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[jb2178]

As some of you may know I'm running my 128i sport in my regions scca D Stock class this season and it's been a blast but a few weeks back I went to an AutoX school and toasted one front tire. I'm thinking about ditching my run flats for better tires but I had a few questions. I should be able to upgrade to 18's since that was an optional wheel but I'm curious what my options for just replacing my run flats and keeping my 17s are. I know they are heavy but I'll have a much easier time convincing the wife if I'm only spending $500 on tires instead of $1800 on Breytons.

1. Can I run 215 or 225s on the front 7 inch wide wheel? Can I run 235 or 245 rears on the 7.5 inch wide wheel?

2. Does anybody know of a good autocross setup 1 series that would still keep me in the stock class?

3. Any street tire recommendations out there from fellow cone killers? I know hoosiers and r comp tires would be best but if I don't buy new wheels for sundays then the tires will see daily use.

Thanks for the help

[axoid]

My advice is to stay on 17s and fit 225 all around. With wheels being equal, 17s will be lighter than 18s with the 128 less torque and 225 all around should allow the car to rotate better that if you put wider tires on the rear.

Get the stickiest tire you can afford/justify.

When I autoxed my 128 with the RFTs, I ended up running 35/45 psi front rear to get the car to rotate.

[Artmasterx]

I currently run a 235/40 17 setup for autoX, but it is on some older 17x8 wheels. I am running Goodyear GS-D3 tires, but they aren't the best for autoX.

I think many people here would suggest the Dunlop Star spec if you want a great autoX tire.

Also, I just toasted one of my stock front tires hitting a pothole and put 225/45 17s all around. So 225 can definitely fit up front, and they look fine in my opinion. If you wanted to, you could probably run a 235/45 17 on the rear 7.5" wheels, and the tire diameter would be less than a 1/2" difference to the front 225/45s.

[nordique14]

The profile of the tires also makes a difference. Go to the tirerack site and look at a tire. There will be a Specs tab. It will list the rim width for each tire size. Very interesting info. For example, with the Bridgestone RE-11 tires (a good street autox tire):
235/40R17 fits rims 8-9.5" while the 235/45R17 fits rims 7.5-9".
245/40R17 fits rims 8-9.5" while the 245/45R17 fits rims 7.5-9".

You should probably read this:
http://www.tirerack.com/tires/tirete...#rimwidthrange

[jb2178]

Originally Posted by Artmasterx

I think many people here would suggest the Dunlop Star spec if you want a great autoX tire.

Not to start a neverending forum battle of opinions but based on my choices would you still recommend the Dunlops?

Dunlops: 235 $135/225 $129
Kumho MX: 235 $130/225 $116
Kumho XS: 235 $131/225 $122

Dunlops: Staggered $538/Non $516
MX: Staggered $492/Non $464
XS: Staggered $506/Non $488

I'm leaning towards going with a staggered setup at the risk of some understeer. I'll get my alignment set first and see what kind of difference I can get from that.

Thanks

[ben14142001]

I've heard only good things about the Star Specs.

[Artmasterx]

I am sure that there is a better possibility of you kicking yourself for not spending the extra $50 to get the Dunlops than there is you being happy that you didn't.

I am not an expert, but adding negative camber can certainly give you significantly more grip up front, at the expense of potentially uneven tire wear. There are people on the forum that can give you great advice on camber, I am not one of them.

I would say that if you are money-conscious, you could skip the alignment and see how the tires do without it. Do camber changes affect the SCCA class you would be in?

[axoid]

Originally Posted by Artmasterx

I would say that if you are money-conscious, you could skip the alignment and see how the tires do without it. Do camber changes affect the SCCA class you would be in?

No, as long as it is with in the factory adjustability.

[dereknmmi]

What's the difference between a staggered setup and a non staggered setup. I've never heard of that before.
Thanks

[BrokenVert]

Originally Posted by dereknmmi

What's the difference between a staggered setup and a non staggered setup. I've never heard of that before.
Thanks

A staggared setup has a larger tire size in the rear than in the front. Like on your 135i. This works for cars with higher power output because you have more rubber in the rear. This adds to a car's overstear problems, so a square set up (all tires the same size) is more desireable for Auto-X

Also, my vote goes in for PS2s. I have em on my vert and the grip is phenominal.

[Artmasterx]

Just to clarify the above post. Staggered is wider tires/wheels in the back than in the front. Generally the tire diameters in the front and back are kept as close as possible.

[jb2178]

Well after yesterday's autocross (and crossing 20,000 miles) my rear run flats are more like slicks so I took that to mean I should bite the bullet and order some tires:
Front:
225/45ZR17 Dunlop Direzza Sport Z1 Star Spec
Rear:
235/45ZR17 Dunlop Direzza Sport Z1 Star Spec

Also picked up some new tires for the wife's subaru:
205/55R16 Bridgestone Potenza RE960AS Pole Position

Hopefully the Dunlops and getting closer to a non-staggered setup will help at the next event. Thanks for the help making the decision.

[jb2178]

I don't know if it qualifies as my first performance mod but I do feel like it should.

For those 128i's out there who hate there runflats let me suggest upgrading to the Dunlop Star Specs!

I just got home after the change at Europian Auto Garage (good people if you are in East Tennessee and want a shop http://www.europeanautogarage.com/) after they swapped the rubber on my 2008 128i sport and did an oil change. In case you missed it in passed posts, my opinion is to thank BMW for giving you ever third oil change for free and pay for the two in between (and of course change that oil after break-in).

I upgraded to 225/45/17s on the font and 235/45/17s on the rear. Dunlop Direzza Sport Z1 Star Specs. I didn't bother with new rims as I'm autocrossing and want to remain in D-Stock until my driving improves. We'll see at my next event, no more blaming my bad driving on run flats.

I was a little worries the 225s up front would be too wide nd possibly appear wider then the wheel and give you that "balloon" tire look but after the 50 series tire that was on it I'm extremely happy. I took her for a spirited drive over some mountain roads coming home and I'm excited to get back on the AutoX and try them out, the car obviously has more rubber on it now and the grip feels greatly improved.

I realize I might get boo'd for not buying a 135 or not putting 19s on my car but I spent a total of $560 on tires and $85 to get them installed on my $33,500 BMW and that's fine with me.

Photos (first two are the last photos of my car will with run flats on it, ever):