Touring - Why the wide disparity in trail of touring bikes

In comparing the trail of various touring bikes I have noticed they vary widely in the amount of trail based on the steering geometry. The difference in trail also means there is a great difference in the amount of wheel flop. Isn't there any agreement on what amount of trail provides for the best handling when loaded and with a front load being carried in low riders?

You have obviously got some numbers, but for the most part I have seen73/45. There are some lower steering angles, and that would change a lot, since the forks seem to be made to the same numbers.

Thanks MassiveD. Trucker Deluxe for example is 71/45. You answered my question though; I was just wondering about what is considered the accepted norm.

It has more to do with company's philosophy on weight distribution of the riders. In general, road bike geo. is designed to be 40Front 60rear ratio but touring bikes' long chainstays messes up the weight distribution and the position of the riders. Therefore, they increase the front centre by slacker head angle and more fork rake. Hence the 18wheeler wheelbase.

Thanks linus. I just picked up a bike to add to my collection that has 48.5 cm chain stays, but it only has a 71/45 HT angle/fork offset and I was comparing it to many other bikes to try and figure this all out. Steering geometry is actually identical to the Trucker Deluxe. I found the trail computes to being identical or close to several other very good bikes, depending on tire width. The seat tube on the bike I acquired is also very slack at 71.5 degrees. May not be a lively ride, but will sure be stable when descending.

No, different builders have different ideas./.

components are mass produced, bike frames to mount them on
can be made by an individual.

then there is wheel size .. and contact patch size, of chosen tire.

but I don't see trail stated.. only implied .. ['71/45']

Trail, that is the distance laid out on the ground plane. in MM.

measure that and get back..

front loads, like the Porteur's bikes, shuttling Parisian newspaper bundles
to the Sellers stands from the Printer.

have different needs than someone wanting to look at the scenery on a stable bike
that does not need their full attention.

Thanks fietsbob, that makes sense. The bike in question is an old 26" wheeled mtn bike. I made a spread sheet comparing the trail to several other bikes - some with 26" wheels, some with 650b, and some with 700c. I also compared different size tires for each. The bike I bought has quite a lot of trail, it ranges from 67 mm with 1.9" tires to 71 mm with 2.35" tires. Mechanical trail shows a little less for each. The bike will probably be fine for commuting/townie purposes and touring as described by your last sentence, and that is what I bought it for.

Perhaps low trail is more important for Porteur's carrying heavy loads up high? My other road touring bikes have very low trail and seem stable and comfortable to "look at the scenery." Guess I will see how this one rides when it arrives in a few days.

fietsbob, I did not measure the trail but used the online trail calculator here (http://yojimg.net/bike/web_tools/trailcalc.php) to compare different bikes based on their head tube angle, fork offset/rake, and different tire widths. Based on tire width, the trail ranges from 62 mm to 71 mm for the bike I got. Seems like a lot to me, but it compares favorably to some other good bikes like the Atlantis, A. Homer Hilson, Hunqapilar, SOMA San Marco, LHT Deluxe; even the Bridgestone XO-1 if I run 35 mm tires. The bike in question is an old 1983 Trek 850 that is on its way to me.

I have wanted a 26" wheeled bike to make into an all-around/townie/tourer and the Trek is what I got.