I don't think there is a problem..... unless you plan on doing some racing. I have them on all 4 wheels, rear wheels don't really need them and it only helps with the brake dust on the front.... but it does help.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k