Messing with ideas for a “porteur” bike. Is shortish stem/longish TT and low trail just about all there is to it? I don’t have much experience with loaded front racks, so any insights you can provide would be helpful.
Have fun with this one. Probably the most informative thing I found on the internet as far as touring geometry/trail/front-loaded bikes go when I was obsessed with geometry last winter.
you should try frameforums or whatever it is.
i’ve yet to ride a low trail bike so i can’t really comment.
i can say going from 58mm trail to 50mm trail is pretty noticeable (unloaded road bikes).
[quote=cookietruck]you should try frameforums or whatever it is.
[/quote]
That place is terrible.
[quote=]This is unpleasant in my experience with my 2.2" trail long
wheelbase 73/73 degree race bike.[/quote]
I can attest to this. My 73/73/45mm rake bike sucks with the tiniest load on the handlebars. Has about 58mm of trail. Also, are we talking about ground trail or mechanical trail?
http://www.pvdwiki.com/index.php?title=Mechanical_Trail
I’ve read tons of info on this topic and haven’t come to any sort of really good conclusions.
73/45mm with 28mm tire is ~56mm trail.
73/43mm with 28mm tire is ~59mm trail.
i’ve read lots on the subject too and haven’t really come to any good conclusions. just accept that lower trail is better for front load.
size and placement of load probably matters alot too.
wish i could build frames. i would build something around 73/73 with maybe a 43.5mm chainstay and then build a few forks for it. ride around with different loads and actually feel what the differences are.
yo zombie did you ask this in the frame builder mailing list?
Nope.
Nope.[/quote]
guy was using a 35cm 700 and they suggested wider bars and a 30cm 650, this was for a tandem though. I didn’t read it when i first saw it.
As the handlebars turn, the front end drops slightly and gravity pulls the bars around on their own. I assume that number they put on wheel flop is the amount that the front end drops. But I’ve never seen it quantified before. BTW, this apparently has an effect at all speeds even though it is more pronounced at low speed.
Zombie, Volume 3, Number 3 of Bicycle Quarterly magazine has a good article on front end geometry and compares some classic and modern randonneur and camping bikes. Back issues are available: http://www.vintagebicyclepress.com/contents.html
EDIT: Volume 5, Number 3 also has a number of excellent articles on porteur bikes. And Vol 5, No 2 has a review of the Kogswell P/R in inimitable Jan Heine style.
I gotta say, my Kogswell P/R handles better with something on the front than it does empty. It’s kind of uncanny.
that’s why i got a bike that was designed to handle a rear load instead of front load. didn’t want weird handling with no weight on front.
I mean, it handles fine unloaded. But you can put 40 lbs on the front rack and not even know it’s there (until you’re stopped at a light and and have to fight to straighten the wheel).
what you just said but medium trail.
As the handlebars turn, the front end drops slightly and gravity pulls the bars around on their own. I assume that number they put on wheel flop is the amount that the front end drops. But I’ve never seen it quantified before. BTW, this apparently has an effect at all speeds even though it is more pronounced at low speed.[/quote]
I understand the concept. It’s the quantitative measurement that I don’t get. 14mm of what?
As the handlebars turn, the front end drops slightly and gravity pulls the bars around on their own. I assume that number they put on wheel flop is the amount that the front end drops. But I’ve never seen it quantified before. BTW, this apparently has an effect at all speeds even though it is more pronounced at low speed.[/quote]
I understand the concept. It’s the quantitative measurement that I don’t get. 14mm of what?[/quote]
looks like dave kirk doesn’t even know…
[quote=dave kirk]Not sure what factor “F” is but wheel flop is caused by having an inappropriate amount of trail.
Dave[/quote]
Bumping 'cos I hope Fred could have something more to say about this:
[quote=blasdelf] [quote=lukasz]
Can someone get into the geometry needed for this? Basically a steep head angle with a high rake fork to compensate? Can your average 73 degree headtube, 28mm tire Audax bike get away with a small front load?[/quote]
Yes, on a 73 HTA bike even with a normal 45mm offset fork you can get away with a small front load (less than a u-lock or full waterbottle)
On that same bike with a custom 65mm offset fork to get low trail, the weight capacity isn’t limited by the handling
On most tiny bikes with silly slack HTAs instead of small wheels, or normal CX bikes with 71-72 HTAs, shit gets maladaptive real quick – do not recommend
There is another elusive sweet spot in the 80mm+ trail range on 90s MTBs that shouldn’t work (it’s extra super floppy) but somehow feels good man at least under 15mph. Still haven’t figured out what the parameters are to get it on purpose.
[/quote]
As the handlebars turn, the front end drops slightly and gravity pulls the bars around on their own. I assume that number they put on wheel flop is the amount that the front end drops. But I’ve never seen it quantified before. BTW, this apparently has an effect at all speeds even though it is more pronounced at low speed.[/quote]
I understand the concept. It’s the quantitative measurement that I don’t get. 14mm of what?[/quote]
looks like dave kirk doesn’t even know…
[quote=dave kirk]Not sure what factor “F” is but wheel flop is caused by having an inappropriate amount of trail.
Dave[/quote][/quote]
It’s the vertical distance the center of the front axle drops as the front wheel is turned from straight ahead to 90° sideways.