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  1. #1
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    The evolution of MTB XC geometry?

    I've ridden off and on for years and recently got back on the saddle. Catching back up with the latest trends has been fun, but in regards to hard tails, what has changed about mountain bike geometry in the last 10+ years?

    Looking at the latest offerings from the big brands it seems like head tubes are still at 71, seat tubes at 73 and chain stays are still around 17-inches. If things have changed, what? I have to be missing something.

    I ask because I was at a bike shop the other day and the tech mentioned that modern mountain bikes are a lot different than they were 10 years ago. This didn't seem right to me, but I didn't want to argue with the guy, out of fearing of exposing my ignorance -- I was asking him for advice after all.

    Obviously, 29ers, disc brakes, and long travel forks have come a long way in the last decade, but in regards to geometry on a XC mountain bike, what's different?

  2. #2
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    XC hardtail geometry really hasn't changed much in the past decade except the frames are now designed around 100mm or 120mm forks. Top tubes (ETT) may be a smidge longer.

    The biggest changes are in the components. Suspension forks are much better now and disc brakes are the norm.

    There have been geometry changes for long-travel "all-mountain" hardtails though. primarily slacker geometry.
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  3. #3
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    Quote Originally Posted by Bjdraw View Post
    I've ridden off and on for years and recently got back on the saddle. Catching back up with the latest trends has been fun, but in regards to hard tails, what has changed about mountain bike geometry in the last 10+ years?

    Looking at the latest offerings from the big brands it seems like head tubes are still at 71, seat tubes at 73 and chain stays are still around 17-inches. If things have changed, what? I have to be missing something.

    I ask because I was at a bike shop the other day and the tech mentioned that modern mountain bikes are a lot different than they were 10 years ago. This didn't seem right to me, but I didn't want to argue with the guy, out of fearing of exposing my ignorance -- I was asking him for advice after all.

    Obviously, 29ers, disc brakes, and long travel forks have come a long way in the last decade, but in regards to geometry on a XC mountain bike, what's different?
    Not sure which bikes you are looking at, but in general, but over the past 15 years your average xc/trail bike has gotten slacker in the head tube, longer in the top tube (and typically run with shorter stems).

    It may be that you are looking at bikes more aimed at xc racing, not sure, people have different definitions of what counts as an "XC" bike. It seems to me that back in 2000, you had mostly either xc bikes with the geo you are talking about, or FR bikes. It is the vast ground between them that has been filled in since then. So while there are bikes out there now with the same numbers, there are also more other options.
    15mm is a second-best solution to a problem that was already solved.

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    That is what I suspected. The handle bars are higher as a result of the 100+ forks, but other than the obvious suspension benefit for rough terrain, does the higher handle bar make the bike more comfortable, less likely to endo and/or faster?

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    Quote Originally Posted by kapusta View Post
    Not sure which bikes you are looking at, but in general, but over the past 15 years your average xc/trail bike has gotten slacker in the head tube, longer in the top tube (and typically run with shorter stems).
    The bike he referenced specifically was a Specialized Rockropper 29er. Its head tube is at 70 and seat tube at 73 with 100mm of travel.

    My bike, which he said was much different is a '96 Univega Aluminum 808. I measured the head tube at 71 and the seat tube at 73, with 60mm of travel. The discussion was spurred when I was asking about replacing the front fork with a RS XC30 with 80mm of travel, which I estimate will change the head tube angle to ~70 degrees.

    I know that the new bike has much better components, more travel, etc. The only thing I'm trying to understand is how the geo is different/better.
    Last edited by Bjdraw; 06-24-2012 at 11:29 AM.

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    Quote Originally Posted by Bjdraw View Post
    That is what I suspected. The handle bars are higher as a result of the 100+ forks, but other than the obvious suspension benefit for rough terrain, does the higher handle bar make the bike more comfortable, less likely to endo and/or faster?
    Longer travel, shorter stems, wider riser bars provide more control. Faster on the downhills, but not on the flats or uphills (though full susp is actually better on some uphills). I'm still a bit old-school (started in the early 90s) so I still like longer stems and narrower bars than the typical newer rider, but my stems today are about 20 mm shorter than they were 10 years ago and I'm running riser bars that are 1 to 2 inches wider than the flat bars I used to run. New fatter tires are awesome. There are plenty of lightweight 2.3-2.35 XC tires available today.
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    Quote Originally Posted by trailville View Post
    Longer travel, shorter stems, wider riser bars provide more control. Faster on the downhills, but not on the flats or uphills (though full susp is actually better on some uphills). I'm still a bit old-school (started in the early 90s) so I still like longer stems and narrower bars than the typical newer rider, but my stems today are about 20 mm shorter than they were 10 years ago and I'm running riser bars that are 1 to 2 inches wider than the flat bars I used to run. New fatter tires are awesome. There are plenty of lightweight 2.3-2.35 XC tires available today.
    Good point. Stems, riser bars, wider tires, all great advancements in recent years, but all easily swapped out. It seems the biggest reason my frame is outdated is because it can't handle a 100mm fork or disc brakes.

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    Quote Originally Posted by Bjdraw View Post
    Good point. Stems, riser bars, wider tires, all great advancements in recent years, but all easily swapped out. It seems the biggest reason my frame is outdated is because it can't handle a 100mm fork or disc brakes.
    100mm fork may be the issue with intended geometry. Strength not as much I'm sure it could handle a bit more than 80mm. I'm building my old Ibis Szabo as SS it was designed with 80mm in the front and 125mm in the back, it was too steep and quick for my liking. I'm putting a 120 fork in the front, the handling is quite similar to the modern geometry.

    Disc brake, there are a few adapter you can find to fit your bike and make it disc compatible.

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    It isn't the geometries that have made the differences over past years as much as how the frame material twists and flexes.

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    Quote Originally Posted by Bjdraw View Post
    The discussion was spurred when I was asking about replacing the front fork with a RS XC30 with 80mm of travel, which I estimate will change the head tube angle to ~70 degrees.
    Putting a new 80mm fork on your bike shouldn't be a problem. But I'd suggest looking for a better fork than the XC30. You've currently got a nice lightweight 90s hardtail, putting a 5-pound lower end modern fork on it may not be the best plan. Unfortunately, I don't think any of the higher end 80mm forks come with brake bosses any more, so if you go to something like a Reba, you're going to have to put a disc up front and get a new front wheel. If you run a mechanical disc (like a BB7) you can use your same current v-brake lever. Running a mechanical disc up front with a v-brake in the back works fine.
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    Yes, the selection of 80mm shocks is the one part of the geometry of my bike that I do not like. In fact the XC30 was the highest end model I could find available in 80mm and with mounts for rim brakes -- didn't consider mixing brakes, but that's a good idea. I essentially settled on it because I'm sure it is far superior to my old school Rockshox -- especially since it is locked up. The weight of the XC30 is about 2lbs heavier than the one I have now, but at $150 it much more affordable than a new bike -- not to mention the bike Rockhopper comes with just as heavy of a shock. I figure I'll get a new bike in the next year or so and keep this one as a spare or use it to ride around town. After I understand all the advancements since the last time I bought a bike.
    Last edited by Bjdraw; 06-24-2012 at 11:36 AM.

  12. #12
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    How about a Manitou Minute Expert - 4.1 lbs with Alu. steerer, 80mm with v-brake mounts.

    Manitou Minute Expert 26" Suspension Forks 100076029 at CambriaBike.com

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    Quote Originally Posted by drag_slick View Post
    How about a Manitou Minute Expert - 4.1 lbs with Alu. steerer, 80mm with v-brake mounts.
    Not sure how I missed that one. It is a little more than I wanted to spend and not much lighter at 1905g than the XC30 at 1917g (my old Rockshox is only ~1400g). Based on the specs, though, it does look worth the extra $120.

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    Quote Originally Posted by Bjdraw View Post
    Not sure how I missed that one. It is a little more than I wanted to spend and not much lighter at 1905g than the XC30 at 1917g (my old Rockshox is only ~1400g). Based on the specs, though, it does look worth the extra $120.
    The Manitou has a much better damper. I also see the XC30 listed at 2180g versus 1861g for the Minute with aluminium steerer. It should also be stiffer since it has 32mm stanchions versus 30mm.

    Much better fork honestly.
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    That is part of what makes all of this so frustrating. One site lists the weight at 2180, while another one lists it at 1917g. I can only assume that one is the 80mm and the other is 100mm.

    Even worse, the axle to crown measurements are impossible to obtain. In the interest in retaining as close to original of a head tube angle as possible, I'd really like to know if the a2c of two 80mm forks is the same. I was able to find a site online that indicated my old RS fork a2c is 408mm -- I can't measure mine because it is seized.

    I already ordered the xc30tk and my plan is to keep riding my old frame until I choose a new bike. If I decide to stick with a 26-inch hardtail, then I'll evaluate my need for 100mm of travel and disc brakes, and if I still bike old frame geometry with an 80mm fork on it. I may also try to find a good deal on a shorter stem (currently running 130mm) and longer riser bar so that I can test out my old frame in the more modern seating position.

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    The 63mm Judy's had an A2C around 420mm.
    Newer 80mm forks range from 450mm to 460mm depending on brand and model.
    The difference isn't as great once you take sag into account.
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    I have a Quadra 21r on mine, but the Aluminum 808 was also available with a Judy.

    Here is where I got the 408 mm from.
    BikePro.com / Buyer's Guide / Suspension Fork Comparison Table - Bicycle Parts at discount prices / the Buyer's Guide / Bicycle Parts at their finest! / Professional Bicycle Source / Bike Pro

    I was hoping for a little sag, I was thinking that I may be able to adjust the preload a bit as well. I only weight 160lbs so I'm hopeful that the xc30tk can get me by while I figure out what to do next.

  18. #18
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    Your Quadra may have been 408mm, but the Judys were a little longer (I still have a 1996 Judy XC). As frames were gradually adjusted for suspension, the A2C of newer fork models became longer even with the same travel.
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  19. #19
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    Bikes have changed with improvements in technology. Components are the obvious target but frame materials going from tubes to all sorts of extruded and "laid-up" shapes have made frames respond differently by putting strength and flexibility where it is needed and still reduce wieght.

    One of the big reasons for bikes changing is that the rider who that enters the sport, and stays with it, is different. The old designs required a certain amount of hardnosed stick-to-it-ness due to the skill demands. Modern bikes forgive a lot and a more general type of athlete will stay with the sport. The modern bike is more comfortable and doesn't demand as much from the rider. That said, good riders, who can ride anything, now do phenominal things on modern bikes.

    Old school good riders don't ask if a design will keep one from going OTB; you did that by knowing how to ride what was under you. If you didn't you quit and took up road or golf. You didn't put your bars up high, you learned how to get your weight behind them and drive the wheel past an obstical or learned to pick a good line. With a rigid fork, thinner tires, or a limited travel fork it was your only option. Now with the wonderful shocks, wide and durable tubeless tires you can just wham into and over things with little regard for a line.

    I don't mean to say "well scout, back in the day we knew how to ride and didn't have all these new-fangled gizmos that did everything for us." I do mean to say that the modern rider, who is growing our sport by the way, is different. Manufacturers have come to understand what works a lot better for more riders and keeps them riding and newer technologies make that chicken-and-egg paradigm more intimate and comprehensive.

    In my lifetime some of our folks felt that in order to learn to drive you had to learn on a stick. That's how I learned and in SF no less. In High school we all eschewed the automatic, a slushbox, and raced around with dual carbs with 4-speeds with no syncros and disc brakes if you had an import, maybe on all 4 wheels. What am I driving now? 5 speed automatic? No, computerized fuel injected flat 4 and a CVT with infinite ratios and computerized 4-wheel disc anti-lock brakes that work better than I ever could.

    That said, I am not so sure that one need to ride an HT to learn to ride well. That said, that said, it is really cool when you are out in the hills and people look at you and say, "you're doing that on a hardtail?" My lower bars on my dual-suspended bike draw some looks but I can't seem to give that up.
    Attached Thumbnails Attached Thumbnails The evolution of MTB XC geometry?-ebonti852.jpg  

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    My new fork arrived today and I just finished my first test ride after installing it (just around the neighborhood) and am happy with how it turned out. I have no doubt it'll hold me over while I look for my next bike and serve as a good backup. Thanks for al the insight, it'll definitely come in handy as now I'll know what to look for. The evolution of MTB XC geometry?-img_0539_md.jpg

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    Quote Originally Posted by Berkeley Mike View Post
    Bikes have changed with improvements in technology. Components are the obvious target but frame materials going from tubes to all sorts of extruded and "laid-up" shapes have made frames respond differently by putting strength and flexibility where it is needed and still reduce wieght.

    One of the big reasons for bikes changing is that the rider who that enters the sport, and stays with it, is different. The old designs required a certain amount of hardnosed stick-to-it-ness due to the skill demands. Modern bikes forgive a lot and a more general type of athlete will stay with the sport. The modern bike is more comfortable and doesn't demand as much from the rider. That said, good riders, who can ride anything, now do phenominal things on modern bikes.

    Old school good riders don't ask if a design will keep one from going OTB; you did that by knowing how to ride what was under you. If you didn't you quit and took up road or golf. You didn't put your bars up high, you learned how to get your weight behind them and drive the wheel past an obstical or learned to pick a good line. With a rigid fork, thinner tires, or a limited travel fork it was your only option. Now with the wonderful shocks, wide and durable tubeless tires you can just wham into and over things with little regard for a line.

    I don't mean to say "well scout, back in the day we knew how to ride and didn't have all these new-fangled gizmos that did everything for us." I do mean to say that the modern rider, who is growing our sport by the way, is different. Manufacturers have come to understand what works a lot better for more riders and keeps them riding and newer technologies make that chicken-and-egg paradigm more intimate and comprehensive.

    In my lifetime some of our folks felt that in order to learn to drive you had to learn on a stick. That's how I learned and in SF no less. In High school we all eschewed the automatic, a slushbox, and raced around with dual carbs with 4-speeds with no syncros and disc brakes if you had an import, maybe on all 4 wheels. What am I driving now? 5 speed automatic? No, computerized fuel injected flat 4 and a CVT with infinite ratios and computerized 4-wheel disc anti-lock brakes that work better than I ever could.

    That said, I am not so sure that one need to ride an HT to learn to ride well. That said, that said, it is really cool when you are out in the hills and people look at you and say, "you're doing that on a hardtail?" My lower bars on my dual-suspended bike draw some looks but I can't seem to give that up.
    Some of the advancements are certainly in technology that was simply not an option in the old days (brakes, tires, suspension), but some have been changes in frame geo and cockpit setup.

    I'm not sure if I could consider my self "old school", but I started riding in 1998 with a bike from the early 90's. Me (and everyone I rode with) learned on "old school" bikes. Long stems, low, narrow bars, bar ends, and shorter top tubes.

    To be honest, I think we all rode that kind of geometry and setup because nobody knew any better.

    Not saying that the old-school geo does not work for some folks, but I think we now have a much better understanding of the advantages of different ways to approach frame geometry and cockpit setup.

    Forward 14 years, almost everyone I rode with then that has stayed active in the sport has migrated away from the old school setups to some extent (some more than others).
    15mm is a second-best solution to a problem that was already solved.

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    Mike.. I am an old school guy as well. Part of this due to my path I have taken in this.

    I started in 98 on a hardtail. My friends also rode hardtails and we had blast on in fact had a rigid because we could never find fork to fit is giant giaint (he his 6' 4"). We rode everywhere could on these hardtails and loved it. By the 2003 we had some nice bikes. My friend ended up on a GT Ti Ligthning with 63mm Carbon Sid race fork on it. I ended with KHS Alite 4000 with full XT components and an ok 100mm Judy SL.

    Then two of us go married in 2004 and that realy cut the riding back. Fast forward to 2011 and we both got back in to riding. Dusted off the old bike and picked up where we left off. Now everyone (including our 6'4" friend) is on either a 29er or FS bike. The two of us still ride our V-brake 3x9 26" hardtails still have as much fun as before. I guess you can call us old school.
    Attached Thumbnails Attached Thumbnails The evolution of MTB XC geometry?-khs01-s.jpg  

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    JoePAz,

    Your story is so much like mine, wow. Starting riding while I was at school in Tallahassee in '98, rode non-stop until about 2002. Had kids, other hobbies and now I'm trying to get back onto my bike and love it. The sad part of my story is that the elastomers in my shock were completely gone, so riding it was like riding a rigid. I rode it for a few months and decided to upgrade the shock. Had two different techs at two different shops tell me to just buy a new bike, cause my wasn't worth fixing -- although I suspect it is because they think Univega is a cheap wal-mart brand, guess they aren't old enough to remember.

    Anyways, didn't mean to turn this into an old bike glory days post, but glad to know that while geometry does change over the years, old bikes don't die.

  24. #24
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    Quote Originally Posted by Bjdraw View Post
    JoePAz,

    Your story is so much like mine, wow. Starting riding while I was at school in Tallahassee in '98, rode non-stop until about 2002. Had kids, other hobbies and now I'm trying to get back onto my bike and love it. The sad part of my story is that the elastomers in my shock were completely gone, so riding it was like riding a rigid. I rode it for a few months and decided to upgrade the shock. Had two different techs at two different shops tell me to just buy a new bike, cause my wasn't worth fixing -- although I suspect it is because they think Univega is a cheap wal-mart brand, guess they aren't old enough to remember.

    Anyways, didn't mean to turn this into an old bike glory days post, but glad to know that while geometry does change over the years, old bikes don't die.
    Wow... your story is almost identical to mine.
    I stopped riding 2004 due to wife and then kids. When I started back in 2011 I considered getting rebuild kit for my Judy since she is s old. Judy is 2002 vintage and I had seen some damp spots around it. So I figured I would rebuild it myself. I was in my LBS and they told me no they don't have any kits and that I would need new fork and probably a new bike. I said mine was only 23lbs and did not really want to change it. They said they don't come that light any more with disc brakes and tubeless tires. Well I walked out figuring that I will just ride what I have. The judy is coil spring based with oil damper and low pressure air assist. It seems to be holding so I will just ride it.

    My KHS frame is pretty rare yet back in 2003 was pretty well respected. So I plan on keeping it as long as I possibly can. I am even staying with tube tires and v-brakes. I am concerned that if my wheels get buggered up that I will have a hard time finding good quality rim brake wheels. At least my frame and fork have the attachments for disc brakes if I am forced that way.


    As for changes... seems like the biggest changes are the riding style. Like Mike was eluding to back in our day there was XC and downhil. Not much in between. FS were evolving and many had lots of drawbacks still. Now FS has changed so much that what would pass for crazy downhill bikes 10 years ago are now typical trail bikes. Riders today think nothing of jumping off 3' drops. These bikes are also quite heavy in many cases. This progression into simply flying over nasty terrain while letting the bike soak up the bumps seem more prevelant.

    Still a good rider on an old school hardtail can still wipe up on mediocre rider on FS bike any day. After all going up a hill is still about the motor pushing the pedals and arms pulling on the bars.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

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    If my hands, feet, and butt are in the same position as it was in 1995, does geometry make a difference?

    Actually, my cockpit has gotten smaller as I have aged but the attack position has been the heart of things. Come to think of it I used to be just a mountain biker but, now with all the special purposed bikes while my riding hasn't changed much I am considered an XC guy. I think that means I get my butt out of the saddle more than most, as opposed to sittn' in my sled with my hands high.
    I don't rattle.

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