Head set question

[Psycolist]

Has there ever been a head set produced that creates a notch in the rotation of the fork that holds the front wheel in the straight position.. I have been asked to 'service' an old 1980's 90's appx, hybrid style bike from Diamondback. I haven't started on it yet, but wheeling it into my workshop, I noticed that the front wheel seems to slot into the straight position. I figure, if its a bearing problem, it is extremely unlikely that it just happens to hold the wheel in the straight position. At the same time, I have never come across this 'function' before. Anyone got any experience or info on this system, if it is a system, I would be glad to hear from you. Ta.

 

[earlestownflya]

it's just too tight

 

[ANT 666]

Nuff said.

 

[Psycolist]

If that's the case, why is it only 'notched' in the straight position. I wondered if had been over tightened when the wheel was straight, but just being too tight seems too simplistic. As I said, no work done yet, but its going to be the first thing I look that.

 

[earlestownflya]

If that's the case, why is it only 'notched' in the straight position. I wondered if had been over tightened when the wheel was straight, but just being too tight seems too simplistic. As I said, no work done yet, but its going to be the first thing I look that.

it returns to straight on because that's where the pressure on the bearings is least....that's what you're feeling as a notch.

 

[Erudin]

It's called "Indexed Steering" ("Brinelling")

From http://www.sheldonbrown.com/headsets.html

"All of the other ball bearings on a bike spend their lives rotating round and round, but headsets spend most of their time pointing straight ahead. Sometimes you will see that the bearing balls have created a neat row of little dents in the bearing surface of the lower frame cup and/or the crown race. This creates the effect commonly known as "indexed steering" where the balls sort of "snap" into place, and the fork tends to stick in the straight-forward position."

See also http://www.sheldonbrown.com/brandt/indexed-steering.html

 

[Psycolist]

OK, seems like a reasonable theory. It seems odd that in 10 years of working on bikes, its the first time I have come across this phenomenon. To be fair, most bikes I get to work have the opposite problem, I will ease the tension on the bearings before I do anything else, and see if that has any benefit. More likely is a new headset to solve the issue. Thanks for the very prompt replies. ( I will let you know when I've had a fiddle)

 

[Smurfy]

I hate bikes that have this fault. You can't ride them hands off!

 

[raleighnut]

It's called "Indexed Steering" ("Brinelling")

From http://www.sheldonbrown.com/headsets.html

"All of the other ball bearings on a bike spend their lives rotating round and round, but headsets spend most of their time pointing straight ahead. Sometimes you will see that the bearing balls have created a neat row of little dents in the bearing surface of the lower frame cup and/or the crown race. This creates the effect commonly known as "indexed steering" where the balls sort of "snap" into place, and the fork tends to stick in the straight-forward position."

See also http://www.sheldonbrown.com/brandt/indexed-steering.html

^^^^^^+1, I've had bikes that do this, it is much more common on headsets that use a retainer to space the bearings, a cheap fix can be to use more 'loose' bearings (not in a retainer) but this doesn't always work.

 

[RichardB]

The act of moving forward and staying upright involves many small movements of the steering (largely done automatically by the physics of the bike), and if the steering is stiff, rough or 'indexed' as described above, the bike can be almost unrideable, or at least feel to be handling very strangely. Not sure if it an accepted term in cycling, but motorcyclists call it 'thrupenny-bitting' (or 50-pence-piecing for the youngsters) from the path the bike has to take round a corner. It robs the ride of all pleasure, as just keeping the bike in a straight line involves a lot of tiny steering inputs, instead of letting the bike find its own way. I had a Triumph Sprint that had this problem (and resulted in my only tumble in about 30 years) and new head bearings transformed it.

 

[FrankCrank]

.....surprising that in many years working on bikes the OP has only just encountered this - it's a very common issue with caged bearings. Another way to alleviate the indexing is to do a full rotation of the fork every now and then, that way the bearings settle in a more random fashion. But it's a chore most would neglect, including me.........

 

[raleighnut]

.....surprising that in many years working on bikes the OP has only just encountered this - it's a very common issue with caged bearings. Another way to alleviate the indexing is to do a full rotation of the fork every now and then, that way the bearings settle in a more random fashion. But it's a chore most would neglect, including me.........

It happened to me on tour with the Ridgeback once, turning he bars 'lock to lock' a few times got rid of it for 10-15 miles but then it'd return. got into the habit of doing it every time I came to a stop, people who saw me must have thought I was crazy. Got me home OK though.

 

[Citius]

It seems odd that in 10 years of working on bikes, its the first time I have come across this phenomenon

You haven't worked on enough bikes then....

 

[Gravity Aided]

You may also remove the headset, turn it 90 degrees, and re-install it, as you'll rarely have it turned so far. Older Trek bicycles with the older Campagnolo headsets used to take a set like this, due to the softness of the metal in the races, IIRC. But your best bet is to install another headset, that way you're covered for a long time.

 

[Psycolist]

Thank you all for your replies. This seems to be a much more common occurrence than I had imagined. The flat spotted bearing reply really puts the situation into perspective. Good old Sheldon has the answer once more. I should have known to go on his site and have a mooch among his informative and very comprehensive posts. I only work on bikes as a hobby, I have not had any training other than what I have picked up in this forum and by experience. This will be another 'problem' that I will now know the answer to in future. Thanks again to all contributors.