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Weird Bike Torque? Issue

post #1 of 9
Thread Starter 

So I was out on a ride tonight and starting to go downhill it felt like I had a loose tire. The bike was noticeably shaking from side to side. I stopped, checked the quick releases and brakes and such on both tires and it all seemed fine. Got back on, still an issue. Once I got above a certain speed the feeling seemed to dissipate (or it could just the it was masked by the normal bumpiness of the roads here at speed). However once I drop back down its back. I'd say between about 10-20 mph range the bike is shaking very noticeably. IE on a downhill stretch of paved road if I take the weight off the handle bars it is shaking from side to side. But the feeling is almost like the whole frame is twisting, when I looked down it wasn't just the handle bars but the entire frame seemed to be rocking side to side. 

 

My back tire is slightly bent, but it has been that way for a while. It's a by product of riding a fairly narrow tire on the pot holed and dirt roads (more like wide MT bike trails) here. I was riding a particularly bumpy section pretty aggresively, but the tire doesn't appear to be any more bent than it was when I started. Any ideas for a cause?

post #2 of 9

Broken axle.  Check the rear first.  Pull the wheel off and see if it's still in one-piece.  Could also be the bearing surfaces in the hub have broken or are no longer secured to the hub itself.  You'll have to disassemble the hub to see if that's the case.

post #3 of 9
Thread Starter 
Quote:
Originally Posted by Scott43 View Post
 

Broken axle.  Check the rear first.  Pull the wheel off and see if it's still in one-piece.  Could also be the bearing surfaces in the hub have broken or are no longer secured to the hub itself.  You'll have to disassemble the hub to see if that's the case.

 

Thanks, makes sense. The last ride I had an issue where the tire popped off. Fortunately 50m down the road from a bike shop. The nut on the end of the axle was messed up somehow, I forget exactly, but he fixed it and it seemed fine. Probably was a by product of a larger issue. 

post #4 of 9
Quote:
Originally Posted by tylrwnzl View Post
 

 

Thanks, makes sense. The last ride I had an issue where the tire popped off. Fortunately 50m down the road from a bike shop. The nut on the end of the axle was messed up somehow, I forget exactly, but he fixed it and it seemed fine. Probably was a by product of a larger issue. 


Ahh..could also be a bulge in the tire or the tire is mounted unevenly.  Check the bead-line to see if it's consistent with the edge of the rim. 

post #5 of 9
Thread Starter 
Quote:
Originally Posted by Scott43 View Post
 
Quote:
Originally Posted by tylrwnzl View Post
 

 

Thanks, makes sense. The last ride I had an issue where the tire popped off. Fortunately 50m down the road from a bike shop. The nut on the end of the axle was messed up somehow, I forget exactly, but he fixed it and it seemed fine. Probably was a by product of a larger issue. 


Ahh..could also be a bulge in the tire or the tire is mounted unevenly.  Check the bead-line to see if it's consistent with the edge of the rim. 

 

Forgive my ignorance, but bead line? I don't think it is a mounting issue, the guy at the shop remounted the tire when he fixed it yesterday and I rode that same section that I did today without any issues. 

post #6 of 9
Thread Starter 

Ok so I went down and flipped the bike up to check it out further. It was near dark when I was out riding, I think maybe I did bend the tire further. Think this is enough to be noticeable?: 

 

post #7 of 9

That's not terrible, but you would notice that.  It's still salvageable if you choose to have it straightened, it's not that bad.  Depending on  how many times it's been trued, how badly it's been banged up in the past. 

 

Bead line..there is often a line cast into the rubber of the tire near the bead (the part that goes into the rim when mounted).  It's a guide to make sure the tire is evenly mounted all the way around.  Sometimes the tire will stick down and not pop up evenly all the way around when inflated.  You basically end up with a flat spot in the tire that causes a bump every revolution. 

 

I'd still pop the quick release, pull the wheel out of the dropout and check the hub/axle/bearings, just to make sure it's not loose and it's in one piece. 

post #8 of 9
Thread Starter 
Quote:
Originally Posted by Scott43 View Post
 

That's not terrible, but you would notice that.  It's still salvageable if you choose to have it straightened, it's not that bad.  Depending on  how many times it's been trued, how badly it's been banged up in the past. 

 

Bead line..there is often a line cast into the rubber of the tire near the bead (the part that goes into the rim when mounted).  It's a guide to make sure the tire is evenly mounted all the way around.  Sometimes the tire will stick down and not pop up evenly all the way around when inflated.  You basically end up with a flat spot in the tire that causes a bump every revolution. 

 

I'd still pop the quick release, pull the wheel out of the dropout and check the hub/axle/bearings, just to make sure it's not loose and it's in one piece. 

 

Thanks I will do; it's a pretty cheap rim anyhow, so not a huge deal if I need a new one. I will check the axle though. Probably just go to the bike shop and have them do whatever they tell me needs done. Just a lot easier to tell them "I think the back tire is broken" in Spanish than explaining a torque feeling at varying velocities.  

post #9 of 9
Quote:
Originally Posted by tylrwnzl View Post
 

 

Thanks I will do; it's a pretty cheap rim anyhow, so not a huge deal if I need a new one. I will check the axle though. Probably just go to the bike shop and have them do whatever they tell me needs done. Just a lot easier to tell them "I think the back tire is broken" in Spanish than explaining a torque feeling at varying velocities.  


Yup..any mechanic worth his salt will notice in 5 seconds that the axle is broken..and in 15 seconds that the hub races are damaged once they try to true it.  :D

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