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How come the cranks are not reverse threaded?(14 posts)

How come the cranks are not reverse threaded?chazman
Oct 12, 2002 6:06 PM
Just wondering why the industry decided to reverse thread the left pedal instead of the left crank? Especially on mountain bikes where pedals are two sided. I've seen people almost get really hurt when they put the pedals on the wrong side and they backed out. I've never seen someone able to put the cranks on the wrong side and be able to ride the thing. If the cranks were differentially threaded then both pedals could be the same (mountain of course).
DUH, they are....C-40
Oct 13, 2002 5:15 AM
I guess you don't understand threading. The pedal with left-hand external threads will only screw into a matching left-hand internal threaded crankarm. You can't accidentally screw a pedal into the wrong side of the crank.

If you've seen a pedal come off, it was caused from a failure to tighten properly.
What the heck are you talking about?Kerry Irons
Oct 13, 2002 7:03 AM
Right pedals are right hand threaded, left pedals are left threaded. Are you somehow suggesting they should be reversed from that? They are threaded the way they are to minimize the precession effect, which would tend to make the left pedal unthread if it was right hand threaded. Any pedal that comes out during riding was NOT properly installed. Simple as that. Full stop.
You must live in the southern hemisphere (nm).the other Tim
Oct 13, 2002 8:12 AM
Originally done that way for track bikes...terzo rene
Oct 13, 2002 1:52 PM
so that if the pedals seized up and stopped rotating the pedals would come off instead of your legs. Unfortunately the design was never changed and we now have to use monster pedal wrenches to tighten them enough to prevent loosening.
Originally done that way to keep the left pedal from unscrewingthe other Tim
Oct 13, 2002 3:57 PM
due to precession. The design was never changed because left pedals are still in use. Monster pedal wrenches are for pedal removal; you can use a hex key to tighten.
Correct, if bearings seize, pedals loosen.Chen2
Oct 14, 2002 2:31 PM
Riding does not cause pedals to tighten.
half correct ...the other Tim
Oct 14, 2002 4:08 PM
While a pedal with seized bearings will unscrew itself with the current threading scheme, the
b reason
for using l-h threads on the left pedal is to keep the pedal from unscrewing when the bearings are
b not seized
(the condition preferred by cyclists, 2 to 1). The same phenomenon (precession), that would make a left pedal unscrew itself if r-h threads were used, causes pedal threads (current scheme) to tighten with use.
MTB pedals.Matno
Oct 13, 2002 2:44 PM
If both pedals were the same, you'd have to put one of your cleats on backwards. Just out of curiousity, where are you from? Not many Chaz's out there...
Let me clarify (I'm not tarded)chazman
Oct 13, 2002 3:43 PM
Thanks for the colorful responses. I guess I should have been more clear about my question. Many of the MTB prototype pedals I have seen are symmetric (i.e., there is no front or back of the pedal). This simplifies the claw design and allows symmetric release so you can twist your shoe in or out to release. I see road as going this route also (speedplay etc). If these pedals ever go into production then there will be a ton of people that screw them into the wrong crank, and yes, if you do this your pedal can back out on you. The only way to prevent this is to thread both pedals the same way and reverse thread the left crank.

Oh, and for those that are curious, I live in LA. That would explain a lot about me but not the fact that I am stupid. I blame that on Soy products.
I've never seenMatno
Oct 13, 2002 4:09 PM
a person who could fully thread a pedal onto the wrong side. It would take a lot of pressure to torque a right-threaded pedal into a left-threaded crank (or vice versa). On the other hand, if pedals were threaded differently, they WOULD be able to unscrew from riding. The simple (and existing) solution to the problem you suggest is a little "L" and "R" on the pedals. Far as I know, most pedals come with such a label. You just have to look for it.
Usually there's other markings too.Spoke Wrench
Oct 14, 2002 4:42 AM
As a general rule, fasteners with a left hand thread will often have a serration machined into it to distinguish it from a right threaded counterpart. The majority of pedals (but not all) have these markings.

Pedals WILL come loose if used on the wrong side of a bike. Most tandems use a cross over drive so the captain's crank has a chainring only on the left side. If you try to use an ordinary crankset backwards, you will have to take some additional measures to keep the pedals from unscrewing themselves.

It IS possible to completely screw pedals into the wrong side of a crankset. I've seen it done. I think Grzy Mnky said it best, some people shouldn't be allowed near tools.
Let me clarify (I'm not tarded)DieselDan
Oct 13, 2002 9:44 PM
The pedal that goes on the left has a uppercase "L" stamped on the shaft near the threads, and an "R" is stamped in the same place on the right pedal. Still, you cannot install them backwards successfully. Force the right pedal into the left crank, and you seriously strip the threads out of the cramkarm enough you'll have to replace it. I do think you should leave complicated procedures to the professionals.
Maybe it would help if ...the other Tim
Oct 13, 2002 10:23 PM
bicycle manufacturers stamped R and L on the sides of the bike where the R and L pedals belong.

WRT "I'm not tarded." At this point, I think you have the burden of proof.