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  1. #1
    Senior Member aaronmcd's Avatar
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    What is BMX vs mountain vs trials vs etc...?

    Hey, I ride a road bike. It's really simple because they are all the same - they are all geared, high saddle, drop bars, 700c wheels (or very close).

    I would like a fun bike that I could hop, do wheelies, and play around, but all the different options are really confusing to me. I would also like to ride backwards, but it seems you can't do this on BMX, mountain or trials. Are there fixed gear bikes sized more like a BMX?

    1) 20" vs 24" vs 26" wheels - what is the benefit of smaller wheels? It seems to me that small wheels would be really slow. Why do trials bikes have big wheels while BMX have small?
    2) Seat height. Is it just that a low seat means you can jump and drop more without being smacked with the seat? Again, it seems like a low seat would be a real pain to ride more than a mile/a few minutes.
    3) Free/fixed. It seems like people pick on fixed gear trick riding. But how about riding backwards? Also I'd think wheelies are easier on fixed gear.
    4) Gear ratio. Again, I would like being able to travel somewhat conveniently on any bike I own. 20" wheels with 2.75 gear ratio is going to be really slow, even while spinning super fast. is this why some people like the 24" wheels? What is the downside to 24" (see question 1)?

    Hope someone can help. Searching all over online and most hits I get assume the reader already knows what the difference between bmx/trials/fixed gear/mountain/etc are.

  2. #2
    ÖöÖöÖöÖöÖö Dannihilator's Avatar
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    I can't wheelie on my fixed gear to save my life, but can wheelie and manual with ease on the dmr.
    Strike like an eagle and sacrifice the dove.
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  3. #3
    Member Evil D's Avatar
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    Well, I grew up riding almost nothing but BMX, so here's my input.

    1. Smaller wheels mean lower gyroscopic force, which is the force applied to spinning wheels. This is what helps you stay upright when riding a bike. The bigger the wheel, the more gyroscopic force is applied to it. The reason this benefits a BMX bike is maneuverability. BMX often means jumps/tricks/etc and being extremely agile, much more so than you'll get on anything larger than a 20 inch rim. That's not to say you can't do tricks on anything bigger than a 20 inch rim bike, but you will have much more and much easier maneuverability on 20s. Overall speed just really depends on the gear ratio. Look into actual BMX racing. They may not be going as fast as a road bike, but then road bikes are also not jumping huge sets of doubles and going through rhythm sections and over burms. You also gain an advantage in acceleration with smaller wheels, which is beneficial in BMX racing since they're using doing short lapped races, not the distance stuff that road bikes see. Lastly, one of the biggest advantages to 20 inch rims is a shorter back end, which means less force required to pull the front end up and into a jump or hop. You can shorten the chain stays on a 24-26 inch bike until the rim hits the seat tube, and the back end will always be longer than a 20 inch frame because the wheel itself is bigger.

    2. Seat height has changed over the years. Back in the BMX gold years, guys raced with their seats up at a normal height just fine. Same with freestyle. As the tricks progressed and got more and more insane and technical, seat height dropped as a result. The tricks guys are doing on 20 inch bikes these days were unheard of even in video games just 10 years ago. The sport has progressed VERY fast in the last 10 years, and it wasn't exactly stone age back then. Basically, BMX bikes aren't built for riding long distances, so seat height is less important than seat clearance. That said, I have ridden 40+ mile round trips on my 20 inch bikes as recently as 2 years ago. Just raise the seat up and get a comfy seat. The leg extension will never be as efficient as a road bike when sitting down though, unless you have a 2 foot long seat post (then you run the risk of damaging the frame). When we were teens, riding was the only way we got around, so 20-30 miles on summer days were a common thing.

    3. I'm not sure what you mean by "fixed gear" vs. free? Do you mean fixed gear, as in one single gear (like a fixie) or do you mean literally fixed like a unicycle so that you could pedal backwards and be propelled backwards? I don't think I've ever seen a BMX bike that could be pedaled backwards like that. They do make freewheel hubs that allow you to ROLL backwards without having to counter-pedal, which are useful when rolling out backwards from tricks. I'm not even aware of trials bikes that have a solid fixed gear like a unicycle. You need to be able to spin the pedals backwards and reposition your feet.

    4. As far as gear ratios go, again we're not talking about riding distances. Even when we were kids riding 30 miles a day, we were goofing off, jumping ditches, having wheelie contests, etc. We weren't riding to make it anywhere in a set amount of time. That said, you aren't very limited to gear ratios until you get into some of the modern BMX frames that simply don't have room up front for a larger chain ring. Prior to about 2005ish or so, you had a typical 44ish tooth chain ring up front and usually about 16 or so in the back. This was the standard for decades unless you rode flatland, and then you ran a smaller 30ish tooth up front so you could easily snap the front wheel off the ground into a manual with a single pedal stroke. Now your typical BMX bike is running something like 28/9 gearing, which isn't as efficient as the older setup, but is much lighter and allows for better bottom bracket clearance. Again, BMX is evolving along with the tricks people do on them. BMX racing still uses the 44/16 or so gearing. Speed with smaller rims isn't impossible, I've been clocked at 35mph on my old racing BMX bikes. That may not be impressive to a road bike guy who can cruise along at 30 with ease, but how fast do you really plan on going on a bike that you're mostly interested in for bunny hops and manuals? Suffice to say that sustained long distance 15-20 is not unrealistic if you're in good shape.

    The down side to 24 is basically like I listed in #1 , you have a greater gyroscopic force on the wheels, and so you'll be less agile. If you're not doing spin type tricks and such, this may not matter to you. You'll have to really think about your riding style to decide. I have a 24 inch BMX bike, and it's my primary BMX bike. I don't ride near as hard as I used to, but it hops quite well considering the back end is much longer due to larger diameter wheels. Now, depending on how you look at it, this may or may not be a disadvantage. There are 24 and 26 inch BMX racing classes, and the 24 inch BMX/freestyle segment is booming big time right now, especially dirt jumping. Recently, there's even a 22 inch option that puts you in between the more common 20 and 24 options, so you get the best of both worlds.

    Here's a pic of my 24. It's a 2010 Fit CR24. It's crazy strong and weighs less than 95% of the 20s I grew up riding. As you can see, I run the seat rather high so I can get decent leg extension when sitting down. It's still not as comfortable as a road bike, but again why are you wanting to ride a BMX bike?



    The most recent ride I made on this bike was 85 miles on the Loveland Ohio bike trail, going from Loveland Ohio to Xenia Ohio and back (about 42.5 miles each way). I'd say we averaged about 10mph or so...not very fast, but we weren't out to set any speed records.

    I do sometimes run a shorter/lower seat post...just depends on what I plan on doing on it.
    Last edited by Evil D; 11-25-13 at 02:28 PM.

  4. #4
    Senior Member aaronmcd's Avatar
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    Quote Originally Posted by Evil D View Post
    Well, I grew up riding almost nothing but BMX, so here's my input.

    1. Smaller wheels mean lower gyroscopic force, which is the force applied to spinning wheels. This is what helps you stay upright when riding a bike. The bigger the wheel, the more gyroscopic force is applied to it. The reason this benefits a BMX bike is maneuverability. BMX often means jumps/tricks/etc and being extremely agile, much more so than you'll get on anything larger than a 20 inch rim. That's not to say you can't do tricks on anything bigger than a 20 inch rim bike, but you will have much more and much easier maneuverability on 20s. Overall speed just really depends on the gear ratio. Look into actual BMX racing. They may not be going as fast as a road bike, but then road bikes are also not jumping huge sets of doubles and going through rhythm sections and over burms. You also gain an advantage in acceleration with smaller wheels, which is beneficial in BMX racing since they're using doing short lapped races, not the distance stuff that road bikes see. Lastly, one of the biggest advantages to 20 inch rims is a shorter back end, which means less force required to pull the front end up and into a jump or hop. You can shorten the chain stays on a 24-26 inch bike until the rim hits the seat tube, and the back end will always be longer than a 20 inch frame because the wheel itself is bigger.

    2. Seat height has changed over the years. Back in the BMX gold years, guys raced with their seats up at a normal height just fine. Same with freestyle. As the tricks progressed and got more and more insane and technical, seat height dropped as a result. The tricks guys are doing on 20 inch bikes these days were unheard of even in video games just 10 years ago. The sport has progressed VERY fast in the last 10 years, and it wasn't exactly stone age back then. Basically, BMX bikes aren't built for riding long distances, so seat height is less important than seat clearance. That said, I have ridden 40+ mile round trips on my 20 inch bikes as recently as 2 years ago. Just raise the seat up and get a comfy seat. The leg extension will never be as efficient as a road bike when sitting down though, unless you have a 2 foot long seat post (then you run the risk of damaging the frame). When we were teens, riding was the only way we got around, so 20-30 miles on summer days were a common thing.

    3. I'm not sure what you mean by "fixed gear" vs. free? Do you mean fixed gear, as in one single gear (like a fixie) or do you mean literally fixed like a unicycle so that you could pedal backwards and be propelled backwards? I don't think I've ever seen a BMX bike that could be pedaled backwards like that. They do make freewheel hubs that allow you to ROLL backwards without having to counter-pedal, which are useful when rolling out backwards from tricks. I'm not even aware of trials bikes that have a solid fixed gear like a unicycle. You need to be able to spin the pedals backwards and reposition your feet.

    4. As far as gear ratios go, again we're not talking about riding distances. Even when we were kids riding 30 miles a day, we were goofing off, jumping ditches, having wheelie contests, etc. We weren't riding to make it anywhere in a set amount of time. That said, you aren't very limited to gear ratios until you get into some of the modern BMX frames that simply don't have room up front for a larger chain ring. Prior to about 2005ish or so, you had a typical 44ish tooth chain ring up front and usually about 16 or so in the back. This was the standard for decades unless you rode flatland, and then you ran a smaller 30ish tooth up front so you could easily snap the front wheel off the ground into a manual with a single pedal stroke. Now your typical BMX bike is running something like 28/9 gearing, which isn't as efficient as the older setup, but is much lighter and allows for better bottom bracket clearance. Again, BMX is evolving along with the tricks people do on them. BMX racing still uses the 44/16 or so gearing. Speed with smaller rims isn't impossible, I've been clocked at 35mph on my old racing BMX bikes. That may not be impressive to a road bike guy who can cruise along at 30 with ease, but how fast do you really plan on going on a bike that you're mostly interested in for bunny hops and manuals? Suffice to say that sustained long distance 15-20 is not unrealistic if you're in good shape.

    The down side to 24 is basically like I listed in #1 , you have a greater gyroscopic force on the wheels, and so you'll be less agile. If you're not doing spin type tricks and such, this may not matter to you. You'll have to really think about your riding style to decide. I have a 24 inch BMX bike, and it's my primary BMX bike. I don't ride near as hard as I used to, but it hops quite well considering the back end is much longer due to larger diameter wheels. Now, depending on how you look at it, this may or may not be a disadvantage. There are 24 and 26 inch BMX racing classes, and the 24 inch BMX/freestyle segment is booming big time right now, especially dirt jumping. Recently, there's even a 22 inch option that puts you in between the more common 20 and 24 options, so you get the best of both worlds.

    Here's a pic of my 24. It's a 2010 Fit CR24. It's crazy strong and weighs less than 95% of the 20s I grew up riding. As you can see, I run the seat rather high so I can get decent leg extension when sitting down. It's still not as comfortable as a road bike, but again why are you wanting to ride a BMX bike?



    The most recent ride I made on this bike was 85 miles on the Loveland Ohio bike trail, going from Loveland Ohio to Xenia Ohio and back (about 42.5 miles each way). I'd say we averaged about 10mph or so...not very fast, but we weren't out to set any speed records.

    I do sometimes run a shorter/lower seat post...just depends on what I plan on doing on it.
    Thanks for the detailed reply!
    You mentioned those pedal backwards to brake bikes. Are there bikes without free hubs?
    You also have only a rear brake on that bike. Is that standard?
    Last, I remember my brother had one as a kid, and it had some special thing at the steer tube that somehow broke up the brake cable to allow bar spins. Do you know what this is?

  5. #5
    Member Evil D's Avatar
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    Quote Originally Posted by aaronmcd View Post
    Thanks for the detailed reply!
    You mentioned those pedal backwards to brake bikes. Are there bikes without free hubs?
    You also have only a rear brake on that bike. Is that standard?
    Last, I remember my brother had one as a kid, and it had some special thing at the steer tube that somehow broke up the brake cable to allow bar spins. Do you know what this is?

    If you mean are there bikes with pedal brakes, there are but they're usually lower end kids bikes. There used to be hubs like that used for flatland riding though.

    The rear only brake is standard on a lot of BMX bikes, if they have any brakes at all. Many bmx guys ride brakeless these days. You can still add front brakes if you want to though. Usually it's just to save weight. The steering tube thing you're referring to is commonly called a Gyro because that was the name of one of the original designs made by Odyssey. They basically add a bearing system in the middle of the cable to allow it to spin without tangling up. They aren't absolutely necessary for bar spins, you just have to run a long enough cable to allow it to wrap around the head tube, but then you can only do so many bar spins before you need to spin back the other way.

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