Wheel & tire help for autocross/track

[IT Gnome]

I picked up a 2006 MS6 recently. The previous owner installed a GTX3071R turbo so the car would be in the Street Modified class. This class allows me to run R-comp tires which I don't have any experience with. I know I'll need more than the street tires I have now.

I really like the TSW Nürburgring wheel which comes in 2 sizes that might work:
18x8.5+45 or 18x9+63 (this will need 10mm spacers & extended wheel studs)

The fenders have already been rolled, not flat but done professionally, and no pull.
The 8.5" wheel with a 235/40 tire according to Rims&Tires should have plenty of clearance inside and stick out about 20mm.
The 9" wheel with a 245/40 tire will be approximately 13mm closer to the suspension and stick out 17mm if I use a 10mm spacer giving an effective offset of +53.

These are the tires I've been looking at. The dimensional data comes from TireRack. (I couldn't insert my Excel spreadsheet.)

Model/Size Tread Width Diameter Weight Rim Width
Pirelli P Zero Trofeo R
225/40R18 8.1 25.1 23 8.5
235/40R18 8.5 25.4 22 8.5-9.0
245/40R18 8.7 25.7 25 9.0

Toyo Proxes R888R
225/40R18 8.2 25.1 23 8.5
235/40R18 8.6 25.4 24 9.0
245/40R18 8.9 25.7 25 9.0
255/35R18 9.6 25.0 25 10.0

Michelin Pilot Sport Cup 2
235/40R18 8.0 25.4 21 8.0-8.5
245/40R18 8.3 25.7 22 8.5

BFGoodrich g-Force R1 S
225/40R18 9.0 24.9 21 9.0-9.5
245/40R18 9.7 25.4 23 10.0

Hankook Ventus Z214
225/40R18 8.4 25.0 21 8.5
245/40R18 9.1 25.6 24 9.5
245/40R18 9.1 25.6 24 9.5

Yokohama Advan A048
235/40R18 8.2 25.4 24 8.5

Hoosier R7
225/40R18 8.8 24.8 20 8.5-9.0
245/40R18 9.0 25.4 22 9.0-9.5

Hoosier A7
225/45R17 9.0 24.7 20 9.0-9.5

Hoosier Radial Wet H2O
225/45R17 8.8 24.8 21 9.0
245/40R18 8.7 25.5 21 9.0

Yokohama Advan A052
225/40R18 8.4 25.1 22 8.5
235/40R18 8.8 25.5 23 9.0
245/40R18 9.2 25.1 24 9.5

Any insight on sizing what will fit would be appreciated. Also any recommendations on the tires as well. This would be a dedicated setup for autocross and occasional track days. I hope to get coilovers this spring too.

[Fstrnyou]

I'm willing to bet one of @phate;'s threads will answer your question.

[phate]

Originally Posted by IT Gnome I picked up a 2006 MS6 recently. The previous owner installed a GTX3071R turbo so the car would be in the Street Modified class. This class allows me to run R-comp tires which I don't have any experience with. I know I'll need more than the street tires I have now. <way too skinny bs> Any insight on sizing what will fit would be appreciated. Also any recommendations on the tires as well. This would be a dedicated setup for autocross and occasional track days. I hope to get coilovers this spring too.

335's.


Really, if you don't have much experience autocrossing, just rock street tires for a while. Don't run Hoosier A's on a road course, they'll overheat way too quickly. Hoosier R's suck for autocross.


In general, run the widest wheel you can, then size the tire to that. You can run a 9.5 with 255's on heavily rolled and pulled fenders.

[IT Gnome]

Originally Posted by phate 335's. Really, if you don't have much experience autocrossing, just rock street tires for a while. Don't run Hoosier A's on a road course, they'll overheat way too quickly. Hoosier R's suck for autocross. In general, run the widest wheel you can, then size the tire to that. You can run a 9.5 with 255's on heavily rolled and pulled fenders.

I've been autocrossing for 3 years now. My wife and I ran our VW EOS last year in HS. I finished 7th overall out of 50+ drivers and my wife finished tied for 2nd in Novice.

I'm considering running the MS6 this year but if I do, the car needs help in the tire department. THe previuous owner dumped all his money into the engine and drivetrain but nothing into the brakes, suspension, or tires.

[GohanX]

Originally Posted by IT Gnome . I'm considering running the MS6 this year but if I do, the car needs help in the tire department. THe previuous owner dumped all his money into the engine and drivetrain but nothing into the brakes, suspension, or tires.

I kinda hate when people do that to these cars. If you wanted power without the ability to handle why not just get a Mustang instead of a Mazda?

[IT Gnome]

Originally Posted by GohanX I kinda hate when people do that to these cars. If you wanted power without the ability to handle why not just get a Mustang instead of a Mazda?

My feeling exactly. He also put aesthetic aero mods on it like the rear diffuser among others which I'm in the process of removing.

[phate]

Originally Posted by IT Gnome I've been autocrossing for 3 years now. My wife and I ran our VW EOS last year in HS. I finished 7th overall out of 50+ drivers and my wife finished tied for 2nd in Novice. I'm considering running the MS6 this year but if I do, the car needs help in the tire department. THe previuous owner dumped all his money into the engine and drivetrain but nothing into the brakes, suspension, or tires.

This is my 5 year and counting journey of turning the MS6 into a dedicated autocrosser for Street Prepared: MS6 Suspension Data & DIY Bilstein Coilovers


Much of what you're considering boils down to budget and at what level you want to compete (and if you really want to stay in SM). Are you looking to stay local and have some fun with the car? Would you be willing to go a little smaller or even back to stock turbo? Or are you talking about a full bore autocrosser?

[IT Gnome]

Originally Posted by phate This is my 5 year and counting journey of turning the MS6 into a dedicated autocrosser for Street Prepared: MS6 Suspension Data & DIY Bilstein Coilovers Much of what you're considering boils down to budget and at what level you want to compete (and if you really want to stay in SM). Are you looking to stay local and have some fun with the car? Would you be willing to go a little smaller or even back to stock turbo? Or are you talking about a full bore autocrosser?

For now, I only compete locally with the Mohawk-Hudson SCCA and the Poughkeepsie Sports Car Club. Between the 2 clubs, that's 15-20 autocross events a year. I might try a couple track days since I live 20 minutes from Lime Rock and some club members go over to Palmer and Thompson.

The engine is built and tuned. I don't feel like messing with it at this stage so I'd end up staying SM. I haven't defined a budget yet either.

[Fstrnyou]

I was looking at TSW Nurburgring yesterday for summer tires. The 18x8.5+45. My only hangup is which color to get. Gray...or gray with machined face.

[shamie]

If your budget allows, Hoosiers all day every day. A7 for autocross R7 for road work.

The Hankook 214s offer multiple compounds and are a much cheaper option and last a little longer.

As Phate eluded too - one tire (compound) won't be the best for both applications.

[phate]

Originally Posted by IT Gnome For now, I only compete locally with the Mohawk-Hudson SCCA and the Poughkeepsie Sports Car Club. Between the 2 clubs, that's 15-20 autocross events a year. I might try a couple track days since I live 20 minutes from Lime Rock and some club members go over to Palmer and Thompson. The engine is built and tuned. I don't feel like messing with it at this stage so I'd end up staying SM. I haven't defined a budget yet either.

I think I would stay away from the Hoosiers if you don't want to run through 2-3 sets per year. The A7's with good camber control will last upwards of 100-120 runs, as reference.




Maximize wheel width. You compromise tire contact patch and response by throwing a big tire on narrow wheel.

17x9.5 with a 245/40/17 R comp will work well. Slightly shorter tire than stock - works well if you tend to run lower speed autocrosses where you don't bang limiter but can still be up in the revs for boost. 18x9.5 with a 245/35/18 is the same story. This will be a little crisper since there's less sidewall.

18x9.5 with 245/40/18 works, too. If you have higher speed courses, these will give you a bit more top end speed. But it might suck coming out of really slow digs.

You can run any of those combos without cutting fenders with proper offset. A 9.5 should be around +45 to be as far inboard as possible, and let you spacer it out a few mm if you get any rubbing. I ran 17x9.5 +38 Enkei NT03+M and had ~5mm of space to go inboard with a 255/40/17 street tire.



Stock rotors and calipers are good. Upgrade to your pad compound of choice.


Camber control is a MUST with R-Comps. You won't unlock their potential until they're happy, and you'll chew through the shoulders if you don't have enough. Expect a need for upwards of -3.5° of camber front and rear, ESPECIALLY if you have soft suspension.

[IT Gnome]

Originally Posted by Fstrnyou I was looking at TSW Nurburgring yesterday for summer tires. The 18x8.5+45. My only hangup is which color to get. Gray...or gray with machined face.

My wife and I both like the grey with machined face. I like the contrast.

[IT Gnome]

Originally Posted by phate I think I would stay away from the Hoosiers if you don't want to run through 2-3 sets per year. The A7's with good camber control will last upwards of 100-120 runs, as reference. Maximize wheel width. You compromise tire contact patch and response by throwing a big tire on narrow wheel. 17x9.5 with a 245/40/17 R comp will work well. Slightly shorter tire than stock - works well if you tend to run lower speed autocrosses where you don't bang limiter but can still be up in the revs for boost. 18x9.5 with a 245/35/18 is the same story. This will be a little crisper since there's less sidewall. 18x9.5 with 245/40/18 works, too. If you have higher speed courses, these will give you a bit more top end speed. But it might suck coming out of really slow digs. You can run any of those combos without cutting fenders with proper offset. A 9.5 should be around +45 to be as far inboard as possible, and let you spacer it out a few mm if you get any rubbing. I ran 17x9.5 +38 Enkei NT03+M and had ~5mm of space to go inboard with a 255/40/17 street tire. Stock rotors and calipers are good. Upgrade to your pad compound of choice. Camber control is a MUST with R-Comps. You won't unlock their potential until they're happy, and you'll chew through the shoulders if you don't have enough. Expect a need for upwards of -3.5° of camber front and rear, ESPECIALLY if you have soft suspension.

I figured that I'd need to get the SPC upper ball joints and their rear upper links to get the necessary camber.

The TSW Nürburgring does come in an 18x9.5+40. Would that work with the 245/35/18 tire? I have room to roll the inner fenders more. They're not a flat roll now but there's no pull which I'd prefer not to do.
I saw a link to an article about proper sizing of tires in another thread somewhere. It mentioned that the rim should be the same to 0.5" wider than the measured tread width.

The autocross courses are mostly of the tight technical variety. Almost all the drivers never get out of 2nd gear.


I guess I can take my springs out and move the wheel through its suspension range to get an idea the clearances. The car only has the Eibach Prokit springs with the stock shocks. If I don't get coilovers, I figured on getting Bilstein B8 shocks at least.

[IT Gnome]

Originally Posted by phate ... Stock rotors and calipers are good. Upgrade to your pad compound of choice. ...

I have a set of Hawk HPS 5.0 pads for daily running but I have used Carbotech pads in the past and will probably use something like their AX6.

Last year my wife and I used the Hawk Street/Race pads (DTC-30?) They worked quite well. I used them with Comar GS610 fluid.

[phate]

Originally Posted by IT Gnome I figured that I'd need to get the SPC upper ball joints and their rear upper links to get the necessary camber.

That's pretty much my setup, but with some offset UCA bushings in the front to get a bit more camber than just the ball joints offer. In the rear, I run the LCA as far inboard as I can via the lower camber adjuster, then get my camber set with the SPC UCA (let's me run the car a little narrower). Be aware that the SPC rear UCA has a spherical bearing on one end, so if you ever drop down to SP or ST class, they aren't legal. [I swapped the spherical for some poly bushings.]

Originally Posted by IT Gnome I figured that I'd need to get the SPC upper ball joints and their rear upper links to get the necessary camber. The TSW Nürburgring does come in an 18x9.5+40. Would that work with the 245/35/18 tire? I have room to roll the inner fenders more. They're not a flat roll now but there's no pull which I'd prefer not to do. I saw a link to an article about proper sizing of tires in another thread somewhere. It mentioned that the rim should be the same to 0.5" wider than the measured tread width. The autocross courses are mostly of the tight technical variety. Almost all the drivers never get out of 2nd gear.

Yep, that should work well. TireRack is the only place that publishes a tread width number, so I use it and go by those same guidelines. You can even stretch the tire just a touch more and still be just fine. It makes them a little crisper transitionally.

Originally Posted by IT Gnome I guess I can take my springs out and move the wheel through its suspension range to get an idea the clearances. The car only has the Eibach Prokit springs with the stock shocks. If I don't get coilovers, I figured on getting Bilstein B8 shocks at least.

Those springs are a little softer than stock, IIRC. The B8's are good, as well as the B6's but the rears are a touch soft. Either one could make the foundation for a sweet coil over setup

Originally Posted by IT Gnome I have a set of Hawk HPS 5.0 pads for daily running but I have used Carbotech pads in the past and will probably use something like their AX6. Last year my wife and I used the Hawk Street/Race pads (DTC-30?) They worked quite well. I used them with Comar GS610 fluid.

When I was running stock calipers with 200TW street tires, I ran a HPS front pad and HPS5.0 rear pad. They weren't enough to stop 285 wide Hoosiers, so I bumped to HPS5.0 in the front and all was well again.

I haven't used the AX6 compound, but I did like both the XP8 and XP10 for autocross.




Since I went to the CS caliper with a smaller pad/less stopping power, I had to bump up to the HP+ compound and have mostly liked it. I have a set of DTC-30 in the garage for testing next season.

[IT Gnome]

The DTC-30 is noisy and dusty but it bites like the Dickens.

Sent from my Moto Z (2) using Tapatalk

[phate]

Originally Posted by IT Gnome The DTC-30 is noisy and dusty but it bites like the Dickens.

One thing about RComps is that they are much lighter than a regular street tire. They're easier to lock up if you stab the brakes, and pads with crazy bite can make it even more difficult. They also have way less feedback under both braking and cornering, so you have to be very cognizant of what the car is doing.

The 6 has a very intrusive ABS system, so I run with the ABS fuse pulled.

[IT Gnome]

Originally Posted by phate One thing about RComps is that they are much lighter than a regular street tire. They're easier to lock up if you stab the brakes, and pads with crazy bite can make it even more difficult. They also have way less feedback under both braking and cornering, so you have to be very cognizant of what the car is doing. The 6 has a very intrusive ABS system, so I run with the ABS fuse pulled.

If I understand you correctly, because R-comps are lighter and stickier, you can use pads with less bite than you need with say 200TW tires or regular street tires.

[phate]

Originally Posted by IT Gnome If I understand you correctly, because R-comps are lighter and stickier, you can use pads with less bite than you need with say 200TW tires or regular street tires.

RComps don't deal as well with a huge 'shock' of braking force. If we're defining bite the same way, yeah - I just mean the initial hit you feel at low pedal force when you're first getting into the brakes.

HPS/HPS5.0 have no bite, but moderate overall friction.

HP+ have high initial bite, and moderate-high overall friction.


It's just because they're lighter - much easier to stop a lower mass rotating object than a heavier one, especially because we're talking about mass at the outer region of a spinning disc.




Overall, RComps will brake WAY harder than street tires (and blend turning much, much better). We've pulled ~1.4g decel on rcomps vs ~1.2g on street tires. So, you still need a good amount of overall friction, you just can't slam you're way into full decel like you can with most street tires. You need to work with the weight transfer a little bit and get into rip-your-face-off braking force just a hair slower than skreet tires.

[IT Gnome]

Phate, you said the Eibach Prokit springs are softer than the stock springs.

The night I picked up the MS6, my wife was following me and at one point we turned to go up a hill and I gunned it. She noticed sparks coming from underneath as the car squatted down. Probably from the CPE exhaust which seems to hang a little low.

Is there a better option for springs that don't squat as much and would work well with the Bilstein B8 shocks if I go that route?
I'm not too concerned with being super low. A small drop is ok.

[Fstrnyou]

I have a new set of Corksport springs if you don't want to do full coilover set-up.
But most will tell you that coilovers offer much more bang for the buck.
That's the reason they're still in the box.

[phate]

Originally Posted by IT Gnome @phate You said the Eibach Prokit springs are softer than the stock springs. The night I picked up the MS6, my wife was following me and at one point we turned to go up a hill and I gunned it. She noticed sparks coming from underneath as the car squatted down. Probably from the CPE exhaust which seems to hang a little low. Is there a better option for springs that squat as much and would work well with the Bilstein B8 shocks if I go that route? I'm not too concerned with being super low. A small drop is ok.

The sky is the limit if you convert the B6 or B8 to a coil over.

Edit: There aren't any ots "spring kits" that offer any meaningful increase in spring rate. You're limited to ~20% stiffer than stock in a compromised rate split.

For reference, my springs are over 4x stiffer than stock with a lot more front and rear bar on top of that.