Created article FAQ: The engine sounds different when I hold the rear brake
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FAQ: Why does the engine sound different with the brakes on? |
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Petty Tyrant
![]() ![]() GTS250 GTS300 MP3 500
Joined: 11 Oct 2005
Posts: 29677 Location: Bay Area, California |
![]() Created article FAQ: The engine sounds different when I hold the rear brake
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Petty Tyrant
![]() ![]() GTS250 GTS300 MP3 500
Joined: 11 Oct 2005
Posts: 29677 Location: Bay Area, California |
![]() A different Theroy
I would like to offer a different Theory. The engine is isolated from the frame by rubber bushings whether the rear brake is applied or not. The axle is under load from the weight of the scooter and the rider. The force of the brake pad transferred to the rear axle is minimal when the scooter is setting still.
So IMHO the clamping of the brake pad to the rear disc does little to nothing to change the sound and vibration. What does go from an isolated to non isolated state is the hydraulic fluid and line activating the rear brake. Unpressurized the rubber hose and fluid dampen sound and vibration transferred from engine to frame. Pressurized, the fluid and the line become almost solid ending the damping and create a conduit for the sound and vibration to be transferred from engine to the frame. If the rear brake was activated by a cable, the change in sound and vibration would be less because of the cable being made of many stands of wire and having more flexibility than the hydraulic line and fluid under pressure. |
Petty Tyrant
![]() ![]() GTS250 GTS300 MP3 500
Joined: 11 Oct 2005
Posts: 29677 Location: Bay Area, California |
![]() I hadn't heard that theory before, but it's a good one. I never really thought of the hydraulic line becoming like a solid, but in a sense it really does.
I don't think there's anything at all wrong with adding this theory to the existing article. It's at least as good as the one that's already there. ![]() |
![]() Re: A different Theroy
wetspeed wrote: Pressurized, the fluid and the line become almost solid ending the damping and create a conduit for the sound and vibration to be transferred from engine to the frame. If the rear brake was activated by a cable, the change in sound and vibration would be less because of the cable being made of many stands of wire and having more flexibility than the hydraulic line and fluid under pressure. |
Ossessionato
![]() ![]() 2016 Vespa GTS300ie abs/asr/ess Settantesimo '70'
Joined: 11 Jun 2011
Posts: 3160 Location: East Anglia, a dryer region of the UK than Israel |
![]() Also, don't forget the brake applies the stop light. This high wattage bulb loads the generator at idle and increases the load (albeit lightly) on the engine, and possibly further changing the engine note. This will be even more noticeable when the battery is not fully charged. Just another thought! It's probably all of the things mentioned in this thread above put together.
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![]() Stromrider wrote: Also, don't forget the brake applies the stop light. This high wattage bulb loads the generator at idle and increases the load (albeit lightly) on the engine, and possibly further changing the engine note. This will be even more noticeable when the battery is not fully charged. Just another thought! It's probably all of the things mentioned in this thread above put together. |
Ossessionato
![]() ![]() BV350, Primavera 150, Yamaha Zuma 125
Joined: 06 Jun 2013
Posts: 3231 Location: The Twin Cities of Minneapolis/Saint Paul, Minnesota |
![]() Theflaming wrote: Stromrider wrote: Also, don't forget the brake applies the stop light. This high wattage bulb loads the generator at idle and increases the load (albeit lightly) on the engine, and possibly further changing the engine note. This will be even more noticeable when the battery is not fully charged. Just another thought! It's probably all of the things mentioned in this thread above put together. |
Moderaptor
![]() ![]() The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
Joined: 26 Aug 2007
Posts: 39245 Location: Pleasant Hill, CA |
![]() JKJ-FZ6 wrote: Theflaming wrote: Stromrider wrote: Also, don't forget the brake applies the stop light. This high wattage bulb loads the generator at idle and increases the load (albeit lightly) on the engine, and possibly further changing the engine note. This will be even more noticeable when the battery is not fully charged. Just another thought! It's probably all of the things mentioned in this thread above put together. A 20W bulb sucks up a whopping 0.025hp. Arguably this might make a noticeable difference if the charging system is weak and the battery is shagged, but I doubt it. |
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