Tandem Cycling - Tandems and Faster Wheels / Rims

A recent ride saw the demise of our Velocity Dyad 40 hole rear rim. The rim developed circumferential cracks adjacent to the spoke holes.

I ordered another of the same rim, just being lazy. It should arrive soon and will be an easy swap.

When I noticed the cracks, it was after the Saturday ride in Vero with the PANTHERS tandem club. Sunday morning, after lockwiring the spokes to prevent a possible drivetrain lockup, I was talking with Bob Thompson, and he recommended having some taller profile wheels built.

I do have another set of hubs, and am now wondering, without going the cost of specialty wheels, or the price of carbon rims, what is an optimum rim height for the 25mm or 28mm tires. Seems it's a weight vs aero tradeoff.

BTW, my hubs are 40 hole, so whatever I decide will still be 40 spoke wheels.

Veocity offers a few possible choices.


Having discs front and rear, we could run these 43mm tall, 19mm wide / 770 gram

http://www.velocitywheels.com/store/product.asp?pID=20&cID=18



These were popular on some bikes at Vero 30mm tall, 19mm wide / 518 grams

http://www.velocitywheels.com/store/product.asp?pID=23&cID=18



Another possibility and wider 32mm tall, 24mm wide / 650 grams

http://www.velocitywheels.com/store/product.asp?pID=21&cID=18



Our current rims are these. 22mm tall, 24mm wide / 480 grams

http://www.velocitywheels.com/store/product.asp?pID=24&cID=18

This is a balance of cost vs performance for recreation type rides, group events and training rides.

Also open to any good articles or links on this to save you folks some keyboard strokes.

Thanks
PK

I had the Velocity Dyad wheels and switched to the Velocity Deep V you have listed. I really like the deep V,s they are a solid wheel and they seem to roll better. I have them on White Ind. hubs.

IMHO, it's better to focus on durability than speed with tandem wheels. With that in mind, I believe the Deep V Velocity rims are supposed to be pretty stout.

We're a 350 lb. team and our daVinci is using the stock V-22 40h wheels. These are very affordable and seem bullet-proof.

It is interesting that you have disc brakes and have this rim problem. It is my belief that disc brakes add additional stress to the spokes and rim.

We've had Deep V's on Phil Wood hubs for the last year or so, after our Rolf's failed yet again. Liking them a lot, but way too early to claim anything about lifespan, etc. We also have a pair of daVinci V-22s on White Ind. hubs that were the originals on our Erickson, but these have a history of breaking spokes despite a complete rebuild. 330 lb team.

Ditto on the Deep"V" and White Ind hubs. Roll fast and strong.

It is interesting that you have disc brakes and have this rim problem. It is my belief that disc brakes add additional stress to the spokes and rim.

No doubt the discs do add more stress. Some brake manufacturers specify how they want the wheel laced.

I have no babied these wheels, and I likely run too much tension but prefer no flex on the back.

I'll cut a cross section and see, maybe the spoke holes were counterbored too deep, then again, maybe not.

Any info about the aero benefits based on rim height? The Zipps get pretty tall in the name of speed, just curious how it all relates.

PK

I have no babied these wheels, and I likely run too much tension but prefer no flex on the back.

Tension won't affect flex, as long as the spokes aren't going slack. (But if spokes are going slack, the wheel isn't going to last anyway).

IMO if you're not checking spoke tension with a tension meter, and keeping it at the rim manufacturer's recommended tension, no tandem wheel will last. I'm also a firm believer in using 14-15 double butted spokes, not straight gauge. I've never broken a spoke or had a rim crack on any bike. Of course I'm not running Rolfs on our tandem, though I've run Rolfs on one of my singles for many years. On our tandem we run ordinary 36H wheels, with a variety of rims. We're a 310 lb. team, and have toured loaded on the same wheels we use for sport rides, without any issues. We have rim brakes.

IMO if you're not checking spoke tension with a tension meter, and keeping it at the rim manufacturer's recommended tension, no tandem wheel will last.

Without coming off as a smarty pants, this Manufacturers Recommended Tension should be found where?

The rims were 700c Velocity Dyads

The US distributors site is here

http://www.velocityusa.com/default.asp?contentID=584

The Australian site is here

http://www.velocitywheels.com/store/categories.asp?cID=18

I'll gladly use a tensiometer for the rebuilding of the wheel, could not find the spec on either site, could you please help?

PK

Tension won't affect flex, as long as the spokes aren't going slack. (But if spokes are going slack, the wheel isn't going to last anyway).

Not to cause a debate, but if the tension has slackened slightly, I can feel the back end sway. We are no powerhouse or hardcore riders, but for us it can be felt.

I did a bit of looking and this seems to note wheel flex and factors that can have an effect. If the report is flawed that's fine too.

http://www.rouesartisanales.com/article-23159755.html

Based also on disc brake manufacturers recommendations, they want high tensions.

PK

Thank you all for the input, now I just need to decide what route to take.

PK

Without coming off as a smarty pants, this Manufacturers Recommended Tension should be found where?

The rims were 700c Velocity Dyads

The US distributors site is here

http://www.velocityusa.com/default.asp?contentID=584

The Australian site is here

http://www.velocitywheels.com/store/categories.asp?cID=18

I'll gladly use a tensiometer for the rebuilding of the wheel, could not find the spec on either site, could you please help?

PKWhat I've done is email the rim manufacturer. I've always gotten a response. This is a response I received from Velocity:


We build all of our wheels at the same spoke tension. Spoke tension is measured in Kilograms of Force (KGF). We build the front wheel between 105 – 115 KGF, and the rear between 110 – 120 KGF. I hope this helps, let me know if you have any further questions.

Thanks for riding Velocity.
MD
Matthew Dennis
Customer Service/Sales
Velocity USA
616.243.3400
md@velocityusa.comOn my CK rear hub I went ~115 KGF both sides, since it's almost symmetrical. I think I went 110 on the front. On an asymmetrical rear hub, you go 115-120 DS, and then whatever on the NDS that centers the rim. So it doesn't matter how many spokes, doesn't matter which rim. I don't know of a traditional rim that wants tensions different from these, though my knowledge is limited to Velocity and Mavic. In general, I've found taller section rims build up stiffer and stronger wheels. Hence we bow before the beauty of the Deep V for up to 28c tires.

These tensions will really stretch a 14-15 DB spoke, which is a good thing.

Since you live in Florida and probably seldom ride in the mountains or hills the Deep Vs make since. About two years ago Velocity got some bad aluminum and had several rims crack. I had one of those rims crack in 950 miles although mine cracked around the side wall. Velocity was very good about replacing the rims. They even replaced my front rim which was not cracked but bought at the same time. I took the wheels to Velocity USA in Grand Rapids and had the wheels rebuilt with new rims for no charge. The rear rim that I have had last the longest (by far) is a Velocity Dyad with a disc brake.

What I've done is email the rim manufacturer. I've always gotten a response. This is a response I received from Velocity:

On my CK rear hub I went ~115 KGF both sides, since it's almost symmetrical. I think I went 110 on the front. On an asymmetrical rear hub, you go 115-120 DS, and then whatever on the NDS that centers the rim. So it doesn't matter how many spokes, doesn't matter which rim. I don't know of a traditional rim that wants tensions different from these, though my knowledge is limited to Velocity and Mavic. In general, I've found taller section rims build up stiffer and stronger wheels. Hence we bow before the beauty of the Deep V for up to 28c tires.

These tensions will really stretch a 14-15 DB spoke, which is a good thing.


Thanks for those specs.

Replacement Dyad rim arrived. Borrowed the tensiometer from my buddies shop. With both tire pressures at about 25 psi, I checked the existing wheel builds.

Front is spot on to the range you published, with an inflated tire it will drop some. Possibly to the lower end of the range or below that.

The rear wheel, which still runs true, with a deflated tire, was less than 10 kg above the specs you provided. Adding 120 psi to the tire will likely place those tensions in spec.

Good and bad, bad is the rim failed, but nothing serious. Good is that even though I don't always use a tensiometer, I can still get the spokes tensioned without one. I'll buildup the wheel this weekend. I'll compare as I go to see if what I like in regards to tension and how the bike rides compares to how the tensiometer reads them.

Not one complaint about the Dyad rim, and for all the wheels I have built for myself, wife and friends, this only the third to crack a rim. The others were high mileage MTB wheels with brake tracks almost worn through.

Thanks for those specs. BTW, did they mention if that is for Velocity hub with any particular brand of spokes.

Thanks
PK

Thanks for those specs.

Replacement Dyad rim arrived. Borrowed the tensiometer from my buddies shop. With both tire pressures at about 25 psi, I checked the existing wheel builds.

Front is spot on to the range you published, with an inflated tire it will drop some. Possibly to the lower end of the range or below that.

The rear wheel, which still runs true, with a deflated tire, was less than 10 kg above the specs you provided. Adding 120 psi to the tire will likely place those tensions in spec.

Good and bad, bad is the rim failed, but nothing serious. Good is that even though I don't always use a tensiometer, I can still get the spokes tensioned without one. I'll buildup the wheel this weekend. I'll compare as I go to see if what I like in regards to tension and how the bike rides compares to how the tensiometer reads them.

Not one complaint about the Dyad rim, and for all the wheels I have built for myself, wife and friends, this only the third to crack a rim. The others were high mileage MTB wheels with brake tracks almost worn through.

Thanks for those specs. BTW, did they mention if that is for Velocity hub with any particular brand of spokes.

Thanks
PKThat's the whole body of the email. My guess is that hub and spokes don't matter to the spec, just to the longevity of the wheel. I also go through brake tracks here in the PNW, so I've probably never had a wheel go over 10,000 miles, except maybe the Open Pro Ceramics on my rain single. Could be why I've never had a rim crack.

Agreed. Disc brakes on a tandem, with much higher bike and rider mass than on a single bike, will cause much higher stress at the rim-spoke juncture.

I'm not 100% convinced but pretty certain the rim failed from fatigue / use.

So now back on topic, I am rebuilding the original Dyad wheel assembly with a new Dyad rim.

For my other wheels I'll build up, I have hubs already, just need rims and spokes.

I have suggestions of a Mavic CXP33, Velocity Deep V's and I myself am considering a B43 possibly for the rear.

So anyone have thoughts about the trade off of aero vs weight. Hearing the trailing edge or rear wheel matters most, and also that the heavier rim on the back won't be noticed as much for weight initially but may after a couple of hours of riding.

PK

Rodriguez says they run heavier rims and more spokes on tandems with disc brakes. Now just because a rim is heavier, doesn't mean it has more wall thickness at the nipple. Obviously the rim can be just wider or taller. We ride with another tandem with a rear disc that has cracked a Dyad. I think it's worth more research. Another thing that might be in favor of the Deep V or similar for this application is that the rim shape might act to prevent flexing and thus cracking. Of course those two rims are designed for different tire widths, so that will be a factor. I put on a CXP33 rear rim recently, because I needed a rim that day and that's all I could find locally. It's an eyeleted rim. Maybe the eyelets spread out the stress, maybe not.

I don't think rim weight is as important on a tandem as it is on a single, at least for us. We never accelerate the bike quickly, so it doesn't seem like an issue unless the team is strong and climb a lot out of the saddle. I'm very happy with rims which don't need much spoke adjustment and which don't come out of true when I have some little issue on the road. So far, the CXP33s and the Deep-Vs have been the best at that. Haven't run Dyads. Since a Deep-V is 40g heavier than a Dyad and narrower, I'd sure think it would be stronger. The aero is a bonus, IMO. On a tandem, I'd guess that you're mostly faster with a heavier aero rim than a lighter flat rim, since a tandem is often faster on the flat than a single. Be interesting to hear what others think.

Agreed. Disc brakes on a tandem, with much higher bike and rider mass than on a single bike, will cause much higher stress at the rim-spoke juncture.

Do you mean higher stress than rim brakes? I have often heard this, and it seems somehow intuitive, but I would sure like to see it explained in diagrams, numbers, vectors, forces, etc. I have tried to think through the fact that when braking, the friction that stops the bike is between the tire and the road. The weight is almost entirely the riders who connect to that tire/road interface via their saddles, handlebars and pedals, through the frame and fork to the hubs, to the spokes, to the rims. So how can there be more stress on the rim spoke junction for one brake over another? Can an engineer or physicist give a lesson here? Curious minds need to know.

Rodriguez says they run heavier rims and more spokes on tandems with disc brakes. Now just because a rim is heavier, doesn't mean it has more wall thickness at the nipple. Obviously the rim can be just wider or taller. We ride with another tandem with a rear disc that has cracked a Dyad. I think it's worth more research. Another thing that might be in favor of the Deep V or similar for this application is that the rim shape might act to prevent flexing and thus cracking. Of course those two rims are designed for different tire widths, so that will be a factor. I put on a CXP33 rear rim recently, because I needed a rim that day and that's all I could find locally. It's an eyeleted rim. Maybe the eyelets spread out the stress, maybe not.

I don't think rim weight is as important on a tandem as it is on a single, at least for us. We never accelerate the bike quickly, so it doesn't seem like an issue unless the team is strong and climb a lot out of the saddle. I'm very happy with rims which don't need much spoke adjustment and which don't come out of true when I have some little issue on the road. So far, the CXP33s and the Deep-Vs have been the best at that. Haven't run Dyads. Since a Deep-V is 40g heavier than a Dyad and narrower, I'd sure think it would be stronger. The aero is a bonus, IMO. On a tandem, I'd guess that you're mostly faster with a heavier aero rim than a lighter flat rim, since a tandem is often faster on the flat than a single. Be interesting to hear what others think.

The additional rim weight is not in regards to added strength around the spoke holes. My current thoughts are to run the 43mm tall B43 rim on the rear, and this is disc specific with no brake tracks, and run a non machined (no machining for the brakes just anodize) Deep V up front with a front disc setup. The additional weight is probably mostly in the height, but the 43mm tall rim is disc only so maybe the spoke bed is beefed up.

This would give a 770g 43mm tall rear rim, and a 518g 30mm tall front rim, both are 19mm wide.

PK

Do you mean higher stress than rim brakes? I have often heard this, and it seems somehow intuitive, but I would sure like to see it explained in diagrams, numbers, vectors, forces, etc. I have tried to think through the fact that when braking, the friction that stops the bike is between the tire and the road. The weight is almost entirely the riders who connect to that tire/road interface via their saddles, handlebars and pedals, through the frame and fork to the hubs, to the spokes, to the rims. So how can there be more stress on the rim spoke junction for one brake over another? Can an engineer or physicist give a lesson here? Curious minds need to know.Engineering background here, not a PE. With rim brakes, the only braking force on the spokes is that forward pressure on the hub caused by the bike's deceleration. That's maybe .5g max? So half the weight of the bike, riders, etc. Not so much really, because you'll pull more g's than that hitting a big bump. And all the spokes on the trailing edge of the wheel are involved in that deceleration, both leading and trailing spokes.

But with a disc, you have that same deceleration force with the added stress on the spokes cause by the hub "winding up" the wheel. The force of the caliper on the disc has to be transferred to the hub and then to the rim by only the trailing half of the spokes, before the rim can transfer it to the tire and thus to the road. Because only half the spokes are involved in preventing the wheel from winding up, it seems to me that the deceleration force on the spokes could be twice as high with a disc as with rim brakes.

To put that in perpective, say we add a total force of 1g to the spokes, half distributed among all the trailing spokes, and half among all the spokes on the trailing edge of the wheel. From this earlier discussion, we see that manufacturers spec ~110 KGF or over 240 lbs. preload on each of the 72 or more spokes involved in the deceleration. So it's not that great a percentage increase or decrease in tension. So we shouldn't break steel spokes. However we might deform the aluminum rim slightly, and aluminum is sensitive to fatigue There is great resistance on the part of cyclists to the manufacturer adding a lot of extra weight to the rim to prevent fatigue.

The additional rim weight is not in regards to added strength around the spoke holes. My current thoughts are to run the 43mm tall B43 rim on the rear, and this is disc specific with no brake tracks, and run a non machined (no machining for the brakes just anodize) Deep V up front with a front disc setup. The additional weight is probably mostly in the height, but the 43mm tall rim is disc only so maybe the spoke bed is beefed up.

This would give a 770g 43mm tall rear rim, and a 518g 30mm tall front rim, both are 19mm wide.

PKThe Velocity sections show the spoke bed being heavier in the B43 and Deep V. The Dyad also shows thickening, but that area looks narrower on the Dyad. Just for fun, I bought my last Aeroheard front rim unmachined and sanded off the anodizing myself, hoping to save some rim material, my guess being that they anodize them all then machine, hence $5 cheaper for unmachined. BTW, don't try that yourself unless you have professional sanding equipment like I do.

I do have another set of hubs, and am now wondering, without going the cost of specialty wheels, or the price of carbon rims, what is an optimum rim height for the 25mm or 28mm tires. Seems it's a weight vs aero tradeoff.

This is a balance of cost vs performance for recreation type rides, group events and training rides.

Check the Zipp or HED sites, I believe one has some data relating rim height to drag. IIRC, aero benefits kicked in at 30mm rim height and modestly improved as rim height increased. Below 30mm rim height didn't play a significant role in reducing drag.

Assessing the trade-off of weight vs. aero is highly dependent on individual riding demands/goals: Weight is pretty unimportant for pure time trial applications, but becomes more important for climbing or pack riding/road race applications (where the ability to easily accelerate is prized).

You must be routinely riding at about ~ 22 MPH on the flat for aero benefits to start to kick in. At 25+ MPH they will become substantial (Just my rule of thumb, FWIW).

Typically recreational cyclists overemphasize aero and underemphasize weight in making equipment decisions (again, FWIW).

Can an engineer or physicist give a lesson here? Curious minds need to know.
I am a mechanical engineer.
A rim brake applies the braking force directly to the rim and tire. A disc brake creates a torque moment about the hub's axis of rotation; the moment's force vector must be transmitted via the hub flange to the spokes, rim, and tire. On a tandem, these stresses are definitely significant. Without doing real calculations, it should be obvious that a disc brake equipped wheel should have a heavier rim and higher spoke count to accommodate the stresses. I will sit down and do the free body diagram and the basic dynamics next time I get the urge...

Thank you for this explanation. This is exactly what I thought.

Wayne


I am a mechanical engineer.
A rim brake applies the braking force directly to the rim and tire. A disc brake creates a torque moment about the hub's axis of rotation; the moment's force vector must be transmitted via the hub flange to the spokes, rim, and tire. On a tandem, these stresses are definitely significant. Without doing real calculations, it should be obvious that a disc brake equipped wheel should have a heavier rim and higher spoke count to accommodate the stresses. I will sit down and do the free body diagram and the basic dynamics next time I get the urge...

I will sit down and do the free body diagram and the basic dynamics next time I get the urge...

Thanks for the quick explanation, but I am waiting for the full monty, too.

I have had really good experience with Velocity rims.
I have used multiple sets of Aeroheads on my single and Fusions on my tandems.
Fusions at 25mm deep are lighter than Deep Vs but still plenty strong for our 250 lbs.
Velocity does have great customer service. I have an Aerohead rim that had a blip at the joint that was worse than what I thought it should be and they sent me a new rim, no questions asked.

What I've done is email the rim manufacturer. I've always gotten a response. This is a response I received from Velocity:

On my CK rear hub I went ~115 KGF both sides, since it's almost symmetrical. I think I went 110 on the front. On an asymmetrical rear hub, you go 115-120 DS, and then whatever on the NDS that centers the rim. So it doesn't matter how many spokes, doesn't matter which rim. I don't know of a traditional rim that wants tensions different from these, though my knowledge is limited to Velocity and Mavic. In general, I've found taller section rims build up stiffer and stronger wheels. Hence we bow before the beauty of the Deep V for up to 28c tires.

These tensions will really stretch a 14-15 DB spoke, which is a good thing.

The new rim is laced, and trued. I utilized a tensiometer. Without a mounted and inflated tire, which tends to drop the tension, Spokes both sides are balanced for tension.

I did not obtain the kgf values you posted yet. At the lesser end of the range, you posted 110. At 100 kgf, these are very tight, to the point I am content and also planning to get another tensiometer to verify this ones calibration.

Based on a comparison of my building by feel vs using the tool, there is no way the old wheel was too tight in regards to spoke tension. I did notice though, that the old rim showed many threads protruding through the nipples. The new rim shows none of this, leading me to believe the failed rim had likely fatigued, yielded, then began cracking. Regardless though, a good rim, since nothing pulled through, and it still ran true.

I stabilized the tension by adding side load to the spokes. Possibly we can ride it this weekend and I'll reset the tension.

PK

[SIZE=2]As recommended, I emailed the rim company for a spec. Not on disbelief of Carbonfibreboy, but rather to confirm if his response was specific to his rims. I inquired specifically in regards to the Dyads, front and rear, 40 spokes per wheel and 14ga spokes. I also added for the information in building a B43 rear and Deep V front.

This is the reply I received, which does differ somewhat from that of Carbonfibreboys.

Regardless, the rim failure was not from excess tension since I know I have the spokes tight but not that tight when compared to those done with a tensiometer.

The response I received.

We build to all our rims to 110-130 kgf. Good luck with your builds!

Adam Lorenz

Velocity USA
www.velocityusa.com (http://www.velocityusa.com/)
1-800-453-6126
adam@velocityusa.com

Carbonfibreboys response.


We build all of our wheels at the same spoke tension. Spoke tension is measured in Kilograms of Force (KGF). We build the front wheel between 105 – 115 KGF, and the rear between 110 – 120 KGF. I hope this helps, let me know if you have any further questions.

Thanks for riding Velocity.
MD
Matthew Dennis
Customer Service/Sales
Velocity USA
616.243.3400
md@velocityusa.com

I ordered a spoke tensiometer for myself. I will bring both wheels to 120 kgf per my email.

Thanks for all the good advice.

PK

As a follow up, I installed the new rim. Tensioned the wheel by feel since the tool had not arrived. Did a short local ride.

With the tool, tire installed and inflated, reset all tensions to Velocities specs. I also checked the front and found that hand tensioning had the disc side spokes just a bit over the tension recommended and the non disc side settled where they needed for true.

Lowered the front tension to spec.

Put 60 uneventful miles on the wheels last Sunday.

I also took the failed rim and cut a section out of it in the failed area. The failure occurred along the section change in the extrusion as expected.

My honest opinion is metal fatigue / they just wore out...

PK

The new rim is laced, and trued. I utilized a tensiometer. Without a mounted and inflated tire, which tends to drop the tension, Spokes both sides are balanced for tension.

I did not obtain the kgf values you posted yet. At the lesser end of the range, you posted 110. At 100 kgf, these are very tight, to the point I am content and also planning to get another tensiometer to verify this ones calibration.

Based on a comparison of my building by feel vs using the tool, there is no way the old wheel was too tight in regards to spoke tension. I did notice though, that the old rim showed many threads protruding through the nipples. The new rim shows none of this, leading me to believe the failed rim had likely fatigued, yielded, then began cracking. Regardless though, a good rim, since nothing pulled through, and it still ran true.

I stabilized the tension by adding side load to the spokes. Possibly we can ride it this weekend and I'll reset the tension.

PKAfter a little back of the envelope calculation for weight distribution, I think I should be running the same spoke tensions front and back, also. The Velocity email I received was undoubtedly pitched toward single bikes.

I don't think we frequently see rim or spoke failure from overtension. IMO this results from undertension or too thick spokes, hence too little spoke stretch, hence fatigue. Deeper, stiffer section rims will move less in the plane of the wheel as the wheel rolls, thus unloading the spoke tension less than a shallower section rim, thus being even less likely to fatigue.

Honestly, I still am biased to it just was wear and tear. The primary failure was a circumferential crack adjacent to the spoke nipple.

With the rim removed and a close inspection, you can also see many small cracks beginning at the nipples. All rims are made in a production environment, so deburred edges are not there. Rather the exact opposite with the spoke drilling often having knife edges on account of the rims profile. These make awesome places for cracks to begin and propagate from. If I never wanted to ride, I could scare myself by Eddy Current inspecting my rims...that would probably be bad.

Not at, but near the circumferential crack is also a few nicks in the flange. Possibly we ran over some debris and side loaded the wheel and that area failed. As I mentioned before, we are not easy on our stuff, so both on and off-road rims are kind of a wear item. Hopefully not often but it can happen.

BTW, thanks for the tips. As $ and ambition allow, I am pretty certain I'll build up another pair of wheels with my spare hubs. Deep V front and a Chukker or B43 rear.

PK

Honestly, I still am biased to it just was wear and tear. The primary failure was a circumferential crack adjacent to the spoke nipple.

With the rim removed and a close inspection, you can also see many small cracks beginning at the nipples. All rims are made in a production environment, so deburred edges are not there. Rather the exact opposite with the spoke drilling often having knife edges on account of the rims profile. These make awesome places for cracks to begin and propagate from. If I never wanted to ride, I could scare myself by Eddy Current inspecting my rims...that would probably be bad.

Not at, but near the circumferential crack is also a few nicks in the flange. Possibly we ran over some debris and side loaded the wheel and that area failed. As I mentioned before, we are not easy on our stuff, so both on and off-road rims are kind of a wear item. Hopefully not often but it can happen.

BTW, thanks for the tips. As $ and ambition allow, I am pretty certain I'll build up another pair of wheels with my spare hubs. Deep V front and a Chukker or B43 rear.

PKFriends of ours have been sidelined a couple of times by rear wheel failures, rim or hub. That's one of the reasons I built up a second rear, this one with an Arai. Must have operable tandem! The front I can just grab off one of my singles, which work well enough for a few rides as long as I'm careful.