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Thread busted on right pedal crank
#21
ok Ive decided to replace the crank after asking 2 local bike mechanics. Plus I could never trust a bonded pedal...especially going uphill!

But I want to do it myself to save money. I have found a crank set on ebay for just £11.50 + £3.50 postage. Its new and from rep dealer. Its sold over 50 of them and has 100% feedback.

Do you think this is suitable for my Giant boulder as Im not sure; Coyote triple crankset with 24/34/42 teeth & 170mm arms. Black steel & plastic chainguard.
[Image: 97r8yw.jpg]

Im worried about compatibility issues...or having to adjust the gears or chain. I think I can manage the crank replacement part following instructions. I need to buy or borrow a crank removal tool too.

But now Ive seen a suntour crank on ebay with 48-38-25 chainrings so thats bigger. This would effect the chain would it not? Does it matter about the ring size differences?

edit; now seen another at £20 total new; this is 48/38/28
[Image: fcme07.jpg]
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#22
If you don't want to change more parts, stay as close to your original crankset as possible. Also, make sure that the cranksets you are getting are compatible with the BB and chain or you will need to change them as well. BB's are not very expensive, but chains can be.

I've never heard of the Coyote brand, but like the SunTour (and everything else now-a-days) it's most likely made in China. SunTour cranks are used by many bike manufacturers for their less expensive bikes, so you know that they are of some quality. My Giant Cypress came with a SunTour crankset and I've never had a problem with it in over 2,000 miles on that bike.

As for the tooth sizes, that is a matter of deciding if you want a crankset that will be a bit faster then the other.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Daily
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#23
How am I supposed to know what crank my chain is most compatible with? Which toothsizes go faster(the coyote has another same price option of 48/38/28)? Chains seem to be around £7 total at the cheap end on ebay. If you buy a new chain do you need one of those link extractor tools too?

The coyote looks as good but just without the brand name on. Steel is steel right? Plus it has a chain guard on and mine has a small piece missing so thats a bonus.

A tip a local mechanic gave me was to look out for the smaller cog on the chain rings. Some are proper flat and some have a more dish shape. Well mine has a dish shape to it. Do the ones above look suitable?
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#24
Well my current crank seems to have 42 teeth on biggest crank and 170mm arm(assuming you measure from central points of the connection points).

so I think the first posted coyote pic should be a similar replacement.
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#25
Pedals have 1/2 or 9/19 thread. If you have 1/2 thread you can drill crank and cut new thread. In this case you will have to buy new pedals and ride with different pedals unless you convert another side too.
I guess you don't have tools for that job. If you buy new crank make sure pedal threads are the same or you will need to buy new ones.
I just checked Walmart website, they have new bikes for $59, but you don't have Walmart there?
http://www.walmart.com/ip/NEXT-Parowan-26-Men-s-Mountain-Bike/16318857
Unicycles need much less maintenance: Smile
http://www.walmart.com/ip/16-Unicycle/11065194
  Reply
#26
Only thing I wanted to say is about repairing threads on the crank!

Glue Cost = 20 pounds
Loss of Life or limb = PRICELESS!
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
  Reply
#27
Well Ive ordered the first coyote crank. The arm length and teeth match the one I have so Im hoping its a straightforward swap. But I suspect Ill hit problems as Ive never removed a crank before. Ive borrowed a bike toolkit which has all the tools including crank removal tools. So all Ive spent so far is £16 total for the crank. Ill be very happy if thats my total costs!

I did actually acquire some steel epoxy glue. Whilst researching jb weld I hit on a forum where a couple of posters mentioned an equivalent glue... from the £1 store! They claimed it was even stronger than jb weld after using it. Just by chance I managed to find it in my local £1 store. But Ill use the glue for other stuff now. I could never be confident with a glued pedal. They take such huge pressure.
  Reply
#28
You did well. Some things like accessories (that have no pressure or stress) is ok to use your jb glue on. Major parts I will say heck no to! No offense to anyone but that is one thing I do cherish, is personal safety. Giants are a pretty nice bike to put some money into Wink
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
  Reply
#29
Hi Zippy,

Did you get this crankset? I need to replace mine cause ive managed to strip the thread on the pedal! Looking at this crankset an wondering if its a " Buy cheap buy twice " Crank?
  Reply
#30
I bought a new road bike. I had it tuned/assembled at LBS. I rode the bike at max. 3 hrs. at various times--very short gentle spins. The right pedal came off twice. I then brought it to a different LBS shop after reading this blog. Sure enough it was the Rt. Crank Arm that has to be replaced.
The store from which I bought the bike agreed to send me another crank arm thru the manufacturer. I am pleased about this and waiting for the part.

However, I am now wondering about the labor expense of replacing the Rt. Arm Crank. Does anyone know?

In addition, I just had platform pedals on the bike. Eventually, I was going to switch to a Shimano PD 234 (?) Dual Purpose in the event I get into biking and want to buy the specialized shoes. Why I mention this, is that I read on the blog that the problem with the threading breaking down is due to the Alum. crank against the steel pedal. Thus, I am perplexed because I don't want the same thing to happen over again. This is a problem and costly. Please Help?
  Reply
#31
ok just gotta pipe up here because no one has mentioned the obvious thing,are you putting the pedals on the correct sides of the bike? the only time i have ever had a pedal fall off was because i had screwed the left pedal into the right side of the bike (think i was about 13 at the time).

as for using glues or bonding agents to hold pedals on ive got to agree with quite a few people here its a stupid and dangerous idea and your asking for trouble,i cant actually think of anywhere on my bike i would use glue apart from the rubber cement you use on punctures.

i changed the crank and bb along with a quite a lot of bits on my bike a few weeks ago,this is the crank i used http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_159276_langId_-1_categoryId_165545 just make sure you use some grease so if it ever needs replacing again its not too hard to remove.
ride until your wheels fall off
  Reply
#32
Quote:Why I mention this, is that I read on the blog that the problem with the threading breaking down is due to the Alum. crank against the steel pedal.

Cougar, if the pedals are screwed in correctly, you won't have any issues with either the crank or the pedals. Depending on the bike shop, the mechanic may not be very experienced and/or may always be in a hurry, thus overlooking simple things like making sure the pedal isn't cross threaded before he tightens it down. Since my crank arm was replaced, I have ridden the bike over 1,000 miles, including a charity ride that was 50 mile/day for two days through some of what we call our worst hilly countryside. I have yet to have had another problem with the crankset or the pedals. The LBS that replaced the crankset put the pedals in correctly.
HCFR Cycling Team
Ride Safe...Ride Hard...Ride Daily
  Reply
#33
yeah, same thing happen to me over a stupid mountain biking mistake zippy. I personally have had shimano cranks on my bikes. but i know most cranks anyways have warranties; call, sound pissed, and they cant refuse you (the manufacture).
  Reply
#34
(04-04-2011, 02:19 PM)DaveM Wrote:  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.


Any of you Pommies ever thought about the difference between putting a Helicoil in and JB Weld in something made out of two different types of metals??? Let me break it down for ya... JB would work fine for steel to steel, but in most cases, the crank arm is aluminum and the pedal shaft is steel.... therefore STILL making the weak point the crank. To answer your question Z, Get a Helicoil kit and just tap out the new thread size and pitch, insert the STEEL Helicoil, and then put the pedal back in the new STEEL threads. All a Helicoil is is an expansion of the original threads. It's not gonna be perfect, but I can gaurentee from experience that it'll work just fine as long as you don't try putting 1000lbs on it or something stupid.
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#35
There is a DYI. I just made one and seems to be working great as a temporary replacement (till the owner can afford a proper repair). This is also how I think pedals should be designed, using bolts, so you don't have to worry about stripped threads. I can't take all the credit though, I am pretty sure I remember my dad rigging up one of my bikes this way. He was very good at coming up with unusual ways to fix things.

Ok, so for what ever reason my picture wont attach or insert, so I made it my avatar. See to the left.
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#36
Cost = 6$ not including wrench. Lost the gyration of the pedal but not really that important. Find a bolt and nut the same size of the pedal thread and replace.
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#37
(04-03-2011, 11:51 AM)dave_sd Wrote:  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

That WILL NOT work. You have to replace the cranks. Tiagra cranks are pretty cheap. FSA makes some very good and cheap (Gossamer line) cranks. But it all depends on how the present cranks are attached. So first you have to recognize how the cranks are held on. Then buy something new or used off of Craigslist to match it. (for sale - bicycle parts).

The problem is that this guy appears not to be able to hire a mechanic to correct his problem and probably doesn't have the tools to replace it.
  Reply
#38
I have to admit that this thread has made me cringe more than once.
The general comments about bike quality and design are not at all accurate (yes, there have been some poorly designed/engineered made components and frames manufactured over the decades; but more of an exception than rule). The crankarm to pedal interface has essentially remained the same for a 100 years or more without any appreciable problems when dealing with the parts themselves and the stresses they are required to withstand. My only bad crank was steel and caused by improper installation by a previous owner. Never a bad alloy crank out of hundreds (majority having decades of use) I have worked on, and I regularly remove pedals on my daily road bike when transporting.
I have found after 50 years of messing around (riding, maintaining, repairing, modifying) with bikes that the threads on pedals and cranks work fine; EXCEPT when improperly installed (cross threaded, not sufficiently tighened), lack of maintenance (not verifying pedal tightness regularly), or damage (from an accident or shipping, etc.).

SAFETY FIRST!! DO NOT GLUE PEDALS ONTO CRANKARMS! I WOULD NOT RECOMMEND USING AN ALLOY CRANK WITH ANY THREAD DAMAGE! IT'S YOUR BLOOD THAT WILL SPILL!

Even with a steel crank I still have reservations (at least with my type of riding; I am not a leisurely casual rider), but there is a better possibility of re-tapping a steel crank if, and only if there are still undamaged threads that would adequately engage with the (50 % or more undamaged!) threads of the pedal. I have done this before and have 1000s of miles on that repair; but it was on an old English 3 speed that does not receive the stress I put on other bikes (that bike is now 55 yrs old and still going strong).
A pedal can be welded to a crank arm, but only a steel crank. The pedal still must be fully inserted into the crank hole and properly aligned. You cannot weld aluminium to steel except with special methods which are not applicable (nor cost effective) to situation.
I would never use a "helicoil" to repair a bad crank (alloy or steel); again it's your blood.

I respectfully request that members do no provide repair options that are dangerous to those asking for advice unless you have done it yourself and have adequately "field" tested the repair themselves under the most extreme use and for long duration. I have engineering, design, fabrication, assembly, breakdown, repair, and maintenance experience in an industrial (including "Milspec") environment. I will witnessed injuries and equipment failure from those "cutting corners" using unreliable means for repairs just to get something done cheaply and quickly. It has required a decade or more before I allowed myself to provide my fabrications/modifications to be used by another and even then only with full acknowledgement of any potential danger by those wanting to use my "fixes". Of course, I do not have (anymore) the means to do controlled testing under proper conditions and with the proper calibrated equipment required to provide quick feedback as to the efficacy of my designs, and thus much more time must be spent ensuring that my work was indeed reliable and of high quality.

Please folks, stop provided "bandade", "chewing gum", "duct tape", "coat hanger" repair recommendations which are often taken up with full confidence by those without proper knowledge, experience, tools, etc. unless you are willing to accept liability if something goes wrong.
Also, when dealing with "professionals" that you might bring your bike to, make sure by directly asking them if they have done that specific work before (e.g. widening the rear fork is a scary proposition if done by those without the proper know-how). Many shops are manned by those who have only limited experience, and often only with certain style bikes, newer bikes. I have yet to find a shop that can (or will) tear down an internally geared hub in the last 15 years; those that did are retired or dead and that knowledge has not been passed along to the younger generations. It is generally a pull it and replace mentality nowadays, both to conserve time and effort, but also to sell new parts.
Take care,
Jesper

"I am become Death, the destroyer of bicycles." NJS
  Reply
#39
(04-02-2011, 04:47 PM)dave_sd Wrote:  Take it to your local bike shop and see if they can drill it out and install a helicoil

That's a good idea that I wouldn't have thought of. I would have simply replaced the cranks. You can usually find extra left hand arms on Ebay or Craigslist but I have never seen just a drive side.

(04-02-2011, 05:45 PM)zippy Wrote:  thanks but that could be expensive. I wanted to know any DIY methods...cheap!

Because it's the drive side there are no "cheap" fixes. And I suspect you ruined the crank threads trying to turn it in in the incorrect direction. So the cheapest thing you could do is take it to a competent bike shop and take his advice when he has eyes on the problem. You probably don't have the proper tools to work on it anyway. You might get the good replacement crank off of Craigslist but you wouldn't know how to install it. And there are a dozen things you have to know and at least one special tool in any case.

Many shops will explain it to you.

(03-24-2024, 08:52 PM)Jesper Wrote:  I have to admit that this thread has made me cringe more than once.
The general comments about bike quality and design are not at all accurate (yes, there have been some poorly designed/engineered made components and frames manufactured over the decades; but more of an exception than rule). The crankarm to pedal interface has essentially remained the same for a 100 years or more without any appreciable problems when dealing with the parts themselves and the stresses they are required to withstand. My only bad crank was steel and caused by improper installation by a previous owner. Never a bad alloy crank out of hundreds (majority having decades of use) I have worked on, and I regularly remove pedals on my daily road bike when transporting.
I have found after 50 years of messing around (riding, maintaining, repairing, modifying) with bikes that the threads on pedals and cranks work fine; EXCEPT when improperly installed (cross threaded, not sufficiently tighened), lack of maintenance (not verifying pedal tightness regularly), or damage (from an accident or shipping, etc.).

SAFETY FIRST!! DO NOT GLUE PEDALS ONTO CRANKARMS! I WOULD NOT RECOMMEND USING AN ALLOY CRANK WITH ANY THREAD DAMAGE! IT'S YOUR BLOOD THAT WILL SPILL!

Even with a steel crank I still have reservations (at least with my type of riding; I am not a leisurely casual rider), but there is a better possibility of re-tapping a steel crank if, and only if there are still undamaged threads that would adequately engage with the (50 % or more undamaged!) threads of the pedal. I have done this before and have 1000s of miles on that repair; but it was on an old English 3 speed that does not receive the stress I put on other bikes (that bike is now 55 yrs old and still going strong).
A pedal can be welded to a crank arm, but only a steel crank. The pedal still must be fully inserted into the crank hole and properly aligned. You cannot weld aluminium to steel except with special methods which are not applicable (nor cost effective) to situation.
I would never use a "helicoil" to repair a bad crank (alloy or steel); again it's your blood.

I respectfully request that members do no provide repair options that are dangerous to those asking for advice unless you have done it yourself and have adequately "field" tested the repair themselves under the most extreme use and for long duration. I have engineering, design, fabrication, assembly, breakdown, repair, and maintenance experience in an industrial (including "Milspec") environment. I will witnessed injuries and equipment failure from those "cutting corners" using unreliable means for repairs just to get something done cheaply and quickly. It has required a decade or more before I allowed myself to provide my fabrications/modifications to be used by another and even then only with full acknowledgement of any potential danger by those wanting to use my "fixes". Of course, I do not have (anymore) the means to do controlled testing under proper conditions and with the proper calibrated equipment required to provide quick feedback as to the efficacy of my designs, and thus much more time must be spent ensuring that my work was indeed reliable and of high quality.

Please folks, stop provided "bandade", "chewing gum", "duct tape", "coat hanger" repair recommendations which are often taken up with full confidence by those without proper knowledge, experience, tools, etc. unless you are willing to accept liability if something goes wrong.
Also, when dealing with "professionals" that you might bring your bike to, make sure by directly asking them if they have done that specific work before (e.g. widening the rear fork is a scary proposition if done by those without the proper know-how). Many shops are manned by those who have only limited experience, and often only with certain style bikes, newer bikes. I have yet to find a shop that can (or will) tear down an internally geared hub in the last 15 years; those that did are retired or dead and that knowledge has not been passed along to the younger generations. It is generally a pull it and replace mentality nowadays, both to conserve time and effort, but also to sell new parts.

I agree. but that sort of damage suggests that our friend is not any sort o9f bike mechanic and cranks are dangerous for newbies to mess with.
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#40
(04-04-2024, 05:17 PM)Frankly Wrote:  I agree. but that sort of damage suggests that our friend is not any sort o9f bike mechanic and cranks are dangerous for newbies to mess with.

Exactly why some of the advice should never have been given; and why the owner should have been warned away from doing some of the ludicrous "repair" advice proffered. Sometimes a little common sense must prevail over a quick "fix" and cost savings over getting things done right.
Take care,
Jesper

"I am become Death, the destroyer of bicycles." NJS
  Reply


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