700 and 650 wheels.

Teach

Sorry if this is posted in the wrong section.
I'm looking at building a bike for my 11 year old son. The bike building itself I am fairly happy with what I'm not sure is what I need. What I am not sure about are the wheels.

Basically what's the difference between 650 and 700 wheels.

I'll now add more ramblings.
I know the 700 wheel is bigger, but how much bigger? Will the wheel significantly affect how big the bike feels? Can you change between 650 and 700 wheels on any frame? If not how do you know whether a frame takes 650 or 700 wheels. Are there any significant benefits for children in having either size?

Cheers

John.T

Basically what's the difference between 650 and 700 wheels.

Basically 50mm in diameter. You would have trouble fitting the brakes if you used 650s in a normal frame. There would not be clearance for 700s in a frame made for 650s.
Also not so many tyres available for 650 wheels.

MichaelW

650C is sometimes interchangeable on an MTB sized frame. The 650C rim is about 6mm lower at the brake blocks (also the axle width standard is different for road and MTB)
You can get tyres down to 1"which is pretty much the same as a 28mm.

stickman

Teach,
can you clarify 650a which some old road bikes and roadsters have, or 650c?

Berk Bonebonce

700c is the standard road size; some might call it 28". Some kiddies racing bikes come with smaller, 650c wheels. The 650c size is the same as 26" mountain bike wheel size.

650c wheel size offers advantages for children and small adults mostly because you can achieve a more proportioned bike with a better geometry. There is also a lower centre of gravity with 650c and this can result in better handling.

But in practice, and in a world of mass production, the bike industry likes 'standards', and 700c is the prevailing standard. All bike kit is pretty much made to the 700c standard - 650c and 700c wheels are not interchangeable in the same frame.

In the case of an 11-year-old I would be inclined to head in the direction of 700c, and escpacially if the child is large or is likely to hit a growing spurt. But if the child is small and you want him/her to really excell at the sport of cycling, and you have plenty of money to throw around, a road bike with 650c wheels might be the best option.

Search for a specialist who sells childrens road bikes, eg. Isla Bikes.

Monty Dog

^ 650c is not the same as 26" MTB - they are not interchangeable - 650c is 571mm ETRTO whereas 26" MTB is 559mm.

To the OP, the simple question is what size of frame your 11 yo needs- if they can ride something with a toptube of >500mm then a 700c bike is suitable, anything smaller is almost impossible to construct without problems of wheel overlap and weird geometry/handling.

scherrit

Yup a smaller rider in this house rides a 48.5mm effective top tube and no 700c frame would ever work for her.

If you look at geometry charts, you'll see that the cheating starts even before 500mm top tubes- from 520mm manufacturers are often offering silly steep seat tubes and lazy head angles. This gives a (measured) shorter top tube which you can't really rely on, as putting the rider back where they belong with respect to the BB "steals" back some the apparent top tube shortening.