| Author | Message | ||
     Rageonthedl |
So I have a question (yep a tech with a question) So im gettin Head shake around 120mph. Front tire is at 36psi rear is at 28psi (its the M/T drag tire, the tire its self is hard but has soft rubber)i have tryed playin with the rear psi is has helped some (38psi was waaayyyyy to hard it rode like crap at low speeds). I hear no clunk or chatter in front end. No weights have fallen off cuz i blance them with out weights. My belt is VERY streached out i am getting a new one but i dont think that would have anything to do with it. Really i think it is the Tire so i may just go get a 208 and see if it fixes the problem....but the M/T is sooo sticky i reall do like it..just under 120mph | ||
| Wyckedflesh |
Check the treadwear and see if either tire has picked up excessive feathering to one side or the other of the centerline. | ||
| Gentleman_jon |
Just thinking. Just because the headset bearings don't clunk or chatter might not mean they are correctly adjusted, especially considering the effects of what might be considered high speed. I would adjust the headset as per manual just to be sure. Perhaps a small amount of play is only noticeable at 120, perhaps not. I was also intrigued by your statement that you are able to balance the wheels without weights. I am afraid I have never heard of this technique, so I do not know how it works. You might want to check the balance another way, because headshake at a particular speed could easily be a symptom of a balance abnormality. It could easily be a tire problem too. Are you running Mickey Thompson drag tires front and rear? If so, there might be some set up issues due to the unusual size and construction of these tires, and the rather radical steering geometry of the XB. I look forward to learning how this problem is solved. | ||
| Tpoppa |
Try reducing you rear preload by 1 click. This will change the steering geometry in a way that will slightly increase high speed stability (and slightly decrease steering sensitivity). Or just stay under 120mph. (Message edited by tpoppa on May 30, 2005) | ||
| Izzinya |
Gentleman_jon Just because the headset bearings don't clunk or chatter might not mean they are correctly adjusted, especially considering the effects of what might be considered high speed. im with Gentleman_jon try going to the high end of the spec for neck torque just an idea Izzinya  | ||
| Rageonthedl |
Im gonna go try the preload thing, and as for blancing the tires with out weights here is what i do, put the tire on with the dot at the valve stem...blance...find where it needs the weight and put that spot over the vlave stem...just keep doing it till its at 0 or very close, id rather look at one weight than 5. and yeah i could stay under 120 but thats not the point, some thing is wrong and i have the D207 up front and the M/T in back | ||
| Gentleman_jon |
I see. If I understand you properly, this balance system is a static balance system, correct? While it is a very clever idea, and while static balance does work pretty well, ( it is what Dunlop uses at the race track), I just wonder if putting it on a dynamic balancer to check it out might not be a idea, just to see if there is some other balancing issue here that the static balance does not catch, and which only shows up at 120. I am not familiar with the M/T drag tire, but it looks different than regular street tires. If the diameter is much different than a stock tire, that could do it. We fitted a 195 Dunlop slick on my newphews XB9R and we could not get the bike to handle at all. We even dropped the forks to try to compensate for the increased diameter. Wobbled under acceleration at around the speed your talking about. Is the M/T tire larger than the stocker?If so, that will decrease stability, and it doesn't take a lot to do it. Reducing preload in the rear will increase fork angle, but it also affects the handling in other ways, and really should be set according to proper sag, that is why real competition shocks like Ohlins or Penske allow you to regulate preload and and sag, or ride height independently. If you are drag racing your bike, you might want to look into a real racing rear shock. Just my .02¢ | ||
| Tank_bueller |
and i have the D207 up front and the M/T in back My front 207 has been giving me some wierd, junk feeling, un-inspiring responses lately: 1. headshake when I let go of the bars at "normal" speed, and I can feel it at higher speed. 2. Sometimes, while in a corner, it's rock solid; but sometimes it feels flat(like 15-20psi). Not very confidence-inspiring, and it scares the hell outta me that I may need it to be there, and it will be on vacation. tank p.s. it hasn't let me down......yet. (Message edited by tank_bueller on May 30, 2005) | ||
| Rageonthedl |
It is a 190, the tire is very flat in the center. i to was thinking about dropin the forks abit to see if it would help any. The bike does not handle bad yet its not as good as a reg tire but like i sad its not that bad. Im thinking that im gonna say "F" it and just go get a street tire. | ||
| Tpoppa |
If you are talking about lowering the front end...that will have the opposite effect. It will reduce high speed stability, and too much will make the steering feel 'twitchy.' | ||
| Gentleman_jon |
Rage- Going back to street tire might be a good idea. We could never get the large diameter tires to work, - we had the same problem you have, and that was with racing slicks, not a drag tire. In addition, the larger tire changes the gear ratio quite a bit, so unless you have greatly increased your horsepower, like to over 120 HP, the bike will probably be slower, especially in acceleration. You could lower the forks until they are flush with the tops of the triple crown. That helped, but did not completely cure the problem. If you are going to get new tires, you might think about Michelin Pilot Powers, or Pirelli Diablos - lots of the members here report good things with them. I use the Pilot powers: got good mileage and they improve the handling a lot over the Dunlop 207. Poppa- You are right, but we are talking about lowering the forks in the triple clamp, not lowering the clamps on the forks. | ||
| Bristolxb |
Getting the same wiggle on my 12s as well. Had it on the worn STD Dunlops and changed to BT010's it still there. Been playing with the suspension set up to try to even things out. Dropped 1 on the rear preload and added 1/4 turn to the front and rear compression to soften it up as the roads here are pretty bad in places. This seamed to help a bit but it still feels a bit lively at speed.(100+) How do you Jardine boys lift the front as I want to check the head stock bearings as suggested earlier just to make sure all is as it should be. |
