Bicycle Mechanics - 24" wheels on a 26" bike

Hi
I am looking for a new bike for my 12yo son. He's a little short for a 26", but will probably outgrow a 24" soon. He needs a bike now and I'm trying to avoid buying two bikes in one year. I'm reluctant to get him a bike thats too big for him, but I was wondering if I could buy the bigger bike and then reduce the height of the bar by installing smaller tires. He only needs a few inches.
Has anybody ever heard of this? The front wheel seems easy enough, but how complicated would the rear switch be? Can I put a 24" in the front and keep the rear 26"? What about the brakes?
Lots of questions, Please Help.
Thanks
Mike

The brakes will probably not reach and you won't get that much more bar drop out of it. There are some pretty small 26" bikes that might give him enough room. You could also look for a used 24" There have to be a bunch of them out there, try Craigslist.

Last winter I bought a 26" MTB-styled bike for my 9 year-old grandson who is tall for his age but not by much. I bought one with a "compact-style" frame, i.e., the top tube is dropped significanty below the horizontal so he has plenty of stand-over clearance and has no problems handling it. You should be able to find a similar style.

As RG said, a wheel change won't help much but will cause all sorts of brake reach and other problems.

I'm in the Backwoods of Louisiana.
No craigslist, no LBS, no ads for used bikes within 150 miles, etc.
Only Wal-Mart and the UPS man.
It's either "do it yourself" or "learn to live without it".
Thanks for the help.
Mike

Maybe not a practical alteration.... you could probably use a 24" rear wheel with a coaster brake if you can find one that will fit the rear spacing of your frame (or use hub or disc brakes) so rim-brake reach wouldn't be an issue. The smaller wheels will also alter the handling of the bike ('cause the frame geometry, fork rake & resulting trail were designed for 26" wheels), but I don't know how much.

If he's going to outgrow it within a year, then a cheap Wal-Mart bike may just work. Just make sure the stem, handlebars, shifters, brake levers, pedals, crankarms, seatpost, saddle, and wheels are tight before he rides it. Then you may need to adjust the brakes and deraillers.

I'll be putting on the Nomax underware in the back...............

How short is your son? I (average height) was riding 26" bikes at age 10, and my brother (below average) left his 24" bike for a 26" when he turned 11. You should be able to find a small bike on 26". Don't they make 12" frames for full size wheels now?

I'm in the Backwoods of Louisiana.
No craigslist, no LBS, no ads for used bikes within 150 miles, etc.
Only Wal-Mart and the UPS man.
It's either "do it yourself" or "learn to live without it".
Thanks for the help.
Mike
E-Bay?

How tall is your son and what is his inseam measurement?

I'm 5' 1" and have an inseam of 26 1/2" and I ride a 24" mountain bike and its the RIGHT size! He would need to be bigger than me before a 24" mountain bike is too small for him. Seriously.

There are FAR too many children out there these day's riding bikes that are way too big for them. It seems to be a trend and once one starts it other childrens parents for some reason get the idea that the larger size is better so its started a trend that feeds itself.

Changing wheels is going to do nothing to improve fit and the brakes won't work with smaller wheels anyway. There are 2 fit factors far more important than height that you cant easily fix. First the cranks on the 26" mountain bike will be way to long. They will be 170 mm(nearly 7") long which is stupidly long for children and it will teach bad habits at the least if not do harm. He shouldn't be using cranks longer than 150 mm(6"). Secondly the top tube length will be too long. The smaller wheels alows for shorter top tube length which is just as important as height. Often people slide the seat forward to compensate but again this isn't a good idea.

Anyway I reccomend getting the 24" wheeled bike as it will provide superior fit and will fit for far longer than you think.

Regards, Anthony

KNJC68 had a good solution but a new wheelset is just as pricey as an X-mart bike.
And you may need a shorter crank.

Enjoy

For what it's worth, I went the 24 inch for 2 years route when my son was 11. He was tall, but had coordination problems and I was concerned that a 26 inch bike would be difficult for him to handle. I picked up the least expensive Walmart bike I could find, a Roadmaster Mt. Fury. It lasted the two years I wanted out of it, then I replaced it with an old, 1988, Gary Fisher Hoo Koo E Koo. I sold the Mt Fury at a yard sale for about $25, half what I paid for it. So if you can repeat that process, it will cost you $25 for your son to ride a proper size bike for 2 years. Then he'll be taller, and you can buy him a LBS bike.
Given your situation, maybe Walmart is the best answer.

If he's going to outgrow it within a year, then a cheap Wal-Mart bike may just work. Just make sure the stem, handlebars, shifters, brake levers, pedals, crankarms, seatpost, saddle, and wheels are tight before he rides it. Then you may need to adjust the brakes and deraillers.

I'll be putting on the Nomax underware in the back...............
Good advice from DieselDan. The Mt Fury I referenced above had some loose bolts and I remember the deraileur had problems throwing the chain into the wheel when shifting into the granny gear (the plastic guard stopped any serious damage). I didn't know how to adjust a deraileur then, so he just rode it without use of that gear. The problems with Wal-mart bikes are not exagerated, you need to check it out completely before your son rides it.

How tall is your son and what is his inseam measurement?

I'm 5' 1" and have an inseam of 26 1/2" and I ride a 24" mountain bike and its the RIGHT size! He would need to be bigger than me before a 24" mountain bike is too small for him. Seriously.

There are FAR too many children out there these day's riding bikes that are way too big for them. It seems to be a trend and once one starts it other childrens parents for some reason get the idea that the larger size is better so its started a trend that feeds itself.

Changing wheels is going to do nothing to improve fit and the brakes won't work with smaller wheels anyway. There are 2 fit factors far more important than height that you cant easily fix. First the cranks on the 26" mountain bike will be way to long. They will be 170 mm(nearly 7") long which is stupidly long for children and it will teach bad habits at the least if not do harm. He shouldn't be using cranks longer than 150 mm(6"). Secondly the top tube length will be too long. The smaller wheels alows for shorter top tube length which is just as important as height. Often people slide the seat forward to compensate but again this isn't a good idea.

Anyway I reccomend getting the 24" wheeled bike as it will provide superior fit and will fit for far longer than you think.

Regards, Anthony

Anthony is exactly right. Here's the way it works: Buy a tiny-framed, bizarrely proportioned 26" bike, and a year or two later, the kid will have outgrown it and will need a bigger frame size. Buy a 24" wheel bike, and the kid will have fun riding safely and confidently on it until he's ready to skip over the small 26" bike and go for a normally proportioned 26" bike. Going the 26" route now won't save you any money.