Short wheelbase vs Long wheelbase bents

[PaulM]

Last year I rode the hilly Isle of Wight randonnee on a LWB, this year I attempted it on a SWB – and failed. I was expecting the SWB to be easier to balance on the hills but I lost balance on a few occasions when in bottom gear, usually when distracted or in tricky congested situation (lots of bikes, narrow roads, cars coming the other way kind of thing).

Gear ranges: LWB 21.4-106.8”, SWB 20.4-85.6”

The SWB is about 4lbs heavier with its rear suspension. The LWB has the more efficient drive train with no idler and no suspension.

So maybe I was able to maintain a higher speed on the LWB which helped with stability. Second gear on the SWB is 22.9 and that was too high for many of the hills.

My legs felt like lead after a couple of hours so I opted for the shorter route after reaching Alverstone. Maybe racing for the ferry early in the morning had drained me – left the house 10 mins later than planned. Also my asthma this year is causing me problems.

After the ride, on the way home going up the Portsdown Hill (old A3) I managed the whole long climb from Cosham without stopping or losing balance and more than half of that was done in first so I shouldn’t be too hard on myself.

 

[Ming the Merciless]

It takes a while to adjust to the balance points of a SWB bent. Suspension doesn't help with up hills often robbing you of a fair bit of power. The more laid back you are the less power as well. Body to legs angle of about 40-45 degrees is considered optimal for power output. SWB are often more reclined which means your power output, particularly on hills is not so good.

I can manage 20 degrees uphill on SWB but no more. Never ridden LWB but I've heard a few such as Rans Rocket are good uphill.

 

[PaulM]

Yes, riding position affects power output and it's true that for most riders there is less power with a an open position. I've since remembered that the SWB has 150mm cranks vs 165mm on the LWB which gives the LWB a lower gain ratio so probably not much difference in terms of low end gearing between them.

 

[Tigerbiten]

A reasonably good rule of thumb with recumbent bikes is .........

The lower you are and/or the more reclined you are, the harder the bike will be to balance at low speeds but the faster you will be at high.

The LWB bents I've seen tend to have a more upright seat than SWB bents.
So the LWB bent may just be inherently more stable at low speeds than the SWB due to the basic geometry of the seat.

YMMV .............

 

[PaulM]

I have a regular circuit which gives me a chance to compare my performance on my Nazca vs the RANS. The circuit is 16.4 miles with 725 feet of climbing. My best averages so far are 11.9 mph on the RANS and 11.1 mph on the Nazca. Unfortunately I am getting an aching hip on the RANS which is possibly a hip impingement. I shall try laying the seat back a little. In the meantime I have £300 of upgrades to install on the Nazca: an aluminium fork and a conversion to 10 speed. I reckon each will save me around 300g, so price of being weight weanie is about 50p per gramme.

 

[recumbentpanda]

My Nazca Fuego is noticeably faster than my Linear CLWB. But, ironically, I can get the Linear round much tighter corners at slower speeds than the Nazca.

The Linear (old school Iowa built folder) is of course designed as a relaxed tourer with a fairly upright position. The Nazca is set up as a ‘fast tourer’ and is much more laid back. Despite the layback I can get it up steeper hills than the Linear with about the same bottom end gearing.

It’s never just about the bike tho, bike/human is a complex system of feedback loops

 

[Ming the Merciless]

I think the more upright you are the more you can use body English to correct minor wobbles at low speed. The lower your centre of gravity the less time you'll have to respond but will be more stable at speed.