Thread busted on right pedal crank

[zippy]

Hi

Ive joined to specifically ask about a problem which may have been covered before Im sure.

My right pedal broke so I had to replace it. Then had issues getting the new pedal to go on straight so I was riding with it slightly at a bend. But then it just came loose and fell off.

Problem is now the thread seems busted and the pedal just slots in with no screwing needed because the hole is enlarged. Just has a bit of thread grip at the end. But its not enough to withstand any pedaling pressure for more than a few minutes riding. Just comes off!

Is it possible to glue/bond the pedal on with a metal glue? I dont have much money for big repairs or costly replacements. What are the options? Im not bike repair savvy so please keep any replies simple and non techy! cheers

[dave_sd]

Take it to your local bike shop and see if they can drill it out and install a helicoil

[zippy]

thanks but that could be expensive. I wanted to know any DIY methods...cheap!

[RobAR]

zippy - if the threads are stripped in the crankarm, there is no inexpensive DIY. I would not even advise the helicoil. Sorry.

[JohnV]

This story sounds all to familiar to me. Zippy, all I can say is I've been there, done that and as Rob said, "there is no inexpensive DIY." Start looking on the Net for a new replacement crankset.

[dave_sd]

The crank is trashed, so you may as well try jb weld or something if you don't mind trashing your pedals if it doesn't work

[JonB]

...just make sure you have bombproof life insurance!

Seriously, don't. That's asking for pain. Bin it and get a new set. Probs not what you wanted to hear but that's only solution. Sorry.

[zippy]

So none of you seem to think that any form of bonding would work? Is that because you dont think it would withstand the pressure put on it(uphill for instance)? Or is it any other reason?

The bike only cost me £25($40) secondhand which was an amazing bargain from a private ad. Its a Giant boulder mountain bike which is just the perfect size and look for me so I would like to keep it. Then again, Im not losing big money here like other serious bikers with expensive bikes. Which is why Im reluctant to spend big money on getting it repaired.

Ive never heard of jb weld, was that a serious suggestion? There are other strong metal glues. I dont really have anything to lose trying to bond it if the only other solution is a new crank. Pedals are easy to acquire(you can even get them at my local pound/dollar store!)

I have read another thread about a successful helicoil job too so Im not sure why thats also been shot down.

[JohnV]

A helicoil may fix the problem today, but how long will it last before the stress on it causes it to fail. Did the other thread say how long the helicoil lasted? Unless he has been riding on the helicoil repair for years and thousands of miles, I would be very concerned about the safety feature more than a cheap way to get it fixed.

I have a Giant Defy road bike that had one of the pedals slightly cross-threaded when it was installed by the LBS I bought it from. I later had clipless pedals installed by a different LBS and that is when the cross-threading was noticed. They tapped out the threads and installed the new pedal. Worked great, no problem. Right at three hundred miles of riding with the clipless pedals, the right crank pedal did the same thing that yours did. It cost me a new crankset.

A new Giant Boulder runs around $350.00 USD, so although not a high end bike, it isn't exactly a low end, department store bike (nothing against department store bikes). Regardless of what you paid for it, if the bike is in decent condition and you really like it, then its worth getting a new cranset for it. The Boulder normally comes with the SR SunTour crankset that is the same as the one on my Giant Cypress. I have seen them on the Net for around $35.00 USD (cheaper on some sites). You may even be able to find a used one at a LBS for even less.

[JonB]

I completely agree with that. Even new, Giant Boulders are a bargain for what you get, so it's worth spending money on it.

Oh and no, don't buy pound/dollar shop pedals. These are completely useless, even 5:10 shoes won't be able to grip them and the bearings will be toast after a trip to the shops! This bike really IS worth spending money on.

As for repairing the crank, this is why I would bin them:
scenario 1 (assumes you use it as a commuter bike):
you're riding along in heavy traffic, eventually the repair fails and the pedal falls off without warning, you go straight down into the path of a Chelsea Tractor (SUV ). Pain follows.

scenario 2 (assumes you use it off-road)
Again, you're riding along and the repair fails. You go straight down, possibly tumbling down a steep hill or smashing into a tree/boulder.


By the way, I had one of those Suntour cranksets on my Hardrock. After a year and a half of abuse off-road the pedal insert bent quite noticeably. Put a half decent Shimano crankset on it (Deore or above) if you ride off-road.

[JohnV]

Quote:By the way, I had one of those Suntour cranksets on my Hardrock. After a year and a half of abuse off-road the pedal insert bent quite noticeably. Put a half decent Shimano crankset on it (Deore or above) if you ride off-road.

I agree here. The SunTour crank on my Cypress has lasted for over 2,000 miles and is still going strong. But.... I don't take it off the road. If you are going to subject it to a lot of abuse such as strictly off road and mountain trails, then look at the Shimano as JonB said. There are other excellent brands that you can look into but they cost more than the Deore cranks.

[dave_sd]

I'm with everyone else on this thread, you need a new crank. However, for your own knowledge, http://jbweld.net/index.php
I used it in some of my design/build classes in school. Works like a champ when the application can accept it!

[zippy]

well Im gonna take it to a local repair shop and see what they suggest. I may even buy a new Giant bike for the summer so theres another reason not to spend too much on this.

I may still try bonding it just to satisfy my curiosity as Im obsessed with the idea. There must be some glue strong enough. or maybe even weld it on? I just read something about a pedal being welded on so I assume it was because the thread went also.

I really dont know why they persist with these pedal connections. Surely some simple nut/bolt device would suffice and be much less prone to these thread issues. Seems ridiculous to have to replace the whole crank just because you cant attach a pedal! If the pedal had a longer thread that came out the back end of the crank hole then I could attach a nut to hold it in place. They should sell pedals with this option for people like me!

Then again, I guess its in the industries best interest to make us buy new parts *light bulb*.

I dont know anything about cranks either! They seem to have different sizes and types so I wouldnt even know what to get. I could probably put it on myself following instructions but I dont have that crank tool you need too screw in and remove it(??). Plus do you have to then adjust your gears or anything? I can fix breaks but gears I usually stay clear of because I know nothing.

ps; one of the reviews for jb weld on amazon uk does say they used it to fix a bike pedal and it works perfect. Ha!

[zippy]

does anybody know which jb weld would be best to use? theres the normal cold weld for around £4 on ebay which seems to be the one generally used. But then there are more heavy duty ones like industro weld which is more expensive at £20..although it seems to be over 4 times bigger in weight content so Im not sure if its strength is so much more or whether its the amount you get that makes it so much more expensive.

this stuff looks useful so at £4.80 total(with p&p) its worth a try at least. Im sure it will be handy for other jobs too even if the pedal experiment fails. Im not setting my hopes too high.

ps; in my google jb weld search I came across this funny looking bike!

http://www.flickr.com/photos/carnutt2002/sets/72157617307091795/

[DaveM]

Before you blow £20 on glue (JB Weld is epoxy, the use of the word "weld" is just marketing) just buy another used bike and swap the cranks. Or just buy a new right crank arm. That shouldn't cost more than £20 either. Gluing the pedal in might work for a little while. But it will break eventually and will probably do so in a way that could cause you to crash and get hurt.

When pedals are installed correctly, they last indefinitely. Yours were either put on wrong at some point or ridden loose for a long time which damaged the threads.

[zippy]

well Ive said it was put on incorrectly. But this all happened in the space of two days. The thread was busted after just a couple of hours riding. So obviously it doesn't take much wear to destroy them. It was tightened to the base but it was slightly angled so one side had a tiny gap.

Replacing cranks may seem easy to you and others here but I know nothing about them so its daunting. I do actually have an old bike out back that may have a similar crank but I have no idea about compatibility.

Pedals could last indefinitely with a more versatile connection. This one seems all or nothing. I'm not mechanically savvy but having a thread at one of the most high impact points of a bike doesn't seem wise. And those pedals are not easy to put in straight sometimes. My case proves my point and theres many other similar stories. Putting a pedal on should be simple!

[DaveM]

It is not the strongest possible design and I certainly won't claim that bikes couldn't be better designed for long term durability. But if what your saying is that you should be able to cross thread something and expect it not to break is not a powerful critique of bike design.

You messed up and cross threaded something and it broke. I've done it and I bet lots of others have. But I wouldn't really call that a design flaw. It's called screwing up.

I think most people here agree that gluing probably won't work well, but you're welcome to try it. The other options are helicoil or swapping the cranks. If the other crank set you have is from a similar style of bike, it will probably work fine. But of course, hard to know for sure without more info. If you post details about both, someone here can probably recommend.

[zippy]

what I'm saying is that putting a pedal on could be much easier and you should not be able to destroy your crank in the process. All I did was try to screw on a pedal! I tried many times to screw it on proper straight but when all you have is a spanner theres not much you can do. So you put it on best you can like I did. I wasn't aware that it would be so fickle that it would destroy the thread within a day.

Even I could come up with a more foolproof connection device. In my experience threads are stupid things to have at high impact points because they're obviously vulnerable.

[DaveM]

I would absolutely agree that machines should be designed to be more foolproof and more durable. Threaded connections are vulnerable, but they do have advantages too. Bikes tend to be designed to be "just strong enough" for cost, weight, and size issues. In general I think they have a very good balance, but there's always room for debate on where to draw the line. If you think pedal threads aren't strong enough, you should see some of the crazy handlebar/stem designs they're making these days that if you don't install them with a high end torque wrench you can easily snap them during normal riding.

[JohnV]

Zippy, the issue here is not the overall design of the pedals and the crank arm but metals that are used to make the parts. You have aluminum used to make the crank arm and tempered steel to make the pedal. If you made the crankarm of tempered steel, cross-threading would not occur as often and as easy, but the bike would weigh a lot more than what some people want it to. If you made the pedals of aluminum, they would not last as long because the aluminum would heat up during the rotation of the pedal platform around the shaft and cause it to bind. Since the aluminum is much softer than the tempered steel, it is very easy to cross-thread a pedal if you are not careful.

As far as making the pedal thread long enough to extend past the back of the crank arm so you can put a nut on it, you now are causing the crankarm to have more of an outward curve to avoid hitting the frame. This causes the feet to be placed further away from the center of the bike causing an incorrect angle on the downward stroke of your leg. It may not seem much when you are doing short rides, but for those of us that do very long distances, this is a major deal.