BB length for Atlantis with White VBC cranks?

[Mark Reimer]

Hi all,

I just got a pair of White Industries mountain VBC cranks with a 46/36 ring combination for my Atlantis build. There is a 113mm BB in the frame currently and it is way too short to run these cranks, which isn't that surprising. I followed the instructions on the WI website and it looks like I'll need a BB somewhere in the 130mm range, which seems very long to me.

Is anyone out there running the VBC cranks on an Atlantis? Care to share the inner ring size and BB length for comparison please?

Thanks!

Mark

[blakcloud]

Mark,

On a non Rivendell bike that I had those cranks on I used a 122.5 BB. I could have went a little shorter had the chainstays been dimpled for crankrings. It was that inner bolt on the 36 chainring that caused much of the problem as the head sticks out past the chainring. I came up with 122.5 by eying the crank on the BB spindle that I had, placed it where I needed it, measured the distance, doubled it, added this number to the my current BB and came up with 121. Shimano had a 122.5 which was only .75mm off from my best guess so I used it. Hope it works out for you.

Thomas
 

[Shoji Takahashi]

Wow, really? Erik of Bikenoir/Cosmic Country mentioned 113mm BB on the Hunqapillar. I have a VBC Mountain and 113mm waiting for installation in the box... maybe I'll need to plan on a longer time window before venturing.

Here's the link to the thread on 113/VBC/Hunqapillar: https://groups.google.com/forum/?fromgroups#!starred/rbw-owners-bunch/jE_W_ff3RSU 

Good luck, Mark. 

shoji

[erik jensen]

I'm rolling a 40x24, for climbing infinity and maximum clearance. I'm within a few mm of rubbing 60s. Not sure if I have a 113 or 118 down there, been a year or so since I replaced it.

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[Mark Reimer]

Well it's still a mystery. I used some callipers to measure the BB in my frame, it's 114 from end-to-end and my rings bottom out on the frame before the BB taper even starts to make full contact. Using the instructions on the white industries website, they'd have me running a spindle over 140, which cannot be right. I've emailed them as well as Mark at Riv for advice. My local shop doesn't have square taper BB's past 125, which I would have thought would be adequate. 

There are enough photos of Atlantis' with VBC cranks to make me know this is a doable combination, but many of them seem to have smaller inner rings - usually around 30 or smaller. I'm wondering if the size of my inner ring is too large with the Atlantis flared chain stays. I hope to have this sorted out soon, the remaining parts for the bike are arriving this week and this is all that will hold me back.

[Mark Reimer]

Since this has been a topic on my mind, I just noticed that the hunqapillar on the Radavist has the White Industries road VBC cranks, which have a very narrow Q factor, plus 46/36 rings, which should be even harder to fit than my situation. Confounding!

http://theradavist.com/2014/05/allans-hunqapillar-dirt-tourer/#8

So far emailing back and forth with W.I. and Riv hasn't turned up a solution. Confusion continues. 

[Shoji Takahashi]

Hi Mark,

Did you try Keven or Brian at Riv? They both run VBC cranks.

Brian's Hunqapillar http://www.rivbike.com/product-p/staff10.htm
Keven's Appaloosa http://www.rivbike.com/product-p/staff3.htm

Good eye on the Radavist-- it seems like Jared (at Riv) may have insight into the BB length.

Keep me/us posted!

Shoji

[Mark Reimer]

Great call, Just sent Brian an email about it. He's also running the road VBC cranks like the Hunq on the Radavist. Very curious how that works.

Last night I bought a super cheap 127.5mm BB just to try it out. Turns out it does work, despite the White Ind calculations pointing me to a much longer spindle length. I have about 3-4mm clearance at the chainring bolts, which would be the first thing to contact the frame. That suggests I could get away with a shorter spindle, maybe a 125, which still seems very long to me, but so it goes. I'll update when it's finally resolved!

[erik jensen]

This is being over complicated. You are trying to equip a road double, with way too high of an inner ring, on a bike with 60mm tire clearances. You will need a crazy wide bb to do so. 125 isn't very long, old mountain bikes with high profile cranks used them (early 80s mb-1s among them).

The solution to bottom bracket issues is to, a) search for an answer b) try out combinations. A bike shop, in which you pay for hourly rates of labor, will have a variety of these bb lengths to try in order to find the correct length for the application. If you are doing your own work, in order to save money, don't expect that the answer will be there or that paid craftspeople will be able to help you without you taking your bike into a shop and allowing them to swap combinations (and hopefully, paying for that work). This is part of the craft of the mechanic work you elected to avoid by doing it yourself. DIY is often more expensive, when starting out.

In architecture, we charge to answer requests for information from the contractor, because it takes a lot of time (imagine answering the phone on the thousands of custom setups that go out the door of shops like riv, that's a lot of hours). I wonder what an RFI system would mean for shops, but I digress.

So, since your custom build means a) didn't work, you've finally arrived at b) which was the place to probably start in the first place as all hand made frames are slightly different. You will likely find that 36x48 works ok with a 125mm bb, but that your chainline is pretty bad. This is why wide range doubles, not road doubles, are what riv recommends and what the bikes are designed around. Instead of returning those bottom brackets, keep them for the next time you or your friends need to try out combinations. Super cheap bb's make the world go round, and are used on all of my bicycles, since this is a constant question for people who tweak their setups. Next time, if you don't know, just go with a crank that is recommended or prepare yourself for similar headaches.

Not trying to run on about this, but at a certain point the answers are only to be found in practice. Custom parts on custom builds = custom headaches.

Put on the 127.5 and ride your bike, it's working and you're on your way. When you wear out those rings, drop down your sizing and put on a smaller bb, or get a low profile triple if the 46 is important, or get a 30 if the 46 is important, or or or ad infinitum.

e

[Mark Reimer]

The ENO crank is not a road double actually, it is a mountain double crank. VBC cranks are offered in two variations - road and mountain. ENO cranks are the single speed and mountain double arms. The cranks I have are designed with wide chain stays in mind, so this should work. I always knew the Atlantis had wide stays, but after seeing a few photos of this combination online, I wasn't expecting any troubles.

The only reason this is getting complicated is because the instructions provided by White Industries themselves generated a BB length that simply made no sense - well over 140mm.

So in some ways, I agree - my first step was to use the manufacturer-provided guidelines for calculating bottom brackets. This generated questionable results, so that lead me to option two: ask the owners group if anyone is running the same combination and can share their BB length. Since that didn't turn anything up either, I asked the manufacturer if I was using their formula correctly. And then, like you suggested, I'm on to option 3 - go to a shop, and trial and error. 

I am well aware that bike shops charge for labour by the hour and it's a valuable service. I spend a significant amount of my money employing my local shops for this exact service, so there is no need to preach the value of paying skilled craftspeople to me. I am part of the choir. The reason why this thread has rambled on is that there never should have been a need to employ any skilled mechanic, much less go into a trail and error mode and waste money buying a bunch of cheap bottom brackets as a means of finding the right length, because calculating BB length is easy with some simple math. I've done it for all my bikes for over a decade. I pay my bike shop to do things I can't do, and order components locally whenever possible. I'm building the Atlantis myself because I enjoy it, not simply to save money or because I don't value skilled work. 

I manage a graphic design studio and have the exact same understanding of the value of time as you do in architecture. That's why I came to an owner/enthusiast group first, which doesn't cost anyone anything, then contacted the manufacturer of the crank second (simply asking if I was using their published guidelines for calculations correctly) and only contacted Riv for advice after even my own local shop mechanics (who I pay) were scratching their heads. 

Anyway, you may be glad to know I now have a pile of unused bottom brackets as well as a number of other components for the build purchased from my local shop (shop wins), some new, smaller white industries rings and BB on the way that will enable a much narrower BB (White Ind wins), already had ordered a number of the components for the Atlantis from Rivendell directly (Riv wins), and will soon be spending my time riding blissfully into the sunset instead of justifying my query here (we both win!)

Problem solved, now lets go ride some bikes. 

[Mark Reimer]

Realized after posting that you likely were referring to the 46/36 chain ring sizes as being a road double, not the actual crank arms. My mistake. Ride your bike!

[rperks]

Mark,

I am correct in thinking that you picked up these cranks used?  and if you have a 113 bb spindle, new or in good shape, can you put the arms on said spindle out of the bike, so that the arms are across from each other, and torque down to spec of 30 ft lbs?  From there it should be easy to measure the Q factor with a tape measure or ruler.  I am wondering if the arms had previously been off and on, or run loose and the tapers are slightly buggered.  This could cause them to run up on the spindle tapers and give you a false impression of fit with a specified spindle.  This still puts you back at a point of trial and error to get them working.

My only concern is if you are needing a bb spindle that long it means you quite possible are having 14.5 mm of creep split up in some portion of each arm.  I am guessing these have the self extracting bolts, and yo may not be seeing how close these are to having the bolt bottom out on the spindle end.  You may get these to work on a longer spindle, but is the tapers are that far out of spec you may honestly want to start thinking about safety of use.  

That all said, even with the math WI recommends, a 36 inner ring is pretty big and may be a portion of the multi faceted problem.  First thing I would do is confirm Q on a known accurate spindle, and make sure you are remotely within tolerance.  From there if you want to use the cranks you will also have a new baseline for you calculations on where it all sits in space.

Another thing to consider is the differences between spindles.  I have installed the VBC on WI, SKF, Shimano and IRD 113 bottom brackets.  They are all close, but there is still a bit over a mm in spread of where the chain line ends up.  That said, once the chain is on and you are rolling it is all about the same.

Rob

(the only thing worse than professional liability for answering questions, is answering questions about used parts and stuff you talk about on the internet ;-) )

Ventura, Ca

[Shoji Takahashi]

Mark,

I installed the White ENO/VBC Mountain on my Hunqapillar. It's a 44/26 on a 113 Shimano BB. There's not much room for a larger inner ring (or outer ring for that matter). Here's a pic of the inner ring.

https://www.flickr.com/photos/stakx/14266122862/

The distance to the chain stay is closer than the Sugino it replaced. No problems (thus far) with rubbing, but I'm 155#.

Good luck,

shoji

[Mark Reimer]

Oh thanks Shoji!! That's awesome that it fit on a 113. Thanks for sharing. Once my rings come in, I'll share a photo of the ring/bb combination here as well for future reference. 

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[Mark Reimer]

Rob,

thanks for the tips. Sorry to have delayed my reply. You are correct, these cranks are new. I had also wondered about the condition of the crank arms, but thankfully they seem to be in great shape. I can torque the arms down to 30 ft lbs and based on my eyeball measurements, I'd say I have 3-4 mm between the end of the spindle and the end of the crank arms. So the crank bolts aren't bottoming out or anything. (I used some 'normal' crank bolts, not the self extracting, so i just unscrewed them and could see how far the cranks had been pushed onto the spindle).

I'd say that at this point, I can definitively say that my problem is simply that the chain stays on the Atlantis do not accomodate chain rings as large as 46/36 without having at least a 122-124mm bottom bracket. 

Currently I have a 127.5 and there is about 3-4mm between the chain stay and chainring bolts. If I double that and subtract it from the spindle length, it suggests a  121.5mm spindle would cause the bolts to just touch the frame. 

I've ordered new rings for the cranks - 44/30. That will allow for a much narrower spindle since the chain ring and bolts will have a smaller radius. A 121 would easily work. Mark from Riv used a 118mm bb with 44/30 rings and the road VBC crank arms on his Hunqapillar and while it technically worked, he said the crank arms were a bit too close to the frame for comfort. They currently reside on his Homer with a 113mm bb. Using the ENO arms, I will have more clearance and anticipate a 118mm will be fine on the Atlantis.