More reclined position with higher feet by putting a small wheel /short suspension in the back

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Cruzbike-in-Germany
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Beigetreten: 2 Nov 2010

Hello,

when pushing on the Sofrider I (6ft) did not like the feeling that I pushed at a downwards angle. I once tried a HP Speedmachine and loved its forward push feeling, having no problem with its 30° seat back .
Saturday night I envisioned a smaller rear wheel to rise up my feet on my Sofrider V3 - like the late Valdo's model:
I even ordered a 20" wheel on Saturday night, but woke up on Sunday morning and immediately got the idea to put the 16" front wheel of my HP Spirit - a short LWB recumbent - in the position of my Sofrider's back wheel to get a more reclined position while keeping the good body angle I set up while riding on the home trainer.
So we have - both unused - a SON dynamo and a Magura Julie brake disk there. I inflated the tire to just under 5bars (70psi), that was OK:

Unused Tektro back brakes - I rode cautiously, and the front brake was enough. Keep in mind that I was just position testing on lonely roads well-known to me, never take risk at this!!

A lot of space for the bag:

...and a more reclined position, which I really enjoyed, I only made small adjustments to the leg length:

Well, it does not look fast or sexy, but it felt comfortable and swift, and the feeling that the feet were higher was good!
(I just created a thread in the Ride forum describing the landscape a bit, for those interested in landscape pics)
After cruzing and enjoying myself for 2,5 hours my thighs "told me" to better drive home.
To calculate the angle change: the 16" wheel's radius is about 195mm, the normal 26" wheel's radius is about 315mm, so the back axle sunk by about 120mm. This leads to about 6° more recline - at a wheelbase of 1110mm (taken from the data sheet).
The steeper steering tube angle means you need more force when straightening the steering wheel at the end of a turn, but this was unnoticed with one possible exception: when I tried a slow&tight turn on a 2m wide lane, I did not manage to stay on the tarmac, got into half-high grass and was practically stopped by the uneven ground - the bike fell under me - one possible reason for my failing might be the added force to upright the front due to that steeper angle. But this was extreme.
Today the 20" wheel arrived, and I expect the tube&tire to arrive soon, so I can put the 16" wheel back on the HP Spirit.
To continue the testing at a different angle I also ordered a Quest-style short (125mm) suspension element K261 to modify the suspension length, too - currently the K258 at 165mm. I know it is not the same spring ratio, but they are not expensive (for me) and I am curious how it feels: more reclined, but harder suspension...
My neck accepted the change without problems.
My slight groin pain - just above the hip joints - did not come back until today, although I pushed sometimes. Maybe I should try Q-rings, too, to get rid of this pain...

That one was really Happy Cruzin'

Ernest

P.S. It also worked well on my home trainer today!! I will put some brake (drum / disk) there if I decide to keep a smaller wheel in the back. 
 

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Jeremy S
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Beigetreten: 6 May 2013
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Well it certainly has an

Well it certainly has an interesting look! Thanks for posting the pictures.

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Eric Winn
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Beigetreten: 31 Jul 2012
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Kind of reminds me of one of

Kind of reminds me of one of those compact spares when your normal wheel gets a flat on modern cars with 17 to 20 inch rims. The contrast in size is very eyeball grabbing. No disrespect intended, that is just what first popped in my head.  Although recently it seems the automotive world is regressing back to not having a spare wheel and tire at all - just repair doodads. 

I think I would try a layback seat post for more recline and keep the wheels the same size. This way you have to only worry about one size for spares. The larger wheels will tend to deal a bit better with some road conditions too I suspect.

I've not seen a Sofrider in person that I can recall but if the seat can move back more along with using the layback post for more recline, that should also allow you to raise your BB a bit more too.

-Eric
 

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Cruzbike-in-Germany
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Beigetreten: 2 Nov 2010
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Put a 20" wheel in the back for better looks

Thanks Eric!
Yes you're right, it looks weird. The comparison with those ugly mini spare car wheels is a good one, we have them here, too!
But riding it, I don't have to look at it smiley. Ok more, serious: As I said I ordered a 36 spoke - sounded solid - 20" back wheel with 32mm tire - like the front one - to tackle this. The looks improved in my view, but the pedal push felt more downward again and I didn't like that:

Regarding the seat pan position: yes it can be moved backwards, as it is in the second most forward position currently. But then the knees are likely to touch the bar, they have ~1" clearance now. I will surely have to turn the stem backwards. And I expect the effect to be comparatively small: If you move the crank back 5" - the stem position change will yield maximum this - you might get 2"-3"of that as height gain for the BB. So even if I would use a longer stem, this might come handy for the fine tuning, but will not raise my feet 100mm or more.
Next I will put 40mm shorter shock - in fact the Quest's K261 - in the back, as I wrote. I expect it to come the next days. I might then even go back to the 26" wheel in the back if I pedal nicely forward with it. If so I will surely have to rethink the bag, though...I am happy to have the trainer here to check these changes (and shrink my aerobelly blush).
Well, one could try and calculate a lot more than I do now, but if you sit more reclined, the shock backs down a bit more as your weigh moves to the back, and the preferred BB position will change a bit, too, at least I encountered that. And the whole mod is about the feel. So I hope for it to dial in with the short shock.
Regarding the looks: I think the small wheel will hurt the eye less if the rim was "bladed",as the front wheel, like here:

 

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Beigetreten: 2 Nov 2010
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And here a pic of the current setup in the trainer

My bike at home...

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Eric Winn
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Beigetreten: 31 Jul 2012
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How does your riding position

How does your riding position compare to Charles' in this photo? He is 6 ft 1in. I'm not sure if he has the layback seatpost on this photo or not but it looks like with your shock tweaks and a layback seatpost you could get close to what you are trying to achieve.

-Eric
 

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cplager
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Beigetreten: 22 Jan 2012
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That picture is with a

That picture is with a straight seat post. With a layback seatpost, you can get a much lower angle.

What you can't easily get is making the bottom bracket higher.

My thoughts on the mod:

+: able to raise bottom bracket.

-: changing steering angles.

It may very well be the case that the steering isn't affected much, so it might be a win...

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yakmurph
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Beigetreten: 6 Mar 2008
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Raised Bottom Bracket

The best way to raise the bottom bracket is to -raise the bottom bracket.

The best way to get a lower seat angle is to lower the seat.

The best....
Anyway, keeping things simple is harder to do than it looks, isn't it!


This is what my bike looked like before I quit posting photos.
Now, the seat is faired, the headrest is complete and the chainstays are more robust.

Compared with a stock Sofrider, my bike is a rocketship.

If you look closely at the seat I built, you'll see that the seat pan is about as far forward as you can get
and about as low as possible.
It fits my back perfectly because I molded it to fit.

For me, your small diameter rear wheel does a few bad things to the ride:

-the steering gets very slack which makes the front end very floppy at low speed;
-the ear (cochlea) gets dangerously close to being located behind the axle of the rear wheel.
  That's something I personally do not like... makes me unstable.

Like you, I really prefer a higher bottom bracket!

Ride safe,

-Steve

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Handling is (mostly) not about seat angle

As usual, Yakmurph hits the main point:

Head tube angle is key to bicycle geometry, and changing it - even slightly - makes a big difference.

In particular, decreasing the head tube angle increases the trail, which tends to make the bike more stable (tends to center the front wheel), but also makes "fork flop" more of a factor (handlebars tend to oversteer in response to rider input).

See the Wikipedia article http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry

and especially

http://www.adventurecycling.org/default/assets/resources/20140601_Mechan...

and John Tolhurst's comments in several places on this forum, including

http://cruzbike.com/first-riding-impressions

The relation between head angle and rake (fork offset) is critical to handling, with small changes (few degrees) making the bike easy or hard to ride, or even dangerous. Fork flop means that when you turn the handlebars, the bike CoG goes down, thus tending to increase the turning. A 6-degree change is *huge* in this context.

This is probably why you commented that straightening after a low-speed turn required more force.

The changes you notice and like are probably not primarily due to the seat/BB height difference but because of these fundamental changes to the steering geometry. Maybe they are good for your style of riding, but there will be reverberating consequences.

The bottom line is that bicycle designers balance these apparently-fine distinctions very carefully, and we should also.

Billy K

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Kavman
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Beigetreten: 16 Aug 2013
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yakmurph's Sofrider

I'm enjoying this thread.  But, yakmurph, would you be able to start a new thread with a picture of your Sofrider as it looks now?

Thanks,

Kevin

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cplager
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Beigetreten: 22 Jan 2012
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+1 to Kevin's request for

+1 to Kevin's request for pictures!

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yakmurph
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The 'YakRider'

My modded Sofrider lives on the trainer, currently...
and I'm sitting on my more upright fibreglass seat,
not the low seat in the above picture.
Makes it more comfortable to read-and-'ride.'

My new carbon fibre MBB midracer kitted out with a nice SRAM
?powertrain is still being built and it is exceeding my wildest expectations.

Pictures?
Sorry.

No pictures now, but maybe a snap or two of my completed
CF midracer will show up next Summer.

If Cruzbike ever comes out with CF framed Silvios and Vendettas,
you'll want to own one.

----

Ernest,
Your beautiful blue Sofrider is a terrific bike and
I personally love the way it looks with the tiny rear wheel on it.

-Steve

 

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If Cruzbike ever comes out

If Cruzbike ever comes out with CF framed Silvios and Vendettas,
you'll want to own one.

Indeed.