Vintage touring bike bottom bracket/chainwheel replacement

I've got a 30yo 10 speed touring bike that I still use for my daily commute. There are no problems getting spare parts for rear cogs, derailleur cogs (shimano friction shifters), chains, wires, etc, but by now I have almost worn out the smaller cog in front (teeth are less than half as thick as they used to be after tens of thousand k's and they are STEEL). Crank is the old one-piece forged steel number with two cogs, I believe the cogs may have been made by Simplex.

What are my choices if I want to continue using the old clunker?
1. New crank (will the bearings fit)?
2. New cogwheel (highly unlikely)?
3. Something else?

Or should I just use it till the cogs start breaking off (shouldn't be long now), then junk it?

I might have a suggestion if I could see the crank (a picture is worth a thousand words?) maybe you can post one or find a link to something very similar?

How readily you can replace the BB & crank depend on who made the frame AND when it was actually made.

The chainrings on a one-piece crank can be changed. Did you simply want to replace the chainring(s) if that were an option OR did you actually want to change the crankset & BB?

How much are you willing to spend?

As suggested, post a picture of your bike -- your budget & how capable you are of working on your bike, yourself, may be the only limiting factors.

Will post some pics ASAP.

Budget is low as bike isn't worth many cents but I can do the job myself so might be worth it. It's a Crescent, built in Sweden, very good quality but heavy as a tank.

Picture added of a near identical bike. (different colour)

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Sorry I don't know about that one-peice crank specifically, but often the recycling center or donation center will be rife with similar bikes. check the chainwheel and spin the crank to see that they are in usable condition, buy the whole bike for whatever they are asking then donate or recycle the rest back. it could be that you can use just the crank or you might need the bb as well.

if replacing this bike is within your budget then here are some other thoughts:

saddle is pushed very far forward on this bike
handlebars are very high
the fit of this bike (to the rider) is not ideal
the bike must weigh a ton
cost of periodic maintenance when needed: wheel & headset bearings, brake pads, tires could be put toward a better fitting better riding bike

there should be many 'little used' hybrid bicycles available 2nd hand that would fit better and weigh a lot less... the hybrid would likely have an straight bar, higher bar position, slightly wider tire, aluminum rims, better braking and although the weight difference may not be HUGE, it would 'ride' a lot lighter (more responsive, acccelerate easier)

best of luck,

*perhaps someone more familiar with that crankset and can offer more detail about its possible replacement

The crank in the picture uses what is commonly referred to as an "American" BB -- also known more correctly as an ASHTABULA BB.

The Ashtabula BB shell is oversized compared with bikes which don't use an American BB.

An adapter which sleeves into the Ashtabula BB shell is available which will allow you to use a "standard" English BB -- the price varies between $20-to-$30, depending on where you buy it from.

You can buy a 110BCD "spider" which will fit on your bike's current crankarm + an individual chainring of your choice from any shop that sells BMX "stuff" ... or, go to WWW.DANSCOMP.COM to see what is generally available in the BMX world.

Most BMX shops will also have individual chainwheels which will fit on your crankarm -- you will recognize the chainwheel because it will have a hole in the middle (for the axle) + a registration hole which the crank arm keys into.

Now, the fact that you either may not have paid much for your bike or your bike is old doesn't mean that it isn't worth spending money on it because whatever you put on it can be used on another bike in the future ...

Basically, only your budget and desire will limit you from updating components on the bike.

BTW. If you are moderately handy AND ambitious, you can replace the chainwheel, yourself.

I don't know what size bearings an American BB uses ...

The disassembly is pretty straight forward ... remove the pedal on the left side of the bike (I presume it has a left hand thread) ... remove the lockring on the non-drive side (bike tools are "needed" but I suppose a large pipe wrench could be used, but it would mar the edge ... remove the cup (again, a bike specific tool OR a large adjustable wrench if the outer surface has a raised 'hex' surface) ... snake the crankarm out of the BB shell ... replace the chainwheel ... clean and/or replace the bearings & repack with fresh grease ... reassemble.

You may have to remove the driveside cup in order to remove the crankarm ... I can't recall, but I'm currently under the impression tht it has to be removed, too.

RE: one piece/ashtabula crank removal

after removing the pedal, remove the lockring, it is likely reverse thread, a large adjustable wrench usually works, remove any washer, spacer
remove the cone, also likely reverse thread, a straight blade screwdriver will be able to tap it around to loosen and remove, there is also a pin tool designed to do this job
next remove the ball bearing retainer, looks like a little cage holding the bearings
then the crank can come out from the other side and pass thru the frame.
the ball retainer on the other side should come out with the crank, if it doesnt you may need to pull it out along with the crank to get the bend in the crank to pass thru the frame smoothly.

then the cups can be tapped out of the bottom bracket shell if necessary

Thanks guys,

That provided a few good ideas (especially "alfeng"). I'll have a good look at the "spider" path when the chainring finally gives up or gets too bad. Yes, it weighs a ton, that is over 20KG! The solid frame, steel crank, stainless steel equipment, etc all add to the weight, but it's a bit of nostalgia at the same time (and pushing all that weight up the hills makes me STRONG )

P.S. It has two chainwheels (2 x 5 = 10 gears) so will have to get 2 of them bolted together onto the spider but it should work fine. The chainwheels won't transplant directly since the current chainwheels have 6 bolts holding them (as opposed to 4 or 5)

R)ger