Zero Gravity Gravitas SL Brakeset
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Tested March 10, 2013
Zero Gravity Gravitas SL Brakeset
I first became aware of Zero Gravity brakes in 2004 when Iban Mayo used them at the Tour de France on the way to finishing in third place. In 2005, Francis, the founder off MTBR.com & Roadbikereview.com, got his hands on a set of the original OG-05 Ti calipers and wrote this review. After reading his review and seeing the brakes on Francis' bike, I ordered a pair immediately. They were incredibly light while also offering excellent braking. A few years later I also purchased the slightly heavier but stiffer Zero Gravity GSL's (230 grams) for another bike.
When the Gravitas came out in 2009, I was awestruck by the all carbon construction, weight, and $875 price. I did toy with the idea of buying these brakes but the price was just too steep. Luckily, I held out, which was a good thing because Zero Gravity has recently offered refurbished Gravitas brakes for $399. I couldn't resist at that price.
You will need seven tools to install these brakes (in addition to Campy 2000+ brake pads; brake pads are not supplied):
- 5mm and 3mm allen wrench. The 5mm is for the brake bolt, the 3mm is for the bolt that clamps the cable.
- 13mm or 1/2 inch cone wrench to hold the nut behind the brake. You also use this wrench to center the calipers.
- T-20 and T-30 Torx bits. The T-20 is for the brake pads. The T-30 is to adjust the tension of the brake calipers. If the brake is "sticky" and doesn't return fully, loosen the brake bolt then hold the nut with the cone wrench and rotate the front-facing Torx bolt counter-clockwise with the T-30 bit.
- Electrician's tape. Place the tape around the nut to prevent scratches.
- Cable cutters for housing and cable.
There are a few tricks to the install. First, do not compress the brake by pushing in the brake by the brake pads with your fingers. This can weaken the return spring. Secondly, make sure to trim the brake cable so when inserted into the barke arm it doesn't push the brake to one side. Additionally, make sure it isn't too short which would make the brake pivot to the other side.
The brakes also come with 3 sets of washers for the brake pads. There is a washer with a flat side and concave on the other. The washer with the flat side needs to have the flat side flush with the brake; the concave side mates to the brake pad holder. There are 2 additional spacers that are bent on both sides; one thick and one thin. Use all three if your rim is a narrow 19mm wide. Remove the two bent spacers if you are running super wide Zipp & Hed wheels. For rims that are in between, experiment to see what fits best. I tried using the rear brakes with just the flat/concave washer on my Easton EA90 SLX rims and braking performance wasn't great. Adding the thick spacer improved braking dramatically.
Another neat feature is the routing of the cable through the cinching bolt. You thread the cable through the brake arm and then behind the cinch bolt through a pre-drilled hole. This is a nice feature that guarantees alignment while also making it easier to secure.
Cable threading to cinch bolt
Lastly, the brakes are designed to have the most leverage with very little pull on the levers. Ted advises just 1mm of clearance between the shoes and the rim. So make sure your cable is tight and raise the cam arm while adjusting. You can pinch the brake pads against the rims while doing this without potentiall weakening the return spring.
Rating: 4.5 stars; the refurbished brakes are a good value for a superlight brake that provides excellent stopping power. You just need to be patient with the install.
Rear cable routing