How Much Freewheel Spin

[AlanD]

Hi Hubbers,

 

Last weekend I changed the SRAM rotors (180 front and 170 rear) for shimano Ice Tech rotors (both 180mm) that were on the 26er as they were in great condition and not used for that long and look the business and didn't think of any compatibility issues as it's really just swopping the rotors. The brakes are the AVID trail 9 brakes.

 

The front fitted perfectly with no adjustments needed and aligned the caliper. The front wheel spins real nice and eventually comes to a slow stop.

 

Back wheel was a lot more fiddly as the rotor seems a bit more snug in the caliper and didn't fit. I eventually used a Magura adapter and the wheel now moves through the caliper without hitting any part of it. Aligned the caliper but it still seems as though it's a snug fit but difficult to hear if there is any rubbing. I even pushed the pistons all the was back. 

 

The back wheel now spins a good few times but then just comes to a halt, doesn't come to a steady slow stop, it just slows down and stops. Is this normal?

 

Also, they have developed a bit of a squeak now but only when I seem to break hard.

 

Thanks

[JXV]

Did you fit new pads with the discs? If not it may take a while for them to wear in especially if the old disc was worn.

 

If sqeaking then alignment of pads to disc is not 100% but this could be uneven wear on pads used with another disc.

 

Friction in the freehub mechanism will normally make the rear wheel lose momentum quicker than a front wheel when you spin them. If the wheel always comes to rest at the same place then it might be brake pads rubbing.

 

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[AlanD]

No, not new pads. Just used the existing pads that were used with the SRAM rotors. The pads are still in good nic so no need to change them.

 

So the pads may need a few rides to wear with the shimano rotors? I will check if the wheel comes to a stop at the same place.

 

The funny thing is, on  my ride they squeaked from the first pull of the lever so I stops, gave the rotors a wipe with my gloves in case there was some dirt on them and then the squeak only came when I braked hard.

[bikebloke]

I stand under correction but I was told that ice tech rotors are slightly thicker than ordinary rotors (no idea if its tru) and that you shouldn't mix them (unless indicated by shimano) with other brake types like you can with more generic rotors

 

maybe someone else has more details if this is vaguely correct ..

[JXV]

No, not new pads. Just used the existing pads that were used with the SRAM rotors. The pads are still in good nic so no need to change them.

 

So the pads may need a few rides to wear with the shimano rotors? I will check if the wheel comes to a stop at the same place.

 

The funny thing is, on my ride they squeaked from the first pull of the lever so I stops, gave the rotors a wipe with my gloves in case there was some dirt on them and then the squeak only came when I braked hard.

When a brake disc wears, the two faces do not necessarily wear exactly parallel, so the pads may also wear unevenly.

 

Now you fit new discs with exactly parallel faces....

 

Give it a few rides for them to settle in, then align them again if still not right. The brakes should bite a bit better once they wear in and the squealing should subside.

 

 

 

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[AlanD]

When a brake disc wears, the two faces do not necessarily wear exactly parallel, so the pads may also wear unevenly.

 

Now you fit new discs with exactly parallel faces....

 

Give it a few rides for them to settle in, then align them again if still not right. The brakes should bite a bit better once they wear in and the squealing should subside.

 

 

 

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Ok great. My pet hate is squealing or any noise on my bike but will give it a few rides to settle. Perhaps this will also free up the wheel a bit and make it spin more freely.

[AlanD]

I stand under correction but I was told that ice tech rotors are slightly thicker than ordinary rotors (no idea if its tru) and that you shouldn't mix them (unless indicated by shimano) with other brake types like you can with more generic rotors

 

maybe someone else has more details if this is vaguely correct ..

I did some googling before swopping over and loads of people had used shimano rotors in avid brakes with no issues so thought I would give it a go.

[bikebloke]

I did some googling before swopping over and loads of people had used shimano rotors in avid brakes with no issues so thought I would give it a go.

 

not all shimanos are icetech ..

 

it may be bull bro just putting it out there as I heard it ..

but I would make sure before you ride your bike you could muck a freewheel or your brakes or your face   if theres a problem and we don't want that

[AlanD]

not all shimanos are icetech ..

 

it may be bull bro just putting it out there as I heard it ..

but I would make sure before you ride your bike you could muck a freewheel or your brakes or your face   if theres a problem and we don't want that

Yeah, I hear you. After doing the deed I did ride it up and down the street to check the brakes work fine and there's no immediate danger...seemed to be ok.

[JXV]

I stand under correction but I was told that ice tech rotors are slightly thicker than ordinary rotors (no idea if its tru) and that you shouldn't mix them (unless indicated by shimano) with other brake types like you can with more generic rotors

 

maybe someone else has more details if this is vaguely correct ..

(Shimano) Brakepads have about 2mm of friction material when new and should normally be replaced when worn to about 0.5mm. I presume Avid pads are similar. Ice-tech rotors are 2mm thick when new and should be replaced at 1.5mm...so that's at least 3.5 mm of play that the calipers can take up. Then you need some clearance when the brakes are not applied.....

 

There is space to accommodate a slightly thicker disc provided the new disc and new pads fit with enough clearance to rotate freely when the pistons are fully retracted.

 

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[droo]

If you've pushed the pistons back and the brake's still binding, I'd suggest a bleed as a good starting point.

 

Also, don't wipe your rotors with anything that may have even the slightest trace of oil on it. Even touching them with your finger can contaminate them and cause squeaking.

[AlanD]

I am going to clean the rotors and pads with some isopropyl alcohol to ensure there is no contaminant's (or as little as possible) on them to stop the squeal. Then double check the alignment of the caliper to ensure all is good.

 

Go for a few rides to assess. If still persists then will bleed the brakes (need to learn the Avids and get a kit or do a DIY as I have always had only shimano.

 

Will take some pics tonight to get some advice if the rotor is sitting correctly in the caliper.

[AlanD]

Here are some pics. Looms like the pistons are not flush with the caliper despite me pushing them back. How do i get them flush?

[Sepia]

Wish my brakes looked like that.  I see no problem.

[JXV]

They appear to be riding a little high on the friction surface. Also too far in.

 

remove wheel and pads. Use piston spreader or similar tool to push apart. All 4 pistons same time. Dont lever directly onto the pads or pistons with a hard or sharp object. use old pads to protect if necessary. Those look new but if they were bled in the past with used pads in place instead of bleeder blocks they may now be overfilled and might not fully retract. Likewise if they have air in..... you'll get a spongy lever and the air will expand when the lever is released instead of the pads retracting.

 

If the brakes bite positively with no sponginess then no air bubbles.

 

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[AlanD]

Yes, the pistons seem too far in. I did use a tyre lever to push them back last weekend but didn't seem to move much.

 

The levers feel good and bite well. I have a shimano block, would that work in the avid brakes just to try get them back further or should i just bleed them?