Crust knowledge/experience for Bambora vs Evasion Lite

[Toby Whitfield]

I am looking for a new versatile rugged bike for bikepacking/rough gravel/all round use.

This is to complement my Weigle randonneur when I want something a bit more heavy duty and also a bit less precious.

I am looking at the Crust Bambora or Evasion lite. The Bambora takes a road crank, while the Evasion has a bit more tire clearance, but takes a wider crank. Has anyone compared the two? I'm thinking about flexibility - any real difference there? I'm also wondering about the Evasion crank, and what fits there. It has a 73mm shell. Are there reasonable options there for a 1 x crank with low Q?

I would like to run tires from 47-48 mm road tires to slightly wider knobbies (wider with the Evasion, which seems to be the main benefit of that model vs the Bambora).

Thanks for any thoughts
Toby

[satanas]

From my dictionary:

"Noun

bombora (plural bomboras)

(Australia) A shallow isolated piece of reef located a distance offshore."

Crust says the Bombora has a 68mm BB shell...

https://www.crustbikes.com/products/bombora/

...and they also say...

"Designed around a 1 X. A double will work, but you are on your own with figuring it out."

^ My assumption is that this means cable routing is only provided for 1x, so FD cabling woupd need to be improvised.

Given the 68mm shell, almost all cranks that aren't BB30 (or similar, like BBRight) ought to fit; Matt's personal bike used Dura-Ace 7400 cranks with a narrow-wide ring. If you're going to use 1x the most important thing will be to ensure suitable rings are available, and while narrow-wide rings exist for many common BCDs they do not for things like 5-pin cranks or RH. Chainline is also a consideration, and is not easily adjustable with some cranks; with square taper cranks this is simpler, or for some cranks various offset rings are available.

Later,
Stephen (who really dislikes 73mm BB shells)

[satanas]

PS: Russ at Path Less Pedaled has a Bombora and has reviewed and commented on it quite a bit; you may find some of his videos useful.

[Toby Whitfield]

Thanks Stephen. I'm trying to figure out the 73mm bottom bracket crank options. All the truly MTB options look quite high q, the best being the XTR 1x, but that is quite expensive and still not ideal. I'm trying to figure out whether I could use a square taper road crank for 1x with a slightly wider bottom bracket, which would keep the q reasonable. Of course, the Bambora is an obvious solution, but it is out of stock. If I could get one on Crust's stated in stock date of August that works for me, but I also wonder if COVID and the bike boom could slow things down.

If I could get something working on the Evasion Lite that has reasonable q, that might be a good alternative. I'm also curious about the tubing differences, but suspect they are quite similar. The fit is pretty close in the large sizes I'd be looking at.

[Justin Hughes]

I use a carbon SRAM XX with 156mm Q. It's 4 bolt 120mm BCD. Wolf Tooth makes narrow wide rings and there are likely others. 

[satanas]

^ I just bought a Q156 XX GXP crankset from UK eBay to go on a Salsa Cutthroat v1 frame with a $##@@! BB92 BB shell. There are a few people doing rings to suit, but not many; I'm sticking with 2x and 39x26. There was a Q156 XX1 GXP crank too (pre-Eagle) but they're getting very scarce; you can use a 4 bolt 1x ring on these, or a direct mount ring or spider, and even 2x on an NSB 104/64 spider.

I hate 73mm BB shells as they prevent the use of almost all road cranks, square taper possibly excepted. The other potential problems with square taper cranks are crank-to-chainstay clearance on a normal width BB, and chainline on a wider one. This can't really be assessed until you see the frame and can measure the external width across the chainstays ~190mm behind the centre of the BB shell.

Whilst XTR cranks are an option they have their issues:

1. The M985 cranks were available in 172.5mm - good for me - but the 88mm BCD leaves very few chainring choices; the original outer rings are both scarce and very expensive. Q is 163mm, low only by MTB standards.

2. The M9000 cranks (170/175 only, Q158mm) have even more expensive rings, and use weird chainring bolts and "nuts," so only XTR rings will fit, not XT, etc. These "nuts" are different for 1x and 2x(!), *very* expensive, and hard to find too; KCNC make cheaper ones, but good luck sourcing any.

Another "low Q" (for MTBs - 163mm) option is Rotor cranks, for instance:

https://www.ebay.com/itm/202827507736

^ Figuring out which BB and spacers you need for Rotor cranks can be be annoying, and small BB parts (for any cranks) are often scarce and expensive; with Shimano there aren't any.

IMHO, 73mm shells are best avoided unless you want really wide tyres (>54mm) and are okay with running MTB cranks. Note too than many MTB chainstays won't clear low Q MTB cranks. The Q158 M9000 cranks have a bit less clearance than Q156 SRAM, but even the Q163 M985 would't clear on Niner or some Ibis frames, and no doubt many others; Niner used to state this on their website. :-(

Note too that manufacturers are very conservative about what they see as acceptable crank-to-chainstay clearance, and anything less than 5-6mm (or more) will be looked down on. In practice you can get away with less, but this depends on how flexible the frame and crankset is and how huge the rider is, hence the paranoia.

If you see any mention of Boost 148 spacing the chances of anything less than ~170mm Q cranks clearing are slim to none.

Best of luck,
Stephen

[thoma...@gmail.com]

If you're looking for low Q, stick with the Bombora. Trying to keep a low Q on a MTB bb shell is an expensive hassle. If you want to go that way, using a low-q square taper crank with a chain retaining 1x ring is the cheapest but requires the most fiddling.

[satanas]

^ Agreed!

On an older Surly Troll, with a 73mm shell but relatively narrow chainstays by current MTB standards, the lowest Q factor I could achieve was ~157mm, and that required fiddling with spacers and was for a Rohloff chainline (54mm); chainstay clearance was minimal.

Most current MTB frames assume the use of 1x and at least 168mm Q cranks. Some will accept less, but about the lowest Q current MTB cranks are M9100 XTR (162mm) and XX1 (168mm). Apart from Rotor (163mm) and a few low volume specialist European manufacturers just about everything else starts at 172mm and goes up from there. Boost cranks usually add 6mm to these numbers, and as the cranks get wider so do the chainstays, then the cranks get wider again and so on.

If the frame you're looking at 1) isn't a MTB frame, and 2) has a 68mm shell it's much more likely that low Q cranks will fit. There are pressfit equivalents too, but dealing with these is more complicated and creaking is more likely.

Later,
Stephen

[Toby Whitfield]

I think that waiting for the new run of Bombora's seems to make the most sense. I don't want to be tied into trying to force something to work that will be too much of a compromise, and the low q MTB cranks seem to be expensive, and not that low q. Even finding high quality square taper MTB cranks in my preferred 170 length looks challenging.

It also has the benefit of not requiring me to learn about modern MTB crank options. Figuring out disks and drop bars will be enough education for me.

Thanks for the advice.

Toby

[Daniel Jackson]

Toby - what size Bombora are you looking for? I’ve got an XL frame/fork for sale if that might work for you.

Best,
D.

[matthew shroyer]

I just saw this, but I gotta get to work, so i'll be quick and chime in later. I purchased a bombora L, specifically because i like the geo, needed (knee) low q, and wanted the biggest tires i could run with a low q crank (i got addicted to tubless on a fatbike, love large volume).  However, it took me a while to gather everything for the build, and the bombora frame got dented really badly on the top tube, compromising its integrity for safe riding in my opinion. this happened by one of my kids smashing an amplifier against the frame, right where the butting gets super thin, the fork is heavy, but the rest of that frame is pretty darn light, If you want durability i would go with something else. My solution was the midnight special, but that is a departure from the bomboras geo, with a more road oriented front end, unless you run an angled headset to copy the bombora. You could also go with the kona Rove st, which if i remember correctly is nearly identical to the bombora/evasion and can take a low q crank. 
I'll chime back in later with more when i have a moment.   I would sell my bombora frame with a dent for cheap if you want to have someone fix it or try to fix it, retube it, etc. 

matt

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[Thomas Lawn]

Matt, what a bummer to hear about your Bombora! I'd never thought to compare the bombora to the Rove ST, but you're right in that they are very similar. One important thing to note about the Roves is that fitting bigger than a 650x48 tire is pretty much a no-go. It might be possible to get a 650x50 with minimal mud clearance but the chainstays are super narrow on these bikes.

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[Toby Whitfield]

I've responded to Daniel and Matt privately, but just in case anyone is looking at this and happens to have one that they're looking to move along, I'm interested in buying a large sized Bambora - though not looking for a frame repair project.

Toby

[Justin Wyne]

May be interested in the dented Bombora if no one else has claimed it

On Monday, August 3, 2020 at 6:45:53 AM UTC-4, matthew s wrote:

I just saw this, but I gotta get to work, so i'll be quick and chime in later. I purchased a bombora L, specifically because i like the geo, needed (knee) low q, and wanted the biggest tires i could run with a low q crank (i got addicted to tubless on a fatbike, love large volume).  However, it took me a while to gather everything for the build, and the bombora frame got dented really badly on the top tube, compromising its integrity for safe riding in my opinion. this happened by one of my kids smashing an amplifier against the frame, right where the butting gets super thin, the fork is heavy, but the rest of that frame is pretty darn light, If you want durability i would go with something else. My solution was the midnight special, but that is a departure from the bomboras geo, with a more road oriented front end, unless you run an angled headset to copy the bombora. You could also go with the kona Rove st, which if i remember correctly is nearly identical to the bombora/evasion and can take a low q crank. 
I'll chime back in later with more when i have a moment.   I would sell my bombora frame with a dent for cheap if you want to have someone fix it or try to fix it, retube it, etc. 

matt

On Sun, Aug 2, 2020 at 12:58 PM Daniel Jackson <daniel.s...@gmail.com> wrote:

Toby - what size Bombora are you looking for? I’ve got an XL frame/fork for sale if that might work for you.

Best,
D.

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