Bent Rim and rubbing disc rotor

[Bergbok]

Hi Hubbers,

 

Maybe this has been asked before. I remember Johan B commenting about bent chain stays or something but I can't find the post...

 

Anyway, washing my bike after Attekwas I realised that my rear wheel ( ZTR Olympic) does not spin freely. Infact it stops immediately - severe friction. No wonder Attekwas was tough...

On closer inspection I see that the rim has got a wobble. About 3 mm out on one side.

 

Now 2 questions I was wondering about:

 

• I read in another post that if a rim is damaged (as apposed to a loose nipple) it is not repairable and the wheel needs to be rebuild with a new rim. Is this true in all cases or how bad must the damage be? When can it be trued and when not?

 

• When bike is upside down and skewer not fastened, the wheel spins freely. When skewer tightned, wheel is locked against pads. Why does this happen? My point being that the disc rotor is part of the hub and not the rim, so a bend rim should not influence the disc rotor… or am I missing something?

 

Hope description is clear enough. Will take the bike in on Thursday to find out about the wheel, but I’m curios to know about how the skewer influences the whole problem.

[MintSauce]

In all likelihood your disc rotor is bent or you just need to have your brake caliper adjusted. I'm guessing it's the rotor seeing as it spins freely and then stops suddenly. If it was the caliper alignment it would touch slightly but still spin freely.

 

The wheels spins freely when the QR is loosened as the bent disc causes the wheel to be pushed out of position to compensate for the bent disc. Once the QR is tightened it keeps the wheel in the correct position and since there's no more give the rotor makes contact with the pad causing the wheel to stop.

 

A decent shop should have a rotor truing fork, which is a basic device used to straiten the rotor, unless they're too lazy and want to sell you a new rotor.

 

As for the rim, a 3mm buckle is not too serious, but you should have it sorted.

 

What brakes do you run?

[Bergbok]

In all likelihood your disc rotor is bent or you just need to have your brake caliper adjusted. I'm guessing it's the rotor seeing as it spins freely and then stops suddenly. If it was the caliper alignment it would touch slightly but still spin freely.

 

The wheels spins freely when the QR is loosened as the bent disc causes the wheel to be pushed out of position to compensate for the bent disc. Once the QR is tightened it keeps the wheel in the correct position and since there's no more give the rotor makes contact with the pad causing the wheel to stop.

 

A decent shop should have a rotor truing fork, which is a basic device used to straiten the rotor, unless they're too lazy and want to sell you a new rotor.

 

As for the rim, a 3mm buckle is not too serious, but you should have it sorted.

 

What brakes do you run?

 

Thanks for the reply.

The rotor seems perfectly straight, atleast when doing a visual inspection.

What bothers me is that I "press down" the wheel into the frame without the skewer fastened and then spin it without problems, so i don't think the wheels move to compensate. The sidewards pressure of the skewer seems to cause the problem.

 

You might be correct though... will let them check it out.

Your explanation does make sense though: If the caliper did not move and the wheel is in the correct position, the rotor must be bent...

 

I am running Sram X0. about a month old.

 

Thanks

[TNT1]

 

A decent shop should have a rotor truing fork, which is a basic device used to straiten the rotor,

 

 

Called a stove and a pot?

[Johan Bornman]

Hi Hubbers,

 

Maybe this has been asked before. I remember Johan B commenting about bent chain stays or something but I can't find the post...

 

Anyway, washing my bike after Attekwas I realised that my rear wheel ( ZTR Olympic) does not spin freely. Infact it stops immediately - severe friction. No wonder Attekwas was tough...

On closer inspection I see that the rim has got a wobble. About 3 mm out on one side.

 

Now 2 questions I was wondering about:

 

• I read in another post that if a rim is damaged (as apposed to a loose nipple) it is not repairable and the wheel needs to be rebuild with a new rim. Is this true in all cases or how bad must the damage be? When can it be trued and when not?

 

• When bike is upside down and skewer not fastened, the wheel spins freely. When skewer tightned, wheel is locked against pads. Why does this happen? My point being that the disc rotor is part of the hub and not the rim, so a bend rim should not influence the disc rotor… or am I missing something?

 

Hope description is clear enough. Will take the bike in on Thursday to find out about the wheel, but I’m curios to know about how the skewer influences the whole problem.

 

First try and isolate the problem. Remove either the disc or the caliper so that we know the brakes don't come into the equation. Now spin the wheel. Experiment with the QR tight and loose.

 

If a tight QR causes the wheel to bind, it is either that the two drop-outs are not parallel or, that the axle is bent.

 

To look for a bent axle, hold the wheel (without skewer) horizontally in your lap. Keep your eye on the axle whilst rotating it from the bottom, using your fingers. You'll see the axle wobble....or not.

 

If not the axle, the drop-outs need attention. This can be done at home, but you do need patience and confidence.

 

Place the bike in a workstand so that the back wheel can run freely. Remove the caliper. Now alternatively tighten and loosen the QR whilst keeping an eye on the drop-outs and isolate the bent drop-out. I suspect it will only be one. You will look for movement and/or light through gaps. Once you've located the problem DO, now try and figure out the plane of the bend. Use a shifting spanner and judiciously place it on the drop-ouy (wheel off) and make little bends. Check the whole procedure afterwards. The proof of the pudding will be a wheel that runs freely.

 

If you don't have the appetite for this, find a bike shop with a drop-out aligning tool and experience.

 

Good luck.

[Johan Bornman]

Hi Hubbers,

 

Maybe this has been asked before. I remember Johan B commenting about bent chain stays or something but I can't find the post...

 

Anyway, washing my bike after Attekwas I realised that my rear wheel ( ZTR Olympic) does not spin freely. Infact it stops immediately - severe friction. No wonder Attekwas was tough...

On closer inspection I see that the rim has got a wobble. About 3 mm out on one side.

 

Now 2 questions I was wondering about:

 

• I read in another post that if a rim is damaged (as apposed to a loose nipple) it is not repairable and the wheel needs to be rebuild with a new rim. Is this true in all cases or how bad must the damage be? When can it be trued and when not?

 

• When bike is upside down and skewer not fastened, the wheel spins freely. When skewer tightned, wheel is locked against pads. Why does this happen? My point being that the disc rotor is part of the hub and not the rim, so a bend rim should not influence the disc rotor… or am I missing something?

 

Hope description is clear enough. Will take the bike in on Thursday to find out about the wheel, but I’m curios to know about how the skewer influences the whole problem.

 

First try and isolate the problem. Remove either the disc or the caliper so that we know the brakes don't come into the equation. Now spin the wheel. Experiment with the QR tight and loose.

 

If a tight QR causes the wheel to bind, it is either that the two drop-outs are not parallel or, that the axle is bent.

 

To look for a bent axle, hold the wheel (without skewer) horizontally in your lap. Keep your eye on the axle whilst rotating it from the bottom, using your fingers. You'll see the axle wobble....or not.

 

If not the axle, the drop-outs need attention. This can be done at home, but you do need patience and confidence.

 

Place the bike in a workstand so that the back wheel can run freely. Remove the caliper. Now alternatively tighten and loosen the QR whilst keeping an eye on the drop-outs and isolate the bent drop-out. I suspect it will only be one. You will look for movement and/or light through gaps. Once you've located the problem DO, now try and figure out the plane of the bend. Use a shifting spanner and judiciously place it on the drop-ouy (wheel off) and make little bends. Check the whole procedure afterwards. The proof of the pudding will be a wheel that runs freely.

 

If you don't have the appetite for this, find a bike shop with a drop-out aligning tool and experience.

 

As for the rim. If the rim is laterally bent, no amount of truing can fix it. You’ll always have spokes with too much tension on the one side and too little on the other side.

A flat spot in a rim is easily repairable. Take it to a competent wheelbuilder.

The beauty of disk brakes is that they can be out of true and it doesn’t matter.

 

Good luck.

Edited January 18, 2011 by Johan Bornman

[MintSauce]

Does the wheel spin at all when the QR is tightened? I mean does it turn freely for a bit and then get stuck or does the rotor rub through the whole revolution?

[werner J]

Same issue here Bergbok.. Alow me also to ask

 

Mintsauce, your oppinion:

 

I Dentet my American Classic. The tubeless seal was broken after the impact. Fterward my tubeless seals again, but dent is still there. Will a good shop be able to repair dent in the rim?

 

Werner

[Bergbok]

First try and isolate the problem. Remove either the disc or the caliper so that we know the brakes don't come into the equation. Now spin the wheel. Experiment with the QR tight and loose.

 

If a tight QR causes the wheel to bind, it is either that the two drop-outs are not parallel or, that the axle is bent.

 

To look for a bent axle, hold the wheel (without skewer) horizontally in your lap. Keep your eye on the axle whilst rotating it from the bottom, using your fingers. You'll see the axle wobble....or not.

 

If not the axle, the drop-outs need attention. This can be done at home, but you do need patience and confidence.

 

Place the bike in a workstand so that the back wheel can run freely. Remove the caliper. Now alternatively tighten and loosen the QR whilst keeping an eye on the drop-outs and isolate the bent drop-out. I suspect it will only be one. You will look for movement and/or light through gaps. Once you've located the problem DO, now try and figure out the plane of the bend. Use a shifting spanner and judiciously place it on the drop-ouy (wheel off) and make little bends. Check the whole procedure afterwards. The proof of the pudding will be a wheel that runs freely.

 

If you don't have the appetite for this, find a bike shop with a drop-out aligning tool and experience.

 

As for the rim. If the rim is laterally bent, no amount of truing can fix it. You’ll always have spokes with too much tension on the one side and too little on the other side.

A flat spot in a rim is easily repairable. Take it to a competent wheelbuilder.

The beauty of disk brakes is that they can be out of true and it doesn’t matter.

 

Good luck.

Thanks lots Johan, Will play around tonight.

Think I will still take the bike in eventually to be on the safe side.

 

You help is greatly appreciated

[Bergbok]

Does the wheel spin at all when the QR is tightened? I mean does it turn freely for a bit and then get stuck or does the rotor rub through the whole revolution?

 

When QR is fastened wheel does not spin at all. It is stuck... Can rotate wheel, but it def does not spin and then stop when rotor touches pad at some point. friction is for the full 360 degree rotation

[MintSauce]

When QR is fastened wheel does not spin at all. It is stuck... Can rotate wheel, but it def does not spin and then stop when rotor touches pad at some point. friction is for the full 360 degree rotation

 

Have you tried loosening and realigning the caliper?

[Bergbok]

Have you tried loosening and realigning the caliper?

 

No I did not yet do anything yet. Agree it might solve the problem, but my thinking was: if the wheel is mounted "flat" in the dropouts as previously and caliper did not move, there should be no friction and wheel should be fine as before Attekwas. I therefor thought that maybe something else also got damaged with the rim like the dropouts or axle as mentioned in Johan's reply.

[MintSauce]

No I did not yet do anything yet. Agree it might solve the problem, but my thinking was: if the wheel is mounted "flat" in the dropouts as previously and caliper did not move, there should be no friction and wheel should be fine as before Attekwas. I therefor thought that maybe something else also got damaged with the rim like the dropouts or axle as mentioned in Johan's reply.

 

 

Ok, if the rotor is straight then the next step would be to realign. Just loosen the two bolts, just enough for the caliper to move side to side. Pull the brakelever to align the caliper on the rotor and while holding the lever in, gently re-tighten the caliper bolts, little by little, alternating between the two bolts.

 

If this does not resolve the problem, then you need to start looking at the axle and dropouts as Johan mentioned.

[MintSauce]

Same issue here Bergbok.. Alow me also to ask

 

Mintsauce, your oppinion:

 

I Dentet my American Classic. The tubeless seal was broken after the impact. Fterward my tubeless seals again, but dent is still there. Will a good shop be able to repair dent in the rim?

 

Werner

 

It depends on how badly it's dented. Aluminium doesn't really like being bent back and forth. If the dent is quite severe then it's likely to form a crack if you try and bend it back.

I generally don't bother with fixing dents if it seals up again. If it doesn't then it's a different story, but even then I'd be very weary of it forming a crack and only bend it out enough until it seals.

[The Drongo]

When QR is fastened wheel does not spin at all. It is stuck... Can rotate wheel, but it def does not spin and then stop when rotor touches pad at some point. friction is for the full 360 degree rotation

 

 

What rear hub are you running?

 

Have you whiped out the QR and run the wheel on the axle?

 

Bearings ceased maybe?

Edited January 18, 2011 by The Drongo