Tire Talk Megathread

[kolosy]

Originally Posted by DrFerry

Not stupid. The same tire when mounted on a wider rim can create more cornering force than when mounted on a narrower rim - even at the same pressure. This is because ~85% of a tire's stiffness is pneumatic with the rest being structural. However, inflated lateral stiffness is the key to large steer angle cornering force - which is improved with a wider rim. Hence, the inflated shape of said tire on a wider rim is more trapezoidal than when mounted on a narrower rim where the inflated shape would be more rounded. Think of a house on a wide foundation being more stable than a house on a narrow foundation. A pyramid is more stable than an inverted pyramid. I digress. PS: The rule of thumb in motor racing is the wheel width should be at least 1 inch wider than the tread width. There is a point of going too far with this concept as shown in the image below.
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https://grassrootsmotorsports.com/articles/wheel-width-is-wider-always-better/

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Wait so back on this for a second. The 295 Bridgestone is 10.6 tread width, the 285 is 10.1. So does that mean that the 285 is the better option here with the 11” rim?

[DrFerry]

Originally Posted by kolosy

Wait so back on this for a second. The 295 Bridgestone is 10.6 tread width, the 285 is 10.1. So does that mean that the 285 is the better option here with the 11” rim?

Yes it does if you're looking to extract the most cornering power, with lower reciprocating mass (flywheel effect) and lower un-sprung mass (lower inertia i.e. more responsive) from the tire and rim assembly. This is because when using the rule of thumb, mentioned earlier, the 295 is better suited for an 11.5 in terms of racing performance (which is more than just grip) though of course the 295 can be mounted on the 11 inch wide rim. However, the 295 won't be as efficient as the 285 on the same 11 inch wide rim. For example: the 285 assembly will have lower rolling resistance, and have lower mass than the 295 - assuming identical aspect ratio and rim diameter. PS: Cornering power is the area under the curve of cornering force versus slip angle.

[amg6975]

The RE71RS is fast a frick but will wear pretty quick and can't hammer lap after lap. The ECF is the opposite, not nearly as fast but lasts forever and you can run the hard for many laps. They will heat cycle into a 600TW before they wear out.

My take: Falken RT660+ is the best parts of both of those tires. Faster than the ECF, longer lasting and more consistent than the RE71RS. Also probably cheaper than either.

[DrFerry]

Originally Posted by e92BMW///M3

I haven't tried the ECF, but I have enjoyed the RE71RS. Was reading up about the Hoosier TrackAttacks as well, but think my next tires will be back to the RE71RS.

You might want to look at the new Hoosier RCES just recently introduced in January 2025. They come in size 275/35R17 which can be mounted on a 9 - 11 inch wide rim. Here's the Hoosier press release (also attached as pdf).

PRODUCT BULLETIN 1/7/2025
New Hoosier Spec Tire for NASA - RCES
Lakeville, Ind. - Beginning in 2025, NASA has chosen Hoosier Racing Tire’s RCES tire as the official specification tire for the following classes: 944 Spec, American Iron, Camaro-Mustang Challenge, Spec Iron, and Spec [BMW] E46. The RCES, which stands for Road Course Endurance Spec, is an entirely new product. Designed to meet the demands of spec-class racing, the tire offers enhanced durability and a consistent performance curve both within a single session and across multiple heat cycles.

The RCES tire is available in multiple sizes:
P225/50ZR15 $250.82
P245/40ZR17 $315.10
P275/40ZR17 $335.20
P275/35ZR18 $387.98

For more information or to place an order, please contact your nearest Hoosier Racing Tire Distributor. A complete list of locations can be found at www.hoosiertire.com

https://drivenasa.com/road-racing/hoosier-rces-tire/
https://www.tirerack.com/tires/hoosier-rces
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It sounds like an R7 with much better wear life. UTQG Treadware = 40

[D_SheerDrivingPleasure]

Originally Posted by DrFerry

You might want to look at the new Hoosier RCES just recently introduced in January 2025. They come in size 275/35R17 which can be mounted on a 9 - 11 inch wide rim. Here's the Hoosier press release (also attached as pdf).

PRODUCT BULLETIN 1/7/2025
New Hoosier Spec Tire for NASA - RCES
Lakeville, Ind. - Beginning in 2025, NASA has chosen Hoosier Racing Tire’s RCES tire as the official specification tire for the following classes: 944 Spec, American Iron, Camaro-Mustang Challenge, Spec Iron, and Spec [BMW] E46. The RCES, which stands for Road Course Endurance Spec, is an entirely new product. Designed to meet the demands of spec-class racing, the tire offers enhanced durability and a consistent performance curve both within a single session and across multiple heat cycles.

The RCES tire is available in multiple sizes:
P225/50ZR15 $250.82
P245/40ZR17 $315.10
P275/40ZR17 $335.20
P275/35ZR18 $387.98

For more information or to place an order, please contact your nearest Hoosier Racing Tire Distributor. A complete list of locations can be found at www.hoosiertire.com

https://drivenasa.com/road-racing/hoosier-rces-tire/
https://www.tirerack.com/tires/hoosier-rces
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It sounds like an R7 with much better wear life. UTQG Treadware = 40

Interesting. I missed that tire release. Meanwhile, the R7 in the same size sells on TR for $482.

[kolosy]

Originally Posted by amg6975

The RE71RS is fast a frick but will wear pretty quick and can't hammer lap after lap. The ECF is the opposite, not nearly as fast but lasts forever and you can run the hard for many laps. They will heat cycle into a 600TW before they wear out.

My take: Falken RT660+ is the best parts of both of those tires. Faster than the ECF, longer lasting and more consistent than the RE71RS. Also probably cheaper than either.

What’s interesting is that the 285 of the rt660+ has a tread width of 10.4 but according to the spec sheet can only go on a 10.5 wheel.

Edit — actually same with the Re71rs in 285/30

[DrFerry]

Originally Posted by kolosy

What’s interesting is that the 285 of the rt660+ has a tread width of 10.4 but according to the spec sheet can only go on a 10.5 wheel. Edit — actually same with the Re71rs in 285/30

The published rim width range is really referring to the "recommended rim width range". The recommended range is determined by an engineering design formula specified by industry organizations such as the Tire & Rim Association (T&RA) in the USA, as well as JATMA (Japan Automobile Tyre Manufacturers Association) in Japan, and the ETRTO (European Tyre and Rim Technical Organization) in the Europe. Some consumers do stray from the recommended rim width range for various reasons (see links below). The 30% aspect ratio of the 285/30R18 size you mention is probably the main factor in limiting the recommended rim range to a 10.5in rim maximum for street applications. Based on the rim width rule of thumb, I mentioned earlier for motor racing (i.e. Tread width + at least 1 inch), the 285 should perform well on an 11 inch wide rim (10.4in Tread Width + 1in = 11.4in). However, if you have any doubt, contact Falken at technical@falkentire.com because the RT660+ is basically a sort of hybrid tire design i.e. a street tire designed for track use.
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https://www.tirerack.com/upgrade-gar...nge-for-a-tire
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https://rennlist.com/forums/993-foru...on-11-rim.html
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https://www.evolutionm.net/forums/mo...-11-wheel.html
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[bipp]

Is the rationale that the ideal width for a 285/30 11", or is the ideal width for an 11" 285/30?

If I recall correctly, maximizing wheel width when possible when tire width is limited is optimal, but (within reason) increasing tire width is generally beneficial (i.e. 285 or 295 on a 10.5, 295 on a 11).

I recall Bimmerworld was running the 315-wide ECFs on a 11" for GTMore at one point. https://f80.bimmerpost.com/forums/sh...34&postcount=2

[DrFerry]

Originally Posted by bipp

Is the rationale that the ideal width for a 285/30 11", or is the ideal width for an 11" 285/30?

If I recall correctly, maximizing wheel width when possible when tire width is limited is optimal, but (within reason) increasing tire width is generally beneficial (i.e. 285 or 295 on a 10.5, 295 on a 11).

I recall Bimmerworld was running the 315-wide ECFs on a 11" for GTMore at one point. https://f80.bimmerpost.com/forums/sh...34&postcount=2

It's not really a discussion about ideal width, but rather about options kolosy might have available to him given his product preferences and the sizes available with regard to his recent investment in 18X11 wheels. Yes, maximizing wheel width in a track environment is desirable. As is increasing tire width, but there is a point of diminishing returns in terms of un-sprung mass, reciprocating mass, rolling resistance and aero' drag. Example: A 345/25R19 may yield slower lap times than a 305/30R19 on an E9X M3 assuming one could accomplish such a fitment.

[kolosy]

Originally Posted by DrFerry

It's not really a discussion about ideal width, but rather about options kolosy might have available to him given his product preferences and the sizes available with regard to his recent investment in 18X11 wheels. Yes, maximizing wheel width in a track environment is desirable. As is increasing tire width, but there is a point of diminishing returns in terms of un-sprung mass, reciprocating mass, rolling resistance and aero' drag. Example: A 345/25R19 may yield slower lap times than a 305/30R19 on an E9X M3 assuming one could accomplish such a fitment.

Yeah I’m leaning toward a 295 tire tbh, even though it’s less than the rule of thumb. With all the weight reduction, the cg has shifted forward enough that I’m definitely having on throttle traction issues and I’m assuming a wider contact patch is more important for straight line acceleration.

Also 295 square is cool

[DrFerry]

Originally Posted by kolosy

Yeah I’m leaning toward a 295 tire tbh, even though it’s less than the rule of thumb. With all the weight reduction, the cg has shifted forward enough that I’m definitely having on throttle traction issues and I’m assuming a wider contact patch is more important for straight line acceleration.

Also 295 square is cool

Cool. If you can fit a 295/30R18 square on the 11 inch rims under the fenders without rubbing the suspension, then go for it. A wider contact patch (east - west orientation) improves cornering grip. A longer contact patch (north - south) orientation improves acceleration and braking grip. It's why dragsters (that don't go round corners) run relatively narrow tire section and tread widths for the power and torque they produce. It's because all they need is straight line traction (see photo).

Given the center of gravity shifting forward you probably need to start thinking about brake bias and adding aero loading (a rear wing). Assuming the same load and pressure the contact patch will have the same area between sizes BUT the contact patch shape changes when the tire size changes. Again, assuming the same load, pressure and rim width.

Example: If a racecar weighs 3000lb / 4 tires = 750lb load at each tire - assuming a 50/50 weight distribution. If the inflation pressure is 30psi then 750lbs/30psi = 25 square inches for the contact patch area. Assuming the same pressure and load: Changing sizes only changes the contact patch shape, but not the contact patch area. It means a narrow tire will have a more longitudinal (north - south) contact patch orientation which is good for braking and acceleration. Assuming the same inflation pressure and load, a wider tire will have a wider contact patch shape (generally speaking - excluding drag tires) and be better for cornering (lateral) grip.
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[kolosy]

Ended up pulling the trigger on a set of RT660+ with heat cycling in 295/30. Hope they fit 🫣

[bipp]

Originally Posted by kolosy

Ended up pulling the trigger on a set of RT660+ with heat cycling in 295/30. Hope they fit 🫣

If you're open to 295, try out the Nankang CRS v2 - not sure if you've tried yet. I got 6 days out of mine with maybe ~4000 additional street miles since I daily on them. They're incredibly consistent throughout a session once they come up to temp, but your outlap is a little sketch if it's a colder day - they have very little cold grip. They do like lower pressures and seem to not like recovering if overdriven, I find that 32 on a full-weight car they are great but past 35 it seems like they go out a little. I would say that they are likely fast to cords, but my last day on them was a little edgy (which could also be attributed to the cold).

There's also the new Vitour Tempesta P1's to try out.

[bigjae1976]

Originally Posted by amg6975

The RE71RS is fast a frick but will wear pretty quick and can't hammer lap after lap. The ECF is the opposite, not nearly as fast but lasts forever and you can run the hard for many laps. They will heat cycle into a 600TW before they wear out.

My take: Falken RT660+ is the best parts of both of those tires. Faster than the ECF, longer lasting and more consistent than the RE71RS. Also probably cheaper than either.

That's a good take.

I would say that compared to Toyo RRs, the 660s have much better braking but the rear end is not as good. The RRs were the opposite - the front end grip falls off a lot faster.

The 660s take a solid 2 laps to warm up, RRs never took more than 1. And new 660s are total shit for the first 1/2 lap. I almost spun in the hot pit.

But the 660s feel faster than the RRs out the box. Seems like the 660s don't fall off like the RRs do. I have 17 heat cycles on the 660s and they are definitely faster than RRs with 17 heat cycles. They are wearing great too!

At least for me, the 660s got a little greasy and then then just flat out gave up. I was punishing the RF tire and then all of the sudden it was understeer ABS ice mode death skid which my car has never done before. I also don't like the consistency of the rear tires. There is a left turn where I have consistently, lap after lap, just 4 wheel slide into and then lift and the rear end oscillates into a right turn...I don't even have to turn the steering wheel. I've done it over 100 times. These 660s...sometimes the rear end would not break loose enough, other times I would be sideways.

The 660s are a terrible NASA ST/TT tire. But they are cheap, seem to last and are decently consistent. 275/40R17s are $1100 incl tax. Can't be mad at that! These would be an awesome tire if I wasn't coming out of every turn sideways 45 degrees or with no slip at all.

The RRs are a little more, fall off in terms of grip but are much easier to drive or I'm just really familiar with them.

I'm thinking I might try the Toyo Rs next.

[BoilerUP]

I've only got two sessions on the Proxes R, but they compare pretty dang favorably so far with the 71RS for a DE tire.

[tsk94]

Originally Posted by BoilerUP

I've only got two sessions on the Proxes R, but they compare pretty dang favorably so far with the 71RS for a DE tire.

Have you used the RR as well? If so, how do they compare?

[BoilerUP]

Originally Posted by tsk94

Have you used the RR as well? If so, how do they compare?

I have not used the RR.

GrassrootsMotorsports testing showed the ProxesR was a substantial improvement from the RR so the ProxesR is where I started.

[kolosy]

So I’ve got a set of 18x11 et30 wheels sitting here, with 295/30 rubber. A 15mm spacer gives me enough clearance on the strut side but then the tire sticks out a solid inch past the front fender. I assume this is a nonstarter, but now I’m not sure what to do. I can return the tire rack tires and just be out shipping and mounting and get 285s instead.. that should let me use a smaller spacer (or none at all), right? Or am I sol without going wide body?

[DRLane]

Originally Posted by kolosy

So I’ve got a set of 18x11 et30 wheels sitting here, with 295/30 rubber. A 15mm spacer gives me enough clearance on the strut side but then the tire sticks out a solid inch past the front fender. I assume this is a nonstarter, but now I’m not sure what to do. I can return the tire rack tires and just be out shipping and mounting and get 285s instead.. that should let me use a smaller spacer (or none at all), right? Or am I sol without going wide body?

You're going to be tight with 11" wheels even with 285. That said, I fit 295 R7s on 11" wheel with a 25mm spacer. It was close (like couple mm) and I shaved the tire savers off with razor blade. But it was different suspension and thus I wasn't contending with the spring collar. Could pull in the top with more static camber?

[kolosy]

Originally Posted by DRLane

You're going to be tight with 11" wheels even with 285. That said, I fit 295 R7s on 11" wheel with a 25mm spacer. It was close (like couple mm) and I shaved the tire savers off with razor blade. But it was different suspension and thus I wasn't contending with the spring collar. Could pull in the top with more static camber?

i'm at -3.5 already, could maybe go to -4 but i can't see that adding much in the way of space.

i'm tempted to try the 285s, just would hate to be in the same spot after dealing with all that.

[DRLane]

Originally Posted by kolosy

i'm at -3.5 already, could maybe go to -4 but i can't see that adding much in the way of space.

i'm tempted to try the 285s, just would hate to be in the same spot after dealing with all that.

That’s suspension doesn’t look like it gives a lot of height adjustment / spring length options?

[kolosy]

Originally Posted by DRLane

That’s suspension doesn’t look like it gives a lot of height adjustment / spring length options?

i don't have a good frame of reference on that. it does seem to be at the very top of the ride height range (goes with my other concern that the guy that ripped me off on a corner balance also screwed up my ride height)

it's just the ohlins dedicated track setup from 3DM