Overweight out of shape guy looking for some help. I may be purchasing a Trek 820 or Trek 3500 bike and they both come with the following fork: SR Suntour M-3030, coil spring, 75mm travel. At my weight (325) and fitness level (beyond pathetic), a suspension fork is the last thing that I need.

I want a rigid fork. What do I need to know and how do I find out what specs to look for in a rigid fork? I want it to have at least as long (if not longer) steerer tube than the stock fork. I am fine it the new fork is made from steel (or whatever else).

What are some brand names of forks that I should consider. I realize that these are low end bikes, so I'm not looking to break the bank on a fork. I just need a stury one for my weight.

I would suggest a fork from Surly in the appropriate style and size. Forks | Parts and Accessories | Surly Bikes
They come in suspension corrected version so your geometry won't be changed.
You should also measure the offset on the current fork, The distance from the center line of the steer tube to the dropouts and match it as close as possible.

Another possibility: Buy something suitable as it comes, not something that immediately has to be modified.

Ok, there are 4 types of common forks.

1" Threaded (several different threads)
1" Threadless
1 1/8" Threaded
1 1/8" Threadless (most of the MTBs and hybrids, even road bikes in the last 5 to 10 years).
(plus some more custom tapered forks, especially with carbon fiber bikes).

Oh, are you buying new or used? As HillRider mentioned, it is ambitious to buy a new bike and do major changes immediately. A used bike? There are a lot of good used non-suspension bikes available, but you have less money invested in the bike, and have to take what comes along.

Also at least or local co-op has a whole wall of battered MTB forks. Something would surely fit. Do you have a local bike co-op or bicycle recycler?

Buy a bike that comes with a rigid fork.

I like the idea of a bike already with a rigid fork. Can you suggest some entry level mtn bikes that have a rigid fork? Or are older bikes my only choice when it comes to mtn bikes? Seems like most new ones come with suspension without lockup. I was wanting a mtn bike, but I see that Trek FX 7.1 and 7.2 come with a rigid fork. any other suggestions. I live about an hour north of Atlanta. I would guess that Atlanta has some co-ops.

FX 7.x series are not mountain bikes. They are hybrids. As you already know, Surly makes some nice all rounders that are suitable for roads and trails, such as the Ogre/Troll bikes.

You also might want to try the Salsa Fargo. Also check out the Kona Rove and Big Rove, both in Steel and Aluminum.

Not a mountain bike, but the Fairdale Weekender Archer might be perfect for what you are trying to do.

Now, get out and take some test rides.

Do you actually need a dedicated mountain bike or are you planning on doing mostly road riding and maybe some smooth dirt roads? A hybrid like the Trek's mentioned may be a better choice and already supplied with a rigid fork. Don't rule out looking for used either. Plenty of lightly used hybrids out there at 2/3-1/2 the cost of a new one.

What sort of riding are you planning on doing? Do you actually plan on riding "off road", or are we talking road / cycle path riding here? If the latter then I would highly recommend you consider a hybrid bike like the Trek 7.1/7.2. Even if you're riding gravel paths, a hybrid will do the job.

I would guess yes that most of my riding would be on pavement in the outstart. Due to my fitness level, I won't be able to do much whether it's pavement or dirt.

I will be riding some sidewalks (no one ever walks on these sidewalks) and it's always rough around the man hole covers b/c the pavement is always at several different levels. On a road type bike, it can be an unpleasant jarring experience and these areas occur every several hundred feet. So, part of the desire for wide cushy tires comes from just riding those areas. I do have some trails within a reasonable distance from home.

In a nutshell, I just want a relatively inexpensive bike that I can keep in the truck and ride when the opportunity presents itself no matter where I might find myself. So, I'm kind of leaning towards a mtn bike, but I realize the FX bike could serve the purpose and it already has a rigid fork. Since none of the entry level mtn bikes come with a rigid fork, seems like my best bet is an older used model.

When I inquire at the Trek stores about a replacement rigid fork, they give me the price range of $75 to $100, but I want to see a picture of what would work. If it would make the bike look hideous, then that may change my mind totally. I just don't know how to figure out what measurements that I need to take into consideration when looking for a rigid steel fork for the 26" wheels. I know the stock one has 75mm of travel, but that's about all I know.

If you go ahead and purchase a bike with front suspension and then change it out for a rigid fork (which, as stated above, seems silly) the Trek dealer that quoted you those prices for a rigid replacement should be able to provide something suitable.

As noted, a rigid fork hybrid will certainly meet your need and they come with larger, lower pressure tires than road bikes so they will also soften the bumps.

Many high-end suspension forks have a lockout feature.

Although, if you don't need the suspension, then here is no reason for all that extra weight and complexity.

I keep making suggestions for some bikes to check out that are better options than a heavy, slow mountain bike. Forget about a mountain bike, unless you want to pick up a used one for $100 and try to make it work for awhile.

Fairdale Weekender Archer (or something like it). Ticks off all your boxes.

Wide, 42 mm tires, should soak up those bumps.
Cro Moly Steel frame and fork for a forgiving ride.
Upright riding position with swept back handlebars.
Retail price under $900
Relatively simple 1 x 9 drivetrain.
2016 Weekender Archer | Fairdale Bikes

Another one worth checking out is the Giant ToughRoad. Also under $900, aluminum frame and carbon fork, 3 x 9 drivetrain. Hydraulic disc brakes. Flat bars. (might want to change those out to something with a bend) And notably, HUGE 29 x 2" tires, which is 50 mm. that would really soak up the bumps in the pavement without the headache of a heavy, energy robbing suspension fork.ToughRoad SLR 2 (2016) | Giant Bicycles | United States