FlewByU352

I'm so torn on wheel and tire choice. TRM makes the C3M in 15x9 +36 and 949 makes the 6UL in 15x9 +36 but without cutting rear fenders the 9" wide will not fit using a 225. I hate to stagger so I'm wondering how bad the 225 really is on a 8" wide for sidewall flex?

granracing

I think the 8" would be just fine.

Xian

It's fine. The 225 will even work ok on a 15x7 at the rear... wouldn't do it at the front though.

scottdh20

I too am looking at the bfg rival in a 225/45 on either a trm c1 15x8 +20 or konig wideopen 15x8 +20

but the fenders im going to be running are designed for a +0 but I cant find much but hella flush rims in the sub $125/ea range

I'd rather not run spacers

rice_classic

This might sound like a strange question but what is 205?

Do I know know what it is "supposed" to be? Yes I do. But does Hoosier, does Toyo? Sometimes it seems like they don't.

Example: a 225/50/15 or a 225/45/15 RA1 is the same damn width as a 205/50/15 Hoosier R6. I can put 225 RA1s, C51s on a 15x7 and have them fit my car all day long, lock to lock. I cannot fit a 225 Hoosier R6 under my car.

The section width difference between the 225/45 RA1 and R6 is .8" on the spec sheet (R6 being wider) but seems like even more IRL.

I finding the case about the 205/50/15 Toyo RR as well. Like the R6 it too is "oversized" in terms of width.

So basically I'm looking at real world width as opposed to just the number now. RR/R6 I run 205's on a 15x7. RA1s or C51's I use 225's.

Xian

Yep... sounds about right. FWIW, I've seen a handful of CRX's that have fit 225/45 15 Hoosiers onto the car but it's tight up front and crazy tight at the rear. The 225/50 14 is an easier fit as is the 205/50 15.

But, as to your question, I think your best bet is to go off of published specs of the tire vs. DOT tire sizing. As you pointed out, Hoosier tends to run the largest of the large but you see it with different manufactures at different times depending on the specific tire.

bakrdkng

i've ran 225/45 rs3's on 6.5'' wheels as well with no problems. you will need to find a tire mounter who knows what he is doing and they will fit just fine. you may also need to run a spacer in the rear to clear the trailing arm.

rice_classic

BACK FROM DEAD:


The last 2 race weekends I've been rudely awakened to the importance of tire temp vs tire width.

At two different tracks I have proved twice that my 205/50/15 RRs are faster than my 225/45/15 RRs by one half to a full second. Both the data and lap times boldly made that clear, oh yeah and losing 4 races in 2 weekends made that clear as well.

Both weekends had ambient temps at or below 70F.

The difference? About 30+ degrees tire temp. The 225s just shed so much more heat (or maybe generate less?). They may also have more rolling drag but the glaring difference came when I took tire temps and my 225s were 150F hot and my 205s would be 180F hot (and almost a second faster).

Another guy I race with (same make/model car) went wider as well from 205 R6's to the 225's Hoosier R6's. He didn't go slower than his previous lap times, but he didn't match his best times either. I don't have empirical data but I hypothesize new R6's work better (closer to peak lateral grip) at a lower temperature range than the Toyo RR which is why he went wider but faster and I went wider and went slower.

Regardless, the back to back testing of the 225 and 205 RR on my 2250lb ITA CRX was evident.

The weather is taking a turn for Summer now and maybe on a 80-90F day the track will be hot enough where the 225s will reach their optimal temp and actually be fast.

johnjw

was this ^ on the same width rim? curious if you went from a 205 on a 7 to a 225 on a 8?

Xian

Good info... and excellent points about different tires, different compounds, and different temp requirements. There are a ton of variables and it's tough to balance them all... I know ITA Miata's have pretty consistently done the same sort of times on 205's Hoosiers as they have on 225's. Rolling resistance and aero drag have appeared to be the biggest hurdles for that application. For the Honda stuff, the 225's are almost always faster BUT this is in the SE where it's blazing hot more often than not.

PS
ITA rules only allow a 7" wide wheel so I doubt he ran the 225's on an 8".

rice_classic

All of this.

ITA = 7" rim. The 225/45 RR isn't much wider than a 205/50 RR on the same rim. But heat difference was staggering.

The guys back east running massive 225 Hoosiers often are running A6s as well. So that solves the heat the problem when you're road racing on an autocross compound.

I suspect there's more to the story but I don't know the extent. I know the 205 is working "better" on the 7" rim and thus may be working with my limited camber better providing more tractive forces and producing more heat. Maybe... maybe not.

In a few weeks I'm going back to Pacific when the weather will be hotter and I have solved my camber woes and if I can get the 225's up to 180+F then we'll see if they're still the slower tire.

Xian

For IT, don't believe the hype on folks out here running A's vs. R's. There are absolutely SOME folks doing it but they're the outliers. Most people still run the R's as they last longer than A's and really only give up time for the first ~couple laps while they're coming up to temp.

I'm interested in seeing the results of the ongoing testing. Aren't the RR's somewhere between the A's and R's with regard to temp tolerance?

rice_classic

It's been my experience that the RR handles heat and abuse better than the R6. They don't fall off quite as easily and when they do they are easy to bring back. Right now I'm thinking that below 160F, the R6 provides more lateral grip than the RR.

VTECIntegra9

Anyone gotten a hold of A7's yet? I know someone testing them so curious if anyone else is on the Hoosier list?

Calif_Kid

These are a little off topic, but just wondering - for those people who have run Toyo RA1 or NT01's, and then run the RR's, what was the difference in hot pressures that you found the RR's needed vs the RA1/NT01s? I'm running a EK hatch in Nasa TTC/H2 at 2500 lbs with driver running 225/45-15's with camber approx 3.6-3.7F and 2.7R. In the past, I've targeted around 35-37 psig hot with the RA1/NT01's, but I haven't run the RR's yet, so just wondering what others have found. Also, did you have clearance problems when you switched from RA1s to RR's as I've heard that the RR's are slightly wider.

Also, one very good/fast driver mentioned to me, that he liked to measure the hot tire temps and pressures, and if the tire temps were too low, then he would lower the cold pressure (at approx 1 psig cold being equivalent to 10 deg F hot) as the lower pressure would let the tire sidewalls flex more generating more heat. I know that if the tire temps are too low, then it may mean that you just need to drive it harder, but assuming that the car is being driven pretty hard, it is interesting about adjusting the tire pressures slightly to help adjust the temp somewhat. Just wondering if anyone has heard of this method. Thanks!! - Jim

rice_classic

I went back to pacific raceways (with more heat and more camber) and have a bit of an update.

Saturday it was hotter (80F ambient) and I was able to get heat in the 225's. Previously at PR I was only able to do high 39's or 1:40's on the 225s and did a 1:39.2 on the 205s.

On Saturday I did a 38.9 with the 225's but then only mid to high 39's after that. On Sunday it was cooler and I ran the 205's and in the race I did a 38.8 and then ran consistent very low 39's all race long. These 205's are almost showing cords.. God how I love the toyo RR.

So now I know I can make the 225's work if the day is hot enough. However the 205's seem to be the way to go. My next set of tires will be a 205.

speedjunkie_g35

Def felt better having 205/50/15 ZI's on 15x8 vs 15x6.5 I had them on originally!!

I have been debating jumping to 16" wheels so I could run the ZII in a 225. Im just not sure if it is worth it from the 205/50/15 ZI's I have now. This is a street set-up because I run 205 R6's racing.

Xian

Why wouldn't you just switch out to the Rival or RS3 which come in a 225/45 15?

speedjunkie_g35

If i go any larger than the 205 Z1's, I am going to need spacers. I guess a 5-10mm would be safe (I do have arp extended studs) but I have always had a thing against spacers. I rather have a correct offset.

Xian

Gotcha. My question still stands though. Why would you go to the taller 16" option vs spacer or different wheels in 15"?

PS
Is the clearance a problem on the front or the back of the car?

johnjw

yeah 16's suck for tire selection.

speedjunkie_g35

My current street setup will knock wheel weights off the barrel of the wheel due to itr brakes so I had been thinking of stepping up to a 16. Plus the simple fact that I love my Z1 ' s. They handle wet conditions great. Being in FL where it rains everyday, I tend to get caught in a storm on occasion. I'm Prob going to give the rivals a try on my current 15 rim. I can always sell if I don't like.

Xian

I run 15x8's with ITR brakes and don't have any issues with it knocking off wheel weights.

I absolutely loved the Star Spec... the Z2 has higher limits but, IMO, it's not nearly as rewarding to drive. The horror stories about the Rival are largely overstated. I'm in FL as well and run them on the street without issue. Yeah, they're not perfect in deep, standing water but they're generally fine in the wet. The new RS3 is supposed to be light years better cold and wet. They may be a solid 15" option for you also.

miamirice

Back from the dead....AGAIN. I just ran a 4 sprint race day at Homestead. First time running Hoosiers. 205's on 8". The tires can be awesome but....when they are overdriven they go FAR away. I don't seem to have a good understanding of how to be patient and finesse this tire. I had little awareness of when I was pushing the tire too much until it was gone. I corded 1 tire on the inside shoulder after 4 races which tells me I am way out line of driving the tire correctly. I was a 1 man show so between fuel, food, bathroom....etc. I never got tire temp readings. I ran them at 37psi hot.

Reading rice classics temp concerns, I am on the other side where I notice in these Hot Florida sprints, 15-20 minutes you see guys in preservation mode. I was warned that most guys will push really hard expecting a yellow and if it doesn't come you will see the pace fall during recovery.

So......I too consistently found my tires were pissed off around the 20 minute mark and would need to ease off a bit and hope an in-class car wasn't threatening. So I am considering 225's thinking temp control.

Also, the guy that is winning everything in my class runs a 9" wheel with spacers in the front. 8" in the rear. Do you guys see this wheel set up much where rules allow?

rice_classic

UNO) Hoosier R6's build temp quicker/easier than RR's because they have a much thinner tread band. Part of the reason the RR's last so long: thicker tread band.

B) In my specific situation, along with my switch to RR's, this year I also changed my front springs from 600 to 450 after my first race (softer) and I hypothesize that the softer front end put less stress throughout the tire and possibly reduces the rate at which the tire builds heat. Just a thought. Next year I think I'm going back to the 600lb springs up front, especially since I have a splitter now.

Trois) I haven't seen the variation in wheel sizes but I would suggest the 225 on the 8" wheel without a doubt. I have seen a fellow racer run 10mm split on track-width by using 10mm spacers on the front wheels and none on the rear.