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TNN Booster Still Flexing


isitafox

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I've currently got a TNN booster/brake mount combo on the back of my Pure and yet the rear end still flexes like mad.

Has anyone got any suggestions on how to stop this or is it purely down to my ultra powerful brake setup? (Echo SL CNC lever body with 4 finger Magura lever blade)

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Hmm. It should be pretty stiff.

Some 'washered' clamps will help with the Trialtech rim though, unless you just grind an angle on the pads (or live with a slightly funny-feeling brake until they wear to match the angle of the rim).

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I've got these on an Echo Control frame and the brake is pretty stiff. The beauty of the TNN booster is you can just run an additional booster on top. Have you tried bleeding the brake? Very often flex comes from the frame, but if your brake has air trapped in it, you'll get the impression that the frame is flexing (which it always does to an extent) when actually most of the sponginess comes from the air.

Actually there was a time when Monty frames could have a v-brake booster installed on the underside of the seat stays. Pretty random bit of info, but a really neat idea. Used to run 3 brake booster in total on my old X-Lite.

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Does it make the brake feel stiffer/give better braking performance if you run the pads at the same angle as the rim?

I run echo clamps, no washers, and the pads have worm at the angle of the trial tech rim. Works fine but am I missing out on something better?

Yes.

It will work spot on now yeah, as the pad face is hitting the rim squarely.

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Can someone explain to me why CNC backings make the brake stiffer?

Is it because they don't move around as much in the slaves? Because if not I can't really get my head around how they help? Is it because the plastic backings compress more as they'll have air trapped inside them?

It's one of those things where I've always just generally accepted it but when I think about it i'm not sure why. My brain works by wanting to know why haha

Edited by dann2707
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Plastic backings flex, middle of the pad gets all the force, the two ends of the pad don't, so the force is compressing only a small amount of pad material.

Metal backings stiffer, the force is going into all of the pad material.

You can see it happening with a powerful brake setup and plastic backings.

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I've currently got a TNN booster/brake mount combo on the back of my Pure and yet the rear end still flexes like mad.

Has anyone got any suggestions on how to stop this or is it purely down to my ultra powerful brake setup? (Echo SL CNC lever body with 4 finger Magura lever blade)

Could you please measure how much you brake booster flexes under normal use? 1-2 mm of flex is normal unless your applying more braking force than required under normal riding conditions.

Here's a trick if you want less flex and more solid lever feel. Loosen off the lower bolt on one clamp which holds the booster. Now with needle nose pliers flex the booster outwards 1-1.5mm by squeezing the booster and the clamp. While booster is flexed outward tighten clamp.

What this does is preload the booster so once the brake is applied the bulk of the flex is already preloaded out of the booster. Having said this all boosters flex even ones which weigh twice as much as a TNN.

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  • 2 weeks later...

Its the pure frame. I have a 2012 Pure too. Its just the same. The most flexy rear end frame I've owned, even with a booster. What it does tell me though is taht ive got a good solid bleed on the rear to have no sponginess. Can see the frame start flexxing out the second the lever goes more solid.

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