Hi,

I'm new to bikes so the names for the parts that I'm using might be wrong. Sorry about that.

I have a mountain bike lying around and I ordered a mobile phone mount that basically replaces the top cap on the tube. Specs says that it's compatible with 1-1/8" tubes. Having no idea about bikes, I read it as 1" to 1.8" and measured my tube diameter (it happens to be 1"). And thought that it was compatible.

Anyway, I now have a mount with larger top cap on the way . Would there be any problems If I mount it on the bike anyway? It's inner ring will not go inside the tube but sit above it. If the screw is long enought, I belive it would work just fine. Or, should I just cancel my order before it's shipped?

Thanks.

You may have issues getting the fork adjusted properly. I would cancel it and order the right sized top cap, the fork and headset are pretty crucial and I wouldn't risk them.

Use the original cap to set your headset preload and tighten the stem bolts. Then having a stem cap at all doesn't matter.

AS long as the flat area on the top of the stem is large enough for the cap to sit flat than it makes no difference at all. Or you may put a thin spacer above the stem, and the rim of the top cap hanging over won't matter.

If you have a power drill, you can make a mandrel from a 6mm bolt and nut to hold the top cap, then use the drill to spin it against a bench grinder wheel, or against a file and turn it down to 1" if that makes it cosmetically more appealing.

Then of course, you could adjust the headset tighten the stem and swap top caps as the Demon suggested.

So you have plenty of options, and can go with the one that best suits your needs or wants.

the top cap can sit, either on top of the stem itself , or an additional Spacer, on top of the stem.

the stem's bolts around the fork steerer tube hold the headset preload adjustment.
and so if that is un touched, changing just the stem cap , wont change the headset adjustment.

I'd put a 1" spacer on top of the stem, [5mm] then put the top cap on top of that.

maybe get a longer bolt as well..

and pull off and stop the bike , before using the Phone.

Thanks a lot for the responses. A decided to keep the order, make sure my headset is adjusted properly and fixed is position, then replace the top cap. I was afraid that it would affect the structural integrity but apparently it's not the case.

Good advice