Cycling UK Forum

The bottom bracket cassette keeps coming loose on the Thorn..ie..the right hand screw in ring ...I keep tightening it up with the correct splined tool but by 50 miles it is loose again..What is the solution..?
Someone has told me about bottom bracket cassettes that do not screw into the threaded parts on the frame? Would this be the best way to go..
Chris

The BB unit screws into the frame from the chain side on a left hand thread.

Back off the nearside retaining cup (normal thread)
screw the unit fully home.
tighten the nearside retainer
job done

Make sure you're doing it tight enough. I do mine to 50Nm on the drive side and just nip up the support cup. You'll need a reversible torque wrench, I'm afraid.

Hi,
This information may come too late for the thread originator but I thought I'd post anyway as I had stumbled across this forum whilst trying to get to grips with my own loose bottom bracket issue...

Basically I had only just bought a second hand road bike. It all seemed to be in fantastic condition except I noticed after a ride that the bottom bracket had excess movement in it (lateral). I got home, undid the locking ring on the non - chainwheel side and nipped up the bottom bracket cup. It seemed ok so I retightened the locking ring and off I went again and after another 30 mins or so it was loose again. I took the bike home and started scouring the net for solutions

Again I nipped it up and again it worked loose which was very odd because the locking ring was still tight and the cup on the chain side was snuggly against the frame so that hadn't come loose. In the end I started thinking that I may just go to Halfords and get a one piece sealed unit...

Today I went for about a 10 mile ride and after getting off the bike the bottom bracket was unacceptably loose, despite being nipped up so tightly that there was a little resistance to turning... After going home I went to Halfords and picked up a bearing set. I then removed my crank arms, the locking nut and removed the adjustable side cup. Having looked at it - nothing seemed to be out of place and not being able to undo the chainwheel side cup I slid the crank axle out ensuring that it rook the bearing on that side with it.

No sooner had I started to extract the axle , I heard a "ping, ping ping" as three of the bearings came out of the cage and slid down the inside of the seat tube and popped out the end of the seat stem - Aha - there was my problem, or so I thought....

To cut a long story short I cleaned the cups, applied liberal quantities of white lithium grease and refitted the bearings as they had been. I then put everything back together and to my horror - I still had that excessive crank play!!!

I just didn't understand it, especially as I had visually inspected the cups etc and ensured that there were no rough bits. Then I picked up one of the discarded bearing sets and it suddenly dawned on me!

The bearings had been fitted the wrong way around. The reason I was having the excess play and having to retighten all the time was because the bearings had been fitted with the "frame" of the bearing cage (which is quite flat), sitting against the inside of the cups (curved). So what was happening was that whilst the axles had the benefit of having rolling bearings against them, the cups just had the flat back side of the bearing cage! As the bearing cage was being worn down by all that pedalling it constantly needed retightening and would have continued needed retightening until it broke I expect.

All taken apart again, re cleaned, greased, bearings refitted the right way around and then put back together - Absolutely smooth as silk and no lateral movement at all. In all it took me about an hour from start to finish but the time didn't bother me, I was just glad to have been able to work out what the problem was and get the result.

So if you're having this issue, before throwing your bottom bracket out in favour of a sealed unit, I'd suggest popping by Halfords and for under a fiver getting replacement bearings (with grease included) and replace the bearings - Just ensure that you get them the right way around or you'll be doing it twice like I did

Hopefully my experience will help someone out,

Andy.

I had similar problem to upstream and finally fixed it by removing the bearing cages completely. Luckily I had an old scrap frame and took the bearings from that to add to the exiting ones. I remember as a kid way back in the 70s and 80s that BBs in my bikes were all like that anyway so I'm not sure why they started using the cages. Probably makes things easier for factory assembly I guess.

Re the loose BB caused by the reversed bearings, it's worth noting that this applies to Head-set bearings also.

tykeboy2003 wrote:I had similar problem to upstream and finally fixed it by removing the bearing cages completely. Luckily I had an old scrap frame and took the bearings from that to add to the exiting ones. I remember as a kid way back in the 70s and 80s that BBs in my bikes were all like that anyway so I'm not sure why they started using the cages. Probably makes things easier for factory assembly I guess.

I agree with you here and if I found myself in the position of having to replace any bearings in the future I'd go back to the old 70's & 80's method of packing with grease and using the grease to hold bearings in place whilst I reassembled it without using a bearing cage

georgew wrote:Re the loose BB caused by the reversed bearings, it's worth noting that this applies to Head-set bearings also.

I hadn't though of that - lucky my headset seems ok.