Recently installed some camber arms and springs/shocks. I have a set of 17x10 sitting in my garage and planning to get 255/40 tires for DEs. My car is mainly for DE/autoX now that I have a DD for commute. Should I wait til I get the tires and put the new rims to go for an alignment? Or getting the alignment with OEM rims/tires now? The reason I asked is b/c there's some diameter/circumference differences between the 2 set and I'm not sure if the difference is significant enough that would have an effect on the alignment.

I plan to drive to/from events with my OEMs and switch them to my 17s once I get there, but if I can't find a way to stuff all 4 tires in the Z then I'll have to drive the 17s to/from events.

Here's the info from 1010tires.com

225/45/18
overall dia: 25.97in
circumference: 81.58in

245/45/18
overall dia: 26.68in
circumference: 83.81in

255/40/17
overall dia: 25.03in
circumference: 78.63in

Ideally, 275/40/17 would be best matched to the OEM sizes. But since my car isnt that powerful (only have MREV2+spacer) and the price difference in 255 vs 275, I don't see the need to go with 275. Plus seems like 255/40 has more tire selections, at least from tirerack.

What do you guys think? Any help is appreciated!!!

Thanks!

 

Go 275/40 , they are still shorter than stock and will free up power.

 

Bigger is better, I like the 275s myself, but I ran those on 7.5/8" wheels back when I was running stock autocross class.

 

so then should I get the alignment with my OEMs or wait til I get the 275/40 with my 17s?

What's the advantage of using 275/40 over 255/40 besides the fact it's wider and provide more grip?

 

Advantage is wider, the car weights 3200 pounds and needs the extra rubber. Align with the wheels that will mostly be on the car.

 

I would wait till you get the new tires mounted on your wheels, then get an alignment done.

As for tire selection, wider is better, especially for a porky car like the Z. However, since you are stuck with 17" wheels, your tire selection for the Extreme Performance Catergory (AD08, Star Specs, RE-11, RS3, XS) is pretty limited to a 255 width tire. A 265 and up tire would require 18" wheels to have the same tire selection.

The Kumho XS is the only "extreme" tire that comes in a 275/40/17. I had the XS before, and they were great when the weather conditions were dry and hot but terrible in the rain.

If you plan to replace your tires every 6 months like I do, then get the 255/40/17 tires as they are cheaper and have the best tire selections.

 

Alright, so I've gotta ask.

What the heck does getting new wheels/tires have anything to do with getting an alignment before or after said wheels/tires?

Wheels and tires won't change the alignment, not like changing the suspension would?

 

Changing the wheels/tires don't really have an affect on alignment settings. Only thing I can think of is a slight change in toe, if you decide to change the overall tire diameter. Other than that, I usually get an alignment when I mount new tires to ensure that I get proper wear throughout the tire life. I have actually killed a set of new tires because I didn't check my toe settings.

 

it depends... you're suppose to though... I'll just give you an example if someone got an alignment when their tires had uneven wear... when they get a fresh set of tires the specs of how the car sits will change.

 

Unless they had a 1" tread depth, incredibly stiff sidewalls, and existing alignment problems bad enough to wear one side all the way down without touching the other, I don't see how what's on the car now will affect it later in any meaningful way.

I would (and have on several cars) just align the car with whatever's on it if you're looking to test out some more performance-oriented settings, and get to know your alignment place well. You'll be back at least 3-4 times until you get the settings dialed in for your suspension, tire, track/surface, and style. Make changes to any of the above, and there's a good chance you'll be going back again.

This is just one of the many expenses you have to accept (like wearing through soft tires more quickly than 400-treadwear economy tires) when you're looking to get more out of your car.

 

just an update......... finally settle with getting 275/40/17 Sumitomo HTR Z III. Hoping to get the alignment done this weekend with the new tires/rims. Anyone have any suggestions on alignment settings? I want something that's good for DE/autoX but also wont wear the tires toooooo quickly.

I'm thinking something like this:

Front: -1.5 camber, 1/8" toe-in
Rear: -1 camber, 1/16" toe-in

Will this set-up good for DE/autoX? FYI, I have a set of 17x10 with +25 offset 5Zigens. I've read that it should clear everything, but just want to get 2nd opinions.

thanks!

 

I would bump up the camber a bit. Get the front over -2. If you havn't ordered tires yet, i would reconsider your tire choice.

 

Front: -2.2 w/ 1/8" toe-out
Rear: -1.7 w/ 1/16" toe-in

This should be a good starting point. Depending on driving style, suspension set-up, tire pressures...etc, you might have to change the camber/toe. You won't really know until you get some seat time and start collecting data.

 

So I took my car and have it align to the spec that was listed here. I can see the camber are fairly close to the spec, but can someone help me convert the toe numbers into inches?

Thanks!

 

The tech that did the alignment said I'll need toe bolts to get it to where I want for the rear, he said that's the closest he can get with my current setup.

 

btw, thanks for helping on the specs Clam!

 

No problem! As for the toe conversion, the alignment shop I go to usually does the conversion on their computer when they are trying to adjust the toe settings.

 

You'll be fine fitment wise with that wheel/tire combo. I'm running 17x10 +35 5Zigens with 15/20mm spacers and 275/40/17 Kumho XS for autocross and driving to & from events only. My fitment is perfect right now, and I should be able to go to wider tires in the future by using smaller spacers.

 

dude :-) see you soon at TWS... btw, for texas summer pick kumho XS or nitto NT01 (both available in size you need) right now the nitto are lasting longer than the kumho and are a little faster.

 

I'm planning to go to TWS in June with Porsche club of america, heard they got some great instructors to learn from. hopefully I can get my car ready by then, still need to change out fluids and get some toe bolts.

as far as tires go, well, i already bought a set, so we'll see how that goes. If it sucks, then I can just burnt them by daily driving them. hahahaha