For those running 235's at the front.

[MetalSpikeRacing]

For those guys running 235's up front, do you guys have eccesive rub?
I am planning to replace my 215's with 235's ofcourse, just want to know how bad is it?

My front specs are 17x8 +48. 215/40/17 RT-615's( which we now they are narrower than your avarage performance tire.)

I am thinking I could compensate inner rubbing with spacers...?.

Thanks for the input.

-MSR

 

[rasir_x]

I have 235/40/17 up front and 285/30/18 in the rear as my tire setup and i only rub at full lock. Since i rarely turn at full lock it has not bothered me. I do have spacers to clear my Brembo brakes though.

Example: If turning left at full lock my rubbing comes from the left tires outside face rubbing the fender liner near the clutch pedal.

 

[MetalSpikeRacing]

Nice, what is your wheel width at the front an offset?

Thanks,

-MSR

 

[stevenlee]

I'm running 235's in the front on 8 inch x 17 inch wheels. I removed the front plastic shrouds. I modified the plastic wheel well liners by cutting off the rear inner section and remolded the liner with a hot air gun and a large wet sponge. The tire rubbed a little at the back inner area of the wheel well which was easily adjusted with a short, SMALL sledge hammer. Now there's no rubbing.

You will like the added braking performance of a wider front tire in addition to the increased cornering traction.

I'm running 295's on the rear with 10.5 inch wide wheels and they seem to work well with the fronts.

 

[nsxtasy]

You will like the added braking performance of a wider front tire in addition to the increased cornering traction.

Wider tires don't affect braking performance.

 

[MetalSpikeRacing]

I'm running 235's in the front on 8 inch x 17 inch wheels. I removed the front plastic shrouds. I modified the plastic wheel well liners by cutting off the rear inner section and remolded the liner with a hot air gun and a large wet sponge. The tire rubbed a little at the back inner area of the wheel well which was easily adjusted with a short, SMALL sledge hammer. Now there's no rubbing.

You will like the added braking performance of a wider front tire in addition to the increased cornering traction.

I'm running 295's on the rear with 10.5 inch wide wheels and they seem to work well with the fronts.

Thank you very much for the info, what is your offset please. I ill be using 235's.

Ill let you guys know how it goes on the spring.

 

[Ponyboy]

I run 235/40/17's up front and rub at full lock. Removed linining seemed to help a bit. I don't think there's anyway to get around rubbing at full lock if you're going to run a 235 up front. Maybe you can use a BUFF hammer to the wheel well to add some clearance.

 

[stevenlee]

My fronts are CE28N's 17x8. Offset is +38. Tires are 235-40-17.
Rears are 18x10.5. Offset is +45. Tires are 295-35-18.
They fit perfectly in my opinion. Tire is flush with the top of the rear fender.

I have virtually no rubbing. I did cut out some of the wheel well liner and mold it with a heat gun and a wet sponge.

I have short gears and JDM R&P. I did recalibrate the speedo for the larger tires. I also removed the traction control unit.

 

[barretire]

Some really good info in this post. Thanks..

 

[MetalSpikeRacing]

Hey Stevenlee, how about a couple pics of the front wheels.
I would like to see how they look.

-MSR

 

[stevenlee]

MSR, I just put my car on a lift and pulled the transmission last night so I can't take good pics of the front 235 tires for a while. Here are a few general photos that include the front and rear tires.

 

[Coz]

I ran 235x40x17 and 285x35x18 on both my Green and Red NSX's for years without problems. Street and track.
Would get a slight rub at full wheel lock, which didn't matter since it was very rare I was at full lock anyway.
Used Volk CE28's and RE-30's and cleared big brakes and Brembo's with no problems and no spacers.

 

[MetalSpikeRacing]

Thanks for the input guys and the pics, I will make sure to post plenty of pictures when I put my tires on in the spring.

-MSR

 

[Greg@R-Tuned]

don't do it, you'll regret it.

if you have to, you might want to take out the fender liners, but rocks might be an issue.

im pretty sure i'm going back to the 215/275 setup

 

[Jack Sparrow]

don't do it, you'll regret it.

if you have to, you might want to take out the fender liners, but rocks might be an issue.

im pretty sure i'm going back to the 215/275 setup

Any reasons why you suggest against the 235 front setup?

 

[ScienceofSpeed]

The problem is that the 235/40-17 is 24.4" in outer diameter compared to the factory size of 23.8". Unfortunately, it's one of the only available sizes for the front of our car if you want to go wider than stock. Other more ideal sizes like 225/35-17 and 245/35-17 are smaller in diameter, but very rare to find. It is worth dealing with for high performance applications though. That additional width makes a pretty dramatic improvement in braking and cornering grip.

Increasing the distance away from the center line of the car with spacers actually makes the situation worse because you are increasing the arc of the tire's travel. Your width and offset is actually quite good for this size tire.

The tires will generally hit in two places with your width and offset: the A/C condenser plastic shroud's louvers in the front and a raised ridge and one of the pinch welds in the sheet metal in the rear. This will happen under sharp load speed turns (like turning into a parking space) but isn't a problem once you're up to speed making broader turns. To alleviate these problems, you can remove or modify the plastic shroud, use a plastic mallet to smooth out the ridge in the sheet metal, and grind off some of the excessive material at the pinch weld. It sounds evasive, but it is actually very minimal work.

Now for the sales pitch... We came out with these wheels specifically for running wider tires like this. The offsets are optimal and the larger width (8.5) stretches the tire slightly to reduce it's overall diameter. This is probably the best combination of width and offset, but even with these, some minor rubbing would be expected.


http://scienceofspeed.com/products/exterior_performance_products/NSX/ScienceofSpeed/VolkRacingTE37/

regards,
-- Chris

take care,
-- Chris

 

[ScienceofSpeed]

Wider tires don't affect braking performance.

Wider tires make an improvement in braking performance in the same way that a wider tire would reduce tire slip under acceleration. The contact patch increases with a larger tire. Although a smaller tire has the same amount of force exerted on the road surface compared to a larger tire (assuming the same weight of the vehicle) asphalt is irregular, and the larger contact patch allows the wider tire to more evenly distribute it's load on the available contact surfaces and therefore heat from friction. By reducing heat at these contact surfaces, you eliminating the small moment slipping events from losing coefficient of friction.

-- Chris

 

[FXMDBilly]

Wider tires make an improvement in braking performance in the same way that a wider tire would reduce tire slip under acceleration. The contact patch increases with a larger tire. Although a smaller tire has the same amount of force exerted on the road surface compared to a larger tire (assuming the same weight of the vehicle) asphalt is irregular, and the larger contact patch allows the wider tire to more evenly distribute it's load on the available contact surfaces and therefore heat from friction. By reducing heat at these contact surfaces, you eliminating the small moment slipping events from losing coefficient of friction.

-- Chris

Technically if the weight of the car remains constant, and the tire pressure remains constant, wider tires will have the same contact patch as a narrower tire. But the contact patch will be wider and shorter. A tire's contact patch primarily changes with an increase in weight (or downforce) on the car or lower tire pressures -allowing the tire to smush and flatten out.

This is one reason why I don't like the stock 33/40psi stagger on modern 215/235 front and 255-295 rear tires. Having the smaller front tires at a low 33psi increases its contact patch and front grip, while the higher pressure rear tire reduces the rear contact patch and thus make the car oversteer more than if both front and rear were set at the same optimum pressure -making the rear contact patch much wider than the front which gives the car stability and reduces oversteer. While tire pressures can be fine tuned at the track, I don't stray too far from a non-staggered tire pressures.

I do probably have to agree that 235 front tires improve deceleration over 215s on the front of the NSX, but if the brake system isn't capable of maxing out a 215's grip level (if the brakes are the limiting factor with street pads), then a wider 235 won't improve the braking ability. I do firmly believe and stand by that wider front tires increased front grip when cornering.


Billy

 

[W]

Technically if the weight of the car remains constant, and the tire pressure remains constant, wider tires will have the same contact patch as a narrower tire. But the contact patch will be wider and shorter. A tire's contact patch primarily changes with an increase in weight (or downforce) on the car or lower tire pressures -allowing the tire to smush and flatten out.

I think technically what you are stating is true if tires were more like flimsy balloons but they aren't. A performance tire at 20 psi has a different contact patch and area than that of a non-performance tire at 20 psi due to differences in sidewall stiffness and whatnot.

 

[Jack Sparrow]

Technically if the weight of the car remains constant, and the tire pressure remains constant, wider tires will have the same contact patch as a narrower tire. But the contact patch will be wider and shorter. A tire's contact patch primarily changes with an increase in weight (or downforce) on the car or lower tire pressures -allowing the tire to smush and flatten out.

This is one reason why I don't like the stock 33/40psi stagger on modern 215/235 front and 255-295 rear tires. Having the smaller front tires at a low 33psi increases its contact patch and front grip, while the higher pressure rear tire reduces the rear contact patch and thus make the car oversteer more than if both front and rear were set at the same optimum pressure -making the rear contact patch much wider than the front which gives the car stability and reduces oversteer. While tire pressures can be fine tuned at the track, I don't stray too far from a non-staggered tire pressures.

I do probably have to agree that 235 front tires improve deceleration over 215s on the front of the NSX, but if the brake system isn't capable of maxing out a 215's grip level (if the brakes are the limiting factor with street pads), then a wider 235 won't improve the braking ability. I do firmly believe and stand by that wider front tires increased front grip when cornering.


Billy

So is everyone in agreement that the optimal sizing for the front tire/wheel combo should be 235/40-17X8.5? If so, what would be the optimal size (performance being the only criteria) for the rear tire/wheel for the NSX (Non-WB)?

 

[FXMDBilly]

I think technically what you are stating is true if tires were more like flimsy balloons but they aren't. A performance tire at 20 psi has a different contact patch and area than that of a non-performance tire at 20 psi due to differences in sidewall stiffness and whatnot.

I'm not sure what you mean by 'performance' vs. 'non-performance' tires but most street and R-compound semi-slicks do not operate at 20psi (maybe it was an arbitrary number ) but rather in the 30-40psi range.

Again, given constant tire pressures and vehicle weights, different size tires will not increase or decrease the contact patch. Air in the tire supports the tire and the weight of the car has a certain deformation on the tire. What wider tires do allow is for lower pressures relative to narrow tires which does increase the contact patch. They also increase the total surface area of the tire thus distributing cornering load over a wider area. Its important to use a probe-type tire pyrometer to determine if your tires are too narrow or wide -tires are overheating or not getting up to temperature.

So is everyone in agreement that the optimal sizing for the front tire/wheel combo should be 235/40-17X8.5? If so, what would be the optimal size (performance being the only criteria) for the rear tire/wheel for the NSX (Non-WB)?

Most 235/40-17 tires out there are on 17x8" wheels. I run them on my 17x7.5" 5Zigen ProRacer GN+ wheels, but the 235 on a 8.5" wide wheel is a more ideal tire-wheel sizing.

Keeping this ratio and the commonly-used stagger on NSXs, would be a 275 on a 10" wide rear wheel or a 285 on a 10.5" wide rear wheel.


Billy

 

[Jack Sparrow]

Most 235/40-17 tires out there are on 17x8" wheels. I run them on my 17x7.5" 5Zigen ProRacer GN+ wheels, but the 235 on a 8.5" wide wheel is a more ideal tire-wheel sizing.

Keeping this ratio and the commonly-used stagger on NSXs, would be a 275 on a 10" wide rear wheel or a 285 on a 10.5" wide rear wheel.


Billy

Sweet, thanks Billy.

 

[nsxtasy]

I think technically what you are stating is true if tires were more like flimsy balloons but they aren't. A performance tire at 20 psi has a different contact patch and area than that of a non-performance tire at 20 psi due to differences in sidewall stiffness and whatnot.

Nope. Billy is correct. The size of the contact patch depends on the weight on the tire and the inflation in the tire.

As a test, the Tire Rack measured the contact patch for the same tire model in two different sizes, one significantly wider than the other, placed on the same car with the same inflation in the tires. The difference in the area of the contact patch between the two tires was less than their measurement error, which they estimated as 2 percent.

 

[W]

Nope. Billy is correct. The size of the contact patch depends on the weight on the tire and the inflation in the tire.

As a test, the Tire Rack measured the contact patch for the same tire model in two different sizes, one significantly wider than the other, placed on the same car with the same inflation in the tires. The difference in the area of the contact patch between the two tires was less than their measurement error, which they estimated as 2 percent.

You might want to re-read my statement as I was more specific than the general discussion. My statement about sidewall stiffness is between two different tire models, not the same tire model in a different size. BTW, my example tire pressures were purposely low to help the user visualize a deflated tire and how sidewall stiffness comes into play. In the end, I was hoping that there was going to be some discussion as to what other tire characteristics affect a tire's braking/accerating ability since these types of discussions tend to be primarily focused on air pressure/shape of contact patch.

 

[FXMDBilly]

You might want to re-read my statement as I was more specific than the general discussion. My statement about sidewall stiffness is between two different tire models, not the same tire model in a different size. BTW, my example tire pressures were purposely low to help the user visualize a deflated tire and how sidewall stiffness comes into play. In the end, I was hoping that there was going to be some discussion as to what other tire characteristics affect a tire's braking/accerating ability since these types of discussions tend to be primarily focused on air pressure/shape of contact patch.

I get what you are trying to say about the sidewalls but you are assuming that lower pressures deflate and deform a tire width wise only when the contact patch grows in length (forweard/aft) more than width with lower pressures. As Ken stated, Tire Rack did a test on this.

In regards to 2 different tires, one with a stiff sidewall and the other with a soft one should also have roughly the same static contact patch given consistent vehicle weight and tire pressures. Air supports the tire/car and the vehicle weight is the other aspect that determine contact patch size. Now on the other hand (what you might be referring to), a tire with a rounder profile (Yokohama A048/Toyo R888) could possibly have a smaller contact patch than a more square profile of a Nitto NT01 or BFG R1 given same car and pressures. While at most this there would be a small difference in contact patch size, the shape/handlong characteristics can be greatly affected. I would have to do a similar test that TireRack did on daid tires to see how substantial or insignificant the difference is. I have the feeling like TR's results, it shouldn't be a big change.

What aspects of a tire increase braking performance and acceleration? A general rule of thumb is the LARGER the RADIUS of the tire, the LONGER the contact patch (relative to width) while the wider the wheel/tire has a wider but shorter contact patch which is better for lateral grip. There is a reason ejy top-fuel dragsters have tall skinny tires while F1 cars have shorter, wider tires.


Billy