Axle Bent on new bike...why?

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Axle Bent on new bike...why?

Postby mtbcrazy » Wed May 10, 2017 6:55 am

Hi
I received my Pacific Stratus from Amazon and assembled it.
I noticed right away the rear axle is slightly bent, by about 2mm at one end...it's got a 5 speed freewheel.
While pedaling hard, the rear hub makes a intermittent knocking sound.
Also, when I spin the rear wheel with it off the ground and the chain disconected, I can hear unusual bearing noise.

(1) How did the axle get bent on a new bike out of the box?

(2) How do I straighten the axle?

Thanks!

Image
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Re: Axle Bent on new bike...why?

Postby to the beach » Wed May 10, 2017 4:19 pm

You may have to remove and strip down the axle. Then, roll it on a flat surface to examine the bend. There isn't really any way to safely straighten an axle. Maybe Pacific will ship you a new wheel under warranty?? If you're on your own, then buy just the axle on Amazon.com.

There are basically 2 axles, SAE sized axles are for coaster brake, metric sized axles are for freewheel.
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Re: Axle Bent on new bike...why?

Postby Tomcat65 » Wed May 10, 2017 4:45 pm

Unfortunately, this happens.. A lot. The freewheel design hubs are prone to bending axles and most low cost bikes have low cost, softer materials. Axles are the first thing I suspect any time I have a shifting problem. The problem with freewheel hubs is that the bearings are mounted inboard of the gear set. This leaves a good inch or better of unsupported axle from bearing to frame attachment. The easiest fix is to expect the axles to bend, and go with good quality chromoly replacement axles, 10mm rear with new bearing cones and nuts.. 9mm front. The "no cost too high" route, get a new freehub wheelset and a new cassette gearset.
If you look at where the bearings are on the comparison below, you'll see the difference for yourself:
99985.jpg
freehub top, freewheel bottom
99985.jpg (46.69 KiB) Viewed 300 times

The freehub design is more expensive to produce and has more parts. So, you won't see it on many BBB's
New axles cost anywhere from $8 to $35.. I try to find what I want in the $20-$25 range and expect a good quality axle

Option 3, mark the ends of the axle to indicate the direction of the bend, loosen both ends and clock the bent axle to where it works best. Not a great answer, but it might get you by for a while. You might try turning the bend downwards, then when you load the axle, it will stress the axle in a straightening direction. Might not work, but keep in mind, the axle does not turn after you tighten it to the frame..

Faulty freewheel cogs are often mistaken for bent axles as they wobble around while pedaling. A cross threaded or improperly machined freewheel seat can also cause freewheel wobble while pedaling.
Faulty hub machining (off center bores) will cause the freewheel to wobble while coasting.
Bent axles just throw the alignment off randomly every time you remove and replace the wheel
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Re: Axle Bent on new bike...why?

Postby dddd » Wed May 10, 2017 10:42 pm

mtbcrazy wrote:...I noticed right away the rear axle is slightly bent, by about 2mm at one end...it's got a 5 speed freewheel.<br abp="729">While pedaling hard, the rear hub makes a intermittent knocking sound.<br abp="730">Also, when I spin the rear wheel with it off the ground and the chain disconected, I can hear unusual bearing noise.<br abp="731"><br abp="732">(1) How did the axle get bent on a new bike out of the box?<br abp="733"><br abp="734">(2) How do I straighten the axle?...Thanks!]


I had the exact symptoms on my Pacific Mongoose Hondo, which I and the Pacific representative believed was caused by the box being dropped.
I had the bent axle, and the bearing cup had also become loose in the hubshell, so had all of the same symptoms you described.

Pacific simply sent me a new wheel, no charge, to replace the one with damaged hub.

I was able to repair the damaged one by pulling out the axle, then putting a few drops of Red Loctite around the bearing cup, applied from inside the hub shell through the left-side of the hubshell after the axle was removed and using a penlight to confirm that the Loctite had dripped down into the crevice around the bearing cup.
I then heated the hubshell medium hot using a hair drier, to fully cure the liquid Loctite.
I also replaced the axle assembly with a solid 10mm axle assembly, and the whole thing now has about 800 off-road miles on it with no more creaking and no more bent axles.
I kept the new replacement wheel as a spare.
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Re: Axle Bent on new bike...why?

Postby mtbcrazy » Thu May 11, 2017 6:38 am

Tomcat65 wrote:The easiest fix is to expect the axles to bend, and go with good quality chromoly replacement axles, 10mm rear with new bearing cones and nuts.. 9mm front.


I ordered a new hub from Niagaracycle...WheelMaster Steel Rear Hub, 36H x 80G, 126mm, 5/6 Speed.
It's only $5...I already have a spare Sun rim, so I plan to build a new wheel.
  • Do you think Wheelmaster is a good brand?
  • Do you think it has a chromoly axle in it?
Image


Tomcat65 wrote:Faulty freewheel cogs are often mistaken for bent axles as they wobble around while pedaling. A cross threaded or improperly machined freewheel seat can also cause freewheel wobble while pedaling.
Faulty hub machining (off center bores) will cause the freewheel to wobble while coasting.
Bent axles just throw the alignment off randomly every time you remove and replace the wheel


I agree. After carefully studying the freewheel, I determined that main culprit for the knocking sound is a faulty, wobbly freewheel which causes the chain and cog to rub intermittently.
And I'm certain the axle is slightly bent (but only slightly)...and it is a minor culprit like you suggested.

I've also ordered this freewheel from Niagara $9...Sunrace 5-Speed Freewheel, 14-28T
I hope this is a decent quality brand.
Image
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Re: Axle Bent on new bike...why?

Postby dddd » Thu May 11, 2017 4:12 pm

The Sunrace freewheels are better than most bbb parts these days.

The hub should be ok, but if the freewheel alone is making the noises, wouldn't replacing just the axle be far easier?
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Re: Axle Bent on new bike...why?

Postby mtbcrazy » Thu May 11, 2017 4:36 pm

dddd wrote:The Sunrace freewheels are better than most bbb parts these days.

The hub should be ok, but if the freewheel alone is making the noises, wouldn't replacing just the axle be far easier?


When I receive the Wheelmaster hub, I'll remove its axle and put it into the current Pacific hub.
And I'll install the new SR freewheel.
If this fixes the knocking noise, then it's good and easy.

But if not, then that means the current Pacific hub is not machined properly, I'll have to replace it.
That means building a new wheel.
That's okay...I have a new wheel truing stand that I've been itching to use.

I probably should call Pacific for warranty...and get a spare wheel like you did.
How did you contact Pacific Cycle?
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