2015 Mustang IRS Spring Rate

[Mark Reynolds]

What spring rate is supplied with the 2015 Mustang IRS option?

[edwardb]

My Anniversary Roadster kit with the 2015 IRS came with 500# front and 400# rear springs. Note this kit also came with front and rear sway bars. Don't know if that makes a difference or not.

[Mark Reynolds]

Thanks Ed! This is interesting. The T-Bird IRS came with 750lb/in springs. This indicates the motion ratio is significantly different between the t-bird and Mustang IRS. I will peruse your build thread for a look.
Regards, Mark Reynolds

[Mark Reynolds]

Had a look at the T-bird IRS on the FFR website and confirmed that yes the shocks are much further inboard and also further from vertical - which necessitates a higher spring rate for the same effective rate.