The Riding Gravel Forum
Register Calendar Latest Topics Chat
 
 
 


Reply
  Author   Comment   Page 1 of 2      1   2   Next
trener1

Starter
Registered:
Posts: 10
Reply with quote  #1 
I am wondering what the general consensus is regarding sizing for a gravel bike, do you usually more or less go with the same size as your road bike, or do you size down one size?.

My road bike's ETT is 54.5 and I run it with a 110 stem.

The gravel bike that I am looking at comes in a 54 with the same ett, but a 90 stem so that might be perfect.
It's also available as a 52 with a 53.5 ett, but that bike also has a slightly shorter wheelbase which might take away a (slight) touch of stability on fast descents.

What do you guys suggest?
0
DrSpoke

Senior Member
Registered:
Posts: 253
Reply with quote  #2 
That's pretty much what I do.  That is, pretty much road bike geo with a slightly shorter top tube and stem.  I usually angle the stem up on gravel rather than down as I do on a road bike.
0
drwelby

Senior Member
Registered:
Posts: 378
Reply with quote  #3 
Is the seat tube angle the same? It's a better comparison to look at stack and reach to compare sizing.
0
trener1

Starter
Registered:
Posts: 10
Reply with quote  #4 
Quote:
Originally Posted by DrSpoke
That's pretty much what I do.  That is, pretty much road bike geo with a slightly shorter top tube and stem.  I usually angle the stem up on gravel rather than down as I do on a road bike.


So are you suggesting that I go down one size?
0
trener1

Starter
Registered:
Posts: 10
Reply with quote  #5 
Quote:
Originally Posted by drwelby
Is the seat tube angle the same? It's a better comparison to look at stack and reach to compare sizing.


So the Seat tube angle on my 54 road bike is 73.5

On the gravel bike that I have my eye on 
the 54 comes in at 73 and the 
52 at 74.5
However I don't really understand these numbers.
Based on them, which would you recommend.



0
LewisQC

Member
Registered:
Posts: 94
Reply with quote  #6 
1+ about  stack and reach number, they are far better than TT too guesstimate if a bike will fit or to compare geo between different bike. 
0
trener1

Starter
Registered:
Posts: 10
Reply with quote  #7 
So based on those numbers which one sounds best? I don't understand how the stack/reach numbers work.
0
GHC

Member
Registered:
Posts: 62
Reply with quote  #8 
trener1

I am not going to directly answer your question in this first paragraph.   What I would do is try get fitted/sized on the bike you are looking at at a bike shop that services serious riders or similar if possible.  If you can't find that bike, find one with same geometry and get on to test.  If you aren't buying the bike from a LBS, lets say online, I would shoot them straight about why you are there.   I have done this, while offering to pay a fee for the service, and was quite surprised how accommodating they were .... because imo I offered to pay for what info I was looking for (they didn't take my money), but I would have been fine paying something...because the info had value to me, saved me from potentially having to attempt returns or being unhappy.   As I hadn't ordered the bike yet, imo they felt it was worth their time because they still had an opportunity to compete for my business.  In the end, they didn't carry the bike I was ordering (Ridley), and while their offerings were similar in geometry (which was handy), in the end they couldn't compete on price, particularly after considering the components on the online bike.  It was obvious to me, and them.  I later found the exact bike I was looking for at a different shop, and it was the smaller of the sizes I was between, and after testing that one, I ordered a size bigger online. After my bike arrived, I called my LBS and asked if they assembled boxed bikes for a fee .....and sure enough they did .... $90 if I remember correctly, which I was happy to pay when the bike came in. Admittedly the LBS's approach with me was probably aided by the fact that I had (and still do) done previous business with them. 

Now to you question about sizing, ignoring the first paragraph. Only you know if your current bike is just right, a little small, or a little big.  That should weigh into your decision, along with the angles others have mentioned.  Next, compare if your current post is offset or straight .... and the stem length is long or short, and depending on geometry of the bike, how much seat post you have showing.  If you are currently riding a back offset seat post and a long stem and a lot of seat post showing, I would tend to error on a bigger size if you are on the fence between two sizes on the new bike ......because if you are within centimeters, those things can easily be adjusted.  Beyond all that, stack and reach are what I pay attention to as others have mentioned. My two cents, ymmv

Edit adding:  I tend to want my gravel bike set up a little "more relaxed".  For me this means not as slammed....so when on the drops I am slightly more upright, with the option of being more upright when on the tops.  Gives me a lot of flexibility to move around on the bars when on long hard rough rides.  Also means I want a little more stack (which is why I would want to error on the larger bike if on the fence), and a slightly lower BB and slightly longer chain stay compared to a straight road bike.  But these are personal pref things. You definitely want the drops in play comfortably on gravel. 

Finally and respectfully, you need to spend some time and understand what the bike geometry measurements really mean and what they can do for you/how they effect the feel, if you don't already know....which is why I am back to the first paragraph which will allow you to ride a few different styles to aid your decision.

I apologize in advance if I have offended in any way, trying to help ..... have a roadie friend who bought a gravel bike based on road bike "size" ... he's a heck of a road rider, but on gravel his stack was way too low, couldn't spend any time on the drops when fatigued on rough stuff until he "fixed it" ... front end looks like a flag pole now and sports $$ bars to get it right, but he's riding.  Would have made more sense for him to research and ride before he bought.
0
drwelby

Senior Member
Registered:
Posts: 378
Reply with quote  #9 
You can plug the numbers into bikegeo.net and see the difference between the frames.


0
cjdaking

Member
Registered:
Posts: 59
Reply with quote  #10 
My road bike reach is almost identical to my gravel/cross bike reach. You're basically in the same position, so aligning these sizes should have you where you want to be
0
DrSpoke

Senior Member
Registered:
Posts: 253
Reply with quote  #11 
Quote:
Originally Posted by trener1


So are you suggesting that I go down one size?


It's not so much going down a full size.  Often, it seems, I am in between sizes.  In those instances, I generally go for the smaller size rather than the larger - but that is personal preference.  Generally, as re ETT, it might only be .5 cm or so. 

As others have stated, stack and reach are more reliable measurements of frame sizing especially in this day of sloping top tubes and fewer frame sizes per model among other things.  This measurement is a vertical and horizontal measurement based on the bottom bracket.  Accordingly, it allows for a better comparison among frames that top tube alone.  It's pretty easy to measure so a good place to start would be to measure or find the stack and reach of your current frame and go from there.  I also agree w/other above that a more relaxed (upright, endurance fit) riding position is preferred for gravel so a slightly shorter reach and more stack than your road bike help to achieve this.  Short stems and stems that are angled up also aid with this.
0
NoCoGreg

Senior Member
Registered:
Posts: 261
Reply with quote  #12 
A few thots...

+1 on the drwelby's suggestion to use the fit calculator!  

+1 on GHC's recommendation on getting fit properly.  To know if you want to go larger or smaller you must understand how you want the bike to fit and handle.  As GHC pointed out, a smaller frame may necessitate a "race fit".  Too large and there isn't clearance to straddle the top tube.

All my bikes (road, gravel, mountain) have the same saddle/pedal setup.  I want the mechanics of the pedal motion and muscle use to be the same.

The fit differences between the various bikes is with the reach and drop (saddle-to-bars).

My Tarmac race bike is setup with about 2.5" of drop.  The various gravel bikes have 0.5" to 2" less drop and 0.5" to 1" less reach than my Tarmac.  For more technical single track and jeep roads I prefer a more upright position.  If I'm going to be on fast gravel roads with a bunch of racers then I'll have more drop.

Increasing drop does several important things:
1. Most obvious the position is more aero.
2. Counter intuitively, more drop causes the abs to engage which provides more support for the back AND assists in generating more power.
3. Weight is shifted forward: increased weight on the arms and more power to the pedals will take weight off the seat. This will reduce fatigue in one's butt.
4. Reach increases as drop increases.  A small increase in drop can feel like a large increase in reach.

When looking at the size of a bike - IMO the key dimensions are Stack, Reach, and Standover and Wheelbase.  I prefer a larger frame because it generally has a longer wheelbase and the increased flex is usually an improvement.   I use the Stack, Reach and Standover to confirm I can fit a frame.  

One last note - the length of the stem affects how the steering feels.  A longer stem increases the lever arm from the bars to the steerer tube and it also move weight farther forward.  This isn't necessarily a bad thing, just something to be aware of.

Hope this helps,
Greg
0
chas

Avatar / Picture

Senior Member
Registered:
Posts: 347
Reply with quote  #13 
For me, the cockpit  (top tube length + stem) overshadows everything else, as everything else is pretty adjustable.
My cockpit is 65 cm = 55cm top tube + 100mm stem for example

I went down in size, but for gravel most people are going to want the larger size for stable decents (for my model the larger size had 20mm longer wheelbase)
Smaller is more agile, larger is more stable and better for what most people want for gravel.

So, unless you prize agility - get the larger of the two sizes.  



Stems in mountain bikes are interesting
racey bikes used the have very low long stems
now they have very high and short stems.

Reach is kind of an odd thing.  two bikes with the same cockpit length can have very different reach numbers based if they have different seat angles and/or different stem lengths.   Stack is usually highly adjustable.
0
NoCoGreg

Senior Member
Registered:
Posts: 261
Reply with quote  #14 
Quote:
Originally Posted by chas

Reach is kind of an odd thing.  two bikes with the same cockpit length can have very different reach numbers based if they have different seat angles and/or different stem lengths.   Stack is usually highly adjustable.

Yes exactly!

Yet I regularly find people who claim the top tube or seat tube measurement is all they need to determine if a bike will fit. Sigh...

Regarding your observation on mountain bikes having shorter stems, it also seems the headtube height (aka stack) has evolved to a much higher position. In rigid bikes increased stack becomes obvious because the increased stack usually shows up with a longer head tube.  Suspension forks need additional clearance needed for the fork brace etc. so the increased stack is much less obvious.
0
Skldmark

Member
Registered:
Posts: 76
Reply with quote  #15 
I have three cyclocross bikes , each a different brand. Size 49cm.,size 50cm., size 52cm. All fit close to the same. If anything the size 49cm. fits biggest. I’m saying it’s not the number, it’s the fit. Should you get a gravel bike that fits smaller than your road bike? Prolly knot.
But I setup my cross and gravel bikes with the hoods closer to me.
0
Possum

Starter
Registered:
Posts: 12
Reply with quote  #16 
Standover height !!! Check specs...
A 57cm cxbike has about the same Standover as a 60cm roadbike...those taller tires on same sized rims.
Personally, I prefer a little more space on my cx/gravel bikes so I don't rack my sack...cx mounts and dismounts have shown me this through the school of hard knocks
0
Volsung

Avatar / Picture

Senior Member
Registered:
Posts: 193
Reply with quote  #17 
Standover height only matters when you're not riding it or crashing.
0
Possum

Starter
Registered:
Posts: 12
Reply with quote  #18 
Or a PRO such as yourself
0
RobF

Member
Registered:
Posts: 26
Reply with quote  #19 

"Standover height only matters when you're not riding it or crashing."

How much does standover really matter when you're not riding it?  Usually when I stop for a moment I put 1 foot down first and lean the bike, not put both feet down and straddle it.  I'd give up standover to have a triangle with more room for bottles or bag.

0
Zurichman

Avatar / Picture

Senior Member
Registered:
Posts: 724
Reply with quote  #20 
I guess I just got lucky at my end. I thought the Raleigh bikes for me were sized a little bit bigger. I ride 57 cm Lemond bikes all day long. I went to my Raleigh shop and tried sizing for my bike/bikes. I bought the 56 cm and then had my gravel bike fitted the same as my road bike and it has worked out fine.

Zman

__________________
If it was easy it wouldn't be a memory. You just hope you don't have all your memories in the same ride. been there dun that Zman
0
chas

Avatar / Picture

Senior Member
Registered:
Posts: 347
Reply with quote  #21 
Quote:
Originally Posted by RobF

"Standover height only matters when you're not riding it or crashing."

How much does standover really matter when you're not riding it?  Usually when I stop for a moment I put 1 foot down first and lean the bike, not put both feet down and straddle it.  I'd give up standover to have a triangle with more room for bottles or bag.



Answer:  When it hits your crotch.

I agree with ya, most bikes have a compact geometry, and standover is not an issue, space in the triangle may be more of a priority.

I recently tried out two bikes.  Although I liked the larger size for gravel, the top tube was 84cm high, and my crotch is most 86.  For that reason alone I felt I should size down.

On my traditional sized (non compact) road bike, I have a horizontal top tube.  That leaves very little exposed stem on my seatpost.  Thus nice cushy carbon seat posts like my Specialized CG-R, or Canyon VCLS don't do anything to absorb bumps.  Its kinda frustrating.  but on a bike with a nice healthy dose of exposed seat post, they work very nicely.

Food for thought.


0
Possum

Starter
Registered:
Posts: 12
Reply with quote  #22 
Sorry, I was only sharing my experiences and opinion on cyclocross... Hoppin back on after dismounts for obstacles can be rough without a little clearance... Didn't expect a salty reply on this site...
Guess standover is only important for folks with balls...
0
RobF

Member
Registered:
Posts: 26
Reply with quote  #23 
That's a good point about having more exposed seatpost for more flex.
0
NoCoGreg

Senior Member
Registered:
Posts: 261
Reply with quote  #24 
Quote:
Originally Posted by Possum
Sorry, I was only sharing my experiences and opinion on cyclocross... Hoppin back on after dismounts for obstacles can be rough without a little clearance... Didn't expect a salty reply on this site... Guess standover is only important for folks with balls...

I've been fortunate and gravel hasn't required the kind of standover clearance I need for mountain biking (read - I'm able to keep the rubber side down on gravel). So I view the requirement for gravel clearance to be much more like that of a bike for touring or commuting.  But that's just my experience...

CX OTOH is a vastly different situation and my CX bike does have much more clearance.  I think there is some confusion in sizing because CX bikes do work well for gravel but the "typical" gravel rider won't be running while mounting. Again, just my experience. :-) 

Clearance on frames varies significantly.  For example the Raleigh Roker and DB Haanjo have less clearance than the Salsa Carbon Warbird and Niner RLT RDO which are semi-compact.  The Haanjo in my size has a much shorter TT so to get a good fit I would have to go with the XL which has a 34" standover and precious little clearance for the family jewels.
0
dangle

Senior Member
Registered:
Posts: 206
Reply with quote  #25 
Quote:
Originally Posted by Possum
Sorry, I was only sharing my experiences and opinion on cyclocross... Hoppin back on after dismounts for obstacles can be rough without a little clearance... Didn't expect a salty reply on this site... Guess standover is only important for folks with balls...


I would love to see a video of your CX remounts where standover comes into play.
0
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.