Spring Rate

Golgother

Golgother

Hero member
Hey All

Last year I spent bouncing around on my hard tail Harris road bike trying to adjust for sag & static sag etc with out any success. I now suspect that I need a softer rear spring on the monoshock suspension which is a simple cantilever set up not a rising rate system with rocker arms etc. Rising rate systems use stronger springs.

Here's a site I found usefull for converting Nm to lbf/in  

http://www.unitconversion.org/torque/newton-meters-to-pound-force-inchs-conversion.html

I measured my rear spring at 75 Nm giving 663lbf/in which seems way stiff, I have since heard Harris recommend 300 lbf/in.

I noticed on one of Phil's race bikes that the rear suspension looked similar to the Harris set up. So what stiffness do you Motodd and indeed Harris guys like up ye rear end  ........ :D

Any comment welcome.......well that's opened the door.

                              Boing !
                                      Matt





 
Got a 95 kg or N/m or something spring on the cantilevered back end of my Mk1 Motodd, I'm using an Ohlins shock. The guys at Harris performance were dead helpfull, they sent me a few used ex race springs cheap to try out.


    Keith.
 
Hey Keith

What does she ride like with a 95 something spring ?

                          Cheers
                                Matt
 
Hi Matt - I seem to remember using a 75kg/cm spring on my racer with straight push type monoshock - it was a lot lighter machine than road going ones, but,unfortunately I was not . Unit was an original De Carbon one.  This works out to about 400lbs/inch so perhaps my memory is a bit duff. - Regards - Phil
 
Golgother said:
Hey Keith

What does she ride like with a 95 something spring ?

                          Cheers
                                 Matt
Click to expand...

  Hi Matt, no idea mate but she pushes round the workshop real sweet  ;)

  The 95 summats spring gives me the right amount of static sag and matches the front spring rate when I sit down on the bike, got such a long line of customer bikes in front of me just now getting the Motodd out on the road seems a long way off yet....


      Keith.
 
I dunno what springs you need, but there seems to be a bit of confusion over the spring rate units of measurement. A 75 N/m spring would be about as strong as a biro spring. I reckon the units you're talking about are KiloNewtons per metre, which are near enough the same as kg/cm.

Here's a conversion table which might be useful for comparing springs with rates quoted in different units.

KN/m      kg/cm        lb/in
  60          61          342
  65          66          371
  70          71          399
  75          77          428
  80          82          456
  85          87          485
  90          92          513
  95          97          542
100        102          570

Also for the pedantic - spring rates are N/m, not Nm. Nm is a unit of energy, also called a Joule.

Cheers,
Cam
 
.... not forgetting the oft quoted N/mm and of course - same values as KN/m.
 
Me confused ......... you bet ........ :-\

Phil there is a link with KTM here, my rear shock is a White Power product now know as WP for PC reasons and now bought out by KTM.

Cam you are spot on wehen you say there is lot of confusion and thanks for the conversion table that matches some figures I got from Ohlins.

I am now awaiting Bob to say ''take the bike to Maxton''

                          Cheers
                                    Matt
 
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