100 MPG Madness, Project Aprilia SR50- Brakes, Bling and Suspension
By Mike Kojima
In the last edition of Project Aprillia SR50, we had upgraded our little 50cc high tech scooter from an in-town runabout to a serious 60 mph capable commuter capable of handling rides on the fastest crowded main streets and parkways without cowering in the slow lane.
|The stock hydraulic disc brakes were good, we wanted to make them awesome to match the rest of our super scooter's capability. Just the thing to smoke Vespa scooter snob fags that seem to populate our area.|
Now to build a balanced bike, since we upped the speed and acceleration, it was time to address the brakes and suspension. The SR50 is blessed with some excellent Grimeca hydraulic disc brakes from the factory but we set out to improve them.
|The full floating Stage 6 rotor dwarfs the stock part on the right. It has through vents as well as scallops to evacuate vaporized pad material helping improve pad bite. The bigger rotor gives the caliper more leverage and more power.|
We had High Gain Tuning special order us a front big brake upgrade from Stage 6. Stage 6 is a European scooter tuning company that sells some pretty serious stuff. The Big brake kit features a large floating front rotor. The rotors is about as big of a part that can be fit inside the front wheel. The kit includes a bracket that relocates the caliper higher to accommodate the bigger rotor. The Stage 6 rotor is floated on an aluminum mounting hat using special shoulder bolts which allows the rotors to slightly move on the hat even when the bolt is fully tight. Floating the rotor is a racing feature common for race cars and bikes that allows the rotor to freely expand minimizing the thermal stress and coning that can happen in one piece and solidly bolted rotors.
|Wow, this deserves a prize just for the improvement in looks alone! You can see the CNC machined bracket that spaces the caliper out so the bigger rotor can be used. Yes the EVO in the background has 14″ 6 piston Brembo monoblocks.|
The difference in thermal expansion from the higher mass hub side to the backside on a one piece rotor can cause the rotor to assume a cone shape at high temperatures or warp more easily. This can cause a mushy lever. Floating the rotors can also work to minimize piston knockback. where a warping rotor pushes the brake piston back into the caliper also causing a long lever.
|Even though the brakes are way better, the kit still scores big in the looks department. The carbon fiber fender is made by PM Tuning in the UK. Look them up on google if you want to get one.|
In the rear of our bike, we installed a Galfer wave style rear rotor we got from Aprillia performance dealer AF1. A wave rotor has a scalloped periphery which helps evacuate vaporized pad material and water allowing the brakes to have better high temperature and wet performance. Evacuating the braking surface allows the brake pads to have more bite.
|The rear Galfer rotor has a wave scalloping on the outside and some vent slots. It is the stock diameter but on a bike 80% of your stopping is done by the front wheel.|
With our upgraded brakes, we immediately noticed a huge difference. The bigger rotor not only works better at high temperatures but the larger diameter gives the caliper a bigger moment arm so the applied stopping torque is multiplied. The front brake feels powerful now, like a big bike and our scooter can do stoppies. Two finger on the lever stopping is not an issue, just like the big Brembo brakes on our Ducati Hypermotard. Our rear brake feel is improved as well and the squeal that the stock drilled rotors had is now gone. The rear pads definitely have more bite and better modulation.
|The rear brake is pretty hidden on the SR50 but it looks cool. Helps lever feel a little as well.|