Yuba mundo frame flex?

[scphantm]

ive got a new (v4) yuba mundo that i am running a crystalyte HT on. everything runs great except for one thing thats borderline annoying/unsafe. it seems like i have a LOT of frame flex in this thing. i currently don't have a means to immobilize the frame to put a pry bar on it to see if my twisting is coming from the wheels or the frame, but wherever its coming from, there is a lot of it.

is this a known issue with these things?

 

[ohzee]

How do you notice this flex ? Just when riding at high speeds ?

I have a new yuba and push it upwards of 35mph.. the only thing I have noticed is if I take my hands off the wheel I have a slight shudder , but
I also have the weight on the left side of my bike and not balanced so I thought that may be it.

 

[cal3thousand]

I'm interested in a cargo bike and the yuba mundo is on the list. I would expect some flex from this frame since it is hi-ten steel. But your description using "... a lot..." doesn't make me excited about getting that new frame.

 

[melodious]

Can you go further into detail of the flex? Is the flex lateral or horizontal in nature? I too am thinking of using a v4 yuba frame as my maiden voyage e-build and would like to make sure the frame is up to par. Are you sure it's not the additional position of the batteries/controller/hub that is causing some kind of harmonic vibration at a certain speed?

 

[pdf]

I am betting it is coming from the wheels, not the frame. I have an Xtracycle and esp when heavily loaded, it gets a bit wonky in the rear. I am pretty sure it is coming from the wheels.

 

[scphantm]

a buddy of mine that knows more about bikes than i do checked it out. the direction of the flex is the front wheel goes left the rear wheel goes right, whatever direction you want to call that. but he checked it out and said its the wheels and the forks, not the frame. the front spokes can go a little tighter but he said don't go very much with this wheel, he is suggesting a much heavier duty hoop.

 

[dogman dan]

Sounds like you just discovered tail wag. Likely not really all that bad, but it sure looks alarming the first time you see it.

It's caused by very heavy loads on the rear end of a bike, long or short. Rear hub and rear battery just about garantees it, as does just a set of very loaded panniers if the motor is elsewhere. Pedaling input turns into a tail wag, with the wag increasing porportional to the push on the pedals. This flexibility also has a good chance of getting turned into a high speed wobble, or even a low speed wobble if you let go of the bars completely.

Though this won't be the case with a mundo, a flexy and loose rear rack can make this wag worse. So look for anything loose back there. Your battery strapped in tight? or flopping around some?

 

[scphantm]

It's not the rear that's the problem, it's the front. On motorcycles spokes are to be tight enough to ring when you hit em with a screwdriver. My buddy said the hoop that comes with the Mundo wouldn't handle anywhere near that torque. He recommends a new heavier duty one

 

[dogman dan]

Just telling ya why all my cargo carrying bikes wag thier tails. The force is coming from where the weight is. Your's would never do that though. Not that a floppy front wheel couldn't make it worse. Everything on a heavyweight bike need to be tight, that's for sure.

 

[chaosbarbie]

Just an FYI, the Mundo V4 is made out of CroMoly steel, not High-Ten steel.

 

[cal3thousand]

Just an FYI, the Mundo V4 is made out of CroMoly steel, not High-Ten steel.

Just another FYI, the V4 is made of High-Tensile Steel. NOT Cromoly. Only the sideloaders are made of Cromoly.

From Yubaride.com:

A solid foundation
Picking every component by hand has its pleasures. We know. That's why we're happy to provide this stand-alone frame. You pick the parts that best suit your needs, you build it up, customizing every aspect with the surety of knowing your frame will never let you down.
The Mundo 4.2 features:
• High-tensile steel Frame
• Chromoly sideloaders
• Disc Brake Tabs (Front and rear)
• Sideloader attachments to support any load from passenger feets to large boxes
• Heavy duty 1.2mm tubes
• Threadless headset
• Electric ready
• Uni-frame fit, comfortable for riders from 5 feet to 6.5 feet tall (1.5m to 2m)

Specs:
• BB:68mm | Headtube 1 1/8" | Seat Post ø 34.9mm

Came back to this thread after more soul searching for a cargo bike to fit my life. I keep coming back to the Yuba based on cost and reputation for being sturdy. Since I will be electrifying the cargo bike, strength is more important than lightness in my case.

Going to ask for a Mundo frame for Father's Day. fingers crossed.

 

[Drunkskunk]

It's not the rear that's the problem, it's the front. On motorcycles spokes are to be tight enough to ring when you hit em with a screwdriver. My buddy said the hoop that comes with the Mundo wouldn't handle anywhere near that torque. He recommends a new heavier duty one

All bike rims should have tight spokes. If the wheel wobbles side to side, It needs the spoke s adjusted. If the spokes are also loose enough to notice, there is an extreme problem, and the bike shouldn't be riden untill the wheel is fixed.

It sounds like your front wheel needs a trip to the bike shop. Let a Real bicycle mechanic take a look at it. Maybe your friend knows what he's talking about, and maybe he doesn't. Get a real mechanic to at least look at it anyway.

 

[Bike Xing]

I've seen the Pedego wag until it's tail fell off. The battery rack has holes drilled at the top and bottom right near where it's welded. A crack began at the hole and propagated until failure. The weight back there gets the bikes flexing.
I'm planning on dropping by the Yuba bike showroom this Thursday. I'll look at the bikes and come back with my 2 cents.

 

[100volts+]

Isn't the Yuba Mundo the bike with the notoriously weak front fork. Some guy in this forum nearly killed himself because the front forks broke. I could be wrong though. My memory isn't that good these days.


Regards,
RW, Pedego dealer (just kidding)

 

[Mundo]

I have two Mundos, first one is a V2 with a DD 36vdc on the front and the other is a V4 with a UC mid drive 48vdc ...the V2, is a much stronger built frame.but mid drive is the way to go! Also, keeping the weight as low as possible is a must.

The components that come on these bikes are pretty weak and finding replacements components is difficult.

I've been looking for a new rear disc ready 48 hole freewheel hub with a 14mm axle...Yuba appears to be the only game in town.

But their hubs and wheels are basically entry level components.

Wonder how many Mundos are on this forum and how they have been upgraded.

 

[cal3thousand]

I have two Mundos, first one is a V2 with a DD 36vdc on the front and the other is a V4 with a UC mid drive 48vdc ...the V2, is a much stronger built frame.but mid drive is the way to go! Also, keeping the weight as low as possible is a must.

The components that come on these bikes are pretty weak and finding replacements components is difficult.

I've been looking for a new rear disc ready 48 hole freewheel hub with a 14mm axle...Yuba appears to be the only game in town.

But their hubs and wheels are basically entry level components.

Wonder how many Mundos are on this forum and how they have been upgraded.

You're in SM? Where did you buy your Mundos? I'm in MDR and find it difficult to test one.

As it stands, I'm planning to buy just the frame and use my own 24" rims (I hope this will work on this frame) giving me a lower center of gravity and stronger wheels.

 

[aroundqube]

May be off topic, but some folks may want to know that there is a safety recall on the Mundo V-4.0 They are providing free rear wheel covers so that childrens feet can not get into the wheel. Also known to us oldtimers as skirtguards.

 

[neptronix]

Isn't the Yuba Mundo the bike with the notoriously weak front fork. Some guy in this forum nearly killed himself because the front forks broke. I could be wrong though. My memory isn't that good these days.

Regards,
RW, Pedego dealer (just kidding)

:lol:

Ok, i've seen brand new ones in at a local showroom - they have a much stronger looking fork. Not the one that looks like it's designed to fail on purpose..

 

[Mundo]

I bought my Mundos' directly from Ben at Yuba. Ben has been helpful and occasionally thrown in a few extras.
Unfortunately, Yuba doesn't have any distributors in the Los Angeles area. Too bad they don't, the Mundo is a practical format for , family biking, shopping, picnicking an much more. I am starting to see more and more utility bikes here in Santa Monica, mostly related to family biking.

Back to the original topic, I am not experiencing frame flex with the mid-drive on my V4.
The V2 is built so strong, it's a different animal..
My bigger concern, is the cheap rims, hubs and steel spokes, (here by the beach, they are rusting pretty fast). I frequently use these bikes to their weight limits, the wheels/hubs are the weak link.
It looks like tandem hubs and wheels might be an option, however, real expensive. I'll continue searching

 

[boostjuice]

I've been looking for a new rear disc ready 48 hole freewheel hub with a 14mm axle...Yuba appears to be the only game in town.

But their hubs and wheels are basically entry level components.

Wonder how many Mundos are on this forum and how they have been upgraded.

I run and recommend a Halo SAS 48H rim mounted to Halo 48H Spindoctor 10mm threaded axle (Halo SAS Pro rear wheel) with 14mm 'Axemen' converters. The Spin Doctor's hub bearings ride on a 12mm shaft so not quite as strong as the standard 15mm bearing ID yuba rear wheel (although the cluster side bearing is located further outward toward the dropout = superior) however overall it is a much higher quality wheel with provision of a freehub instead of the prehistoric screw-on freewheel clusters Mundo users are forced to deal with on the standard wheel. Oh, and 14G spokes mean they actually have some springiness in them over the 13G spokes on the factory rear wheel, thus allowing for a more robust wheel. I irredeemably flat spotted my factory rear wheel due to this poor selection choice of spoke gauge.

 

[Mundo]

boostjuice,

Big thanks for the Halo links!

 

[-dg]

Just an FYI, the Mundo V4 is made out of CroMoly steel, not High-Ten steel.

Just another FYI, the V4 is made of High-Tensile Steel. NOT Cromoly. Only the sideloaders are made of Cromoly.

However, CroMoly steel is not stiffer than High-Tensile (carbon) steel. It is stronger, but not stiffer. And generally a bike made with lower strength steel requires more steel to avoid early fatigue failures. If the geometry and tube diameters are the same, then a bike made from carbon steel will have thick walled heavier stiffer tubing. Which is why they are so clunky to ride. Of course stiffness mainly depends on shape which is why you can build also unpleasantly stiff bikes from aluminum or even plastic.

Many people are also under the impression that stiffer is better, but this is more generally applicable to boners, and less so for bicycle frames.