spectastic

I got a new frame today. As I was building it, the bottom fork steer tube bearing was a very tight fit. I had to use a hammer to tap it in there, and I probably won't be able to remove it unless I use the hammer again, much like how bb30 works. Is this going to be a problem?

cale

Well you don't want it to fall out, do you? If you say you ".. had to use a hammer to tap it...", I'd say you're doing fine. Those lower head tube bearings can be extremely hard to seat and tapping sounds gentle.

spectastic

I bought two different frames. the other one slipped right in

cale

My guess is that it doesn't take much of a difference in tolerances for one to slip right in and one to get tapped home. Most frames are "hand finished" to a certain extent. There will be minor variations between units.

spectastic

ok thanks. I just wasn't sure what the acceptable margin of error is.

trailangel

So you didn't do any measuring huh? You just 'tapped it with a hammer'?

spectastic

it was ready to go in, just needed a little convincing. besides, I was gentle

Neverseconds

I had the same issue with my windsail carbon road bb30 frame, but it just works fine so far.

spectastic

BTW it was a rubber mallet, not a hammer... metal to metal is no bueno

Slash5

There are several headset standards - pretty well all use drop in bearings, some have pressed in cups. When you say you had to use a hammer on the bearing, do you actually mean bearing or cup?

CliffordK

There are different crown race sizes, but I would think using the wrong one would take A LOT of persuasion.

I am assuming this is a sealed bearing and not a crown race?

FBinNY 

The crown race is an interference fit, and is supposed to be hammered on. If all is on spec, the steerer is between 0.02 and 0.05 mm bigger than the race. This is to ensure that there is zero possibility of movement there.

Of course we have no way of knowing if it was on spec or not, but hammering proves there was interference, and the fact that you got it on and it didn't crack is decent evidence that it was at least close to the upper limit. So based on the evidence the bike is likely on spec.

fietsbob

How Big a Hammer was needed ?

Old Mechanic's Motto "if at first you dont Succeed, try a larger Hammer" ...

spectastic

these type

FBinNY 

Now it's a bit jumbled. Did you have to press those into the frame or onto the fork?

If onto the fork, something is likely wrong since these don't usually press directly onto the fork. Instead they're supposed to sit on a pressed on centering cone (mistakenly referred to as a crown race out of habit).

In any case one should never need to hammer directly onto a bearing. That's a good way to greatly shorten it's life. Bearings should be pressed in using adapters that press on the race itself rather than through the bearing. For example, if you were pressing the right bearing in the photo into the head tube, you'd press driving the outer ring, without touching the inner at all.

In any case, the exact bearings shown in the photo, aren't pressed in. Instead they rely on the conical sections inside and out which sit in or on mating conical seats top and bottom, with the top inner cone being the split cone which centers and tightens threadless headsets when pushed down by the stem.

spectastic

I was pressing the thing into the frame head tube. I had already slid the crown plastic thing onto the fork steer tube. I thought about bringing out a press for the bearing, but the taps were - did I mention? - gentle, with a - did I mention? - rubber mallet. besides, I'm more concerned about the frame than the bearing.

also the bearing was recessed, meaning I would need a special fitting. don't have those

cale

I could tell when you wrote that you'd used a wood block or some form of "protection". Haha

FBinNY 

Given that there are so many headset systems all installed differently, and using different approaches for bearing location, we need to be specific when discussing installation methods.

spectastic

did I mention recessed?

spectastic

well the two frames I got came with the exact same head set packs. Like I said, the other bike's bearing went right in, and the bearing went right in on the top of the head tube. It was the bottom of the head tube that needed more work. So it's a matter of manufacturing error.

cale

I'm not going to follow you there...

cale

Well, yes and no. If you have two parts and each is permitted a variance, no matter how small, then if each varies in opposite ways you can find yourself either much too loose or much too tight.

I was in manufacturing, I sold printing for many years. Every so often someone would come up with artwork that totally ignored the rules of variance. I'd try my best to realign their expectations. Sure, if I was wrong and the paper mill, the printing blanket manufacturer, the guy sipping coffee at the press, etc where all on top of their game, we could operate with the slimmest of variances. But when we couldn't, that's just a fact of life. It doesn't have anything to do with defect or error.