I am not very informed when it comes to these two words. My question is, if I converted to a 07 sportster front end, stock rake, and a 21 in rim, would this effect my rake or trail? the reason I ask is I got everything back together yesterday and went for a ride, if I really lay on the throttle, and get up to about 60-70mph I get an awful wobble in the front end. After this happend i slowed down and the wobble went away, rolled heavy on the throttle again to see if it would do it again,and it did not. I did this several times and it was hit or miss for the wobble. When I got home I did a quick check of the front end and everything seems to be rock solid and tight. The only thing I was able to come up with if its not the trail being messed up is, my forks that came with the bike were 4 inches longer than the new, and they really pushed the front end out, I also have 12" ape hangers, with my new forks being so much shorter, I have a much shorter wheel base (so it seems), take that and add apehangers, which are chalange to get used to, and now you have a bike that has such sensitive steering that a slight tap of the handlebars will send the bike in that direction. How does this make it wobble at high speeds if im not moving the handle bars, well, these bikes are so damn quick when you punch the gas that it darn near thows me off the back of the seat, so I can imaginge that I may jerk a little at the handlebars. As far as normal riding speeds and turns the bike handles like a dream, no wobble what so ever. Ahh one last thing, it doesnt wobble at slow speed but back to the sensitive steering bit, at 25 mph I can hardly keep it going in a straight line, this is where I came up with the sensitive steering and short wheel base idea. So I guess I got a little long winded here, but just wanted to get everything out there that I was thinking of on this situation, and see if anyone had any recomendations, or ideas on what may be going on. Thanks.

 

Looked at a couple of your other posts related to the front end swap to get a clearer picture of what you did.
You dropped the stock 1971 front end.
Installed a set of machined cups that allow you to use a 2007 front end w/1 inch stem.
That completes my understanding!

When you installed this 2007 front, what was used for the bearings?
Original loose *****?
Or did the machined cups allow the use of Timken roller-type bearings?

Was your original front end a +4 inch over stock length?
That would make the bike higher than normal in the front, unless the frame was raked, or the original was not-so-original and had (shudder) raked trees.

Does the bike now sit level, and not down in the front because of the now shorter fork tubes?

Pics would be a great help, because either your front end geometry is screwed, something is not installed correctly, or something is out of adjustment.
Typical things to look for if the rake and trail are OK - Front wheel alignment, condition of wheel bearings, wheel bearing end-play, correct torque on axle nut, neck bearing cups misaligned, neck bearings installed incorrectly, neck bearings in bad condition, triple trees misaligned or bent, stem nut under- or over-tightened.

Here is a primer on rake and trail -
http://www.rbracing-rsr.com/rakeandtrail.html

 

&nbsp\\;
I vote for the above issues as it sounds an awful lot like a problem&nbsp\\;in the neck with the bearings or how they are installed and/or adjusted.......

 

the neck bearings are brand new, how would they be misaligned or installed incorrectly?&nbsp\\; please dont think im being a smart ***, i truly dont know and just want to be sure i've done it correctly

 

I want to add a couple of more things, I had the wheel and tire balanced without the rotor installed, I called the mechanic, and he said that was fine, it didnt need the rotor on, and it would not hurt anything. when I jack the bike up the lower neck cup has some play back and forth and will not stay tight in the frame neck, when I lower the bike the&nbsp\\;weight of the bike&nbsp\\;holds it very tight to where I cant move any thing. I went for another ride ( i tightened everything with torque wrench, its only at very high speeds that I get the wobble, MAN i almost crashed it was so bad this time, cruising speed seems fine, I also noticed i cant go with no hands anymore either.

 

OK! so I put on all my protective riding clothing said a short prayer and went out one more time, and this may sound crazy and I may be way out in left field, but here goes. The new sportsters have rubber mounted motors, ours have rigid mount, new has rigid mount handlebar risers, ours have rubber mount. My handlebars shake so bad that even when idling the shake about half an inch&nbsp\\;because I had to use the newer mounts, rather than the rubber mounts. Anyways I went on a road where there are some straight stretches and not much traffic. I pushed forward on the handlebars as hard as I could to keep them from vibrating, and I went as fast as I could with out getting terrified, my gps is dead, but I figure I was doing about 80-90mph, point is, no wobble, plenty of vibration and throwing me off the seat, but no vibration. Any thoughts?

 

I have been following your post a bit and it sounds like you sometimes have a wobble and sometimes you do not. It is rather difficult for you (much less us) to determine if you truly have a wobble, or is it perhaps the wind condition (cross wind) on a particular on a particular day when you notice the wobble.

If the bike had a problem then it would wobble every time you were on it and hit 65 or 70 or whatever speed it is that you seem to notice things get loose. However, you should not have the cup loose in the frame! If the lower cup has play as you described a couple of post back, this may account for your sometimes wobble. Cups should be so tight that they require a press fit into the frame neck.

One thing that is not in your favor is those handlebars! You are going to have considerably less control with ape hangers than you would have with the bars that come on the machine or a good set of flat track style bars. So if you want to look cool, that's OK, as long as you can accept the trade off. The trade off with high bars is less control.....period.
Longer wheel base equals less stability at low speeds, but better stability at high speeds.
Shorter wheel base equals more stability at low speeds, but less stability at high speeds.
Everything is a trade off...........pg

 

Thanks pinion, I was hoping you would chime in. As far as the machined cups, I was a bit suprised at how smooth the were going into the frame since it took me over an hour to get the old out. Would this really be that big of a deal, since when the weight of the bike is on the cup, its rock solid, and I cant get it to budge. I really think its the handle bars rocking so hard they are throwing the whole bike into a frenzy. I guess if I go the speed limit it should never be an issue right.

 

Well, the cups should be tight.
&nbsp\\;As you say, the old ones were tight getting them out and the new replacements should be just as tight going in. To tell you the truth though, I do not know what you could do to fix this.

Given the right road surface, the right speed, and the right wind......these conditions could combine to induce the wobble you experience, and no doubt it is coming from the loose cup.
Remember, the weight of the bike is sitting on the cup at a standstill, but how much weight is removed when you are rolling down the road at 65 mph? Hard to say, but you can bet it is less than when its sitting there in the driveway.

I was riding my Dyna one day last year when it was really windy. I was running much too fast, around 85 to 90 mph on the Interstate 10 trying to get home asap. I passed a semi tractor trailer on the left. As I pulled alongside him I ran into a sort of vacuum. When I reached even with his front bumper the side wind hit me and I swear both wheels on the Dyna went sideways a full 6 inches on the road, maybe a bit more. Thankfully away from the truck and not into it! The Dyna gets wobbley at times also.
So I would say just watch your speed and you will have no problems. None of us need to run more than 10 miles over the speed limit anyway. Especially if we intend to get up and ride tomorrow just as we have ridden today. Keep an eye on that cup.........pg