Can you convert from a front shock to regular fork?

[johnnybentwrench]

Hi, I was wondering if I can take the shock out of a 1992 Trek 990 and put a fork in it. Are the bike frames with front shocks different from the ones that do not have a shock?

[Uncle Grumpy]

Short answer to the first question: yes.

Short answer to the second question: no.

Now the longer version.

We could talk all day about geometry and how the axle to crown length influences geometry, but that's not really going to help get you setting up your Trek. Generally speaking, a bike that runs a suspension fork can run a rigid fork, there's no real difference in how the frame is made, though some bikes that run a slacker head angle might have gusseting and the like. Again, that's not really going to help you solve your problem.

The two thi... three things to consider are the headset type, headset steerer size, and axle to crown length.

Firstly, you need to make sure you get a fork that is compatible with your headset in terms of whether it is threaded or threadless. If your stem has a quill that goes inside the fork steerer then it's threaded. If the stem slides over the steerer and clamps around it, it's threadless.

Secondly, is it 1" or 1 1/8". I'm going with 1" but I don't know every detail of every bike ever made so someone else can fill in that gap.

Oh, crap, there's four things...

The one I forgot, is the length of the steerer. You need to ensure you have enough length in the steerer of the new fork, and enough thread if you have a threaded system. Taking measurements off your current fork is a good thing.

Finally, the axle to crown, as in the distance from the hub axle to the crown of the fork. Getting something close to what you have now will keep the geometry and steering similar. You be the judge if you want a shorter axle to crown for quicker steering or a longer one for a more laid back feel.

Hopefully that gets you started. Anything else you need to know, holler out.

Grumps

[johnnybentwrench]

Thanks. I will google Axle to crown. I found a seller on E bay with a lot of older trek forks. I still have to check what size the stem is on my bike. Looks like nothing but the handle bars were changed out on the bike everything else including the rubber hoods for the brakes are there. Thanks again for the help and info. I don't really know about mountain bikes. John Los Angeles

[CCMDoc]

If its a 1" steerer, there's a young woman on this forum who is looking to swap her rigid fork for suspension a few posts down.

You might want to PM her.

[Drummerboy1975]

There's actually five things to consider. I ran into very issue on a Rckhopper I was going to do the same swap on.

Brakes. Yes, you will need to figure out what to do with your brakes. I'm guessing you have center pull brakes in the bike right now. Well, when you change over to a rigid fork, will you be able to run the same brake set you? Probably not because with the rigid fork, I doubt it will have anyway of hold your brake cable in place.

Something to look into. More than likely you will have to run side pull brakes.

[Andy FitzGibbon]

There's actually five things to consider. I ran into very issue on a Rckhopper I was going to do the same swap on.

Brakes. Yes, you will need to figure out what to do with your brakes. I'm guessing you have center pull brakes in the bike right now. Well, when you change over to a rigid fork, will you be able to run the same brake set you? Probably not because with the rigid fork, I doubt it will have anyway of hold your brake cable in place.

Something to look into. More than likely you will have to run side pull brakes.

Cantilevers work fine with rigid forks. Just get a headset cable hanger and you're good to go.

[hegstad1]

The 1992 990 frame is the same as the 970,950 and 930 frames which all came with rigid forks. That is to say, the 990 was not suspension corrected and can easily be switched to a rigid without changing the geometry. The 950 (which I have) and the 970 came with a 1 1/8 inch threaded Tange Big Fork. Forgive me for "outing," but there is currently one on Ebay which is the exact one that would fit this frame.

Tange Cro Moly MTB Bicycle Fork 26" 1 1 8" Steerer Tube Diameter 146 mm Purple | eBay

[johnnybentwrench]

The frame is 21" It looks like the steering tube is 165
I was looking at this fork. I know it is not correct for the 990 but if it will work thats ok

Trek CrMo Bicycle Cycling MTB Fork 26" 1 1 8" Steerer Tube Diameter 165 Mm | eBay

[girlonbike]

Just an FYI - outings of auctions are generally frowned upon but it looks like you need a lot of help and you're getting somewhere so try to keep that in mind. Good luck and enjoy.

[johnnybentwrench]

Sorry, I did not know. Thanks

[yo-Nate-y]

If the steerer length is right for your frame size, you should get the fork Hegstad linked to.

If someone swapped your headset for threadless/ahead when they put the suspension fork on, you'll also need a threaded headset. Tange Levins are super cheap and work great.