Rigid replacement for a 100mm sus fork- Mtbr.com
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  1. #1
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    Rigid replacement for a 100mm sus fork

    I'm riding a 1x8, but I figured I'd post this here because y'all seem to discuss rigid forks a lot more.

    I recently bought an old Kona Blast with a crappy 100mm suspension fork with a 470mm a-c. I can't afford a decent suspension fork right now, so I bought a used Vicious Cycles 438mm a-c rigid fork. I haven't tried it yet, but now that I've researched more it seems that even taking sag into account, the new fork will be about an inch too short and will steepen the head tube angle by one degree.

    I'm thinking the bike is already too slack as it is, but it's hard to tell because I've never ridden a suspension fork before. Ultimately, I guess I'll just have to try it and see how it works, but I'd like to hear some opinions.

    Is this an acceptable amount of frame angle difference? How much would a bigger tire help? I'm running 1.9s now. Do you think I'd be better off sticking a 29" wheel up front, making it a 96'er?

  2. #2
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    Well, if you think that the bike is too slack as it is then a shorter fork to steepen up the angles might be just what it needs?

    With the 470mm suspension fork you probably be running at least 20 -25mm of sag, so the difference between that and 438mm isn't in my opinion worth worrying about. Plus any suspension fork will compress even more under braking, rolling off a step etc. (steepening the head angle right when you don't need it). This is often overlooked when comparing fork lengths - your 438mm rigid fork is always that length whereas the 100mm travel 470mm fork might get as short as 370mm. Think what that does to your geometry.

    By all means try a 29er front wheel - I'm thinking of doing just the same.

  3. #3
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    Maybe a 29er fork with your current wheel? Surly Karate Monkey fork is 468 mm, for example, and can usually be found cheaply on eBay or whatever. As long as you are running disc brakes it should be OK.

    I wouldn't go with a 29er fork and wheel, that would really jack the front end.

    Like Andy R said, a shorter fork should actually un-slacken the bike.

  4. #4
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    Quote Originally Posted by anthony.delorenzo
    Maybe a 29er fork with your current wheel?
    I wouldn't go with a 29er fork and wheel, that would really jack the front end.
    You'd have plenty of room to get a 29" front wheel in the fork that you have - depending on tyre sizes that will lift the front maybe 30-35mm, so will slacken your angles by a degree and a half, hardly any different to using a 468mm 29er fork with a 26" wheel.
    If you were going to do either I'd go for the 29" wheel in the forks you have, but don't get too hung up on angles anyway. My experience is that you soon adjust and ride the bike for how it is.

    If you decide not to use the Vicious Cycles forks you can always sell them to me

  5. #5
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    Well, I got the fork today and got it installed and took it on a run through the woods across the parking lot. It sure climbs and steers a lot better than with that cheap mushy suspension fork! But after only a few hundred yards of semi-rough stuff my shoulders and elbows were aching a bit... better now after a scotch and a beer.

    Part of the problem may be that the steerer tube is cut so short that I don't have room for any spacers, so my position is a bit forward, plus the geometry is a little steeper... and I'm pushing 40 yo and haven't ridden off road in more than 20 years, lol. The skills are still pretty much there, but my joints doth protest... maybe if I stick some BMX bars on this bad boy....

    Ima take it to the local single track and see how I feel after 5-10 miles, but I have a feeling I'll be saving up for a nice suspension fork.

    Thanks for the input.

  6. #6
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    Quote Originally Posted by middy
    But after only a few hundred yards of semi-rough stuff my shoulders and elbows were aching a bit... better now after a scotch and a beer.

    Part of the problem may be that the steerer tube is cut so short that I don't have room for any spacers, so my position is a bit forward, plus the geometry is a little steeper... and I'm pushing 40 yo and haven't ridden off road in more than 20 years, lol.
    Ima take it to the local single track and see how I feel after 5-10 miles, but I have a feeling I'll be saving up for a nice suspension fork.
    Your arms and shoulders will get used to it, but I agree - what you can't do much about is a too short steerer tube. I take it that you are using riser bars, 'cos if not, that obviously would make a difference.

    I was serious about buying the Vicious Cycles forks if they don't suit you, but I'd need a steerer of 195mm minimum so possibly they'd be cut too short for me as well.

    Pushing 40 eh?- you poor old soul.........I wish that's all I was but unfortunately I can add another 20 onto that.

  7. #7
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    Yeah, I'm using risers already. It isn't too bad, about an inch below my saddle.

    I feel fine this morning, so I'm sure I will get used to it. I sure enjoyed the solid tracking of the vc forks and they're obviously well-made. Plus my bike is sooo much lighter!

    We'll see how I feel after a few laps around a real trail... I'm feeling a little younger for some reason.

  8. #8
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    Quote Originally Posted by middy
    Yeah, I'm using risers already. It isn't too bad, about an inch below my saddle.

    We'll see how I feel after a few laps around a real trail... I'm feeling a little younger for some reason.
    Sound ideal, mate - enjoy it !!

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