Joe Perez

iTrader: (8)

Saw the thread title, assumed this was about 10" diameter wheels. Came in here looking to ban someone. Was disappointed.

Thread rating 0/5. Would not read again.

Leafy

iTrader: (1)

I also want to try the 11" wheels. BUT I'm not sure if making the car 2 inches wider will cancel out any of the benefits of the tire fitting better. We KNOW that going from 9's to 10's on the 275 improves time. But we dont know if going from 10's to 11's will. And getting spinwerks to make me a set of 11's with basically no resale value that may or may not make the car faster is not something high up on my build list.

Just noticed the link in your sig. God Dammit Joe.

FrankL

We were thinking about Real wheels. I would expect similar results 9 to 10 as 10 to 11. Wonder if we could get the 949s widened to the front. Lol

bbundy

Yea I think the improvement seen with the 9 to 10 jump would also be seen with the 10 to 11 jump. I base on how much better the 245's feel and behave on the 10" wheels than the 275's

GeneSplicer

iTrader: (14)

I own a set of 10s... can't say I've used them though, sadly.

Fireindc

iTrader: (13)

With a geo metro drum brake conversion ?

Raucky

iTrader: (1)

I must be the coolest because I'm rocking 10.5" square and looking to go 11" square..lol.

bbundy

Funny my Discount Tire guy came by this weekend and I sold him some Miata parts. He told me upper management said they cannot mount 225 tires on 9" wheels. The explanation was it wasn't safe. I guess they lost my business with their stupidity.

k24madness

iTrader: (6)

I don't think we will see that happen. The 10's are slow movers compared to everything else. I am glad he made em cause I would be screwed without em.

FrankL

I didn't mean manufactured that way, more widened after the fact.

TheScaryOne

iTrader: (3)

My employer gave me the pleasure of sending me to a recent BFGoodrich training event at the Miller Motorsports Park in Ogden, Utah. We got to drive 2005-2009 Mustangs around the (flippin sweet) track. We also had a bunch of other training sessions, including driving an identical (make, model, tune and upgrades) car, back to back, with different width wheels and the same tires.

Let me tell you, the stock 8" wheels and (IIRC) 245/40R18 BFGoodrich Comp2 tires felt like **** compared to the 9.5" Shelby wheels with the same tires. There was less body roll, the car pointed better, just a total night and day difference. We went from the minimum rim width to almost the max (10") for that size. Aesthetically, the tires looked better on the 9.5" wheels too. Rather than having bulgy sidewalls that could load to the side while turning, they were nice and square to the wheel.

So it makes sense that 11's with the 275's would be an improvement. Hoosier even says 11 is the max they recommend for the A6. It would probably have a positive difference in handling, but might break loose easier under lateral loads, as the tire will have less "give" in the sidewalls. At the end of the training, we decided that any generic vehicle should get the best fitting, lightest, widest wheels (please no 15x15 gaucho wheels or 22" wheels and 26" tires, kthxbai) and tires should be sized to the wheels for ultimate performance. The priority afforded to being light weight is reduced on higher horsepower/larger vehicles. Slap some 18's or 20's on a stock Miata and feel the dearly departed power disappear, while upping from 15" to 20" on something with boost or a V8 is virtually unnoticeable, until you want to brake.

I had a coworker with an awd turbo Eagle Talon, who got a sweet deal on some 5x4.5 wheels. Unfortunately, they came off of an Explorer and weighed almost 40# each for a 18" wheel (not counting the extra weight of 18" tires, either). After two weeks he put the stock 19 pound 16's back on because he didn't have enough brake to compensate for all of the extra wheel and tire weight.

Unfortunately, this is a result of sue-happy America. I asked our BFG rep about why the catalogs changed. A couple years ago it used the terms "recommended rim width range" and gave a range. Now all of the new catalogs say "Minimum to Maximum Rim Width", with no suggestion that you can go outside of the lines. A 225/45R15 BFG G-Force Rival shows a max width of 8.5", and would likely work fine on a 9" wheel, but because someone sued we can't do it anymore.

Make friends with a tire guy. You won't have a receipt to sue anyone that way, and everything becomes hunky dory.

bbundy

I believe there are hundreds of people who have 225/45's mounted on 9" wheels now days. And a good number are G-Force Rivals. I have never herd of a single issue because of it, only that they perform better in pretty much every way when mounted on a 9" wheel as appose to something skinnyer.

My back to back testing 8 to 9" was almost a 2 second improvement on a minute 35 road course. And FWIW earlyer testing showed 205 to 225 both mounted on 7" were both pretty much equal to each other. Rim width to tire width ratio is more important than tread width. I don't know how much is too much. But I will say some of the Fastest PTE cars in the country limited by formula to 205 tires that can run any width wheel they want run 205 hoosiers on 9" wheels because they are faster than they are on 8" wheels.

TheScaryOne

iTrader: (3)

Sorry, by "would likely work" I most likely mean "will work" but because I'm so used to dealing with word-twisting mouth breathers I have to watch how I talk when it comes to tires.

But it's the sue-happy people, or people who were trying to get warranty credit, or someone who dug a fender into the tire (especially fender dug into sidewall from some oni-camber jerk) and wanted BFG to cover body damage when it blew out, who has caused you to be unable to get tires mounted.

I don't doubt that they'd be "faster," when you have tires stretched like that (205 on 9" is common for the drifters round here) the sidewalls are constantly under stress and can't flex as much(similar to an over-inflated tire). They are faster because they will respond quicker to acceleration and turning because of the stressed sidewalls, without the poor contact patch of overinflated tires. They're faster right up until you lose traction and slide off the road. (Read: They will always be faster with professional drivers who won't slide off the road) Try putting a novice driver in the same car and watch the fun. Also, they'll only be faster in situations where everyone is limited to the same size tire, elsewise someone will just run a wider tire for the extra contact patch.

Part of the reason drifters use stretched tires is that it's easier to blip the throttle to break them lose because the sidewall doesn't cushion either the torque of acceleration (radial deformation), or the car sliding sideways (angular deformation).

With taller/bulgier sidewalls (either high profile, or with wider tires/section widths), during hard cornering, the tire can roll over so the centerline of the wheel is no longer on the centerline of the tire. There is an equal amount of deflection in either direction under similar g's. The cushion in the sidewall means you don't need to worry as much about upsetting the car by jabbing the brakes, or turning the wheel too quickly, etc. etc. With undersized width tires it's also harder to get any radial/centrifugal deformation (think like wrinklewalls do on the strip, this happens on a less dramatic scale with all tires) because the sidewalls are constantly stressed.



The image is for dirtbike tires, but exaggerates the effect of lateral deformation.

As to section width being more of an issue than tread width, I don't know which is the most important. In the 225/45R15 size, every non-Hoosier (on the rack) has an 8.9" section width, with the R6 and A6 Hoosier's coming in at 9.8" (the wet Hoosier is 8.9"). Section width is also dynamic (you won't have 8.9" section width on a 10" wide wheel) so without knowing what width wheel they measured section width on, it's a measurement that only means anything when looking at the same brand tires. In this case, we do know that most of the tires were measured using a 7.5" wheel (some are unlisted). Even though the section width is wider on the Hoosier's, they still recommend the same 7"-8.5" wheel range as the BFG Rivals or the Hankook RS3's. Similar with the tread width, it's all over the place from 8" to 9" in this size, but everyone recommends the same wheel widths.

This tells me that a lawyer was responsible for the wheel width ranges. It doesn't feel like an engineering decision to arbitrarily assign the same min/max across a size without factoring the performance of each individual tire.

bbundy

I don't think you understand the wider rim makes a little more traction in a corner because the kinematics of the tire sidewalls deflecting in a corner keep the contact patch more consistently flat to the ground instead of transferring all the load to the outside shoulder. They are a lot faster however because it is easier to drive at and over the limit the snap breakaway feeling disappears when they are mounted on the wider wheel. The biggest difference in performance is not from what the lateral g’s peak at, it is because they are easier for a novice to drive at the limit and keep it near the limit or even bring it back from over the limit. The difference in sidewall stress is nothing.

On the 245/45/15’s mounted on 10” wheels I became comfortable coming off a 150mph straightaway downshifting to 5th turning in with as little braking as possible trail braking into the corner and scrub just enough speed to make it back to the apex of a 180 degree turn without dropping the speed below 100mph. knowing how the 275’s feel that would be a lot more scary on them.

TheScaryOne

iTrader: (3)

Except you're talking about taking them far beyond vertical sidewalls, to /---\ sidewalls. Which are constantly stressed. Which gives them a better contact patch because the sidewalls can no longer do what they are designed to do, which I alluded to in the first two sentences that you quoted.

The "feeling" of snap break away is gone, but the chances of snap break away aren't. Drifters run the same tires because it's easy to snap break away compared to proper width tires. The feeling is your tires loading the sidewalls while turning, then unloading when you jerk the wheel, or aren't smooth with gas and brake. I'd much rather get the feeling and know I did wrong, than to have it just happen with little warning (other than tire squeal). I don't see how removing one of the warnings would make them easier to drive for a novice. We got pretty familiar with that feeling in the Mustangs, 8" wide wheel with 245's. The whole point of the track time was to smooth out our inputs to avoid upsetting the car.

If you want a better contact patch, buy good tires. For example, Michelin and BFG both have technologies designed to increase the area of the contact patch as more force is transmitted to the outside edge of the tire. Michelin calls it Variable Contact Patch 2.0, and BFG calls it Enhanced ETEC with Dynamic Suspension.

You're picking an oranges comparison for our apples. Those 275's have more sidewall to move, so will definitely have more squirm in the exact same situation on a 10" wheel. The 245's are better for that wheel. This can be helped with proper pressure, although an 11" wide wheel would be better.

FrankL

I am more and more intrigued by the thought of 11s. Contacted a company to widen some of my 10" 949 wheels.

compaddict

Hmm. Subbed.

hrk

iTrader: (6)

13x10 all around or
13 x 10 front and 15 x 13 rear.

TheScaryOne

iTrader: (3)

Won't wider tires on the rear than the front induce understeer without any other suspension changes?

z31maniac

Hot Rod guys do this, I wouldn't want to screw up a set of 6ULs for it.

I suspect that by the time you include the cost of the 6ULs, shipping to the company and back + the work, you could just have Jongbloed/Keizer/etc make you a set.