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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 12-03-12, 05:11 PM   #1
Ritterview
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How 135 mm rear hub spacing affects road bike chainline and shifting

With disc brakes making inroads into road and cross bikes, tandems with disc brakes and larger than 130 mm hub spacing are getting more company. Chainline and hub spacing are discussed in considerable technical detail here at Bike Rumor.

TECH BREAKDOWN: HOW 135MM REAR HUB SPACING AFFECTS ROAD BIKE CHAINLINE & SHIFTING



Thereís no doubt disc brakes are well on their way to the road bike market. A few major brands like Colnago and Specialized recently introduced production models, Volagi built their brand with them from the outset, and disc brake cyclocross bikes are pouring in.

But what does all this mean for the other side of the wheel? Weíve covered (here and here) some of the technical challenges and concerns of using disc brakes on road bikes and the changes required for wheels. But the conversationís been missing one critical element of the shift. Virtually everyone thatís making or planning a disc brake road or cyclocross bike has 135mm rear hub spacing on the drawing board.

Thatís 5mm wider than what road bike frames have been designed for. 5mm wider than what decades of drivetrains have been designed around. Sure, thatís only 2.5mm per side, which doesnít sound like much. Until you consider that Shimano only needed 1.8mm to add an 11th cog.

We spoke with the engineers and product managers at FSA, SRAM, Shimano, Specialized, Parlee and Volagi to see how this will affect chain line, shifting performance and heel clearance on what could very well be your next road bikeÖ


More at link, includes complicated tables:

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Old 12-03-12, 05:23 PM   #2
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What is the rear dropout spacing on your bike and would you consider any different wheel selection if you were specing the bike today?

Actually if you were designing a new bike what all would you do different?

Wayne
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Old 12-03-12, 06:59 PM   #3
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What is the rear dropout spacing on your bike and would you consider any different wheel selection if you were specing the bike today?
Mine is 135 mm.
  • Greater selection of hubs, includes mountain hubs.
  • Lesser chainline issues than 145 mm.
  • Less problematic spoke angles than 145 mm with deep rims.
  • Wheel strength gained through deep rims instead of hub width.
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Old 12-03-12, 08:42 PM   #4
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Interesting topic. I have contemplated 135mm for our new tandem. It seems that this spacing may grow beyond the MTB seen with disc brakes coming to CX and likely for some road applications.

As long as we are talking rear spacing for tandems, would anyone consider 132.5mm? Or does this create more problems than it solves?
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Old 12-03-12, 10:16 PM   #5
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Interesting topic. I have contemplated 135mm for our new tandem. It seems that this spacing may grow beyond the MTB seen with disc brakes coming to CX and likely for some road applications.

As long as we are talking rear spacing for tandems, would anyone consider 132.5mm? Or does this create more problems than it solves?
The hub choices are a veritable cornucopia at 135 mm, as the mountain bike segment is so much larger and more competitive than tandems. With 145 mm, a reasonable choice is the Chris King, at 366 grams.



But, if you are a relatively light team, then you might find that a mountain hub will be sufficiently robust (we have thousands of trouble free miles on our DT 240s disc). Your options expand to consider something like the 205 gram Tune Kong. Is the Kong up to the task? Something to discuss with your wheel builder. However, if it is, you've pared 161 grams, just like that.

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Old 12-03-12, 11:14 PM   #6
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I have an original Volagi at 130mm. There are enough disc-compatible hubs available, but a Powertap is out of the question. I've converted mine to a triple and this thread will prompt me to be a bit more analytic about my available gear combinations - unlike our daVinci where I can actually "use" 40 different combinations (don't do so in practice of course), the Volagi is probably somewhere between 24 and 27 speeds -works for me.
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Old 12-04-12, 07:35 AM   #7
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The chainline on most tandem cranksets is a lot wider than on those for single bike cranks. The FSA tandem cranks (both Gossamer and SL-K) have an official chainline of 53 mm (measured to the center of the middle ring), and the new Shimano R603 cranks have a 50 mm chainline. A standard single bike road triple has a chainline of 45mm (and 43.5 for a double, measured halfway between the two rings). This makes 145 mm hub spacing on a tandem approximately equivalent to 130mm hub spacing on a single when using FSA cranks or 135 mm when running Shimano's cranks.

The Bikerumor article also mentions that chainstay length is very important - a lot of the issues only really apply to race bikes with very short chainstays (390 - 410 mm). Our Co-Motion Speedster is off of the bottom of the FSA tables with 438 mm chainstays, so that also avoids most of the problem.

The problematic combination that is the take-home message from the article is that running a standard road double crank, a 135 mm hub, and 400 mm chainstays is going to cause some trouble. The wider chainline on tandem cranks and the longer chainstays mean that 145 mm rear hubs are about right for a tandem. However, if you've got a Santana with a 160 mm rear hub then chainline might be an issue.

Having said all that, we're currently running single-bike triple cranks (Shimano 105 5603 front and rear) on our tandem, with chainrings in only the inner two positions (and a belt drive in the outer position). I've added about 3mm of spacers behind the right-hand BB cup, so the middle/outer ring is at about 48mm, giving us the equivalent of a double crank with about a 45mm chainline. On top of that, the jump between rings is huge - 26 tooth inner and 42 tooth middle/outer. This means that the smallest couple of cogs are totally off limits from the small ring, and I try to use only the largest 6 (of 10) cogs with the inner ring; when I forget we're still in the small ring and start cross-chaining then my stoker is very good at quickly reminding me. When running in the middle/outer ring, the chain is lined up nicely with the center of the cassette, and because of the long chainstays I have no concerns about using all gear combinations from that ring. This setup results in very few redundant gears that are usable, and we do have a large jump in cadence when going between rings, but with the wide-range cassette (11-34), we can do 90% of our riding on the middle/outer ring and rarely need to shift up front; when we do then a couple of compensatory shifts at the rear just beforehand keeps things reasonably smooth. The advantages that we get over using tandem cranksets is a wider choice of crank length (we're running 165 mm cranks front and rear), a narrower Q-factor, and slightly lower weight (due to having one less spider, no big ring, and slightly shorter axles). Of course, we spin out our top gear (42/11) at about 50 kph (30 mph), but we're more into touring than racing, so tend to coast whenever we're above about 40 kph (25 mph), so this is a non-factor (and if we ever needed to do a faster ride, then I could switch the rings for a 32 inner and 46 middle that I have in stock). Anyway, I'm wandering off topic, so I'll stop here.

Last edited by Chris_W; 12-04-12 at 07:43 AM.
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Old 12-04-12, 04:39 PM   #8
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Having said all that, we're currently running single-bike triple cranks (Shimano 105 5603 front and rear) on our tandem, with chainrings in only the inner two positions (and a belt drive in the outer position).
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I recommend triples to everyone but the very fittest people.
So, Chris W, triple expert, triple proponent, Gear Combo Guru, in vertiginous Switzerland, on his tandem, is running a.... double?

This is like learning that the tree-hugging global warming activist whose words you've lived by has purchased a BTU-consuming, 9 million dollar manse in Montecito.

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Old 12-05-12, 07:43 AM   #9
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Chris, I know we are getting off topic but I'd love some additional details/photos of your setup. I'm building up a gravel road tandem from an old Ibis Cousin It and looking for creative ideas.
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Old 12-05-12, 02:38 PM   #10
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Thanks for tolerating my lengthy and geeky post! Those not interested can tune out now.

Ritterview, you're correct that I'm a strong proponent of triples. However, if you look at my thread that you linked to that includes the index of road triple cranksets, you'll see that the criteria actually do not stipulate needing to have three chainrings - any crank that allows a 30-tooth or smaller inner ring and is designed for a road bike fits the criteria, and I list three double cranks that satisfy this (by Specialized, Lightning, and Sugino). On my single bike, I'm currently running the Lightning cranks with a 94 mm BCD double setup and 29-46 chainrings, plus 12-30 cassette. However, having such a large jump between rings is not ideal for most people, and there aren't really any regular cranks available with this setup, which is why for most people I recommend just using a triple (including my own wife). Apologies for that index being a little out of date now, I haven't redone it in about 18 months - it doesn't even have the new Campagnolo triple cranks in it.

I'm planning to post some photos of my setup, but I didn't want to post it while we still had the old Gates drive on there because it really didn't quite fit in the outer ring position due to crank arm interference (even after flipping the ring and shaving off 1 mm from the edge). Last week, we finally got the new Gates CenterTrack belt and rings, which fits far better, but it did require quite a bit of playing around with ring spacers before getting it just right. It worked great when riding the bike solo, but I haven't had a chance to test it with my stoker yet. If you use a timing chain instead of the belt, then running it in the outer position of the triple instead of the large ring shouldn't cause any trouble at all.

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Old 12-06-12, 09:08 PM   #11
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Chris, what do you think about an even larger jump between the two chainrings? I'm running some calcs and I think a 28-48 combined with an 11-28 cassette would be great gearing. 20 teeth is a big jump though. I currently run a 54-39-24, so my biggest jump is 17 and it works OK but a bit slow to shift. Really looking forward to those pictures.
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Old 12-07-12, 12:50 AM   #12
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46 teeth is the biggest chain ring that I know of that is designed for the middle position of a triple (and so has the bolt recesses on the correct side and has shifting ramps), it's made by TA Specialites in black or silver (I think Peter White would be the best US-based source). When choosing combinations, keep in mind that it is the ratio of the two sizes that is more important than the tooth count difference. The most extreme I've run is a 28-46 combo on my single bike, but that is really extreme, and I wouldn't use it on a tandem, where it is harder to coordinate easing off the pedaling power when shifting. With any of these combo's, make sure that you have a chain retention device inside the inner ring - the N-Gear Jump Stop is my favorite.
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Old 12-07-12, 08:32 AM   #13
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Here is a possible option. These come in only one crank length and you must buy their rings but I think they will do what bikeinxs wants to do.

http://www.compasscycle.com/cranks_rh_tandem.html
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Old 12-08-12, 06:25 PM   #14
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I've posted details of our setup in this post on the Gates CenterTrack. Here is the shot of the thing that is important to the discussion in this thread - the chainline:
Attached Images
File Type: jpg Tandem_Drivetrain1.JPG (75.6 KB, 23 views)
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