BMWCCA Car Control Clinic - Fun (But Now We Need New Tires)

[lucid]

Right, drive around the streets on r-compounds that will hydroplane badly after they lose about 2/32"-3/32" of their 6/32" original thread, which won't take very long. Why do you think they are "just" street legal? Not to mention that you'll need to replace them how often exactly? And one really needs that type of traction on the street...

[jragan]

Originally Posted by ANILE8

Someone mentioned Dunlop DZSPZ1. If you are going to improve your tyres go all the way, why fart arse around and compromise...

Dunlop R Compound DZO2G race tires are far superior. For the fronts I use 245/40/18, and 265/35/18 for the rears. Basically they are a reduced tread depth, stiff side walled, grooved racing slick that is road legal, just. This made the biggest difference to the handling, no surprise there.

After you have driven on a race tire like this you would never want to use a hard as nails road tire again on a performance car.

Only people at the top tier of their run groups should ever consider an R-Compound tire. R-Compound tires are the worst idea ever for trying to teach a driver car control because they stick when the car should otherwise not be sticking and teach drivers bad habits. (This is the same reason the best car control clinics are performed in the rain). I'm in the advanced run group in all the different associations in my area and I still choose to use the Direzza StarSpec because I still have learning to do.

[Finnegan]

Well, there's certainly a lot of learning to do by both drivers of the ///M…

It's looks like Direzza StarSpec's will be going on the car. The only question is front/rear sizing. 245/265 plus some negative camber would seem to dial back the understeer a bit.

Any concerns about the diameter difference on the 265/35/18s being close to 3% (2.81% diameter change) vs. stock 255s? It’s “under the line” but… In theory, one could go up to 275/35/18s on the rear, but that would simply preserve the stock stagger (and some have suggested 275 is too wide for the stock rims).

I totally agree about car control in rainy/wet conditions. Like I said in an earlier post, when I first started driving (many years ago) I’d wait for a good rain and find a large open parking lot. It was a great training experience! I’d love to do that with a more structured program. Trying to find a place to do that on my own is problematic, as sadly, “modern” parking lots are chock full of planters and light poles.

I really appreciate the help/feedback—thanks!

[jragan]

Originally Posted by Finnegan

Well, there's certainly a lot of learning to do by both drivers of the ///M…

It's looks like Direzza StarSpec's will be going on the car. The only question is front/rear sizing. 245/265 plus some negative camber would seem to dial back the understeer a bit.

Any concerns about the diameter difference on the 265/35/18s being close to 3% (2.81% diameter change) vs. stock 255s? It’s “under the line” but… In theory, one could go up to 275/35/18s on the rear, but that would simply preserve the stock stagger (and some have suggested 275 is too wide for the stock rims).

I totally agree about car control in rainy/wet conditions. Like I said in an earlier post, when I first started driving (many years ago) I’d wait for a good rain and find a large open parking lot. It was a great training experience! I’d love to do that with a more structured program. Trying to find a place to do that on my own is problematic, as sadly, “modern” parking lots are chock full of planters and light poles.

I really appreciate the help/feedback—thanks!

The size most of us run on the stock wheels is front:245/40-18 and rear:275/35-18. Here's a diagram I had put together a year or more ago comparing the options available to stock (265/35 rear was never a consideration):
(click for larger version)

[Finnegan]

Originally Posted by jragan

The size most of us run on the stock wheels is front:245/40-18 and rear:275/35-18. Here's a diagram I had put together a year or more ago comparing the options available to stock (265/35 rear was never a consideration):
(click for larger version)

Wow! This is a huge help! I'm ordering a new set now!

[lucid]

If you want to reduce stagger a little to reduce understeer, you can also consider a 235/255 combo. Since this will remain your street setup, there is no obvious need to try to stuff larger rubber in the rear--especially if you will be using the OEM rims.

[Skelekitty]

Dang, I tried to post this earlier and my iPhone ate it (after I meticulously typed it in on that beastly little keyboard, too!)

Originally Posted by lucid

Right, drive around the streets on r-compounds that will hydroplane badly after they lose about 2/32"-3/32" of their 6/32" original thread, which won't take very long. Why do you think they are "just" street legal? Not to mention that you'll need to replace them how often exactly? And one really needs that type of traction on the street...

Well, he DOES live in Australia, so I'm guessing hydroplaning isn't too much of an issue.

Originally Posted by jragan

Only people at the top tier of their run groups should ever consider an R-Compound tire. R-Compound tires are the worst idea ever for trying to teach a driver car control because they stick when the car should otherwise not be sticking and teach drivers bad habits. (This is the same reason the best car control clinics are performed in the rain). I'm in the advanced run group in all the different associations in my area and I still choose to use the Direzza StarSpec because I still have learning to do.

Originally Posted by jragan

The size most of us run on the stock wheels is front:245/40-18 and rear:275/35-18.

As usual, GREAT info - and thanks for the chart!!!

Originally Posted by lucid

If you want to reduce stagger a little to reduce understeer, you can also consider a 235/255 combo. Since this will remain your street setup, there is no obvious need to try to stuff larger rubber in the rear--especially if you will be using the OEM rims.

I caught Ron (Finnegan) this morning before he actually ordered any tires and we're both letting the two recommendations for tires sink in. At this point in the day, I think we're leaning toward the 235/255 combo since, as you say Lucid, it's my street setup and this little baby is my daily driver.

However, we're also toying with the idea of getting an extra set of wheels for track and autoX days. Speaking of which, does anyone want to buy a 2007 Ford Escape Hybrid to help support this [strike]drug[/strike] er... car habit we've gotten ourselves into?

[jragan]

Originally Posted by Skelekitty

I caught Ron (Finnegan) this morning before he actually ordered any tires and we're both letting the two recommendations for tires sink in. At this point in the day, I think we're leaning toward the 235/255 combo since, as you say Lucid, it's my street setup and this little baby is my daily driver.

However, we're also toying with the idea of getting an extra set of wheels for track and autoX days. Speaking of which, does anyone want to buy a 2007 Ford Escape Hybrid to help support this [strike]drug[/strike] er... car habit we've gotten ourselves into?

The sizes I gave you are tried and true and work extremely well on the street. The extra tad bit of width also gives your rims a bit of extra protection. It's also worth mentioning that if you get a set of track wheels in the same 18" but wider sizes, you'll be able to swap your tires from your OEM wheels to your track wheels. For example, on the rack I run the same wheels as found for sale here http://www.zpost.com/forums/showthread.php?t=361970 which are much wider than stock (especially in rear). I use the same size Direzzas, though, on my OEM wheels and these track wheels. So as I use the track direzzas up, I have the direzzas on my OEM wheels moved to my track wheels and I get new direzzas for my OEM wheels. So I essentially keep new rubber for daily driving and save money in the long run because I'm not having to deal with different sizes, etc.

[Tonybest]

SO now I'm worried the tires and wheels I ordered will be wrong.

I got 235/40/18 in the front and 265/35/18 in the back. Dunlops Direzzas StarSpec Z1

I thought it would be ok being ever so slightly more square than the 225/255 combo that come with the car.

I also bought new wheels to use as track wheels only: O.Z. Ultraleggera in the same size as OEM 18X8 and 18X9.


And my going to hate this setup?

[Skelekitty]

Originally Posted by jragan

The sizes I gave you are tried and true and work extremely well on the street. The extra tad bit of width also gives your rims a bit of extra protection. It's also worth mentioning that if you get a set of track wheels in the same 18" but wider sizes, you'll be able to swap your tires from your OEM wheels to your track wheels. For example, on the rack I run the same wheels as found for sale here http://www.zpost.com/forums/showthread.php?t=361970 which are much wider than stock (especially in rear). I use the same size Direzzas, though, on my OEM wheels and these track wheels. So as I use the track direzzas up, I have the direzzas on my OEM wheels moved to my track wheels and I get new direzzas for my OEM wheels. So I essentially keep new rubber for daily driving and save money in the long run because I'm not having to deal with different sizes, etc.

Well, I can honestly say that now I don't know what I/we want to do on size, but we are def. going with the Dun I really like your idea (as a matter of fact, I'd go so far as to call it genius ). Saving money is also a plus!

You know what we WON'T be doing? Ordering the tires before we have a chance to sit down and talk about it this evening and think out loud.

Originally Posted by Tonybest

SO now I'm worried the tires and wheels I ordered will be wrong.

I got 235/40/18 in the front and 265/35/18 in the back. Dunlops Direzzas StarSpec Z1

I thought it would be ok being ever so slightly more square than the 225/255 combo that come with the car.

I also bought new wheels to use as track wheels only: O.Z. Ultraleggera in the same size as OEM 18X8 and 18X9.


And my going to hate this setup?

:: pats Tonybest on back ::

[F360C]

My suggestion is to go for the 245/265 combo with RE-11s. I ran this combo for my first and second year of tracking (although on the old model RE-11, the RE-01R) and loved it. No only did they last FOREVER but they have sooooo much grip and are very forgiving when they let go. Did I mention they last forever?!?! I loved to drift these tires and towards the end I was activily trying to destroy them on the track. They still had enough life left after I was done with them that I sold them to a drifter buddy of mine. Hopefully he can destroy them at the drift comp that is coming up soon...

[Rick Hunter]

235/255 or 245/265 should effectively reduce some understeer as well.

[Finnegan]

Originally Posted by Rick Hunter

235/255 or 245/265 should effectively reduce some understeer as well.

Thanks!

[jragan]

Just to throw more information at you http://www.bimmerfest.com/forums/sho...d.php?t=294185 This was kinda the Direzza Master Thread for a while...

[AWM3]

Originally Posted by Tonybest

SO now I'm worried the tires and wheels I ordered will be wrong.

I got 235/40/18 in the front and 265/35/18 in the back. Dunlops Direzzas StarSpec Z1

I thought it would be ok being ever so slightly more square than the 225/255 combo that come with the car.

I also bought new wheels to use as track wheels only: O.Z. Ultraleggera in the same size as OEM 18X8 and 18X9.


And my going to hate this setup?

I think you will love this setup. The only issue remaining is to make sure your offsets front and rear and appropriate and close to OEM spec, since you are using OEM size wheels and only a slight change in the OEM tire size. Do you know what the front and rear offsets are for those particular wheels?

[Finnegan]

Originally Posted by Tonybest

SO now I'm worried the tires and wheels I ordered will be wrong.

I got 235/40/18 in the front and 265/35/18 in the back. Dunlops Direzzas StarSpec Z1

I thought it would be ok being ever so slightly more square than the 225/255 combo that come with the car.

I also bought new wheels to use as track wheels only: O.Z. Ultraleggera in the same size as OEM 18X8 and 18X9.

And my going to hate this setup?

Edited 4/2/10 @1.20pm after my discussion with Tire Rack--just sharing what they told me--I don't claim it's "correct".

If you do, we're going to hate it as too! I think you'll be fine!

This is exactly what we decided to go with: 235/40/18 in the front and 265/35/18 in the Star Specs. (50 buck rebate on those from Tire Rack as well.)

The overall diameter both front and rear is going to be about 1/2" less than stock, which we went into this knowing and which may have the following effects:

• A slight increase in effective gearing (which should be fun ) Tire Rack confirmed this
• Probably a very slight drop in highway MPG (oh my, the EPA mileage police may come after us ) Tire Rack confirmed this
• Possibly a slight bit more stiffness in the sidewall (which may offset 10mm wider rubber on the stock wheels). Tire Rack confirmed this but recommended running 2 PSI higher as there's less rubber/air cushion [shoulder wear potential with stock PSI] and to increase hydroplanning resistance
• Potentially more resistance to hydroplanning than the 245/275 setup (from what I've learned, going to wider rubber increases the chances of this, and given the amount of rain we get we took a more conservative position....)
  Tire Rack confirmed that this is an issue with wider rubber--with moderate increases it can be offset with a slight PSI increase
• Tire Rack also confirmed the suggestion by many here to dial in some negative camber on the fronts to both help with wear with this setup, decrease understeer, and improve turn-in.

I know I could have gone the 245/275 route, or 235/255 (couldn't get the front and rear diameters to be close enough), but this seemed to be the best solution for our needs and objectives.

Thanks for the great input! It made working through the options a lot easier. I'll give an update after they're mounted and broken in.

Originally Posted by jragan

Just to throw more information at you http://www.bimmerfest.com/forums/sho...d.php?t=294185 This was kinda the Direzza Master Thread for a while...

Thanks Jeremy!

[Tonybest]

Originally Posted by Finnegan

...This is exactly what we decided to go with: 235/40/18 in the front and 265/35/18 in the Star Specs. (50 buck rebate on those from Tire Rack as well.)

...

• A slight increase in effective gearing (which should be fun )
• Probably a very slight drop in highway MPG (oh my, the EPA mileage police may come after us )
• Possibly a slight bit more stiffness in the sidewall (which may offset 10mm wider rubber on the stock wheels). Tire Rack confirmed this but recommended running 2 PSI higher as there's less rubber/air cushion [shoulder wear potential with stock PSI] and to increase hydroplanning resistance
• Potentially more resistance to hydroplanning than the 245/275 setup (from what I've learned, going to wider rubber increases the chances of this, and given the amount of rain we get we took a more conservative position....)
  Tire Rack confirmed that this is an issue with wider rubber--with moderate increases it can be offset with a slight PSI increase

I know I could have gone the 245/275 route, or 235/255 (couldn't get the front and rear diameters to be close enough), but this seemed to be the best solution for our needs and objectives.

Thanks for the great input! It made working through the options a lot easier. I'll give an update after they're mounted and broken in.

...

I can't get the 50$ Cash back up here in Canada.

Highway MPG doesn't bother me since we use liters/100kms seriously though it won't bother me since they will be track only rubber... except I will need to mount them for the ride to the track and back.

Tirerack just confirmed packages left Indiana...

If my car will understeer... next ones will be 245/265. But I might change my mind again.

Thanks for all the info.

[Tonybest]

Originally Posted by car62

I think you will love this setup. The only issue remaining is to make sure your offsets front and rear and appropriate and close to OEM spec, since you are using OEM size wheels and only a slight change in the OEM tire size. Do you know what the front and rear offsets are for those particular wheels?

I know the fronts don't need spacers... but for the rears they are sending me 20mm spacers. I originally didn't want to go with spacers and maybe would have changed wheels because of that. But Tirerack convinced me I had nothing to worry about.

I will give you offsets when I get them.

[Finnegan]

Originally Posted by Tonybest

I can't get the 50$ Cash back up here in Canada.

Highway MPG doesn't bother me since we use liters/100kms seriously though it won't bother me since they will be track only rubber... except I will need to mount them for the ride to the track and back.

Tirerack just confirmed packages left Indiana...

If my car will understeer... next ones will be 245/265. But I might change my mind again.

Thanks for all the info.

I forgot part of the Tire Rack conversation: the agreed that dialing in some negative camber would help with the understeer, improve turn-in, and also optimize wear on the front with this setup. (Sorry about that, I added it to the post above.)

So, I'm going to run their recommendations, add some negative camber on the front, and keep a close eye on tire wear and adjust as needed based on that and performance.

Yeah, this is hardly the last set of tires we'll be putting on the car, so there's always next time. Consider it another manifestation of the "mod bug" .

This should be interesting and fun! I've learned so much this week thanks to members on the board! The community here is great!

[Blind32]

This has been a great thread. Very informative even for the people on the sidelines, just listening, like me

[Tonybest]

Originally Posted by Finnegan

I forgot part of the Tire Rack conversation: the agreed that dialing in some negative camber would help with the understeer, improve turn-in, and also optimize wear on the front with this setup. (Sorry about that, I added it to the post above.)

So, I'm going to run their recommendations, add some negative camber on the front, and keep a close eye on tire wear and adjust as needed based on that and performance.

...

This should be interesting and fun! I've learned so much this week thanks to members on the board! The community here is great!

Ok here is my non-mechanical savvy question.
How easy is it to adjust camber at the track?

I saw this post : http://www.zpost.com/forums/showpost...87&postcount=5

It looks complicated. I need to be able to do it on my own, at the track.
If it's too complicated, I'll run in stock form. Until my car becomes a track-only trailer transported car.

[Tonybest]

Originally Posted by Blind32

This has been a great thread. Very informative even for the people on the sidelines, just listening, like me

Still awaiting delivery? Oooooo... Hope it's soon.