Recumbent trike hydraulic brake issue

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SmilerGB
Posts: 59
Joined: 16 Dec 2017, 8:41pm

Recumbent trike hydraulic brake issue

Postby SmilerGB » 12 Jul 2019, 7:52am

I’ve got a ice trike sprint x, with tektro Volans hydraulic brakes. I seem to get a build up of air on RH side it’s been bled multiple times & within a day the problem reoccurs.

Has anyone else issues like this & resolved or know of any replacement callipers which are mirror images of each other that I can use ?

Any help would be gratefully appreciated
The bicycle is a simple solution to some of the world's most complicated problems.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Recumbent trike hydraulic brake issue

Postby Brucey » 12 Jul 2019, 8:52am

how do you know that the air is in the RH caliper? FWIW two-caliper hydraulic circuits can be a pain to bleed, but persistently recurring problems are almost invariably caused by air in the MC reservoir migrating into the pressure part of the brake system (otherwise you have to imagine that air is somehow able to get in at the calipers, without fluid leaking out; this doesn't make sense).

Problems at the MC end are aided and abetted in many recumbents by the MC positioning.

A good test is to temporarily reposition the MC so that the compensation port (the port that connects the MC to the reservoir) is vertical. If the brake then firms up by itself within a few pulls of the lever then you can be sure that there is air in the MC reservoir and that it is migrating into the rest of the circuit to cause the sponginess. If the hose, when installed, undulates (i.e. goes up and down) then it will tend to accumulate air in the high spots, rather than self-bleed.

It is easy enough to bleed a hydraulic system on an upright bike, leave some air in the MC reservoir and think that you have done a super job because the brakes feel firm. However this is 'necessary but not sufficient'; if there is air in MC reservoir then the brakes will stop working if the bike is turned upside down and if the same standard of bleed is used on a recumbent then the brakes will often be persistently troublesome in normal use because of the orientation of the MC.

cheers
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Tigerbiten
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Re: Recumbent trike hydraulic brake issue

Postby Tigerbiten » 12 Jul 2019, 8:53am

At a guess it's the brake lever piston seal that gone, that's where mine used to fail.
Check for signs of an oil leak around the brake lever piston seal.
If it has then you need to replace the lever not the callipers.

On a recumbent trike the levers point upwards and the top of the piston seal is in a nice hollow in the brake body.
Any dust/grit that falls in there plus a little rain water makes a nice grinding paste which can cause the seal to fail.
I ended up getting a replacement lever from Tektro and then making a cover for the brake lever/body so nothing can get into that space.
Cut a small neoprene glove so the little finger can be zip tied around the lever and part of the hand gets zip tied around the brake body to form the dust cover.
I went from roughly 3 dead seals in three years to the last one that has lasted over 5 years now.
I think it's a little known downside of hydraulic brakes on a bent trike.

Luck ........... :D

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Recumbent trike hydraulic brake issue

Postby Brucey » 12 Jul 2019, 9:36am

its worth mentioning that some tektro MCs use the 'bladder reservoir' system. If this system runs low on fluid or the bladder goes hard, you can get negative pressure in the brake system on the return stroke and the first place the air is drawn in is past a slightly worn MC seal. Obviously once air is in the MC bore if the orientation is unfavourable it tends to stay there.

Hope recommend a silicone spray lube for their pistons; I don't see why it shouldn't be used on Tektro MC seals too.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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SmilerGB
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Joined: 16 Dec 2017, 8:41pm

Recumbent trike hydraulic brake issue

Postby SmilerGB » 12 Jul 2019, 10:08am

Thanks all for you responses, will investigate further when I’m back off nights.
The bicycle is a simple solution to some of the world's most complicated problems.

Brucey
Posts: 35887
Joined: 4 Jan 2012, 6:25pm

Re: Recumbent trike hydraulic brake issue

Postby Brucey » 12 Jul 2019, 11:17am

if your brakes look like this

Image

then the MC reservoir has a diaphragm inside it. Not sure what (if any ) changes they make when two calipers are used from one MC.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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Tigerbiten
Posts: 1920
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Re: Recumbent trike hydraulic brake issue

Postby Tigerbiten » 12 Jul 2019, 3:47pm

SmilerGB wrote:know of any replacement callipers which are mirror images of each other that I can use ?

Any help would be gratefully appreciated

The only callipers that are a mirror image of each other I know of are the Tektro Auriga Twin as they are designed to fit tadpole trikes.
I'm not sure how dead my dead set is.
I know the main piston seal is blown, apart from that ?? as I last used then around 5 years ago.

Luck ........... :D

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SmilerGB
Posts: 59
Joined: 16 Dec 2017, 8:41pm

Re: Recumbent trike hydraulic brake issue

Postby SmilerGB » 12 Jul 2019, 4:10pm

Thanks for the alternative suggestion on callipers was struggling to find any

I’ve got enough food for thought, to investigate & throw at ice trike support.

Thank you everyone for your time & support
The bicycle is a simple solution to some of the world's most complicated problems.