Need wheel & tire advice. Looking for street setup with some autocross.

Hey fellas,

Sorry for the long and complicated question. Tried a search but didn't find anything quite right.

My '05 GT currently has stock 17" wheels with 235/55-17 BFG G-Force T/A tires. Suspension is Eibach pro system plus so it's lowered about 1 1/2". I'm old school. I like the look of more sidewall. So I like the existing look of the 17" tires, but was playing with the idea of new wheels anyway. The oem wheels are grey bullets (?) but, I've always preferred chrome, so have been looking at options. Advice I've received is to go no larger then 18" to keep the sidewall look. Besides, I'm not a fan of the harsher ride of 19 and larger wheels & tires. I really like the deep dish wheels like American Muscle bullets. If I'm going to go there, I might as well get the widest that will reasonably fit without re engineering things or adding spacers and such. One thing I DO NOT want is the stretched look. Sidewalls should be wider than the rims, not vice versa.

I thought I had this figured out, until I went to my first autocross last weekend. What a blast. Now I'm wondering how to improve grip on top of the looks. The BGF tires were screaming like stuck pigs. The whipple can overpower these tires easily and it understeered a lot. Tire pressures started at 42 in all. Eventually going down to 40 in the front and 36 in the back. I know, a lot of that is me. I run out of talent long before I run out of car, so seat time is what I need most. My best times were when the tires were the quietest. Beyond that, all the guys I met said better tires would be a big help. Many were running Bridgestone Potenza RE-71R tires, but they all said tire wear doesn't make them a good street DD tire. I'm not ready to build a dedicated set quite yet either. My source recommended Mickey Thompson Street Comps.

Can I do both? Can I improve the looks, with wider tires on deep dish wheels AND get a reasonable improvement in grip for the few autocrosses I hope to do each summer. I assume there must be some trade offs from either side. How much though? Are the deep dish wheels or staggered tire width an issue for autocross grip? I'm willing to stay equal width all around as a compromise. Is there a less expensive route to creating a dedicated set that could be driven, maybe an hour or so, to get the the event. Maybe then I'd look at the Potenzas. I definitely won't be changing tires at the site.

Advice I've received from a reputable source said max equal tire size would be 255/45-18 on 18x9 wheels. Staggered max would be 275/45-18 out back.

Your advice would be very much appreciated. Thanks in advance.

Attachment 14368 Attachment 14369

I can’t comment on sizes, but on a Mustang you don’t want a wider rear tire for autocrossing, a square setup would be best and I’d bet fastEd would be very helpful with this as he had a similar car for a while and he’s an autocrosser.
With regards to the “tire wider than wheel”, I’m no expert but I’m sure that would create unpredictable handling at the track as the tires would be more prone to fold and flex, I’m thinking the best option would be tire width equal to rim width or slightly smaller for sharper turn-in.

Thanks Ponyryd.

When I say "tire wider than wheel" I mean the traditional look where there's some bulge to the sidewall. The sidewall is the widest part, like in the attached picture. What I do not want is the edge of the rim to be the furthest thing outboard. Seems to be a new thing, I see with lower profile tires, that this old fart just can't get his head around. Just does not look right to me, and besides, it's far easier to scrape your rims with that look.

Attachment 14372

**** Also, to clarify/add a point. I'm working on the assumption that lower profile tires handle better and will have less sidewall flex than my oem 17s. If I can get a decent improvement in grip and stay with 17s, then that's another option I'm willing to explore.

That depends on the tire, if you get a 17” track tire it will have much better grip and less sidewall deflection than an 18” all season.

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Originally Posted by Ponyryd

That depends on the tire, if you get a 17” track tire it will have much better grip and less sidewall deflection than an 18” all season.

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I hear ya. I'd rather not go all out this early in my autocrossing career and get a dedicated set of track tires. I'm just looking for a reasonable compromise between streetable tire wear and ride quality and improved cornering ability. If I can do that with the staggered, deep dish look, then great. If not, then I'll have to decide which is more important.

EDIT:
Thinking out loud. Options?
- instead of staggered get equal width deep dishes?
- would the added offset of the DD wheels adversely effect autocross type handling, or what about max tire width? Overthinking? yes.
- get the staggered DD wheels and decent street tires, then use the old oem 17x8 rims for autocross. I'd need 17" sticky tires.

If it was me I’d go for a square deep dish setup and be done, that’s the easiest and most economical, and of course you can keep your old wheels to use for dedicated track tires if you find yourself tracking enough to justify it.
Really though, when it comes to autocross, a light wheel/tire combo is best, and an AM deep dish wheel isn’t exactly light, but it’s a good place to start and see if you want to get into it farther.

As someone who tracks a similar car, 2006 GT with a Roush M90, this it what I have done:

Always a square set. First was the stock 17x8 Bullitts with 235/55/17s. Moved quickly to 18x8.5 Bullitts, first with 235/??/18s then 255/45/18s. Currently running a set of Roush 18x10s with 275/45/18s. The car has always been driven to and from the track. Because the car was a daily driver, yes even in the winter, the tires had to be some what streetable. The OEM BFGs on the 18s were decent enough while I was learning to track the car. Next was set of Nitto555s. They were an exceptional all around tire and more than enough for me to have loads of fun at the track. They are still on the 18 Bullitts today. Earlier this year while researching new tires, I was lucky enough to get the set of Roush wheels clad with Cooper tires. I've only had one track day with them, and they more than held their own. If I didn't get the 18x10s I was debating between the Nitto555 Gen IIs and the Firestone Firehawk Indy 500s. If money was no object, And I could trailer the car to the track Iwould have a dedicated set of track tires, read slicks, on light weight wheels. Will dedicated ultra sticky track improve your lap times, probably, but are they worth the extra money for just a few times a year, and will the increase the smiles/lap factor?

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Originally Posted by Ponyryd

If it was me I’d go for a square deep dish setup... Really though, when it comes to autocross, a light wheel/tire combo is best, and an AM deep dish wheel isn’t exactly light, but it’s a good place to start and see if you want to get into it farther.

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Good points. Thanks.

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Originally Posted by Stephen06GT

As someone who tracks a similar car, 2006 GT with a Roush M90, this it what I have done: Always a square set...Currently running a set of Roush 18x10s with 275/45/18s...

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Please tell me more about the 18x10 wheels & 275 tire combo. On all 4 corners? Are you using spacers or any other mods? Is your car lowered? Mine is. No rubbing or interference with suspension articulation or steering? Do you know the offset or backspacing on those rims? A trusted source told me the the widest I could run on my '05, without spacers or other mods, is 255/45-18 up front and 275/45-18 out back. Can you post some pictures from different angles and close up please?

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Originally Posted by Stephen06GT

Will dedicated ultra sticky track improve your lap times, probably, but are they worth the extra money for just a few times a year, and will the increase the smiles/lap factor?

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I hear ya. As you said, we're talking about something that's only going to happen a couple times a year. I just want less squealing, and a little better response & handling. Some of that will come from me getting more seat time, but the "extra" that lighter wheels or ultra sticky track tires would garner is not worth the extra expense and work.

Thanks again fellas. Much appreciated.

In the same breath, drive with dedicated ultra grippy tires just once.............ruined for life.
BFG R1s on the Cobra, epic difference.


https://www.tirerack.com/images/tire...r1_pdpcrop.jpg

There are very few choices in 275/45R18, that is an OEM size for Porsche and Mercedes SUVs so the selections are all expensive high-end tires.

You should look at 275/40R18 if doing a square setup, or if you insist on staggered, then look at 255/45R18 and 285/40R18 so that the overall diameter matches front to rear.

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Originally Posted by ZR

In the same breath, drive with dedicated ultra grippy tires just once.............ruined for life.
BFG R1s on the Cobra, epic difference.

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Gee, thanks. ;) You realize I now have a little angel and devil on my shoulders, like in the cartoons, eh? Sticky tires, hmmmmm. What are the chances I do that then start breaking driveline parts? It's a stock rear end, driveshaft and transmission. The DFX clutch should be more than enough. Damn, why am I even talking about this, LOL ?!?!?!

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Originally Posted by Parkway Ford Lincoln SVT

You should look at 275/40R18 if doing a square setup, or if you insist on staggered, then look at 255/45R18 and 285/40R18 so that the overall diameter matches front to rear.

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Wow, excellent info! Thanks for the course correction.

Can you elaborate please. What do you recommend for wheel width and offset specs for those tire sizes?

The roush 18x10s should fit fine everywhere. Roush stuff is usually pretty bang on.

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Originally Posted by wildswing

Wow, excellent info! Thanks for the course correction.

Can you elaborate please. What do you recommend for wheel width and offset specs for those tire sizes?

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Stephen has the 275/40R18 on his car, I'm thinking that he just made a mistype with the 45.


The options for larger staggered tire sizes in 18" are diminishing, the only ones in the 255/45 & 285/40R18 combo I'd currently recommend are the latest from Continental, the ExtremeContact Sport. Very nice street tire with good dry & wet grip, and could be used for autocross or track days … bearing in mind that you won't keep up with people that are running the max effort stuff like the RE-71R.

https://www.continentaltire.ca/car/t...econtact-sport

Another option for staggered is to go with 245/45R18 and 275/40R18. Still not ideal, but better than your OEM 235 tires. Those sizes are much more common, and give you many more choices for brand and model. An excellent option at a great price is the Firestone Firehawk Indy 500, which are made from the same carcass as a Bridgestone RE003, one of their tires not sold in North America. These are impressive performers, especially when the price is factored in.

https://www.firestonetire.ca/tire/firehawk-indy-500


Wheel sizes needed would be 18x9 with offset in the +35 range, and 18x10 with offset in the +40 range, give or take a few mm either way.


if doing the 275/40R18 all around, then you should have 9.5" or 10" wheels with offset in the +40 to +45 range.

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Originally Posted by dbovine

The roush 18x10s should fit fine everywhere. Roush stuff is usually pretty bang on.

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Makes sense. Thanks.

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Originally Posted by Parkway Ford Lincoln SVT

Stephen has the 275/40R18 on his car, I'm thinking that he just made a mistype with the 45. The options for larger staggered tire sizes in 18" are diminishing, the only ones in the 255/45 & 285/40R18 combo I'd currently recommend are the latest from Continental, the ExtremeContact Sport. Very nice street tire with good dry & wet grip, and could be used for autocross or track days … bearing in mind that you won't keep up with people that are running the max effort stuff like the RE-71R.

https://www.continentaltire.ca/car/t...econtact-sport

Another option for staggered is to go with 245/45R18 and 275/40R18. Still not ideal, but better than your OEM 235 tires. Those sizes are much more common, and give you many more choices for brand and model. An excellent option at a great price is the Firestone Firehawk Indy 500, which are made from the same carcass as a Bridgestone RE003, one of their tires not sold in North America. These are impressive performers, especially when the price is factored in.

https://www.firestonetire.ca/tire/firehawk-indy-500

Wheel sizes needed would be 18x9 with offset in the +35 range, and 18x10 with offset in the +40 range, give or take a few mm either way. If doing the 275/40R18 all around, then you should have 9.5" or 10" wheels with offset in the +40 to +45 range.

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Thanks again for all the excellent info Parkway.

Anyone have an opinion on Mickey Thompson Street Comp tires? Just another tire recommendation I've received.

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Originally Posted by wildswing

Makes sense. Thanks.



Thanks again for all the excellent info Parkway.

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Ed is the man. And he was correct, I made a typo with regard to the 275/40/18s.

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Originally Posted by wildswing

Anyone have an opinion on Mickey Thompson Street Comp tires? Just another tire recommendation I've received.

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They are made for Mickey Thompson by Cooper Tires, and are a good product for the price point.

I need to set up an autoreply to thank you. :)

Lots of good info in here!

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Originally Posted by Parkway Ford Lincoln SVT

The options for larger staggered tire sizes in 18" are diminishing, the only ones in the 255/45 & 285/40R18 combo I'd currently recommend are the latest from Continental, the ExtremeContact Sport. Very nice street tire … bearing in mind that you won't keep up with people that are running the max effort stuff like the RE-71R.

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I was just reading the description of the Bridgestone RE-71R on Tire Rack. In it TR says,

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the Potenza RE-71R, like all Extreme Performance Summer tires, are not intended to be serviced, stored or driven in near- and below-freezing temperatures, through snow or on ice.

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Can't even be stored below freezing? Wow. So no chance of using these as dual purpose tires even if driven very little unless you don't try to extend your season early in the spring or late into the fall and store them in the house over the winter. I have to admit I've heard of this before with certain Michelin Pilot tires, but only recently. A guy here just got a new GT this summer and it came outfitted with some of these tires that are afraid of the cold. He double checked with Michelin tech support. They told him the tires should NEVER see cold temperatures. He had the dealer change them for something else.

Can y'all pro tire guys confirm that ALL extreme performance summer tires are like this?

Even the descriptions of tires in their MAX performance category have a cold temperature warning, although not as severe. The following is from the description of the Continental ExtremeContact Sport.

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Note:: Tires exposed to temperatures of 20 degrees F (-7 degrees C) or lower must be permitted to gradually return to temperatures of at least 40 degrees F (5 degrees C) for at least 24 hours before they are flexed in any manner, such as by adjusting inflation pressures, mounting them on wheels or using them to support, roll or drive a vehicle.

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So what if you have these tires on your car and you have an unexpectedly cold night. What do you do? Don't move the car and let ambient warm up to over 5°C before moving it?

Tire Rack has no such warnings on tires in their ultra high performance tire category.

Along with the previous temperature question above, I'm back with a question about size & fitment, or more of a confirmation.

In previous replies, Stephen and Parkway Ford, you both said 275/40R18 mounted on 18x10 [+45] would fit on all corners. That's the exact specs for Roush '05-'14 18" wheels. So why is it that online tire dealers tend to spec 10" only for the rear? Square setups always seem to be 18x9. I figure they're just being overly conservative, and you guys know what fits by experience. Also, I assume that there's nothing magical about the Roush wheels, so any 18x10 +45 would fit as well. Does that sound right?

With that in mind, I'd like to talk about deep dish wheels. Their 18x9” are 30 mm offset, 5.94” backspace and 18x10” DD are 45 mm offset, 7.2” backspace. As mentioned above, they say the 10" is only for the rear, but by their specs seem to match what you guys say fits all around. In their Q&A section they say, "The width and the offset of the wheel make it difficult for the wheel to fit properly within the front wheel well. With some modification to the fender, control arm and possible the steering rack, you may be able to use a 10 inch wide wheel in the front, however, this would be a custom modification which we could not guarantee." What am I missing here?

They say their 18x10" DD bullets have a +45 offset. How is that possible. Maybe this picture will illustrate my confusion.

Attachment 14404

I got some feedback back from AM about their insistance that 18x10 can only fit on the back...

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While we've seen it done at times, we've also run into issues in the past with 18x10 setups on the front. We give a recommendation based on providing a guarantee that rubbing won't occur under just about any circumstances for that wheel. It may be possible to pull off an 18x10 square, and for Roush Mustangs that actually came with these wheels from the factory they had Roush steering stops to reduce the turn radius and avoid contact on turns. For most of their 18x10 wheels for clearing the front Roush does advise this as well. I'll include a link below:

https://www.americanmuscle.com/roush...ack-stops.html

The best bet for clearing with an 18x10 square setup would be the steering stops, and the best bet for the tires on an 18x10 to clear would be a 275/40R18. Each vehicle does respond to the suspension and other mods differently, and that roots style blower you have on there will bring the front down a bit more with the added weight. We recommend test-fitting wheels and tires for clearance prior to installing. Ordering one for test-fitting is what I often recommend for similar situations.

Regarding the offset of the deep dish wheels, the lip sort of gives it a more concave look though the "spokes" won't go in by the same distance as the non-deep dish wheels, just far enough to provide the same offset. It would be possible to fit 18x9 square, which would allow you to do a 265/35R18 tire square if you wanted.

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Their recommendation of using 265/35R18 on 18x9 seems odd. Tire diameter is 25.3". That's 2 inches less than my stock 255/55R17 27.2" dia. I would think 255/45R18 on either an 18x8 or 18x9 wheel would make more sense.

I'm also not a fan of rack limiters. I had some on my '91 and they gave it the turning radius of a bus. I'd like to follow up with those that either have run or recommend 275/40R18 on 18x10 on all corners. Are there specific wheels you also recommend? Your thoughts please. If you have successfully run 275/40R18 on 18x10 rims on a lowered car without suspension or steering mods, please tell me what rims you used.

Thanks again!

Stephen has the square Roush set up on his, looks and fits perfect.

10" at +43 to +45 with a 275 or 285 width tire will fit all around on an S197 without issues.


cheers
Ed

Thanks very much guys. I'm sorry if I'm beating a dead horse here, but please confirm, your endorsement of 275/40-15s on 18x10 +45 also applies if the car is lowered? I don't think anyone's said that outright yet. If they have, it's my mess up for not paying enough attention. Again, I appreciate your patience with me.

FYI I got some clarification from AM regarding the specs on their deep dish wheels. I mentioned in a previous post how I was confused by their specs that said their 18x10 regular and deep dish had the same offset, +45. I could not wrap my head around that. He said it had to do with the shape of the spokes...

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I want to make sure I understand your explanation of the deep dish wheel's shape. Are you saying the tire's on both normal and deep dish are in the same location relative to the mounting surface, and that the deep dish look is achieved solely by changing the shape and position of the spokes?

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That would be the case, the tires for the wheels we carry are in the same location relative to the mounting surface. The spokes are positioned and angled differently so to speak to achieve this.

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This is the modified picture I sent along with that last question...

Attachment 14415

My 07 GT was lowered and had 18x10 at +43 with 275s all around, then 19x10 with 285s all around. The issue with some of the wheels that the vendors sell as rears only is that the spoke shape won't clear the bigger brake setups. If you are thinking about going to the 14" Brembos from the GT500, this is a consideration.


cheers
Ed

FYI, my car is lowered as well.

Thanks for the brake reminder Ed.

Thanks again guys. Your help is very much appreciated. I think I've finally got enough info.

You may want to also take a look at LMR for rims and tires. Good service, decent quality and usually wheels are designed for your car and reasonable pricing (but in US dollars).

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Originally Posted by FABMAN

You may want to also take a look at LMR for rims and tires. Good service, decent quality and usually wheels are designed for your car and reasonable pricing (but in US dollars).

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Thanks for the hint. Buying from the US is a definite possibility since I live in the Soo. I get stuff from eBay, Amazon, etc., shipped to Sault Ste Marie, Michigan all the time. There's even a Tire Rack service center there.

If you go that way, careful on what you pick for tires. Sometimes they have some pretty mediocre performing stuff packaged with the wheels to be able to offer them at an attractive price. Many of them would be fine for street use, but a disappointment when pushed in an auto-x.

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Originally Posted by Parkway Ford Lincoln SVT

If you go that way, careful on what you pick for tires. Sometimes they have some pretty mediocre performing stuff packaged with the wheels to be able to offer them at an attractive price. Many of them would be fine for street use, but a disappointment when pushed in an auto-x.

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Thanks for the heads up. I figured as much, so was already planning on buying wheels and tires separately. Tire selection so far has been whittled down to Mickey Thompson Street Comp, or Firestone Firehawk Indy 500. I've heard a lot of good things about the Firestone and their prices are the best.

A group of us from the Soo are going to the Mackinaw City Mustang Show in a couple weeks. I'm sure there'll be lots of S197s there with different wheel/tire combinations to get ideas from.

Parkway Ford has very competitive pricing on tires. I am very pleased with the wheel and tire combo Ed set me up with for my CTS wagon. I also bought my track day tires from him. I don’t think that I could have done better for the money.
My 2 cents.

https://www.kijiji.ca/v-tires-rims/g...ationFlag=true

Not my ad nor do I know the seller.

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Originally Posted by RAT ATK

Parkway Ford has very competitive pricing on tires. I am very pleased with the wheel and tire combo Ed set me up with for my CTS wagon. I also bought my track day tires from him. I don’t think that I could have done better for the money.
My 2 cents.

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I appreciate the bump for Parkway. I don't doubt their competitive pricing. Unfortunately, I'm 8 hours away, measured either through Canada or the US.

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Originally Posted by 1BAD92LX

https://www.kijiji.ca/v-tires-rims/g...ationFlag=true

Not my ad nor do I know the seller.

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10-4. Thanks for the link. I'm 8 hrs away. Shipping costs in Canada are nuts. My guess is it would cost me $150 to $200 get those to me. I'll contact the seller tonight. Thanks again.

Agreed, would love to fix you up with a package, but shipping costs put a dent in our competitiveness for pricing.


My vote is for the Firestones … as I've said on here before, I strongly believe that they are currently the best value for a budget-friendly high performance tire. Great traction, great price.

I have the Firestone’s - so far not disappointed one bit. I’d pick up a second set right now if I had some spare $$
- great bang for your buck if u going through multiple sets of tires anyway-


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