| Author | Message | ||
     Glenn |
Hi, I have an '07 and changed my trees to the 2008 parts about 5K miles ago and have noticed an instability that I'd like to get verified by someone else that has made the switch. If I'm going 45-50 plus and make a fast/quick steering correction, I start to get a head shake. At higher speeds it is worse and at 50 can be controlled pretty easy but is disconcerting. The first time I noticed it was a little while after making the switch and hitting some sand in mid road while riding in Maine in early Spring. A friend was riding my bike and following me a couple of weeks ago and did a QUICK lane change to stay behind me on a highway and told me that it was almost a tank slapper. I though that my worn out front tire might have contributed but even with the new PR2 that I mounted this weekend, I can get it to do it. I changed the trees only and not the forks and know that the trail has been reduced from the way Eric made them and think that this is the issue. Steering stabilizers are too expensive and new forks about the same, but I don't like this especially if I get into an emergency some time and have this happen. This was the tech release for 2008: 2008 MODEL YEAR TECHNICAL FORUM BUELLŪ NEW UlyssesŪ Model Updates UlyssesŪ fork tubes have increased from 43mm to 47mm Forks are offset 5/8 inch forward with new triple clamps to increase stop to stop steering angle from 54 degrees to 74 degrees Front axle is offset 5/8th inch rearward in the new fork lower to maintain the original 54.1 inch wheelbase Based on this the trail has been decreased by 5/8" by only changing the trees. This is a nice graphic that Treadmarks posted in this link: http://www.badweatherbikers.com/buell/messages/142838/323241.html  My steering head bearings are tight, I have a new tire, suspension is set to my weight and tires are inflated properly. Anyone else experience this? Thanks | ||
| Ulynut |
What kind of front tire? | ||
| Glenn |
I took off a Pirelli Scorpion and now have a Michelin Pilot Road 2 mounted, front and rear. Same reaction with both tires. | ||
| Nipsey |
I have an 06 with 08 trees - none of that issue for me. From a ride perspective I could not really tell of any difference. | ||
| Ratbuell |
Wheelie or hit a few potholes, and retorque your head bearings. Sometimes you need to torque them, let them "settle", and retorque. | ||
| Rr_eater |
Glenn I had a DR650 that used to do this after tire changes. Loosen up the front axle pinch bolts, then loosen up and only SNUG the axle down, basically finger tight. Then grab a handful of front brake, and jump up and down on the suspension a bunch of times, compressing it like a hard stop. Then very carefully get off the bike and gently set it on the side stand, then torque the axle as normal, and tighten the pinch bolts. Worked every time. My Uly had a tendency to want to lay over going right, but had to fight it down to go left, did this and it fixed that too. Give it a try Bruce | ||
| Glenn |
Thanks for the stem bearing torque and fork to axle alignment tips. The shake though occurred before and after the tire change. I did recheck the stem torque last night and when I changed the tire last weekend, I did perform the fork compression before torquing the axle and pinch bolts but I'll try it again tonight since I may not have had the axle loose enough. I'm thinking that with the reduced trail and then a QUICK lean, which due to the lean and fork compression further reduces the trail, that the bike is unstable without enough trail. From Wikipedia http://en.wikipedia.org/wiki/Bicycle_and_motorcycl e_geometry "Trail can vary as the bike leans or steers. In the case of traditional geometry, trail decreases (and wheelbase increases if measuring distance between ground contact points and not hubs) as the bike leans and steers in the direction of the lean. Trail can also vary as the suspension activates, in response to braking for example. As telescopic forks compress due to load transfer during braking, the trail and the wheelbase both decrease." I did find in searching Sunday night that there was another guy who slid on three tar snakes in a sweeper and got severe head shake. He didn't say anything about a fork change on his Uly so I assume it was stock and I don't know what year. I'd be interested in someone with the 08 tree mod in doing a little safe experimenting. The thing is that quick avoidance, sand or gravel and tar snakes are all factors that can be out of your control. Thanks, | ||
| Glenn |
This is the link I mentioned earlier: http://www.sport-touring.net/forums/index.php?topi c=9488.0 "I Was riding in Northern Ontario last summer, Highway #129 in the middle of no where. Beautiful sweepers but a lot of road snakes (repaired tar strips). I came around one corner and ran across three strips side by side. I'm not sure what happened but the next thing i knew the bike was flopping violently side to side, not a tank slapper with the bars but the whole bike. It was so bad to actually knocked my left foot off the peg, which strangely seemed to straight it out. Scariest ride I had ever had. The whole area is either rock faces or a drop off to the river, and very deserted, it was an hour before I meant the next car. Not a great place to crash." | ||
| Tootal |
Glenn, I did this change 10,000 miles ago and have not experienced any head shake. I didn't notice any difference in fact. I've pushed it hard through the twisties and ran slab and never had any problem. I don't think you have a geometry problem, too many of us have done this with no issues. Just brainstorming here, did you torque your steering head bearings before you tightened the clamps on the forks? You should tighten the top clamp, then the steering head bearings then the lower clamp then the axle. If you tighten the upper and lower fork clamps before the head bearings, the head bearings will not tighten. I'm not saying you did it wrong, just throwing up a possibility. | ||
| Glenn |
Hi Tootal, Thanks for your input and I'm open to all of them. I followed the shop manual. I loosened the top steering stem pinch bolt at the upper tree, loosened the steering stem capnut, loosened the lower triple clamp pinch bolts and then torqued the steering stem capnut to 40 ft-lbs. I then torqued the upper pinch bolt and then the lower tree clamp bolts in that order. If you get a chance, can you do a quick left at around 50 and see what happens? Not a smooth turn, but a quick aggressive one? Thanks | ||
| Tootal |
Sounds like you did it correctly. Now try raising the front tire off the ground with a jack on the muffler. Grab the bottom of your forks and try to move it forward and back. Is there any movement or clicking noises? If so you have a bad bearing. I just got back from a week and a half long ride and head out tomorrow to go racing. I'll try that when I get back but I'm sure after riding out to Suches GA. and chasing Slowride all day, that I should have induced something if there was something to induce. I'll let you know the results of the experiment. | ||
| Glenn |
Thanks Total, The other night I did try moving the lower forks with my bike jacked up as you mention. I was through this about a year ago on my old Beemer and know the drill. I had to replace the bearings on it. It would start shaking at certain road speeds, very consistently. Looking forward to your test. Give it a very fast twitch to the left at 45 to 50 or so. Be careful! | ||
| Jamba |
Where do i get 2008 tripletrees to my 2006 xb12x? What is the part number? |
