Funky handling

[skid jackson]

about two weeks ago I put a new rear tire on (pirelli mxextra). At the same time I cranked up the preload on my rear spring from about 8mm to 10 or 11mm. When I went for a ride I though I immediately felt the rear tire pull to the right. It was very wet and very slippery and it was a new tire so I was thinking it just might be the conditions. I rode the bike for about 15 miles but did not like the way it felt. I ran into a fast guy at the parking area and had him take it for a run. when he came back he said he thought it was fine and it was most likely just slipping and sliding. Fast forward one week and I'm riding a pretty technical 55 mile dual sport. All rocky single track. the back of the bike is all over the place and the front is doing some funky shiet too. There are lots of dry leave so its slip and slide again. I'm going very slow. so slow one of the two guys I'm with suggests I ride his ktm 200 while he rides my 300. they both know I'm faster on the 200. Its a nice way of saying you are riding so slow that you are holding us up and we need to get out of the woods..... TODAY!! We ride for a bit, my friend comments "dude this bike is really fast" ... we ride quite bit more ... I notice that the 200 with a very worn rear tire has better traction and tracking then my 300 w/new mxextra .... we stop again ... my friend say's "DUDE THIS BIKE IS DOING SOME SERIOUSLY WEIRD SHIET!!" it pulls to the right when you gas it, turns great going one way but doesn't like to turn at all going the other way and the front tire climbs ruts and sometimes does this weird skitter thing in certain turns. He was convinced the back tire was not lined up right. However i put it on the same way I have always been putting them on the last 3 years. When I eyeball the tire the chain and the sprocket every thing looks pretty straight to me.

I plan to do the following
measure back from the swing arm bolt and make sure the tire is lined up right.
check sprocket bolts for tightness. I replaced the sprocket this last ride but did torque the bolts to spec when installing. will double check
check all the linkage bolts for proper torque.
remove the handle bars and check to see if they are bent. I haven't had any good wipe outs that would bend the bars though
check bar mount bolts, if they were loose i would notice that on the trail though
pull front tire check the axle, eyeball the spacers inside the hub
Probably pull the rear wheel and check the axle and the spacers in the hub
although I have had both axles out before the ride and did not notice anything
loosen and reset the front forks
check the steering stem bearings

did I leave anything off the list???

this funky behaviour was most noticable after I installed the pirelli mxextra. I have had good luck with pirelli mt 16 and 18 tires and the scorpian midsoft mx32 on the rear. I have always had good traction in the rocks even with the midsoft terrian 32. the mxextra has a harder compond and is designed to be a multi terrain tire good from midsoft to mid hard. I figured the harder compond tire was just not gripping the rocks. I spoke with another rider who said he pitched them after one ride.

the other change I made was to crank up the preload on my rear spring. it went from 7 or 8mm to about 11 mm. Do you suppose the extra preload is putting too much weight to the front and causing the lack of traction on the rear? add to this a hard compound tire lots of rock and dry slick leaves you could have a busy rear end ....

the only other change was I snapped one of the front axle clamp bolts .. I only have one on the brake side. can't imagine that would cause any handling issues

that about covers it.
any suggestions on what else to look for/check out

 

[Brian]

Sounds like a solid troubleshooting plan. Good Luck.
Is the tire directional and mounted opposite as marked?
That is the only thing else I could think of to check in regards to your handling issues. Maybe it would effect it? Not sure if it would really do that you are describing though.

 

[GMP]

Part of your problem is the increased preload for sure, especially in poor traction situations. Perhaps the tire is a problem as well, but the preload makes it more obvious.

 

[Eric K]

Like Glenn said, I would back off the preload to where it was before and try it again. I would also check the rear wheel alignment. Also, verify your tire pressure.

 

[iancp5]

Sounds like 2 issues making it confusing.
Find out why it's biased to one side first. Don't forget to check wheel bearings front and rear. Why they should go at the same time as tyre changing is odd but maybe it has just highlighted them. Also look at the tyre - it could have a fault. If you can find nothing wrong remount it the other way round and see if it pulls the other way! When you have identified the pulling to one side then set the suspension up. There'll be threads on here about what sag etc.

 

[skid jackson]

I measured the axle bolt back from the swing arm bolt and it was spot on. I brought the preload down to about 7mm, it was up near 11 mm. One thing I found out was the rear rebound damping was only 8 clicks out. hmmm I'm guessing too much preload ... too much rebound ....too many rocks .... equals poor handling bike!! Not sure about the pull to the right. I'll check the handle bars to see if they are slightly bent and then just go ride it sunday. could also be the mx xtra tires suck in the rocks .....

 

[skid jackson]

well backing off the preload to 7mm and putting the rebound back to the stock setting, 16 out, definitely calmed down the back end!! it was very wet and slippery today so I did not get a real good chance to hammer. lots of tip toeing through wet roots. I'm going to replace these tires and check over the front end. definite improvement though.

 

[GMP]

Have you crashed recently? Front end (forks) tweaked in the triple clamps? Loosen everything up on the front end and retorque.

Dropping the preload to less than 10mm has a huge effect on calming the rear end down in the rocks. Your now at 7mm, go up 1mm at a time until you feel the harshness come back, then back off 1mm. If it squats to much add comp damping to compensate.

 

[roostafish]

This may seem simple, but I'd go back and check your front wheel to make sure it's tight, and no slop from wheel bearings (If it's acting funny in one direction though, I doubt it's in the front end).

Second, check the rear wheel bearings and chain stays. I doubt that's it, but it would certainly produce your symptoms.

Next I would check your swingarm pivot. To me, it seems likely that you have a bearing or bushing issue causing slop in the swingarm at the pivot.

If that ends up being a dead end, check the frame for a break, or crack. While your preload can affect your handling, preload doesn't care if you're turning right or left, so it would act the same in either direction.

I once broke a frame and did not know it (Honda, not GG). The bike acted really strange, but I rode it for weeks thinking I had a tire issue, or my shock was wierding out on me. I pulled the shock and noticed a distinct brown line on my frame. I looked closer to see that it was a crack. Not only was it a crack, the whole tube was broken, and when it was under load, would open up. After welding the tube back, it was fine.

 

[skid jackson]

I pulled the front end of my bike last night. There was a tiny bit of play in the steering stem when I jiggled the forks. The steering stem nut which was torqued down to 22 ft lbs back in the spring had loosened too hand tight. The nut underneath that which is suppose to be hand tight then ad a 1/4 turn was also hand tight. I cleaned up the bearings and set everything back to what it is suppose to be. I checked the bars and the sweep looks to be about 3 to 4 mm off from one side to the other. Thats around an 1/8 of an inch to a strong 1/8 off from side to side .... you think that is enough to notice a difference?? I'm going to order some new bars anyway. Still haven't come across anything major on the back end ....
I'll pull the rear tire today and see if I can get any movement from the swing arm. So far everything seems tight on that end.

 

[skid jackson]

on suggestion of another rider I pulled the bar mount bolts to check if they might be tweaked. Found one that was visibly bent, other didn't look so bad. Slightly bent bars, slightly bent bar mount bolt, (new bolts on the way) slightly loose steering stem nut ... guess that could add up to some funky handling. got some new pro tapers going on, will pull the rear tire tonight, check over the back end, and go for ride tomorrow.

Not really sure how much they affect things but ....Check those bar mount bolts!!