wcometh

Hi,

So. I dug my bike out of my garage and found that the crank screw to the bottom bracket was bad an the crank fell off. So I was able to get a local bike shop to pop the crank of the bottom bracket (yeah, they are nice folk!), and they said "why waste $150 to repair a $100 bike" ($70 for both crank arms and new BB spindle + labor) ..."you can get parts and do it yourself". And with the lock-downs things are very slow in the shop. Oh, BTW, they did clean andd lube parts, adjust brakes, for a very nominal fee, so the bike is in good condition.

This bottom bracket spindle is an old model type (or should I say cheap?). Picture is attached. It says Neco CR-VB 3L. I found out that 3L means a length of 116mm, 32 mm on the left and right side sections, and the middle is 52 mm and it is Asian style or so. (India uses the exact same measurements; and Vintage Sugino Maxi Bottom Bracket from England??)

THE IMAGE IN RED BACKGROUND IS A REPLACEMENT ONE I FOUND -- BUT I AM NOT SURE OF PULLING THE "TRIGGER" SO TO SAY, until I get some second opinions. I would like this to be a one-shot thing and not stretch it to a CVS-like rolling bill of small items.

1. The bike is a dirt bike-type (at least >10 years) with gears - 3 in front, 6 back. So the one crank arm has to have the gear "thingies" (!) for the bike chain, and those individual plates are riveted on there.

2. I can find a few sites with replacements but the measurements of the sections are not put except the full length.
Question: What would be the "common name" for the BB spindle ?
Question: And can anyone point to a couple of good places that I can get this part without having to panic??

2. I am thinking of an "upgrade" to the spindle and crank arms. Like I said I need to accommodate the gear sprockets on the one crank arm.
Question: Can I upgrade easily? What type can I upgrade to?
Question: Will this be straight forward and =do I need adapters?/

Many thanks for the reading this. Your help is greatly appreciated and comments welcome!

PS: I'm having trouble posting pics !! noob restrictions.

dedhed

See above.

The crank arm fell off. This usually means the tapered fit to the spindle is compromised and a new crank is usually the best option as the old arm will continue to loosen up when ridden.

Because the crankset chosen determines what length BB spindle you need. you get the BB that the crank requires. This is important so it clears the frame and allows the front derailleur to reach all the chainrings.
You're looking for a cheaper 6/7/8 speed triple crankset. Something like a Shimano Tourney or Acera
https://www.treefortbikes.com/Shiman...kset-28-38-48t

https://www.cambriabike.com/products...caAoNFEALw_wcB

Now the bottom bracket best bet is to drop a cartridge unit in and be done. Something like a Shimano UN26 or UN55. This requires knowing your frame BB shell width. (likely 73mm or 68mm) and threading (likely BSA/English) and the spindle length the new crankset requires. Now these things require some special tools to install as does removing your old BB cups. The good news is that it appears at least one cup was removed and and that bodes well they are not rusted in place. These also have reverse threading on different sides so do some research on BB threading. Pedals may need a pedal wrench to remove and the Left side is also Left hand thread.
https://www.treefortbikes.com/Shiman...Bottom-Bracket

You're also going to find as you look for parts, the current state of the world has many of these normally common, easy to get parts are, "out of stock".

This should get you started on more thinking and research

Retro Grouch 

I agree with deadhead and with the bike shop guy who tried to talk you out of spending $150.00 to fix a $100.00 bike. I went through a period in my life when I acquired bike parts by cruising the subdivision on trash day to find what people had discarded. Sometimes I found a donor bike that was better overall than the one I was trying to fix. If it was my bike, I might resort to doing that again.

wcometh

dedhed
Many, many, thanks for your reply! Much appreciated.

The pic of my old crank spindle is in my avatar.

A big request. Since I cannot post pics, can you please check eBay with this phrase (copy/paste) "Vintage Sugino Maxi Bottom Bracket Eng.1370X24, 3L 115. Complete.NOS #10 ". The top hit with a red background is an exact replica of my bottom bracket spindle set, screws, bolts and bearings. And same length. Of course, its a little archaic. I just want a good likeness of my BB to be available for your comparison.

Re the upgrade and measurement checks:

1. Crank sprockets. The number stamped on the crank arm plate is IV48 and I counted 48/38/28 teeth.

2. The crank handle says PR170 so it must be 170 mm. (A ruler shows it to be about there to the center of the crank hole, center of pedal hole)

3. The BB length (width across bicycle frame) is 73 mm on the left outside-to- right outside.

4. Question: However, for example, the 48/38/28 crank set you link, to says "requires 122.5 mm bracket". My old spindle length was 115/116 mm. I figure so the extra length goes on the taper ends and does not affect the central portion involving the threads. This left thread - right thread across distance is 73 mm. Is that correct? The slighly longer taper press fit ends, means the crack arm has a "deeper" hole ?? Or something like that.

5. Yes, I have the tools to completely remove the bracket cups.

I am not a pro at all....I have learned whatever I know by reading a lot, and carefully taking my bike apart. But your answer has helped crystallize my thoughts, and confirm the parameters I need to be considering. I should be getting there soon ...>>!

wcometh

I agree with the "DIY" approach. Unfortunately, in my area its easier to find discarded hedge funds than bikes !! I live way below the poverty line....

Thanks for the moral support. Much appreciated.

dedhed

See above.

Bottom line to do this fairly easily and cost effectively you buy a new crank and BB compatible with the new crankset and dump your old stuff. You'll still have $50-60 into it but its basically plug & play. You will have to do some adjustments on derailleurs but with the same tooth count the chain should be the proper length for it all to work together.


https://www.sheldonbrown.com/bbsize.html

dedhed

We haven't even got into chainline yet which you may want to measure and check.

https://www.sheldonbrown.com/chainline.html

3alarmer 

...if you post your location, someone might be able to recommend a bike co-op. They are mostly running on limited status now, but some of them are still helping people by just fixing their bikes for a nominal fee, instead of the do it yourself instruction that many of them used to engage in. But if you really are poor, relative to the locality, it often turns out cheaper/easier to find a used bike someone does not need or want and has donated to a co-op, than to repair something that (from your description) might not have been manufactured with care and an extended product lifespan in mind.

This might seem counter intuitive, but it's true in my city, and was true over in Davis and down in the Bay Area when I was still in touch with those guys.

The reason you don't spend money to repair a $110 bike is that there are often a lot of other things that are also wearing out at an accelerated rate, because the bike was designed with disposability and a low initial price tag in mind. Bicycles nowadays are different in that regard from the Beaver's paperboy bike. Anyway, good luck with it.

wcometh

Just updating. I am still getting parts together, actually the issue is find the proper tools. Like it has been mentioned, also need to read about chains and stuff.

I decided about parts but reading about installation. How do I push the crank on to the spindle? There is aneed for a torque wrench ....and the videos talk about so many types it gets totally confusing.

BUT, I think I am a little clearer, and need to think about tools.

Will update.

Homebrew01

My first thought was to buy a used crank off Ebay, that fits the existing BB axle.

And just because the crank was loose, doesn't mean it was ruined.

madpogue 

OP's photos - https://www.bikeforums.net/g/album/18554843

We only see photos of the old spindle. Do you have photos of the crank arms, showing possible damage?

Do you still have the bearings and cups, and the plastic sleeve if applicable? Any idea what condition they're in?

The shop might not have done you any favors removing the BB, if the only problem was an arm that fell off, and may or may not have been damaged. If it was properly lubed and adjusted, they might have been just as well off leaving it.

Miele Man

With slightly damaged crankarms, I've managed to extend the life of some of them. This is what I do.

I get a pop/soda can and cut into a few strips the width of the taper on t he bottom bracket spindle. I thoroughly clean the four flats on each side of the bottom bracket spindle. I then use a gel crazy glue to glue a piece of the can to each of the flats of the bottom bracket spindle. I then put the crankarm back on a tighten it thoroughly.

Cheers

wcometh

Thanks for updating the photos.

1. The real problem was actually only the threaded end of the spindle (see the pics), where the lock nut fits on to prevent the crank arm from actually falling off if it gets loose. Indeed, the square end presses to the crank real good and required a good amount of force on the puller tool to get off. My fear was that is the crank arm aever got loose it would just fall off since the lock nut at the end keeps falling off.

2. The other parts do not look bad at all since they were not having issues. The bearings are smooth etc. The pic is attached--I need to clean the parts to make things clearer to look at.
PS: Well...the 10 post limit has hit me again. No pic.

3. The threads are really gone. I tried thread locker glue stuff and it stayed one for a brief time and came off.

4. The entire spindle with bearings, cup, nuts etc. is going for $30.00 on eBay. Just my belief that spending another $30 may get me a new updated BB and crank.

5. But no tools. I have to check back with the bike shop if they'll install it but.......$.

So I have to bite the bullet on one of the $ routes.

wcometh

I don't think the taper end is bad, see my reply just above this one. If not for this pandemic and the bike shortage, another simple bike would have been a less headache.?? You know the feeling, wondering if you are spending good money over bad ideas....

wcometh

BTW, how important is the correct torque specifications for the taper end ? It looks like around 50 Nm is required....

madpogue 

Left side of the first photo, yeah, you can see the end-stud threads are shot. Your best option at this point would be a cartridge bottom bracket replacement. $15-20. Esp. if the crank arms are okay. Did you ever find out if there's a bike co-op near you? The cartridge BB requires a socket made for it, but otherwise, it's standard tools.

This probably makes me a bad bike-wrench (or maybe I'm not setting a good example), but I've never actually used a torque wrench on the crank arm bolts/nuts. You can, I suppose. The important thing is to check them, and retighten if necessary, after riding a while.

Thomas15

What is the condition of other consumable items like tires, tubes and brake pads? If the tires are close to dry rot condition this adds to the repair cost. Also brake cables and shifter cables.

wcometh

madpogue Thanks for taking the time to reply.

Yes, the threads were the problem. There is no co-op where I am -- or within a reasonable distance. Yeah, the torque thing is getting me a little wary, since this is my first repair !! I have heard about using "perceived effort" !! However that is measured


I have decided to just get the BB and then see how the crank arms work. Then go from there. I will use perceived effort to tighten the crank........ha!

wcometh

Thomas15 Hi.

The bike is in otherwise excellent shape. The bike shop gave it a good overhaul - greasing and brake adjust, deraileur adjustment etc. The tire and stuff is really good and treading is good.

Even the paint on the bike looks intact and nice. SO that's my reason to resurrect this. When I bought this bike, I did not expect it age so well. I wish I do age like this !!

Retro Grouch 

That's a pretty important spec. 30 ft/lb is typical. Less than that and you risk the left side crank arm coming loose. More than that and you risk cracking out the crank arm at one of the corners of the square hole. If you don't have access to a torque wrench, imagine a 30 lb weight hanging on the end of a foot long wrench. That'll get you in the ball park.