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  1. #1
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    Head Angle vs Wheelbase?

    For those who have read my last thread "Easy button didn't work" you know that I'm trying to find a frame that is a little longer and slower than my 16" 97 DB w/71.5* head angle. I noticed that as frames get bigger, they also get longer.
    I want a frame that is a little larger and slower steering than what I have now.
    I was hoping for a 70* head angle, but it looks like the light CF frames are almost all 71*.

    Will an 18" 71* frame be noticably slower handling than a 16" 71.5* frame?
    I know that an increase in wheelbase slows things a little, but will it be enough to notice?
    What I have is a little more twitchy than I would like, not bad but I would like to do better.
    Any suggestions from those w/experience on this? TIA

    R

  2. #2
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    The bicycle frame is the sum of its parts... or number.. or angles. It is not just wheelbase and head tube that makes how a bike behaves.

    Head over to the Frame Building forum as I believe they can explain things for you.

  3. #3
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    Impossible Question?

    The frame forum was even less help than this forum. I guess a straight answer is too difficult to come up with. I am aware that there many variables in a frame, I also know that all else being equeal that there are some rule of thumb tendencies.
    I will just have to wait for the right person to answer this most difficult and perplexing question. Thanks

    R

  4. #4
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    I skimmed your "Easy Button" post, and it's not clear to me... Why are you trying to slow down the steering?

    Have you considered other alternatives, such as a steering damper? It might be just the thing to stabilize your steering.

  5. #5
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    I'm not sure exactly what you are looking for, but CF frames are generally going to have steep head angles because they are usually intended to be racing (or at least racing style) bikes. Put a 120mm fork on them, and the head angle will be a little slacker (sort of). Or look for an older frame that was designed for 60 or 80mm forks and put an 80 or 100 on it. Obviously this will change the seat tube angle as well.
    You can slow your steering by going to a longer stem and/or wider bars.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  6. #6
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    I wasn't even thinking about a frame change until I did my OTH. What I have is not a problem, I just would like a little lighter, slower and better balanced. Why do I want slower, because what I have is a little more responsive than I like. I put a 100mm fork on my 97 DB, the R7 forks work great. If I can't have everything I want, what can I have and how much will it cost. Why does anyone change frames?
    If I'm going to change frames, I might as well get what I want! I don't have the experience to know what my options are.
    So, how would a 18" 71* frame compare to a 16" 71.5* frame everything else being equal?
    I didn't even consider a steering dampener!

    R

  7. #7
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    I wasn't even thinking about a frame change until I did my OTH. What I have is not a problem,

    - good to know its not the bike, going OTH is rider error.

    I just would like a little lighter, slower and better balanced. Why do I want slower, because what I have is a little more responsive than I like. I put a 100mm fork on my 97 DB, the R7 forks work great.

    - when you installed a longer length fork, you effectively altered the geo and handling.

    If I can't have everything I want, what can I have and how much will it cost. Why does anyone change frames?

    - someone buys a new frame when 1 - old one is busted 2 - newer technology 3 - different fit.

    If I'm going to change frames, I might as well get what I want! I don't have the experience to know what my options are.

    - these is where demoing or riding the ones you are interested comes in.

    So, how would a 18" 71* frame compare to a 16" 71.5* frame everything else being equal?

    - this is where it gets difficult - to find an 18" 71 deg and a 16" 71.5 deg to compare.

    Why don't you go to your LBS and get the same model on a size 16 and a size 18 from the same manufacturer and ride both. The .05 deg difference in head angle you are concerned will not decide if you will go OTH. Road bikes have far steeper head angles with no concern for OTH. If anything that will come out of this demo is the fact, how a bigger bike compares to a small one.


    I see they moved your original post from Frame Builders. Maybe if you just asked how to size yourself to get a neutral handling bike by giving your measurements.

  8. #8
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    I Thought I was Clear?

    OG. This is my first quality bike. In every post I have mentioned my desire for a more neutral handling bike. I have also stated my measurements. 5' 8", 31" pants inseam.
    In my trolling I notice that everyone seems to have their own preferance of fit and handling. The idea of test rides is good, but I'm wasn't sure where to start. Since my shoulder is trashed from my OTH, I won't be riding anything for a few weeks. I'm trying to get as much info as possible before I start shopping.
    I had never done a lock up panic stop before. I think a more neutral/balanced bike
    would be a little more forgiving, not to mention more comfortable. I'm sure someone has gone from a small frame to a larger one, hopefuly they will comment?
    When I added the R7 forks, I wasn't sensative enough to notice the difference in handling.
    I did like the smoother ride! I think I will go to a larger frame regardless. I want to be happy w/results, so I'm doing my research/homework.
    Thanks for something constructive. The benifit of others experience is invaluable!

    R

  9. #9
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    Quote Originally Posted by Ricisan
    OG. This is my first quality bike. In every post I have mentioned my desire for a more neutral handling bike. I have also stated my measurements. 5' 8", 31" pants inseam.

    - to size you up better, body measurements includes: arms length, shoulder length, torso length, thigh length, knee to foot length, proper inseam length and height. This will give you proper standover, top tube, stem length, handlebar width (road), saddle height, saddle position, crankarms length etc.. among other things.

    Is this necessary? not really. As long as you feel comfortable ( not stretch out, not cramp, have good standover, and bike feels easy to maneuver but not nervous. In short you feel good riding it.

    If you read too much about bike sizing without actual riding, it tends to confuse and what happens is you might over analyze theoretically.


    I had never done a lock up panic stop before. I think a more neutral/balanced bike
    would be a little more forgiving, not to mention more comfortable. I'm sure someone has gone from a small frame to a larger one, hopefuly they will comment?

    - a smaller than your proper size bike is doable but it will feel feel twitchy to a less experience rider. Conversely it will feel nimble and more flickable to an experienced rider.

    I have a size 15 and a size 16.5 Merlins. The size 15 has a drop of 2 inches from saddle to handlebar because of the limitations of the stem. This puts me in an aero position and my weight more on the front wheel. The size 16.5 puts me in a more upright position as the bars can be the same height as the saddle or even higher. It has a roomier cockpit as the top tube is longer which I compensated with a shorter stem. The 16.5 is more stable however the 15 feels more agile, quicker. The 15 was my first mountainbike 18 years ago and served me well. The 16.5 I bought on closeout sale 5 years ago and at my age feels more comfortable to me now.


    Thanks for something constructive. The benifit of others experience is invaluable!

    R


    Glad I answered some of your questions.

  10. #10
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    Wheelbase Measurement?

    As a continuation of my homework/research, I was browsing the CF frames on Ebay.
    I noticed the 18" frames have a 1047mm wheelbase. Using 1in = 25mm, the frame has a 41.9 in wb. The 16" frame I am thinking about replacing also has a 41.9 in wb. WTF!
    If I can't have a more relaxed steering, at least I can expect is longer wb?
    Did something get lost in the translation? I just measured my 97 DB frame. The R7 forks have the axel "extended" a little 1/2" past the fork tubes. WB is about 42.5.
    How can a longer frame have the same wb? I don't get it? TIA

    R

  11. #11
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    one inch = 25.4mm
    larger sizes of the same frame will have longer wheelbases
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  12. #12
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    Somebody is Wrong?

    TV: I would agree w/you ordinarily. From their website:
    For the18" frame WB is 1062=41.8" 1in=25.4mm
    Not only that but all chainstays are the same?
    The Top Tubes measure 16"-22.1 18"-22.6 20"-23.6
    WB is: 16"-41.1 18"-41.8 20"-42.4
    Is there something wrong here? Frame geo is not my field, but this does not look right.
    Their 16" CF frame has a TT 2" longer than my 16" frame, but .8" less WB?
    From 16"-20" the TT only changes 1.5"?
    Are their numbers wrong or do they have an unusual idea of what handles?
    Somebody please explain this in simple terms. Help

    R

  13. #13
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    Quote Originally Posted by Ricisan
    TV: I would agree w/you ordinarily. From their website:
    For the18" frame WB is 1062=41.8" 1in=25.4mm
    Not only that but all chainstays are the same?
    The Top Tubes measure 16"-22.1 18"-22.6 20"-23.6
    WB is: 16"-41.1 18"-41.8 20"-42.4
    Is there something wrong here? Frame geo is not my field, but this does not look right.
    Their 16" CF frame has a TT 2" longer than my 16" frame, but .8" less WB?
    From 16"-20" the TT only changes 1.5"?
    Are their numbers wrong or do they have an unusual idea of what handles?
    Somebody please explain this in simple terms. Help
    R
    Posted sizing/geo information is not always accurate. Different manufacturers sometimes measure differently, and I've seen plenty of measurements that are just plain wrong. Plus, there are TT measurements and ETT (Effective Top Tube) measurement. Today, ETT is used mostly because of sloping top tubes. ETT is measured as a level line from the center of the top of your top tube to the center of your seatpost. But also, the actual fork used can change head tube angle, seat tube angle, standover, and wheelbase. You generally don't know what fork they used to determine these, or whether or not they incorporated fork sag into the equation.

    A custom builder can give you anything you want, but my opinion based on your posts is that you are getting a bit too carried away with head tube angle and wheelbase. You should be looking for a frame that fits and is designed for the type of riding you do. The reason almost all XC rigs have similar head tube angles is that after a few decades of building XC mountain bike frames, the manufacturers have figured that to be the optimal setup for most XC riders. If you look at all-mountain frames, you'll find a little more relaxed geometry. Downhill/freeride, even more relaxed geometry. At your height and inseam, I think you should be on a 17"-18" frame for XC riding. Your 16' frame is probably too small for you, but that's probably not why you went over the bars. Going over the bars is generally rider error. One degree of head tube angle change or one inch longer wheelbase probably would not have prevented your accident. Unless you want to ride downhill geo for XC riding (not a good idea) you need to learn to get your weight back when you break.
    Warning: may contain sarcasm and/or crap made up in an attempt to feel important.

  14. #14
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    I'm a Spaz!

    TV: None of what you said is a surprise, it was expected.
    I'm new to biking, but I learn fast. I lurk a lot. lol
    I was hoping to get the info I wanted the "easy" button/cheap way.
    My friend and I ride about 1K each riding season on back roads and bike paths.
    The worst I stress my bike is off/up big curbs, I can't even bh. Nothing tech for me.
    The less than perfect Chinese CF frames are stronger than I will need, I hope.
    My 97 DB frame is ready for replacement. I'm trying to make an informed decision w/my limited experience. Solid accurate info, I won't get. I would like to do this right the first time. I'm trying to follow The 7 Ps.
    Proper, Previous, Planning, Prevents, Piss, Poor, Performance!
    I think that I'm just going to have to trust in basics. That a 18" 71* XC frame is a touch slower than a 16" 71.5* XC frame, and a little lighter.
    In spite of my need for reassurance like a child, I think I can do this.
    You were the dose of reality that I needed. I have been know to put things off waiting for more info or a better deal, till the chance had passed.
    Now I know, time to get going.
    Thanx

    R

  15. #15
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    My experience

    First everything I have or have had has at least claimed to be 71 degree with the fok that is was originally designed for.

    That said I have a Psycle Werks Wild Hare and a SC superlight right now. They both claim to be 71 degree but there is no doubt that the longer top tube on the Psycle Werks feels more stable in the steep and rough. It could also be that the Psycle Werks suspension sags a little more. BTW both bikes have identical 100mm Marzocchi Forks.

    If you are light enough (less than 165) and if you buy a bike with descent head tube support you could get a more relaxed front end by running a slightly longer fork. Say a 120 instead of a 100. You just have to take into consideration the xtra stress the longer fork puts on the head tube junction

    Finally if you have the $ some of the CF 'trailbikes' have slacker head tube angles and are competitive weight wise. Try Trek.

    Kona has always gone for slightly slacker head tube angles.

    I am totally with you by the way. If I could spec my own frame it would have 4 inches of rear travel and a 69 degree head tube. In my area there are a lot more rock gardens and drops than tight turns so I'd gladly trade some steering quickness for stability. I'm too old for the OTB trick.

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