Bike Fit - ideal top tube length

[Dave G]

Hello all.

Does anyone know of a web resource which details the ideal effective length of a top tube? Actually, even better would be a resource which details the best reach to the hoods (including stem).

All resources I've found focus on seat tube length, which is of little use considering different manufacturers make frames with varying seat tube lengths (i.e. a medium giant isn't the same as medium trek etc).

I know a proper fit by a LBS is the best way, but I'm trying to look at something retrospectively.

I have a Planet X bike size 48cm seat tube, 54.7 eff top tube and a Trek 1.9, size 54cm seat tube and 53.9cm top tube. I'm trying to work out if one is too big/small. They both feel OK to ride, which is I suppose the main thing.

 

[spandex]

have a look at sheldon browns web site . http://www.sheldonbrown.com/frame-sizing.html and http://www.sheldonbrown.com/gloss_e-f.html#framesize

 

[Dave5N]

See beginners for something similar.

 

[Mortiroloboy]

Hello all.

Does anyone know of a web resource which details the ideal effective length of a top tube? Actually, even better would be a resource which details the best reach to the hoods (including stem).

All resources I've found focus on seat tube length, which is of little use considering different manufacturers make frames with varying seat tube lengths (i.e. a medium giant isn't the same as medium trek etc).

I know a proper fit by a LBS is the best way, but I'm trying to look at something retrospectively.

I have a Planet X bike size 48cm seat tube, 54.7 eff top tube and a Trek 1.9, size 54cm seat tube and 53.9cm top tube. I'm trying to work out if one is too big/small. They both feel OK to ride, which is I suppose the main thing.[/QUOTE]


You are being far too analytical, just get out and ride!

 

[monnet]

Top tubes matter but the key is the distance from the seat to the stem centre. If you can get that length similar on your bikes you're ok. Remember though that if you're keen to get the position right you also need to think about stem length, position of your saddle in relation to the bottom bracket, height difference between saddle and stem and the distance between the brake block nut and the stem.

To take mortiroloboy's point, I over analyse. My reason is that my 'good' bike is pretty much perfect so I try to replicate the position as best as possible but it's almost impossible so, ride and see how it feels.

 

[Monty Dog]

As your difference is less than 1cm, it would almost be imperceptable to most - unless you're Eddy Merckx who was exacting about his position following a crash. My bikes vary as much by 3cm in toptube - offset by longer stems and seatpost layback. Do some lumbar and stretching exercises too if you find it causes a problem.