Jump to content

Suspension Relationships


alan bechard
 Share

Recommended Posts

Courtesy of Team Sherco and especially Mr. Ibsen,

2.5" of sag between the fender bolt and the axle with a fully dressed rider on board.

E-mail or PM me if you would like pictures with arrows and circles and a diagram on the back of each one explaining what each one was to be used as evidence against us.

If that is not funny too you. Never mind.

I bet Charlie is laughing right now though!

OOOPPPPSSSS,,,,, just reread through the post and realized Charlie had answered.

I really do have pictures and arrows if you want though.

Edited by Alan Bechard
Link to comment
Share on other sites

 

 
E-mail or PM me if you would like pictures with arrows and circles and a diagram on the back of each one explaining what each one was to be used as evidence against us.

...in 2 part harmony :rolleyes:

Link to comment
Share on other sites

 
 
 

Alan:

Sorry I'm so slow to respond - had a family emergency requiring a few days away from home.

I've been comparing GOOD (my judgement) 1970's trialers to modern trials bikes and have found some interesting tid-bits - which have almost become LAWS of TRIALS MOTORCYCLE DESIGN for me. At least until I learn some more. Note that these "LAWS" are applicable for "full size" bikes (125cc and higher) with "full size" riders - they may not apply to smaller machines and smaller riders. Yet they may provide guidance for the smaller machines and riders.

1. Target wheelbase is 52".

2. There is precious little reason for the footpegs to be higher than the line between the axles with the suspension fully extended.

3. Foot pegs should be 16" ahead of the rear axle. Although information is gathering to suggest this "LAW" should state that the foot pegs should be 36" behind the front axle (52-16=36). When stated in the second form, the "LAW" seems to provide for the proper placement of the pegs if the wheelbase is shorter than 52".

4. The vertical distance from the footpeg to the height of the handle bar ends should be 30"-31".

5. The horizontal distance from the foot pegs to the handlebar ends (think of measuring this out on a side view photo of the machine) should be 20"-21".

NOTE 1: The first three "LAWS" (given some small tolerance, say less than an inch) seem to be exhibited on good trials machines manufactured 3 decades apart. This suggests to me, those are the RIGHT numbers for those specifications.

Additionally, I am currently convinced that since 1) all trials bikes should have a 52" wheelbase and 2) the foot peg height on all such trials bikes should be close to the line between the axles and 3) the foot pegs should be 36" behind the front axle - decades of design and testing has shown exactly "where" the mass of the rider should be on a trials machine. This location provides for proper front/rear weight shifting for optimum control. So, since we know where the riders feet should be, we now need to identify where his hands should go. Again, 3 decades of designs give fairly precise guidance.

NOTE 2: "LAWS" 4 and 5 relate to the riding position the rider is "forced" to adopt. Tolerances must necessarily be larger on these dimensions to accomodate:

- rider size - arm length - leg length, etc

These measurements will NOT put the rider in the same position as the old TY's with the high pegs, low bars and nearly level rider's back with the uncomfortable kinked neck.

These dimensions do put a full size rider on a full size machine in a comfortable, bent leg position with the hands falling comfortably in position on the bar ends. AND these dimensions do not require the rider to "feel" like he is uncomfortably/unsafely well ahead of his hands when weighting the front end - yet still allow major weight shifts to the rear when that is needed.

That's my two cents worth of machine research - which does not address your questions relating to rake and trail - but may be helpful in thinking about mods on the smaller bike for the smaller rider.

Bullfrog :rolleyes:

Link to comment
Share on other sites

 
 
 
 

Hmmmmm,,,,,, I think it will be larger than Dean could comfortably handle.

I got the short swingarm installed last night, I put the pressure test too it of a 1' jump and slamming my weight into it on landing. Seems fine at this point.

Time will tell.

Dean said it wheelied easier, but I never know if that is him talking, or saying what Dad wants to hear. It did appear that the front was coming higher quicker from my vantage point.

I also have the modified spring on it, so I have about 1" of Sag with his weight. I think I will try an even lighter one again.

The Dixie cup is this weekend, so, assuming little or no rain, it will get put to the test this weekend.

Link to comment
Share on other sites

 

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
  • Create New...