reeseleblanc

Hey guys. I apologize if this has been covered. I've been looking for about an hour using keywords v1, widest, front, 9.5, etc trying to get an answer.

I know the 9" accessory wheels fit fine up front but would an 18x9.5 45 offset be able to work? Using a fitment calculator it seems like outside fitment is ok but I'm unsure on inner clearance. Can anyone offer any insight?

It shows that the wheel would be 15mm closer to the suspension.

Thanks!

Reese

AAIIIC

iTrader: (19)

The Accessory wheels aren't 9"; they're the same dimensions as the stock wheels (18x8.5" +42mm).

The Team Dynamics wheels are 9"; they're 18x9" +38mm, and they do fit fine up front. Based on what I've seen on my car, I don't believe an 18x9.5" +45mm would fit - the rim would hit the spindle. Here are a couple pics on my car:





The 9.5" wheel would have ~13mm more backspacing, which would close that 8mm gap between the wheel lip and the spindle. And the 7mm more offset would mean the 8mm gap at the shoulder of the tire would be damn close to disappearing.

Edit: That's a 275/35-18 R-compound tire.

Bio248

you're going to have to go down into the mid to lower 30s offset for a 9.5.

a 19x9.5 +33 physically fit, but i put a 3mm spacer on to clear the calipers a little more.

AAIIIC

iTrader: (19)

I've thought about going to an 18x9.5" or 18x10" to optimize the performance of the 275/35-18s I run on track; 9" is the minimum recommended width for those. That's how I came to be taking those pics above - went to look at what clearance I had to the inside and realized that pretty much all of the added width would have to go to the outside.

FuzzyLog1c

iTrader: (4)

The 19x9" Forgestar F14s have a +40mm offset. The extra 2mm on the Team Dynamics wheels is the only reason why AAIIIC can make that crazy 275 tire fit. If you plan on running a more reasonable tire on a 9.5" wheel, you'll need at least 7mm more offset than the Forgestar F14.

As an alternative, you can run STS aluminum spindles on the car, which have plenty of inboard clearance and reduce unsprung weight by roughly 5 lbs. After I did the upgrade, I found that there was enough room to install the rear Forgestar F14s (19x10 +42mm) on the front with a 5mm spacer. It was ugly, but it worked.

reeseleblanc

Thanks for the correction about the accessory wheels, AAIIIC! I was confusing them with the TD wheels.

In front I only plan to run 245-45, so that's considerably smaller than the 275s.

Basically, I'm looking at either STS spindles or using 15mm spacers. The wheels I found were heavily discounted but I don't know if they are worth it.

I really appreciate the input, guys!

AAIIIC

iTrader: (19)

I'm not sure what's "crazy" about a 275. It's within the tire manufacturer's recommended width range, lasts longer than an undersized (for this heavy car) 245/40 (the only other widely available R-comp size that would work), and is multiple seconds per lap quicker than the 245. And I guess your "fuzzy logic" explains why the 2mm of extra offset is the "only reason" my setup clears by 8-10mm everywhere?

Note that there is more clearance the farther up you go on the spindle (in other words, the larger the wheel diameter), so the fact your 19" wheels clear doesn't mean his 18"s would. An 18x10" +38mm wheel will not clear the STS spindle - there's about 5mm of interference. That wheel has almost exactly the same backspacing as the 18x9.5" +45mm.

FuzzyLog1c

iTrader: (4)

Because you're not accounting for wheel and tire deformation that occurs when you corner.

Anthony Toal

just curious, how much room does the STS spindle/knuckle really give for wider wheels? From what ive read, it is mostly for camber, i believe from your posts Fuzzy. Looking at it and comparing the two, it looks like the upper ball joint needs to be replaced as well.

barrok69

I'm running GM Accessory Wheels widened from 8.5" to 9". Offset is 48.35mm post widening. I run a 5mm spacer which reduces it down to 43.35mm. I have 5mm clearance from Tire to the spindle in the closest spot. The lateral runout of the wheel shouldn't be more than 1mm. I'm also running 275/35R18's and they are square on that widened wheel.

I've tracked my car with this setup and haven't had any rubbing on the fender/fender liners, or spindle.

I'm running the car pretty low right now and have ~ -2° camber up front. The turn in is great and wear has been minimal if any on the pilot super sports for street driving. If only we had faster steering racks this car would be really nice.

Without pulling the fenders or having your wheels/tires stick outside of the fender a 275 is going to be the widest front you'll be able to pull off.

vroom_vroom

iTrader: (5)

That's promising news, just bought two wheels to send out to be widened. Not a big spacer fan but they are a lot less than the widened trailing arms. Plus I'm not lowered so I should be straight forward.

Not to totally hijack this but seems stupid to start a new topic, I'm running the all season bfg sport comps in 245s is parking a 275 going to be enough of an improvement in traction as I am almost thinking of just putting the summer sport comps on the back and swapping the fronts when they run down but I'm sketchy on running two different tires. Thoughts

AAIIIC

iTrader: (19)

What's deforming the top of the wheel/tire, 180deg away from the contact patch? All the deformation at the bottom at the contact patch.

barrok69

Exactly.

FuzzyLog1c

iTrader: (4)

Your wheels and wheel bearings are deflecting toward the top of the spindle on the inside corner. If you had regular 26.7" diameter tires instead of the smaller 25.6" diameter tires, the tires would be scraping that outward bend in the spindle where that pinch bolt passes through.

Anti-knockback bearings and forged wheels help, but there's still a significant amount of flex. Articles and podcasts interviewing folks at Forgeline, HRE, and BBS have mentioning seeing a scary amount of barrel deformation in cast and flow-formed wheels under cornering loads on high speed cameras. That got me curious since I'm in the market for another set of wheels, but I couldn't locate any such videos.

I don't know if you listen to podcasts but Alan Peltier (president of HRE, 17 years experience) has been on a bunch of automotive podcasts over the past five years, including recently on the Petersen Automotive Museum podcast. In the past, Alan has identified that heavier cars, shorter sidewalls, larger diameter wheels, sticker tire compounds, and the continued demand for low unsprung weight are starting to require companies like HRE to consider retiring aluminum on their performance lines in favor of newer materials and composites that have a higher modulus of elasticity.

Personally, I think that it's important to maintain at least 5mm clearance between the wheel lip and spindle or trailing arm, or 7-10mm if you're on a strict budget and can't afford stiff wheels and bearings and still want to drive hard. Any less and you're running the risk of messing something up, particularly if you also drive hard on the street. I've been through a couple of sets of fenders hitting potholes while cornering, for example, despite what looked like adequate fender clearance. I'm just grateful that I haven't cracked a wheel or broken any suspension yet (knock on wood).

Bio248

"scary amount of barrel deformation" isn't very descriptive. there's no way in hell a wheel flexes several millimeters. there's no way in hell the combination of the wheel and wheel bearing flex several millimeters.

Sssnake

Any issues with this? I would love to get more rubber on the front of my car. With the F14s and 245/40s I have to run -1 camber just to have them clear rolled fenders. I have the STS spindles, the bearings and the ball joint already. This might be the motivation for me to put off other projects and get this done. When you say it was ugly I am assuming this is from a cosmetic standpoint... You don't like the deeper dish on the fronts?

FuzzyLog1c

iTrader: (4)

Ever experience pad knockback where the brake pedal drops?

http://www.stoptech.com/technical-su.../pad-knockback

Anthony Toal

But does having multiple, smaller pistons help that on our platform though with the knock back? Interesting read, though unless the bearings are going out, I dont see that much deflection happening either, which in that article, it is a good way to find out if you got one on the "fritz" as it says.

Anthony Toal

Curious about this myself, would like to fit 275s on all corners, or at least the fronts on F14s

FuzzyLog1c

iTrader: (4)

It doesn't get any better as long as the area ratio of the master cylinder to the caliper pistons remains the same. All the author was trying to say is if your master cylinder has a relatively huge bore (compared to the total surface area of all 8 or 10 caliper pistons), the amount of pedal travel required to close the "knockback gap" will be less. So you're less likely to notice the pedal drop.

Frankly, some of his solutions were stupid (although they may have been intended to reinforce earlier concepts). For example, reducing rotor diameter and/or increasing bore size don't fix the problem and introduces new problems (i.e. increased pedal effort and reduced torque and heat capacity). Better bearings and lightly-sprung residual pressure valves are better countermeasures.

Getting back to the earlier debate, if you think there's no deflection, I invite you to prop your car way up at a 37-40 degree angle so that two wheels are taking all the weight. Check your lower wheel clearance before and then after. If the change in wheel clearance is greater than your clearance on flat/level ground, you may experience spindle contact during 1.2G static cornering. If you want to evaluate for a 1.6G transient, increase the angle to 54-56 degrees.

Hopefully that mental image provides a better idea of the forces that can be placed on the tires, wheels, and bearings.