Bike Geometry

[Hont]

I'm looking at buying a new bike. On my current model I feel a bit too stretched out (i.e. arms stretched forward, sitting on the end of the saddle etc), so I've been thinking about getting a slightly smaller frame for the new one. Here, however I am confused.

Looking at the dimension differences for frame sizes, most offer only a 10ml reduction in length of top tube for each size difference, so a bike recommended for someone 5'1", for example, has a top tube only 60ml shorter than one for someone who is 6'1". That seems not enough to me, even if you take smaller stems into consideration. What am I missing? How is someone a foot shorter able to comfortably reach the bars when reach is only reduced by 80ml or so?

Do shorter people have proportionally longer bodies and arms? Or is there some other aspect of the geometry that affects reach?

EDIT. It probably is the stems isn't it. I was forgetting that you can get 60ml stems these days.

 

[Fletch456]

I would go to a shop that does a bike fitting either by a member of staff having lots of experience and skill or one of the systems that are common now like BG or Retul. Fit is very important in my book and worth hunting out a shop that has someone who knows that they are talking about.

Bike geometry seems to vary significantly between some manufacturers so what may change between tube lengths for one may not be the same for another.

 

[cyberknight]

Try getting a shorter stem assuming the rest of the bike fits, 10 minute job to change it and you can pick one up for under £10

http://www.jimlangle...rank/bikefit.ht

For a road bike i find whilst on the drops if your front wheel hub is obscured by the handlebars then it feels about right to me.

I have a proportionally short torso for my size so i always have to get a slighlty shorter stem for the bike fit to work.

I ride a 52-54 although for my leg length i could easily ride a 56 cm but it gives me back ache as i am too stretched out even with a 80 mm stem.

 

[Hont]

Well the reason I'm looking at a new bike is not because of this problem, but I think I will get a smaller stem as the old bike will be the new winter bike. I'll just have to find somewhere else for the bike computer.

 

[2Loose]

A stem that is shorter will make the bike 'twitchier'...ideally you should look down through the stem\handlebar clamp and be able to line it up with your front wheel hub bolts.

Can you saddle move forward a bit?

I felt very stretched out on my bike and got a 2cm shorter stem, but once fitted ended up moving the saddle back 1.5cm. Now it feels perfect!
Half a cm makes a lot of difference!