Frame sizing for riding position and dropper posts

Spagoose

I'm planning on buying the seemingly popular VooDoo Bizango and am agonizing over frame size. I'm 173cm/5'8", 31"inseam and a 178cm arm span so I am between small and medium.

Halfords don't have any 16" VooDoo bikes to try near me and said they can't order them in just for me to try but I did try an 18" Bizango.

As far as I can tell the reach is okay but I have only about 4.5" of exposed seat tube when the saddle is at the correct height and I'm only 2" above the lowest the seat post can go anyway.

First issue is that I think I will stuggle to fit a dropper post in without it being too high, and I wanted at least a 100mm dropper, preferable a 125mm.

Secondly the saddle is also below the handlebars, with the top of the saddle roughly at the same height as the top of the head tube. I feel like I should be sitting higher than the handlebars or at least level with them at a minumum and I'm doubtful moving the spacers will achieve that.

Standover is about ~1 but I know it's not really relevant to sizing but is slightly on the tall side.

Infact the image halfords uses for the Bizango is a fairly accurate depiction of what it looked like when I got the saddle height right for me:
https://i.imgur.com/5NoHkjk.jpg

The question is, is this bike too big as is? Should I forget about having a dropper? Any similar sized riders/bizango owners out there that could shed some light on the way forward?

Thanks

steve_sordy

I am not a Bizango owner, nor have I ever ridden one, but all the bikes I've had did have their saddle about level with the bars, slightly higher if anything. It sounds like the 18" bike is too big for you.

I'd find a Halfords with a 16" bike, or is prepared to get one in for you to try. If it fits buy it from them. The first shop can sod off!

Spagoose

steve_sordy wrote:

It sounds like the 18" bike is too big for you.

While dropping to a 16" would probably solve the dropper post fit issue, how would that actually affect being lower than handebars? The seat tube would be lower be 2" so the saddle post would be extended 2" extra, ultimately sitting at the same overall height.

I'm under the impression that the head tube/stack and hence handlebars would still be the same height between all the sizes as the fork, wheel and head tube are all the same size, so the end result is that you are in the same spot.

robertpb

That saddle looks too low even for me at 5'5", how are you setting up the saddle.

My saddle is set at 33.5 inches from the lowest position of the pedal to the top of the saddle just as a guide.

steve_sordy

Spagoose wrote:

............

While dropping to a 16" would probably solve the dropper post fit issue, how would that actually affect being lower than handebars? The seat tube would be lower be 2" so the saddle post would be extended 2" extra, ultimately sitting at the same overall height.

I'm under the impression that the head tube/stack and hence handlebars would still be the same height between all the sizes as the fork, wheel and head tube are all the same size, so the end result is that you are in the same spot.

Yes the BB height will probably be the same across the range, and probably the rear centre too and sometimes the head tube too. But the rest of the bike dimensions will change. So the reach and the stack will steadily get bigger as the frame size increases. If it didn't then why have different sized bikes? They need to change to allow for the difference between the heights of the customers.

Irrespective of what sized bike you will be sat on, once you have the saddle at the correct height for you, you will be sitting at the same height. It's how the rest of the bike fits you that is then important. Where are your knees with respect to the bottom bracket so that you can get an efficient pedalling position and without knee pain? Where are the bars so that you don't feel too cramped or stretched out? And finally to your first question, where is your saddle with respect to the top of the seat tube, so that you can raise and lower the saddle through the range required (manually or by dropper).

Different bikes have different geometry and design ideas. Some will suit you and some will not. But because other people have different proportions to you, bikes that fit you perfectly, won't feel so good to them. Which is why a test ride is always recommended.

Spagoose

robertpb wrote:

That saddle looks too low even for me at 5'5", how are you setting up the saddle.

My saddle is set at 33.5 inches from the lowest position of the pedal to the top of the saddle just as a guide.

I 100% agree it looks too low, I'm doing the normal full leg heel extension to give a slight knee bend, I couldn't go much higher without my legs being fully straight at the bottom of the crank.

steve_sordy wrote:

So the reach and the stack will steadily get bigger as the frame size increases. If it didn't then why have different sized bikes? They need to change to allow for the difference between the heights of the customers.

Ah I guess I misunderstood then, I knew that reach increased between sizes but I thought that difference in stack between different sizes of the same model would only differ by differences in head tube length and angle, which would probably be only minor, and in this case there are the same anyway.

3wheeler

Try the 16 if you can. Main thing to check will be the reach - if it's too short then don't buy it, you fit shorter stems but I wouldn't suggest fitting longer.
The photo of the bike doesn't help much, as soon as you sit on it the fork will compress by an inch or tow anyway, and there's a bunch of spacers under the stem that can be removed to lower the bar height.

kajjal

I am very tall but with a longer body and get stuck between bike sizes.

The rough guide is if a bike is a bit too small for you it can be adjusted to fit, if it is too large for you then there is little you can do. For my road bike I went with the smaller size and flipped the stem upright to get the riding position I wanted.

For my FS mountain bike I went for the larger size as it felt better and bought a shorter stem flipped downwards to get the riding position I wanted. Both bikes work very well for me. If you want to use a dropper post then you have to measure the minimum post you need and also the post for the saddle height you will ride the bike at normally.

Reach and stack are a useful guide but they don't consider what stem is fitted or where the spacers are positioned.

Spagoose

3wheeler wrote:

Try the 16 if you can. Main thing to check will be the reach - if it's too short then don't buy it, you fit shorter stems but I wouldn't suggest fitting longer.
The photo of the bike doesn't help much, as soon as you sit on it the fork will compress by an inch or tow anyway, and there's a bunch of spacers under the stem that can be removed to lower the bar height.

I finally found a 16" to try and it was indeed too short in the reach department. I agree with not wanting to add a longer stem so I think this bike in particular is not for me.

The Rookie

Its a problem with 29ers and suspension that even a short head tube puts the stem quite high, of course you can flip the stem and that will lower the bars compared to the top of the headtube by circa 15mm (based on a 6 degree 70mm stem).