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Tire size recommendation for 18x10 rear

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Old 12-22-2016, 06:45 PM
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Bill Verburg
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there are 3 primary tarmac driving world w/ wildly different needs in each.

world 1 is summer street
world 2 is big track
world 3 is A/X

street is most forgiving there is a huge variation it what is ok

big track tends to want neutral to very minor oversteer at speed which will be a major understeerer at A/X speeds

A/X tends to want oversteer which will be pretty uncomfortable at track speeds
Old 12-22-2016, 10:58 PM
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GBX
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Originally Posted by Bill Verburg
there are 3 primary tarmac driving world w/ wildly different needs in each.

world 1 is summer street
world 2 is big track
world 3 is A/X

street is most forgiving there is a huge variation it what is ok

big track tends to want neutral to very minor oversteer at speed which will be a major understeerer at A/X speeds

A/X tends to want oversteer which will be pretty uncomfortable at track speeds
So, what do we recommend on tires sizes for world 1 - summer street?

Just picked up a set of Fikse FM10's spec' as follows:
18x8 ET50
18x10 ET60

225, 265 or should I push the envelope to 235, 275 or 285s? Car is lowered on kw v3's
Old 12-22-2016, 11:33 PM
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tian647
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I will say that for World 3 one does not want a 225/275 combo as there is an enormous amount of understeer and nowhere near enough power to overcome the rear traction and help it turn.

My setup was Bilstein B8s and M030 springs with RE-11As on Carrera IIIs in 8/10x18. Feels great at a DE, induces unhealthy frustration levels trying to backside a tight slalom



Next year will see me run 245/275 RE-71s, or a Corvette because they just effin work.


Christian
'95 Carrera
Thanks J. Douglas Patterson/Patterson Prints LLP for the astounding camera work!
Old 12-23-2016, 12:07 AM
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SleepRM3
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Default 225/40-18, 265/35-18 for 8 and 10 x 18 Fikse FM-10s

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Old 12-23-2016, 12:35 AM
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Default Tire model category and overall diameter differences front/rear might be a concern?

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Old 12-23-2016, 03:06 AM
  #66  
Bill Verburg
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Originally Posted by GBX
So, what do we recommend on tires sizes for world 1 - summer street?

Just picked up a set of Fikse FM10's spec' as follows:
18x8 ET50
18x10 ET60

225, 265 or should I push the envelope to 235, 275 or 285s? Car is lowered on kw v3's
I'd use 225/40 & 265/35 x18 as the most neutral w/ ok gearing effect

if you want a meatier look 235/40 & 275/30, cost is a little worse gearing

if you want a tad better gearing 235/40 & 285/30

as I said world 1 has a wide range of ok
Old 12-23-2016, 03:13 AM
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Bill Verburg
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Originally Posted by tian647
I will say that for World 3 one does not want a 225/275 combo as there is an enormous amount of understeer and nowhere near enough power to overcome the rear traction and help it turn.

My setup was Bilstein B8s and M030 springs with RE-11As on Carrera IIIs in 8/10x18. Feels great at a DE, induces unhealthy frustration levels trying to backside a tight slalom



Next year will see me run 245/275 RE-71s, or a Corvette because they just effin work.


Christian
'95 Carrera
Thanks J. Douglas Patterson/Patterson Prints LLP for the astounding camera work!
correct for a/x wider front wheel and tire is wanted relative to stock 8 225/40 & 10 265/35. 235/ or 245/ in front but the wider tire still wants a wider wheel, I currently use an 8.5 front and have used 9s there in the past. Even for big track use this is desireable as a stock 993 understeers a lot. You also want a shorter side wall, 225/40 will be better than 235/45 on an 8. Stiffer rear sway and springs also increases oversteer
Old 12-23-2016, 03:32 AM
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Originally Posted by tian647
I will say that for World 3 one does not want a 225/275 combo as there is an enormous amount of understeer and nowhere near enough power to overcome the rear traction and help it turn.

My setup was Bilstein B8s and M030 springs with RE-11As on Carrera IIIs in 8/10x18. Feels great at a DE, induces unhealthy frustration levels trying to backside a tight slalom

You know what I started yelling at my students instead of "look ahead"? "Look up!". Actually, proved to be pretty effective
Old 12-23-2016, 09:55 AM
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Originally Posted by nile13
You know what I started yelling at my students instead of "look ahead"? "Look up!". Actually, proved to be pretty effective
Heh, I am looking up! It's just lost as the gun'ls come surging up amidst all that body roll.

That remains a perennial struggle of mine, keeping my vision focused far enough ahead to plan rather than react.


Christian
'95 Carrera
Old 12-23-2016, 11:25 AM
  #70  
Mark in Baltimore
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Where you look is where you'll go. Also, it helps to set up at least two corners in advance, especially for any corner that leads to a long straight (to get on the power as early as possible).
Old 12-23-2016, 02:07 PM
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Originally Posted by tian647
Heh, I am looking up! It's just lost as the gun'ls come surging up amidst all that body roll.

That remains a perennial struggle of mine, keeping my vision focused far enough ahead to plan rather than react.
That's 80-90% of success at autocross. I literally yell out loud at myself during the runs when I remember to look ahead. The two things I yell is "look ahead" and "turn earlier".

The problem is, being busy you often forget those things. I usually forget to breath and have to remind myself mid-run, and we run long 70+ second courses. It's easier when instructing, I remember and yell on every run
Old 12-23-2016, 02:09 PM
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Originally Posted by Mark in Baltimore
Where you look is where you'll go. Also, it helps to set up at least two corners in advance, especially for any corner that leads to a long straight (to get on the power as early as possible).
Long straights? We don't have no stinking long straights (to almost quote Mel Brooks).
Old 12-23-2016, 02:30 PM
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Originally Posted by nile13
Long straights? We don't have no stinking long straights (to almost quote Mel Brooks).
Well, I guess it's relative. When I used to autocross (in the NSA's parking lot, for crying out loud. No more.), the organizers made the course with decent straights where you could floor it for five seconds or more.
Old 12-23-2016, 03:11 PM
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Originally Posted by Mark in Baltimore
Well, I guess it's relative. When I used to autocross (in the NSA's parking lot, for crying out loud. No more.), the organizers made the course with decent straights where you could floor it for five seconds or more.
Wow. We run at an old airfield, and 5 seconds on the gas would be... well one of two PCA clubs used to do that, but running towards the top of 3rd gear in a Miata was outright scary and I've stopped going. They've changed course designers since, but I remember the sickening feeling of trying to slalom at 80 mph and not being able to bring the car back by just slight lift like I'm used to in 2nd. the old course designer would actually outright say: "We are trying to make a mini-track event here". Of course, some people really liked it. Just not my thing. I love convoluted technical courses that is what we mostly run locally.

One secret I've been tough early on is that at autocross, if you find or make a long enough curve, that's your acceleration line. So now I'm looking for long curves, whether they are there or whether I can create them. To me, that's actually one of the largest differences between autocross and track.
Old 12-23-2016, 06:45 PM
  #75  
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Originally Posted by Bill Verburg
I'd use 225/40 & 265/35 x18 as the most neutral w/ ok gearing effect

if you want a meatier look 235/40 & 275/30, cost is a little worse gearing

if you want a tad better gearing 235/40 & 285/30

as I said world 1 has a wide range of ok
good info! thanks Bill. So does 225/40 & 265/35 x18 or 235/40 & 285/30 maintain better gearing?

Last edited by GBX; 12-24-2016 at 09:19 AM.


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