Tony Kart Venox 2005 Brakes

Hi guys,

This is an old tony kart venox 2005 we’ve had sitting in the shed and trying to sort out.

The main problem at the moment is the brakes. The pads are only travelling into the disc right at the end of the brake pedal travel and even then are hardly making contact.

I’ve already bled the brakes with a tower but it doesn’t seem to have done anything.

Any help appreciated.

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Sounds like the pistons are binding. Take the caliper off and pads, extend the pistons by pressing the pedal and clean the exposed piston, put some brake fluid on it and push it back in, do this a few times it might just free it up.

Failing that take it apart and clean any contamination or corrosion from pistons and housing bores, careful with the housing if there are corrosion pits.

If you have to hone the bore a bit to clean it up, clean it very thoroughly afterwards.

I think that caliper does not self adjust for travel. You may have to turn in the bolts with the springs to shorten the gap from the pad face to the rotor. Try adjusting the resting point of the pads, then give the pedal a few pumps and see if the point of contact within the range of pedal travel improves. Check the reservoir level after to make sure it is still full.

Tip: First back the bolts out until the pad backing plate contacts the caliper body, then turn them in equally. Resting point should be 1 mm or less from pad face to rotor.

1 Like

You’re right GregF that caliper is not self adjusting for pad to disc clearance.
Adjustment is by shims between the piston and the pad backing plate.
Looks to be one in there ,may be room for another on the other side.
@ohasha. Is the bottom pic taken with the pedal pressed? The left m/ cyl looks as if its piston is halfway down the bore.
Which one feeds the front brakes? Do they work at all?
I would disconnect all the linkage and pull the boots off the 2 m/cyls and check that both m/cyl pistons are returning fully against the circlips.
There is an advised technique for bleeding these systems. Can’t produce a link but if you google ’ bleeding Tony kart brakes’ and look for the contribution from ‘Jan/Race instructor’ from Karting1. co .uk and follow that it may help.

So just out of curiosity, what are those bolts with springs for? I can only assume the springs prevent the bolts from turning from vibrations, but what do they push against if not the back of the pads? Would it make sense to upgrade to the newer style master cylinder that self adjusts and eliminate the need for shims? The self adjusting one is a better design IMHO.

The bolts with springs hold the pads on the caliper and the springs retract the pads.

Yes the two bolts screw into tapped holes in the steel pad backing plate, usually with a tubular sleeve .
The spring sits between the bolt head and the caliper body and pulls the pad back against the body or any adjustment shims.
I prefer the spring return caliper to the self adjuster.
In my experience the self adjuster suffers from poor pad retraction and with no need for adjustment, the pistons end up too far out of their bores leading to worn calipers but ’ each to his own’

GregW & John,

Makes sense the springs act a return mechanism. I have been using the BS6 rear Caliper with the One-Piece Master and never had an issue with the pads not backing off the rotor. Let off the pedal and the axle spins free. Other than replace pads, all I have ever had to do was bleed the system every now and again. For peace of mind I did replace the caliper piston seals a few months ago, but that was because I wanted to take the caliper apart for a good cleaning. Did not make sense to reuse the old seals as it was already apart.

Anyway, @ohasha, I hope we were able to help you out. Let us know how it goes.

Cheers for the input guys, i’ve taken apart and cleaned all 3 calipers so i’ll bleed it in the weekend and see how it goes

Further to this does anybody know if the brake system on tony karts Of this age take dot 5 or dot 4 fluid? I believe it’s a BS2 system

The BS2 uses dot 4, later models changed to dot 5