arex

I recently acquired a '92 Burley Rock'n'Roll tandem that needs some attention. The frame is sound, but the wheels are showing their age, with a fair amount of braking wear on the rims. The hubs are Suzue (sp?) with Sun Chinook rims, 36h front and back, with an auxiliary drum brake on the back.

My intent is to build new wheels based on Sun RhynoLite rims and Deore XT hubs, and eliminate the need for the drum brake by upgrading the canti brakes to V-brakes. However, as I started gathering stuff together, I came to learn that tandems' rear hubs are generally 140mm wide, and the Deore XT hub I intended to use is 135mm.

I have two questions about this. First, is it feasible to cold-set the dropouts DOWN to 135mm? I've cold-set a couple of older steel frames to accommodate wider hubs with good results, so I'm comfortable with the process...however, I've never heard of anyone cold-setting down to a narrower hub, and I don't know if there's a problem with that. Also, this frame is very, very stout, and I'm not sure how receptive it would be to cold-setting...on the other hand, it would be only 5mm.

Second, do I need to consider that there's a good reason for the rear hub to be 140mm? I picked the XT hub because I know it can take a lot of abuse, more than is likely to be dished out by a tandem (not taking it off any sweet jumps)...but I also realize that the stresses a tandem puts on a hub (high, constant weight) isn't the same as what a MTB hub is built for. Do I need to be looking for a hub that's made for tandems specifically?

WheelsNT

Several thoughts:
The drum brake and the rim brakes serve different purposes. The rim brakes are to stop the bike. The drum brake is a drag brake to keep speed under control on long/steep descents. You apply a drag brake to an appropriate level, and then leave it there until you reach the bottom. The drum can dissipate a huge amount of heat without failing, unlike rim (or even disk) brakes, so they can be safely applied for extended periods. If it’s not set up this way already, you want the drum brake on a completely different lever than the rim brakes. Usually people use an old thumbshifter so they can set it to a level and have it stay there.

Several different OLDs (over-locknut dimensions) have been used for tandems. Yours might very well be 140mm, but you want to measure. The current standard for most tandems is 145mm. Santana uses 160mm, but they are the only one who does. The reason to use a wider OLD is to increase the angle on the spokes to reduce the dish on the drive side, which takes huge stresses on a tandem. So if you were going to cold-set it, rather than reduce the OLD, you should go to 145mm which would make you compatible with most tandem-rated hubs produced today. However, this really isn’t necessary unless your team and/or riding are too much for a 140 OLD wheel. There are plenty of 140 hubs and wheels available. One thing you do want to do is get a cassette hub. Freewheel hubs tend to break axles on tandems. The extra axle support on a cassette is a big benefit for tandems.

As to a “tandem” specific vs non-tandem specific hub, it will depend on your team weight and where you want to ride. This is an MTB tandem, after all. If you want to do serious off-roading, or if your team weight is 400-500 lbs, you need the strongest stuff you can get. If your team weight is 250 lbs and you never intend to leave the pavement, regular road bike stuff may be ok. The bracing angle of the spokes is the biggest factor, but the hub internals and the hub flanges are also stronger on tandem hubs. MTB tandems use very low gears in steep terrain that can put lots of torque on a hub and sometimes tear up the internals. Lastly, if it were me, I’d stick with hubs that are threaded on the off side to you can retain the drum brake.

Hope that helps!

CliffordK

The wider the rear hub, the less dishing needed. Especially with more gears. That means that the wheel effectively has more support on both sides.

As @WheelsNT suggests, first verify your current dropout spacing.

You can purchase longer rear axles:
https://wheelsmfg.com/products/hub-p...s/axle-04.html
https://wheelsmfg.com/products/hub-p...s/axle-29.html

It would be easiest enough to take your desired hub, and swap axles and toss in a couple of extra NDS spacers to more or less center the hub.

OneIsAllYouNeed

I recommend keeping the frame rear spacing at 140, 141, or 145mm. A 135mm cassette hub has a lot of dish, so spokes don’t last as long. Regarding the hub standards...
140mm: outdated tandem standard from 1980s and 1990s. No new hubs available. Most 140mm spaced hubs had drum brake threads.
145mm: tandem standard 2000s and 2010s. New hubs are still available, but many manufacturers as phasing them out. Most 145mm hubs had either drum threads or IS disc brake mounts.
148mm thru axle: The standard for high end tandems in 2018 and 2019. Increasing number of hub options are becoming available.
141mm: Also known as boost QR. This has emerged as a cheaper option than thru axle on some plus tire mountain bikes. The hub shell is identical to 148mm thru axle.

The Deore LX or XT hubs should be fine for tandem use. We have two that I respaced to 145mm with the Wheels MFG axle 29 (and 2X 5mm spacers). So far so good, but they have less than 5k miles each.

Darth Lefty 

Recommend you contact a tandem vendor for a hub... and advice on the rest of the wheel. If you can’t find an old standard hub, it’s possible to use a newer boost or super boost hub that has end caps to make it QR... the spacing is at least closer, though you lose the drag brake. MTB Tandems is using DT Swiss Hybrid 350 hubs.

L134 

Tandems East lists several hubs with 140mm spacing.

Darth Lefty 

It isn't really. The "MTB"' features are 26" fat tires and a flat handlebar. Other than that it's pretty much just like the equivalent road model.

unikid

I agree with all the points made by OneIsAllYouNeed. Be sure to measure the dropouts with a caliper to know exactly what you are dealing with.

135mm hubs are fine. Ventana uses 135mm spacing on their full suspension MTB frames. There are many heavy teams using it.

If your frame ends up being 140mm, using a longer longer axle and 2.5mm spacers on either side to keep the hub centered should work.

If you are looking to build 36-spoke wheels this might be a good source for the rims: https://www.jensonusa.com/Sun-Rhyno-ABT-Lite-Rim

CliffordK

Unless this is a fixie, put all the spacers on the NDS side.

The point of the 140/145mm hubs is to reduce dish (space the NDS side to similar to the DS side).

I posted a link to some replacement axles if you wish. I think the standard is about 3mm of axle on each side. But, with wider modern dropouts, I like the axle length to be long enough to fill the dropouts.

If the OP has already built wheels, then still put the spacers to the NDS side, and hopefully one can redish the wheel as necessary.

unikid

I assume by "NDS" you mean Non Drive Side (i.e. Left side)? If so, I see your point. Put any spacers on the left side of the hub only. So the cassette remains flush to the right. Then build (or re-dish if existing) the wheel so the rim is centered and the spokes on the Drive Side (Right side) end up being less vertical and overall strengthening the wheel.

arex

I've considered everything brought up thus far.

• I have most of the parts to build the wheels, but they're not built yet. I'm still waiting on the front hub to arrive. I was waiting to learn more about what I ought to do here before proceeding.
• I feel comfortable eliminating the drum brake. This bike is pretty much going to be for leisure, not touring, so my wife can ride with me. I don't anticipate any long steep hills, at least with her along. It's needless weight and complication. The previous owner said that while he and his wife did plenty of long distance rides in hilly terrain (northern Colorado), he never once used the drum brake. I figure I can sell the brake and recoup some money. I'm also comfortable eliminating the drum brake because the later models of this bike no longer had the brake (2000 or so).
• The OLD of the original hub is 140mm. I also did some measurements of both hubs to compare spacing and off-centerishness (I know there's a proper term for that, but I don't know what it is), and I found that the dimensions differed very little. I can see the benefit, though, of swapping in a longer axle and using a 5mm spacer on the NDS. On the other hand, I'm not sure there'd be enough benefit to reducing the dishing that little to make it worth the trouble. Again, this will be a farting-around bike that I don't think will be enduring any unusual stress.
• I did a test fit of the XT hub in the dropouts and the stays are easily flexible enough to squeeze down to the 135mm hub. I think doing a cold set would be successful with little risk.

So, I think what I'll do is use the XT hub, and either replace the axle and shift the hub over 5mm, or use it as-is and cold-set the frame. I realize that the former would be a more desirable plan, but I'd need some convincing that it'd be enough of an advantage over the latter to make it worthwhile.

Anyways. Thank you all...this was educational.

LV2TNDM

I would disagree with going with LX or XT when the Shimano tandem hub is an option at about the same price. If you're riding a tandem with low mountain gearing, you risk spinning the cassette body off of the aluminum hubshell. I know because I did exactly this on an LX hub climbing a steep, but not unreasonably difficult dirt fire road. In other words, it wasn't steep enough to lose traction under my 100 lb. stoker. Instead, the hub failed.

The Shimano tandem hub uses a steel spline interface between the cassette body and the hubshell, eliminating this failure point. Now I must admit that I'm referring to the old version with drum brake threading on the other side. However, I assume they've simply transferred over the design to the current disk model(s). I could be wrong.

It would be a shame to have nice new wheels built around a hub that cannot withstand the high torque loads a tandem team exerts on the rear hub/freehub body.

quemazon

Newer mountain bike hubs use boost spacing and thru-axles that have a 148mm spacing. But they also usually have replaceable end caps that allow you to use regular quick release skewers. This also makes the spacing 141mm (instead of 148mm). That route would be a much better fit for your frame.

Carbonfiberboy 

I agree with going to 145mm. It's not just axle length, it's flange spacing. My 2003 145mm Chris King rear hub has almost symmetrical flange spacing, very nice. That hub is still going strong. That hub doesn't have NDS threading for a drum, so I built a second rear wheel using a White Industries threaded hub (no longer made) so I can use a drum for touring and very steep mountain rides. Touring on a tandem is a gas, BTW. You have a drum. They are no longer in production and much sought-after, so I wouldn't abandon it without giving it some thought. Having 2 rear wheels is also a good idea. One can borrow a front from a single for a while if you ride carefully, but not the rear.

The whole problem with that paragraph is that it assumes one could buy a 145mm threaded tandem hub. That may no longer be possible, in which case stay with the hub you have and just rebuild the wheel with a new rim. That's the least expensive option and very possibly also the best option. The only bad thing about the threaded hub is that the Akai drum is a bit heavy, but so what.