# Roll resistance calculations error?

1. Dec 24, 2011

### Jas1159

Hi,

I am trying to calculate weight transfer from the front to rear of a vehicle and have already calculated the total sprung weight to be transfered.

I now need to calculate the Roll resistance generated by the springs using the following forumula and this is where the error occurs.

(SF/(WmF/SmF)^2) x TF^2 [ x ] 2 x ∏ / 180 = ArF

In laymens terms

SF = Front Spring Rate
WmF=Front Wheel Movement
SmF=Relative Front Spring Movement
TF = Front Track
ArF = Roll Resistance of Front Springs

Now i can't figure out if the x i placed in brackets [ ] is supposed to be / (x or /)?

The example is as follows;

(175/(1.00/0.75)^2)xTF^2x2xPi/180 = 2889.77 in.lbs per degree (roll resistance of front springs)

you will notice that the formula does not equate to the answer and to obtain the answer i must devide.... which present me with a problem as my understanding of this particular aspect is clouded by my understanding of the units...

I realise this is probably a 'suck eggs' moment but can somebody explain in practical terms what is meant by in.lbs per degree... the amount of in.lbs per degree of roll but in.lbs is both a distance and a weight...

Any help with either or both of the above problems will be much appreciated.

Regards
Jason

Last edited: Dec 24, 2011
2. Dec 25, 2011

### Ranger Mike

hello and Welcome
suggest you read Race car suspension Class
on t his mech eng forum posted Jul29-09

page two has calc for spring rates

merry Christmas
rm