559 front, 451 rear - thoughts?

[dennis234]

Has anyone tried putting a 451 rear wheel on a 559 Quest?
I'm thinking this would have the following advantages:
- lower the seat height while still keeping the bigger driving wheel
- increase the trail for more stable/less twitchy handling
- compared to same-size wheel setups, this would raise the crank higher relative to the seat (more aero)

Disadvantages:
- you need to carry 2 spare tubes instead of just 1

 

[John Tolhurst]

Disadvantages (cont)
- greater fork flop for more difficult handling at the critical start up speeds
- slower steering response at other speeds
- slight decrease in weight over the front wheel

 

[dennis234]

John, are you speaking from experience or theory?

 

[dennis234]

i guess no one has really tried this. i might have to be the first then

lowering the rear axle height by 3 inches, i roughly calculated, would result in about 1.5 inches lowering of the seat height from the base 559 setup. and would add 4 degrees more recline to the seatback angle. in another post, the max recline i saw for the Quest was 41 degrees without reversing the seatpost. So with the 451 rear wheel and 559 front, this brings you nicely into Silvio angle of 45 degrees.

there will be a small weight shift towards the back, but this may be too small to be noticeable. the change in wheelbase would be very very small. the seat recline probably will be the main component of the weight shift.

 

[John Tolhurst]

Disadvantages (cont)
- greater fork flop for more difficult handling at the critical start up speeds - experience
- slower steering response at other speeds - experience and theory as taught by Tony Foale
- slight decrease in weight over the front wheel - can be readily calculated due to the rotation back of the body

 

[marshall2389]

I was thinking about trying this the other day! Let us know how it goes.

 

[billyk]

I'm thinking of doing the opposite: putting a 451 front wheel on a 559 Quest 2.

Most of my riding is year-round commuting in rainy Seattle, and I climb a lot of hills (100m+ hill coming home from work every day, including a 1-block stretch of 20% grade). My present recumbent tends to unweight the front wheel on the steep hill, which would be fatal on a Quest (which in my short experience is prone to spinning the front wheel under heavy load anyway).

My reasons:
- Put more weight on the front wheel (more traction uphill)
- Fit a wider, grippier tire for rain traction (with room for fenders)
- slightly more upright riding position
- slightly lower gears for hill-climbing

I see that Nanda H. tried this, at least briefly (see photos near the bottom of http://cruzbike.com/quest-kit).

Nanda - want to comment about the ride characteristics?
John T - Do you have one of your typically well-thought-out reasons why this is or isn't a good idea?

 

[John Tolhurst]

The approach is sound,

The approach is sound, assuming the taller head tube angle gives handling you can accept.

 

[billyk]

Glad to hear that.

Is the handling difference strictly a function of the reduction in trail? Namely that it would make the steering more sensitive? "Twitchy"?

How much will the trail change? (If you can do that off the top of your head). Is the difference likely to be dramatic?

I really know little about this, certainly not enough to be able to judge how big a change it will make without trying it. But I don't want to ruin the handling of the bike through my ignorance. (And I also don't want to spend a lot of money finding that out ... learning is worth a great deal, but asking before making a mistake is cheaper.)

 

[John Tolhurst]

The wheelbase is 1057, so the

The wheelbase is 1057, so the difference in axle height over that distance is the approximately angle that the headtube will move.

So head angle will alter by about tan-1((559-451)/2/1057) = 2.9 degrees.

Trail will reduce by about the same fraction, i.e. (451/2)(tan(2.9)), or 11mm.

Taller head tubes angles always handle better.

http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

 

[billyk]

Thanks for that info, but ...

Thanks for that info. But ...

Isn't there also an effect on trail from reducing the wheel diameter? Namely, increasing the head angle and reducing the wheel size will both contribute to reducing trail.

Using the formula from Wikipedia (http://en.wikipedia.org/wiki/Bicycle_and_motorcycle_geometry), which is:

Trail = (Wheelradius*cos(headangle) - Rake)/sin(headangle)

Guessing that for the standard Quests Rake = 40mm, and Head angle = 73, I get:

a) 225mm radius wheel: Trail = 27.0mm

b) 300mm radius wheel: Trail = 49.9mm

Now, if I simply increase the head angle by 2.9 degrees (say, by raising the back):

c) 225mm radius wheel: Trail = 15.3mm

d) 300mm radius wheel: Trail = 34.1mm

Those a-c or b-d differences are roughly the 11mm you get from back-of-the-envelope.

But if I both reduce the wheel size and increase the head angle, I go from b to c, a reduction of 35mm. If my guessed head angle and rake are correct, that would be about 1/3 the original trail.

1) Am I missing something?
2) Are we now getting to a dramatically-large handling change?
3) What are the head angle and rake of the standard Quest?

Thanks!

 

[John Tolhurst]

Time to do a CAD drawing.

Time to do a CAD drawing.

 

[marshall2389]

Somebody try it!

Isn't there 559 Quest rider out there with access to a 451 rear wheel? Just pop it on and go for a ride!

 

[John Tolhurst]

Trail will reduce from 63mm

Trail will reduce from 63mm to 27mm, according to my drawing:

 

[Romagjack]

I can't imagine tinkering

I can't imagine tinkering with wheel size on the Quest. I love the Quest 2 as is, but can see myself on a 700c (Quest 3 John?) version with all the same equipment as version 2. It would add a little more speed & height. Partial fold is nice but not essential. Love the color, IGH, and disc brakes and current shocks. In other words, a more receational and complete version of the Silvio. I enjoy riding the Quest more than any bike I've had.