Brake Boosters - do they ACTUALLY work?

[Old School MTN BKR]

They work on very flexy forks, like a Rock Shox Mag 21.

They do work on Maguras too.

 

[legrandefromage]

For and aft is the important bit as the forward movement actually pulls the rear stays back together as braking force is applied.

The brace doesnt need to stop the frame flexing, only the twisting of stanchions/ fork legs - you're still thinking about what you bike does when standing still - whilst moving, its a whole different kettle of sprouts

Loosen you pads a tiny bit, whilst stationary, apply brakes and rock the bike backwards/ forwards and watch your stays/ pads - fit a booster and do the same...

Then tighten you pads!!!

 

[legrandefromage]

just tried this on my Pubjumper - cant get ANYTHING to move as the frame dont flex....

duh..

 

[scant]

if theres ever an advert for a brake booster it would be a magura brake on a clark kent titanium frame. the amount of flex has to be seen to believed

 

[tintin40]

On my bikes. happy with my braking . If i was to buy some 'boosters' for Maguras then it would be sexy carbon But at £15 each. I'll have to have more money in the bank than i do now :cry:

 

[dookie]

For and aft is the important bit as the forward movement actually pulls the rear stays back together as braking force is applied.

i'm having a bit of a problem understanding how a perpendicular force (from pad friction on rotating rim) could cause any inward movement (stays toward rim). torsion (with the brake boss as the axis), sure, but as the trailing edge of the pads are twisted into the rim, the leading edge twists away. and even if this were true, inward force lost to outward flex does nothing to help 'pull the stays together'.

all of which leads me to say, yes, boosters do make a difference if your frame flexes at all (even while stationary). the two examples i have in hand are a steel paramount (w/somewhat flexy rear stays and a beefy unicrown up front), and a ti kona (much more solid rear, disc up front).

i see flex in two directions, both of which the boosters virtually eliminate. first, the stays (or fork blades) bow outward. second, the brake bosses act as a lever and twist the stays along their length (with the stay as the axis).

i run maguras on the paramount and absolutely, positively recommend boosters with these rim crushers. i happened to have a v-booster in hand, so i run it on the kona rear as well. in both cases, subjectively speaking, braking is much improved...more of the lever force is ultimately applied to the rim (more power), and subtle changes in lever pressure are reflected at the pads and not the frame (better modulation).

just my $0.02.

 

[tintin40]

even with out 'boosters' i can lock the rear wheel up with one finger on a steep decent with Maguras. So why fit a booster? Any more is not needed. May be thats why they are rim crushers

 

[legrandefromage]

For and aft is the important bit as the forward movement actually pulls the rear stays back together as braking force is applied.

i'm having a bit of a problem understanding how a perpendicular force (from pad friction on rotating rim) could cause any inward movement (stays toward rim). torsion (with the brake boss as the axis), sure, but as the trailing edge of the pads are twisted into the rim, the leading edge twists away. and even if this were true, inward force lost to outward flex does nothing to help 'pull the stays together'.

You're thinking two dimentionally, pulling the brake lever as you ride along applies a multiple of forces on the frame/ cable/ lever/rim/ pad

put a tube between to rollers - pull the tube backwards & forwards - the rollers move - the rollers = action on your stays/ stanchions as you apply the brake to -

the tube - ie - your wheel

 

[legrandefromage]

even with out 'boosters' i can lock the rear wheel up with one finger on a steep decent with Maguras. So why fit a booster? Any more is not needed. May be thats why they are rim crushers

really really does depend on the build of the frame. And maguras have a 'linear' action which is different.

Boosters are best on the front - we're discussing the effects of yanking on the stoppers and the difference between stopping in front of a policeman or, as my case running over his foot! (mag 21's with NO booster).

 

[legrandefromage]

dont get competitive here!

A brake booster works, the physics of it says it does - wether you actually need one is another matter and depends entirely on your frame build and forks - I'd only use one on some very early designs of suspention fork when using cantelevers. Most rigid forks dont need one, V-brakes dont really need one...

now you've made me mention 'physics' and made my brain hurt. :twisted: