1. The most important thing about buying a new bike is to make sure it fits. The only way you'll know if the bike is right for you is to size up the bike and make sure that the bike's geometry matches your body's geometry. Ask questions and do some research.
mtn. biking 101
2. If possible, try to find a shop that will let you demo the bike on real dirt. Five minutes in a parking lot won't cut it. You wouldn't buy a car without a real world test drive, and a bike should be no different.
3. Don't belive the hype. Just because your favorite rider or best friend rides a certain bike, that doesn't mean that's the best one for you. Have an open mind and be realistic about your needs and ability.
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  1. #1
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    Hi, I don't know anything!

    So after spending my teen years freestyling on Haro's and Redline's, I'm finally back in the saddle. This time its on a Mountain bike. I always had a costco Mongoose bike that weighed a ton but was a PIA to ride. So I did some quick searching on Craig's List and was able to land this Trek 4900 for $100



    Its fork was stolen but other than that, it looks to be in really solid shape. I got it home and took the fork off the mongoose, thinking that it would be a simple swap. For the most part it was pretty straight forward but the shaft leading up the frame to the handle bars was about .5" too short. Getting past the first tightening bolt on the handle bars it didn't quite make the second.

    I got everything tightened up and went for a ride. It held up great, cautiously I hit the trails and started to gradually push it. No problems at all. I know its not ideal so I started looking for a proper replacement, again on CL. This time I found this listing
    Mountain Bike Suspension fork

    Its for a rockShox fork and the stem is 8.5" which seems like the perfect size after I took some quick measurements. So, basically I'm looking for some direction, thanks for the help.

  2. #2
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    Did that person paint the stanchions on that Rock Shox Fork? I havent heard of any rock shox forks that had black stanchions other than a Boxxer and that is not a boxxer.

    Looks like someone might be trying to rip others off.

  3. #3
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    I would recommend waiting until you get a fork with the right size steer tube before riding that bike again.

  4. #4
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    Pics of the fork installed?
    If the steerer is too long you can cut it, if it's too short it no worky.
    Round and round we go

  5. #5
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    This is what it looks like right now. Honestly its pretty solid. The steer tub is between both tightening bolts on the handle bar neck. I know that ideally I would want it all the way to the top but I'm having trouble figuring out how long it should be. Is there a way to determine the size fork I need?


  6. #6
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    It should be a few mm shorter than the top to leave room for the top cap to tighten/load the bearing. It should also be at least long enough to reach the center of the top bolt on the stem.
    Maybe a stem that's not as tall on the steerer?
    Round and round we go

  7. #7
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    Are you riding somewhere that you need a suspension fork? If not, you'll get a better rigid fork for the money.

    If you still want a suspension fork, this is what you need to know:

    steerer tube length- measured from the top of the fork crown to the top of the stem. You can always cut the tube or add spacers if it is too long. tube also needs to be straight, not tapered. Not threaded.
    correct travel- should be 80-100mm, from what I've read. I would just get 100mm.
    brakes- has posts for those brakes.

    I see a few new ones on ebay that would work. $75 and under.

    Not sure what year your bike is, but this is probably close. This site is great for info on older bikes:
    2003 Trek 4900 - BikePedia
    Quote Originally Posted by Fuglio View Post
    You guys suck im all bummed now

  8. #8
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    If you have any spacers you could add an inch or so to the length of the steer tube that is in the bike now. Then you could take up the extra space with the spacers / rings. if you dont have any you could always cut down the steer tube on the new fork. I ussualy cut my steer tube so it is about 1/32 short of sticking through the top of the stem. This way I can pull everything tight.If the fork / bike is new to you, you may want to leave the steer tube long and take up the extra space with spacers that way you can ride it around to see if you want the bars left high or not. Then you can take out a spacer and put it on top of the stem to see if you like it better with the bars lower. This will allow you to change the height without cutting anything.

  9. #9
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    Quote Originally Posted by NEOHIO Ray View Post
    If you have any spacers you could add an inch or so to the length of the steer tube that is in the bike now.
    What spacers are you referring to?

    edit: disregard. It sounded like you were saying there are spacers that can add length to a steerer tube. I get it now.
    Quote Originally Posted by Fuglio View Post
    You guys suck im all bummed now

  10. #10
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    Thanks for your help guys. The steer tube I have on there now is from a Mongoose and its too short, about .5" too short I would say. I have to re-measure it but from the last time I measured it it was 8.5" exactly from the very top of the Adjusting cap, bolt to the bottom Fork Crown race (I'm picking up some terminology, watch out hahah). With that info I tracked down the CL post above.

    Also, according to that BikePedia page, the bike is a 2004 model. Which is really surprising because the guy I bought it from said it was a couple of months old and it looks like it.
    2004 Trek 4900 - BikePedia

  11. #11
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    Also if you are getting a used fork, make sure there is a star nut inside (that is what the top cap tightens down to) and if youneed to shorten the steer tube, make sure you push the star nut down at least 1/4" below your cut line. The star nut can be push in by gentaly taping on it with a socket that is slightly smaller in diameter than the steer tube and a hammer. (gentaly tapping) and dont go to far or you will need to push it out the other end and reinsert it, or get a new one. they are cheap though. Last thing, always reserch itmes on CL before you buy, bike pedia is very good for figuring out the year of a bike as mentioned above. Most bike manuf. change color and compenets year to year.

  12. #12
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    Thanks for the tip. Do you know of a good online place where I can buy parts from?

  13. #13
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    I ussualy buy stuff on ebay, however I have bought stuff from wheelworld. There are alot of online retailers that are mentioned on here like jenson, blue sky, and nashbar. They all seem to be pretty go on prices.

  14. #14
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    Quote Originally Posted by theMeat View Post
    Maybe a stem that's not as tall on the steerer?
    Cheapest and quickest fix right there - find a stem where the end that clamps to the steer tube is lower than the one on there now (which looks pretty tall). Bring the whole bike to the LBS and do a side-by-side comparison, maybe a test fit. Make sure you get the right stem for you handlebars if you go this route - a lot of newer ones are made for larger dia (31.8mm) bars.
    Hell, a BMX stem might even do the trick if you've got any around that are new enough to be threadless style.

  15. #15
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    Hi, I don't know anything!

    Quote Originally Posted by NEOHIO Ray View Post
    If you have any spacers you could add an inch or so to the length of the steer tube that is in the bike now. Then you could take up the extra space with the spacers / rings. if you dont have any you could always cut down the steer tube on the new fork. I ussualy cut my steer tube so it is about 1/32 short of sticking through the top of the stem. This way I can pull everything tight.If the fork / bike is new to you, you may want to leave the steer tube long and take up the extra space with spacers that way you can ride it around to see if you want the bars left high or not. Then you can take out a spacer and put it on top of the stem to see if you like it better with the bars lower. This will allow you to change the height without cutting anything.
    His problem w the current fork is the steerer tube is too short. There are no spacers that extend the length of the steerer tube.

    You add spacers between the headset and the stem to adjust the bar height. You add spacers above the headset to ensure that you have the correct bar height dialed in. Once you have it dialed in, you cut the steerer tube to 5mm below the top of the stem and remove the spacers.

    OP: I hate to tell you this but you probably wound up with a bad purchase. You can find a rigid fork that will make the bike functional. Buying a used suspension fork is a crap shoot. Chances are you'll need to add $50- $100 to the CL price for a used for to buy a rebuild kit or have a shop rebuild it for you.
    JPark - 3.5- don't listen to dremer

  16. #16
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    I wast saying there are spacers to extend the steer tube. I was saying he could add 1 inch or so to the steer tube that is on the mongoose fork to base his new purches on. Once he buys a new that lets say is now 9.5" lg because he siad his steer tube us 8.5" and he siad that one is too short. Sooooo now that he has a new fork, if the steer tube is too long he can then add a spacer below the stem or above it to make it fit correctly.

    Also hiw can you say he made a bad purchase, the orignal msrp was around 500$. It us missing the fork which can be bought for 150$ tops on ebay. That is 250$ total in the bike. Maybe a little more if he wants a new seat. Why does everyone think you have to spend a grand on a bike to be able to have fun and enjoy riding.

  17. #17
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    Hi, I don't know anything!

    Quote Originally Posted by NEOHIO Ray View Post
    I wast saying there are spacers to extend the steer tube. I was saying he could add 1 inch or so to the steer tube that is on the mongoose fork to base his new purches on. Once he buys a new that lets say is now 9.5" lg because he siad his steer tube us 8.5" and he siad that one is too short. Sooooo now that he has a new fork, if the steer tube is too long he can then add a spacer below the stem or above it to make it fit correctly.

    Also hiw can you say he made a bad purchase, the orignal msrp was around 500$. It us missing the fork which can be bought for 150$ tops on ebay. That is 250$ total in the bike. Maybe a little more if he wants a new seat. Why does everyone think you have to spend a grand on a bike to be able to have fun and enjoy riding.

    Got it. You're 100% correct. My bad.

    Bad purchase: he paid $100 for a 10 year old bike. He'll pay $75 for a rigid fork or $150 for a used/rebuilt fork. He'll wind up with a $175-$250, 10 year old bike. Assuming that the rest of the components aren't brand new, I'd estimate that he has another $100 in parts (tires, bottom bracket, drive train) that he'll need to replace in short order.

    So now it's my turn to clarify: I never suggested that anyone needs to spend a bunch of money on a bike. I did say that this particular purchase, with very little research done, was impulsive and the op would have been better off spending $200-$300 on a complete bike. In other words, it's my opinion that this was a bad purchase.
    JPark - 3.5- don't listen to dremer

  18. #18
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    If the Mongoose fork fit as planned, and the frame is a fit, it would have been a good purchase. BB and other bits don't need to be replaced until they fail. I've got 25+ years on some of my bbs and no issues. Regardless this is all speculation and what shoulda and coulda talk. Think we're onto how to fix where we're at now.

    Now in a deep Barry White voice, What it was, what it is, and what it could be.

    You didn't mention reach/fit with that stem and height, is it good? Is the fork's sag usable ?
    Last edited by theMeat; 06-18-2013 at 04:26 PM.
    Round and round we go

  19. #19
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    I'm honestly surprised when I learned that the bike was 9 years old. It looks brand new, probably a couple months of use, tops. But, its done and I have it now. I have been looking on my local craigs list and have found some good deals on forks. The vast majority well under $100. What should I look out for when buying a fork? Can I compression test it by leaning down on it when I got to buy it? Or does it have to be mounted on the bike and ridden to get a sense if something is wrong?

  20. #20
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    Hi, I don't know anything!

    Quote Originally Posted by trek View Post
    I'm honestly surprised when I learned that the bike was 9 years old. It looks brand new, probably a couple months of use, tops. But, its done and I have it now. I have been looking on my local craigs list and have found some good deals on forks. The vast majority well under $100. What should I look out for when buying a fork? Can I compression test it by leaning down on it when I got to buy it? Or does it have to be mounted on the bike and ridden to get a sense if something is wrong?
    It's a crap shoot. You can compression test and look for oil leaking or air hissing (gurgling). Make sure the stanchions are smooth with no grooves or scratches.

    Very important:

    1. Every fork comes with a crown race. The race is the interface between the fork's steerer tube and the bike's headset. It's a press fit on the fork at the bottom of the steerer tube and the arch. You'll want to make sure the crown race comes with the fork.

    2. Steerer tube diameters are different. You want to ensure that the fork you're purchasing has 1 1/8" threadless steerer tube.

    You can also interview the seller. Find out why they're selling, ask about their other bikes, etc.

    You should budget extra money for a rebuild or rebuild kit. Prices will vary depending on the brand and model of fork.
    JPark - 3.5- don't listen to dremer

  21. #21
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    Great, thanks for the help.

  22. #22
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    Quote Originally Posted by Ken in KC View Post
    1. Every fork comes with a crown race. The race is the interface between the fork's steerer tube and the bike's headset. It's a press fit on the fork at the bottom of the steerer tube and the arch. You'll want to make sure the crown race comes with the fork.
    Just a quick correction - the crown race is a component of the headset, not the fork. A fork NEVER comes with a crown race, as they differ depending on make and model of the headset. You'll need to move yours from your current fork to any one you end up buying. People will swear this is a shop job, or you need specialty tools, but I've been changing them with a hammer and flathead forever and never had an issue. YMMV.

  23. #23
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    Hi, I don't know anything!

    Quote Originally Posted by slapheadmofo View Post
    Just a quick correction - the crown race is a component of the headset, not the fork. A fork NEVER comes with a crown race, as they differ depending on make and model of the headset. You'll need to move yours from your current fork to any one you end up buying. People will swear this is a shop job, or you need specialty tools, but I've been changing them with a hammer and flathead forever and never had an issue. YMMV.
    D'oh! You're right. Thanks for the correction. OP: you'll want to mail order a crown race for your particular brand/size headset. Size again is 1 1/8" threadless. Sorry for the wrong information.
    JPark - 3.5- don't listen to dremer

  24. #24
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    Is the Crown race specific to a particular frame or is it a universal fit? I have this mongoose fork on now and it seems to be sitting perfectly. I would leave if but the steering tube is just a little too short. That brings up another question, can i buy just a steering tube and pop out the star nut in the old shorter one and pop it into the new tube?

  25. #25
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    Hi, I don't know anything!

    Quote Originally Posted by trek View Post
    Is the Crown race specific to a particular frame or is it a universal fit? I have this mongoose fork on now and it seems to be sitting perfectly. I would leave if but the steering tube is just a little too short. That brings up another question, can i buy just a steering tube and pop out the star nut in the old shorter one and pop it into the new tube?
    It is specific to the headset: the headset is the press fit set of bearings on the top and bottom of the headtube (the part pf the frame that the steerer tube goes through). The brand is probably stamped or printed on the outside of the bearing cap (came creek, wtb, etc).

    There's not a whole lot to crown race. All it really does is aligns the fork with the headset. Short term, you have it pulled tight and its likely doing its job. But it would be a good idea for the long term to get the proper race for the headset.

    Most steerer tubes aren't replaceable or interchangeable. Some brands are an industrial press fit, some are welded or mechanically bonded in some sort of permanent fashion. Some oem's will replace them for you. Wouldn't hurt to ask in your case but its been my experience that you can get that type of service from higher end products (for a price) but not so much with the big box produced stuff.
    JPark - 3.5- don't listen to dremer

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