Steerer length and Stack Height

[Tomianson]

Simple question just to confirm in my head if thats ok.
When determining the steerer length needed for a fork, its the head tube length plus the Stack Height of the headset isnt it? I've always measured it before and cut and got it right, but just wanted to check the mathematical method is that simple?
Thanks

 

[raidan73]

That's it Tom Obviously you need to allow a mm or two for the lip or rubber seal on the top lock nut of a threaded headset

 

[FluffyChicken]

Thread headset of course.

 

[Splatter Paint]

I’d physically check the stack rather than going on manufacturer’s values alone.

Thread headset of course.

^^ + stem and spacers if Aheadset!

 

[Tomianson]

Cheers. Will double check it against the manufacturers figures abs will allow a couple of mm for the rubber lip on the top nut. Better a couple of mm too short than too long.

 

[FluffyChicken]

The lip is usually taken care in in the stack height.

What headset is it?

 

[Tomianson]

The lip is usually taken care in in the stack height.

What headset is it?

XTR m900 1”

 

[FluffyChicken]

H +22.8+11.5 (top, bottom) and shimano already caters for its lip/stop.
The Pro's chamfer the finish to make it look nice and slot on easily.

~page 48 https://1drv.ms/b/s!AuDkhAv29wDHsjvKjYwBlhAa8grx

 

[Tomianson]

H +22.8+11.5 (top, bottom) and shimano already caters for its lip/stop.
The Pro's chamfer the finish to make it look nice and slot on easily.

~page 48 https://1drv.ms/b/s!AuDkhAv29wDHsjvKjYwBlhAa8grx

Cheers that’s really helpful. I take it H is the head tube length?
and do I take the top surface of the crown race bit as 0 and measure up from there before cutting? Or from bottom of crown race?

 

[FluffyChicken]

It's everything. H Is headtube length yes.
I link one of the old biking bibles, it got more than enough info there, from first steps of measuring.

The details for the Shimano are from the HP-M90x headset.