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Discussion Starter · #1 ·
I have worked on plenty of bike when i was a kid...a long time ago...and I have been back into biking for a year or so, now my "entry level" trek 3700 needs a new fork.

the stock rst doesn't do much with my 200 pounds on it. so when i buy a new fork, what dimensions do i need to look at?

my bike has a 22.5" frame and has a freakishly long head tube, so does the steerer tube need to be extra long or is that a factor?

anyone who has some info on this please post even if you think it is something worthless. also, could someone run through the process real fast of what bolt does what on the stem,

I take it that the one vertical bolt adjusts the tension on the headset bearings, but will that also drop the fork if it is removed, and are the bearings loose or are they "caged"?

and the two horizontal bolts...are they only used to hold/align the stem?

and since this is a hardtail...how much travel should i look for?
thanks
 

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The head tube shouldn't be so big that a regular fork won't work but when you decide on a fork, just check the steerer tube length. Once you have that just add up the stack height of your headset and the height of your stem and see if there will be enough room. Most new forks need to be cut down so you should be fine but it never hurts to check. When everything is in place the edge of the steerer tube needs to be a few millimeters below the top of the stem to allow for tightning. I usually will leave the steerer a little long and use spacers at the top in case I change to a stem that happens to be bigger or a frame with a larger head tube.

The vertical bolt does just tighten the headset bearings. If you loosen it the fork will not fall out though. The two or more horizontal bolts are the "pinch" bolts with actually clamp the steerer tube. The pinch bolts are the ones that hold everything in place once you set up your bearing preload with the vertical bolt.

Travel wise, you can run anywhere from 65mm of travel to 150mm if you want. It depends on your riding but for most riding I would suggest 100-130mm. If you just ride light duty XC than you could go with 80mm of travel.
 

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Discussion Starter · #3 · (Edited)
ok, does the stem clamp onto the steerer tube?...my head tube is 7 and 1/4 inches long... from the bottom edge of the headtube to the bottom of the stem is a little over 9 inches...

will this be a problem with buying a used fork? the bike only cost 250 new so i dont wanna sink a lot o cash into it.... i plan on getting a fs in the future....

oh..and does anyone know if my steerer is a 1" or a 1 1/8 inch? next i'll be asking if somebody will come and install it for me...lol

thanks
 

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Formerly DMR For Life
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pretty much garentee that its a 1 1/8th steer....yes your stem clamps onto your steer tube

measure the length of the steer tube on your current fork and when your looking for a used fork check to ensure that the steer tube is that length or longer

one note when your changing your fork you will have to remove your crown race which will sit right against the crown of your fork...with some paitence you can do this...but can be done fast by someone at your LBS

DMR
 

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In choosing a new fork's travel spec you need to think about what your current frame was intended for. Your frame according to Trek comes with a 63mm travel fork, so I'd look in the range of 63-80mm travel forks; I'd say going over that with most forks could cause your bike to handle poorly; no more than 100mm in any case IMO. There's a measurement called axle to crown height that you can use to compare forks; you might be able to get a recommendation from Trek.

You'll need tools to install your crown race as well as the star nut on your new fork; while you don't need the specialized tools made for this purpose, they do make the job easier. If you buy your fork from a local lbs I'd say they'd do the installation for you very reasonably. Review tools & procedures on a site like parktool.com or sheldonbrown.com; you can search for some diy solutions here in mtbr too.

I'd second the recommendation that you check your steerer tube requirements before fork purchase, while most new forks should come with adequate steerer tube, it's a good idea to be sure. Most used forks will probably have had their steerer tubes cut too short. Be sure to account for your headtube, headset stack height and spacers needed in calculating measurements.

Your headset has semi-cartridge bearings according to the Trek website.
 

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Discussion Starter · #6 ·
as far as the handling is concerned, my head angle is a little steep, how would the increased travel affect this? would it most likely

a) increase the ride height and get closer to the stock angle as the fork is compressed(this would be ok as a little more slack would be cool)
b) keep the same ride height and form a steeper headtube angle as the fork compressed, due to dropping the front of the bike(this would be not so good, like i said the angle is kinda steep)
thanks for all the info guys...
 

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Ok.

Top nut is for headset.

Horizontal bolts are often called pinch nuts because they pinch the steerer and hold the stem in place. They must be slightly loose to adjust the headset or you'll damage your headset or starnut.

Oh, and I recommend getting a headlock when you get the fork. Much better than a Starnut.

Get an Answer Headlock and you're ready to rock and roll. I run one on my BMX bike and I'm going to get one for my MTB.
 

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crown race, etc

if i get what i think you're asking, if you go with 100 mm travel, for instance, instead of 63 mm, your ride height will be raised up quite a bit, making the bike harder to control. this can be somewhat compensated for by increasing the sag on the fork so its partially compressed when you're sitting on the bike, but this also then limits the travel of the fork. bottom line: go w/ probably an 80 mm fork; if you get a good quality fork like marzocchi or maybe manitou, you'll get plenty of effective travel, it won't bottom out, and you won't compromise your handling as you would with a 100 mm fork

also, a tip for your crown race if you're doing it yourself: you'll have to use a small flat bladed screwdriver to tap between the crown race and the crown of the fork to remove it, working around the race and being sure not to damage the smooth bearing surface. then, to put the race on your new fork, simply put the entire fork in the freezer (do this when wife/girlfriend is not around!) for about 30 minutes. then, use wife/girlfriend's hair dryer on high to heat up the crown race itself for about 2 minutes (hold w/ a pair of pliers so you don't burn your hand). then, take the fork out of the freezer and slide the crown race onto the fork; as the metals heat up/cool down, the race will tighten on the fork. ain't science amazing?!?
 
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