Proper "fit" for BMX style bike

[zerpy]

This isn't a mountain biking question, but I know there are some BMX style riders out there that might be able to answer this one. I'm getting my 9 year old son a decent BMX style bike for his birthday this month. It is his first bike that isn't a garage sale special. He finally shed the training wheels this summer and part of the motivation I gave him for that was I'd buy him a bike that doesn't suck.

I guess I know how to properly adjust my mountain bike to fit me, but how about adjustments for a BMX style bike for someone? I'm not sure how high to put the seat for him, angle of the handlebars, angle of the seat, etc...

Thanks,
jas

[manual63]

This depends on whether he will race or not. If he does not race, you don't have to be as critical in the size of the bike. Make sure the bars are back far enough so his elbows are slightly bend while sitting on the seat. Make sure the seat is low enough, so that when he is standing and pedaling (which you do a lot of on a BMX bike) the seat is about knee height. If he does want to learn to bunny hop and jump, it is critical that the seat is not to high for obvious reasons.

If he plans on racing, there are many types and sizes of BMX bikes. There are Minis, Juniors, Experts, Pro, Pro XL. and Pro XXL sizes. He would probably run an Expert size, but it would only last him about 2 years or so before he would need a Pro size.

I don't know if you have a BMX bike yet, but there are 3 main types Racing, Jumping, and Freestyle. A racing bike will be the lightest, but it's not good for doing tricks or adding pegs. A jumping or freestyle bike is going to be heavier, but also a lot stronger. On a BMX bike, you don't size a bike by height like you do a Mountain or Road bike, you size it by top tube length. Basically, if you are under 5' 6" tall, you will want a 20" or shorter top tube length from center of seat tube to center of headtube. Of he is taller, a 20" - 21" top tube length is good. Over 21" Top tube is for really tall riders like 6' or more.

If you want suggestions of brands to get or have more questions about a type of bike, feel free to E-mail me at: manual63@yahoo.com

Just so you know my background a bit. I ran Twin City BMX for 7 years and have been riding BMX since 1980.

[zerpy]

Thanks for the info Shad. I haven't had anything to do with a BMX style bike since I was about his age (turning 10 here in a couple of weeks) and now after what you said, I don't think I ever had one adjusted right. When I was a kid, it was popular to have the handlebars really far forward so you were stretched out over the bike to reach them - got really sore after a while. Kinda funny thinking back on the stupid things we do when we are kids :)

Anyway, yes did just buy him a bike will give it to him at his b-day. Got him an 02 specialized vegas dirtboy. First of all, really good deal. For the size of the bike (expert) I went by the advise of the sales guy (my son wasn't around since this is a surprise) based on what I told him and what you just said confirms what he said. I wanted to get a more durable frame because I'm sure that as soon as he gets the coordination, he'll be jumping it off things - boys will be boys. Like you said, I'll have to get a bigger bike in a couple of years anyway, so if he gets interested in racing then we can address that issue. For now that isn't an issue, the coordination isn't there yet.

But I didn't know how to adjust it for him, so thanks for the info. One more question though. For the seat height, should that be at knee level with the pedals level or another position?

Again, thanks for the info...

jas

[manual63]

A rider should jump with one foot forward and one back when the pedals/cranks are level (parallel) to the ground. I like to jump with my right foot forward, which seems to be most common, but either way works. The seat should be about knee height and as he gains more experience, he will learn to use his knees on the seat to balance the bike during turns and jumps. One example is to pinch the seat with your knees during a barspin to keep the bike level under the rider while the hands are off the bars (much more advanced).

Mainly the seat should be low enough not to do damage to the vital area of manhood if he slips a pedal or something while jumping. Also, when and if he starts jumping, get him some shin pads and maybe even knee pads, as these parts get thrashed by the pedals a lot. Oh, and instead of tipping the seat forward, like on a mountain bike, tip it back a couple of notches. It helps when the seat is lower and is more natural.

[zerpy]

Sweet, that's good info - thanks much!

Heheheh, I have a very hard time picturing it, but I know it will happen.

Keeping the pedals level is a habit I have not yet learned. I somehow picked up the bad habbit when I was much younger to put one pedal down and I put a lot of my weight on it when I am not pedaling. Yesterday was my first time on the main track at lebanon and I didn't have the pedals level when going over a log crossing. I had already had a couple of "good" log crossings and was getting cocky, aka going at a pretty good clip, and was launched pretty good as my crank smacked into the log pile:) Hopefully I won't be teaching Zac that habit!:)

Thanks again for all the good info!
jas

[manual63]

Yeah, I guess it comes naturally for me, so I forget to mention it when writing some of my Tips. I guess I assume most people know to keep their pedals level when doing things like jumping, log rolls, or any other technical thing.

Maybe some have one pedal down and one up, which will get you in trouble a lot. The only time I have one pedal down and one up is in a turn. I make sure the inside pedal is up and the outside down. That way, you will not dig your inside pedal into the ground and if you need to take off your inside foot to keep from falling, it's already set to remove without the cranks having to rotate on you in a turn.

I hope your son enjoys BMX. It's what's kept me sane all these years.