Replace headset bearing

paulbnix

A few weeks ago I noticed a brown smear at the top of the forks and, after reading a thread on this forum, realised that the lower bearing had been affected by water. Its an FSA tapered headset on a Boardman Road Comp.
I cleaned out and regreased the bearing but now find that no matter how tight I preload the headset there is still a slight knock. So I assume the bearing needs replacement.
Its a sealed unit that is larger than the 1 1/8th top bearing but there is nothing written on the bearing to indicate what size it actually is - where do I measure in order to determine the size?
Where is a good place to obtain a replacement?

keef66

just for the avoidance of doubt, are you preloading by tightening the bolt in the top cap before tightening the clamp bolts which secure the stem onto the steerer?

And are you sure that the thing the top cap bolt is threaded into (star nut or expander bung) isn't moving up the steerer?

paulbnix

Yes I am applying the preload correctly with the clamp bolts undone.
When I first got this bike (May 2012) I did have an issue with getting the right preload because the expander bung was moving but I fixed that a while ago.

wishitwasallflat

paulbnix wrote:

an FSA tapered headset on a Boardman Road Comp.

there is nothing written on the bearing to indicate what size it actually is - where do I measure in order to determine the size?

Where is a good place to obtain a replacement?

Any branch of Halfords or their on-line Q&A should be able to tell you the size - and order it for you - but once you know the size the world is your oyster ... :!: If you have vernier or digital caliper you can measure it yourself but the bit I couldn't work out was how to measure the bearing angles - there is a tool but its £15 and I couldn't justify it to myself as I don't think I would use it enough.

maringirl

Halfords wont be able to tell you - they will just go on the internet and look it up - so you can do it for yourself and it'll be cheaper. I know I have done it!

chaos75

i've got a road team, not sure if it's the same headset but i think it is.
i replaced mine recently with FSA MR110 (ACB 36 x 45 073#) and MR121.
Got the lbs to order. I think they were about £11 each.

Gareth

paulbnix

I think I now understand what is wrong but I can't figure out what has happened :?:

Basically there is a gap down to the bung but its not enough to allow the preload to be fully applied. I tested this by adding another spacer above the stem.
It was ok before I took the headset apart and regreased the lower bearing.
I have all the spacers that were there before and I can't see any bits I left out so I am a bit baffled.
The bung is one that lies flush with the top of the steerer so I will get another that can go further down.

keef66

Is it an all carbon steerer or alloy? If carbon it might require a bung that sits right at the top (My Scott does)

paulbnix

It is carbon so I have kept the original bung and just added a very thin spacer above the stem.
All sorted now.
Thanks for responses I'll note the bearing type in chaos75 response in case my regreasing didn't work.

slug56

Just stumbled across this post in my quest to replace my headset bearings for my Boardman Road Comp (2012). Just to verify we're talking about the same bike, it's this one -https://web.archive.org/web/20130110011328/http://www.boardmanbikes.com/road/road_comp.html

I suffered the 'rusty smear' from the headset many months ago, and since then things have been going downhill. A trip to Halfords revealed that the headset is the FSA Orbit C-40 ACB (Angular Contact Bearings), link here: http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_972272_langId_-1_categoryId_210157. However, I didn't fancy paying upwards of £50 for it.

I'm at the point now where no matter how much I tighten the top bolt (with the stem bolts loose, of course), I'll get knocking noises and the headset will seem to work its way loose, at which point I have to repeat the process. I've tried stripping down the entire assembly, cleaning, regreasing, checking the compression plug, spacers etc... But I think it's my bearings that are shot.

A bit more digging revealed the individual part numbers for the upper and lower bearings.

Upper: FSA TH-870 MR042 1 1/8" ACB 45° x 45° (Part number: 160-6480), Link: http://www.ukbikestore.co.uk/product/140/160_6480/fsa-th-870-mr042-1-18-acb-45-x-45-campag-headset-bearing.html

Lower: FSA TH-073 MR110 1.5" ACB 36° x 45° (Part number: 160-6740), Link: http://www.ukbikestore.co.uk/product/140/160_6740/fsa-th-073-mr110-15-acb-36-x-45-headset-bearing.html

I've just purchased replacement bearing from the above links, and I'll post back saying whether they've resolved the problem. Well, if I don't post back then assume all is good, otherwise I'll definitely post back if the problem persists or the bearings don't fit.

EDIT: Apologies for replying to a slightly old post, but if someone comes across it in an internet search (as I did), then at least there'll be some information to help them find a solution to their headset woes.

paulbnix

Yes that is the same bike as mine.
As I said in the earlier post regreasing the bottom bearing worked and my problem was insufficient space for the preload to be properly applied. An extra spacer sorted it.