length lever along with standard 5mm brake cable and housing, all of which worked perfectly.  One nice feature is the amount of adjustability of the design.  The SD-7 uses a coil spring with a long arm held in tension against brake arm.  Pad clearance can be micro-adjusted by turning a Phillips-head screw after centering the brakes.  Alternately, one can pull or push the long spring arm tensioning the brake on one side to center the brake pads between the sides of the rim. 
Like other linear-pull brakes, the SD 7 may be disengaged to remove a wheel with its inflated tire without loosening the cable fixing bolt.  This is accomplished by squeezing the tops of the twin arms together while unhooking the cable ‘noodle’ from its hinged carrier.      

Rider Experience
Since 70-90% of all braking effort in an emergency stop on a bicycle is produced by the front brake, my SD 7 rear brake did not have a great deal of work to do.  However, along with a front disc brake, it did prove capable of stopping a motorized bicycle from speeds of 32 mph, all without grabbing, squealing, or excessive fade.  I set up the SD 7 with minimal rim clearance and cable slack, resulting in quick stops and a ‘tight’ one-finger brake effort, while still maintaining adequate brake modulation. 

Over four months of use on pavement and dirt trails, I have noticed little pad wear.  As expected, the brake cable needed to be re-tightened after a week of use because of cable stretch (common with cable-operated brakes).  Maintenance has been minimal, consisting mostly of occasional fine adjustments of brake pad clearance vs. the rim sidewall.  
 
Most of my riding takes place in dry southwestern desert, so I did not have an opportunity to evaluate braking performance in rainy weather or on muddy trails.  With its replaceable cartridge-type brake pads, the SD 7 can be upgraded with abrasive dual-compound or other pads that offer increased wet-weather performance.  For regular use on muddy or wet trails, disc brakes are a more suitable alternative.  But for general XC rides, Avid’s SD 7 should be more than adequate.  

Recommended: Yes