Tire and or Suspension...

[skiracer]

So I rode an event last October, and during the last test, the dirt was worn off the roots, as was the bark, leaving a lot of nice bare roots exposed.  I was having some issues with the front end not getting a good grip in these conditions.  Question: problem with tire selection, suspension settings, or just poor driving on my part???  Any thoughts, comments?

1976 250 MC5 Original Owner
1976 Penton 175 XC

[SouthRider]

Possibly - YES.

Could be any or all of the above.

Impractical to change tires for each event, and then there will always be a mix of terrain. Trials universal tires work better than knobbies on slippery roots or rocks, but not so well in the mud. Lower tire pressure helps tires to bite, but risks more flats.

If suspension is set up for MX tracks it will be way too stiff in the woods, and vice versa.

Getting up over the bars helps to keep the front wheel weighted on slippery roots, and riding/training often enough to have the stamina to stay there helps.

In the day we attempted to set the bikes up in advance of each race for what the terrain was - all within our budget and mechanical skills.

It's all a trade off - much like most things in life.

_____________________________________________________________________________________

"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

[Paul Danik]

Greetings,

    You say the front end was not getting a good grip, were you initiating a turn on the roots and the tire was just sort of sliding along the root ?  Or

   The angle of attack is first and foremost in my mind. The more square you hit those shiny suckers the better off you will be. Lots of variables, going uphill over roots try to keep your weight back and let the front wheel float over them as the rear wheel drives you forward. The back wheel may kick around a bit but if you have some momentum working for you the bike will keep on trucking in a forward direction even as the rear wheel does its dance. Momentum / speed is your friend in many of those situations and the gyroscopic force of the spinning wheels will help to keep the bike upright, BUT, if you hit a shiny root at a bad angle and the front wheel wants to follow it you may get to sample the soil, hitting them as square as possible is very important.

  In summary, proper angle of attack, lighten the front end a bit and carry a little bit of momentum / speed, AND....LOOK DOWN THE TRAIL TO WHERE YOU WANT TO GO....
 
    Reminds me of a story that Jack Penton told about riding out west with his Dad. They were heading up a mountain on a washed out dirt road with Jack leading the way, Jack said he was taking it easy with his Dad following him and I think another gent was along as well. When they reached the top John told Jack that the climb up the mountain had hurt his back and he was feeling a bit of pain. Jack suggested that John lead the way on the ride down so as to allow him to ride at his own pace. Jack said that when they headed back down with John in the lead John took off like a rocket and really was scaring the heck out of Jack. Jack said he tried to get up close enough to John to get his attention and get him to slow down, but to no avail. When they got to the bottom and stopped Jack questioned John as to just what the heck he was doing going so fast on the washed out trail with his back bothering him. Johns response was that the faster he went the more the motorcycle did what it was designed to do as the suspension was doing its job of absorbing the impacts and John said he / as the rider / felt very little of the impacts and for him it was the smoothest way to ride down the mountain.

Hope this helps, or at least entertains...
Paul

PS  I found this video on gyroscopic forces, it isn't exactly what I was looking for, but it demonstrates gyroscopic forces. I remember doing a trailride many years ago with my son Chad. We came across a section of trail several hundred feet long that was crisscrossed with dried ruts like you wouldn't believe. I looked at the other end of the section focusing on a certain point, clicked the bike up a gear and screwed on the throttle and in no time had crossed the section. Chad hit it slow and had a rough time, but not the next time !!!! I might add, be up on the pegs and have your butt hanging back to lighten the front end and give your rear wheel optimum drive, and may the force be with you, gyroscopic force that is...
https://www.youtube.com/watch?v=dV63f1H_lXg

[wfopete]

What tire pressure were you running?  If it was more than 12 psi then I suggest you drop it into the 10 psi or lower range.



Pete Petrick
175 Jackpiner
Slow but Good

[skiracer]

Thanks for the input. The bike is an 83 PE, so, the suspension is for the woods.

quote:Originally posted by SouthRider

Possibly - YES.

Could be any or all of the above.

Impractical to change tires for each event, and then there will always be a mix of terrain. Trials universal tires work better than knobbies on slippery roots or rocks, but not so well in the mud. Lower tire pressure helps tires to bite, but risks more flats.

If suspension is set up for MX tracks it will be way too stiff in the woods, and vice versa.

Getting up over the bars helps to keep the front wheel weighted on slippery roots, and riding/training often enough to have the stamina to stay there helps.

In the day we attempted to set the bikes up in advance of each race for what the terrain was - all within our budget and mechanical skills.

It's all a trade off - much like most things in life.

_____________________________________________________________________________________

"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

1976 250 MC5 Original Owner
1976 Penton 175 XC

[skiracer]

Hi Paul!  Thanks for responding, and what a great story, thanks!  I haven't looked at the link yet, but I will.  Hope all is well.

quote:Originally posted by Paul Danik

Greetings,

    You say the front end was not getting a good grip, were you initiating a turn on the roots and the tire was just sort of sliding along the root ?  Or

   The angle of attack is first and foremost in my mind. The more square you and hit those shiny suckers the better off you will be. Lots of variables, going uphill over roots try to keep your weight back and let the front wheel float over them as the rear wheel drives you forward. The back wheel may kick around a bit but if you have some momentum working for you the bike will keep on trucking in a forward direction even as the rear wheel does its dance. Momentum / speed is your friend in many of those situations and the gyroscopic force of the spinning wheels will help to keep the bike upright, BUT, if you hit a shiny root at a bad angle and the front wheel wants to follow it you may get to sample the soil, hitting them as square as possible is very important.

  In summary, proper angle of attack, lighten the front end a bit and carry a little bit of momentum / speed, AND....LOOK DOWN THE TRAIL TO WHERE YOU WANT TO GO....
 
    Reminds me of a story that Jack Penton told about riding out west with his Dad. They were heading up a mountain on a washed out dirt road with Jack leading the way, Jack said he was taking it easy with his Dad following him and I think another gent was along as well. When they reached the top John told Jack that the climb up the mountain had hurt his back and he was feeling a bit of pain. Jack suggested that John lead the way on the ride down so as to allow him to ride at his own pace. Jack said that when they headed back down with John in the lead John took off like a rocket and really was scaring the heck out of Jack. Jack said he tried to get up close enough to John to get his attention and get him to slow down, but to no avail. When they got to the bottom and stopped Jack questioned John as to just what the heck he was doing going so fast on the washed out trail with his back bothering him. Johns response was that the faster he went the more the motorcycle did what it was designed to do as the suspension was doing its job of absorbing the impacts and John said he / as the rider / felt very little of the impacts and for him it was the smoothest way to ride down the mountain.

Hope this helps, or at least entertains...
Paul

PS  I found this video on gyroscopic forces, it isn't exactly what I was looking for, but it demonstrates gyroscopic forces. I remember doing a trailride many years ago with my son Chad. We came across a section of trail several hundred feet long that was crisscrossed with dried ruts like you wouldn't believe. I looked at the other end of the section focusing on a certain point, clicked the bike up a gear and screwed on the throttle and in no time had crossed the section. Chad hit it slow and had a rough time, but not the next time !!!! I might add, be up on the pegs and have your butt hanging back to lighten the front end and give your rear wheel optimum drive, and may the force be with you, gyroscopic force that is...
https://www.youtube.com/watch?v=dV63f1H_lXg

1976 250 MC5 Original Owner
1976 Penton 175 XC

[skiracer]

I don't use tubes....

quote:Originally posted by wfopete

What tire pressure were you running?  If it was more than 12 psi then I suggest you drop it into the 10 psi or lower range.



Pete Petrick
175 Jackpiner
Slow but Good

1976 250 MC5 Original Owner
1976 Penton 175 XC

[Pat Oshaughnessy]

I was going to say what Paul Said only he did a much better job than I would. In my area 10 lbs. of air may result in pinched tubes & flat tires . I ran 14 or 15 lbs. To many rocks![]