crisklm

Hi,
i own a road bike and i am planning to buy a gravel bike.
I will use the gravel bike for quite long rides (5-6 hours) on asphalt and gravel.
what i am not sure of is the sizing of the new bike.
maybe you can help me?

i am 171cm tall with 76cm inseam
my road bike has :
TT=535mm
Reach=377mm
Stack=546mm
this bike fits me perfect.

the gravel bike, which i have to buy without testing has the following measurement:
TT=519mm
Reach=365mm
Stack=548mm

my concern is that the gravel bike is to small.

what do you think ?

thanks and sorry for my poor english

Steve B.

I tend to use “effective top tube” as the key measurement. All 3 of my road bikes are either 56cm ETT, or a 55 that has a 10mm longer stem than the 56 bikes, thus I would generally duplicate the measurements of the road bike if you think that’s a correct fit. I did this with my Cannondale Topstone, it fits perfectly,

mstateglfr 

Assuming the head tube angle isnt drastically different, you could match the cockpit fit on your road bike with spacer swaps and a different stem(length/angle).
Whether you want to match the fit exactly is something to consider.

SoSmellyAir

It seems you are trying to find a gravel bike with the same stack measurement as your road bike. But many gravel bikes have high stack measurements than road bikes. So as Steve B. said, try to compare the bikes by their respective Effective Top Tube lengths.

crisklm

My inseam is quite small to my body ratio, so i dont have many options regarding standover hight fitting.
So i compared reach and effective TT on the 2 bikes.
Effective TT is 16mm smaller on the gravel bike.
Reach as well is 12mm shorter.

Steve B.

if you have a good fit on your current road bike, I would not be getting a gravel that was that much smaller. 16 cm is easily a size smaller. Wrong bike

crisklm

yes, i thought my road bike is a good fit.
but today i took a picture of me sitting on the bike and i was told that my arms are to stretched .
i would have posted the picture here, but i am not allowed

mstateglfr 

I am guessing the STA of the gravel bike is steeper than your road bike, and that is what makes the ETT shorter? Regardless, a 16mm TT difference can often be negated with a saddle adjustment. Going from 0 offset to back 16mm would be the change.

crisklm

STA on the road bike is 74.
The STA on the gravel bike is 74.25.
not a big difference

SoSmellyAir

How about comparing your existing road bike to the same gravel bike but one size bigger?

SoSmellyAir

No, saddle adjustment, including its fore/aft positioning, should be set relative to the bottom bracket, to optimize pedaling. Saddle fore/aft should not be set to compensate for reach; doing so might negatively affect balance, e.g., too much weight supported by arms and hands. Reach can be compensated (within reason) by stem length.

mstateglfr 

Ha, I said this same thing today in the Hot or Not thread in the Road forum.
Yes, I am well aware of how saddle setback should be set as well as stem length.

As you can see, earlier I guessed the STA was different. That would have, in past, explained the difference in vtt length. My comment about saddle adjustment was based on assuming the STA was different.
Since the STA is only .25deg different, my comment about saddle adjustment compensating for that difference is largely irrelevant.

mstateglfr 

Will you reveal what bikes you are talking about? I am befuddled as to how some of this geometry equates to actual bikes.

Steve B.

I would not be trying to make an incorrect bike size be closer to correct by assuming you can place the seat back on the rails. Bad advice, IMO.

mstateglfr 

OK, again, I guessed wrong in STA and posted comments based on that wrong guess.
I agree that moving the seatpost to adjust only for effective sitting reach is a bad idea. Saddle position should be set for maximum power output and knee/hip comfort.
As I posted early on, a stem swap can easily offset the difference in frame reach.


My apologies for that incorrect guess. Hopefully 2 explanations in the thread will be enough. Fingers crossed.

crisklm

its a second hand bike, so unfortunately i don´t get to choose a different size

crisklm

my current road bike is a Bianchi Via Nirone 7 2017 size 53.
the gravel bike which i´m after is a Rose Backroad AL 2021 size 51

crisklm

i looked into different bike brands and what i noticed is that for the same size the Rose bikes have the shortest reach.

for example the next size (53) has a reach of just 368.5 mm.

t2p

something to keep in mind

and while this might not influence top tube length (selection) - it can effect stem length (selection)

if you are going from rim brake to hydraulic disc brake - the hydraulic disc brake / shifter hoods can sit out further than rim brake / shifter hoods

crisklm

in the first post i wrote that the road bike fits me perfect... but from what i read i don't think it's the case anymore.
riding , i always hold my hands on the top corner of the handlebars ( called ramps / shoulders) and never on the brake/ shifter hoods, because i dont feel comfortable
the reach might be a little too big for me , so the 12mm shorter reach on the Rose bike should be ok

cyclezen

I'm not familiar with the specifics of either bike, so some general comments to consider.
once you have your saddle position set then the actual 'reach' to your position on the bars has 3 considerations, the distance from saddle (whatever you use for your sitzbone setting) to the steerer tube center, then the length & angle of stem and then the 'reach' from the stem bar clamp to where you mainly ride - if 'on the hoods' then that measurement - bars have different 'reaches.
So the sum of those 3. Also bar width has a very slight effect.
On your road bike, if you're not comfortable riding On The Hoods, then experimenting with varying stem lengths might help that. Also, handlebars with shorter reach is worth investigation.
That said.
When I first started looking at gravel bikes, they ALL had signfcantly shorter final/total reach than any of my road bikes - even in a larger size. So I decided to ignore that. Deciding that a long stem would handle the difference of 10 to 15 mm in total reach.
After riding the gravel bike, unchanged, I was having no issues with the shorter reach. Generally I like the slightly more upright position/posture for seeing better the surface ahead. What I ride is not graded gravel roads, it's mostly what I call 'mountain biking Light' - single track without heavy technical stuff, like rock gardens or hairy descents or close contact to rcks and trees.
Certainly not the 'aero' position I search for when riding real 'road'.
You say the Rose is 'used', so maybe you can get a short ride on it? Even after a short distance, I can usually make determinations on the existing setup/position on a bike, and then go from there to make position modifications.
Making 'adjustments', when it comes to stem and bar can be complicated of the bike has proprietary fork/stem/bar parts... worth considering or certainly noting...
Other things can (and do) have a great effect on how a bike handles - like 'Front -Center', which is the dimension from center of BB to center of Front wheel (the hub).
The numbers you quote are all workable - go test ride, if possible.
Ride On
Yuri

SoSmellyAir

The ramps are an occasional resting spot. You should try to ride on the hoods most of the time for quicker access to the brake levers, in case of emergencies.

You will soon get to 10 posts and post a photo of your current bike from the side, so that an imaginary line between your camera lens and where your stem clamps onto your steerer is parallel to the ground, so others can chime in on your handlebar setup.

crisklm

Hi Yuri,

I appreciate the information, i will take it in consideration
i agree , a test ride would have been the best thing.
unfortunately the bike is 600km away

crisklm

i didn´t know this until yesterday, that the standard (neutral) riding position is with the hands on the hoods. i never rode this way, but yeah it makes sense

crisklm

this is my position on the bike

https://i.postimg.cc/xjmQR3Z1/IMG-004509.jpg