Recumbents and comfort

Most recumbent ('bent) owners learned to ride on DFs or 'diamond frames.' A DF is the standard road bike like the ones ridden in the Tour de France.

Some cyclists bought a recumbent because they believed it would be faster. Some because they wanted to try something different and some because they were suffering pain when riding a DF. Many bent owners also own and ride DFs.
Some bent owners are a bit evangelistic about recumbents. They don't consider DFs have any redeeming features at all and their most likely comment is that "DFs are painful to ride."

Leaving aside any arguments about speed or visibility, is a recumbent much more comfortable than a DF?

Let's start with the three wheeled bents - the trikes. You don't have to balance them and you sit in a cushioned chair. They can be very comfortable. Even the hard shell seats on alloy racing trikes are supportive and comfortable. In terms of the gold standard for comfort, trikes have it.

Next on the comfort scale are the recumbents with fairly upright seats. The most common design is the short wheel based recumbent like the P-38, V-Rex and Maxarya but there are some low racers with high angle seats. The front wheel drive Toxy is one. Zockra is another. Long wheel base recumbents like the Gold Rush also have upright seats.

As the seat angle drops below about 28 degrees, the comfort starts to suffer in one specific area. In order to see forward the rider on a low angle seat has to raise his head. His position can be assisted by a seat that has 'recurve' - the upper part of the seat is at a higher angle. The rider can also utilise a neck rest or a head rest, but on bumpy roads the vibration may be unpleasant.

Any bike where you sit on a cushioned chair and face forward has to be more comfortable than any DF. But DF riders say they're comfortable; how can that be?

On a properly fitted racing DF, the riders weight is evenly balanced on his or her seat, pedals and wrists. Riders become accustomed to the pressure from the saddle and don't notice discomfort unless they ride long distances. They are relatively 'comfortable.'

This is at the expense of forward vision. To see more than a few feet in front of their wheel, a DF rider has to raise the head, which puts the neck under strain - just as a low seat angle does on a recumbent. Of course, the 'comfort' DFs like the Electra Townie and the RANS 'crank forward' bikes keep the riders back almost vertical, so they have good forward vision.

Anyone that has ridden both DFs and recumbents will almost certainly admit that most recumbents are more comfortable than DF road bikes. But both recumbents and DFs can become uncomfortable as you change the riders positions to obtain a more aerodynamic position.

Safety - How safe are recumbents and can I make them safer?

Cycling is safer than doing no exercise and in terms of emergency room visits, statistically safer than playing basketball (National Safety Council of America.)

www.bicyclinglife.com/SafetySkills/SafetyQuiz.htm

Comparing cycling to driving, which is safer?

France: An hour of cycling is safer than an hour of driving.
Germany: cycling is about equal in safety, per hour.
Sweden: cycling is about equal in safety.
Switzerland: cycling is about equal in safety.
Netherlands: cycling is about equal in safety.
Australia: cycling is slightly more dangerous than driving.
USA: cycling is safer than driving, per hour.
Britain: cycling is more dangerous.

We don't have statistics comparing recumbents with road bikes. In a study of the members of UKs, CTC, a cyclist was killed every 15,000 person-years of cycling.
So the perception of cycling being 'dangerous' doesn't hold up - generally speaking the danger is about the same as for driving a car but cycling provides health benefits that extend life.

Anecdotally it seems that there are two main types of cycling fatality. Cyclists are hit from behind, or run over at intersections.

With regard to rear impacts, you can take the following precautions.

NEVER ride into a setting sun if you have another option.
If you are forced to ride into a setting sun, ride on the footpath, even if illegal.
Fit and use a mirror and if it's obvious that the vehicle approaching from the rear may be a danger, get off the road immediately.

NEVER RIDE ON THE ROAD INTO A SETTING SUN IF IT'S RAINING - NO - NOT EVER.
Likewise, don't ride at night when it's raining if you have any other option and it almost goes without saying that you must have bright lights.

Staying safe at intersections.

Don't try to hide in the gutter, you may not be seen. Use the bike lane if it's safe and utilise the 'bike boxes' at traffic lights.
If you have a mirror (and you really should) 'take the lane' as you approach an intersection. Cars will see you if you're directly in front.

DO NOT PULL OUT INTO AN INTERSECTION BECAUSE YOU HAVE 'RIGHT OF WAY.' Wait until you can see clearly both ways and if there is traffic that should be giving way, try to make eye contact.

Trikes seem to be over represented in fatalities at intersections. This may be because they are low and can be hidden by other traffic in a term that I call "masking." If you're riding a low racer or trike, you're completely hidden by the traffic around you, except the vehicle behind you.

Ride as if you're invisible and you'll ride much safer.

Flex and why it's bad

The P-38 has virtually no flex in the crank tube under pedal load. The crank tube is braced back to the stem and with four frame sizes, riders can pick a size that more nearly matches their leg length.
This is, in my opinion, one of the reasons why it has a reputation of a good climber. The other reason it climbs well is the closed rider position and moderately high bottom bracket.

Whenever flex is raised as an issue on Forums, someone will claim that, as the flexed frame returns to it's neutral position, the power lost is returned. This is not correct. When the bottom bracket (BB) is forced down and sideways on recumbents with frame flex, it 'pulls' the chain a microscopic amount. But when the BB rises again, the power side of the chain is slackened. When a BB flexes under pedal load, power is lost.

Some recumbents have as much as 25 mm (1 inch) of flex under static load. My experience and brief tests with a trike before and after a BB brace was fitted, suggest that flex can make a trike 10% slower on average - most of the speed lost is in climbing where the most pressure is applied to the pedals.

Some of the latest carbon frames have very little flex at the BB. They are made with a deep rectangular section crank tube. It's no surprise to me that they climb well.

Riders who are short in stature and who have a high cadence may not notice much power loss form BB flex. Likewise, the very rare riders that have a perfectly smooth pedalling action, with power being applied equally around the pedal stroke, will hold a frame in it's stressed position and no power will be lost.

I have a slow cadence and a very long x-seam (distance from back of seat to pedals.)
As a result crank tubes on my bents are extended a long way forward and unless they're braced like the P-38, they flex a lot.

Lack of flex in the P-38 BB is one of the reasons; probably the main reason, that it climbs faster than many recumbent designs.

There must be some faults with the design?

There are a couple of minor design issues. Whether you call them faults is a matter of definition.

Cut seat mesh
Unless the seat mesh is stretched tight and if the seat is tilted back, the seat mesh can come into contact with the rear wheel. This burns a cut in the mesh.

The fix is very simple. Get rid of the factory seat lacing and replace with cable (zip) ties. Using zip ties gives control over the mesh tension - you can have a very tight back mesh and a slightly softer seat mesh.

To completely eliminate any chance of mesh to seat contact, fit a plastic fender (mudguard) over the rear wheel. The clip on DF variety work well. Cut off the clip at the bottom that normally clips over the DF seat tube. Drill a couple of holes in the plastic and zip tie the fender to the frame cross member in front of the rear wheel. At the top, throw away the sliding metal clamp, drill another couple of holes and zip tie the fender under the crossbar between the seat tubes.

Front brake nipple
Depending on the model and year, the P-38 may be fitted with a caliper brake behind the front fork. If you allow the fork/front wheel to rotate too far to the left, the nipple adjuster on the brake arm will contact the lower frame tube. This may snap off the adjuster thread. Everything still works but it's annoying.

The wheel would never rotate far enough when riding the bike. I've had it happen when placing the bike on a rack. The steering has flopped over far enough to cause the brake to foul the frame.

I haven't had any other issues.

Is the P-38 expensive?

Yes. It's a low production volume, triangulated steel frame, hand welded in America.
It's a classic; one of the original racing recumbents and still capable of seeing off the opposition.

Do you want one or not?

Is the P-38 'Fast?' Let's see some figures

Here are some comparison figures for the roll down performances of the recumbents I've tested. The test consisted of zeroing the max field on my Garmin Edge 305 and allowing the bikes to roll down my test location hill from a marked point. At the bottom, I recorded the maximum speed. For each test I performed three rolls, then averaged them. I added weight to bikes lighter than the P-38 - which was all of them!
The location is sheltered by trees and concurrent roll downs typically varied only in the decimals.

P-38 no fairings but with HED front wheel and covered rear wheel. 55.8 kph 33.5 mph
Above is the 'bare' P-38 and you can deduct at least 1.6 kph for the aero wheels
The estimate (but an accurate estimate) for a 'stock' P-38 is 54.2 kph 32.5 mph

P-38 Windwrap GX front, Aerotrunk rear and aero wheels as above 60.2 kph 36 mph
Optima Raptor carbon low racer with clone M5 tailbox 58.4 kph 35 mph
Performer FWD low racer 'bare' 59.7 kph 36 mph

Typical DF road bikes with riders in tuck report maximum speeds about 5 kph 3 mph slower being 51 kph.

I can't find the figures for the High Racer but I recall it was slower on roll down than the bare P-38.

You may be surprised at how close the three designs are - the speed spread is approximately 2 kph between the three recumbents in their different aero configurations.

Yes - the low racers are faster than a bare P-38 by about 4 kph. But that's at a closing speed of 60 kph which is not your typical cruising speed.

A P-38 with aero wheels and an aerotrunk tail box is as fast as the bare low racers.

Yes, I hear what you're saying. The low racers with a well designed tail box and aero wheels will be faster (in aero terms) than a similarly equipped P-38.

BUT because the P-38 climbs better, in anything but dead flat terrain, the P-38 will be as fast or more likely faster.

How good is that for a 23 year old design?

Subjective or Objective - Which evaluations can be trusted?

If we care; and many don't of course, how do we evaluate any product or system. In my case I have been seeking a fast bike so that I can ride with local DF riders and keep up!

Here are some typical statements found on bent Forums.

My bent is really fast :Subjective
I averaged 35 kph for an hour this morning :Objective
The P-38 climbs really well :Subjective
With a tailbox fitted, my bent is faster :Subjective
With a tailbox my bent reached a higher measured speed than without :Objective

You can generally trust objective statements - those that include measurements - more than subjective statements. As in all things it's not totally clear cut, because measurements may not be reliable and there's always a limit to accuracy. Likewise, subjective statements can be surprisingly accurate if they come from enough people.

I chose my P-38 based on the subjective assessments of past and present P-38 owners and of Bentrider forum members.

I confirmed the efficiency by direct measured comparisons with the other bikes I've owned.