Talk me out of a XXL Crust Bombora

[calumf50]

After owning a bunch of 58, 60cm frames I’m finally coming to terms with looking for a bike with a longer ST. My fit is typically 86cm C-T of saddle, so as you can imagine that usually a lot of exposed post, and flex... Unfortunately I have the upper proportions of a 58-60cm frame, so looking for something long and relatively short, with a relatively low stack height.

The xxl crust seems to tick all the boxes, if a little tall. Anyone know of any thing else I should look at, before going full custom.

Must have discs, 700x45 clearance minimum, low ish trail for rando bag set up. Was also looking at the 61T fairlight allthough this doesn’t quite satisfy my long ST desire.

[yinzerniner]

Originally Posted by calumf50

After owning a bunch of 58, 60cm frames I’m finally coming to terms with looking for a bike with a longer ST. My fit is typically 86cm C-T of saddle, so as you can imagine that usually a lot of exposed post, and flex... Unfortunately I have the upper proportions of a 58-60cm frame, so looking for something long and relatively short, with a relatively low stack height.

The xxl crust seems to tick all the boxes, if a little tall. Anyone know of any thing else I should look at, before going full custom.

Must have discs, 700x45 clearance minimum, low ish trail for rando bag set up. Was also looking at the 61T fairlight allthough this doesn’t quite satisfy my long ST desire.

Only thing I couldn’t understand with the bombora is the high BB. It’s roughly 64mm of drip, which when paired with a larger tire means youre center of balance is pretty high. Since you’re already in a higher position due to your saddle height this may or not affect you, but having ridden bikes with higher BBs I hate the feeling.

If the geo works for you then seems like a nice ride otherwise, and really like their paint.

[EB]

The Bombora is designed around 650b wheels - that might explain the higher BB? It does technically work with 700c, but you’re sacrificing a lot of its available tire clearance. When a bike builder says a frame is for a certain wheel size I tend to listen - likely the handling will not be as intended with 700c.

[calumf50]

Originally Posted by yinzerniner

Only thing I couldn’t understand with the bombora is the high BB. It’s roughly 64mm of drip, which when paired with a larger tire means youre center of balance is pretty high. Since you’re already in a higher position due to your saddle height this may or not affect you, but having ridden bikes with higher BBs I hate the feeling.

If the geo works for you then seems like a nice ride otherwise, and really like their paint.

That’s interesting, I never really pay much attention to drop, but its 18mm difference with the frame I’m looking to replace. I don’t feel like I’ll notice it that being said.

[calumf50]

Originally Posted by EB

The Bombora is designed around 650b wheels - that might explain the higher BB? It does technically work with 700c, but you’re sacrificing a lot of its available tire clearance. When a bike builder says a frame is for a certain wheel size I tend to listen - likely the handling will not be as intended with 700c.

Thanks for the clarification

[mstateglfr]

Hey OP-
- what stack and reach do you want exactly? The Crust XXL is hardly short in reach and you mention wanting lower stack...and you mention it isn't.

- the bb drop of that Crust is really unappealing to me, especially since it will be further highlighted due to the large tire clearance.

- I was going to suggest a Fairlight since each size comes in T and R geometry. I figured one would for sure work, but you've already considered it.
I have a 61T Fairlight Secan and am 6'5 so there is a lot of seatpost, but don't really think about it much. There is 225mm of exposed seatpost from collar to clamp and my saddle is set 850mm center of BB to top of saddle.

- a Black Mountain MC would give you limited exposed seatpost...but it's rim brake. Mine has 135mm of exposed seatpost from seat collar to rail clamp.

Maybe a Black Mountain Mod Zero since it has disc brakes? The trail of this frame is similar to my MC and I happily ride with a front basket all the time.
...not sure if the tt angle is too much for what you want.

[mstateglfr]

Originally Posted by calumf50

That’s interesting, I never really pay much attention to drop, but its 18mm difference with the frame I’m looking to replace. I don’t feel like I’ll notice it that being said.

I am pretty sure I can notice 7mm between my old gravel frame(now commute) and my current gravel frame.
And I can definitely feel the bb drop difference between my main road bike and a 90s Cannondale caad3 frame that has me perched up, even tjiught it's probably only like 6mm or so.


In practice, that stuff usually doesn't actually make much difference and I adjust quickly. A lower bb drop is nice for bikes with big tires though. You ride 'in' rather than 'atop' the bike.

[EB]

Originally Posted by mstateglfr

I am pretty sure I can notice 7mm between my old gravel frame(now commute) and my current gravel frame.
And I can definitely feel the bb drop difference between my main road bike and a 90s Cannondale caad3 frame that has me perched up, even tjiught it's probably only like 6mm or so.


In practice, that stuff usually doesn't actually make much difference and I adjust quickly. A lower bb drop is nice for bikes with big tires though. You ride 'in' rather than 'atop' the bike.

For the Bombora at least, ride height will depend on which wheels and tires you would run.

For 650b with a 2.1” tire, tire diameter will be roughly 690cm. For 700c with a 45mm tire, tire diameter will be roughly 713mm. So the 650b setup will be roughly 1cm lower to the ground, relative to the axles - even lower if you chose a narrower 650b tire like 48mm. Of course for both setups the cranks and thus your feet have the same relationship to the axles, but with the smaller wheel diameter, less BB drop keeps your cranks from falling closer to the ground, which might be desirable depending on the use case and how long your cranks are.

[calumf50]

Originally Posted by mstateglfr

Hey OP-
- what stack and reach do you want exactly? The Crust XXL is hardly short in reach and you mention wanting lower stack...and you mention it isn't.

- the bb drop of that Crust is really unappealing to me, especially since it will be further highlighted due to the large tire clearance.

- I was going to suggest a Fairlight since each size comes in T and R geometry. I figured one would for sure work, but you've already considered it.
I have a 61T Fairlight Secan and am 6'5 so there is a lot of seatpost, but don't really think about it much. There is 225mm of exposed seatpost from collar to clamp and my saddle is set 850mm center of BB to top of saddle.

- a Black Mountain MC would give you limited exposed seatpost...but it's rim brake. Mine has 135mm of exposed seatpost from seat collar to rail clamp.

Maybe a Black Mountain Mod Zero since it has disc brakes? The trail of this frame is similar to my MC and I happily ride with a front basket all the time.
...not sure if the tt angle is too much for what you want.

Using my XL Marin Headlands as a reference. The Bombora has 10mm less reach and 120mm more ST

[yinzerniner]

Originally Posted by calumf50

Using my XL Marin Headlands as a reference. The Bombora has 10mm less reach and 120mm more ST

That headlands has an abnormally short ST, more like the newer style off-road drop bar bikes that take a lot of geo figures from mtb


If flex/movement at the saddle is a concern due then a long alloy model vs a carbon post will most certainly alleviate it. Also the steel frame at such a larger size will certainly introduce flex vs smaller frames.

You might be better off with something like the canyon grizl. Alloy frame in the larger size will probably be stiffer than steel, and the geo is similar but with a deeper BB drop and slightly lower stack. Trail calculates as about 70mm for either bike, which seems a bit on the high side if you’re gonna load up the fork

https://geometrygeeks.bike/compare/c...-7-2021-2xl-1/

[mstateglfr]

Originally Posted by calumf50

Using my XL Marin Headlands as a reference. The Bombora has 10mm less reach and 120mm more ST

Interpreting your first post and this one, you want the stack height of your Marin with a shorter reach? Not sure what an 'xl' Marin is as the site uses numbers, but I think it's size 60, based on the reach difference.

I will say that a gravel bike with 638.7mm stack and 426.8mm reach is pretty stretched, even for that stack height.

The largest AC Cosmic Stallion has 633.8 stack and 410.2mm reach.
The largest Trek Checkpoint has 639mm stack and 417mm reach.
A 58t Fairlight Secan has 638mm stack and 394mm reach.
A 61r Fairlight Secan has 612mm stack and 410mm reach.




I could go on and on, but hopefully you see that the Marin is on the long side of things for reach.
Anyways, if you first figure the stack and reach that you want, that will probably go a long ways towards finding a frame that fits, and then you can further narrow down possible frames based on top tube angle so you don't have much seat post exposed.
Is the exposed seat tube a cosmetic dislike or flex/feel dislike? Maybe use a stiffer seatpost if the current one flexes too much.

[clyde the point]

https://www.pinkbike.com/buysell/3825417/

That saddle is about 83 as you see it. Otherwise, it's your bike or F/F

[calumf50]

Originally Posted by mstateglfr

Interpreting your first post and this one, you want the stack height of your Marin with a shorter reach? Not sure what an 'xl' Marin is as the site uses numbers, but I think it's size 60, based on the reach difference.

I will say that a gravel bike with 638.7mm stack and 426.8mm reach is pretty stretched, even for that stack height.

The largest AC Cosmic Stallion has 633.8 stack and 410.2mm reach.
The largest Trek Checkpoint has 639mm stack and 417mm reach.
A 58t Fairlight Secan has 638mm stack and 394mm reach.
A 61r Fairlight Secan has 612mm stack and 410mm reach.




I could go on and on, but hopefully you see that the Marin is on the long side of things for reach.
Anyways, if you first figure the stack and reach that you want, that will probably go a long ways towards finding a frame that fits, and then you can further narrow down possible frames based on top tube angle so you don't have much seat post exposed.
Is the exposed seat tube a cosmetic dislike or flex/feel dislike? Maybe use a stiffer seatpost if the current one flexes too much.

Thanks for taking the time to write this, lots to think about here. Regarding the seatpost, mostly aesthetic, however the flex is annoying. I’ll start with changing it out as suggested.

[mstateglfr]

Originally Posted by calumf50

Thanks for taking the time to write this, lots to think about here. Regarding the seatpost, mostly aesthetic, however the flex is annoying. I’ll start with changing it out as suggested.

Hope my earlier posts didn't come off as judgy, and apologies if they did. I get that aesthetics matter, especially for us leggier folk who already ride bikes thst sometimes have goofy proportions.

Other bikes to consider that may meet what you are looking for-
https://pelagobicycles.com/stavanger/ - low trail, steel, wide tire fits, disc brake. Stack may be too high compared to reach or seat tube length.
https://www.somafab.com/archives/pro...ble-cross-disc - the 62 size has a longer seat tube, less reach than your Marin, and clearance for 45mm tires. It has QR dropouts, but if you got a 50mm offset fork you would have wide tire bike with trail that is on the lower end of the spectrum(58mm).

[TimD]

Originally Posted by clyde the point

https://www.pinkbike.com/buysell/3825417/

That saddle is about 83 as you see it. Otherwise, it's your bike or F/F

Great looking bike, just my size...