Here we go again

bompington

This pedal has covered >2000k without any problems.
Then, this morning - thankfully less than a mile from work - it goes wobbly. As I pedal the last few metres one-legged, I unclip - and the pedal falls off.
So I assume I must have cross-threaded it, and not for the first time - hence the title - it just seems strange that it was fine for so long but then failed so catastrophically.

Well that'll have to be a new crankset I guess: the question I have though, is how to make sure I don't cross-thread it again? I thought I was taking a lot of care not to...

fat daddy

bompington wrote:

how to make sure I don't cross-thread it again? I thought I was taking a lot of care not to...

unless you have mega strong fingers, surely just using fingers to do the pedal up, with stop it from cross threading.

so clean the threads to make sure they are debris free, little smear of your choice of what ever you feel the need to put on your pedals .. anti-seize - grease - locktite - pledge ?? .. then do up with fingers only until the end of the thread, then finish with the tools.

Still .. perfect day for it to break ... good deal on cranks today .. UPGRADE TIME !!!!!

mugensi

Simply remember when fitting pedals that they turn towards the rear of the bike when tightening and towards the front when loosening. You should be able to screw them in fully by hand and only use a spanner to nip them tight at the end.

fenix

Dude that bike looks minging. When was it last washed ?

And yeah just screw it in by hand - you can't go wrong. I always turn it the opposite way until I feel the click and then reverse direction and it goes right in.

bompington

Fenix wrote:

Dude that bike looks minging. When was it last washed ?

And yeah just screw it in by hand - you can't go wrong. I always turn it the opposite way until I feel the click and then reverse direction and it goes right in.

Are you supposed to wash them?

Actually, I don't know what you're complaining about - I've already washed that bike this month! Salty and muddy roads, together with muddy forest dog-walks, mean that it only takes a couple of days to get like that.

But seriously, thanks for the advice - except that this is exactly what I have always done: but I have now had to deal with three stripped crank threads in the last 5 years. That would suggest I'm doing something wrong, but I can't for the life of me think what.

dodgy

MugenSi wrote:

Simply remember when fitting pedals that they turn towards the rear of the bike when tightening and towards the front when loosening. You should be able to screw them in fully by hand and only use a spanner to nip them tight at the end.

Open to misinterpretation, I think (and it looks like you have it the wrong way around?)

Clockwise to tighten on drive side, anti-clockwise on non drive side.

keef66

dodgy wrote:

MugenSi wrote:

Simply remember when fitting pedals that they turn towards the rear of the bike when tightening and towards the front when loosening. You should be able to screw them in fully by hand and only use a spanner to nip them tight at the end.

Open to misinterpretation, I think (and it looks like you have it the wrong way around?)

Clockwise to tighten on drive side, anti-clockwise on non drive side.

I was thinking the same. I think of turning them towards the back of the bike to remove them. (And English threaded BB cups the opposite).

I remember finding my son standing on the pedal spanner trying to remove the second cheap plastic pedal from his brand new Felt. He'd completely mashed the spanner before I pointed out he was trying to turn it the wrong way.

I've never cross-threaded a pedal. I always fit them with a generous dollop of copperslip and do the first few threads by hand to make sure they're not binding. Never had one come loose, or indeed seize either.

Maybe yours are coming loose and destroying the thread as you ride? Three in 5 years is pretty good going though... What cranks were they?

bompington

keef66 wrote:

Maybe yours are coming loose and destroying the thread as you ride? Three in 5 years is pretty good going though... What cranks were they?

I am, of course, devastatingly strong. Or powerful. Or something like that*, so it's natural that I would be grinding my bike's components into fine powder by sheer magnificence.
In order, the cranks were
1. some cheap square taper thingy
2. Rival
3. Force (which is why the latest is more of an ouch...)



*strength and power? That is the same thing, right? :twisted:

fenix

Salty roads and bikes arent a good mix - I have to clean mine straight after - but I dont commute...

Never broken a pedal like that - I think we have to chalk it up to your awesome power.

keef66

bompington wrote:

*strength and power? That is the same thing, right? :twisted:

Is that what you meant by Here we go again...?

arlowood

For correct pedal fitting I use the technique I spotted when a bike shop mechanic was setting up a bike for me to test ride many moons ago.

Offer up pedal to crank arm then gently rotate crank arm backwards to engage thread using the pedal as a "handle". Once thread is engaged correctly just spin the crank backward more quickly until its tight using that method then nip up with appropriate spanner. Also I always apply a liberal coat of copper-slip grease or similar to the pedal threads before assembly..

Never has a pedal come loose or mangle the crank arm threads in over 40 years of cycling.

lesfirth

You would have to be brain dead to screw a pedal all the way in cross threaded without realising that something was wrong.
I think it is more likely that it has come loose and damaged the thread while you were riding.

bompington

lesfirth wrote:

You would have to be brain dead to screw a pedal all the way in cross threaded without realising that something was wrong.
I think it is more likely that it has come loose and damaged the thread while you were riding.

Well, you should never rule out the possibility...

No, I'm genuinely mystified here. I've ordered replacements (by golly, a lot of fake sale prices around today...) for crankset and pedals, and I guess I'll just be putting them together even carefullier than the last time, when I was carefuller than the time before...

ugo.santalucia

No offence,

but you seem the kind of mechanic that would be better off taking his bike to the local shop...

How can you possibly cross thread a pedal? And that's the right one which is a standard thread...

fat daddy

it may not have been cross threaded .. infact it doesn't sound like it was

googling stripped pedals would seem to point to pedals becoming loose and slowly boring their way through the threads as people don't notice they are loose.

the answer seems to point to - don't use anti-seize, just use grease, you don't want you pedals becoming loose.

bbrap

Could you repair the existing crank with a helicoil type insert? I know you have ordered a new set but could be worth fixing the old one for when you bugger up the new one :P

keef66

bbrap wrote:

Could you repair the existing crank with a helicoil type insert? I know you have ordered a new set but could be worth fixing the old one for when you bugger up the new one :P

I'm sure that's possible. A Helicoil repair would probably be stronger than the original alloy thread. Assuming the alloy insert is still firmly bonded in the carbon crank that is...

Moonbiker

My LBS helicoiled when this happend to me to, the cost was around £20 i think.

I had borrowed someones elses bike & was mashing the pedals until one few off. :roll:

I think your problem (as this is happening alot) is being a weakling, so you aren't torquing the pedal up enough newton metres, so its working loose.

Parktool says 307 in-lb minimum

34.68634 Newton-Meter (N∙m)

bompington

Moonbiker wrote:

34.68634 Newton-Meter (N∙m)

Approximately...

keezx

bompington wrote:

But seriously, thanks for the advice - except that this is exactly what I have always done: but I have now had to deal with three stripped crank threads in the last 5 years. That would suggest I'm doing something wrong,

I'm sure you're doing something wrong.
I never stripped 1 crank thread in 50 years.

cycleclinic

The crank is very repairable a good LBS will be abe to do it. I use the Cyclus kit in my shop. There is a helicoil kit as well. It's a dodle really.

Also stop having a go at the OP. He is not the first and wont be last time this happens. Also in 50 years of cycling you must have mucked something up. Come on tell us so we can have a laugh.

veronese68

It's definitely too much power, that's what I'd tell myself anyway. ;-)
The only time I've had a pedal come off was because I hadn't tightened it up enough. I'd not done it up very tight as I knew I'd be swapping back the next day. But the pedal had worked it's way out at least half way before coming off so half the thread was ok. I screwed the pedal in from the back of the crank to clean up the thread and managed to refit it. That was about 6 years ago on my pub hack, still holding up but it doesn't do many miles.
This makes me wonder if the pedal is a tiny bit loose and so moving very slightly in the crank and wearing it over time. Not sure how you'd do it three times though. Other theory (completely without basis) is that salt and water are creeping in and doing the damage over time. Not sure how. The way to prevent this would be too grease the thread before you fit the pedals. But then would you have to reapply every year or so? Taking the pedal off and refitting would be more likely to damage something.
I'd say get it helicoiled, refit the pedal carefully with copper grease on the threads. Then be paranoid and check the pedal is tight every month or so.

ugo.santalucia

Moonbiker wrote:

My LBS helicoiled when this happend to me to, the cost was around £20 i think.

I had borrowed someones elses bike & was mashing the pedals until one few off. :roll:

I think your problem (as this is happening alot) is being a weakling, so you aren't torquing the pedal up enough newton metres, so its working loose.

Parktool says 307 in-lb minimum

34.68634 Newton-Meter (N∙m)

Never torqued a pedal. The all point of having opposite threads is that they tighten rather than loosen as you pedal, unless you pedal backwards obviously

lesfirth

Moonbiker wrote:

My LBS helicoiled when this happend to me to, the cost was around £20 i think.

I had borrowed someones elses bike & was mashing the pedals until one few off. :roll:

I think your problem (as this is happening alot) is being a weakling, so you aren't torquing the pedal up enough newton metres, so its working loose.

Parktool says 307 in-lb minimum

34.68634 Newton-Meter (N∙m)

I know I am old but I do try to understand what younger generations are talking about. However, try as I may, "mashing the pedals until one flew off" is beyond me. Can some one explain please?

Shimano recommend 35 to 55 NM . That is quite a lot. We will now get lots of posts from people saying they just nip their pedals up and have never had a problem. I think it is best to follow Shimano's advice .

ugo.santalucia

lesfirth wrote:

I think it is best to follow Shimano's advice .

Shimano advice refers to Shimano pedals on Shimano cranks of the same series... Shimano also advise to torque a cassette lockring about 40 Nm... but that works well with their steel and titanium freehubs. Most other freehubs are aluminium and if you torque the lockring at 40 nm, most likely you strip the threads... I have seen it happening.

Shimano advice is good advice if you take it to the letter, if you ignore the context, then it is bad advice (how many use Dura Ace pedals on Dura Ace cranks or XT pedals on XT cranks?). I prefer to go with my own experience and IME there is no need whatsoever to torque pedals at over 30 Nm or cassette lockrings at 40 Nm

veronese68

ugo.santalucia wrote:

Never torqued a pedal. The all point of having opposite threads is that they tighten rather than loosen as you pedal, unless you pedal backwards obviously

That was the logic I used when I didn't put my pedals on very tight. When one fell off I thought it must be flawed logic.

bbrap

I'm another who has never used a torque wrench on pedals. I put the pedal on with the merest hint of grease and wind on with my fingers until it stops. Then using a pedal spanner set at about 45 degrees to the crank I squeeze the spanner and crank together using just one hand. Never had one come loose and never had trouble removing one either.

bompington

Starting to think that the problem might have been that it wasn't tight enough and worked loose - I have had trouble with seized pedals before, so whenever I've put pedals on recently I've used plenty of grease and not overdone the tightening. So I guess underdoing the tightening must be it.
New crankset and pedals now on their way as they were getting on a bit, I'll consider the helicoil thing & reconditioning for next time.

Oh, and a special prize to keezx for the least helpful post of the thread.

prawny

I had this happen on a bike I sold to a mate. It was find for me for 1000s of miles but suddenly died with the same pedals. They were SRAM cranks too. I sniff a theme.

No issues with shimano cranks (touch wood)

AK_jnr

I dont torque mine. I use grease but sometimes have a right job getting them back off.

ugo.santalucia

prawny wrote:

I had this happen on a bike I sold to a mate. It was find for me for 1000s of miles but suddenly died with the same pedals. They were SRAM cranks too. I sniff a theme.

No issues with shimano cranks (touch wood)

Buy Sram, buy twice...