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  1. #1
    Senior Member Road Fan's Avatar
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    Handling of low trail bikes?

    Hi, I have a new question (well, maybe two) in the "bikes for handlebar bags" theme. We've got Randochap's fun video on riding his bike no-handed, with a massive (at least it's large) front bag on.

    How does this geometry ride with no front load installed?

    How does it handle with a moderate saddlebag load, and no front load?

  2. #2
    Senior Member Homeyba's Avatar
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    It's probably very stable with no load on the front and/or saddlebags. All the long rake will do is slow the steering down and make the bike less twitchy. That's why it works so well with a load.
    It doesn't get harder, you just go slower.

  3. #3
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Homeyba View Post
    It's probably very stable with no load on the front and/or saddlebags. All the long rake will do is slow the steering down and make the bike less twitchy. That's why it works so well with a load.
    I always thought a lot of trail results in slower steering, and a lot of rake corresponds to a smaller trail. So a lot of rake corresponds to faster steering.
    Last edited by Road Fan; 08-23-09 at 09:21 PM.

  4. #4
    Senior Member Homeyba's Avatar
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    It really depends because you can have a lot of rake and a lot of trail. Most roadrace bikes have small rake and small trail. Which makes for faster steering. The rake is fixed by the steering head. Trail is fixed by the location of the front axle in relation to the rake. Depending on the shape of the fork you can have lots of trail or no (negative) trail My first post was poorly done. Yes, a lot of trail will result in slower more stable steering.
    It doesn't get harder, you just go slower.

  5. #5
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Homeyba View Post
    It really depends because you can have a lot of rake and a lot of trail.

    No, I don't think so. The equation for trail has rake as a subtracted term (see the equation below), so trail gets smaller as rake gets larger, assuming wheel radius and head angle, the other elements, stay the same. -- RF


    Most roadrace bikes have small rake and small trail.

    Again, I don't think so, most road race bikes such as teh higher-end Treks have trail around 60 mm. Traditional sport tour bikes such as the Trek 610s and 620s are more in the 50 mm range. Traditional randonneuses are more in the 40 mm range. -- RF

    Which makes for faster steering. The rake is fixed by the steering head.

    Rake is the distance the axle is offset from the steer tube axis. It has nothing to do with the steering head, or head tube. --RF

    Trail is fixed by the location of the front axle in relation to the rake. Depending on the shape of the fork you can have lots of trail or no (negative) trail My first post was poorly done. Yes, a lot of trail will result in slower more stable steering.
    You have rake and trail mixed up. Trail is the ground distance between where the steering axis intersects the ground and the front tire contact point with the bike sitting on level ground. It can be calculated by

    Trail = (Wheel_radius*cosine(head_angle) - rake)/sine(head_angle)

    As the wheel gets bigger, trail increases. As the head angle gets larger (more vertical), trail increases. As rake increases, trail decreases. This equation is baked into the various online models of trail, or trail calculators.

    I'm not trying in this thread to have a discussion of the mechanics of rake and trail. I'm trying to ask owners of bikes that are designed to be very compatible with handlebar loads to comment on how their bikes handle when no handlebar load is present.

    Why? I'm thinking of having the fork of my Trek 610 bent to get about 55 to 60 mm of rake, so it will have about 40 mm of trail, and hence be compatible with a decent sized handlebar bag. But I wonder if I will like the unloaded response of the bike, for my $50 to $100 for bend or $350 to have a fork made.

    Road Fan
    Last edited by Road Fan; 08-23-09 at 10:23 PM.

  6. #6
    cycles per second Gonzo Bob's Avatar
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    I don't know about Randochap's ride but I can tell you about mine. I have an old sport/touring bike with a moderately steep head tube angle and a moderate amount of fork offset. The bike has no manufacturer stickers on it (only the Ishiwata 022 tubing stickers) but I've taken measurements of it and it appears to match exactly with the 1981.5 22.5" Trek 510 (http://www.vintage-trek.com/images/trek/Trek81a.pdf). The LBS owner told me the frameset was built in Green Bay WI so maybe it is an out-sourced Trek that the factory rejected.

    Anyway, the bike has only about 5cm of trail. Unloaded it rides just fine, although, perhaps a bit on the quick side (esp if I've gotten too used to the slow handling of my tri-bike). I can easily ride it no-handed. But with a medium handlebar bag and small rear panniers it gets a little twitchy, esp at low speed where it can develop a shimmy. High speed descending is fine, though, which is good since I recently finshed a 3+ week tour in the Alps and Pyrenees But I don't know if I could ride it no-handed when it is loaded, or perhaps i could if I packed all the heavy things as low as possible in the rear panniers.

    Reducing trail to 4cm? What is it now? I really don't know how that would feel. Probably really quick and maybe even a little unstable at first but then I bet you'd get used to it and it would be fine.
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    Last edited by Gonzo Bob; 08-24-09 at 06:53 AM.

  7. #7
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Gonzo Bob View Post
    I don't know about Randochap's ride but I can tell you about mine. I have an old sport/touring bike with a moderately steep head tube angle and a moderate amount of fork offset. The bike has no manufacturer stickers on it (only the Ishiwata 022 tubing stickers) but I've taken measurements of it and it appears to match exactly with the 1981.5 22.5" Trek 510 (http://www.vintage-trek.com/images/trek/Trek81a.pdf). The LBS owner told me the frameset was built in Green Bay WI so maybe it is an out-sourced Trek that the factory rejected.

    Anyway, the bike has only about 5cm of trail. Unloaded it rides just fine, although, perhaps a bit on the quick side (esp if I've gotten too used to the slow handling of my tri-bike). I can easily ride it no-handed. But with a medium handlebar bag and small rear panniers it gets a little twitchy, esp at low speed where it can develop a shimmy. High speed descending is fine, though, which is good since I recently finshed a 3+ week tour in the Alps and Pyrenees But I don't know if I could ride it no-handed when it is loaded, or perhaps i could if I packed all the heavy things as low as possible in the rear panniers.

    Reducing trail to 4cm? What is it now? I really don't know how that would feel. Probably really quick and maybe even a little unstable at first but then I bet you'd get used to it and it would be fine.
    If it was a Trek standard factory bike, it should probably have the word Trek at the tops of the seatstays, at least all the pre-1985 ones I've seen do.

    Mine is a 1984 610, and it came with a trail of around 50 degrees, pretty common for the Trek 6xx bikes. I had the fork bent once to get it close to 60 mm, by Ron Boi, a good Chicago framebuilder. He said he felt comfortable with several more adjustments if I needed them in the future. Before this change, I felt it was too quick, and a little hard to handle on slow climbs, seeming to dart back and forth quite a bit with my weight shifts and pedal strokes. I'm smoother now, but still, it was not pleasant. I'm worried about this behavior returning if I reduce the trail.

    What tires are you running? I've found tire diameter and girth to affect steering. These days I'm using Ultra Gatorskin 28s, with about 85 psi front and 90 rear.

  8. #8
    cycles per second Gonzo Bob's Avatar
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    No "TREK" on anything. Maybe the frame builder was just copying the 510.

    So you added ~1cm of trail because of the handling and now you are thinking about subtracting ~2cm? I suspect that you will find that the undesirable handling characteristics will return. If it were me, I'd probably get a beater fork and have that bent and try it out before bending the orig fork or spending $$ to have one made. If you find you don't like it, you can just go back to the orig fork.

    This Spring I was riding 700x23 Serfas SECA FPS but I put on 700x28 Specialized All-condition Armadillos for the tour. I didn't notice any handling changes when I changed tires.

  9. #9
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Gonzo Bob View Post
    No "TREK" on anything. Maybe the frame builder was just copying the 510.

    So you added ~1cm of trail because of the handling and now you are thinking about subtracting ~2cm? I suspect that you will find that the undesirable handling characteristics will return. If it were me, I'd probably get a beater fork and have that bent and try it out before bending the orig fork or spending $$ to have one made. If you find you don't like it, you can just go back to the orig fork.

    This Spring I was riding 700x23 Serfas SECA FPS but I put on 700x28 Specialized All-condition Armadillos for the tour. I didn't notice any handling changes when I changed tires.
    You understand my problem! My first step is to ask some people who might have experience with bikes set up this way.

    I saw a handling change on my Woodrup, also a sport-tourish bike, when I changed from 700C 22 mm tubulars to 700C 32 mm diamond tread tubulars. I like the cushiness. The Woodrup also has a tight fork bend, which gives a lot of the spring.

    Thanks for your input!

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    Actually, increased rake/decreased trail tends to be slightly unstable without the bag. My latest frame (74 degree head angle, 60mm of rake for about 35mm of trail) is ok with a bag, but has a tendency to speed wobble no hands without the bag. This is easily controlled by laying a knee against the top tube, but it does exist.

    This is similar to my previous bike that had about the same rake but a 72 degree head angle designed for off-road riding. It was truck-stable with the bag, and without the bag was significantly "lighter" handling.

    I think it's important to note that all if this is pretty minor. We've tended to make mountains out of molehills where handling is concerned, especially when the discussion is about trail. This was brought home to me by an acquaintance who put a front bag on a bike supposedly totally unsuited to it. He still rides it no hands and while he notes that it's slightly worse handling than it was, it's still perfectly rideable and pleasant.

  11. #11
    Senior Guest Andrey's Avatar
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    Resurrecting old thread.
    And...? Did you do it, Road Fan?
    I am thinking of re-raking a new fork to a smaller trail (45-50mm) to ride with a front bag on a Nitto rack. I find the trail of around 60mm and heavy front bag makes the bike feel like a truck. What is your experience?

  12. #12
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Andrey View Post
    Resurrecting old thread.
    And...? Did you do it, Road Fan?
    I am thinking of re-raking a new fork to a smaller trail (45-50mm) to ride with a front bag on a Nitto rack. I find the trail of around 60mm and heavy front bag makes the bike feel like a truck. What is your experience?
    It sounds like you have the same problem and goals that I do. If I had good front bag set-up, I'd probably load it up around 8#. I know that works terribly on my Trek, which has been modified to have a trail around 56 mm.

    Raking a new fork is interesting. Look at the tire clearance you have and try to estimate (or calculate, if you're good at math) how much it will decrease with the bend you want to have. If your new fork is already designed for a tight fit on a skinny tire, you'll never fit in a wider tire (maybe 30 mm?)with fenders, after the bend.

    I've investigated adding rake to my Woodrup fork and asked several builders if they would take the job. One is willing but does not sound supportive, as in he doesn't buy in to why this would help me. This is not the attitude I want from a craftsman whom I pay for service and collaboration. The other (who modified my Trek), refuses outright, citing concerns about handling, fork tube stress, final bend shape and suitable tooling (needs different tooling to add rake than to remove it), and the possiblility of causing the tubes to buckle. This is a frightening set of concerns and I don't have a year to resolve it, wanting to do a tour in July, several 100ks before that, and a century or 200k or so after that. I don't think this will get resolved on this bike, because I also am not ready to spend the $400 or so for a custom fork built to my spec. When it comes to it, I'll get a bike made for that use.

    Another thing, I think I need to do a better evaluation of the bike I have. I've compared the geo of my Woodrup against the bikes that Jan Heine prefers, and for 25 to 28 mm 700c tires it's not far from what he likes. So I'm changing at least the front brake to a Mafac and adding a small TA front bag mount with a Velo Orange decaleur. The bag, to start, will be my old big Rhode Gear bag with the click-mount removed and the decaleur mount added. That will move the bag a lot closer to the steering axis, which might enable the kind of handling I want. At least it will be better than it was with the bag sticking out from the handlebar. The Woody is already a lot better than the Trek after its trail was increased. My rake is only about 5 mm away from Jan's sweet spot for 700x28c. It's closer to right for 700x25c, but I'd rather ride on 28s. I'm a little heavy for 25s.

    So that's the plan. Thanks for watching this! Please let me know how you're project, or at least your thinking, gets on.

  13. #13
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Gonzo Bob View Post
    No "TREK" on anything. Maybe the frame builder was just copying the 510.

    So you added ~1cm of trail because of the handling and now you are thinking about subtracting ~2cm? I suspect that you will find that the undesirable handling characteristics will return. If it were me, I'd probably get a beater fork and have that bent and try it out before bending the orig fork or spending $$ to have one made. If you find you don't like it, you can just go back to the orig fork.

    This Spring I was riding 700x23 Serfas SECA FPS but I put on 700x28 Specialized All-condition Armadillos for the tour. I didn't notice any handling changes when I changed tires.
    I've been experimenting on a beater Peugeot UO-8, which came to me with an amazing 7 cm of rake, about 3 cm trail. I like the unloaded handling, but it has alignment issues - so many projects ... I haven't added a load to it, yet.

  14. #14
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    Quote Originally Posted by Road Fan View Post
    It sounds like you have the same problem and goals that I do. If I had good front bag set-up, I'd probably load it up around 8#. I know that works terribly on my Trek, which has been modified to have a trail around 56 mm.

    Raking a new fork is interesting. Look at the tire clearance you have and try to estimate (or calculate, if you're good at math) how much it will decrease with the bend you want to have. If your new fork is already designed for a tight fit on a skinny tire, you'll never fit in a wider tire (maybe 30 mm?)with fenders, after the bend. ...
    Also, as increased rake moves the fork crown lower, it will make the head-tube and seat-tube angles steeper. On a bike with a perfectly level top tube, it will now be sloping down. But if you started with a fork that has a fork-crown height that is a little higher than "normal," like a cross-bike fork, and then re-rake it, you could potentially still end up with your fork crown where you want it.

    I bought a "low trail Trek," an '82 Trek 614, and it is the first bike that I can reliably ride with no hands. With a 700x32 tire the trail is about 48 mm. So it is somewhat higher than an "optimal" front-load randonneuring trail. I have noticed that if I am holding the handlebars very lightly and there is no load on the front then I'll get a bit of wobble on a descent. So far I've only used it for commuting.

    Nick

  15. #15
    Senior Member Road Fan's Avatar
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    Quote Originally Posted by thebulls View Post
    Also, as increased rake moves the fork crown lower, it will make the head-tube and seat-tube angles steeper. On a bike with a perfectly level top tube, it will now be sloping down. But if you started with a fork that has a fork-crown height that is a little higher than "normal," like a cross-bike fork, and then re-rake it, you could potentially still end up with your fork crown where you want it.

    I bought a "low trail Trek," an '82 Trek 614, and it is the first bike that I can reliably ride with no hands. With a 700x32 tire the trail is about 48 mm. So it is somewhat higher than an "optimal" front-load randonneuring trail. I have noticed that if I am holding the handlebars very lightly and there is no load on the front then I'll get a bit of wobble on a descent. So far I've only used it for commuting.

    Nick
    That's true, but it isn't much change in angle. Assume you have a wheelbase of 1000 mm. You rake the fork forward by 5 mm. The hard part is to know how much the wheel rises in the fork, but let's just make a worst case assumption of 5 mm rise, in other words the head tube will be 5 mm lower. The angular change in head and seat angle is arctan(5/1000) = 0.29 degrees. This angle is small enough that if you measured the seat tube angle wrong by this amount, nobody would know or care. I would suggest rechecking your knee position, in this case.

    My overall contention has been, the change in head and seat angles isn't big enough to make a lot of difference. This is why.

  16. #16
    Senior Guest Andrey's Avatar
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    Thank you, guys for the info.
    I will be changing a Kona Progect 2 fork to Surly Cross check fork. The rake on both forks is within 1-2 mm, Surly fork is higher 5-10 mm(still have to measure it though). If I re-rake the Surly fork to 55 mm from 44 I would end up with the same height of the bike and the same or almost the same head tube angle(72.5) and shorten the trail to 48 mm from 61mm. Looks like I could bent the fork easily using a pipe bender, or I will make a jig to bend it. Surly fork has tire clearance for 45 mm tires with fenders, so 32 tires will fit fine after the re-rake.
    I think I would like to end up with a trail somewhere between 45 and 50 mm, so I could still ride the bike with no front load. BTW the tires are Passela 32 or Rubino 28, Nitto rack and Acorn Boxy bag.
    I have zero experience riding low end trail bikes, so I do not know how low I should go. Is 50mm better than 40mm or it is not enough? I do not think I would like to go shorter or should I?

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    Recovering mentalist Randochap's Avatar
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    I missed this thread (due to the fact I was busy surviving the incident that destroyed the Bleriot and parts of my body). It should be noted that the Bleriot was/is not a low-trail frame/fork. It is, in fact, somewhere around 65mm.

    I'm not sure what the 42mm Hetres did to that equation but I had no issues using 35mm Col de la Vies either. The bag you see in the video is one of the smaller Berthouds but even loaded down the bike tracked well. I rode that bike on brevets up to 300km (with 3900 metres of climbing) and never felt like I was fighting the steering. As far as downhill goes, I've put the Bleriot into steep curves at 60 km/h.

    I've never ridden a "low-trail" bike for comparison, but I'm very sensitive to bikes that don't track well.
    Last edited by Randochap; 04-30-10 at 01:20 PM.
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    "I think it's important to note that all of this is pretty minor. We've tended to make mountains out of molehills where handling is concerned, especially when the discussion is about trail."

    I'm quoting myself because I am even more convinced of this now than when I wrote it. I have continued my experimentation with trail and handlebar bags and am firmly convinced that trail makes a very minor difference overall. I believe the handlebar bag makes far more difference to handling than does trail, and am coming to the opinion that most folks who don't like handlebar bags don't like them because they are improperly mounted. A bag swinging from the handlebars -- as opposed to firmly mounted to a low-riding rack -- is likely going to create unpleasant handling regardless of geometry.

    My current brevet bike has very low trail, with geometry copied exactly from a 1950's Herse. It rides very nicely with a bag. I recently swapped it with a mate's Rivendell having higher trail than any bike I have ever ridden. It also had a properly mounted and fully loaded handlebar bag. It rode almost identically to mine, at speeds from 6 mph to about 35. Out of the saddle handling was strange to me and I wobbled around on it a bit -- which is exactly the same thing my mate said to me about mine. Bottom line? Given time to become accustomed to the handling of either extreme, I am sure that I would be perfectly satisfied with either.

    I still have a lot of respect for Jan Heine and really enjoy his stuff -- but I do believe he has concentrated on minutiae to the point that, to his readers, it looks far more important than it actually is.

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    Recovering mentalist Randochap's Avatar
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    Agreed. Because the French built this way I don't think it's necessarily to apply it as religion.

    Handling skills go a long way to accommodating idiosyncrasies. Low trail we are told will tend toward straighter tracking with a load, but likewise, if we are to take heed of gyroscopic forces, at some point handling in turns at speed will suffer.

    Personally, I eschewed handlebar bags of all kinds until I tried the low-mount system, which I believe was the real contribution of the French constructeurs.
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    Senior Member Road Fan's Avatar
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    Six Jours, and Randochap, thank you very much. My Trek experiment and my initial Woodrup rides were with a bag mounted very high and rather far forward. If I looked at the bike from the side, the center of the bag was definitely somewhat ahead of the front axle, on the Trek. On the Woodrup using the handlebar mount, the center of the bag is about even with the front axle. I'm now trying to fit a TA rack or a similar mountain bike front rack, and that will move the bag back by about 3 cm with the mountain bike rack, and perhaps 4.5 cm with the little TA rack. This alone might help a lot with steering, even if I don't modify the trail on the Woodrup.

    Of course with any bottom rack I can render the bag bottom stable, and with a decaleur I can hold the top of it still. My old Rhode Gear bag has an internal frame, so it will hold its shape. I'm very hopeful about this part of the experiment.

    I found when I rode both the Trek and the Woodrup with the bag, I did acclimate to the handling when at speed. But when I climbed slowly, the handling was rather more difficult than without a bag, and riding no-handed on the Trek was rather hard.

    Thank you both for joining the discussion.

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    FWIW, I am still in the process of making a fork with adjustable rake. This has turned into a more difficult project than I had imagined, but once completed, I hope it will be a solid learning experience. I will report back when/if there is anything to report.

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    Senior Member Road Fan's Avatar
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    Bump; I want to add something later on.

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    Quote Originally Posted by Six jours View Post
    FWIW, I am still in the process of making a fork with adjustable rake. This has turned into a more difficult project than I had imagined, but once completed, I hope it will be a solid learning experience. I will report back when/if there is anything to report.
    This is very cool! Can you describe your approach? I understand if you want to keep it under wraps, though. Can't wait to hear how it works!

  24. #24
    Senior Member Road Fan's Avatar
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    Six jours,

    Ignore this if you don't want any more ideas, but I've been imagining something like this: a unicrown fork with straight blades or at least very low offset and decent diameter down to the bottom. At the bottom, joined to the tube using perhaps gussets in addition to the normal dropout attachment, a horizontal dropout with a forward-facing slot. No fender to minimize issues with changing tire /fork clearance. The slots on both sides have graduations to facilitate aligned and repeatible installations. QR or bolted-axle pressures hold the wheel in place, just like with standard dropouts. If the wheel is not stable, tending to ride backwards in the slot, an alignment screw in the back of each slot, running forward to stop the axle. Axle still obviously needs to be clamped.

  25. #25
    Senior Guest Andrey's Avatar
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    I oped for the replacement fork from a hybrid bike that I had laying around with more rake to reduce the trail instead of buying another fork and bending. I measured it and it looked like 57 mm rake(perfect!). According to the on line calculator the trail got reduced from 60 to 48-50 mm.

    I had to change a headset from threadless to threaded and stem, but the I like the end result. I mounted the front rack, Acorn bag and a gallon(!) of "car wash soap" in it for the weight and went for a ride around the neighborhood. Seems like the handling improved; it still fells heavy(not as much though) and I still could not ride it with no hands for more than 10-15 feet at a time, but it does feel a little more stable with front load. The bike though did develop a slight shimmy with no load in the bag and riding with no hands at high speed which it did not have before, but it is very minor and it did not bother me on the test ride.

    I have a fleche ride coming up this weekend and I will test the set up on the longer ride.

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