Accidentally stripped crankarm thread

AliShah2020

Regular
Hi all,

I recently purchased a brand new bike online which I put together myself.

I foolishly screwed the left hand pedal into the right hand crank arm and damaged the thread (in the crank arm) in the process. First shop I went to claimed it couldn't be repaired and that the bike needed to be scrapped! They then enviously looked at my bike and asked me where I bought it from. Needless to say I got a bad vibe. Quick check online and I found it can be remedied by a Helicoil which can repair the thread. Pretty straight forward job with cheap parts.

It seems many shops are taking advantage of newbie cyclists.

Can I please ask two questions:
1. What is your experience with repairing stripped threats in the crank arm. Is it worth doing? How much should such a repair cost?
2. I am having trouble understanding the names of the component parts and cost of replacement parts as I do not know how to find a replacement "like for like" chain set. Can someone please kindly help with tell me how much a replacement chain set should cost and share a link for what I need?

The bike is Lapierre Edge AM 727.
https://www.paulscycles.co.uk/1818/products/lapierre-edge-am-727-hardtail-mountain-bike-2019-blackyellow.aspx#infospec

I really appreciate your help and input.

Thank you.
 

Sharky

Guru
Location
Kent
£31.50 + VAT from
https://highpath.co.uk/crank-repairs-and-modifications/

Have had a couple of jobs done by them - very reliable.
Other than a satisfied customer, have no connection with them
 
Location
Loch side.
Hi all,

I recently purchased a brand new bike online which I put together myself.

I foolishly screwed the left hand pedal into the right hand crank arm and damaged the thread (in the crank arm) in the process. First shop I went to claimed it couldn't be repaired and that the bike needed to be scrapped! They then enviously looked at my bike and asked me where I bought it from. Needless to say I got a bad vibe. Quick check online and I found it can be remedied by a Helicoil which can repair the thread. Pretty straight forward job with cheap parts.

It seems many shops are taking advantage of newbie cyclists.

Can I please ask two questions:
1. What is your experience with repairing stripped threats in the crank arm. Is it worth doing? How much should such a repair cost?
2. I am having trouble understanding the names of the component parts and cost of replacement parts as I do not know how to find a replacement "like for like" chain set. Can someone please kindly help with tell me how much a replacement chain set should cost and share a link for what I need?

The bike is Lapierre Edge AM 727.
https://www.paulscycles.co.uk/1818/products/lapierre-edge-am-727-hardtail-mountain-bike-2019-blackyellow.aspx#infospec

I really appreciate your help and input.

Thank you.
I'd love to know how you managed to do that. How did you insert a LH thread enough into a RG threaded hole to strip it? Brute force?

Anyway, a stripped crank can be repaired. Special steel inserts are available to fix the damage. First the old hole has to be reamed out extremely squarely so that your pedal doesn't wobble when turning in the crank. This takes lots of skill. Then the new oversize hole has to be tapped with either a LH or RH tap, depending on which side the stripped crank belongs to. Then a special insert has to be screwed in and glued in place.

All this can easily take a skilled operator, with the right expensive tools and consumables, an hour.

How much is that worth to you?

Your bike has an unbranded crankset on there but any other Hollowtech-compatible crank for a single chainring would work. Youc an reuse your existing chainring.
 

neil_merseyside

Über Member
Location
Wirral
Chances are a local engineering shop will have helicoils and one of the lads will fix it for beer money. Covid hasn't stopped engineering companies from working, it can't be done from home, but finding one that will deal with you with the associated Covid risk may be a bit harder (though I doubt it).
 
OP
AliShah2020

AliShah2020

Regular
Hi Sharkie/Yellow Saddle/Gunk,

Thank you chaps for your help! :smile::okay:

:blush:Basically first time newbie build error. An expensive lesson learned!

Total repair cost using specialist machining engineers [https://highpath.co.uk] is circa £95 for both pedal arms (this includes petrol costs of driving a round trip of 92 miles from London to save time). I am wondering if it is wiser to replace? Is a repaired pedal arm weaker or as good as a new arm?

Few more questions:
1. Can I please ask, do I need a "crank set" or can I buy just the RH crank arm on it's own?

2. My spec according to the bike manufacturer page is LP 2PC 1 x 11 Narrow Wide 32T. I have Shimano XT 1x11-speed derailleurs (I don't know what any of this means).

Could you please point me in the right direction by sharing a link to a good durable replacement? I think from this message thread this is what I need? https://www.plushhillcycles.co.uk/7168/products/shimano-xt-m8000-175mm-crankset.aspx ?

Below is a photo I just took of the RH pedal arm for reference.

1587924914807.png

1587925977820.png


Thanks for your help. :smile::notworthy:

P.S Apologies if I am asking a lot of questions, I have spent two days online looking for answers and I am a complete newbie and my children are upset thinking the bike is going to be an expensive to fix. Sometimes when you have hit a dead end, asking is the most straight forward. :rose:
 
OP
AliShah2020

AliShah2020

Regular
You could try screwing a pedal in from the wrong side to see if that corrects the problem enough to get the pedal in from the correct side. Gently does it to get the pedal started to make sure you have the correct pedal turning in the right direction.
Hi Boyd,

The first rookie mistake I made was screwing the left hand pedal into the right hand crank arm. Perhaps the second rookie mistake I made was unscrewing them both, and then screwing them the right way round.

My left pedal is fine, but unfortunately when I went out for a ride I noticed the right pedal has moved a few degrees. It is now at a slight angle and I am scared of causing more damage as I suspect this will degrade and get worse very quickly.

I have two options: repaired properly with a Helicoil or replaced. It seems I cannot purchase just the peddle arm by itself but have to purchase a damn whole new crank set. This is really upsetting as bike is only 24 hours old.

I don't know how to replace with the correct crank set, as it seems complicated. I have had a look but it's confusing to a newbie. Based on the posted specs can you help?
 

Gunk

Veteran
Location
Oxford
Try this ^^^ first, it may re-tap the thread

I don’t know what that crankset is, it looks like their own brand.
 

rogerzilla

Legendary Member
A 9/16" pedal tap (I only say the size because 1/2" is prevalent on steel one-piece cranksets) fixes many such problems. It depends how bad it is. Otherwise, a new crank arm is probably the most cost-effective option.
 
OP
AliShah2020

AliShah2020

Regular
A 9/16" pedal tap (I only say the size because 1/2" is prevalent on steel one-piece cranksets) fixes many such problems. It depends how bad it is. Otherwise, a new crank arm is probably the most cost-effective option.
Thank you Roger, I almost fell victim to a number of local unscrupulous bike shops. My initially logical thought was I should be able to buy a RH crank arm or crank arm set, and I was told "No you have to buy a chain set for £300." My intuition told me I was being misled.

Thank you everyone for your help.
 

Drago

Flouncing Nobber
Location
Poshshire
Just be aware that since Dave Wrath-Sharman died Highpath have not been doing much work at all (he was 50% of their machinists, and easily the most talented). Chris Bell also died a few years ago, leaving them a one man band and their website hopelessly out of date.

From what I hear they are still operating but their turnaround time is measured in months at the moment. If you're wanting to get out on your new bike then a replacement crank might be the best way forward, unless you're up to the job of helicoiling it yourself.
 
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Location
Loch side.
Thank you Roger, I almost fell victim to a number of local unscrupulous bike shops. My initially logical thought was I should be able to buy a RH crank arm or crank arm set, and I was told "No you have to buy a chain set for £300." My intuition told me I was being misled.

Thank you everyone for your help.
Sometimes you can get a direct replacement left crank. Never right crank only. A tap only works if no metal was lost in the botch up. It cannot replace material, only clean up the threads. We still havent seen a photo of the damage, therefore it is only speculation.
 
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OP
AliShah2020

AliShah2020

Regular
Just be aware that since Dave Wrath-Sharman died Highpath have not been doing much work at all (he was 50% of their machinists, and easily the most talented). Chris Bell also died a few years ago, leaving them a one man band and their website hopelessly out of date.

From what I hear they are still operating but their turnaround time is measured in months at the moment. If you're wanting to get out on your new bike then a replacement crank might be the best way forward, unless you're up to the job of helicoiling it yourself.
Hi Drago,

You are correct. They are fully booked for 3 weeks. Repair is not an option then, will look for replacement crank arms.
 
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