Changing front wheel size - Catrike

[fd3]

My 700 was designed for 349 (16") front wheels, the previous owner switched it to 355 (18").  I'm considering moving up to 406 (20").
Where do I buy wheels from?  Being front disk brakes, how do I ensure that I can just swap the wheels about (switch back if it's an issue) or is this wishful thinking?

[rafletcher]

Disc hubs are much of a muchness, so swapping wheels is trivial.

[LittleWheelsandBig]

Recumbent trikes often have proprietary front hubs, so you may need to get a pair of Catrike front hubs to build up your new wheels. You may prefer to dismantle your existing front wheels and reuse the hubs.

The larger wheels will change ground clearance and front end geometry. The amount of brake steer and steering self-centring is likely to alter. The fatter your new tyres (larger effective wheel diameter), the greater the differences from now.

[Kim]

Disc hubs are much of a muchness, so swapping wheels is trivial.

Not for stub axles they aren't.

[Lightning Phil]

Would this have anything to do with mudguards getting bashed when dropping off kerbs?

[cycleman]

Check whether the larger wheel will effect steering trail 

[fd3]

Would this have anything to do with mudguards getting bashed when dropping off kerbs?

Ummm ... no?

(click to show/hide)

maybe a little

[Kim]

Barakta, through pedestrian-avoidance and general bad planning, had reason to drop (well, gently edge) off a kerb in her ICE the other day.  Neither mudguards nor cruciform made contact, but it was a bit close.  Her skellington wouldn't stand for doing it at any kind of speed, even on a Scorpion or something.

[fd3]

What is this “speed” of which you speak?

[ElyDave]

What is this “speed” of which you speak?

Its what you get on a two wheeled  recumbent
Or an ice VTX, if you aren't worried about spine or fillings

[fd3]

To be fair I have only noticed a marginal decrease in speed from my two wheeler (an SPM though), but a marked reduction in effort.

[ElyDave]

I've always thought (possibly erroneously, VTX excepted) that recumbent tadpoles were inherently a bit slower.  I've not necessarily experienced higher speed on my S40 vs an upwrong, but it's definitely been more relaxed.  My best example being chasing down two roadies working together on the long drag past Islay airport a few years back. I worked at an HR consistent with "normal effort" and consistently gained on them and eventually passed them. 
So Recumbent = better HR at the same speed, or
Recumbent = better speed at the same HR
Either way, we win

[LittleWheelsandBig]

Upright trikes are 10-12% slower than upright bikes according to CTT. I expect the relative speed difference is much the same for recumbent versions.

[fd3]

I've always thought (possibly erroneously, VTX excepted) that recumbent tadpoles were inherently a bit slower.

Well, yes, but when you go from a full suspension midracer to an unsuspended race orientated trike like the Catrike there's not much in it.  Other than comfort and less stress, the Catrike has the advantage of being lower so feeling faster (that and three wheels to hit more bumps makes it feel even faster still).

[Kim]

Upright trikes are 10-12% slower than upright bikes according to CTT. I expect the relative speed difference is much the same for recumbent versions.

My experience of Streetmachine vs ICE Sprint (similar weight, similar tyres, less suspension on the trike) is consistent with this: Basically the same on steep climbs, but the Streetmachine rolls better.

There's a psychological factor where I settle into a lower cruising speed on the trike.  Probably a combination of being lower down and rattled in more directions.

[fd3]

I find I'm faster uphill on the trike - though possibly because I never really mastered the SPM and felt I would crash wobbling uphill, whereas I can just go on the trike.  Also, about 5-10kg I reckon.

[PaulM]

I believe originally Catrike front hubs were either made by Bitex or of the same dimensions as Bitex hubs.

P.S. I think the change might result in rather heavy steering.

[Lightning Phil]

A 5-10kg difference can’t be ignored when going uphill, assuming you can get the same power to the driven wheel on each.

[ElyDave]

Up to about 10% there's not much in it on the S40 vs a trad roadbike (Al frame), but once you get a bit more than that, or it's wet and slippery, the FWD characteristic of the S40 becomes unuseful as you start to get wheelspin and slippage.  You can reduce that with lowering tyre pressure, but there's not a lot of room for fatter, grippier tyres than 28mm.  In the dry I've negotiated 14% or so, with light touring load, but a damp hairpin almost cost me enough momentum to be off and walking.

[Lightning Phil]

Steepest I’ve been up is 20% on the P38 and that’s fine.   I have done a hill start on 17% when foot became un clipped, which is also fine.  I find the ability to get up a hill is very much determined by whether you are still balanced at the speed you are going. Haven’t experienced wheel slip yet but I’m sure going up a steep hill with leaves on a wet winters day would do it.

[ElyDave]

You have  more weight on the drive wheel (not you personally, any rwd)

[Lightning Phil]

Indeed 55% of the weight if balance figures are believed.

[fd3]

You have  more weight on the drive wheel (not you personally, any rwd)

On my cat I found wheelspin on wet leaves in my local park/hill.  It’s the sitting in front of the drive wheel.

[Kim]

You have  more weight on the drive wheel (not you personally, any rwd)

On my cat I found wheelspin on wet leaves in my local park/hill.  It’s the sitting in front of the drive wheel.

Trike vs bike thing.  I rarely get any wheelspin on the Streetmachine, and usually only due to the combination of me sitting upright to get a foot down and gravel or similar.  With its lower gearing and lightly-loaded wheel the ICE trike will suffer horrendous wheelspin if it's vaguely slippery.  I recall barakta and I having an adventure on the Birmingham & Fazeley canal between town and Spaghetti Junction, where I kept having to push her up the 'heritage brick' slopes whenever she failed to attack them with sufficient momentum.  I also hurt my foot in an attempt to apply persuasion to one of the RADAR gates.  We never went that way again.

One advantage to a heavy hub motor in the rear wheel and 12kg of battery on the luggage rack is that it completely eliminates this problem, at the cost of instability when cornering.