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Buell Motorcycle Forum » Big, Bad & Dirty (Buell XB12X Ulysses Adventure Board) » BB&D Archives » Archive through August 30, 2006 » Front brake lockup and wheel dynamics « Previous Next »

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Jjg0324
Posted on Friday, August 25, 2006 - 10:54 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Had a scare yesterday while taking a casual ride down a quite road. A car up ahead was stopped in the road facing me in the oncoming lane. My attention was focused on the car, what were they doing, turning left? I let off the throttle and began to slow, keeping my eye on the car. Then out of the corner of my eye, I see this large dog heading for me on the right side of the road. My reaction was immediate, grabbing the brakes and inducing a brief front wheel lockup. I am sure this was entertaining for the people sitting in the car, even more so had I not let go of the brake.

This is the second time this has happened to me in the 10 months I have owned the Uly. First time was on my dealer test ride. A car ahead of me on the freeway dynamited its brakes momentarily, and I did the same. Wheel locked up then too, but I was impressed at how the Ulysses kept its composure so I bought the bike. The second time with the dog, my impressions were the same, except I noticed it felt like the front wheel twisted up under the stress of the skid. When I release the brake I felt a definite snap, like the wheel was returning to its normal shape. I have also felt this sensation when braking late into a corner, releasing the front brake seems to result in more movement then I am use to.

So my question here is on the brake/wheel design used by Buell. Is it the best approach for a street bike? I have never owned a Japanese Sport bike, but have had other bikes with excellent brakes, BMW1100, Buell S3, Harley FXR with dual Performance Machine 4 pot brakes up front etc. None of these have exhibited the tendency to lock up or flex like I am experiencing with the Uly. For normal use, I love the front brakes performance. It has great feel, is powerful, and requires low lever pressure. But when looking at it, I can't help but think this design, due to the increased leverage, is more prone to lockups when grabbed with an overzealous panic grip. Wondering if we would be better off with a conventional dual disk or S3 type setup, at least until ABS becomes standard. What say the brotherhood?




Thank You

Jim G.
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Electraglider_1997
Posted on Friday, August 25, 2006 - 11:03 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Next time just let the dog come up and then give him a mouth full of sole dressing off the edge of your boot. Works every time and they always will remember the lesson you gave them.
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Electraglider_1997
Posted on Friday, August 25, 2006 - 11:05 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Maybe you gave the bike some counter-steering when you grabbed a handful.
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Aeholton
Posted on Friday, August 25, 2006 - 11:21 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Did you slide or did the rear wheel come up off the ground? I count the powerful front brake as a positive, not a negative. I would suggest trying to stay a little calmer and not grabbing the brake so hard.
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Bosh
Posted on Friday, August 25, 2006 - 11:42 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Jjg, I know what you're talking about. You can feel a kind of bang or something when you quickly put the brake on hard. I notice it especially when I'm forced to brake abruptly in a turn. I think it may be the fork breaking stiction when it compresses under heavy load. Doesn't seem like flex (fork or wheel) to me.
Bottom line... I don't know what the heck it is either. Doesn't seem to hurt anything though.
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Roadrailer
Posted on Friday, August 25, 2006 - 12:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

IMO, there's nothing wrong with the ZTL system. I can brake hard enough to lift the rear wheel off the ground without locking the front, just for a frame of reference. My guess is that the Uly has a lot more braking power than your previous rides. Powerful brakes like the Uly's require a progressive squeeze, not a sharp grab. Sounds like you're doing the latter.

Spend some time in a parking lot practicing your panic stops. Practice it until it becomes second nature, otherwise you won't do it correctly in a panic situation.
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Jjg0324
Posted on Friday, August 25, 2006 - 12:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Bosh, yes the bike overall behaves itself very well, which is a comfort. My thoughts on the front wheel flex are based on the design and what I have felt. The spoke portion of the wheel is purposefully made lighter and with less strength because of the design of the brake. The braking force is directly on the rim and not coming through the spokes. The brake caliper is applying force above and behind the contact patch and on the side of the rim. I can see where that could induce some twisting force. In both the times I experienced this, the situation in front of me cleared up, and releasing the brake to eliminate the skid was not a problem. Wondering what would be the outcome if I had to actually stop. Would I have held the skid and had the front end wash out, or would I release the brake to stop the skid then plow into what was in my way. Think I am making a case for ABS, at least for me. I may also mention that I switch back and forth between a RoadKing and the Buell. My auto-response system must be tuned to Roadking brake effort specs.
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Retired_cop
Posted on Friday, August 25, 2006 - 01:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

The difference in braking power from a Road King to a Ulysses can be best described as 2 hands on the lever versus 2 fingers on the lever. I had a real steep learning curve to make the transition from my ElectraGlide to the Uly. As we teach in the MSF course, squeeeeeze the brakes do not grab. Once the brake starts to slow the bike increase pressure on both front and rear progressively. Parking lots (empty ones of course) are a great place to practice braking. Just start out slow and work up.
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Bosh
Posted on Friday, August 25, 2006 - 02:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My note was referring to the "snap" feeling or sound you talked about. I know you heard something, but I don't think it was wheel flex.
The ZTL system is sound and proven in my opinion.
The skidding thing is all in the technique as you know. Letting off on the brake pressure and re-applying is the same thing as an ABS system would do.

(Message edited by bosh on August 25, 2006)

(Message edited by bosh on August 25, 2006)
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Jjg0324
Posted on Friday, August 25, 2006 - 03:20 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks for the input guys. Yes I am aware of how to apply the brakes, however with me, all that goes out the window in a true "true" panic situation. When you do bang the lever to hard the front end will wind up like a spring and release some energy when you get off the brake. Just want to mention that. Nuff said on this subject.
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Roadrailer
Posted on Friday, August 25, 2006 - 03:55 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks for the input guys. Yes I am aware of how to apply the brakes, however with me, all that goes out the window in a true "true" panic situation. When you do bang the lever to hard the front end will wind up like a spring and release some energy when you get off the brake. Just want to mention that. Nuff said on this subject.

That's why you need to practice it until it becomes instinct. Then practice some more. It's the only way to overcome the panic grab.

I seriously doubt the front end is "winding up" like you claim. Locked wheels (particularly front ones) do wacky things.
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Stevem123
Posted on Friday, August 25, 2006 - 04:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

When you lock or grab hard the front brake, the forks compress. Due to the fact that the forks are not verticle, the compression also shortens the distance between the front wheel and the rear wheel.

I think the snap you feel when you release the brake is the front wheel moving back to it's original position in relation to the rear wheel as the forks rebound. Granted, it's not much movement but enough to be felt under those conditions.

BC Steve
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Snowscum
Posted on Friday, August 25, 2006 - 05:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Have you checked the bolts that hold the disk
on and see if any are lose or have moved?
If one of those slip or the wheel goes out
of round then I would think that one or 2 of them moved. Look for witness marks.
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Dragon_slayer
Posted on Friday, August 25, 2006 - 09:18 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Hard braking? No skid, but I do feel the front wheel seeking left and tucking under the bike. Feel a weird vibe, think it's the tire rubbing the chin spoiler.
BTW, what ever happened about the updated spoiler for the older bikes? And the solution to the loose saddle bag seals?
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Xbimmer
Posted on Friday, August 25, 2006 - 11:07 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I'm thinking technique/conditioning also, no offense.

Did a similar thing first time I had to haul it down real fast on the freeway, no lockup but grabbed the lever hard and thought I was going over forward.

After 7k I'm still disciplining myself with this brake, I love it. I much prefer it to an on/off brake that lacks range in stopping power. I've never before ridden a stock bike with one-finger around town front braking.

The rotor floats and bangs around, is this possibly the mechanical reaction you're hearing/feeling?

Is it possible that the winding up and unloading feeling you're getting is simply just that? A buff front brake hauling down 500lbs+ of mass behind the front fork under a handful of effort, suddenly released, is bound to exhibit some perceptions of front end reactions, IMHO.

I think the Buell front end is probably as strong as they come, I'm not so sure there's a flex problem, but I'm no engineer.
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Windrider
Posted on Saturday, August 26, 2006 - 12:42 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

My guess is that this is just fork dive and rebound under hard braking. I have felt the same thing.

The 07 Ulys have different fork springs, more progressive springs.

Some of the motorcycle mags also complained of too much front end dive under hard braking.

One of the side effects of short wheelbase, long travel forks, and a powerful brake.
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Jackbequick
Posted on Saturday, August 26, 2006 - 09:39 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

For me, the secret to not braking too hard when I go for the front brake in a hurry is to ride with one or two fingers on or draped over the lever.

Around town, and when something alerts me to a possible need to brake hard, I get a couple of fingers on the lever.

Jack
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