Opinion on stripped threads in crank arm.

[JohnV]

When I purchased my road bike it came with toe clip pedals which I did not want. The LBS that I purchased the bike from swapped them out for regular platform pedals and all was well. A month later, when I did my first computer fitting (at another bike shop), they suggested that I get clipless pedals and so I did and they changed them out for me. However, when they went to change the right pedal, they noticed that it was cross-threaded toward the outside of the crank and had to tap it out in order to put the new pedal in.

Everything has been going well except today, toward the end of my ride, I started to notice that pedal was feeling different and my right foot was starting to wobble. When I got home, I looked at the crank and noticed that the pedal is stripped out and the crank now needs replacing.

I know that I'm going to have to eat this, even though the bike is only three months old because I can't prove that it was the original issue with the cross-threaded pedal that caused this to happen or the fact that it was tapped out and that may have screwed something up. Since there are two bike shops involved, I can't point the finger at any one in particular. So are there any ideas as to what may have caused this to happen? I can't take anyone's opinion to the bike shop, but I'm curious to know what others think.

I was planning to change the crank set from the FSA that's on it now to a Shimano Tiagra so it matches the rest of my drivetrain, anyway, but I was going to wait until late summer. I guess I have to do it now whether I want to or not.

[GeorgeET]

Bummer , on a new bike too. Sounds like you need to do more of the work yourself. Both shops screwed up. With the first being more of a screw up. Cross threading is inexcusable.

Since you planed to change cranks anyway I guess just move on. You could helicoil it to fix it, if that size is available, it can also be filled and rebored and retreaded. machine shop could do it for you. Although a new crank may be more cost effective. Check Nashbar lots of sales.

BTW I had lots of bikes and currently have a 1985 Fuji RB and a 1991 Schwinn MB. Never had problems with any of the components. After nearly twenty years my Schwinn SIS rear shifter started missing one gear so it was replaced. Those were all standard components . NO high end bragging rights. Todays components work well. The high end ones just require more labor to make and are lighter and more sculpted, not more reliable.The old friction Sun Tour shifters on my1985 Fuji still work fine.

Components can be changed frame cannot, always put your money in the frame first.

[Bill]

As George said above, parts are NOT what they used to be. There is another option but would be hard to come by and that is to find another crank that is on a the same kind of bike and just swap it out making it was not like the cross threaded one. Being the bike is only 3 mos old that may not really be an option. So if you do go with a new crank and are weary of the Bike shops doing the work then I can say from personal experience this site has some valuable minds with valuable tips and mechanical experience to help ya out! Only thing is to take a few pictures with each question you may have to help along the process .


Bill

Welcome to the site.

[JohnV]

My big problem with doing it myself is that I don't have the right tools or the workspace to do myself. I have some very good bike repair books and was looking at them last night, but I am going to need a table with a vise to get the pedal out of the crank arm and also to get the bushing off the pedal. On an FSA crank set, just replacing the crank arm and spindle doesn't seem to require any special tools according to my books.

Also, I would trust the second bike shop to do the replacement more than I would the first bike shop that cross-threaded the platform pedals. I have another bike shop not too far from me that has been around for almost 40 years and they are family owned and operated with their bike mechanics being there for many, many years. They are a little higher on their prices for parts and labor, but if worst comes to worst, I will take it there. The second bike shop also has more than one bike mechanic that have been around for years and also work on and race some very expensive road and MTB's. The fist bike shop has been around for years but his bike mechanic is a young kid and doesn't have that kind of experience. I'm going to be making some phone calls today to determine where the bike is going to be fixed.

I'll post the results later.

[Bill]

Oh ok. Again whatever you decide we are here.

[dave_sd]

Something similar happened on a friends bike that he bought from performance. I was helping him install clipless pedals and it was really hard to unscrew the pedals. I got one of them off and noticed it was dry. So I put it back on right away. I can't remember if we took it into the shop then or if we did the ride where it seized and stripped the entire crankarm of every thread it had. Anyway, since I had not removed the other pedal, we got them to admit they didn't grease the pedal threads when they put them on, and I think they bullied iron horse to warranty the crank. Then they tried to stick us with $40 labor to install the new crank. Jerks. Anyway what could have happened is they did not lube the pedal threads when they installed the pedals.

[JohnV]

When the second bike shop installed the clipless pedals, they did grease them because I was there watching when they installed them. Since the clipless pedals were installed, I have ridden the bike over 300 fairly hard miles, so I don't understand why all of a sudden it would do this on a fairly easy road ride. Here is what the crank looks like:

[attachment=1817]

[attachment=1818]

The pedal is still very tight on the crank bushing threads, but the crank bushing is what came loose. I'm taking the bike in tomorrow and hope that they can get the same crankset because I really don't want to replace the cassette and chain to match the new crankset.

[trevgbb]

First. if a pedal has been inserted with the thread crossed, you should notice it immediately you start to ride as the pedal will be at an angle to the crank arm and will feel very uncomfortable.
Other possible causes, fitting pedals on wrong side (common problem with home assembly), over or under tightened on second fitting, or seizing up of pedal bearings, or damage in use, ie, catching on kerb, etc. you will probably never know!
Greasing of thread, whilst useful to help with future removal, will have no effect on thread life.

[JohnV]

I took the bike back to the bike shop that installed the clipless pedals today to get the crank replaced. I found out that when they were taking the old pedal off and noticed that it was coming out slightly misaligned, they actually took photos of the pedal and the threads before and after the pedal was removed. I guess it was to protect their butts in case tapping the bushing didn't hold, or something. Anyway, they are going to email the photos to me tomorrow so I am now curious as to what the photos show.

I also talked to the mechanic who remembers installing the clipless pedals and he said that getting the old pedals off was a job and he said that the first shop really over tightened them. The one in question could have been tightened to the point that the face of screw head on the pedal became flush with the crankarm. Depending on the angle that the cross-threading was started, it is very possible that this is what happened, especially with a pressed bushing in an aluminum crank. The finer the threads, the more likely that this is can happen. I know first hand as it has happened to me a time or two when building and working on computers that had the old brass stand-offs to support the motherboards.

Regardless, I am going to have to cover the cost of it so I upgraded the crankset from an FSA Omega crankset that came on the bike to a Shimano Tiagra crankset, which is what should have come on the bike.

Trevgbb Wrote:Other possible causes, fitting pedals on wrong side (common problem with home assembly), over or under tightened on second fitting, or seizing up of pedal bearings, or damage in use, ie, catching on kerb, etc. you will probably never know!

You are right in your statement, I will never know for sure. Since everything so far is speculation and since none of the other things you mentioned happened, I am going to go with over tightening a slightly cross-threaded pedal.

[Darrenjs92ni]

i had a crank set on a cheap bike that both pedals were really stuck in, the threads got a wee bit of damage but are ok to use, my dad ran a tap down one of them i think their a UNF thread. theres a thing called a wire insert that can be used to replace the threads, i dunno how strong they are but.

ooo when changing cranks about you can have problems because with the different tappers(if it is a sqare tapper) i went to swap a crankset on one of my for an other and it sat further down the tapper than the original one did, so the front mech couldn't drop the chain on the lowest chainring!

[RobAR]

John - I'm not going to lay blame on any side but, I will offer you this for future reference...
I always install pedal washers on any bike that comes to me for clipless, or a bike that I know will be used hard. I have even been known to add them to $500 NIB builds that we floor and they do not come to us from the Mfr with them. This $2.00 investment is well worth it, IMHO.
It was your top pic that gave me chills, even after seeing the same on a few occasions. There are compound issues factoring in here. Look at how evenly the arm is dug into by the spindle flange and contemplate.

Pedal Washers. Always think Pedal Washers!
Because no-one but your mechanic will know, and he is sworn to secrecy.

[Darrenjs92ni]

ooo check that the thread on the pedal wasn't damage to before putting on a new crank it could wreck the thread on a new crank.

[JohnV]

I only wish that I had a place to work on my bikes other than the driveway. I don't have a garage or workshop so I'm pretty much at the mercy of the bike shops when it comes to certain repairs.

The good thing is that I can afford the repair without it doing any damage to my finances. The bike is last years model and I got it for $300 off the MSRP. The repair will run me about $200.00 so I'm still a little bit ahead of the game, but not by much. I guess that this is another one of those expensive life lessons that we keep running into every now and then.

[dave_sd]

I started out working on bikes in my 440 sq ft studio apartment. Just clear an area, put down plastic, put up a stand and you're ready to go! That place reamed me on the carpet cleaning fee when I moved out...

[JohnV]

(01-08-2011, 02:46 PM)dave_sd Wrote:  I started out working on bikes in my 440 sq ft studio apartment. Just clear an area, put down plastic, put up a stand and you're ready to go! That place reamed me on the carpet cleaning fee when I moved out...

Were you married? If so, you know why I don't do that.

[JohnV]

Just an update....Got the Defy back from the bike shop today with the new crankset. The Shimano Tiagra looks better on the bike than the FSA did. Anyway, I took the hybrid to get the pedals changed to the same clipless pedals as on the Defy and, to no surprise, they were over-tightened by the same LBS that cross threaded the pedals on the Defy. Luckily, no damage was done and they didn't have to tap the crank to get the pedals in. I'll continue to go the original LSB to purchase items, as he gives me a nice discount every time I go there, but I think I'll need to go somewhere else for any repairs for which I don't have the right tool to do the job. Just about lost all faith in the mechanic at this LBS.

[cyclerUK]

Unlucky with the pedals but glad your sorted.
I do all my own bikes if possible - if a job isn't done well then there is only one person to blame,
I appreciate you might not have much room but where do you store the bike?
Get the tool to change your own pedals and you can do it outside in about 5 minutes.
The tool takes up very little space and no work-stand needed.
(I scrapped my stand a few years back, none of our parents had stands and they worked on bikes for many years).
Minor jobs such as mending punctures and general maintenance require in the way of only small tools as well as costing very little.

[JohnV]

I keep my bikes out in a large shed in the back yard as I don't have a garage on the house. However, the shed isn't really large enough to set up a shop, even a small one. I do certain things on my bikes like change break pads and repair my tires and wheels and make cable adjustments. I actually have have the tools needed to change the pedals, but I don't have the BB removal tool. I could change them out with slip-joint pliers but that would just tear them up and I don't want to do that on a three month old road bike. The only reason the shops changed the pedals is because I was there with the bike when I got the pedals.

I don't mind spending the money on these tools to work with old bike, but both of mine and my wife's recumbent are less than a year old. I figure when they start needing replacement parts, I'll go and purchase the tools I need to do the job correctly. But since all the bikes are still under warranty, no point to it just yet. This crankset issue is something that would have turned out to be bike shop 1 said, bike shop 2 said. Let's see what happens with the crankset on the hybrid. Hopefully, that will last longer than 300 miles. Since the hybrid didn't cost me nearly as much as the road bike, if the crankset goes on it, I will replace it with one of the same make/model as I am not too picky as to what crankset is on that bike. This way I don't have to change out the BB, plus the crankset for the hybrid isn't very expensive, compared to the Shimano Tiagra.

[dave_sd]

(01-08-2011, 03:36 PM)JohnV Wrote:  

(01-08-2011, 02:46 PM)dave_sd Wrote:  I started out working on bikes in my 440 sq ft studio apartment. Just clear an area, put down plastic, put up a stand and you're ready to go! That place reamed me on the carpet cleaning fee when I moved out...

Were you married? If so, you know why I don't do that.

Nope, but my girlfriend leaves her bike in the trainer in the middle of the room most of the time, so I'm sure she wouldn't mind. Well, the grease in the carpet might bother her, slightly...

I can understand why your first mechanic over-tightened the pedals. The few crank installation manuals I've seen (looking at my FSA manual right now) recommended a torque of 29-34 Nm for pedals!! Everyone in this forum will agree that this is an insanely high torque value, and it's sufficient to do a small wrench makeup turn from finger tight.

What I've never been able to understand, however, is how you can physically tighten them that high. I tried to do it once, and I wasn't able to get enough leverage to hold the crank steady to torque them down. Maybe if you laid the bike on the ground and propped the cranks between rocks or something.

Anyway, glad this didn't happen to you again.

[FredS]

I just got married and now have no garage do to it being a staging area for all of the things we own and have not placed in the new house, so I just take a 5 gal bucket out to the driveway or front yard and start working.