BB and rear spacing for plus size frame?

[joth jacobson]

I'm planning out the next build in my mind, which is currently a steel hardtail that could run either 29" or 27.5+ wheel/tires. I'd like to use the bike for overnights, and plus size option for loading it up is appealing. In planning for 27.5+ option in back, would like some input on best approach to spacing.

Options I've been considering:

1. Standard 73mm BB and 142x12 dropouts - would seem to limit plus size tire options without compromising chainring clearance

2. Boost set up - 73mm BB and 148x12 - allows for standard BB size and (hopefully) emerging standard hub size. does this allow for 3.0 or greater tires?

3. 83mm BB and 157x12 dropout spacing - would allow for widest tires, but non-standard bb and hub sizes.

What have others used for plus size spacing, or what would you use if building such a frame today?

Thanks,
Joth Jacobson
Otis Cycles
Flagstaff, AZ

[fortyfour]

<SNIP>

3. 83mm BB and 157x12 dropout spacing - would allow for widest tires, but non-standard bb and hub sizes.

83mm BB Shell width IS a standard. For example, Race Face's SIXC Cinch crank and their new Atlas Cinch both come in 83mm options with appropriate spindle lengths. There are other options too FYI.

12 x 150/157mm rear spacing also IS a standard. Many hub manufacturers offer this spacing in both 150mm QR or 157mm TA.

Both of the above are not a "non-standard". Both are well supported.

Your best option for plus sized spacing is most likely 73mm x 148mm (Boost) or 83 x 150mm QR or 157mm TA. You can't go wrong with either of those options to supply ample clearance for 3" tires and you have plenty of crank/hub combinations to choose from in either.

[joth jacobson]

Thanks Kristofer. Poor choice of words on my part. I understand that 83mm bottom brackets and 150mm are "standard" sizes. Just not as common when looking at parts. And not sure what the new Boost sizing may do to this size offering moving forward. Altho Race Face's new Cinch system helps in that one can simply change out spindles.

I remember seeing on your blog that you've built a plus compatible frame, to two. Do you go Boost or DH spacing?

Thanks for the feedback.

[fortyfour]

Thanks Kristofer. Poor choice of words on my part. I understand that 83mm bottom brackets and 150mm are "standard" sizes. Just not as common when looking at parts.

That's what my hunch was, but just wanted to make sure given how it was worded things were clear.

And not sure what the new Boost sizing may do to this size offering moving forward. Altho Race Face's new Cinch system helps in that one can simply change out spindles.

I remember seeing on your blog that you've built a plus compatible frame, to two. Do you go Boost or DH spacing?

Thanks for the feedback.

Honestly, I don't know what Boost will do to 150/157mm. To get the most versatility and room, I bend towards 83mm x 150mm QR or 157mm TA. The limiting factor is the space between chainring, chain stay and tire. The Cinch rings allow you to flip them to gain even more clearances, but again, the distance between chainring, chain stay and tire is where the trouble starts when you start packing all this in there and have a relatively short rear triangle. It depends on what kind of handling you're after too so there is that to consider.

Hopefully Sean at Vertigo may chime in? I know he's built a bunch of these rigs with the 83x157mm TA set up.

[jon_norstog]

I'm going with 83mm/150mm on one that I'm building now, a plus-size 29er and an update to my 26" "New Model" hucking bike coming up. I'll probably move over to 157x12 for the rear dropouts once the kinks are out and I've used up the rest of my 150mm stuff. One thing to be aware of is that a lot of boingers (suspension forks) are a little tight on a plus-size tire, and the ones that are specifically for plus-size all have tapered steering tubes.

I think the 83mm BB shell is going to be with us for a while, at least in its English threaded configuration. Once the dust settles I think most 'builders will find they need the extra BB shell width so they can make space to bring that plus size tire in close, and that the 150/157 mm rear spacing gives up a pretty decent chainline with that width shell.

Good luck there

jn

"Thursday"

[Rody]

To what advantage is the wide spacing on the rear end for a 27.5+ / 29er build?

I've done a number of these and had no issue running a 3.0" tire on a 73mm bb and 135mm spacing.

rody

[dgaddis]

To what advantage is the wide spacing on the rear end for a 27.5+ / 29er build?

I've done a number of these and had no issue running a 3.0" tire on a 73mm bb and 135mm spacing.

rody

Makes the wheels stiffer.

Also, isn't the point of Boost (vs the 150/157) that it allows for a standard Q factor?

[Rody]

Makes the wheels stiffer.

Seriously? Is 15 more millimeters of axle width going to make a difference in "stiffness" when you are floating a high volume, low pressure tire. The tire is going to provide more wiggly movement than the wheel ever will in the proposed scenario.

Please forgive my grumpiness...I understand our industry re-inventing it's self every season or two to create more market demand for the latest and greatest, but please, lets make forward progress that has defined benefits rather than just moving laterally to develop more financial flow.

rody

[afwalker]

I'm building an 83/150 bike for a 29r+ 3" tire bike. Wouldn't think you'd need that much clearance for a regular 29r/27.5"+ 3" tire. For that the 73/135 and some bending/dimpling will be just fine. So for the OP, what are your bending options available to you? I have 7 benders for my bending needs, lots of trial and error to dial it in. I will fill with sand or even an imported English wax that is less toxic than cerrabend, resin ws8 Shop Resin WS8
Bending is black magic, make the tubes what you need them to be:)
andy walker
https://www.facebook.com/walkerbicycle?fref=ts
https://www.flickr.com/photos/afwalker50/
Walker Bicycle Company | | Walker Bicycle Company
Fat Bike Trials | Walker Bicycle Company

[adarn]

To what advantage is the wide spacing on the rear end for a 27.5+ / 29er build?

I've done a number of these and had no issue running a 3.0" tire on a 73mm bb and 135mm spacing.

rody

My argument is more room for shorter chainstays, which are a good thing especially for a trail bike with plus size tires IMO.

[Rody]

My argument is more room for shorter chainstays, which are a good thing especially for a trail bike with plus size tires IMO.

Ok Adam, then please make your argument...

what is the chainstay length you are trying to achieve? What are the limiting factors that make this not possible with a 73mm bb and 135 spacing?

[dgaddis]

Seriously? Is 15 more millimeters of axle width going to make a difference in "stiffness" when you are floating a high volume, low pressure tire. The tire is going to provide more wiggly movement than the wheel ever will in the proposed scenario.

Please forgive my grumpiness...I understand our industry re-inventing it's self every season or two to create more market demand for the latest and greatest, but please, lets make forward progress that has defined benefits rather than just moving laterally to develop more financial flow.

rody

It's not the axle width, it's the wider hub flange spacing. The Boost hubs actually moved the brake and freehub body out wider, unlike 142 which is really just a 135 with longer endcaps on the hub. The claim is 15-20% more lateral stiffness, supposedly making a 29er wheel as stiff as a 650B. I hope to eventually actually measure that for myself, but it's a ways off at the moment. Whether that's needed is of course totally up to debate, but I know I like my wheels as stiff as possible, even with a high volume low pressure tire.

Boost also isn't just about the wheel/hub/axle, there are Boost specific cranks as well, and they move the spider out (to maintain chainline since the cassette has moved), but keep the same Q-factor as standard cranks. This gives you a little more room in the BB junction to work whatever magic is required to tuck that rear wheel in tighter without as much manipulation of the tubing.

There's really no downside to Boost that I know of. Is it needed? Nah. But neither is suspension, droppers, clipless pedals, hydro discs, etc. Time marches on and all that.

[fortyfour]

To what advantage is the wide spacing on the rear end for a 27.5+ / 29er build?

I've done a number of these and had no issue running a 3.0" tire on a 73mm bb and 135mm spacing.

rody

I suppose the bigger question is this: What is your issue with the 83mm bottom bracket standard as well as the 150/157mm axle spacing standard? (At least my impression is that there is some bristling at the idea.) Pretty much every mountain bike I make goes out the door with 12x142 rear's, 73mm bb shell widths, 44mm HT, and a tapered suspension fork. 73x135 certainly has it's place and I don't see it going anywhere for a long time.

For perspective: Most 29er's I build with clearance for a 2.4" rear tire is 16 to 16.5" / 406 to 419mm chain stay length. The majority being in the 16.5"/419mm range. Things are pretty packed in there with a 2.4" tire with clearances between the tire, chain stay and chainring. But things are getting even more packed in there with the trend for wider rims which creates a "fuller" tire. Chain line is still good, and I'm building the majority of the builds with 1x setups.

For a 27.5+, I'm looking to run somewhere in the 16" / 406mm range. My own opinion is that 83x150 gives someone like myself some additional options when the client request is short chain stays. Actually that's never a request, that's just how I build them... But the advantage being a little more width in the bottom bracket / chain stay / chain ring area to get a little more clearance for tires, which only seem to be getting bigger and fuller and rims only seem to be getting wider. Those are the advantages to me by having the option of 83mm bb width and 150/157mm rear axle widths.

29+? I won't elaborate as it's not in question.

But I'll take it one step further: This is how I see the standards falling in relation to tire size in mountain bikes, plus and fat:

27.5" / 29": 73 x 135/142mm

27.5/29 Plus: 83 x 150/157mm

4" FAT: 100 x 170/177mm

5" FAT: 100 x 190/197mm or 120 x 190/197mm

Agree with it. Disagree with it. But that's my ATMO.

[dgaddis]

What's your take on Boost Kris?

The modified chainring position gives you a little more room, but you're still working with a 73mm BB, but, Q-factor doesn't change.

[Rody]

I suppose the bigger question is this: What is your issue with the 83mm bottom bracket standard as well as the 150/157mm axle spacing standard? .

Kris,

My "issue" lies with the industries need to change standards for the sake of change, to create the appearance of forward progression in an effort to stimulate new sales, all while very little tangible positive benefits are achieved. Often, I feel as professional builders we are taken for a ride, mandated to conform to the latest marketing whim. Instead, calculated logical progress should be achieved by our group, moving design and function forward at a measured pace that benefits the performance of the vehicles we create to the enjoyment and safety of our customer base.

The issue is clearly illustrated by the OP's original query, customers and fledgling builders alike are having difficulty determining the positive attributes of the myriad options available. When the "standards" cannot be clearly defined as to their intended purpose and tangible benefit, it is an indicator that perhaps it does not have the staying power to last and should be questioned in it's relevancy.

The bottom line for the OP and my perspective is this...for a 29er/27+ hardtail build, you do not need to stray from a 73/135 design to achieve his defined goals. The issue is that it takes a capable fabricator to manipulate the tubing to achieve this efficiently within the space provided by the design.

What is fucking ridiculous is the fact that I have a drawer full of dummy axles, growing larger each time the wind blows in another direction.

It is our responsibility as professionals to lead.

rody

Ps...just to clearly communicate, there is nothing personal here. As long as a builder has found a place of comfort in design and fabrication that satisfies their customer base, their job is done.

[fortyfour]

What's your take on Boost Kris?

The modified chainring position gives you a little more room, but you're still working with a 73mm BB, but, Q-factor doesn't change.

Now that manufacturers have been making cranks that actually are meant for Boost, it appears to be more appealing. Personally, I'm still looking at how it all shakes out and what sticks/does not stick? 73x135/142mm setups still for most of my mountain bikes are sufficient. Those are in the majority of what I build. Plus and Fat are in the minority of what I make and that is where 83 x 150/157 or 100 x 190/197 still make sense and have had staying power. They don't seem to be going anywhere.

But with the right cranks and a Boost rear, a little more chainring clearance and tire clearance is not a bad thing especially as I mentioned earlier rims seem to be getting wider and tires seem to be getting bigger/fuller.

[fortyfour]

<SNIP>

My "issue" lies with the industries need to change standards for the sake of change, to create the appearance of forward progression in an effort to stimulate new sales, all while very little tangible positive benefits are achieved. Often, I feel as professional builders we are taken for a ride, mandated to conform to the latest marketing whim. Instead, calculated logical progress should be achieved by our group, moving design and function forward at a measured pace that benefits the performance of the vehicles we create to the enjoyment and safety of our customer base.

I think there is some things that are change for change sake, but there are indeed other changes that actually make sense. And of the changes that do make sense to me, may seem foreign / unnecessary to others. However, one thing I will say though is that none of this stuff is forced on anyone. It is indeed the builders job to evaluate what is available, what makes sense, what does not and what actually solves problems that they are facing that the client is in need of. The builder needs to keep up with this stuff though. You can not sit back and be complacent.

And going back to one of my original quotes, the limiting factor for me is the space between chainring, chain stay and tire. But it depends on what kind of handling you're after, which paints the picture for geometry / measurements and that sets the stage for what standards to choose from. That's a juggling act, but it is good to know that I have several bottom bracket and rear axle spacing to choose from depending on what the client "wants" and what I decide they "need". (That last part being the most important...)

Ps...just to clearly communicate, there is nothing personal here.

Nothing was taken personally. Just wanted to push you a bit to clarify. I still love you. Beers on me next time we see each other.

[joth jacobson]

Rody - I'd be curious as to how you make plus size wheels work with typical 73mm bb and 135/142 hubs? My building buddy made a frame with chainstay clearance for 3.0" tires, but has chain clearance issues (chain hits tire) unless he runs the single chainring in the outer (big ring) position on the cranks. Which would seem to throw off chain line. And basically results in a Boost-spaced front, right?

I agree that all the different sizes and standards get frustrating - especially to us "hobby builders" who also don't want a box full of dummy axles. If a norm is changing (like from QR to TA hubs), I'm fine with cost for new tooling. But I try to avoid chasing outliers. That's where feedback from you all on what's real and what's not is helpful. Thanks.

[fortyfour]

My building buddy made a frame with chainstay clearance for 3.0" tires, but has chain clearance issues (chain hits tire) unless he runs the single chainring in the outer (big ring) position on the cranks. Which would seem to throw off chain line. And basically results in a Boost-spaced front, right?

With Boost, as I understand it, you need to actually shift the front chainring placement. Wolftooth does a good job of explaining Boost, chain line and changes needed with crank/chainrings - see here as a reference.

I agree that all the different sizes and standards get frustrating - especially to us "hobby builders" who also don't want a box full of dummy axles. If a norm is changing (like from QR to TA hubs), I'm fine with cost for new tooling. But I try to avoid chasing outliers. That's where feedback from you all on what's real and what's not is helpful. Thanks.

First: My assumption is that you are using Anvil dummy's in combination with Anvil's Post Mount or ISO mount tools.

Second: IF I were a hobby builder and building myself mountain bikes, I'd look to have these options in my tool chest:

· 135mm keyed dummy (You can use this on road disc QR or mountain 135mm QR)
· 12x142mm keyed dummy (THIS will make things really easy to align the dropouts and keep things in phase.)
· 12x142mm standard dummy (to use with either a Post Mount or ISO disc jig.)

If also wanting to build in Plus sized bikes, I'd do research on 150/157mm and look into the 148mm Boost option as well but decide then based on information of which one you think suits your wants, what solves your needs and finally if it fits in to your budget. Either of those options you will need a keyed and non-keyed axle option if you are using Anvil's disc brake tools. So which ever you decide on, you'll need 2 axles.

But I don't think 135mm or 12x142mm is going anywhere any time soon.

[Rody]

it is good to know that I have several bottom bracket and rear axle spacing to choose from depending on what the client "wants" and what I decide they "need". (That last part being the most important...)

YES, spot on.






Joth,

The issue with chain rub comes down to holistically designing the bike, recognizing that each dimension contributes to the whole.

An error many early builders make is to design wholly around a single element, such as short chain stays or an appealing aesthetic. Folks who chase a single dimension often sacrifice the performance of the entire bike and unintended compromises occur.

If you are striving for super short stays with a full cassette out back, the probability of having component interference issues increases. A hard, critical eye must ferret out these interactions before ever cutting a single tube. Proper forethought and modeling save the strife later down the road.

Given your desire of a bicycle that will facilitate loaded touring and overnights, considerations such as proper weight distribution between the axles, heel clearance, and ample room for racks/fenders/etc should be priorities in the design equation. Component choices and their subsequent placement then are factored in.

It is unlikely that once you thoughtfully analyze and solidify your design for this purpose, that you will encounter chain interference issues running with a 73/135 specification, less so if you choose to avail yourself of the other spacing options.

cheers,

rody