View Full Version : Tire sizes and steering
jamcilvaine Mar 28th, 05, 02:10 PM I have a 1967 rs camaro that is highly modified. It currently has 15x4 volswagon tires on the front and 15x9 wide on the back. I am looking to widen the tires on the front but my car does not have power steering and it is already hard for me to turn it when moving at a slow speed. Do u think that expanding my front tires to 6" will greatly decrease turning ability? I was also told safety was an issue by a guy who works at the tire place because having such a wide tire on the back and skinny in the front because there is so much less rubber on the wheels that are doing the steering. I am also looking for new rims and disappoinetd to find out that the torq thrust II's only come in 8 and 10 inches. I'm pretty sure the 10's will rub with a 15 in rim. Any recommendations for rims or tire sizes? The rear end is from a ford lincoln may cause problems.
jackalope Mar 28th, 05, 03:27 PM Well for the front tires I would go ahead to the wider tire yes it will be harder to turn but you'll get used to it i have 235's manual steering and a tiny little sport wheel and its just a matter of getting used to it.
pdq67 Mar 28th, 05, 04:42 PM A stock, '67 painted steel rim is 14" x 6" with 3.75" offset from the rear. (I still have my five that came new with my car)..
Use a rim that keeps the backside deeper spacing vs a "deep dish reverse" that is wider towards the frontside type rim b/c I almost couldn't parallel park my car with my Fenton Slotted Mags at 14" x 7" with 3.5" b/s rims and E/60-14's!!
And my E/60-14 tires rubbed the wheel well chrome at full droop some b/c they stuck out an 1.25" too much vs right-on for stock, imho...
pdq67
DOUG G Mar 29th, 05, 05:47 AM I have 15x5's w/ 3.5"bs and 205/65/15's on the front. Manual steering,smallblock and a stock steering wheel. No problems unless sitting still. (would hate to parallel park though)
sicsD8 Mar 29th, 05, 11:48 AM Keep in mind that when using cheap VW-size tires in place of true HP frontrunner style tires, the VW tires are designed for much less weight and speed than a race car will be exposing them to. It's not a good place to save money.
jamcilvaine Mar 31st, 05, 12:06 AM Thanks for the feedback guys. i also have a very tiny sport wheel. Question about the back tires now. I have 15x9 right now on the back and cant find any companies that make 15x9 rims. Anyone know of any?
pdq67 Apr 1st, 05, 06:51 PM Heck, I figure either Stockton Wheel or Wheel Vintiques should have them??
pdq67
jamcilvaine Apr 4th, 05, 09:34 PM no one gots em. I think i will have to go down to 8.5
baz67 Apr 5th, 05, 12:48 PM The hard slow speed steering has to do with scrub radius. To reduce scrub you will need deeper backspacing like pdq67 mentioned. On an eight inch rim I would go with at least a 4.5" BS.
Brian
DOUG G Apr 5th, 05, 01:03 PM I have McCreary 285/60/15's (11.5w x 27.5t)on the rear right now. They are tight. I have 15x8's with 4.5"bs.
jamcilvaine Apr 5th, 05, 03:18 PM can someone help me out with scrub radius???
pdq67 Apr 5th, 05, 05:19 PM Scrub radius is the term called that is when your tire foot print isn't centered with respect to the spindle inclination. (Draw a line through your spindle tilted vertically through it's ball joints 'til it hits the ground and then observe how your tire foot print sits on top of the point where it hits the ground)...
In other words, if they don't line up right by hopefully being centered around the point, the tire has to turn more/harder b/c more of it's foot print is not pivoting around the spindle ground intersection point! The tread scrub's off as it turns, hence the term "scrub radius".
How am I doing David?? I ask him b/c he know's a whole bunch more about this stuff then I do is all.
pdq67
baz67 Apr 5th, 05, 07:54 PM pdq67~ if I am reading your post correctly, you are close.
Two imaginary lines define scrub radius. One is the vertical line through the tire center line to the plane of the ground. The other one is the line through the pivot points of the upper and lower BJ to the same ground plane. The most common term for that line is called the kingpin inclenation angle. The distance between the two points on the ground plane is scrub radius. The tire wants to rotate around its center while the car rotates it around the kingpin inclenation. As you can see the more distance between those two points, more scrub radius, the more friction the tire generates so more force is needed to turn the tires. I hope this helps.
Brian
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