Hi. The steering on my recently recommissioned Dommie 99 has always been a bit ‘lively’. On checking the forks with the front wheel raised off the ground I found I could rock the fork legs backwards and forwards a tiny bit (a definite MOT failure).
The play couldn’t be removed by tightening the adjuster nut. So I bought some new sealed bearings and the necessary spacer tube from AN to make the steering bearings ‘fit and forget’. However, on fitting the new bearings, the rocking problem persists. The reason is that the top bearing is loose in the headstock. The bottom bearing is a snug fit (although the lower headstock tube does seem to be a bit oval) but the top one has a 6 thou gap all around its circumference. Perhaps the outer race of the old taper roller bearing had spun in the headstock and been ignored by the previous owner?
I don’t know the cause of that looseness.
So that gives me a problem. Is it fixable? Do I take the new top bearing I got from AN and fix it into the headstock with a bearing retaining liquid such as Loctite 738? Do I get new taper roller bearings and fix the top ones outer race into the headstock with Loctite 738?
Are there any other options?
Any suggestions gratefully received.
Regards
Tony
When you put the new top…
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Hi Terry. Thanks for your…
Hi Terry. Thanks for your input. My top steering bearing just drops into the stem, then it can be rattled around in the stem with only light finger pressure. The fit of the bearing on the fork stem is very good with no rocking.
Good luck with sorting out your steering.
Regards
Tony
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Bearing fit
Hi Tony
I,m about to replace the taper roller bearings in my 65 Atlas with sealed ball bearings and spacer like you but using the angular contact equivalent.
Both old outer races were still a firm fit in the headstock, needing tapping out with a drift after well over 100,000 miles. Yours are definitely too loose if you can rattle it around by hand.
I use Loctite 638 on various things and it,s excellent up to 0.010” gaps. Should be perfect for your 0.006” gap. Try it and see with your new setup.
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Thanks Neil. Loctite 638…
Thanks Neil. Loctite 638 seems to be my only option really. I’m just a bit concerned about its physical strength because the outer race of the upper head bearing will always be trying to move forwards and backwards as it gets put under load from the forks. I’m concerned that the Loctite might start to fracture and break up, resulting in a slack fit again. Any ideas on how physically strong Loctite 638 is? I know it can’t be as strong as the steel in the headstock as it’s just a form of plastic, but is it strong enough for fixing steering head bearings in place?
Regards
Tony
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Another option would be some…
Another option would be some shim steel, if you can work out the exact gap you need to close up, shim steel comes in different thicknesses, I have some brass that is .004", it cuts to size with scissors .Find some the right thickness , the benefit being the bearing will come out again in the future and no loctite creeping into the bearing when being installed.
Regards, Terry.
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Hi Terry. Shimming is…
Hi Terry. Shimming is something I considered seriously but the top bearing location in the headstock has gone slightly oval. That would be tricky to shim as I’d have to insert narrow strips of various thickness shim vertically around the bearing to take up the gap - I don’t think that would work too well. Because of that, I think my best option is the Loctite 638 route.
Regards
Tony
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Loctite 638
Hi Tony
I think the top steering head bearing axial and radial loads would be at the low end of 638 capabilities. Certainly much better than having it loose enough to fail an MOT. I,ve heard of it being used successfully on undersized crownwheel bearings on a car diff over many miles.
Try it and see or give Loctite a call.
https://www.wychbearings.co.uk/638x10ml-Loctite.html
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Thanks Neill. Bottom bearing…
Thanks Neill. Bottom bearing is now in with Loctite 638 - will allow that to set then I’ll do the same with the top (slack) bearing.
Regards
Tony
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I'd have done it slightly differently -
- assembled both top & bottom with loctite and tightened it all up to help make sure they were aligned while the loctite set. Although admittedly that doesn't take too long. The slight risk with the way you have done it is that the loctite on the bottom race will fix it in place slightly out of line with the top bearing.
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Hi Ian. Thanks for your…
Hi Ian. Thanks for your suggestion. I did think about doing it the way you suggested and it seems a good idea but I couldn’t decide whether to do one bearing at a time or both at the same time. In the end I decided to do the bottom one first so I could get the outer race fully seated against the step on the inside of the headstock tube. Now I just have to hope that the top bearing aligns with the bottom one when I fit it with the lower yoke.
Regards
Tony
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When you put the new top bearing in, did it fall in the headstock, rather than a firm push ( minimum), or is it that the steering stem is slack in the top bearing inner ?
There is a small difference in the sizes of the imperial and metric bearings , check out the bearing sizes and fit clearances created by the imperial/metric differences before deciding where to fill gaps up with bearing fit or Devcon etc. Some very careful measuring required, before deciding where to apply bearing fit or anything else.
Try the top bearing on the steering stem, mine has small but noticeable play despite being a 1" imperial on the 1" stem, starting to strip that out tomorrow to see what is required.
Regards, Terry.