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Beetlenut

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I'm trying to buy a new Mtn bike for my son, and am not sure on the sizing. What is the relationship between frame size, which I believe everyone on here is talking about, and tire size, which I think most generic bikes are sized at? I can't decide between a 20" or a 24" bike. Took my son out riding last weekend around the trails surrounding the development I live in, and was amazed to discover all kinds or single track trails with jumps and berms etc... Guess the neighborhood kids have grown up and have been busy since the last time I was back there! My son was on his old small 16" bike and was killing himself taking some of those jumps. But he kept getting right back up saying, "I'm Ok, I'm OK". Then of course he made me take those same jumps. I felt bad for him, and knew he needed a bigger bike to handle that terrain. The good part is we have a new hobby in the making, and are only few miles from the Arcadia Management Area with miles of mapped-out single track!
 

Greg

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Most higher end bikes are sized by the frame, i.e. the length of the seat tube. All manufacturers measure differently though - some to the bottom of the bottom bracket, some to the top. Some bikes have a "virtual" size. When you talking about a 20" or 24" bike for a kid, that refers to the tire diameter, not the frame. Most standard adult MTBs have 26" or 29" diameter tires. Some have a 29" front and a 26" rear (69ers). Confused yet?

Go to the LBS and have your son fitted for a bike. That's the best approach.
 

Marc

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Most manufacturers for MTB's measure from the center of the BB shell, if I remember correctly. GT is one I remember clearly measuring from the bottom of the BB shell resulting in slightly larger nominal frame sizes. Bikes that claim a virtual size are ones that don't have a standard seat tube, usually because of suspension design.

It's also common to see downhill oriented bikes to use 24" rear wheels with a 26" front wheel but the overwhelming majority of adult mountain bikes still use 26" wheels.
 

Greg

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Most manufacturers for MTB's measure from the center of the BB shell, if I remember correctly.

Thanks for clarifying. I knew it had something to do with the BB. :oops:

Bikes that claim a virtual size are ones that don't have a standard seat tube, usually because of suspension design.

Yup - My Trek is like this. The actual length is 17.5". Virtual is 18.5".
 

Beetlenut

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Most higher end bikes are sized by the frame, i.e. the length of the seat tube. All manufacturers measure differently though - some to the bottom of the bottom bracket, some to the top. Some bikes have a "virtual" size. When you talking about a 20" or 24" bike for a kid, that refers to the tire diameter, not the frame. Most standard adult MTBs have 26" or 29" diameter tires. Some have a 29" front and a 26" rear (69ers). Confused yet?

Go to the LBS and have your son fitted for a bike. That's the best approach.

Not too confused, except the 26"/29"thing. Never heard of a LBS in Rhode Island.
 

Greg

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Thanks, I are schooled now! I indeed will have to check out my LBS for a FS bike for my son who had two OTB's while riding the other day!

Now you're getting it... :lol:
 

Paul

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Got a link to those Acadia maps, nut? I'd love to head down and try that, then over to J-town for lunch.
 

MR. evil

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For my son, I think Bennys will work just fine! Now for me....

I wouldn't waste your money on a low end FS bike (under $1000) unless you get a sweet online deal. Spend the same amount on a good quality HT (front suspension only) and you will get a much better bike that will last alot longer
 

Beetlenut

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Got a link to those Acadia maps, nut? I'd love to head down and try that, then over to J-town for lunch.

No I don't have a link yet, not sure if they're online, might have to buy a book. Some friends of mine have told me that the trails are nice, nothing too technical. My son is just starting to ride on the trails, so might be a good way to ease him into it. If I get a good (free) link to a site, I'll pass it on.
 

Beetlenut

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I wouldn't waste your money on a low end FS bike (under $1000) unless you get a sweet online deal. Spend the same amount on a good quality HT (front suspension only) and you will get a much better bike that will last alot longer

I hear ya on the low end stuff, but money's a problem and my son is only 10. If he really gets into it, I can upgrade. Besides I have a 5 year old that will soon also want to join in the fun! $$
 

MR. evil

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I hear ya on the low end stuff, but money's a problem and my son is only 10. If he really gets into it, I can upgrade. Besides I have a 5 year old that will soon also want to join in the fun! $$

Understood, no need to break the bank on a 10 year old. But as an example, a kids FS bike that cost $300 is going to be a complete POS. But a kids HT for the same amount will be a MUCH better bike. On the really low end FS bikes, the rear suspension doesn't really do anything except make riding the bike harder and less effiecient. The rear suspension on these bikes are ussually nothing more than a metal spring with out a damper that will bob like a pogo stick when you try to pedal or hit a bump. Parents buy them because they don't know any better and kids think they look cool. But they are complete garbage and should not even be called a full suspension bike. More like a full suspension like object. Sorry if I am coming off as harsh, but its the truth. One of my nephews has one of these things and I cannot even begin to explain how bad it is. Get you son a decent HT bike with front suspension only.
 

Beetlenut

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Understood, no need to break the bank on a 10 year old. But as an example, a kids FS bike that cost $300 is going to be a complete POS. But a kids HT for the same amount will be a MUCH better bike. On the really low end FS bikes, the rear suspension doesn't really do anything except make riding the bike harder and less effiecient. The rear suspension on these bikes are ussually nothing more than a metal spring with out a damper that will bob like a pogo stick when you try to pedal or hit a bump. Parents buy them because they don't know any better and kids think they look cool. But they are complete garbage and should not even be called a full suspension bike. More like a full suspension like object. Sorry if I am coming off as harsh, but its the truth. One of my nephews has one of these things and I cannot even begin to explain how bad it is. Get you son a decent HT bike with front suspension only.

What about the front fork suspensions on the low end HT's? Are they also nothing more than springs inside tubes, or is there some dampening in those? What are some decent brands of low ent HT's?
 
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