Difference R-comps make in an AX

[bsclywilly]

In case anyone was wondering how much faster they could be switching to R-tires, I had experimented a little at HADA ax #2. 6 Laps initially on the R's and then 2 laps on the streets. I figure the number of runs didn't affect the best times very much as I was more familiar with the course by the time I was on the streets. And i was generally pleased with my runs, I didn't give away too much with either tire.

The short story is that the streets were 3.9% slower.

Setup:
93 Civic Si @ 2250lbs wet
supercharged d16 dyno at 168whp/127lb-ft
12/10kg/mm springs w/ mysterious rear bar

Hoosier A6 225/45-13 (Bridgestone RE-01R 205/45-16)
Best time, clean run: 35.872s (37.280s)
Average time: 36.2s (37.5s)
Max lateral g: 1.46 (1.30)
Max speed: 86.1kph (82.9kph)
% WOT: 18.7 (23.1)

Both sets of tires were relatively fresh with 2 events on the hoosies and 90% tread on the BS.

[nrg3k]

daaaaamn - you still had FTD on streets!

DJM:>

[engsr]

^ Damn, you're right.

Interesting data, Will. I believe the Provincial series gives a 2% bonus with streets. I wonder if this type of data could be used to argue a bigger bonus percentage - ie. if you gather enough data with several cars in different classes, maybe even with different Rs (ubers and non ubers).

[bsclywilly]

Giving a bit less margin to street tires would ensure that competitors are still aiming for fastest times, rather than max points.

One other thing I noticed, and it had an effect, was the difference in wheel size. Even with the lower traction of the street tires, the fact that they were larger, meant that I could get to full throttle easier. I was flat out for a section of the slalom, not so with the hoosies.

[Zoli]

Dave and I have been discussing the pros/cons of going to 13" wheels from the 15's we currently run. My reasoning for wanting to go 13 is to aid in low-end pickup from the slightly lower circumference (dependent on width of rum and profile of rubber) to help the need to downshift coming out of some slower turns, as well as (hopefully) a bit of rotational weight loss.

Is my logic correct, and if so, would it be noticeable?

Will, what width rims are you running those 225's on? Do they have any effect on your shift points?

[BBQMAN]

^ Damn, you're right.

Interesting data, Will. I believe the Provincial series gives a 2% bonus with streets. I wonder if this type of data could be used to argue a bigger bonus percentage - ie. if you gather enough data with several cars in different classes, maybe even with different Rs (ubers and non ubers).

To do this right and have useful data, the tires would have to be of the same dimension and using the same wheels.
Then , to optimize the street tires, they need to be shaved.

The type of course comes into play also. Fast sweeping corners do not affect streets as much as low speed hard corners.

FYI- fastest STS Civics in SCCA regularly run better than my ITR can on Hoosiers........

[bsclywilly]

They're 7.5" width.

When i'm not traction limited, I would say the increased acceleration is definitely noticable in the ass. To back that up, looking at the data and comparing straight line accel at wot (at WOT, i'm power limited so any advantage the tire compound gives me is nil) the 13's are consistently 0.05-0.09g greater. This is alot considering my max accel at wot is only about 0.4g

As far as gearing, for the short courses i've run so far in Ontario (only 4 between hada and tlmc) i've never had to shift out of 2nd :) And you know how much time shifting can take out. the 2-1 shift is pretty bad since 1 is geared so low. 2-3, not so bad but it's still time lost. Not sure how much faster courses are set up at other venues (In Cali, I was regularly well into 3rd).

All in all, it'll be a small but noticable gain. I personally don't like it because the tire options are fewer (I count 2), brakes need to be smaller (if you do track), and it seems like everyone is jumping on the 13" bandwagon in Ontario.

Oh, total weight lost is about 50lbs compared to my streets (16lb tire, 9lb rim) if you go with a light weight tire like the A6. I used to run the Hankook z214-C70 but I don't think they sell it in Canada. The kooks were a bit heavier but one of their reps told me they were taking out a ply to get weight down to hoosiers...but their sidewalls were also alot softer, so *shrug*.

Oh and some reduction in CG too must help. But hey, I just like the way it looks slammed to the ground:cool:

[engsr]

brakes need to be smaller (if you do track)

You could upgrade the front brakes to Integra spec as those do fit under the Lensos.

To do this right and have useful data, the tires would have to be of the same dimension and using the same wheels.
Then , to optimize the street tires, they need to be shaved.

The type of course comes into play also. Fast sweeping corners do not affect streets as much as low speed hard corners.

FYI- fastest STS Civics in SCCA regularly run better than my ITR can on Hoosiers........

Yeah, I figured it would be pretty involved.

[bsclywilly]

To do this right and have useful data, the tires would have to be of the same dimension and using the same wheels.
Then , to optimize the street tires, they need to be shaved.

The type of course comes into play also. Fast sweeping corners do not affect streets as much as low speed hard corners.

FYI- fastest STS Civics in SCCA regularly run better than my ITR can on Hoosiers........

Oh I agree, it's just one data point with more than one variable changing. but still interesting nonetheless. Jut answering Zoli in my last post had me looking at the data in a way I hadn't before.

but FYI, the biggest difference i've found running here, compared to cali, other than the speed, is that the track temps are much much lower. On a comparable 26C day, in SD, I would get my tires up past 180-200F (sorry for mixing units) where as i've yet to break my hoosies past 140F and my street tires, past 130F. Shows how much the sun affects ya depending on your latitude. ..getting to the point though, street rubber doesn't drop off until 180F for an azenis and 180+ for the re-01. No need to shave then.

Really comparing apples to oranges here, your stock suspension itr is lugging around an extra 500 lbs compared to a prepped sts civic. 500 lbs!