The shape of the CST 4" spindle is supposed to make it stick out more than a stock steering knuckle. CST recommends 4.75" back spacing, but some have run stock rims without rubbing, but stock rims usually means narrower tires, (and they will pull in the same tire more than a wider rim, so even though the backspacing might be the same, the same tire might rub on a wider rim, if it was close with stock). For example, BFG states that on average a tire will lose 0.2" of width for every half an inch narrower rim, than the measuring rim from the spec sheet, so if a tire is listed as 12.5" on a 10" rim, on a stock 8" rim it will be 0.8" less wide, (11.7"), but pull in 0.4" on each side of the rim. In some cases about half an inch might make the difference.thebassn8tr said:What are the best specs for 20" KMC Rockstars to avoid any spindle rub? I am going to do the CST spindle, PRG 2.5" spacer, Deaver, block lift. I know that stock specs are 5.5 BS and 25mm offset. The closest match that I could find was this:
20x8.5, 6 on 5.5 / Bolt Pattern; Back Spacing = 5.14 in.; Offset = 10 mm.; Hub Bore = 108
Is this good or am I completely off?
*Is the Hub Bore too big? *How far will these stick out?
The brand and size of the tire will also make a big difference. The Toyo MT LT35x12.5x20 is 13" wide on their spec sheet. If I was going to run that tire, at least on the spec sheet measuring rim ... (it was either 9.5" or 10"), then I would definitely want less backspacing for more spindle clearance, like a 4.75" or a 4.5".
But with less backspacing the front tires will rub more on the fender at the pinch weld, when cranking the steering wheel But the Pinch weld mod looks like an easy way to deal with it. As far as, how far they will stick out ... since they are an 8.5" rim, an extra 1/2" over the 8" if the same backspacing, but with 5.14" b.s., that's about another 3/8", so 7/8 of an inch more for the outside of the rim. Plus the tire's width. [Remember too that rims are about an inch wider than what the nominal width is, but can vary between manufacturers. So a OEM 8" rim might measure 9", and an aftermarket 8.5" rim might be 9.25" or 9.75"].
The hub is about 3" so if there is an option for that, like a 78.1, it might be better. But a lug centric wheel with the proper lug centric lug nuts should work. Seems like a hub centric would be stronger though, so maybe check with the seller.
If the tire model and size is known, this will help too. If there is anyone out there with a 4" spindle lift plus 2.5" PRG level kit that can list their wheel and tire information and if they clear the spindles or needed a wheel spacer, we could probably figure out if yours will clear for sure. Another option is to test fit at a brick and mortar tire shop.