Is there any downside to getting 17x11 rims and running 315/35/17 nitto 555r's?

 

Really, I cant think of a downside unless you call clearancing the wheelwells a little a downside.

 

downsides are going to be weight and rolling resistance on the big end. if you are looking for a bit more contact patch on the street, the other tradeoffs hardly matter. if you want a tire to turn ETs then forget a radial tire all together.

JB

 

Gas milege will drop some. I lost over 1mpg by switching from 275 street tires to 315 nitto DR's. Other than that, I don't have any complaints. Also, my rear wheels and tires even weigh less that stock. Ahh, gotta love welds.

 

Heavier=Slower
Shorter Sidewalls=Harsher Ride
Shorter Sidewalls=Less traction at the drag strip.

 

About the sidewalls. What theoretically causes the loss of traction with smaller sidewalls. I just don't see how this could be. This is hard to explain, but in dragsters, I've noticed the slicks' sidewalls flexing (I guess that what its called). Its pretty much that the slicks have so much traction that the wheels spin before the tires. Is this a good thing for traction? I've even seen where the wheel loses grip on the tire and actually spins with out the tire....

Now that I look back at what I typed it makes hardly any sense, but I think I'm grasping the concept, just unable to reproduce it on screen.

 

You want SOME give in the sidewall when on the track because if there is none, it becomes easier to spin the tire. It's a lot easier to bend something that is 6" long than it is something that is 3" long (assuming the same material and same thickness).

With sidewall flex, the tire can "give" a little, allowing your tire to stick to the track without being ripped loose on launch.

Cars that spin the wheel inside the tire and not the tire need bead locks (bolts to hold the tire to the wheel).

 

You use rim screws to keep the tire bead from slipping on the rim.

Another way to think about the sidewall issue.....
As the sidewall ripples, it puts more tread in contact with the pavement. Think of the tire as a rigid cylinder, and only a very small straight line at the tangent (contact) point contacts the road. Allow the tire to deform, and it "plasters" itself to the road forming a large rectangular contact patch... but the sidewall has to be flexible enough to let the tire deform into the larger contact patch.

When you start looking at 315/35-17's you may lose some "length" in the contact patch, because the 315/35-17 sidewall is 1/2" shorter than the 245/50-16 sidewall, but you will gain a lot of tread width to compensate. Net contact patch stays the same or grows.

 

makes sense to me

Thanks for clearing it up. I knew it was better, just didn't know if I knew it for the right reasons...Know what I mean

 

Fred, thanks for the clarification.

I couldn't have DREAMED a better explanation!

But at least I tried...

 

honestly, I would say the possible increased contact patch are going to be overshadowed by the increased unsprung weight in the wheels/tires. a set of 17" wheels/tires are HEAVY. My guess is going from 16's to bigger 17's you won't notice much difference in traction. Its really compound that makes the difference moreso then tire size (I.E. Drag radials Vs street radials)

 

Keith at ws6.com lost something like 3HP when he went from 17x9 275/45 to 17x11 315/35, by widening his stock WS6 wheels.... definitely a big weight increase based on the pictures of the welding. I personally think the issue of large diameter wheels is over-rated... at least with something like comparing a 16" to a 17".

 

This is a very valid point made by a member of SCCA Forums. Remember this is with a constant tire pressure:

"wider tire will not put any more rubber on the ground because as long as the car's weight remains the same the same amount of tire will be in contact with the road. For example (totally made up numbers, here), if a 7-inch wide tire puts a 7x2" patch on the ground, then an 8-inch tire will put an 8x1.75" patch on the ground... no more rubber than before.

I know my examples are super-basic. But I'm sure I've said enough to clarify my question. "

 

Up sides:
1. Looks
2. Bragging rights
3. Less sidewall = better lateral traction (cornering capabilities)

Down sides:
1. More rotational mass = slower
2. Less sidewall give = poorer straighline traction
3. Price of rims
4. Price of tires
5. Possible need for fender clearancing


Traction is found in the compound and sidwall height.. width, while important, is not as important a factor as the aforementioned two. What it all comes down to is simply that you want the sidewall to flex for two reasons..
1. It acts as a shock absorber during a hard launch and allows the tire to stay planted even as the axle and rim begin to move.. If the rim is spinning inside the tire then that problem should definately be remedied via some screws.
2. The sidewall flexing actually allows the tire to change shape and you end up with a larger contact patch as fred stated so eloquently.

If you want traction get some 15" rims and run slicks. If you want a good compromise stick with the stockers - good sidewall height compromise, light weight, and free. If you're looking for traction I suggest you look at the right tire before you go shopping for rims - slicks or drag radials... if anything runing 17X11 rims with the same tires you use now you'll notice a decrease in 60ft times.

My .02

 

I think we need clarification on what he wants to use his car for. I've started AutoXing recently, and the tradoffs from the 17X11s in the rear are well worth the weight I gave up. Lateral grip is awesome now. Also, this wheel tire combo is great on the street. I don't have to worry about spinning whenever I want to apply anything over half throttle.
My lowly little LT1 auto kills off the line because I'm able to launch it almost as aggressively as I'd like. It's all based on your needs. Take all the info listed, and figure out what will work best for you.