mrfizzed

greetings folks, i am new here and new (or new again after a 15 yr hiatus) to cycling. anyway i have a random question. i bought a bike (used) and it turns out the rt crank is stripped. i have a triple crankset (52/42/30) and found a crankset by same manurfacturer but it is a double ring (53/39). can i simply swap the double crankset for the triple. both are 172.5mm thanks in advance and i look forward to spending lots of time on here.

reptilezs

what cranks?

Dan Burkhart 

Welcome to the nut house.
What is it that's stripped? Is it the puller threads or the pedal threads?There are cures for both.
Doubles and triples use different length bb spindles to achieve proper chain line, so no, it won't be a straight up swap.
Shifter and derailleur should be alright though. That should just be a limit screw adjustment.

mrfizzed

they are tuvativ 172.5mm cranks (isoflow) and it is the rt side pedal thread (where the pedal screws in)

mrfizzed

i also found the same crankset brand new for $50, should i just replace entire crankset?

Dan Burkhart 

A well equipped bike shop should be able to but a Helicoil insert in the crank and make it as good as, or better than new.

Dan Burkhart 

If you are going to change cranksets, I'd spend a bit and upgrade. Don't want to disparage yer bike, but Isoflow aint great. Uses a Powerspline BB which is pretty much junk. This from personal experience, not hearsay.

operator

+1

Powerspline is junk, not from personal experirence or hearsay but from customer bringing their bikes back with BB's shot/stabbed/murdered in a very small amount of time.

I don't like helicoils, it's always a gamble. How do you ensure that it goes in 100% perpendicular to the crank face 100% of the time?

Dan Burkhart 

That is the main challenge for sure. I start by always removing the crank from the bike and doing the job in a vise.
I know there are some that do it on the bike, but I would not trust myself to get it straight.
From there, care and caution.

mrfizzed

i appreciate all the help. now if i were upgrading, what do you recomment? ie whats a 'better' crankset that isnt much more? i mean when i bought the bike i did not know i was replacing the crank at all, and even the $50 is a cost i did not expect/want to spend. anything close to $50 or in the $50-75 range thats "better"?

phantomcow2

You use the right tool for the job. I wouldn't trust most bike shops to do this, but helicoils are a very reliable solution if installed with the aid of a milling machine and either a dial indicator or set of pins. Any small machine shop should be able to install one.

phoebeisis

Since you want to save some $$ You might be able run a tap thru those threads and clean them up enough to make them functional.
Now my definition of functional is pretty broad. If there is so little threading left that it doesn't seem to have enough bite, you can try threading it in while gooped up with some metal epoxy like JB weld. The pedal and the crank will be permanently stuck together, but they are cheap parts, so who cares.

I hesitated to suggest this remedy, but... Even a helicoil done by the shop will cost $30 or so.Who wants to spend $30 on a $20 crankset? JB WELD is $5 and you probably will find other uses for it.

If you can't run a tap thru-no tap- just crank it in bad threads and all-gooped up with JB weld-sort of a ready made tap as it were. You should file the pedal threads a bit to clean them up, so you get it in straight. Screwed up threads can hold surprisingly tightly-especially when reinforced with JB weld.

You have nothing to lose but a cheap pedal, right?

Luck
Charlie