BB (crank arm length) upgrade - Huffy Rock It ? Help

Questions regarding lubrication, adjustments, repairs and other issues
Forum rules
Be polite and courteous! Stay on topic!

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby Tomcat65 » Wed Nov 16, 2016 8:00 am

Image

The Pf30 will most likely leave you looking at a limited group of cranks, further limiting your options, and getting very exensive

UNLESS

You adapt to a BSA threaded bb:
http://www.jensonusa.com/!oey2abFCckkF1Xq4BQHctw!/SramTruvativ-PF30-To-6873mm-BB-Adaptor?utm_source=FRGL&utm_medium=organic&pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=CjwKEAiApLDBBRC8oICb9NvKsg0SJAD9yOHsSSVDrQjMVX7N3Eu1ndADJ_XfhnX6Z9t1by3SQVeo8hoCkuLw_wcB
Image

$27.00 and you open up all kinds of options.This might work, but you'll still have more in the crank than you paid for the bike
AND that 1mm in the press fit 46 to the 47mm bb shell, will make a difference and probably a squeaky, creaky ride. Press fit bb's have a reputation for noise in the proper applications. Maybe a good dose of blue loctite could make it all better? But then it goes from a hack to a bodge and it's a $50 bike.. If you don't mind spending the $$, It looks like a near fit, but not perfect. There are always other "alternative" methods of making $#*+ fit, JB weld, foil shimming, lead soldering, carbon fiber repair kits etc.. lol
:D
But then there's that slim chance that it'll be perfect and everything you wanted it to be

hmmm..
Tomcat65
 
Posts: 1540
Joined: Mon Jun 23, 2014 3:12 pm
Location: Western Kentucky

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby BicyclePhD » Wed Nov 16, 2016 8:41 am

The blue loctite by itself will not work if you are using the delran cups of a PF30. You will need to use two different loctite products the first is a sealer that coats the cups, this will seal the pores tiny holes, sorry I can't remember the number of it right now. After that dries then you can use the bearing retaining compound one to take up some of the tolerance issues between the PF30 shell and the frame.
BicyclePhD
 
Posts: 13
Joined: Thu Mar 31, 2016 7:08 am

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby dddd » Wed Nov 16, 2016 8:40 pm

When I posted above, I was expecting that the bike's original cones could be fitted to the new, longer crank, so that the bearings and cups would be a matching set, with no machining needed.

Spinning a cone's outer flange down in size using a bench grinder would be easy, but whether the bearing's rolling track diameter is the same between the old cups and new cones might best be determined first, as in "measure twice and cut once".
dddd
 
Posts: 528
Joined: Tue Dec 29, 2015 12:04 am

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby frictionshift » Wed Nov 16, 2016 11:41 pm

dddd wrote:When I posted above, I was expecting that the bike's original cones could be fitted to the new, longer crank, so that the bearings and cups would be a matching set, with no machining needed.

Spinning a cone's outer flange down in size using a bench grinder would be easy, but whether the bearing's rolling track diameter is the same between the old cups and new cones might best be determined first, as in "measure twice and cut once".


This is probably the least expensive route to take, and I have been putting a lot of thought into it.
Bearings will have to be packed loose, and bearing size & count will change a little, but that will work.

The crank arms (at least the left arm) will need to be shaved down in diameter also, and that is going to be the trick to snaking it through the BB.

I remember a slender one piece crank with standard threading/sizing from back 30 or 40 some years ago.
The steel wasn't very good quality and the threads on the crank arms would wear down causing the pedals to fall out.
Anyone else remember those?

I need to find a bike shop where I can walk the frame in and drop the PF30 or the BSA (is it the same thing?) in to eyeball the fit/difference before dropping that kind of change into the frame.
Then the other crank components are going to add up... but I might have to end up going with the adapter(s).
Can't see any benefit in tossing a brand new frame, but I don't want to sink a bunch of bucks into it.

Thanks for the help and ideas everyone :D you all are great!

Numbers like PF 30 and 47 mm confuse me.
47 mm even confuses the local wrenches.

Hopefully I'll have a picture to post of the finished bike this coming spring.
I'm the old man you see on the bike.
I love my 10 speed, but can't resist taking my 20 inch for a spin.
So I bought this cheap bike to use for donor parts, but find myself trying to build it back up now...
frictionshift
 
Posts: 23
Joined: Sun Oct 02, 2016 10:18 pm

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby frictionshift » Sun Nov 20, 2016 10:55 pm

Tomcat65 wrote:Image

The Pf30 will most likely leave you looking at a limited group of cranks, further limiting your options, and getting very exensive

UNLESS

You adapt to a BSA threaded bb:
http://www.jensonusa.com/!oey2abFCckkF1Xq4BQHctw!/SramTruvativ-PF30-To-6873mm-BB-Adaptor?utm_source=FRGL&utm_medium=organic&pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=CjwKEAiApLDBBRC8oICb9NvKsg0SJAD9yOHsSSVDrQjMVX7N3Eu1ndADJ_XfhnX6Z9t1by3SQVeo8hoCkuLw_wcB
Image

$27.00 and you open up all kinds of options.This might work, but you'll still have more in the crank than you paid for the bike
AND that 1mm in the press fit 46 to the 47mm bb shell, will make a difference and probably a squeaky, creaky ride. Press fit bb's have a reputation for noise in the proper applications. Maybe a good dose of blue loctite could make it all better? But then it goes from a hack to a bodge and it's a $50 bike.. If you don't mind spending the $$, It looks like a near fit, but not perfect. There are always other "alternative" methods of making $#*+ fit, JB weld, foil shimming, lead soldering, carbon fiber repair kits etc.. lol
:D
But then there's that slim chance that it'll be perfect and everything you wanted it to be

hmmm..


Let me see if I understand this...

Is the adapter all I need ?
I think this is what I am reading.

Or do I install the PF30 and then install an adapter for BSA ?

The bike is down to the frame and a fork at this point, and I'm starting to doubt the integrity of the fork.
I'm the old man you see on the bike.
I love my 10 speed, but can't resist taking my 20 inch for a spin.
So I bought this cheap bike to use for donor parts, but find myself trying to build it back up now...
frictionshift
 
Posts: 23
Joined: Sun Oct 02, 2016 10:18 pm

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby Tomcat65 » Mon Nov 21, 2016 7:02 pm

I don't even want to pretend to know what you need to do, lol...
But if you do buy that adapter, you will still have to buy the BSA bottom bracket.
I don't know that the adapter will work 100% perfectly, it's just the closest thing to the size of your bb shell.
If you try it, I hope it works, but that 1mm could make it a slip and spin fit. Which might be a problem, but maybe you could overcome it with some ingenuity.
Tomcat65
 
Posts: 1540
Joined: Mon Jun 23, 2014 3:12 pm
Location: Western Kentucky

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby frictionshift » Mon Nov 21, 2016 10:54 pm

Wonder what the odds are that I can find a spline that will match the cups, bearings, cones, washer & nut that I already have ?

Something inexpensive, like this...

spline.jpg
spline.jpg (12.63 KiB) Viewed 284 times


This would take me to three piece without any adapters, loctite, JB Weld, shimming, bottom brackets, or machining if I have my brain wrapped around all of this :? .
It would make a cheap and simple hack... I think.

Or am I missing something ?

At my age it is way too easy to overlook something important.

This just looks and sounds so simple that I have to be missing something.
I'm the old man you see on the bike.
I love my 10 speed, but can't resist taking my 20 inch for a spin.
So I bought this cheap bike to use for donor parts, but find myself trying to build it back up now...
frictionshift
 
Posts: 23
Joined: Sun Oct 02, 2016 10:18 pm

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby Tomcat65 » Tue Nov 22, 2016 4:09 am

That would be awesome :)

Very often, we over think something simple, we try a few familiar things that don't work, don't fit, and we get lost in details. The next thing you know, this simple thing has taken us into unfamiliar places where the cost starts adding up.

You have cups and bearings. What you need now, is a way to get either a crank or a crank spindle to fit. The one thing that comes to mind without seeing what you have, is to try loose ball bearings in different sizes. The ball bearings in cages will place limits on everything you try.
Tomcat65
 
Posts: 1540
Joined: Mon Jun 23, 2014 3:12 pm
Location: Western Kentucky

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby frictionshift » Tue Nov 29, 2016 6:23 pm

I ordered that spindle a little while ago Tomcat65.
Paid a whopping $17 for it and will get to play around with bearings in a week or so.

Been pricing crank arms and can safely affirm that this upgrade alone will cost much more than the bike :roll: but in the end it will be that one of a kind ride :D .

On a side note, I've decided to beef up the whole bike and post the build progression in a new thread.
Maybe it'll end up being a 21st century muscle bike, or a lowrider, or something... usable 8-) .
I'm the old man you see on the bike.
I love my 10 speed, but can't resist taking my 20 inch for a spin.
So I bought this cheap bike to use for donor parts, but find myself trying to build it back up now...
frictionshift
 
Posts: 23
Joined: Sun Oct 02, 2016 10:18 pm

Re: BB (crank arm length) upgrade - Huffy Rock It ? Help

Postby frictionshift » Wed Dec 07, 2016 3:58 pm

Tomcat65 wrote:The one thing that comes to mind without seeing what you have, is to try loose ball bearings in different sizes. The ball bearings in cages will place limits on everything you try.

The 5 1/6 bearings are definitely too big for the job... Unless I ream the centers out of the (original) cones and cut new threads into them...far beyond both my skill and tool set.

Will probably take spindle, cups, and cones down to the auto parts store. Maybe they'll have the right size bearings to make it all fit.

Then again... They do have a machine shop.

Or I might just end up using the short crank :cry:
I'm the old man you see on the bike.
I love my 10 speed, but can't resist taking my 20 inch for a spin.
So I bought this cheap bike to use for donor parts, but find myself trying to build it back up now...
frictionshift
 
Posts: 23
Joined: Sun Oct 02, 2016 10:18 pm

PreviousNext

Return to Technical

Who is online

Users browsing this forum: No registered users and 2 guests