Can a rear tire cause front end wiggle?

[ULEWZ]

I was having a problem with the stock six day tire on the front deflecting sharply off of rocks, so I spooned on an MT-16. This tire sticks like glue, but I developed a terrible back and forth with the front end going about 40 mph on a semi rocky fire road. The front end wiggle felt like it started in the rear end. Is this possible?

I followed the recommend procedures to install the front tire, using a screwdriver in the slot to allow the forks to find center easier, moving the forks inboard and then outboard, and tightening the right pinch bolts half way between the two, but the front rim still has a little side to side ability (I believe this is the way it is suppose to be?)

Just another piece of info: the suspension felt great until I was bottoming out at KM and turned in 2 clicks of compression. Is there a corresponding rebound adjustment to make?

I have an MT-18 tire (want to stick with a DOT tire) on the rear which I just hate, but it only has 3 rides on it. The first ride was in the rocks at Kennedy Meadows and the knobs chunked pretty bad. I have a Kenda trailtech II just waiting to spoon on, but wonder if this will help any with the front end stability?

By the way, I ended up adding 4 clicks of rebound to the front end to help, and it kept the wiggling way down, but still feel the rear tire had something to do with it.

Any ideas (if you are recommending a different rear tire, please suggest a DOT tire)?

[marv02]

Mine just wiggle in the sand I going to try the lowwer the fork tubes in the tripple trees making more of a chopper stye The bike works great on every thing else try to rasie or lowwer you'r fork tubes.

I just removed my Kenda Millvile 771 rear tire it had about 30 to 35 hours on it like I said I ride mostly sand with hard base It worn out very fast.

Tire hooked up great but did not last long.

I giving a Dunlop 739 Desert tire a try this time around It mite last longer I hope But at $85.00 a pop I need to find a tire that holds up.

[WR250F Captain]

mine walked around when I tried to ride it like a yamaha, with my knees, once I held the bars a bit tighter it still did it a bit but its not that bad.

I think it has to do more with the rake angle than the rear tire.

[ULEWZ]

Well, it handled great until I changed 2 things, the rear tire and more compression. The compression needed to be tightened up, and the rear six day tire was worn out.

It was handling loose, so I first tried loosening the rebound 2 clicks and I was standing when I got the fast back and forth whobble, and it was not fun. The bike handles great in the sand, so that is not the problem. I then increased the rebound back to the way it was, and then 2 more turns in. It is rideable now, but not great, so I will leave it that way for another ride and see what happens. The Mt-18 does hookup in the sand and will throw some really big rocks, so ride clear if you are behind someone with that tire.

So let me ask another question: What will a chunked out rear tire feel like when going faster?

Pieces missing from the center and side knobbies.

[marv02]

What are you riding on I had a Kenda Trackmaster on my Old Cr did the same it chunked the rear tire due to riding on hard rocky and sharp edged stuff just tore that tire up before I was riding on that type of surfaces it was North Carolina dirt tire wore great back there untill I move back out in Califonia desert riding.

When you turned you'er rebound out was it in the rear did this make it track better in the sand ?.

I wish I could get my KTM handle more like my old CR did but there 2 diffrent types of bikes I still think the extra weight is what I feeling in the whoops The CR just hold it wide open and float over stuff with the KTM man handle the bike over stuff and hope you don't drop the front in to the next set of Whoops.

[ULEWZ]

What are you riding on I had a Kenda Trackmaster on my Old Cr did the same it chunked the rear tire due to riding on hard rocky and sharp edged stuff just tore that tire up before I was riding on that type of surfaces it was North Carolina dirt tire wore great back there untill I move back out in Califonia desert riding.

When you turned you'er rebound out was it in the rear did this make it track better in the sand ?.

I wish I could get my KTM handle more like my old CR did but there 2 diffrent types of bikes I still think the extra weight is what I feeling in the whoops The CR just hold it wide open and float over stuff with the KTM man handle the bike over stuff and hope you don't drop the front in to the next set of Whoops.

I only turned the front rebound in, not out.

If you follow the golden rule of sag and get the proper springs to get that sag, the thing actually handles pretty good. At least mine use to. I set the compression front and rear almost all the way out, until Kennedy Meadows. That place demands more compression (lots of sharp edged rocks), so I turned it in on the forks 2 turns. The back was fine. The rebound front and rear were set to stock, then 2 more turns in on the forks. I got most of my confidence back, but it still isn't perfect like before. I just may replace that rear tire and give it a whirl, but it is a bear to remove/install.

Originally Posted by Dwight_Rudder View Post

Static sag in the front fork is usually 35-45mm. Rider sag is 75-80mm.

Set your rear shock per the "GOLDEN RULE of SAG".

You want 34% of available travel in rider sag. On the KTM that would be about 115mm. ( + - 3mm). Static sag should be 40-45mm. Preload on the shock spring should never ever be over 10mm. Best about 5mm. ( + - 3mm). Set your static sag to about 45mm . If you have the correct spring you will have the correct rider sag. If you have just a bit more than 115mm , tighten your static sag / Preload till you are as close as you can get without going under 40mm static sag. If you end up with 40mm of static sag and more than 118mm rider sag you need a stiffer spring. If you have 45mm static sag and less than 112mm then you need a lighter spring.

Back off your compression till you are bottoming lightly front and rear on the biggest hit you want to take. Then go back in 2 clicks.

Increase your fork rebound by 2 clicks. 3 clicks if you go to a lighter fork oil like PJ1 2.5wt. I would recommend 115mm oil level and the PJ1 2.5wt if you haven't had your fork high speed compression valving reduced. Maxima 5wt if you have.

Increase your shock rebound by 1click per .2kg of increase over the stock setting of 20 clicks out from full in.

Dwight

[WR250F Captain]

if you adjusted the rear rebound, that could do it. rebound thats too fast can make the bike ride higher, taking some rake off your forks, and speed wabble.

i don't know about wp, but kayaba suspension, if you turn the rebound from soft to hard, it slows down the action, so by turning it to soft, it allowed the rebound to be more free and spring back.

which way did you adjust the rebound

[ULEWZ]

if you adjusted the rear rebound, that could do it. rebound thats too fast can make the bike ride higher, taking some rake off your forks, and speed wabble.

i don't know about wp, but kayaba suspension, if you turn the rebound from soft to hard, it slows down the action, so by turning it to soft, it allowed the rebound to be more free and spring back.

which way did you adjust the rebound

I don't remember touching the rear rebound, just the front, but I will set it back to stock just in case.

Just checked the rebound, 25 out on the shock which is stock. 13 out on the forks which is 2 less than stock (stock is 15 turns out).

I set the air pressure in that pig rear tire at 14psi, maybe that tire needs less pressure?

[marv02]

Ha Ha tire are Fun I just changed out my rear 30 Minutes done a lot of them over the years still sucks doing them.

So do you think I need to go stiffer on the front end as in compression, Like I said it dances in the front only in the loss stuff. It likes to follow the ruts in the sand sometimes it gets hairy.

[ULEWZ]

Ha Ha tire are Fun I just changed out my rear 30 Minutes done a lot of them over the years still sucks doing them.

So do you think I need to go stiffer on the front end as in compression, Like I said it dances in the front only in the loss stuff. It likes to follow the ruts in the sand sometimes it gets hairy.

I only went stiffer on the front end compression because it was bottoming out on rocks. Following what dwight says, set the compression as soft as possible without bottoming out. Is your sag set properly for your weight?

Where in Cali are you, I am in Northridge in the Valley.

[marv02]

Yes my sag is correct I guess after my parts come in to fix my oil leak and my new tank I first going to try the lowwing the fork tubes if this is not the ticket I try 1 click softer on the compression in the front end, and go from there.

I up here above LA above Landcaster going east I live in Califonia City I work Out here not because I like it out here not a place I planning to retire at, As we all know so well good jobs are getting harder to find every day now.

Stiffer on the front end compression because it was bottoming out on rocks. Following what dwight says, set the compression as soft as possible without bottoming out. Is your sag set properly for your weight?

Where in Cali are you, I am in Northridge in the Valley.

[ULEWZ]

Since I spooned on the Trackmaster II rear tire, most of my shimmy problems have gone away. I also raised the fork oil to 120mm and that allowed me to loosen up the compression. This also helped loads and it doesn't bottom now and is more plush. It is still a tad nervous, so I just bought a Scotts underbar damper from a local shop (Factory MX). I got a fantastic price that beat the next lower price by $20. Can't beat that. I will pick it up in a few days and can't wait.

[marv02]

Well I blew my fork seals so I will try to play with my oil level also see if that helps out I should be getting my new seals in some time this week then a couple hours to change every thing over Oh what fun getting the KTM to work as good as my last bike.

I had those wet suit type of fork wippers on the bike I could not see the dryed up mud that was under them that did my seal in I not going to put those back on thats for sure.

If I can get this KTM to handle and be as stable as my OLD Honda CR this will be the perfect bike I know it takes time to get them right but it seems that Jap bikes are more forgiving to get them to handle correctly at least older steel framed CR Honda's are.

[marv02]

Thinking about it when my Kenda Millvile was new the bike danced around bad as it wore out the bike tracked much better now I put that New Dunlop desert rear tire on I gotten hairy once again the bike started to swap on me over a high speed rolling jump the other day I was in top of 6th gear pinning wide open it was a hang on and hope for the best type of ride that worked out for me that time this 560 has lots of top end speed you dont notice how fast you realy are moving untill the bike starts going were it wants to go not where you want it to go instead:bonk: .

I wonder if some sub tanks for the front end would help out ? .

I been riding for many years and never needed a steering stablizer hate to buy one now it seems you just masking a problem thats still there I like to get it right not hide it .

Since I spooned on the Trackmaster II rear tire, most of my shimmy problems have gone away. I also raised the fork oil to 120mm and that allowed me to loosen up the compression. This also helped loads and it doesn't bottom now and is more plush. It is still a tad nervous, so I just bought a Scotts underbar damper from a local shop (Factory MX). I got a fantastic price that beat the next lower price by $20. Can't beat that. I will pick it up in a few days and can't wait.

[WR250F Captain]

you would be masking a problem. feel your stabilizer after a good ride, and its warm for sure.

but they also have other features, like automatically making your bike get itself out of a rut, ones that turn... its not that magical, keep you from wearing out as much bouncing off rocks.

even if I didn't have that busy little front end, i still would have gone with the stabilizer, after riding with one in the sand, they are worth there weight in gold. especially the scotts

Thinking about it when my Kenda Millvile was new the bike danced around bad as it wore out the bike tracked much better now I put that New Dunlop desert rear tire on I gotten hairy once again the bike started to swap on me over a high speed rolling jump the other day I was in top of 6th gear pinning wide open it was a hang on and hope for the best type of ride that worked out for me that time this 560 has lots of top end speed you dont notice how fast you realy are moving untill the bike starts going were it wants to go not where you want it to go instead:bonk: .

I wonder if some sub tanks for the front end would help out ? .

I been riding for many years and never needed a steering stablizer hate to buy one now it seems you just masking a problem thats still there I like to get it right not hide it .

[ULEWZ]

I been riding for many years and never needed a steering stablizer hate to buy one now it seems you just masking a problem thats still there I like to get it right not hide it ? .

I have done loads of research on this bike, and the problem is in the steering geometry. It is a heavy bike so KTM speeds up the steering. It makes it handle light in the tight stuff, but nervous in the fast loose stuff. I have made the suspension as good as it is going to get, so the next fix is either a 20/22mm tripple clamp setup, or a steering damper. The scary high speed tankslappers have been fixed with a new rear tire and fork oil height. The damper will help in the sand and rocks. I almost had a bad crash hitting a rock going over whoops and it caused the bars to instantly hit the stops. I somehow saved it, but veered off course about 10 feet. Good thing there wasn't a cliff there. The damper will fix this. these KTMs require a lot of tweaking to make them great, and I am close now. The power is perfect now, stays cool with the fan, and is plush with the golden rule of sag. I just wish it was lighter. I could save some weight by removing all the smog stuff, but I leave it in place for eyewash just in case.