Mountain Gear

A Good Scrub Saves Rotor Weight

Shiny and new, Scrub rotors have a machined brake surface for smooth performance. Photo by Zack Vestal If you are a weight weenie (and there's nothing to be ashamed of if you are), finding new ways to save weight on your mountain bike is getting harder and harder. Most components seem to have reached their limit in the three-way, strength-versus-stiffness-versus-weight tug-of-war. Chris LaCasce and Scrub Components want to change that, with Scrub aluminum brake rotors. Fully half the weight of a traditional 6-bolt stainless steel rotor, a 160mm Scrub rotor weighs less than 60 grams (56 grams claimed, our test rotors each weighed 58gm). A comparable stainless steel rotor weighed 135 grams, meaning that by swapping rotors alone, you could shed around 150 grams from your bike in one fell swoop. That's fully a third of a pound.

Shiny and new, Scrub rotors have a machined brake surface for smooth performance. Photo by Zack Vestal
Shiny and new, Scrub rotors have a machined brake surface for smooth performance. Photo by Zack Vestal

If you are a weight weenie (and there’s nothing to be ashamed of if you are), finding new ways to save weight on your mountain bike is getting harder and harder. Most components seem to have reached their limit in the three-way, strength-versus-stiffness-versus-weight tug-of-war.

Chris LaCasce and Scrub Components want to change that, with Scrub aluminum brake rotors. Fully half the weight of a traditional 6-bolt stainless steel rotor, a 160mm Scrub rotor weighs less than 60 grams (56 grams claimed, our test rotors each weighed 58gm). A comparable stainless steel rotor weighed 135 grams, meaning that by swapping rotors alone, you could shed around 150 grams from your bike in one fell swoop. That’s fully a third of a pound.

But does that kind of weight savings come at a cost? Financially, yes: A single 160mm Scrub rotor will lighten your wallet by $145. What about performance? Read on. We spent more than 100 miles on a pair of Scrub rotors to find out.

Who is Scrub Components?

In business for just more than a year, Scrub Components is based in Park City, Utah and is operated by Chris LaCasce. LaCasce is an engineer by education and has been an avid cyclist for the last 15 years.

“I was always tinkering and throwing ideas around,” LaCasce said.

After completing his degree, he decided to have a go at the cycling market with a product that few have attempted.

“That’s what pushed us; if you look at bikes now, there are not many places left where you can make big improvements,” LaCasce said.

LaCasce recognized that steel brake rotors are among the heaviest single parts remaining on a mountain bike and had great potential to be made lighter. He says he spent about four years working on materials and designs before introducing Scrub rotors last year.

While making brake rotors from aluminum would seem to be an easy task, it’s far from simple. Indeed, Stan’s NoTubes formerly manufactured aluminum brake rotors, but gave up last summer due to high costs and questionable returns.

SCRUB DISC BRAKE ROTORS

$145 per 160mm rotor
The Scoop: A featherweight metal matrix brake rotor, made in the USA
Pros: Quick way to shave significant weight
Cons: Somewhat diminished brake power, must use specific brake pads for best results
More info: www.scrubcomponents.com

LaCasce emphasizes that his product is different in key ways. It has already been validated by race successes from sponsored riders on the MonaVie-Cannondale team, plus endurance riders Evan Plews, Jake Kirkpatrick, Bryan Fawley, Krista Park, and Kathy Sherwin.

The Wrenching

Scrub rotors are cut one at a time from a sheet of metal matrix composite alloy. The metal matrix composite is essentially like an aluminum alloy with other materials mixed in to form a matrix that’s stronger than the metal alone. Years ago, Specialized Bicycles used a material of this type in their high-end alloy hardtail bikes. Currently, the material can be found in motorcycles and snowmobiles, but is expensive to produce and manufactured only in a few locations. Scrub’s metal matrix composite reportedly has great heat transfer and stiffness properties compared to standard aluminum alloys.

After being cut into rotors, the material is coated and then the brake friction surface is machined to be perfectly flat and smooth at the edges. Several colors are available including grey, blue, limited-edition white and MonaVie-Cannondale green.

Scrub Components is very specific about the fact that organic/resin compound brake pads must be used. Scrub specifies that they’ve found Kool Stop brake pads to be optimal for their rotors, but acknowledges other resin pads will work. On the other hand, metal brake pads will accelerate wear on the rotors and can also cause overheating in extreme situations.

LaCasce said that while he’s working on a proprietary pad compound to be paired specifically with his rotors, Kool Stop pads provide the quietest, most consistent braking of the numerous pad compounds he’s tried. Key to braking performance is the buildup of a transfer layer of pad material to the rotor friction surface. Scrub rotors don’t rely on anodizing or a coating to maintain the friction surface.

Swapping to a set of Scrub rotors is as easy as bolting them on, finding Kool Stop disc pads to fit your brakeset and swapping them in place for your stock pads. Scrub sells them on their Web site. I was also able to eventually find them at several Internet bike stores.

In addition to swapping rotors and pads, Scrub’s instructions include a very specific break-in procedure, essentially burning in the rotors such that a layer of pad material transfers to the rotor surface. Once there’s pad material burned on to the friction surface of the rotor, braking is much smoother, quieter and more consistent. Braking hard to a full stop 25 times in a row, from a moderate to high speed, creates enough heat to cause the pad transfer layer to build on the rotor and you are ready to go.

The Riding

I used Scrub rotors on my Trek Fuel EX 9.9 for the Intermontane Challenge stage race, and also on my Gary Fisher Superfly 29er for some long rides around Colorado. I used Avid Juicy Ultimate brakes on both bikes with 160mm rotors and Kool Stop pads.

After completing the burn-in procedure, braking was smooth and consistent. I never had opportunity to ride in wet or muddy conditions, but in dry weather braking performance was good. However, they are not as powerful as I’ve come to enjoy from metal pads on stainless steel rotors. Resin pads pinching Scrub rotors don’t bite as quickly and firmly as I like.

That being said, I freely confess to being a “roadie” type mountain biker with limited confidence in extreme descending situations. As such, I probably ask more from my brakes than most. And in more average terrain braking was perfectly fine. My problems were limited to sketchy fall-line descents and sharp late-braking situations.

I would like to try the 180mm Scrub rotor up front. And I have a hard time envisioning anyone but the most hardcore racer using the available 140mm rear rotor.

Racers will have no problems with these rotors. They are light and held up just fine for my test period. After some adjustment to braking points and modulation, I could descend as fast as I cared to.

Bottom line: if you are willing to give up a chunk of change and a bit of the normal pinch-power from your brakes, Scrub rotors will save you a relatively huge amount of poundage from your bike.