I have cut the fork steer so that it is about 4mm below the stem, do I have to cut the stem shim as well so that the stop of the shim surface is level with the steer tube Thanks
Not level, you need a bit of a gap. With Aheadsets, the steerer needs to be cut shorter than the stem, otherwise you can't tighten the top cap down onto the bung/star-washer to compress the bearings. But you don't want to cut it w-a-y too short, otherwise the stem pinch bolts won't be able to grip the steerer. Park recommend 3mm http://www.parktool.com/repair/readhowto.asp?id=111 So a steerer cut to be 4mm inside the stem will be fine.
Ok thanks for the reply andy, I cut the steer shorter than the stem but do I have to cut the stem shim (1 inch steer) so that the shim is 4mm shorter than the stem?
Oh I think I get it. A 1" steerer inside a 1 1/8" headset ? And you're asking if the shim needs to be exactly the same height as the steerer itself ? Wouldn't have thought so, providing both steerer and shim are just a few mm shorter than the stem enabling you to be able to tighten-up the top cap to load-up the bearings, and neither far too short so that the stem isn't solidly gripping the steerer, I'd think it's fine.
you're right but given that he's already cut the steerer it's easiest just to trim the shim to the same height
Ok guys thanks for all your replies, yes I have a 1 inch steer with a 1/8 inch stem, would the fact that I had star nut and top cap for a 1 inch steer make any difference
[skwerl] I guess it guards against having the shim longer than the steerer, so that the stem is gripping the excess bit of shim tightly, but the steerer itself is only held loosely. [Dave] You'll need the star nut in 1" because that's the size of your steerer. I reckon that theoretically you should use a 1 1/8 top cap though, because you have a 1 1/8 stem. But providing the 1" cap fits against the top of the stem and not the shim, you'll probably get away with it
But providing the 1" cap fits against the top of the stem and not the shim, you'll probably get away with it[/QUOTE] Right thanks, that's answered my question , the shim is at the same height as my stem so I need to cut it down, Looking at the top cap it probably is 1/8 inch with a 1 inch star nut
I would have thought the top of the shim would have to be somewhere between the top of the steerer and the top of the stem - as long it's not shorter than the steerer or higher than the stem, you should be alright?
It can be a bit shorter than the steerer, or a bit longer, so long as neither shim nor steerer are way too short so that the stem doesn't grip (via the shim) the steerer sufficiently - 4mm is fine. But the shim musn't be longer than the stem.
I too have the same issue - 1 1/8" stem with shim to fit a 1" steerer. It has an FSA Orbit X headset fitted so I'm not sure what the top cap size will be (1" or 1 1/8"). Surely if the shim is the same length as the stem and the steerer tube is cut 3mm shorter than both this will be fine? Why does the shim have to be shorter than the stem?
You don't need to cut the shim. If the shim was supposed to be shorter then they'd supply it shorter. Don't cut it, it'll be fine. Just think of the shim as part of the stem. As long as the top of stem is sitting above the level of the steerer (about 3 or 4mm) allowing the cap nut to do its job (i.e. pull the headset together) then all will be well.
