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Tuesday, May 1, 2018

High performance U-bars, stem and riser for recumbents.

Let me make a few prefaces first. If you are looking for handlebars that are adjustable in length and width and grip flare angle, consider Schlitter J-bars as seen on the Schlitter Encore, available from Jacquie and John Schitter at Schlitter Bike. These bars a very easily folded for a travel bike too. Do keep in mind that grip flare angle will be a function of width. If you just want bars with adjustable length, consider Rans 3Way Bars, available from Jerrell Nichols and team at RANS. Both these bars make great sizing tools to figure out what size custom bar you need too. You can even use the RANS bar with my suggested stem and riser below. If you are very concerned with weight, both bars are pretty light. both are easier to shop for and set up as well. I believe many riders would enjoy their riding more with a focus on bike fit and handling though. 

The above are simpler to set up than what I describe below. But keep in mind, you can have a shop do this for you too. 

This configuration has a range of applicability with regards to boom length. If you have a boom of 12.5" (current Medium Bacchetta), you can also use the current Bacchetta 3 Piece Riser with a 120-140mm off the shelf stem to get your bars maximally low. It will not be adjustable for reach, only height, but it will weigh less. The cost will be the same or more depending on how much you spend on the off the shelf stem. If your boom is even shorter, just use a shorter off the shelf stem. On the other end of the spectrum the stem angle of +35 degrees means that as the boom get longer than about 17", and the frame deviates from a stick, you may not be able to get the bars low enough with this set up. I think a Pelso Brevet L will work. If you are choosing a geometry for a new Carbent, this is something to keep in mind as well. Reducing effective tiller is always good, until you need a $1000 stem to locate your bars!

This will not work on Metabikes, as there is too much effective S in the frame, and the boom is too long. 

If you have great visibility over the bars, your arms are relaxed when you can reach the brake and shift levers, your hands are in line with your shoulder, your bars and short and stiff enough, and you are happy with your seat recline, this is not something that will make a big improvement to your riding experience. In fact, if you are more upright, you may not want maximally low bars, as it will put your hands well below your shoulders. 

This combination of parts suggested below will achieve significantly greater rigidity than the bars currently used on many recumbents, including the options above, and allow you to recline as far as you wish and still have relaxed arms, and allow you to get the bars maximally low for the best forward vision without hitting your feet. The key is using 31.8mm tubing rather than 22.2mm for the bars, and an adjustable length stem. Many riders are looking through their bars, and reaching too far to hold onto them as they recline more. Sadly to recline more you have to use a shorter stem, which means the bars go higher! I have seen many recumbent riders challenged by flex between the hand and the front wheel. On many bikes this flexibility is in the bars, but some stems and forks and frames can be contributors too. This flex causes hand shake at higher speeds and power levels, lack of control during hard cornering, and a general lack of oneness and ease when riding. This becomes a bigger factor on rough roads (or worse yet gravel), technical descents, fast group rides, and even hard solo efforts on smooth ground for some riders. Even the most relaxed and skilled riders can be affected by this. Whats to follow fixes all that, and more. 

Here we go with the pieces!!

First you need a Control Tech Stoker Stem. This will allow you to adjust both the height and the fore-aft position of your bars for maximum forward visibility and without hitting your feet. This stem is not light. It is rigid, and very reliable. It comes in several clamp diameters at both ends. You need the 31.6mm seat post diameter (that goes on your riser), and either the 25.4mm bar clamp diameter (if you are using Bacchetta stock bars or most others), or 31.8mm bar clamp (If you go with custom Power On Cycling bar that I recommend). If you only want to buy this stem once, go for the 31.8 bar clamp as you can shim a 25.4mm bar with Wheels Manufacturing Handlebar Shims. The 31.8mm bar allows you to put your cables inside the bar.  A big shout out to Mark Power, as without his custom bars, we would be a lot more limited! He can make U-bars for Lowracers too.

For length mine is at about 200mm, so the short one is fine. I am on a L frame (14") boom, and 170 cranks. On an M frame (12.5") boom, I would only use this stem if you are a very toe down peddler, or are running 155mm cranks or shorter, or some combination of those, or you are willing cut some length off both stem pieces to get it down to about 145mm with 170mm cranks. Also, bar width at the front has an effect on how long you can run the stem without bumping your foot on the bar in turns. My U bar has some V to it so I can get my bars the lowest possible, and fit it in my car easier. My bar is about 16" wide in front and 19" where my hands are. This is why an adjustable stem is so cool. No matter what your bars, pedaling style, foot size, or crank length, you can get your bars maximally low. 


Here are the dimensions of my bars, and this is what Mark will ask you for as well. 
  1. Handlebar wall thickness (065" recommended for .875" OD  HB's) 31.8mm, 22.2 grip
  2. Outside of HB width at end of horizontal (~18.5", narrow spec Aero)  19"   
  3. Outside of HB width just after aft bend (~17.5", narrow spec Aero)   16"  
  4. Front center of HB's to center of grip zone bend (horizontal HB reach) 10.5"
  5. Grip zone angle (40 degrees Bacchetta stock) 40 degrees
  6. Grip zone length, end of grip zone to center of bend 7"
  7. Grip zone boring requirement and length (if bar ends are used) reamed for Sram/Shimano bar ends. 




You will need to figure out yours based on what you currently use, how much more you want to recline and how much forward extension your current stem has. This should help if you are on a Bacchetta: Dimensions of all Bacchetta Risers/Stems. On any other bike, just measure from the center of the steering axis to the center of the bars, with the tape measure or ruler parallel to the frame tube. You want the bars to be wide enough that you have enough steering room for steep climbs, and corrections in gravel. An inch between you hands and thighs is enough for most. You can add some V to your bars like I have by making the front narrower than the grip area, but you must have clearance for your calves, and if you are bowlegged at all that will be a factor as well. Keep in mind extra clearance for tights or rain pants if needed. 31.8mm bars are not very bendable, so you want to order them right. As a rough guide, if you are on a Bacchetta L frame, your new stem will have about 165mm of reach once you adjust it. Keep in mind that even if you change to a different boom length frame, as long as recline stays the same, your bars do not change, only your stem. Bar dimensions are only a function of your body and its position on the bike. Also, people hold the grips in different spots to get comfy, so you do not have to be accurate to the tenth of an inch on the length of the bars. 

For the riser tube, you need something with an ID of 1 1/8" (28.6mm) that slides snugly down your steerer tube. The wall thickness needs to be 1/16" so the OD is 1 1/4". You can just use an old one piece Bacchetta riser (either reach), or lower section of a Bacchetta 2 or 3 piece stem, and cut off the top, like I did at first:

..or get a piece of carbon tubing from Dana at Bent Up Cycles (cleanly cut and slotted on a water-cooled saw), or Rock West Composites, which I did later. Chuck your BFT, and put a star fangled nut (for aluminum lined steerer tubes) or an expander nut (for full carbon steerers) down the steerer and add a conventional top cap and bolt for headset adjustment.Headset Cap and Bolt

For the riser clamp to the steerer, I first went with Bacchetta dual bolt clamp, which you can see in the pic above. Bacchetta Double Bolt Riser Clamp
Now I use the single bolt clamp they used on their newer 2 and 3 piece stems. Never had a slippage problem and it's lighter and cleaner looking.

Also, since the 31.6mm stem clamp to the riser is actually 0.2mm too small, its good do have a Cal-Van spreader tool to use, rather than twisting a big screwdriver to spread it. 

I don't not see them on Cal-Vans site, but have seen them in auto parts stores recently. I believe they were designed for R&R of springs in automotive drum brakes.

Having put stiffer bars on several personal bikes (Velokraft Nocoms, Bacchettas, and Carbents), I have noticed that it allows me to now feel the next largest source of flex. In the case of the Nocom, it was the fork, and nothing could be done. On the other 2, I was now much more cognizant of the affect of tire pressure and sidewall flex. It also made me wish for a frame with a tapered steerer and a thru-axle fork, just so I could see if it could be even better. 

The only thing I might have done differently on this bike is to make the bar grips and inch longer and the length of the bars a little less, so my hands would be in line with my shoulders with the bars level. 

Contact me at Jim@JBVCoaching if you have any questions, need a fitting, or a coach!


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2 comments:

  1. I tested one yrs ago<<,in an oval. very fast..some say not great for touring...I like the seat as seems perfectly erganomic..visually looks scary as crank/BB seems too high up as angle of boom/main frame lower but likely perfectly in line with heart...all due to the wheels are same size...likely the next best to a conventional style bike...I will read all the blog maybe learn some facts..I am one for as many styles bents as possible if room...I still got the performance thing but I like touring and errands too...I am more versatile...like trikes too..

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  2. I just had an ex client do this, primarily so that he could run his cables inside his bars. :-)

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