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+--- Thread: Front wheel issue (/showthread.php?tid=67352)
Front wheel issue - Kentish - 18-02-14
Hello all, I noticed whilst I had my bike up on the paddock stands and spun the front wheel it only rotates about one turn? I stripped the calipers put in new seals cleaned all the pistons so they were like new. With the calipers off the wheel spins a lot more freely, the discs are not warped as I hooked up a new pair that I have on another wheel and it still done the same. Am I going mental or its this normal? I get about one whole revolution of the front wheel when I spin it.
Pads are pretty worn I guess. Help me!!
Re: Front wheel issue - fazersharp - 18-02-14
Normal as the pads do slightly touch
As I dont think they actually retract but just "stop pressing"
Re: Front wheel issue - Kentish - 18-02-14
I guess this is what causes the drag then?
Re: Front wheel issue - Buzz - 19-02-14
I've always been able to hear a slight hiss from the pads when I rotate both the back and front wheels. As long as the wheel isn't properly binding I don't count this as a problem.
Re: Front wheel issue - fazersharp - 19-02-14
(19-02-14, 09:59 AM)Buzz link Wrote: I've always been able to hear a slight hiss from the pads when I rotate both the back and front wheels. .Yep thats it- its a shhhhhhhh when you spin it
Re: Front wheel issue - cfoley - 19-02-14
I actually took my bike to get looked at because of the shhhhh. Turns out I had sintered break pads and they are supposed to touch the wheel slightly. Felt pretty embarrassed about that one. Should have asked on here first!
Re: Front wheel issue - Kentish - 20-02-14
Found the issue out. Someone had used the original back plates (shims) on the EBC pads that were in the calliper, these are only for original pads and not after market pads. Also took the shim off the rear pads which freed the rear wheel up big time. After market pads are made the same thickness as the original with the plate on. No need to put the backing plate on aftermarket pads as this pushes the pads closer to the disc and causes a tight wheel
Re: Front wheel issue - fazersharp - 20-02-14
That all sounds good
But I still dont get it, because the pistons go in depending on how thick your pads are. So thicker pads wont be pressing on the disk any more than thin ones would.
isnt it ??
Re: Front wheel issue - ChristoT - 20-02-14
(20-02-14, 06:59 PM)fazersharp link Wrote: That all sounds good
But I still dont get it, because the pistons go in depending on how thick your pads are. So thicker pads wont be pressing on the disk any more than thin ones would.
isnt it ??
The piston can only retract so far. And don't forget latent pressure in the system.
The disadvantage of hydraulic brakes is plain here: they don't actively disengage. So there's always going to be a certain amount of friction to overcome to disengage them, and then run the wheel past them. Cable operated brakes don't have this, as they spring back with the lever.
Re: Front wheel issue - fazersharp - 20-02-14
Quote:. And don't forget latent pressure in the system.Firstly I dont know about such things as latent
Quote:So you are saying that the pads are so thick that they are pressing on the caliper and not the piston when not under brake
The piston can only retract so far
Re: Front wheel issue - johna6968 - 20-02-14
Gettin a full 1 turn is pretty good and better than most iv come across tbh :thumbup
Re: Front wheel issue - Dead Eye - 20-02-14
(20-02-14, 08:36 PM)fazersharp link Wrote:Quote:So you are saying that the pads are so thick that they are pressing on the caliper and not the piston when not under brake
The piston can only retract so far
Not quite - the pads are always is constant contact with both the piston and disc (under normal circumstances / operation)
The pressure in the hydraulic lines can't be relieved sufficiently (due to the valve at the master cylinder I believe) to cause a gap to occur. However, despite being in contact, its only very slight when the brakes aren't applied but its still enough to stop the wheel from free-spinning
Re: Front wheel issue - Lez72 - 20-02-14
Whenever I put fresh pads in a set of bike calipers I always reuse the backing plate if its still present and have never had a problem before. I changed the pads in my boxeye calipers last year for 'Galfers' without any issue ??
Confused
Re: Front wheel issue - red98 - 20-02-14
Rotation and vibration of the wheel helps to retract the piston, disc brakes are designed to rub all the time.christo is right they are un efficent in that respect........run the bike around for a few miles without using the front brake, pull up using the rear brake only....then try spinning the front wheel, it will be easier to spin.....go on try it
Re: Front wheel issue - Kentish - 21-02-14
(20-02-14, 06:59 PM)fazersharp link Wrote: That all sounds good
But I still dont get it, because the pistons go in depending on how thick your pads are. So thicker pads wont be pressing on the disk any more than thin ones would.
isnt it ??
Pistons will only retract so far due to pressure in the system. they don't go all the way back. So if you were to put pads in and say slide a 1mm or 2mm thin piece of metal behind each pad it would push the pads closer to the disc and cause the wheel to bind. Remove the metal and you will have extra space hence the wheel being more free.