rallycross tyre width question

pjhe · 08-24-2007, 11:27 AM

background: 05 sti rallycrossed on clay, gravel and dirt surfaces which are primarily dry to very dry, occasionally there is a rare mud puddle but never wide event that you can't take a line around it.

current tyre size: 225-45R17 nokian happailietta RSI. I'm looking at some tyre replacement options and one of the options is available in the 225, 235 and even a 245 width. all of which will fit on the wheels and clear my fenders.

so is the wider patch a good thing on dirt in the same manner it is on tarmac? would the added sidewall height rise my debeading risk a lot or make for more sidewall flex for dimenished turn in response?

looking for some people to weigh in on this (fred, orion, christian). I really wish i had the coin and stones to pull the swap to group n brakes and get proper 15" wheels...
maybe in a year or 2 but whatever rubebr i get in the next month should hold me over til then

Orion · 08-24-2007, 02:43 PM

i've got 205 Kumhos and 215 Falken gravels. i've run some 195 snows and 205 ContiExtreme Contact all seasons, but i can't say there was really any way to compare all 4 based on width as conditions varied greatly.

obviously on a loose surface (like the outside of turns at OA) a narrower tire will get to the bottom of it sooner, but in the areas of hardpack (inside of turns at OA) you'd want darn near a 245 premium summer tire (Azenis 615, Kook RS-2, etc)!

pjhe · 08-24-2007, 02:59 PM

i know i'm so torn esp with the fact that a lot of the events are going to be at summit now
and what would likely be best at hastings?
the tyres i'm looking at are snows, with a good aggressive centre section but the shoulders are more closed off then the nokian rsi's are (longer life but i am concerns about grip in loose stuff because of that)

and of course ideally i want to be rotating on the inside line (yeah i WISH i was anywhere near that good)

remowgn · 08-24-2007, 03:06 PM

Quote:

Originally Posted by pjhe

I really wish i had the coin and stones to pull the swap to group n brakes and get proper 15" wheels...

If you're willing to go with something other than the super spendy group n brakes, TCE has a decent wilwood kit that will allow you to run 15" wheels. You'd only need to do the fronts obviously, and Todd at TCE can get you set up with the proper front calipers to maintain the right brake balance with the STI rears. I have the full kit on my WRX, and it's quite nice. The aluminum calipers and rotor hats drop a TON of weight.

http://www.tceperformanceproducts.co...s.pl?record=19

pjhe · 08-24-2007, 03:27 PM

hmm in 5x114.3 that would certainly be an option. I'm going to have to test fit some 15"s on the rear and the grp n frts aren't too bad price wise, but i think the brembo rears still might not clear 15"s in the back

Fred · 08-25-2007, 08:08 AM

The 2000 2.5RS stock wheels won't even fit back there. I'd love to see a 15" wheel that would fit.

If I was stuck with stock wheels, I'd try 225/50/17 with a very stiff sidewall and very aggressive tread pattern, whatever tire that ends up being.

You're really handicapped with the STi, though - so the biggest thing will be removing as much weight as you can, modulating the throttle and focusing on running the shortest line possible with no mistakes.

08-24-2007, 11:27 AM	#1
pjhe Scooby Specialist Member#: 81725 Join Date: Feb 2005 Chapter/Region: MAIC Vehicle: 73 zcar amidst ls2 swap	rallycross tyre width question background: 05 sti rallycrossed on clay, gravel and dirt surfaces which are primarily dry to very dry, occasionally there is a rare mud puddle but never wide event that you can't take a line around it. current tyre size: 225-45R17 nokian happailietta RSI. I'm looking at some tyre replacement options and one of the options is available in the 225, 235 and even a 245 width. all of which will fit on the wheels and clear my fenders. so is the wider patch a good thing on dirt in the same manner it is on tarmac? would the added sidewall height rise my debeading risk a lot or make for more sidewall flex for dimenished turn in response? looking for some people to weigh in on this (fred, orion, christian). I really wish i had the coin and stones to pull the swap to group n brakes and get proper 15" wheels... maybe in a year or 2 but whatever rubebr i get in the next month should hold me over til then

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08-24-2007, 02:43 PM	#2
Orion Got the F out Moderator Member#: 4797 Join Date: Mar 2001 Chapter/Region: MWSOC Location: central ohio Vehicle: 01 01 RS, 00 RS 2008 WRB FSXT 5mt	i've got 205 Kumhos and 215 Falken gravels. i've run some 195 snows and 205 ContiExtreme Contact all seasons, but i can't say there was really any way to compare all 4 based on width as conditions varied greatly. obviously on a loose surface (like the outside of turns at OA) a narrower tire will get to the bottom of it sooner, but in the areas of hardpack (inside of turns at OA) you'd want darn near a 245 premium summer tire (Azenis 615, Kook RS-2, etc)!

08-24-2007, 02:59 PM	#3
pjhe Scooby Specialist Member#: 81725 Join Date: Feb 2005 Chapter/Region: MAIC Vehicle: 73 zcar amidst ls2 swap	i know i'm so torn esp with the fact that a lot of the events are going to be at summit now and what would likely be best at hastings? the tyres i'm looking at are snows, with a good aggressive centre section but the shoulders are more closed off then the nokian rsi's are (longer life but i am concerns about grip in loose stuff because of that) and of course ideally i want to be rotating on the inside line (yeah i WISH i was anywhere near that good)

08-24-2007, 03:27 PM	#5
pjhe Scooby Specialist Member#: 81725 Join Date: Feb 2005 Chapter/Region: MAIC Vehicle: 73 zcar amidst ls2 swap	hmm in 5x114.3 that would certainly be an option. I'm going to have to test fit some 15"s on the rear and the grp n frts aren't too bad price wise, but i think the brembo rears still might not clear 15"s in the back

08-25-2007, 08:08 AM	#6
Fred Scooby Guru Member#: 3560 Join Date: Jan 2001 Chapter/Region: South East Location: Four Oaks, NC Vehicle: 06 STi, 98RS wagon 94 Open Light 2.5RS	The 2000 2.5RS stock wheels won't even fit back there. I'd love to see a 15" wheel that would fit. If I was stuck with stock wheels, I'd try 225/50/17 with a very stiff sidewall and very aggressive tread pattern, whatever tire that ends up being. You're really handicapped with the STi, though - so the biggest thing will be removing as much weight as you can, modulating the throttle and focusing on running the shortest line possible with no mistakes.