Effect of longer stem

HonestAl

Help please. I'm considering a new bike. I've got a long body and relatively short legs. Considering what I'm keen on buying I fall between a couple of frame sizes. The problem can be solved by going for a "medium" frame size or the next size down, and a slightly longer stem. We're talking 120 mm versus 100 mm.

Obviously a smaller frame will have an effect on the handling of the bike, and I presume it'll just make the ride a bit more animated, which is no bad thing. I'm a bit more lost when it comes to the likely effect of the longer stem.

Putting the effect of the frame size aside, what's does lengthening a stem do? It seems to me that putting the handlebars farther out over the wheel would make the steering slightly less responsive, but I've no idea if that's true. Or if it IS true, does it make a noticeable difference?

Thanks for any replies in advance

redddraggon

Looking at the Top Length is misleading, especially if you keep the saddle position in relation to the BB constant, as the STA changes.

E.g. 54cm frame (Seattube angle = 73, TT = 545mm) with zero layback post and a 11cm stem

to a

52cm frame (Seattube angle = 74, TT = 535mm). To get the "same fit" I'd still need to use a 11cm stem, as the TT length only decreases by 1cm, but I'd need 1cm more of setback to be comfortable, effectively wiping out the decrease in TT length.

So don't assume if the TT is 2cm shorter, that you can use a stem 2cm longer...you need to factor in the seat tube angle.

However the advantage of going to a smaller frame if you've got proportionally shorter legs, would be a shorter headtube, so you can still get low.

Garry H

Yes, it's true. There are sure to be other effectes as well. If I were you i would fork out on a proper bike fit, otherwise you'll be pi**ing about buying new stems all the time, like I did. There was a good article on this in Cycling Weakly a couple of weeks ago. Compared two identical bu=ikes in different sizes, made to fit the same person.

ghostynlr

Was wondering about this myself, currently looking at a Giant Tcr Advanced 3, problem is i currently ride Specialized Roubiax which is a 52cm frame, the giant is 53.5cm. Would i be right in thinking that the TT length won't change that much really? Haven't had a chance to test ride the giant yet, so i can't tell.

redddraggon

ghostynlr wrote:

Was wondering about this myself, currently looking at a Giant Tcr Advanced 3, problem is i currently ride Specialized Roubiax which is a 52cm frame, the giant is 53.5cm. Would i be right in thinking that the TT length won't change that much really? Haven't had a chance to test ride the giant yet, so i can't tell.

Roubaix 52cm
TCR 53.5cm

Two totally different size bikes there....

Roubaix 52cm has 53.7cm top tube 14.5cm headtube

TCR 53.5cm 57.0cm top tube 17.0cm headtube

Totally different sizes, and that's before you even start taking the angles into account.

ghostynlr

How much diferent is the 50cm frame, as that 53.5cm one has thrown me a bit. The Spez is a very good fit, but i like the look of the Giant.

redddraggon

The 46.5cm Giant has the closest Geometry to the 52cm Roubaix. 535mm TT and 13cm headtube

The Giant has a 1.5cm shorter headtube, but that is expected when you consider the Giant is a race frame and the Roubaix a "comfort" frame.

ghostynlr

Cheers mate.

on-yer-bike

Go to the Cervelo website it explains what Red Dragon is saying. I have a 54 Spec Allez and a 56 Cervelo RS the former has a 110 stem the latter a 100. The reach on the Allez is greater although the tt is much shorter than 10 mm. Some fitters would put you on a bigger frame to get you the reach at the expense of very little seat tube showing.

maddog 2

some good posts there Red

for the OP, check out the manufacturers websites for geometry info.

As for longer/shorter stems, a longer stem slows the steering down (as well as other things). You can see in MTBing the trend has been to shorten the stem over the last few years, to counteract the slacker head angles and longer forks that are being run, and maintain a decent, quick steering response

If it was a straight fight between a 56cm frame and a 10cm stem, and a 54cm and a 12cm (all else being equal) then I'd say the 56 would be the better option. But the best option is to ride both bikes and see which you prefer.