Re: [rootsradicals] Re: specialized Crosstrail and Xtracycle -- tire question
- On 2008-12-12, at 9:57 PM, Rick Pickett wrote:
>If you run a 2+ inch rear wheel (2.35 big Apple, or 2.5 Maxxis
> I'd second the 26" route, the loss of 1.5" of diameter isn't going
> to be that noticeable and you can get a stouter rear wheel.
Hookworm) there is effectively no loss of diameter.
Bigger tires is better tires. I started out on a 700c, went to 26 x
Fat, and switch back to the 700c each winter for the snow tires. The
fatter tires are just plain better, in every single way except weight
of the tire itself (and if that much weight makes a difference to you,
then you have the wrong bike :-).
Different sized wheels/tires on front and rear is not a big issue. The brakes need to fit. The front tire diameter needs to match up with the rake and trail of the frame/fork combo to keep the steering geometry close to happy, there are a few variables here that work with each other but it's not magic. You'll need to carry more junk to repair flats with. Your fenders might not fit so well.Bigger tires are indeed better in this situation. But why? Because you can run a bigger tire at a lower pressure for a given bike/rider/load. As noted, with the smaller tire at lower pressure you'll feel some give on a bump, that will turn into a flat at some inopportune time. Or maybe a bad experience in a corner. The give part is good, it is like having a suspension system. Unfortunately give turns into pinch flats or rolled tires all too soon with skinny tires.Larger tires can be run at lower pressures, resulting in a much more comfortable ride and more stable handling in rough patches. The rolling resistance might go up a measurable amount. Acceleration will also be negatively impacted due to the greater rotating mass. But comfort trumps speed here.I'm not aware of an hour record having been established for cargo bikes, although it might be a weird sort of fun. I can see a bunch of us with Big Dummys, fixed gears, and skin suits traveling to the track at Mexico City...how many cases of beer would be required?The right answer, for me anyway, is to run a fairly fat tire at the lowest pressure that the roads and loads will allow on my cargo bike. If I were riding a time trial on my carbonium wonderbike the answer would be totally different.Fat Rob
- --- In email@example.com, "lhogue46" <lhogue1@...> wrote:
> I got my Xtracycle last weekend, and my bike shop built it up, but
> ran into a problem with the tire.
> The bike I started out with is a new Specialized Crosstrail, which
> comes with 700x45 tires. The bike shop found that there wasn't
> sufficient clearance for the existing rear tire. I didn't ask where
> the clearance problem was, but looking at it after they installed
> it looks like the problem was with the front cross bar on thethe
> chainstays. They found that a 700x32 tire would fit fine (they used
> an Armadillo, by the way).
> Has anyone else run into a similar problem with a 700c Xtracycle?
> I'm a bit concerned about putting such a skinny tire on a bike I'm
> going to carry loads with, especially after reading the Roots
> Radicals discussions. Today a friend of mine was trying it with
> another friend riding on the back and the tire was squashing. (have
> to admit I don't have a high pressure guage so I couldn't check how
> much air was in it, but it feel pretty firm with a hand test).
> So my friend suggested I could put a 26" wheel on the rear and go
> back to the fatter tire. He said lots of mountain bikes have
> different sized front and back tires. Is this completely crazy?
> Or does anyone else have any experience with a 32c tire on a 700c X?
> I'm glad to say that Steve at UC Cyclery in San Diego seemed really
> knowledgeable about Xtracycles. Another component that he suggested
> to swap out was the front fork. The Crosstrail has suspension on
> front fork, but you can lock it in place. He loaded the bike upwith
> 85 lbs for a test ride and said the fork felt squirrelly andwouldn't
> suggest going above that with this fork. He suggested that I couldas
> switch to a rigid fork of the same height as the existing fork, so
> not to change the geometry. My typical shopping trip comes in at 85thinking
> to 105 pounds (depending on whether we need dog food) so I'm
> about doing this.~~~I read the various replies to your query thus far and several
> Overall I'm happy with the X, though I haven't had a chance to log
> many miles yet. I guess the Crosstrail just wasn't the best bike to
> add an X to (at least expense-wise). But Steve thought that once we
> get these changes made, it will be a pretty bomber ride. Looking
> forward to doing some shopping with it!
suggest converting your rear 700c wheel to a 26" yet they failed to
mention the prospect of losing clearance between the tarmac and your
crank arm. You may have a higher BB height that will let you get
away with this scheme. My Xcycle uses a 58 cm Surly LHT as the donor
bike and although I could fit a 26" rear wheel in the rear triangle
designed for a 700c wheel, the crank arm ends would be too close to
the tarmac to make it feasible. Again, you may have a higher BB so
it might not be an issue but with my touring frame...it wont work
FWIW I'm running Conti Contact tires (700 X 37) and have had no
problems with heavy loads on my X. Inflation pressure is marked on
the sidewall at 85 PSI so I keep them aired up to that figure,
especially before putting any significant weight on the back
If I were you I would run the tire you now have on the rear and keep
it aired up to the suggested limit, which you said is 100 PSI. I
wouldn't run much lower air pressure if even 10% lower
In regards to owning a high pressure guage, I'd suggest buying a
cheapie $20 (or thereabouts) floor pump. It will have an accurate
guage mounted on the barrel. it's considered good practice to check
your air pressure and correct every day you ride but IMO, I would run
your rear tire to the max prerssure with a heavy load.
Underinflation will result in pinch flats