How much stiffer are the sidewalls on the M/T stiff sidewall slick vs M/T ET street slick? Because I'm running the ET STREET right now on my car right now and have a little sway on the top end. I was thinking about adding some tubes to stiffen them up a little if that would help. Since I have a manual trans on full weight car with a 2.9 Whipple. Because I was looking to the sell et street to get the stiff sidewall slicks. Pretty much new tires and hate to get rid of them. Before I buy the tubes or just sale the et streets and get the stiff sidewalls slicks. Thanks for the input.