Understanding how different geometries compare

[alolympic]

So, I am drawing up my shortlist of gravel bikes, and starting to get a bamboozled with different geometries, and what that means in terms of how a bike would ride. Original thread here - https://www.pistonheads.com/gassing/topic.asp?h=0&...

So, I commute on an Orro Terra in a Medium.....https://www.orrobikes.com/shop/terra-gravel-105-hydro

I'm looking at the Open Up - https://opencycle.com/up and the Open Wide https://opencycle.com/wide/Specs

This site is great at giving side by side comparisons https://geometrygeeks.bike/compare/orro-terra-grav...
It also gives a pretty good glossary of terms, the problem is - I don't know what the combined changes would mean.......and I also don't therefore know which frame would actually be the right size
Anyone make sense for me, or point me to any more useful guides?......
Ta

[anonymous-user]

Go ride a few and see which feels best

Remember changing the stem length or saddle or tyres can make a significant difference to the way any giBen bike rides

[moonigan]

The key measurments are.
1. The saddle to BB measurment. Measure from the top of your saddle to middle point on your BB. This will be the same no matter what bike you ride but will impact the saddle to bar drop and reach depending on the frame. This assumes your saddle height is set correctly.

2. Stack and Reach also come into play. Generally a bigger reach measurment means a more racy or stretched out fit and a higher stack number relative to the the reach usually means a more relaxed seating position.

The reach on your Orro looks huge for a medium. I know for me anything approaching 380mm is a no go but I have a short torso and long legs so getting a good fit is always a challenge.

The geometry on the both the UP bikes looks different to your Orro with the WIDE being significantly more relaxed.

If you are looking to drop this kind of money on a bike have a proper fit and then you can give those numbers to OPEN who will help you out. You also might find they are not the bikes for you. I looked into one a few years ago but ended up with a Specialized Diverge instead.

[alolympic]

moonigan said:

The key measurments are.
1. The saddle to BB measurment. Measure from the top of your saddle to middle point on your BB. This will be the same no matter what bike you ride but will impact the saddle to bar drop and reach depending on the frame. This assumes your saddle height is set correctly.

2. Stack and Reach also come into play. Generally a bigger reach measurment means a more racy or stretched out fit and a higher stack number relative to the the reach usually means a more relaxed seating position.

The reach on your Orro looks huge for a medium. I know for me anything approaching 380mm is a no go but I have a short torso and long legs so getting a good fit is always a challenge.

The geometry on the both the UP bikes looks different to your Orro with the WIDE being significantly more relaxed.

If you are looking to drop this kind of money on a bike have a proper fit and then you can give those numbers to OPEN who will help you out. You also might find they are not the bikes for you. I looked into one a few years ago but ended up with a Specialized Diverge instead.

Thanks, very useful.
I have had a pro fit before (on my road bike) and I have these measurements.

[TCX]

Slightly longer wheel base than road/sportive 99-100cm,more fork rake,shorter seat tube,compact to allow more seat post compliance,clearance for wider tyres,or just get a bike n ride it,none are perfect,most are pretty good,I've old TCX cross bike does gravel as well as I need

[moonigan]

So using your saddle height from the bike fit you look like a large in both the Open bikes with the Upper looking an almost idendical match to your Orro. The Wide is slacker more relaxed geometry so easier to ride off road.

I put the geometry for the 3 bikes into a spreadsheet that I used when looking for suitable bikes using your Medium terra and a Large in the Open. The stack to reach ratio determines how racy or how relaxed the bike is with a bigger number being more relaxed. For reference the Cannondale CAAD10 (just about as racy a bike as you can buy) is 1.37

Adding/removing stem spacers will move this number up or down and will also alter the saddle to bar drop.



Not an exact science but it really helped me. As I said before send your bike fit info to Open and they will help.

Edited by moonigan on Tuesday 26th May 12:53

[alolympic]

Thanks so much Moonigan, really kind of you to run some numbers,
Interesting comparison. I must admit, after doing more and more rides on my xc bike with it’s more relaxed geometry, and the extra air in its tyres, I am leaning more to the WIDE than the UP now.
Cheers

[alolympic]

Interestingly (to me anyway) I rode my rigid 29er on a road route yesterday. Despite the much wider wheels and the more upfront riding position it felt amazing. Ran out of gears on fast descents but posted quite a few PR’s on little climbs and felt really quite fresh afterwards. I take this as a sign that I do well on a comfier bike.
Makes me think a more upright gravel bike like the Open Wide is the way to go....unless I just keep with the 29er 🤷‍♂️

[moonigan]

alolympic said:

Interestingly (to me anyway) I rode my rigid 29er on a road route yesterday. Despite the much wider wheels and the more upfront riding position it felt amazing. Ran out of gears on fast descents but posted quite a few PR’s on little climbs and felt really quite fresh afterwards. I take this as a sign that I do well on a comfier bike.
Makes me think a more upright gravel bike like the Open Wide is the way to go....unless I just keep with the 29er ?????

If you have a 29er rigid hard tail then it’s a really tough choice. I guess it will come down to the surface/terrain that you will ride. I have a few routes that are around 40 miles. One is flat and mostly off road and I will always take the gravel bike the others are the polar opposites and have lots of elevation and some really rough surfaces. On each route I’m probably 2mph faster on the gravel bike than than my mtb but the gravel bike is physically more challenging.

[alolympic]

moonigan said:

If you have a 29er rigid hard tail then it’s a really tough choice. I guess it will come down to the surface/terrain that you will ride. I have a few routes that are around 40 miles. One is flat and mostly off road and I will always take the gravel bike the others are the polar opposites and have lots of elevation and some really rough surfaces. On each route I’m probably 2mph faster on the gravel bike than than my mtb but the gravel bike is physically more challenging.

It’s made more difficult by the fact that my bike is actually lighter than most grave bikes out there. I’d keep it if it felt like it wasn’t quite so limited in its top gearing. It’s a 10 speed and I think ideally I would go 11 or 12 with a 10T top gear but that won’t be easy or cheap

[Exige46]

You can play with different stems and bars on here: https://www.velogicfit.com/frame-comparison if that helps

[moonigan]

alolympic said:

It’s made more difficult by the fact that my bike is actually lighter than most grave bikes out there. I’d keep it if it felt like it wasn’t quite so limited in its top gearing. It’s a 10 speed and I think ideally I would go 11 or 12 with a 10T top gear but that won’t be easy or cheap

Yep gearing is an issue. I have a double on both gravel and MTB with 48/32 - 11-34 on the gravel bike and 36/26 - 11-40 on the MTB and whilst lots of people say doubles are dead on MTB/Gravel I love it. The latest single ring 12 speed groupsets offer the same range as my MTB but I still think I'd stick with the double because I hate the big jumps you get between gears and I'm not getting any younger so the I might need the 26/45 gear more often.

Edited by moonigan on Friday 29th May 08:00