i RIDE

Well, I found a deal a few months back for a used crankset. When I bought it, I checked the threads and everything and they seemed perfectly fine and the guy selling seemed trust worthy enough. Finally I got started with my build and tried putting my new pedals on and the drive side gets impossible to thread, halfway in by hand. Pedals are brand new, threads are all good so Im guessing the crank threads are stripped; but would torquing the pedal with a wrench risk ruining the new pedal threads? I should be able to thread the pedal most of the way by hand correct (left side does just fine)? I still can't see any problems with the crank threads...

Won't be too sad if I need new cranks (wern't too hard on the pocket), but will be more sad if I ruin my pedals in the process.

Thanks for the help!

IthaDan 

if it's getting in more than a couple turns before you feel resistance, I'd say there's just gunk in the crankarm's thread or on the pedal threads- use a wrench. If you're still leery, clean of the pedal threads with a wire brush and the threads in the crankarm by threading in something shaped like a bottle brush (automotive battery terminal cleaners work well). I can't hand tighten most of my pedals all the way to the hilt.

As a rule of thumb, if it just barely bites, like before you can get a turn or two, the thread's wrong and the pitch is starting to interfere.

gmt13

Are you sure the threads are compatible? There should be markings on both the crank and pedal flat to indicate whether the threads are English, Italian, French, etc. Pretty much everybody uses 9/16" x 20 tpi, but some components may be French (14 mm x 1.25). I have heard that there may be slight differences in thread design even among the 9/16 x 20. If you verify compatibility, you should then have the crank threads chased with the proper tap. It is my understanding that French threads can be retapped to 9/16 x 20.

It does sound like the non-drive side was fine so that is a good sign. What you may want to try is threading the pedal on from the back side. This just may clean up the burr or grit or whatever.

-G

FBinNY 

This is classic for cross threading. If you stop now you can save the crank, but if you continue kiss it good bye.

Remove the pedal, get a pedal tap, and lead it in carefully from the opposite side. the tap will take the lead from the remaining good threads, and clean up the damaged ones. Nothing will restore the damaged area, but if it's only a few threads it'll be OK. Once you've cleaned it up you can carefully thread in the pedal.

Of course it might just be dirt in in the thread someplace, but you'll never go wrong, by backing out and inspecting, If in doubt use the tap.

i RIDE

Yeah, checked the compatibility and it all works together. It looks a little dirty, so I will give it a good clean tomorrow. If that fails, I will thread the opposite side, or go look for a pedal tap. Thanks for the help!

bikeman732

One of the first lessons I learned as a bicycle mechanic is "Never force it in". If it isnt going easily something is not right. find out what is stopping progress and remedy the problem. Forcing only leads to ruined part!

i RIDE

Definitely, I just wasn't sure if doing it by hand was sufficient, and I used poor words for that. Im will probably take it to my lbs to get it pedal tapped, because I did not realize how expensive they were.

c0urt

+1
if you are forcing it you are doing it wrong it basically

Airburst

It's a bad idea to do it, but it probably won't do the pedal thread any harm. Pedal spindles are generally steel, and tend to be hardened since they have a bearing race on them. Crank arms are aluminium alloy, which is softer than mild steel, let alone hardened steel.

dsbrantjr

"Im will probably take it to my lbs to get it pedal tapped"

Because it is the right crank with the more common right-hand thread a machine shop might have the correct 9/16-20 tap as well.

But by all means try threading it in from the back side. After you clear the threads by whatever method don't forget to grease them to help prevent them seizing due to electrolytic corrosion of the dissimilar metals; I use Tef-Gel.

dsbrantjr

Worst case, if the threads are completely ruined, which doesn't sound likely in this case, they can be economically drilled and tapped oversize and a Helicoil insert installed which will restore the threads stronger than the original ones.

FBinNY 

Yes, a machine shop might own a 9/16x20 tap, but it's a rare size, so it isn't likely. OTOH a bike shop is sure to have the tap, and most likely be willing to do this simple job for far less than a machine shop would.

onespeedbiker

You probably should have added that although the pedals would be fine, the crank arm threads would likely be destroyed and probably need to be helicoiled.

onespeedbiker

There are exceptions to this rule however one being the threading of BSC pedals onto Italian cranks. The threads are the same 9/16" with only a different thread profile. The pedals will start to thread and then tighten up but with some additional force the pedals will thread on (changing the profile in the process). So as long as one knows the cause, a little force is okay.

fietsbob

Use a pedal tap and chase the threads in the crank arm. Don't have one?, your LBS will, .. go there.

the 9/16-20 LH tap is pretty unique to bicycles.

Airburst

I agree, I probably should have. Don't force pedals into cranks if the threads are dodgy, but don't throw the pedals out if you have done.

FBinNY 

This is a good point. The real problem isn't a tight thread, but one which ramps up getting tighter as you go farther. After a while you get a sense of what's likely happening simply by hand feel reading the amount of torque and the pattern of change.

i RIDE

Thanks for all the help! Tried cleaning it with a wire brush, didn't work so I took it to my LBS and it solved the problem with a tap! Kind of expensive ($10) thinking about what they actually did in front of me and screw in the tap then add a squirt of oil for a <5 minute job.

Airburst

Those taps aren't cheap - they have to offset the cost somehow, considering they probably don't need to use them all that often.

wheelreason

Spoken like a true roadie...

FBinNY 

As someone explained to me long ago in a different context. $1.00 for the time it took to help you. $99.00 for the capacity to do so.

bikeman732

This is exactly one of the reasons I got out of the bicycle business. Customer comes to you because they have an issue they can't fix due to lack of tools or knowledge, you fix the problem correctly and quickly, charge a small fee, and they say it is too much. There is no repairman or repair shop in any other industry I know that will fix anything for 10 bucks. In fact most charge more than that before they fix anything!

bikeman732

Those taps are relatively cheap compared to the cost of rent, insurance, payroll, utilities, advertising etc.!

FBinNY 

Whenever I see a consumer criticize a dealer or mechanic, for service charges, I'm tempted to ask what they do for a living, and how much of their time the same dollars would buy.

When I was in retail, I used to ask, and a good majority of those who most objected to our labor charges tended to be professionals, doctors, lawyers, and wall streeters. Some insisted the situation wasn't comparable, but most got the point.

i RIDE

Hey, I wasn't really complaining or trying to criticize the mech. I was happy to pay him for his help and friendliness; I know they have to make a living too. Working full time while being at uni (fyi); so yeah money is something I'd rather save. I was more thinking along the lines of perhaps I could of bought my own tap at $15 per tap and used it in the future; as Im starting to do a lot of my own bike work. Anyways sorry if I offended any of you, I'll think of that in the future.