# Motorman's fat Mundo thread



## motorman (May 30, 2011)

This will become a build thread, but for now some questions 

The idea behind this is to build a family wagon, going to the shops, local trails & trips to the beach. No massive weight, but building a versatile bike to transport 2 little ones primarily, but also double up as a camping bike for me:thumbsup:

So lets begin..... 

What is the largest tyre you can use on the standard wheel & still have 21 gears & no chain rub? Maxxis Hookworms 2.5?

I am planning a Nuvinci N360 with a Trialtech 47mm rim/3.8" Black floyd. Question is I'm pretty sure this will fit fine on the V4, but what about chainline :skep:

Also, regarding gearing, I was planning 32F/22R. Does this sound about right for medium hilly location with 2 kids on-board?

My money is on everything working with this combo, but any advice welcome


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## andyh2 (Mar 8, 2008)

MM I'm going to watch this with interest Just awaiting tyres and then I've got everything to build up my V4 frameset.

I can't answer to Hookworms, but I had a V1 when they first came out. With 60mm Big Apples I had chain rub with 8 speed rear which was solved with 7 speed cassette.

I've decided I'll be happy to coast downhill on the Yuba so will be going with inner / middle / bash. 22/32, maybe 22/36. It would be easy to get a bit of extra clearance by using a longer BB to put the rings in mid / outer position. With the extra long chainstays the crossover chain angles are much more forgiving.

I did consider using a cassette single speed hub and running 5 of 9 speed cogs to give a dishless rear wheel. I also fantasised about a "fat" set up, but I've already blown my budget and keeping the wheels standard means I'll be able to swap with my other 26" bike. It means I'll be able to have a set of wheels with studded winter tyres making for an easy changeover as required.

To my eye, the frame is a utilitarian masterpiece, the fork looks a bit 'normal' by comparison. Couple of days after receiving my frameset I came across a post where someone's fork had collapsed. They were using a 203mm front rotor (Yuba say 160mm max) and both Yuba and Surly note that the braking forces on a longtail can be significantly higher. After worrying about whether to get an alternative fork I've decided to set it up with V brakes to start with and might add a rear disc as a 3rd brake. I think PretendGentleman's Arai drum drag brake is probably a better way to go though. 

I really like the adaptability of Freeloaders so I've a set of those for it, they'll also act as wheel guards for little legs.

I weighed my frame (inc wide loaders), fork, headset and it came out at just under 25lbs. I reckon my standard steel frame, fork, headset and rack is around 10lbs. So a 15lb weight penalty seems pretty good for all that extra utility.

Good luck with the build.


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## PretendGentleman (May 24, 2011)

the 2.5 hookworms work great. they're big! full 8speed cassette with deore triple chainring leads to no chain rub. with a 68mm bb shell on the yuba, you can even space a modern 68/73 external bearing crankset further to the right to allow an even bigger tire.

If you go with the nuvinci, you can adjust chainline by playing with bb spacers and you can move a single ring between the middle ring position and the outer ring position...definitely plenty enough to get a good chainline (though with such a long chain a straight line is less important). with black floyds however, I cannot say from experience, but you can put your middle ring and cranks as far to the right as possible, further right than the rear cog, reducing the likelihood of rub--with a long chain the drawback of a bit of wacky chainline is minimal.

The stock fork doesn't have room for anything much bigger than the 2.5 hookworm. no chance the floyd will fit up there, but a non-offset pug fork isn't too hard to come by

if you haven't seen this post, check it out:
http://forums.mtbr.com/9312854-post117.html


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## motorman (May 30, 2011)

Thanks for the replies 

I'm working on a shopping list for this tonight....:thumbsup: Getting excited now, even my wife has bought into this idea:eekster:

I already have a spareset of Surly 135mm non offset forks & tyres, so the front end is already taken care of. 

I was thinking about running a fat front & regular rear wheel/hookworm to begin with to play around with gear ranges, as this would be a quicker build, but I have now decided to go full fall from the beginning. Do it first time & do it right 

trying to decide between alfine 8 & nuvinci....usual balance between weight/strength & cost. I am still confused by the question of ratios, but I was thinking of starting with 32t - 24t set up & take it from there. 

I also like the freeloader idea for keeping small feet out of the wheel, I was planning this too:thumbsup:


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## PretendGentleman (May 24, 2011)

motorman said:


> trying to decide between alfine 8 & nuvinci....usual balance between weight/strength & cost. I am still confused by the question of ratios, but I was thinking of starting with 32t - 24t set up & take it from there.


I'm not super familiar with IHGs, but I know that with the rohlhoff (and I assume this applies to some extent to any IHG) that they strongly recommend a minimum gear ratio (i.e., that you not use a chainring with under a certain number of teeth for a particular rear cog). If you try to make the bike have an easier gear, you run the risk of destroying the hub because you're applying too much tension to the chain and thus too much torque to the rear cog for the hub to last as long as it was designed.

I would be very careful to research this issue for any IHG you're considering so you don't end up buying something that doesn't have enough low-end for your needs.

Cassettes and freewheels can potentially be destroyed from too much torque, but they tend to be cheaper to replace than IHGs. Tandem cassettes typically/should have freehubs that are designed to bear these higher loads, but many tandem cassettes have a greater than 135mm outer locknut distance, requiring modifications to the hub or the frame (the latter is what I had to do for my Yuba).

I've heard some talk about 29er rear hubs, as some of the bigger stronger guys are having problems blowing out even rather nice conventional shimano freehubs as they apply more power to spin a wheel with a greater 2nd moment (rotational inertia).

Another issue is that you have to deal with the 14mm dropouts. if you go with a threaded axle hub, you can use an adapter without much concern. BMX adapters will require a bit of filing as bmx axles are typically 3/8" (9.5mm) and rear mtb axles are typically 10mm, but this is easy if you have a round file or rotar tool with the right bit.

If you go with a hub that has a qr axle and you can't replace it with a threaded axle, you will have to crank the qr down really hard to keep the wheel from sliding forward in the diagonal dropouts. I've gone this route with my yuba and since getting it about as tight as I can with bare hands, I've had no slipping. But, I have not yet carried a load that required the use of my granny gear. My biggest load was a 160lbs person and I never required anything easier than the 32f 36r gear combination. (btw, 9speed slx 36-12 cassette is great for a cargo bike--don't think you can get a rear cog as big with any fewer gears on the cassette, though my tandem's 7sp 34-13 is pretty darned good too)

My finacee loves my cargo bike! I've given her a few rides home from the bar when we've met up --her in car and me on bike. Also I've given her a ride when she's wearing a nice skirt and wants to ride side-saddle. Passersby usually have a big smile when they see us, maybe moreso than when they see us on the tandem.


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## andyh2 (Mar 8, 2008)

I'll second the helpfulness of low gears. I had 22 x 28 lowest on my Xtracycle and I'll be glad it's 22 x 34 on the Yuba. It is quite hilly round here and my 66lb daughter does like to have her 88lb cousin along.

PG very sensible to make sure 'biggest load' and '160lbs person' were in a separate paragraph to 'fiancee'


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## motorman (May 30, 2011)

Yes, it is the ratio issue that is causing me the most problems

I already have a fat bike for beach/sand riding & I went through the same isues with that.
I wanted IHG, but I couldn't the the gearing low enough to keep within the ratio range. I know of others that have used the alfine for example with 32-24, but that was a fat bike, not a load hauling

I was out today with my son on his tag along & me on my 1x9 mountain bike. Lowest gearing on that is 32-34. This was only just working on the steeper trails, so I am now thinking that I will need to go much lower for the heavier bike, another kid & shopping etc.

Looks like I will have to go with normal gearing, but this means that I will loose the full fat factor on the rear, due to the chainline issue.

If I build the rear wheel with 47mm rim & 2.5 Hookworm, is this the max size to allow full gears?

Another option was to use a 26x3" cruiser tyre & loose a few gears & space out the cassette.










Another problem i found last night, I could only find hub adaptors for Alfine & Nuvinci in the states...I'm in Scotland, so there is a few weeks hold on a build right there!

Looks like a few more nights of scratching my head, but I loves it :thumbsup:


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## PretendGentleman (May 24, 2011)

The 47mm wide rim might push the sidewalls of 2.5" hookworms out enough to lead to chain rub issues in the lowest gears. I've got around 5mm of clearance and I'm using Rhyno Lites (25mm or so?). Unless, of course, you run cranks that can be spaced further to the right. I think that with the speed and terrain that human passengers can comfortably handle does not necessitate modern fat bike components, especially not on your drive wheel, but to a greater extent on your front wheel for steering traction. 

If you want to run super wide rims, get cranks that allow you to adjust the spacing. This could be modern 68/73 outboard bearing 2 piece cranks or conventional square taper cranks that is designed to use a 115mm or less spindle, leaving room to experiment with different sizes to find out how wide you need to run your triple chainrings and be able to get to any gear you want.

If you've got a good back you could also put extra spacers on the non-drive side axle (requiring you shift the whole axle that direction) and spread the dropouts like I did to accommodate a 145mm o.l.d. tandem hub(sheldon brown has a rear triangle bending guide if you're less of a monkey and prefer tools), but for you it allows you to move the wheel to the right, then you can undish the wheel back towards the center (stronger wheel is a benefit here too) resulting in your hub being offset to the right and your rim centered.


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## Anthony King (Aug 29, 2010)

You can use the Alfine or Nexus hubs with a much, much lower ratio than Shimano says you can.

Some facts for your consideration: the dutch bakfiets made by Henry Work Cycles in the Netherlands weighs about 100pounds. The bakfiets made for US imports are spec'd with a red band Nexus 8spd. I have owned one of these and I believe the stock setup was a 32T chainring and 22T cog. I am certain the low gear was in the 20-22" range. Henry of Henry Work Cycles says this is not an issue. I know several bakfiets dealers and none report problems using the Nexus with these heavy bikes and low gearing. I have personally taken my 100lb bakfiet up steep hills in the lowest gear with 375 pounds of humanity on the bike (190 lb. driver and passengers weighing 120, 45, and 20). No problem.

I'm sure this voids the warranty. I would be reluctant to go outside of spec and void the warranty on a Rohloff, but not on an eight speed red band Nexus or Alfine.

On the derailleur side of things what's wrong with having (in an extreme case) five or six usable cogs? 34-30-26-21-17-13 w/ a double or triple would work for any terrain and large loads. Wide spacing between rear cogs, but surely we don't need our cadence to be dialed in at all times on a cargo bike?


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## motorman (May 30, 2011)

Andyh2 - I just realised who you are - I was looking to buy your xtracycle kit that was for sale on STW, but it sold before I could mail you!

Where did you get your frame - Practical cycles or Yuba Europe store?

Tonight's random thought is fit one of these 200mm BBs & see how crazy the chainline looks & what gears are available with the stock wheels & 3.8 tyres










Sounds crazy, but for $24 it is worth a go 

In the meantime, here is some inspiration :thumbsup:


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## andyh2 (Mar 8, 2008)

MM I got mine from Practical Cycles. I like dealing with Zaynan, always found him helpful. The delivery charge to Crieff, Perthshire was the standard £19. The frameset price includes headset, but not seat tube.

I found the Xtracycle great with up to 50kg (daughter and shopping), but adding on her cousin (another 40kg) gave way more flex that I wanted. Also the BB was pretty high which made stopping and starting more nervy than I liked. On the plus side it felt nimble enough for me to be happy riding it for commuting.


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## motorman (May 30, 2011)

Because I'm that wee bit further north, I was going to be £110 for postage from practical for the frameset. 
Needless to say, I am ordering direct from Yuba Europe Store...Complete bike is £200 cheaper & only £70 for postage as an example.


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## PretendGentleman (May 24, 2011)

andyh2 said:


> The frameset price includes headset, but not seat tube.
> 
> I found the Xtracycle great with up to 50kg (daughter and shopping), but adding on her cousin (another 40kg) gave way more flex that I wanted. Also the BB was pretty high which made stopping and starting more nervy than I liked. On the plus side it felt nimble enough for me to be happy riding it for commuting.


the seatpost is an unusual size, motorman, so be aware that you'll have to order one and you won't have many choices. Not sure why they used 31.8 when 31.6 is extremely common. I can only suspect its because 31.8 allows you to clamp a stem to your seatpost.

The Yuba is great for heavy loads, but its true that a high bb makes things a bit funny, especially getting upto 5mph from a start. running fat tires will make this more pronounced and low pressures will make low speed steering a bit harder too I suspect.

I gave 2 guys a ride home from a party on Sunday night. Easily 330lbs of drunk cargo. I was able to keep up with my lady on her own bike and I didn't feel any substantial flex in the frame. It was a hilarious experience! 2.5" hookworms worked great.


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## motorman (May 30, 2011)

Thanks for everyones help so far :thumbsup:

Ok, bike is ordered along with a load of parts that have started to arrive 

I have decided to get the bike rolling with a standard rear end for a few weeks until I sort out the issues with drivetrain & chainline.
Those of you that have fitted Fat Franks to your bike, will know how chubby these tyre are - measure about 58mm on 30mm rims.
I put a Black Floyd on my front 42mm rim tonight for a visual reference between a fat tyre & a really fat tyre  84mm wide

Frank, meet Floyd 



















:eekster:


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## motorman (May 30, 2011)

Progress so far....

I will probably wait until the spring till I go full fat on this now, as -

A. Quite like the stock gearing & there is no point in throwing it away until it is worn out. Also gives me time to figure out what ratios work for me.

B. As winter is nearly here, I'm keen to run full length fenders on the rear























































This bike is mucho fun Big, lazy ass family cruiser, what's not to like:thumbsup:


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## motorman (May 30, 2011)

Fat rear end nearing completion 




























Yep, is does also work with the stock brakes too :thumbsup:



















Note the wheel spaced over to the non drive side. Not much room in there  The freehub was spaced out buy the same amount to the drive side.










BB spacer










Nice neat chainline. I only loose the 1st & second gear, clearance for all the others.










Nearly there, but the red wheel is not working for me, so that will be painted very soon.

More info & pics coming soon :thumbsup:


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## tractopelle (Jul 20, 2012)

So, it's a Fat Franck at the rear?
What hub and spokes did you use?
Thanks.


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## andyh2 (Mar 8, 2008)

It was a Fat Frank at the back initially but MM has now got Surly Black Floyds front and rear. Pretty impressive for a standard frame to be able to take it.

I'm just building one up, but with standard wheels and 55mm tyres. Looking at this I'm envious  Might have to do this one day it makes a lot of sense to have the extra volume tyres on a cargo bike.


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## motorman (May 30, 2011)

As Andy says, it is a Surly Black Floyd 3.8" mounted on the standard Yuba 48H rear wheel.

This is as big a combo you can run on the rear with standard wheel/cassette. Tyre measures about 84mm wide. After some experimenting, fitting a fat rear end to this bike is actually very simple. I will do a detailed post soon with all the steps required to get this to work.

Ok, here is the final build of the bike. Floyd on the front changed to a Larry, because it steers much nicer & looks better. I gave the standard bars a go, but changed them out for a set of Salsa flats, bike feels just "right" now. really stable & reassuring ride & I am looking to getting out on this for a proper ride later in the week.










Family bus mode




























1 + 1 mode










Dad's touring / camping mode!










Naked industrial awesomeness !










Home made decks










Proof that " you can" with nothing more than 4 washers & a large tyre :thumbsup:


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## tractopelle (Jul 20, 2012)

Nice job! :thumbsup:


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## Lone Desert Walker (Sep 15, 2011)

*Yes!!!!!!!!!!!!!!!*

Rock on brother!!!!!!! Going to get me a flizzoyd!!!!:thumbsup::thumbsup::thumbsup:


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## Saw (Mar 24, 2012)

Outstanding! :thumbsup:


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## motorman (May 30, 2011)

I have decided to switch from 3.8" rubber on the back & to 3"










70mm, so, ok, this is now a half fat, but now I have all gears again *;D



















Trying out the pogies & front rack added










Pretty much sorted for bikepacking duties *;D


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## longhaultrucker (Jan 24, 2007)

Brother,I'm sure loving this,watching with great interest :thumbsup:


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## motorman (May 30, 2011)

Kids on holiday...no problem!



















:thumbsup:


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## véloneige (Nov 26, 2012)

Motorman and All:

Great project! Inspiring!

In my small, isolated community in the far North West of Canada, Whitehorse, there is a Yuba Mundo sitting unsold in one of our only 2 bike shops, so I have forwarded this link to my bike mechanic. I could also, in theory, get a Yuba Boda Boda brought in too, so similar half-fat issues there...

As I hem and haw about going with the full fat tired Surly Pugsley with racks and fenders + Rohloff, studded tires, to replace my 1993 Sachs Torpedo-7 IGH winter-commuter-cargo bike, I wonder if a full fat front 3.5 and sort-of-fat 3'' rear tire on a Mundo is noticeably better on 15cm 6in of new snow, or 15cm of brown sugar slush than the 26x1.9 studden Nokians I run, or rather push, in such conditions now?

We have no snow-clearing here, and with climate change, we now have a month a year where the snow is no longer packed and is wet or slushy and soft....

So, for Motorman or others, any experience riding in 15cm new snow or slush with a half-fat bike?

Again, great inspiration! Great bike!


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## motorman (May 30, 2011)

I cannot comment on snow riding as we haven't had any this year :madman:

If i'm honest, I doubt the mundo would be good for you - it is a very heavy bike, even unloaded.

It rides really well, but if you encounter situations where you need to push it through snow I think things could become difficult. & tiresome.

It is also difficult to keep rear wheel traction on the mundo when climbing slippery surfaces unloaded.

It is a great bike, but not perfect for your situation.

I too have a fatbike & if i were you, I would go the pugsley route, with racks front & rear.


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## PretendGentleman (May 24, 2011)

véloneige said:


> Motorman and All:
> 
> Great project! Inspiring!
> 
> ...


Your weight is more evenly distributed between your wheels with a longtail, so there would be flotation benefits there I imagine. But yes, yuba is heavy. You can spend a bit more on a big dummy and definitely save some weight.


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## beoutside (May 5, 2007)

*3.8 surly knards on yuba..... looking at some frame mods*



PretendGentleman said:


> Your weight is more evenly distributed between your wheels with a longtail, so there would be flotation benefits there I imagine. But yes, yuba is heavy. You can spend a bit more on a big dummy and definitely save some weight.


Since I have an electric rear hub on free wheel I have not figured out how to set it up so I can have on my gears but it rides great so I am going to mod it so it will...... 4000.00 miles on her so far prefat tires now going fat and turning her into the elk getting machine!


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