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I use them as daily tires for drag and roll racing. I picked up the AR1 after hearing great things about them and after going through a pair of R888Rs. Going to stick with drag radials for now, so I’m selling them.
I use them as daily tires for drag and roll racing. I picked up the AR1 after hearing great things about them and after going through a pair of R888Rs. Going to stick with drag radials for now, so I’m selling them.
like the r888r they are noisy. i was able to get 1.65 60s with short burnout with them. impressive.
I did not do any speedo recalibration and I also don't know the exact offset. I dont remember finspeed telling me the offset. I checked my old invoice and that info was also left out.
I could check with V8ray to see if he knows the offset on his track wheels.
were you able to find out the offsets ?
Would be super helpful. there are quite a few people wanting 19s like myself but don’t want to order the wrong size.
i wonder how Finspeed knew what sizes would clear ….
I've got 19s all around for my track wheels 19x10.25F and 19x12.5R
no rubbing issues but I only run slicks
after doing more research i’m not sure i want 19s …. ughh.
For some reason Nankang doesn’t have a 325 30 20 in AR1. only their CRS 🤔. i’m concerned about going too small diameter. bigger gap bigger prob with speedo. both could be addressed i suppose. Rake is the most important for handling.
Factory sizes are
27.7 rear and 26.6 front. (1.1 in dif )
305/20 275/19
27.2 rear and. 26.6 front (4/10 dif)
325 /19 305/19
26.7 rear and 26.3 front. (3/10 dif).
Plus 305 front seems pretty big. may actually hurt handling ? maybe run 275 which is 26.6 and adjust height to keep Rake. also not sure the ECU would like tires too close in diameter.
Thoughts ?
Fyi i’m sticking with AR-1. best track/street tire by far.
I see your michelin slicks are 27.8 rear and 27.2 front keeping 6/10 inch dif.
If you are going from 325/30/20 to a 325/30/19, the speedometer error is not really that bad and at least in error in the right direction. You'll be going slower than you read and if on the street, a good thing.
... the speedometer error is not really that bad ...
A few thoughts:
- if you consider that a new vs worn tire can lose 5/32" of tread ... that's 10/32" diameter reduction or about 1/3" smaller diameter
- car speedo readings are _not_ accurate ... I've found that Mercedes/AMG speedos read about 3-5% fast with new tires (likely to limit liability and help allow for different tire diameters even amongst "same spec" tires)
- what's curiously interesting is that I've noticed from captured track-running telemetry that:
* the speed on the speedo reads faster than the wheel-speed captured via OBD and computed from 25Hz GPS (when they're sync'd)
* the wheel-speed captured via OBD generally is the same the 25Hz GPS speed
... which sort of says that there's a controller that's altering/scaling the speed specifically for the speedo display.
- if you consider that a new vs worn tire can lose 5/32" of tread ... that's 10/32" diameter reduction or about 1/3" smaller diameter
- car speedo readings are _not_ accurate ... I've found that Mercedes/AMG speedos read about 3-5% fast with new tires (likely to limit liability and help allow for different tire diameters even amongst "same spec" tires)
- what's curiously interesting is that I've noticed from captured track-running telemetry that:
* the speed on the speedo reads faster than the wheel-speed captured via OBD and computed from 25Hz GPS (when they're sync'd)
* the wheel-speed captured via OBD generally is the same the 25Hz GPS speed
... which sort of says that there's a controller that's altering/scaling the speed specifically for the speedo display.
I agree with you about speedometers being inaccurate (on the high side). It's been that way on every car I've owned for a couple decades now. I recall several years ago, a car mfgr, think it was VW, was sued BC their speedometers read too low (but I could not find the lawsuit with a quick search). A class action suit was brought because numerous owners received speeding tickets when they were sure their speedometers showed they were doing the limit. Since then I believe all mfgrs purposely calculate them low (reading high).
Our Jaguar reads high, my Bentley, Corvette, Jeep.... Everything I've owned in the last 15/20 years.
Speedometer calibrations occur in the EMS and are accessed through the tune. The speedometer is calibrated by manipulating the pulse rate from sensors given various tire sizes available for a given model. Here is an example of the data from a recent tune. The other thing I've seen when comparing outputs directly from the OBD port to dash gauges, the data from the port is realtime while gauges, sometimes are "dampered" so the readings do not "flutter". I call those "lazy gauges". A good example of one is the trans temp gauge. It will display a temp and hold it even though the actual temp is moving. This is really evident if/when changing the transaxle fluids, NOT to rely on the dash temp gauge to determine fluid level. I've found as much as a 10*F in actual fluid temps between the gauge and an actual OBD port readout.
My CLS 63 is dead on with my Vbox 20 HZ ……. put smaller diameter tires on my C7Z and speedo was off by a good 3-4 mph. frustrating on track since i was really used to seeing the speeds on my HUD and knew where target speeds were between turns. No HUD here so won’t water much. what about odometer ? mess up the mileage ?
Thanks for all the info on this thread!!!!! Just received my AR-1s. Can’t wait to try them out. I live about 15 miles from Barber Motorsports Park. I stuck with 19/20 setup. 275/35r19 fronts 305/30r20 rear.
Thanks for all the info on this thread!!!!! Just received my AR-1s. Can’t wait to try them out. I live about 15 miles from Barber Motorsports Park. I stuck with 19/20 setup. 275/35r19 fronts 305/30r20 rear.
I think not will be better with 325 /19s but the 305s work pretty well. Hope they make them in that size soon. they make their crs in factory rear size.
I did not do any speedo recalibration and I also don't know the exact offset. I dont remember finspeed telling me the offset. I checked my old invoice and that info was also left out.
I could check with V8ray to see if he knows the offset on his track wheels.
out of curiosity why did you go so wide upfront ? 305 is over and inch wider than factory. how’s the handling on track with that setup vs factory sizes ?
Lastly how do you like the Perelli slicks compared to say sport cup 2 ZP or R ? Do they get sticky pretty quickly or are the slippery first lap or two ?
out of curiosity why did you go so wide upfront ? 305 is over and inch wider than factory. how’s the handling on track with that setup vs factory sizes ?
Lastly how do you like the Perelli slicks compared to say sport cup 2 ZP or R ? Do they get sticky pretty quickly or are the slippery first lap or two ?
thanks.
My race shop accidentally ordered the wrong tire so it was a Ferrari challenge 305 instead of a 295 front. They had already mounted them on my track wheels and they fit my car so I tired them out and they worked great.
I cant say how any of the slicks compared to ZP or R because I had regular cup 2s and i cant say how they compare the that either because I never tracked with the stock tires. My first day with the car I put on hoosier r7s. To my understanding, at COTA, the hoosier is about 1.5 seconds faster than cup 2 and slicks are about 1.5-2.5 faster than hoosier.
IMHO
Michelin - fastest but have the quickest drop in performance and least longevity
Pirelli - slightly slower than michelin but last alot longer and do not fall off as quick as michelin. these are also the most expensive
Hankook - Cheapest $$ almost half the price of the other two. Slightly slower than pirelli but last the longest and they do not drop off the slowest. Arguably my favorite due to price and performance.
If money was no options i would be in between Pirelli my first choice and hankook second.
My race shop accidentally ordered the wrong tire so it was a Ferrari challenge 305 instead of a 295 front. They had already mounted them on my track wheels and they fit my car so I tired them out and they worked great.
I cant say how any of the slicks compared to ZP or R because I had regular cup 2s and i cant say how they compare the that either because I never tracked with the stock tires. My first day with the car I put on hoosier r7s. To my understanding, at COTA, the hoosier is about 1.5 seconds faster than cup 2 and slicks are about 1.5-2.5 faster than hoosier.
IMHO
Michelin - fastest but have the quickest drop in performance and least longevity
Pirelli - slightly slower than michelin but last alot longer and do not fall off as quick as michelin. these are also the most expensive
Hankook - Cheapest $$ almost half the price of the other two. Slightly slower than pirelli but last the longest and they do not drop off the slowest. Arguably my favorite due to price and performance.
If money was no options i would be in between Pirelli my first choice and hankook second.
Great info thanks.
One more question do you have cooling ducts like Tikt and any issues with clearances on new wheels/tires ?
One more question do you have cooling ducts like Tikt and any issues with clearances on new wheels/tires ?
I do have the front Tikt ducts only. I didn't think i really needed the rear since im close to or at traction control fully off at the track. It would not hurt to have them though.
I dont have any clearance issues with the tikt ducts with track wheels/slicks setup.
I do have the front Tikt ducts only. I didn't think i really needed the rear since im close to or at traction control fully off at the track. It would not hurt to have them though.
I dont have any clearance issues with the tikt ducts with track wheels/slicks setup.
Still waiting to hear about offsets fyi
Thanks that’s really good to know.
I got confirmation from Forgline as well that the VX1 19 inch rear clears. they have database showing at least six other tracked GTRs that got them. Those and Finspeed are both $7k.
Waiting to hear back about BC Forged ($4k) and Signature ($5k). designs are all very similar. Best looking ones are probably the Finspeed but not by a lot.
I've got 19s all around for my track wheels 19x10.25F and 19x12.5R
no rubbing issues but I only run slicks
heard back from Finspeed and they said that 10.25 and 12.25 were the widest that could fit. I had hoped for 10.5 front as that’s the minimum recommended for the 305 wide tire i believe. I ran 305 on 10 inch rim and it was def too narrow. Worked but later i ordered 11 inch which were perfect. Would you please send pic of the 305 tires lunges on rim so we can see how pinched it is ? I can see from above pic they do look a bit pinched. side angle would really be able to tell. I’m sure they are totally safe just not ideal for the feel.
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