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Discussion Starter #1
OK much to say here, will be brief as possible.
2015 Challenger, third car, "date night" car etc. As it turns out this is an excellent road trip car and I am looking to improve touring performance. First road trip last year on two lane black top, cruising at 75 mph to New Mexico and back, 34 mpg, just very comfortable and fun.
Just completed a 2200 mile road trip in five days, three driving days, two days at locations..... as we drove "through Mexico".
Intestate type highways at speeds 90-100 mph sustained, need to do some upgrades.
V6 car, factory 7.5 x 18 rims and 235/55 R18 tires. Running tire pressure was 45 psi.

Problems:
Brakes get a little hot and noisy above 85 mph.
Need a little better tire.
Better aero at speed.

We like the light feel of the V6 car. Wish to keep the stock rims.
Are the 7.5" rims too narrow or can we mount a better tire?
Suggestions for tire and size, mostly dry, no snow.

Suspension kit, looked at factory stage two.. wish to lower a bit, OEM or aftermarket suggestions?

Brakes, again factory has pad and rotor upgrade, any aftermarket suggestions? I don't think new calipers are necessary, performance pads and rotors should fix.

Chin spoiler??

Cold air intake for V6 any benefit or just leave it alone?

Thanks
 

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2020 Dodge Challenger Hellraisin Scat Pack
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OK much to say here, will be brief as possible.
2015 Challenger, third car, "date night" car etc. As it turns out this is an excellent road trip car and I am looking to improve touring performance. First road trip last year on two lane black top, cruising at 75 mph to New Mexico and back, 34 mpg, just very comfortable and fun.
Just completed a 2200 mile road trip in five days, three driving days, two days at locations..... as we drove "through Mexico".
Intestate type highways at speeds 90-100 mph sustained, need to do some upgrades.
V6 car, factory 7.5 x 18 rims and 235/55 R18 tires. Running tire pressure was 45 psi.

Problems:
Brakes get a little hot and noisy above 85 mph.
Need a little better tire.
Better aero at speed.

We like the light feel of the V6 car. Wish to keep the stock rims.
Are the 7.5" rims too narrow or can we mount a better tire?
Suggestions for tire and size, mostly dry, no snow.

Suspension kit, looked at factory stage two.. wish to lower a bit, OEM or aftermarket suggestions?

Brakes, again factory has pad and rotor upgrade, any aftermarket suggestions? I don't think new calipers are necessary, performance pads and rotors should fix.

Chin spoiler??

Cold air intake for V6 any benefit or just leave it alone?

Thanks
Tires inflated to 45psi are over inflated unless (maybe) you were driving a fully loaded car.

How can brakes get hot at speed unless you use them? I would think the brakes should handle at least one haul down from 85mph to a much slower speed, even a stop without manifesting any fade. If this is not the case, wow, but of course you need to address this.

On a related note be sure to flush/bleed the brake hydraulic system every once in a while. While it appears Dodge doesn't give a brake fluid flush/bleed schedule with other cars I have found every 2 years to be a good interval.

If you decide to upgrade the brakes the factory upgrade kit I think deserves some consideration due to (among other things) that it should bolt up with the minimum amount of trouble. 'course, an aftermarket brake kit doesn't necessarily have to be any different.

Can't help you with specific tire wheels/tires recommendations. I know from my road trips the bigger the sidewall the better the ride, the quieter the ride. My 2002 VW Golf TDi with its 16" wheels/tires was like riding a magic carpet compared to covering the same roads in my Boxster (17" wheels/tires), my GTO and Turbo (18" wheels/tires). While I haven't been out in my Hellcat I expect those 20" tires are going to roar...

You want to avoid going to too an exotic tire if you can avoid it. This in case you have a flat tire you want to be able to source a suitable tire pronto. 'course, if you can arrange to carry a full sized spare... (The good old VW had a full size spare tire.) Another consideration is some automakers -- I do not know if Dodge is one -- have some guidelines about mixing a new tire (new due to replacement) with a worn tire (not even worn out) on the other side. If Dodge (or the tire maker) has some guideline regarding this if you get a flat tire out in the boonies you may be looking at having to replace two tires.

Not suggesting you venture out with dime store tires on the car but what seems like a good idea around town hundreds of miles out in the middle of nowhere and finding a tire store/shop only to learn one has to wait a day or two for the proper tire to arrive or worse learning the tire distributor has the tires back ordered and having to possibly replace all 4 tires can have you wishing you have stuck with a more readily available tire but of course one with the proper speed/load/wear rating.

Intelligent aerodynamic enhancements can help. A good air dam/chin spoiler that cuts down on air flowing under the car and helps direct air through the radiator can improve engine cooling although I don't believe you mentioned any real problem with this. Trouble is finding a good add on vs. just one that looks "good". You have to be aware that the air dam/chin spoiler is at risk of damage from road debris. That lump of road kill the car passes over without contact with the stock bumper aerodynamics may tear up the air dam/chin spoiler.

Road clearance also needs to be considered when contemplating installing a high performance suspension which lowers the car (and also stiffens the ride). If the factory suspension is in good working order I'd leave this alone.

Chances are the engine already has a pretty good air intake system that once the car is up to speed and heat soak has had time to dissipate the intake air temperature is pretty close to ambient. For an air intake system you want one that filters out all dirt/dust -- in my road trips it was not uncommon for me to encounter mini dust storms and having a real good engine (and cabin) air filtration system was critical -- and is immune to water when driving through heavy rain, encountering standing water or when vehicles pass your car and throw out huge sprays of water. In this regard, as with intake air temperature, the stock air filtration system is probably the best system.
 

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2016 R/T Scat Pack
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You might consider lowering your car a bit, getting the SRT chin spoiler, and maybe an aftermarket rear diffuser is you want better aero.

When I say a bit I mean, I'd go no lower than stock Scat Pack suspension.
 

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I'm just imaging in my mind what a great trip you just had. I would love to be driving 90-100 and not get put in jail. :surprise:

What got my attention was the 45 PSI tire pressure. If the tire is too hard, it won't be able to grip going through windy roads so well. I would think 35 PSI is a sweet spot. Also, with 7.5 inch wide wheels, you really are limited there if you want to go with wider tires for more grip.

As far as cold air intake, that is purely cosmetic. It looks nice, but if you keep the stock intake that won't hurt you.
 

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Discussion Starter #5
There seems to some misinformation about tire pressures expressed in this thread, so I have included an article from the Tire Rack website to explain the whys of high speeds and higher tire pressures.
Some of my other cars have high speed operation tire pressures right in the owner's manual.

My tires are 235/55 R18 Michelin whatevers...
Sidewall Max is 51 psi cold.
I set them sitting for a couple days cold to 42psi.
Ain't care what the idiot sticker says.
I recorded a maximum psi of 45 on the vehicle monitor while driving well into triple digits.

Here's the article:



Air Pressure / Load Adjustment for High Speed Driving


Driving at high speeds certainly helps make a trip go faster; just ask any driver who has gone "flat out" on the German Autobahn. However, with the exception of events like the Silver State Classic's Open Road Rally or a driver's school on a racetrack, it's difficult to find a place that allows unlimited speeds! Remember, the tires on the vehicle should be properly sized, inflated and inspected if you plan to drive fast because the tires will be subjected to tremendous stresses.

Because of the weight they bear, pneumatic tires' sidewalls bulge and their treads flatten as they roll into contact with the road. This results in dimensional difference between the tire's "unloaded" radius (i.e., between the center of the axle and the top of the tire) and its "loaded" radius (between the center of the axle and the road). The engineers call the difference between the two radii "deflection." Increasing vehicle speed will cause the tires to deflect quicker, and increasing vehicle load will cause the tires to deflect farther (if tire pressure isn't increased).

Consider that a 225/45R17 91W Standard Load tire (with a 25-inch overall diameter) will roll about 835 times every mile. Although the number of tire revolutions per mile doesn't change significantly as speed climbs, the revolutions per second become daunting. While the 225/45R17 91W-sized tire rolls a rather comfortable 7 times per second at 30 mph, this same tire will roll about 16 times per second at 70 mph on an American Interstate and an amazing 35 times per second during a 150 mph cruise on the German Autobahn. Thirty-five tire revolutions per second means that the tire is transforming from its unloaded to loaded shape and back every 3/100th of a second.

The European Tyre and Rim Technical Organization (ETRTO) establishes the standards for tires sold in Europe, and recognizes that the tire's deflection must be minimized and controlled in order to surpass high speed driving stresses. In order to accomplish this, the tire inflation pressure recommendations and the tire's rated load capacities are customized when speeds exceed 160 km/h (99 mph) for all tires up to and including a V-speed rating, and when speeds exceed 190 km/h (118 mph) for all tires that are Z-speed rated and above.

The Autobahn's unlimited speed opportunities explain why many German vehicles identify alternate tire inflation pressures to accommodate higher than North American highway speeds and heavier than typical two-passenger loads. In order to accommodate higher speeds, the tire size and inflation pressure recommendations are tuned beyond what is branded on the tire's sidewalls. These increases in recommended tire pressure are usually determined by agreement between the vehicle and tire manufacturers. In the absence of such an agreement, apply the following:

Beginning with the vehicle manufacturer's recommended tire pressure for normal highway conditions, tire inflation pressures are initially increased and then the tire's rated load capacities (branded on the sidewalls) are reduced as speeds climb.

In our example shown below, the vehicle manufacturer's recommended 35 psi for a 225/45R17 91W Standard Load tire installed on a vehicle initially rises in 1.5 psi increments for every 10 km/h (6.2 mph) increase in speed until the inflation pressures max out with an increase of 7.5 psi when the vehicle's top speed has increased 50 km/h (31mph). Then as the vehicle's top speed continues to climb, the rated load capacity of the tire is reduced in 5% increments for every additional 10 km/h until the vehicle's top speed has increased an additional 30 km/h (18.6 mph). In this case, the 225/45R17 91W Standard Load size's rated load capacity of 1,477 lbs. is reduced to 1,255 lbs. when applied to a vehicle with a 270 km/h (168 mph) top speed.

For W-Speed Rated Tires
Vehicle
Top Speed Required Tire
Pressure Increase Tire Load Capacity
% of Branded Maximum W-Speed Rated Tire
35 psi O.E. Example
mph km/h psi bar % of value branded on sidewall psi lbs.
118 190 0 0 100% 35.0 1000
124 200 1.5 0.1 100% 36.5 1000
130 210 3.0 0.2 100% 38.0 1000
136 220 4.5 0.3 100% 39.5 1000
143 230 6.0 0.4 100% 41.0 1000
149 240 7.5 0.5 100% 42.5 1000
155 250 7.5 0.5 95% 42.5 950
161 260 7.5 0.5 90% 42.5 900
168 270 7.5 0.5 85% 42.5 850
Note: Never exceed the maximum cold inflation pressure branded on the tire's sidewall.
 

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2020 Dodge Challenger Hellraisin Scat Pack
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Well, that idiot sticker was put on the car by the manufacturer. I simply fail to understand why people who apparently hold an auto maker in such low esteem buy its products. I prefer to buy a product from a company that I believe knows what it is doing and this comes right down the proper tire inflation pressures.

My previous cars did not have a call out for a change in tire pressure vs. speed. The tire pressures were suitable even if the car was driven to maximum speed. Given these were Porsche cars and of course could have been used on the autobahn this inflation pressure was good all the way up to 155mph for one car and up to 189mph for the other car. There was recognition vehicle load could require more air pressure.

My new JCW does have a call out for a change in tire pressure -- an increase in tire pressure -- should the car be operated at high speeds (100mph+ I think).

I checked my digital Challenger owners manual and this is all it had on this subject:

Tire Pressures For High Speed Operation
The manufacturer advocates driving at safe speeds and within posted speed limits. Where speed limits or conditions are such that the vehicle can be driven at high speeds, maintaining correct tire inflation pressure is very important. Increased tire pressure and reduced vehicle loading may be required for high-speed vehicle operation. Refer to an authorized tire dealer or original equipment vehicle dealer for recommended safe operating speeds, loading and cold tire inflation pressures.



It wasn't clear from your post that you did the above but if you did and 45psi is the correct pressure for high speed operation then that's fine.
 

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Discussion Starter #7
Ugh
Sorry, this was not meant to be a personal attack though it seems as if you perceived I was trying to start an argument.

Unfortunately I will not get the information I was looking for from this thread as any normal person who reads the posts will move on and not post, as to avoid conflict, as will I.

Thank you
 
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