10.24.2009

Trail, Front Loads, Practical Cycling Design

edited: 4-26-10; i don't really feel too strongly about this any longer, riding a wide range of bicycles with mixed trail--there's a lot that goes into geometry and so while this might be an interesting place to start for many I prefer to leave it up to you to experiment than listen to my opinion.

The above photos are from today's weekly run to the berkeley bowl. Emily's backpack is in front, doing gentle item duty with some eggs/pb/spinach, it's a good size comparison to the very old kremlin bag I use for hauling many-itemed loads on my cetma rack. This setup does a wonderful job navigating the several miles of urban traffic between the berkeley bowl and our house, and saves my back from what can sometimes reach toward triple digit loads. This setup has proven able to carry people, too, if you were wondering. The second photo shows everything carried (which was about half capacity). You can make out a 3L bottle of olive oil in there (and a pomelo--the 'king' of grapefruits).

Low trail geometry is one standard for safely and efficiently moving significant front loads. Kogswell is one of many small makers who are answering the call by using classic french porteur design from the 50s, with 39mm of trail for nominal wheel flop. This bike gives amazingly good handling with huge front loads (my atlantis, for comparison, has the british classic 60+mm of trail and is designed for rear loads--it still works quite well with a front boxy bag, however, so don't get too hung about all this trail business and focus on riding).

Want to try out a low trail bicycle? Check out this post for some options, new and used (of note, Trek made low trail bikes up until 1984).


French porteur racing (also, nice plump tires eat up the cobbles improving speed and handling). A 1952 Alex Singer.


4 comments:

Jim G said...

1) Good stuff.

2) Joel's Sycip is not low trail, but was the forerunner of modern day cargo rack usage.

3) Thanks for the link!

4) Another modern low-trail cargo option: Specalized's Globe Live series. ~40mm trail. Yep!

erik said...

Thanks--this is my brief foray into the realm of trying to write with clarity about some finer points, and I'm glad it has your approval as I certainly am still learning.

I've learned much from your writing!

Sami said...

I am only 5'8" and find that I am confronted with a lot of toe overlap on 700c bikes with low rake and steep head tube angles. This problem is further exacerbated when using fatter tires (>25c), which seem like a prerequisite for any hauling bike. Granted, one can find toeclips with shorter depth, but it is not easy and results in a lot of trial and error (MKS-med clips are good). My overall point is that it seems very hard to have a front loaded rack on a 700c style frame with a high HT angle + low rake and no toe-overlap when you ride a smallish frame. Perhaps anyone riding a 52cm frame (as I am) or less will be better served by a rear rack. Anyone have thoughts on this?

Finally, it seems worthwhile to mention that Long Haul Trucker uses 26" wheels, thus obviating a lot of the concern about toe overlap and fender clearance. However,is the 71 degree HT angle and 45 mm of rake on the LHT too much for good handling with a loaded porteur rack?

erik said...

Thanks for posting Sami, I'll do my best to answer your questions. First, let me say that bicycle anything is driven by what works best for the cyclist -- you. Your mileage my vary, and that's to be expected. I prefer 60-70mm trail until weight gets above about 15 pounds in a porteur/randonneur position, then it gets rougher. I don't think trail matters much for pannier setups--you get used to what works best for you otherwise and there's not much change. I used a crosscheck with lowrider front panniers once upon a time, it worked splendidly.

So, onto your specific concerns about TCO.

I'm unsure about the best method for avoiding toeclip overlap. I ride a 64-66, and my partner 56-58--neither of us worry about this too much in our experience. She's 5'9". Depending on your PBH/torso lengths, you might try a bit larger frame (though again, you know what works or not better than me) in order to better stretch up and out instead of down and in? That would help right off between most bicycles of the same model, given similar geometry scales, due to a longer TT (and would be regardless of trail/HT angle).

HT angle and fork rake variances make your next question hard to answer for me concisely or without doing some geometry analyzing. I've found that low trail, high angle bikes give me more toe clearance, but I can't generalize much more than that (I'd have to sit down and do the math, which, since I don't have TCO I've never thought to do). Google around, I know others are deep into such considerations and have done this. There are many a low trail bicycle geometry guru about--perhaps a question to query the BOB listserv about, or otherwise? Vintage Bicycle Quarterly has much writing about these concerns, as well.

Hope that helps!