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Old 11-13-2005, 11:44 AM   #1
Legacy
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Default How much of a difference between 16-17 wheels for auto-x ?

I'm running a MY97 Legacy GT Wagon and looking at getting some wheels for auto-x. Typically "smaller is better" as the smaller the wheel, the less it weighs. I want to run 16x7 or 17x7, lets say I found 17's that are only a pound or two heavier than the 16's. On an auto-x course HOW much of a difference does it really make ?

Much like a tire comparison, has anyone like "Grassroots Magazine" done a comparison with back to back runs on different size wheels ?
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Old 11-13-2005, 12:58 PM   #2
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Remember to factor in the weight of the tires. They're rotating mass too. Tires for a 16" wheel will be different than tires for a 17" wheel.
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Old 11-13-2005, 02:05 PM   #3
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Yes that is certainly relevant as well. Still looking for an answer.
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Old 11-13-2005, 02:36 PM   #4
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Right now...there are more favorable sizes for tires in 17" than in 16". You can get into xxx 40 17 series tires that weigh about the same, are smaller in overall dia. and handle just as well as a comperable 16" size.


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Old 11-13-2005, 06:54 PM   #5
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GRM have done two articles in the last couple of years dealing with wheel sizes. Can't place my hands on the specific issues right now however. You will likely have better tire choice in 17", 16" will always be cheaper though. If you want to run stock class you can't change from the oem size other than offset. You will not likely notice a time impovement autocrossing, only big difference is going from street tires to R compounds.
I wish I could find the most recent GRM article, I think they did a nissan sentra on the track with 15-18 wheels, was a good article, I think the smaller wheels were faster but harder to drive. Don't quote me though....
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Old 11-13-2005, 06:59 PM   #6
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Important question: R-compounds or streets?
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Old 11-13-2005, 08:05 PM   #7
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16's with a 40 series tire will give you higher gearing resulting in having to shift into 3rd gear during a race.

Heres what 205/40/16 RT-615's on Stock 16in RS wheels


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Old 11-13-2005, 09:10 PM   #8
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Quote:
Originally Posted by Whiteghost 2.5
16's with a 40 series tire will give you higher gearing resulting in having to shift into 3rd gear during a race.
Josh
That's just your choice in tire, not because you have a 16" rim. Lots of selection in 225,50,16 which will have practically zero effect on ratio's. Actually 205,40,16 is a real hard size to find, nothing on TR in competition tires.
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Old 11-14-2005, 12:32 AM   #9
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And I'll say it again, 205/45/16 or 215/40/16 is not enough tire (load capacity wise) for our cars. You'll also have to watch the low profile 17's for the same problem I would not go below the factory specified load carrying capacity (89?) with a tire that I was going to flog mercilessly.

Andy H.
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Old 11-14-2005, 08:54 PM   #10
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Quote:
Originally Posted by KC
Important question: R-compounds or streets?
R's baby ! I don't see the point in auto-x'ing with anythign else if I'm buying new tires in the first place. I would be interested in reading a report on size even if it was done on street tires.


Quote:
Originally Posted by adhowe70
And I'll say it again, 205/45/16 or 215/40/16 is not enough tire (load capacity wise) for our cars. You'll also have to watch the low profile 17's for the same problem I would not go below the factory specified load carrying capacity (89?) with a tire that I was going to flog mercilessly.

Andy H.
Can you explain a little more Andy ? Are you saying some tires cannot handle the load (weight?) of our cars ? How would I know which tires will and will not handle the load ?
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Old 11-14-2005, 09:39 PM   #11
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What I experienced was the sidewall of the outside front tire buckling when turning into a corner. I experienced this with a 205/45/16 tire on a 2.5RS. Nothing catastrophic, just horrible tire wear and far less than optimum grip.

To see the tire's load carrying capacity, look at the last part of the size specification. For example, my OEM RE92's were labeled "205/55/R16 89V" The "89" indicates the load carrying capacity of the tire. Its code for something but basically the higher the number the higher the load capacity. Incidentally, the "V" is the speed rating of the tire.

So, look at the recommended tire size and load capacity in the owner's manual of your car. Buy a tire with at least that load capacity. Have fun! If you do go marginally below that recommended capacity, make sure you run a lot of air in the front tires to keep them supported. The higher the air pressure the higher the load capacity of the tire.

Andy H.
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Old 11-14-2005, 09:44 PM   #12
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Info about load ratings, http://www.tirerack.com/tires/tirete....jsp?techid=35

Remember this is for static loading per corner. Most subaru's especially on R's are going to be doing over .9g's so a significant portion or the vehicle wieght is going to be on the outside tires, even more so front or rear if there is acceleration or braking taking affect.
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Old 11-14-2005, 10:33 PM   #13
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Go with the 16s, for the gearing. Low profile and AWD does wonders. Since there's so much drivetrain loss in the Subaru, when you can lower some gearing with lower profile tires, you'll get more 'pull' out of slower corners.

16 x 7 with V710s in 215/40-16. These are light at 19lbs (reduce unsprung weight), and offer an excellent gearing advantage over stock dia. That's what I'd do.

--kC
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Old 11-14-2005, 10:50 PM   #14
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Run a lot of air in that tire KC! At least the 51psi max pressure.

I'd choose the 225/50/16 V710.
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Old 11-14-2005, 11:23 PM   #15
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Didn't that GRM article find that 17" wheels were a good compromise between the light weight 16" wheels and the heavier 18" wheels? 17" wheels allowed stiffer side walled tires.

Of course class rules might decide for you which size wheel you have to use ...
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Old 11-15-2005, 08:01 AM   #16
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Quote:
Originally Posted by adhowe70
Run a lot of air in that tire KC! At least the 51psi max pressure.

I'd choose the 225/50/16 V710.
Over the past 4-5 years of people autoxing on the 215s, I have yet to hear of any problems on any Subarus. I agree with Andy.. don't underinflate them... I know people that ran 60psi in them in the rear solely for rotation in their old '02.... but run pressures where the tire says you need them (tire temps vs. scrub) in the front.

It's a fast tire on a Subaru... turbo or non-turbo, and is at least 1 second faster than the 225/50-16s on a 60 second course.

--kC
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Old 11-15-2005, 10:10 AM   #17
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Just shows there's more than one way to skin a cat!

For what its worth, the gearing "advantage" of the smaller tire on a 2.5RS isn't an advantage. Our gearing is so short that the 215/40/16 won't even get us to 50mph in second gear. That's why I choose the 225/50/16. That and a bad experience with 205/45/16 Ecsta V700's.
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Old 11-15-2005, 10:25 AM   #18
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Ecsta V700 != V710s!!!!

V710s are light years ahead of the Ecsta V700s... heck, even Victoracers are better than the Ecsta V700s.

I think the '97 Legacy (which the OP drives) has different gearing than the 2.5RS. Not toally sure, but cannot find top speed in 2nd... maybe Pat Olsen might now....

--kC

Last edited by KC; 11-15-2005 at 10:31 AM.
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Old 11-15-2005, 11:36 AM   #19
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Quote:
Originally Posted by KC

I think the '97 Legacy (which the OP drives) has different gearing than the 2.5RS. Not toally sure, but cannot find top speed in 2nd... maybe Pat Olsen might now....

I really don't know my gear ratios yet. The only details about gearing I can tell you is 3rd gear tops out about 125km (75mph)and 4th tops out around 140km (85mph). How do I know if I have a 4.11 or 4.44 rear end ? Or, what the rest of my gearing is for that matter ? I don't think the owners manual has the info
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Old 11-15-2005, 12:54 PM   #20
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WHat does 2nd top out at in your legacy? That's the big question for auto-x.

Last edited by KC; 11-15-2005 at 01:00 PM.
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Old 11-15-2005, 01:08 PM   #21
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I have a 92 leg with fwd and it tops out at 62 or 63 mph. Its n/a with the 2.2L. 5 speed. Dont know if thats relevant or not?
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Old 11-15-2005, 01:44 PM   #22
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FYI guys, I run 30 psi in my 225/50/16 710's. I can tell you right now that not much higher pressures will be needed for any surface.

The 215 will be too narrow, especially for a legacy.
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Old 11-15-2005, 02:13 PM   #23
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Quote:
Originally Posted by ratt_finkel
FYI guys, I run 30 psi in my 225/50/16 710's. I can tell you right now that not much higher pressures will be needed for any surface.

The 215 will be too narrow, especially for a legacy.
Gearing trumps width.
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Old 11-15-2005, 02:23 PM   #24
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Quote:
Originally Posted by KC
WHat does 2nd top out at in your legacy? That's the big question for auto-x.

Can't remember off the top of my head. You'll have to wait until after work
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Old 11-15-2005, 02:32 PM   #25
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I don't know about the Legover, but I run 215/40R16 (iirc) on RS wheels on my WRX, and it feels fantastic, much better than 225/45R17. The gearing difference is huge, much larger than you would expect.
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