Tire Recommendations

[IRC]

I have been a long time lurker on the forum but have never had a requirement to post until now.

I have a 07 Xmoto that I have recently converted to off-road use with 21 – 17 wheel. I used a Xcountry rear and a GS800 front. The combination works well in the dirt but, I get head shake on pavement at speeds above 105 km/h. I am running a Kenda Track master II on the rear and Conti full knob on the front.

I remember reading in the forum that these bikes were sensitive to tire selection but I can’t seem to find the post. Does anyone have a recommendation to address head shake through tire selection?

 

[mhsnowy]

Could be that the head angles are all wrong with the 21 front and 17 rear.
Usually you would have a 21 front and 18 rear or like the x country a 19 front and 17 rear.

 

[mikeyboy]

did you expect it to behave on tarmac with full on nobblies?
you cannot have it all ways i am afraid.
you have raised the front of the bike with the bigger front wheel,this has altered the geometry ,you will need to raise the back to correct the caster angle,or drop the front to correct it,either way if you stick with a 21 inch front it will not feel as stable as a 19".
mike

 

[mhsnowy]

I think the 800 wheel is wider than the X challenge wheel so this may also make it feel strange.

But the main problem is as I originally said and Mikeyboy agreed with.

 

[Losttheplot]

To get the best tyre choice i'd change the rear rim to 18 inch, and the best way would be to get an decent rim (excel) laced to your existing hub.

The standard XChallenge rims are actually made of chocolate, and bend/dent very easily.

If you have fitted a high MX style front fender this will also reduce the stability of the bike at speed.

hth

 

[IRC]

Thanks for the feed back. I was of course aware of the changes in handing expected with a change from the super moto setup. I was not expecting the large amount of steering head shake that I am experiencing.

My rear 17 inch tire diameter is within a mm of the original death wing diameter in the xchallange 18 in configuration. So I do not believe the rear tire size is the culprit. The profile of the rear tire is flatter than I expected, which I believe is more likely to contribute to the instability I am experiencing.

As to the front, the 800 wheel is about 5mm wider than the challenge wheel. But the xmoto wheel is about 25mm wider still. So I don't believe that is the issue either.

I was sure I read here that these bikes were sensitive to tires when it came head shake, but perhaps it was on Adventure Rider.

Thanks again for you input so far.

 

[mhsnowy]

I don't think that its got anything to do with whether its only 5mm wider but less than the 17 original front but more to do with the fact that everything is different. Widths and front to back sizes.

It's not got the configuration of any of the X bikes but a mixture of all. They are the sizes fitted from new for a reason and any variation from that will affect the handling of the bike.

I can't see how you can gain the profile on the back wheel to gain an inch from 17 inch to 18 inch? That in itself must cause handling problems?

 

[crispy duck]

you could try torqueing up the head bearings see if that makes any difference.

 

[IRC]

In the name of science I installed the 19inch front from a Xcountry (the match to the rear). It has TKC mounted. There was significantly less tire noise, but the head shake was still there. So I think front tire/wheel is ruled out of the equation. I ran across a couple of posts from thumper talk where KLR and DRZ riders were having similar head shake issues at speed when using the Kenda Trackmaster II which were addressed when they changed rear tire to something less aggressive.

I may try the MT21 as the next step.