Frame sizes

[colinr]

What do the frame size numbers mean? E.g. how tall / what inside leg does the number equate to? Assuming standard geometry.

I ask because I'm looking for a cheap "pub bike" and have no idea what the classifieds are on about when they say 56cm frame.

Thanks.

 

[Davidc]

There are a number of guides on line - look in google.

Be careful though. With modern compact frames check the manufacturers sizing guide, as they can show unexpected results.

There's also a difference between road bike and mtb sizing.

The most important number imho is the standover height. That's the height of the crossbar top above ground. It needs to be low enough that you can stand with 2 feet on the ground, with clearance for your tender bits.

 

[colinr]

I googled it and got all confused. I'm only looking at road bikes and most cheap stuff isn't new enough to be compact (my compact frame is M, even less helpful!). So if a frame was 56cm, that's the height from ground to crossbar?

 

[MajorMantra]

I googled it and got all confused. I'm only looking at road bikes and most cheap stuff isn't new enough to be compact (my compact frame is M, even less helpful!). So if a frame was 56cm, that's the height from ground to crossbar?

No, it's usually from the centre of the bottom bracket the top of the seat tube measured along the seat tube. You should check though because sometimes people give a centre-to-centre measurement.

Matthew

 

[colinr]

Ta. My revised Googling estimates a 54cm frame, and I'll make sure I check where they're measuring from and to.

 

[gaz]

The most important number imho is the standover height. That's the height of the crossbar top above ground. It needs to be low enough that you can stand with 2 feet on the ground, with clearance for your tender bits.

Who stands over there bike with two feet on the ground?

 

[Sittingduck]

It depends from bike to bike. For example my Specialized Globe is a 55 but my Ribble Audax/Winter is a 48. Clearance from top tube to gonads is the same

I think Spesh give the length of the TT as their number, whereas other makes quote the seattube length...

 

[Davidc]

No, it's usually from the centre of the bottom bracket the top of the seat tube measured along the seat tube. You should check though because sometimes people give a centre-to-centre measurement.

Matthew

Agree - I've been looking for a bike for a while, and most are advertised with frame size wrong. Common errors are giving standover height or crossbar length.

 

[Davidc]

Who stands over there bike with two feet on the ground?

Lots of us - when stopped for a while but not getting off the bike.

 

[MajorMantra]

The most important number imho is the standover height. That's the height of the crossbar top above ground. It needs to be low enough that you can stand with 2 feet on the ground, with clearance for your tender bits.

Standover height is one of the least important measurements. Within reasonable limits for seat tubes, top tube length is probably the most important and in any case it tends to be similar to seat tube length for a typical road frame.

Unless you feel like paying for a proper bike fit the easiest way to assess your needs is to try a variety of bikes. One way you can do this is with test rides in bike shops - some are quite relaxed about letting you try things on grounds that even if you aren't going to buy from them that day, you may well be back if they're friendly.

Matthew

 

[Davidc]

Standover height is one of the least important measurements. Within reasonable limits for seat tubes, top tube length is probably the most important and in any case it tends to be similar to seat tube length for a typical road frame.

Unless you feel like paying for a proper bike fit the easiest way to assess your needs is to try a variety of bikes. One way you can do this is with test rides in bike shops - some are quite relaxed about letting you try things on grounds that even if you aren't going to buy from them that day, you may well be back if they're friendly.

Matthew

Agree totally - trying a bike is by far the best way to find out if it fits. Same as with clothes, the same size from two different manufacturers can be a very different fit.

There appear to be far less frame sizes than there once were, with more adjustment range on the bits attached to them, which can make life easier.

Don't agree with you about standover - I don't like crushed nuts!

 

[Randochap]

Bike size/fitting guide.

 

[colinr]

http://www.veloweb.ca/bikefit.html

Bike size/fitting guide

Very helpful, thanks. I should remember to check your site for this sort of things.