Tire recommendation for HPDE

[shogun32]

My street tires will need to be the same 275/35/19 ratio, on the 9 inch rims, for the speedometer.

ForScan is easy or just live with the couple percent (if that) difference. I don't get this myopia over speedo accuracy. Mine is off by 9.8% and I can't be arsed to care or dig up Forscan to fix it.

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[Norm Peterson]

ForScan is easy or just live with the couple percent (if that) difference. I don't get this myopia over speedo accuracy. Mine is off by 9.8% and I can't be arsed to care or dig up Forscan to fix it.

This ^^^

Especially when the OE calibration could be off by a percent or two without you knowing.


Norm

 

[hlh1]

Good points guys. It's probably not worth messing with. I guess if I'm going from a 40 to 35 ratio tire my speedometer will be reading slightly fast which is better than the opposite. It will be reading 65 mph when I'm really doing about 60 mph. And I can look at the GPS for the real, accurate, speed.

 

[DickR]

FYI I've driven 10's of thousands of miles and at least 500 autocross runs using 275/35x19 RE-71R's Front and Rear on my previous 15 GT PP and now my current 18 GT PP1 stock size 9" Forgestar front wheels. Currently I have a new set of Falken RT-660's on the 9" F and 9.5" R Forgestars. NOTE the front wheels have about 6 mm MORE clearance due to the offset change from stock. I haven't autocrossed them yet but they "look" happy and are only slightly wider than the RE-71R's so I'm optimistic they will autocross OK.

The 6 mm offset change results in MORE sidewall to MagneRide strut clearance than with the stock wheels and the OEM PS4S 255/40x19's on the OEM wheels.

FYI stock offsets are 45 mm F and 52.5 mm R. My Forgestars, ordered through Sam Strano, are 39 mm F and 48 mm R.

Regarding speedometer error with both my cars the speedometer error with 275/35's vs 275/40's was/is about 4 mph at 70 mph. That is the indicated speed is about 4 mph higher than the actual speed. Use GPS (Garmin, phone app, etc.) to determine your situation.

FYI TireRack.com includes the "revs per mile" spec for most of the tires they sell. This is a great way to calculate the percentage difference between tire sizes and to some degree the same size with different brands. With that info you can get a ballpark speedometer reading percentage difference without using gps.

 

[bnightstar]

ForScan is easy or just live with the couple percent (if that) difference. I don't get this myopia over speedo accuracy. Mine is off by 9.8% and I can't be arsed to care or dig up Forscan to fix it.

You rack up miles faster going to shorter wheel though which mean higher depreciation per mile ... As you are passing less real miles than actual. This could and will lead to problems with OLM and service intervals etc. Overall not correcting your speedo is costing you big money.

 

[hlh1]

Good point. I just need to go with 35% tire ratio for track and street, make the Forscan speedometer change, and be done with it. Not a big deal.

 

[Norm Peterson]

You rack up miles faster going to shorter wheel though which mean higher depreciation per mile ... As you are passing less real miles than actual. This could and will lead to problems with OLM and service intervals etc. Overall not correcting your speedo is costing you big money.

Have to disagree a bit - 10% "too frequent" oil change and service intervals is not "big money". Heck, if your car ever sees track time, drag racing, or autocross, Ford's normal maintenance schedule is out the window anyway. Those activities could even be outside Ford's definition of 'severe service'.

I'd be willing to bet that a great many people are apt to go 10% too long between services, which if anything might be worse than going for service 10% too frequently.

The effect of depreciation itself depreciates the longer you keep a car. At some point it essentially becomes an irrelevant factor. First year, it's huge. By the tenth year the total - amortized over the entire ten years - not so much on an annual basis. Depreciation is actually a discouragement to aftermarket modification, so there's that as well.


FWIW, my "track set" of tires is about 5% shorter than the 27-ish OE spec, and my "street set" is ~3% shorter than OE. Even if I could pick one of those to try to set dead nuts on to statute miles or mph, I wouldn't bother (and I'll keep the couple of mph extra cushion between my car's speedometer reading and my car's actual speed in my pocket).


Norm

 

[shogun32]

I'd be willing to bet that a great many people are apt to go 10% too long between services, which if anything might be worse than going for service 10% too often.

given how going for Ford service is a 50/50 chance of getting a functional car back, the fewer visits it makes to the dealership the better.

ok, maybe not...

 

[Radiation Joe]

given how going for Ford service is a 50/50 chance of getting a functional car back, the fewer visits it makes to the dealership the better.

ok, maybe not...

Or maybe so ...
My dealer can't even find a bad wheel bearing in my wife's Explorer. Missed an airbag light during an annual inspection and wasn't even kind enough to convince me not to trade in my awesome diesel F250 with 4 link suspension on a ... wait for this ... a Ford Focus. Well, maybe they're the smart ones.

 

[sdskinner73]

no experience but the 555g2 seems like the most hated summer tire ever lol. i looked into them because lmr has that package with the sve wheels so it would have been convenient (im sure a lot of people have them for this reason). the reviews on youtube from all the various rwd muscle cars is nothing but hate aside from nitto dealers. there are videos of people returning the tires ect lol.

this topic comes up on fb groups all the time and for some reason people are so eager to defend their purchase that they defend the tires and say they arent made for racing, stop saying they are something they arent, use them like they are deigned ect. lol hello, they are a 300 treadwear max performance summer only tire and people are acting like they bought an all season.

I have them currently. Only had them for the summer, and they’re not great. Don’t grip that well. If it’s not 100% dry on the road, they’re terrible. Just my opinion on a few months of use.

 

[bnightstar]

ForScan is easy or just live with the couple percent (if that) difference. I don't get this myopia over speedo accuracy. Mine is off by 9.8% and I can't be arsed to care or dig up Forscan to fix it.

it's not free anymore found out the hard way bought lifetime licence.

 

[tosha]

Very helpful thread and tons of useful information. 285/35/19 rotatable setup seems to be the sweet spot for weekend track warrior.

I have a question that wasn't covered yet though - I have PP1 GT with MagneRide and planning to install supercharger (roush phase 2), and not sure what setup would work best for occasional hpde/track day scenario:
1) stick to square 285/35/19 with et40 apex rims all around
2) go with 305/30/19 with et52 apex rims, add spacers and extended studs
3) do staggered setup 275/305 or 285/315

Option 1 is the easiest, but I'm concerned whether there is enough rubber on the back for FI. Could be used as daily as well. Downside - Hankook RS4 not available in this size (was a main candidate for track use)

Option 2 seems to be the best for track, but requires spacers and studs. Not good for daily drive. Tires selection seems to be the best.

Option 3 - obviously no rotation. How about understeer considering FI?

These would likely be dedicated track wheels as I intend to keep stock pp1 wheels as well, unless option 3 is actually the best for both and then I don't need 2 sets. Appreciate any feedback and advise.

 

[shogun32]

Option 1 is the easiest, but I'm concerned whether there is enough rubber on the back for FI

there is no such thing as 'enough' rubber for FI short of tall-sidewall drag radials and even then. If you like to do track work FI will IMO ruin the car.

 

[EFI]

Could be used as daily as well. Downside - Hankook RS4 not available in this size (was a main candidate for track use)

Federal 595RS-PROs are a very close candidate to the RS4s, wear like iron on track and can be used on street. They come in 275/35/19 and fit nicely on a 10" wheel as they run wide. At less than $200 a pop it's a pretty good bang for buck and perform well on track. Might be a good idea to start there before going nuts on tires and mods to make them fit.

 

[tosha]

Federal 595RS-PROs are a very close candidate to the RS4s, wear like iron on track and can be used on street. They come in 275/35/19 and fit nicely on a 10" wheel as they run wide. At less than $200 a pop it's a pretty good bang for buck and perform well on track. Might be a good idea to start there before going nuts on tires and mods to make them fit.

Thanks. Hankook comes in 275/35/19 as well, same as RT660, but I feel that it would be too close to what I already have and no point to buy another set of wheels. RS4 does come in 305/30/19 size, which is good for my 2nd option.

I'd prefer to avoid spending on set of wheels just to go and buy another set next year and do the mods anyways, if 305's end up as best option for FI.

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