GrandMasterKhan

I have a GPS unit which i have been using to verify my Speedometer for accuracy. I thought it might not be a bad idea since this recent lawsuit with honda's inaccurate odometer.

Anyways. heres the background info...

I actually upgraded my ap2 tires to RE50pp which are 225/255 and I found that my speedo was 100% accurate even up to 130+ mph. Recently I ended up with 2 flats @ the Dragon and no honda dealer withen 200miles had oem tires in stock. So I was forced to get the next best thing. $80 Riken Raptors in 245/40/17. I found that these tires actually cause my Speedo to be about 2-3 mph too fast.

I didnt really like the 225/255 combo so i thought about going back to oem tires. But i didnt want my speedo to be off again so i pulled up tire rack and found out some interesting info. fyi The 225/255 combo seemed 'loose' and squirmy. So i opted to have new OEM ap2 tires installed in the front but i am hesitant on which rears to get installed. Should i get a new set of 255s or stick with the oem 245s? I still have 1 good 255 rear with about 2000 miles on them :/



tire...........tire size.....diameter....revs per mile
OEM tire....245/40/17....24.6".............847............(rear)
Riken........245/40/17....24.7"...............?..............(speedo reads high by 2-3 mph)
ap1 s02.....225/50/16....24.8"..............840
RE50pp.....255/40/17.....25"................833............(proven to be accurate to 130+ mph)

So from looking at this chart it would seem that the 245 tire for the ap2 would be off quite a bit from actual indicated speed with the 255/40/17 and the ap1 rear tires being more accurate.




Interestingly enough the front tire on the ap1 is the same diameter as the 255/40/17 (also note that ap1 rear is the same size as ap2 front)


ap1 so2.....205/55/16....25"................833
RE50pp.....255/40/17.....25"...............833
OEM tire....215/45/17....24.8".............840.............(ap2 front)
ap1 s02.....225/50/16....24.8"..............840............(ap1 rear)

G2k

nice info!

my2ks2k

that is good info...it would be nice if company x's 255/40/17 was the same size as company y's, but apparently taking actual dimensions of tires is too hard for the makers.
when you say your 225/255 combo felt loose and squirmy...that seems odd, considering the REO50A PP is supposed to be 2 steps up from the OEM tire. i put them on mine and now it feels incredible...i'm assuming you tried adjusting the pressure? also there's always going to be the difference of going from tires with little or no tread to 9 or 11/32 of tread, which could make things feel squirmy to begin with...

GrandMasterKhan

The issues I brought up here are actually all OEM bridgestone tires compared as on the S2000. With the exception of the Riken Raptor.

My experiance with the 225/255 combo is that the tires did not make a full contact patch front or rear. about .75"-1" of the outside edge of the tire never touches the ground (assuming OEM alignment & tire pressure) And i didnt like the square look of the front tires anyways. The steering now with the oem front tires is more responsive and the car feels more balanced now.

I am still running the riken raptors in the rear as I am waiting for the honda dealer to get the OEM rears in stock.

But honestly I liked the width of the 255 rear tire. Jim recommended against the 215/255 combo since the rolling diamater would be different. BUT if you look at the above chart the OEM setup is not identical anyways. In fact it looks like the rear wheel is actually a smaller diameter than the front.

So why would be be against that if the Stock setup is the same way? (the 255 would make the rears larger than the front by .2)

my2ks2k

i think probably he reccommends the 225/255 because
1. it keeps the stagger (front to rear) closer to factory than a 215/255 setup
2. the REO50A PPs are supposed to be 2 steps higher (in quality) than the OEM REO50s
3. the slight difference you note in overall diameter is minimal

also note that you're comparing the rear 255 to a front 215 overall diameter, which is not what he reccommended. what you need to measure is the 225/45/17 REO50A PP diameter for a true comparison

ie: OEM is front diameter 24.8, rear diameter 24.6

the REO50A PP is front diameter x, rear diameter 25

my guess is the REO50A PP 225/45/17 diameter is 25.2

GrandMasterKhan

the rear diameter of the ap1 is 24.8, rear diameter of the ap2 is 24.6. So the AP2 OEM tire is Smaller than the oem ap2 tire. And I noticed a slower speedo as a result vs the 25" 255 re50app

the re50app-- 225/45/17 is 25" which is identical to the re50app in 255/40/17


the OEM ap2 setup has a 2.3" stagger. the 225/255 setup gives only 1" stagger (as based on Tread contact width from tire rack specs)

In the front the 215 oem contact patch is 6.7" vs 8.5" of the 225 PP tires.

The tires are also visually taller and body roll was more pronouced. I didnt like the 225/255 setup at all. I had an alignement done and then went to the dragon with about 1500 miles on the tires and they felt downright scary. Even with 4000 miles on the tires they still did not have nearly the same feel of grip as the oem tires.

I could tell an IMMEDIATE difference now that i have the oem 215s up front again (instead of the 225s)

my2ks2k

oh well, to each his own. i love mine

GrandMasterKhan

I see you have an 00. Are you running OEM ap2 wheels with your 225/255 combo?

cyman83

hey just so you know, rpm stands for revs per minute not mile

my2ks2k

yeah i have ap2v2 wheels. just about the best looking wheels around imo.