Author Topic: Bottom Bracket Fitting Help Needed (Read 2077 times)

Paulo · « **on:** January 27, 2008, 11:42 AM »

I've bought a US bottom bracket for my firebird and the cups are a fraction too big to fit.

I've tried using a big bolt and two big washers to coax the cups on but no luck. I would ordinarily wack with my rubber mallet but the frames just been re-chomed so don't want to try it.

So my last thought is to grind the cups down.

Are there different sized US BB's, and has anyone got any suggestions?

Cheers

P.

dwain dibbly · « **Reply #1 on:** January 27, 2008, 11:45 AM »

have you got another frame you could try the cups in??
maybe the new chrome is slightly to thick??

Paulo · « **Reply #2 on:** January 27, 2008, 11:56 AM »

There's little chrome on the inside of the frame. It's a clean job, but I guess it still might be stopping the cups from seating.

Good idea to try the cups in another frame. I have got a goose rider I could strip and try the cups in. That'll show if the cups are the problem or the frame.

Has anyone tried to grind down either the cups or the frame. Any advice?

P.

wildwood1971 · « **Reply #3 on:** January 27, 2008, 12:38 PM »

try freezing the cups overnite - and then fitting them one by one not letting them warm up.

Paul

Paulo · « **Reply #4 on:** January 27, 2008, 05:22 PM »

Another good idea. I'll give that a go too.

Thanks. I'll let you know how it goes.

Waxintaxin · « **Reply #5 on:** January 27, 2008, 07:33 PM »

remember that they should be pretty tight and bitd ,blocks of wood and hammers
OR take it to a bike shop who will have a press

Rich

Moose · « **Reply #6 on:** January 28, 2008, 10:44 AM »

If it does turn out to be the chrome that's a little thick and you can't cet them in - see if you can get someone with a lathe to turn the cups down slightly

Paulo · « **Reply #7 on:** January 28, 2008, 07:02 PM »

Has anyone come up with a good DIY cup fitting kit? Been playing around with some designs today, but I recogn the trick is to keep the cup/s square with the frame.

Send in your pics of your DIY tools.

Waxintaxin · « **Reply #8 on:** January 28, 2008, 07:13 PM »

A Vice

TwoBobRob · « **Reply #9 on:** January 28, 2008, 07:40 PM »

I use a hydraulic press on troublesome cups. My mates old Lengthy took 2 tonnes of pressure to push the cups in

A big vice is as good. Use some wood to spread the load over the cups a little and as mentioned, keep everything as square as possible

You would probably get away with some M12 or bigger stud, 2 peices of heavy steel plate bigger and nuts (dont use stainless steel...) plenty of oil on everything and wind the nuts in to pull the cups in.

motomagII · « **Reply #10 on:** January 28, 2008, 07:42 PM »

my standard frame was real twot to do too took me ages to get cups in they were mega tight

TwoBobRob · « **Reply #11 on:** January 28, 2008, 07:45 PM »

Yip. Very tight tolerances. My mates was perfect though, never gave him a moments problem

perry · « **Reply #12 on:** January 28, 2008, 08:14 PM »

this is bmx right

ive seen cups literally fall into the shell when on its side and others that were simply the wrong size

to use a lathe you need to know what size the shell is in the first place and once that calipers out i can guarantee no shell measured will be the same

decent chrome will add no notable thickness and skimming it will have it flaking off and rusting the frame

if anything more than hand tools are needed to pop some cups in then doesnt that say they are the wrong size

id love to know do those peoples bearings spin freely or do they require a little "push" ( and thats without the cranks on )

if the cups are alloy get a file and take your time , if they are steel get measuring ( precision tools ) and if they are a close tolerance warm the shell

TwoBobRob · « **Reply #13 on:** January 28, 2008, 09:13 PM »

My bearings spin beautifully thankyou. As do my friends in his Lengthy I mentioned earlier. No problems here.

MartyC · « **Reply #14 on:** January 28, 2008, 09:39 PM »

Quote from: perry on January 28, 2008, 08:14 PM

this is bmx right

ive seen cups literally fall into the shell when on its side and others that were simply the wrong size

to use a lathe you need to know what size the shell is in the first place and once that calipers out i can guarantee no shell measured will be the same

decent chrome will add no notable thickness and skimming it will have it flaking off and rusting the frame

if anything more than hand tools are needed to pop some cups in then doesnt that say they are the wrong size

id love to know do those peoples bearings spin freely or do they require a little "push" ( and thats without the cranks on )

if the cups are alloy get a file and take your time , if they are steel get measuring ( precision tools ) and if they are a close tolerance warm the shell

It's all down to manufacturing tolerances, a very tight fit is unlikely to make any significant difference to bearing cups other than making them hard to fit, the bb shell will most likely "stretch" or flare to accomodate. Get a set of vernier calipers to check the insider diameter of the bb and the outside diameter of the bb cups. A good quality BB is more likely to have a better fit than a cheap one, that said in 1982 my Profiles were a fooker to fit to both my Patterson and then my Haro so maybe that ones not right

TwoBobRob · « **Reply #15 on:** January 28, 2008, 09:49 PM »

No Marty, you're right. They're not supposed to be loose.....

Moose · « **Reply #16 on:** January 28, 2008, 10:57 PM »

Quote from: perry on January 28, 2008, 08:14 PM

this is bmx right

ive seen cups literally fall into the shell when on its side and others that were simply the wrong size

to use a lathe you need to know what size the shell is in the first place and once that calipers out i can guarantee no shell measured will be the same

decent chrome will add no notable thickness and skimming it will have it flaking off and rusting the frame

if anything more than hand tools are needed to pop some cups in then doesnt that say they are the wrong size

id love to know do those peoples bearings spin freely or do they require a little "push" ( and thats without the cranks on )

if the cups are alloy get a file and take your time , if they are steel get measuring ( precision tools ) and if they are a close tolerance warm the shell

Perry, I'm left a little confused by this post - I don't quite understand what your solution is to the question, is it to warm the BB shell? With new chrome - I certainly wouldn't.

perry · « **Reply #17 on:** January 29, 2008, 07:21 PM »

yes

to over one hundred degrees hahaha

no

nothing more than a few degrees with a hairdrier on anything bike related

still dont know what the frame is
what the cups are . one piece , open bearing , sealed , alloy , steel , new , old etc
has the frame taken a knock in the past , ie is the shell still round ? , was it round in the first place ? has it ever been submitted to a measuring device ?

were the parts for the build trial fitted before the chroming ?

could wax lyrical about what machinist to take it to but would be nice to know what the parts are first lol

have you considered a 68mm threaded bb

Paulo · « **Reply #18 on:** January 29, 2008, 09:38 PM »

Struth!!!!

Loads of suggestions thanks.

The cups are for an OPC. Although the cups in question weren't test fitted before chroming, the frame did have some in which were removed. My gut feel is that these new ones are not the best quality ups and are a fraction too big.

I'll try filing them a little first, and then make up a more robust clamp to fit them. Failing that, I'm going to hit the fook out of them with a hammer!

My concern is that if the frame gives a little to accept the cups then the chrome will flake.

I guess I'm going to have to take my time with a file.

Thanks all

Moose · « **Reply #19 on:** January 29, 2008, 11:10 PM »

Try this, but be gentle and watch that new chrome

perry · « **Reply #20 on:** January 30, 2008, 10:49 AM »

id personally use a liberal amount of grease too , moose what would you use ?

use a long rotating stroke along the file to prevent making angled edges on the cup

Moose · « **Reply #21 on:** January 30, 2008, 11:00 AM »

Grease is a great idea. I always use it when installing any cups (headset or BB) - longterm it will prevent them from rusting in.

Personally, I now use a vice with soft jaws for the installation of cups. If you have a 'black & decker workmate' it'll do the job just fine

Waxintaxin · « **Reply #22 on:** January 30, 2008, 07:48 PM »

my nos quads BB was oval lol and it took a vice ,greese and a lot of alligning cups to frme , it went in fine ,and my redline 400 BB fell into the floval ? go figure i bet the same cups out a different packet would be as good as machining the ones you have

Rich

Paulo · « **Reply #23 on:** January 30, 2008, 10:23 PM »

Thanks for your help guys. Moose, that bolt is identical to the one I normally use. Let the washers bend!!!

I do fancy getting a big f-off vice. Boys toys

steve Beech TA · « **Reply #24 on:** January 31, 2008, 08:51 PM »

My BB's were very tight, i put some grease on them and put them in with a rubber mallet, the first one i did not do this and i was scratching my head for ages as i could not get it to fit, i was hitting it that hard i thought here we go it will crack in a min, then when i put the grease on themp it still took a bit of firm tapping but it did slide in a treet it was carlube EP2 lithium grease.

Author Topic: Bottom Bracket Fitting Help Needed (Read 2077 times)

Paulo

Paulo

wildwood1971

Paulo

Paulo

motomagII

perry

perry

Paulo

perry

Paulo

steve Beech TA