Where can I get an adapter which slips onto a fork steerer to add space between the fork crown and the head tube?

Problem solvers doesn't make one. I'd just use a piece of aluminum tube, but I want the crown race to seat correctly.

There's a reason they don't offer that kind of extension.

Take a close look at your steerer tube. Steerers are usually reinforced for the bottom inch or two where the crown and lower head cup are. That's because what's below that is cantilevered out without any secondary support. (Imagine what would happen if a fork failed at that point).

If you add a spacer pushing the crown race higher on the steerer you could go beyond the reinforced zone. Also extending the axle further away from the crown increases the bending stress at the crown. More bending moment applied at a less reinforced point is a recipe for disaster. No wonder nobody makes the extender you envision.

How much did you want to add? I've mismatched suspension and rigid forks on MTBs before without any of the adverse handling effects I always read about. Unless your fork is way off, I bet it'll ride just fine.

Machine shop around you? Local economy= hire your neighbors to make a sleeve.

+1

I've done a few fork swaps too. And while I initially notice the difference, it's never threatened the basic rideability of the bike. Some people might be more sensitive though.

Uh, yes someone does make a part for that. It's a headtube extension rather than a crown race extension though.

https://www.eighthinch.com/headtube_extenders.html

Not recommended for off road riding though.

Terrible advice.

1- unless you have a friend who owes you a favor, the minimum cost for any machine shop work is $35-75 depending on where you live.

2- it isn't only about a simple sleeve. It has to be toleranced closely to provide a crown seat and tight fit against the fork column, otherwise the bike will have a permanent loose headset, so to speak.

3- the now greater bending stress will be higher on the column than the fork was designed for, creating a serious risk of catastrophic failure.

This kind of non-thinking advice isn't surprising from a rank amateur, but I'm very disappointed to see it coming from someone who purports to be an experienced professional mechanic. In that capacity your role should be to discourage sloppy, dangerous home repairs rather than encourage them.

To the OP- either install a standard fork and live with the changed geometry, or buy a reasonably priced suspension ready fork properly built for this kind of service.

We used to make things in this country , pay each other decently.
now its only weapons that will pay enough to get the congress to site one of those plants in their district.
and thats all tax paid for..

Yeah I have seen those, but reinstalling the crown race is a more delicate operation and I'd rather risk ruining the fork than the frame.

I could also just get a headset with a bigger stack height, but, again, I'd rather work on the fork than the frame.

+1 on the warnings. It is not a trivial issue. I would look for a fork that has the equivalent CR to Axle distance as your suspension fork with sag has.
I have a 97 RockHopper that was offered with suspension. But this one was rigid. Here is a pic that demonstrates that there are forks that have the distance built in so the frame could be the same for suspension or not. The tires are 2.1 x26, note the clearance:


I mounted fenders on this set up and had to make an extension to mount to the fork!

regarding crown seating tolerance if one were to design a sleeve....

Suppose you use a cartridge bearing with a split-ring crowns? So, tolerance wouldn't matter as much since it will compress...

How much do you need? Most rigid forks now are suspension corrected.

This would get you a little extra if you don't need much.

https://www.jensonusa.com/store/produ...s+Headset.aspx