Mixed tires for Autocross?

thothtp · 04-30-2013, 12:16 PM

So I have a stock class 135i (m3 front sway, Koni yellows, Stock size wheels) that I am autocrossing and daily driving, same tires.

Was using Pilot Super Sports. My front tires (235/40/18s) still have about 40% life, my rear tires (255/35/18) are shot. I need to replace the rears, but don't really want to replace all 4.

Option 1 - Replace the rears with new 255 PSSs

Option 2 - Replace rears with 245 or 235 PSSs for less rear grip and better balance

Option 3 - Buy Direzza ZIIs (or another type if there are any better) and mount them on the front, then mount the 235 PSSs in the rear.

Which option would you suggest for the best autocross results while still being daily driveable?

vantagesc · 04-30-2013, 12:30 PM

Most people will say not to use different tire compounds on the front and rear axles. A professional driver drove a buddy's car that had different tires and he said the car was a bit unpredictable/odd at times because of the different tires. Obviously it's possible to drive like this and in normal driving it may not make a difference, but I wouldn't do it.

I'd go with Option 1. Direzzas or Hankook RS3s would be faster (and wear out more quickly), but you can buy four of those during the next tire change.

Re Option 2, balance is nice to have, but in theory you'll always be faster with more total grip.

Qbrozen · 05-02-2013, 09:32 AM

A couple days late, but another option is to watch Ebay for slightly used super sports. I've been saving quite a bit of $$ buying slightly used tires off Ebay for all my cars.

first350 · 05-02-2013, 02:28 PM

Quote:

Originally Posted by Qbrozen

A couple days late, but another option is to watch Ebay for slightly used super sports. I've been saving quite a bit of $$ buying slightly used tires off Ebay for all my cars.

+1. there's also online companies that sell used tires...just be careful b/c some used tires are off cars that were totaled in an accident; I've had friends receive tires with badly damaged sidewalls that wouldn't be safe to mount.

Kgolf31 · 05-02-2013, 02:49 PM

Replace with like tires in the rear.

If you go ZIIs in the rear, you'll have too much grip in the rear and not enough in the front and you'll plow and understeer like no other...or vice versa

blutattoo · 05-02-2013, 03:11 PM

Quote:

Originally Posted by Qbrozen

A couple days late, but another option is to watch Ebay for slightly used super sports. I've been saving quite a bit of $$ buying slightly used tires off Ebay for all my cars.

+2 I had the opposite happen wore thru my PSS's in the front but the rears had life left so I just bought used ones off ebay for the front at a fraction of the cost of new.

Sven_Mueller · 05-11-2013, 07:08 AM

Hi thothtp,

regarding your235/40r18 front- are you using any wheel spacers? If yes which size?
I am planning on running 235/40r18f and 255/35R18r Dunlop Z2. The wheels are the stock M package wheels.
Thanks!

PS: A Mercedes driver at our last Autox event had Rivas in the front and All season tires in the rear. He did really good.

04-30-2013, 12:16 PM	#1
thothtp Enlisted Member 6 Rep 39 Posts Drives: 2007 BMW 328i Join Date: Sep 2007 Location: Rochester, NY iTrader: (0)	Mixed tires for Autocross? So I have a stock class 135i (m3 front sway, Koni yellows, Stock size wheels) that I am autocrossing and daily driving, same tires. Was using Pilot Super Sports. My front tires (235/40/18s) still have about 40% life, my rear tires (255/35/18) are shot. I need to replace the rears, but don't really want to replace all 4. Option 1 - Replace the rears with new 255 PSSs Option 2 - Replace rears with 245 or 235 PSSs for less rear grip and better balance Option 3 - Buy Direzza ZIIs (or another type if there are any better) and mount them on the front, then mount the 235 PSSs in the rear. Which option would you suggest for the best autocross results while still being daily driveable?
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04-30-2013, 12:30 PM	#2
vantagesc First Lieutenant 45 Rep 365 Posts Drives: BMW Join Date: Mar 2011 Location: USA iTrader: (0)	Most people will say not to use different tire compounds on the front and rear axles. A professional driver drove a buddy's car that had different tires and he said the car was a bit unpredictable/odd at times because of the different tires. Obviously it's possible to drive like this and in normal driving it may not make a difference, but I wouldn't do it. I'd go with Option 1. Direzzas or Hankook RS3s would be faster (and wear out more quickly), but you can buy four of those during the next tire change. Re Option 2, balance is nice to have, but in theory you'll always be faster with more total grip.
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05-02-2013, 09:32 AM	#3
Qbrozen Private First Class 11 Rep 167 Posts Drives: 2008 135i Join Date: Dec 2011 Location: Jackson, NJ iTrader: (1)	A couple days late, but another option is to watch Ebay for slightly used super sports. I've been saving quite a bit of $$ buying slightly used tires off Ebay for all my cars. __________________ '08 135i auto, premium, sport: JB4, BMS DCI, dinan camber plates, OBX DPs, custom oil cooler.
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05-02-2013, 02:49 PM	#5
Kgolf31 Brigadier General 459 Rep 4,531 Posts Drives: 2007 Z4MC, 2012 128i Join Date: Sep 2008 Location: Ohio iTrader: (4)	Replace with like tires in the rear. If you go ZIIs in the rear, you'll have too much grip in the rear and not enough in the front and you'll plow and understeer like no other...or vice versa
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05-11-2013, 07:08 AM	#7
Sven_Mueller New Member 1 Rep 13 Posts Drives: 2011 BMW 135i Join Date: Aug 2012 Location: Saint Paul iTrader: (0)	A question regarding your current tires Hi thothtp, regarding your235/40r18 front- are you using any wheel spacers? If yes which size? I am planning on running 235/40r18f and 255/35R18r Dunlop Z2. The wheels are the stock M package wheels. Thanks! PS: A Mercedes driver at our last Autox event had Rivas in the front and All season tires in the rear. He did really good.
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