Bottom Bracket Woes

[neptune]

I was out riding my pushbike today, when I noticed random noises from my transmission. On closer inspection, turning the cranks backwards met with some resistance at certain points in the rotation, I have had my eye on the bottom bracket for a while, as it has developed slight play in the bearings. As a temporary measure, I tried to get some lube into the bearings. I removed the left side crank, laid the bike over, and ran some gear oil down the shaft. I figured if the bearings are worn, so are the seals, and so I should be able to get some oil in. The situation is improved, and the noises are gone, but I guess we are on borrowed time.

It is a sealed type BB, and the hub shell of the frame is about 68mm wide. It looks like I need a tool with 0 external splines, and there are plenty on E bay. The axle is a square taper type. I need to measure its length, Do I need to measure anything else before ordering?

 

[Deleted member 4366]

They're standard, so any Shimano tool will do it, but get one with a big hexagon on rather than 1/2" square drive. Don't forget about the left hand thread on one side. You might also need a big lever arm or a lump hammer to get it started. Use the crank retaining bolt and a big washer to hold the BB tool into the spline while you try and turn or hit it otherwise it'll keep jumping out. What bike is it?

 

[neptune]

Hi Dave. It is a pushbike, not electric. It is a Raleigh Metro Pioneer, 2010 model. The gears are Shimano. I like the idea of using the crank bolt to hold the tool in place, That means however you cant drive it with a socket ratchet tool. I notice these tools also have flats on to drive it with a spanner. My next job will be to remove both cranks to measure the axle length, as most Ebay suppliers stock a number of different lengths.

Just re read your post where you suggest it is better to drive it with a spanner rather than a ratchet tool.

 

[Deleted member 4366]

I use a big adjustable spanner that normally needs whacking with a lump hammer for well-used BBs like yours. The Shimano cartridge BBs that they have in Halfords for about a tenner seem to last quite well. They have a range of sizes. The reason I was asking about the bike is because you might think about upgrading to a Shimano M590 crank-set, that comes with a hollowtech BB for about £60. It's lighter and stronger, and the cranks never creak or come loose. On special offer at the moment:

http://www.chainreactioncycles.com/shimano-deore-m590-9-speed-triple-chainset/rp-prod40496?utm_source=Google&utm_medium=Shopping&utm_name=UnitedKingdom&gs=1&ds_e_ad_type=pla&gclid=Cj0KEQiA2o6lBRCn_b7yppe98rQBEiQAMpnYnUhJQJ6_-2TTHO7O7gwPRL7HaFYgbjTFClKmlrLOFPQaAlTh8P8HAQ&gclsrc=aw.ds

 

[john h]

Neptune you just need to know the shell width (ie 68 ) + spindle lengh (ie113) this info will be on the old shell you take out.

 

[awol]

Use the crank retaining bolt and a big washer to hold the BB tool into the spline while you try and turn or hit it otherwise it'll keep jumping out.

You are full of amazing tips d8veh, I've always had trouble getting the BB tool to stay in and nearly breaking the small teeth in the process. Next time I'm trying this.

 

[Deleted member 4366]

There's engineers and oily rags!

 

[OldBob1]

Dave I thought engineers came from oily rags

 

[Deleted member 4366]

You have to start somewhere!

 

[neptune]

Today I changed my bottom bracket, and on the whole it went quite well. I took advice from d8veh, and bought the tool with the big hexagon, rather than the one with the half inch socket drive. I also used his tip of holding the tool in place by a crank bolt. This is the same idea as using a wheel nut to hold a freewheel removal tool in place.

I watched a couple of videos on Youtube to get the idea. I then removed the cranks from the bike. I then fitted the tool to the left hand, non drive side of the bike. Having fitted the tool and the retaining bolt, I turned it anticlockwise to unscrew it. The only tool I had that would fit the hexagon was a huge stillson wrench, about two feet long. I was expecting it to be really tight.Actually it unscrewed quite easily, and I could have managed with a pair of slip joint pliers.

A sealed bottom bracket consists of two parts, the main assembly, and a threaded collar. To my surprise, working from the left side of the bike, the whole assembly came out, whereas on the videos, only the collar came out from the left.

Moving to the drive side, I unscrewed the collar with its left hand thread. With the assembly removed, I noticed two things. First, the shaft made a rumbling noise when turned with the fingers, confirming that it was worn. Secondly, the screw on collar was made of plastic!

I took the old assembly to Halfords, to get a replacement. The original axle was 120mm long, and the nearest they stocked wes 122 mm. That is only 1 mm each side, so not likely to be noticed. I cleaned everything up with WD40, and some kitchen paper, and greased the threads. The new assembly was marked Left and Right. Oddly, the main assembly screwed in from the drive side, the opposite to the original bottom bracket. It is impossible to fit it wrong way round, as the drive side threads in the frame are left handed, and right handed on the opposite side of the frame.

The only problem I had was getting the left hand thread to start, as it would go in a couple of turns, and then went tight. Moderate pressure from the tool soon had it screwed all the way in. So it is all fitted and reassembled now. A road test showed that all was well. On the whole, it went well, and like all jobs, its a case of getting stuck in and having a go.

PS. Unless it is my imagination, the bike is now easier to pedal.

 

[awol]

The past 2 new bikes I've bought both came with sq taper sealed bearing bottom brackets which intermittently clicked, generally when setting off from junctions, any ideas of the cause? When they were removed they spin quite smooth and free.
I changed them for new ones which are ok but I still have the the originals and am wondering if there is a common reason and fix?

 

[Deleted member 4366]

Axial free-play?

 

[awol]

No free-play, however not as smooth when compared to a new one I had.
I got an old one out and found the slight click was there occasionally spinning by hand with pressure on, so have dismantled it down to component parts and the sealed bearings are very smooth and free on their own so am going to try carefully re-assembling and see if that has helped, or might even see how much the bearings are one their own.
Incidentally if anyone wants to know the info on the sealed bearings is 17x31x10 2RS but I guess the cost of new BB makes it not really worth the hassle.

 

[neptune]

Today I did a post mortem on my old bottom bracket. The first surprise was that the entire outer shell was made of black plastic. The main body is just a tube. The middle section has a reduced diameter to prevent the bearings drifting inwards. The shaft has a central portion of larger diameter for the sane reason. The main body has two end caps, one of right hand thread and one of left hand thread. Both are a press fit on the central tube.

Plastic does not seem to be a suitable material, but the assembly worked well for over 16,000 miles, more than the average pushbike does in its life. The actual bearings were well worn out, with lots of play. It does seem worrying that the splines which the removal tool engages are also plastic.

If I were designing a bottom bracket, I would have those bearings pressed directly into the bottom bracket shell of the frame. The shell would need to have an internal shoulder, to stop the bearings drifting inwards. A groove could be machined outboard of the bearing to take a circlip if it was found to be necessary. This design would need less material, and would allow a slightly bigger bearing, or a thicker shaft. Sizes could be chosen to accommodate a common, off the shelf bearing.

 

[Deleted member 4366]

If I were designing a bottom bracket, I would have those bearings pressed directly into the bottom bracket shell of the frame. The shell would need to have an internal shoulder, to stop the bearings drifting inwards. A groove could be machined outboard of the bearing to take a circlip if it was found to be necessary. This design would need less material, and would allow a slightly bigger bearing, or a thicker shaft. Sizes could be chosen to accommodate a common, off the shelf bearing.

That's more or less how hollowtech works, except they use the opportunity to have a larger diameter shaft, so the bearings are in holders outboard of the BB shell. I've changed over most of my bikes to hollowtech because the whole system is stronger, stiffer, lighter and easier to service.

The plastic used in BBs is only to hold the bearing in place. It doesn't need to be particularly strong. It has one massive advantage that it's always easy to remove those plastic bearing holders. If you had had metal ones, you'd have needed a sizeable lump hammer to extract them.

 

[neptune]

d8veh.Always interested to hear your comments and observations. You are right in that I found the plastic ones easy to remove. I am fairly sure that the new BB I fitted was made of aluminium, and I made sure to grease the threads liberally in case it has to come out again. Thinking about it, all the stress on the plastic bits is compressive, and as I said it worked well for 16,000 miles.

The main thing that worried me was the plastic splines, but the load is spread over 20 splines, and as plastic is corrosion free, not a lot of force is needed for removal. I suspect that the danger, if any, is in overtightening whilst fitting.

The Hollowtech design sounds good, but in view of the age of the bike, I could not really justify the cost, as a new crankset would be needed as well as a BB.If the new BB lasts as well as the original one, I will be well happy.

 

[awol]

I too have done post mortem on my old BB but on the sealed bearings as they weren't as smooth as I thought and a touch 'bitty' turning by hand, as I had nothing to loose I removed the side seals to reveal a few rusty bits. I totally degreased and am going to try a bit of grinding paste in there to see if they smooth out. If so I will re-grease and re-use.

 

[neptune]

In the past, I have "resrurected" bearings in various things simply by washing the bearing out with paraffin, allowing to dry, and repacking with grease. It definitely improves things, at least for a time. The bearing in my BB were well past that though.

 

[rusky]

I'm a bit late to the party but if like mine, you can't use the bolt to hold the tool in place, a G-clamp does the trick, just remember not to wind it up hard & to loosen it off slightly as it moves!

I had to remove the last BB with a 4' pole!