15x7 or 16x7.5 ??
 

Anyone have experience with the 16x7.5 vs the 15x7? I would like to get as much tire on the car as possible for STS but understand I'll give up a little weight in the process.

Any downsides to the 16x7.5's Kosei's that people have noticed? Any rubbing with a 215/45 Azenis?

Thanks,

Stuart

I think the 215/45/16 azenis are heavier than the 205/50/15 and are less than 1/4 inch wider. They are also a little taller, so gearing is effected. The other issue is wheel weight, I think the 15x7's wieght less for the money than the 16x7.5's

I had the Azenis rub on the rear when running spacers, but that was only when I had the car fully loaded and the tire tail on the back. Talk about squat...

Are you going to do the suspension or just run it stock?

I'm looking down the road at the 205/40 16 Azenis 615:grin: Gearing should be pretty good with that tire and the weight should be offset by the low profile.

As far as other suspension mods......I'm still staying mostly stock until I know what class I'm going to run next year. I ran STS locally a couple weeks ago on my stock wheels with new Falken 205/50-16 FK-451's and missed first place by .1 second out of 20 plus drivers so it makes me think I could have fun in STS with just a few suttle mods. :smile:

If I do suspension I'll keep it pretty simple, Springs, camber plates, sway bars........We'll see.....I just want to race!!!!

Stuart

are the FK-451's shaved? 'cause that is the hot ticket right now in ST*

STX was won on shaved Falken FK-451, and the 225/35/17 FK-451 would be great on a Mini since it won't mess up gearing too much.

Not shaved and squalling all the way around the course:eek2: They only had about 150 miles on them before the race so I wasn't expecting much. As far as shaving them goes.....I'm sure that would help quite a bit as the tread deisign on these tires is not real great for abuse. That being said, the tires took the abuse and looked pretty good after three 60 second runs on asphalt. Grip was okay but I expect it will get a little better as the tire breaks in....We'll see, so far I am happy with then and it was the only tire I could find that met all my criteria for a street freindly "ST" tire in 205/50-16. Plus, they're cheap! :thumbsup:

Rumor is that on the FK-451's there are multiple compounds, and that shaving the tire exposes the softer compound without subjecting the tire to the amount of heat cycles it would take to wear the tread down by driving on it.

Aparently the cars used in the Mazda RevItUp Finale were all on shaved Falken FK-451's.

I was contemplating running the 225/35/17 size, shaved, on my STS Integra, but fate had other plans as my Integra is now in the great junkyard in the sky and there is a Mini in my future.

I bought the FK-451's as a street tire so shaving them is not something I'm interested in doing. To be honest, shaving a street tire seems a little ridiculous. I mean really, why would anyone run a "street tire" class if they have to shave their tires to be competitive:confused: You might as well buy some "real" race tires and quit messing around with the folks that are just out trying to have a good time running their street cars.

Next thing you know people will start towing their "ST" cars to an autocross.....(Oh wait, that might already be happening):mad:

Okay, I'm getting worked up over something that is not really relevant to this forum or topic. Maybe I'll take my rant over to SCCAFORUMS.COM and release my anger over there.

Until then, I'll waffle back and forth over what class to run next year? Frustrating myself and everyone else in the process......

Stuart
HS or STS Cooper ??

I share your sentiment concerning shaving street tires. But just like any sport you have to pay to play and if you wanna win you gotta have the right equipment.

If you're having trouble deciding what class to run, maybe this will help:

I campaigned a STS prepared 94 Integra RS for the last 2 years. I never made it to anything higher than Division events because I never had the car set-up right. I spent tons of money on suspension bits, built an engine for the car, and tested a couple different setups but never found one that I was really happy with. I always said that if I could go back and do it over I would've keep the car stock 'cause there is less room for setup error, and now through a rather interesting twist of fate, I am able to do that.

If you're anything like me, you don't want to run in a class where the car and how it is set-up plays a large part in how well you will do. In stock class that element is minimized (get it Minimized :lol:) versus ST or SP.

The most fun I've had autocrossing was when I drove a DS ITR in a ProSolo and Nationals back in '03. I think a lot of the fun came from the fact that I knew we weren't going to win or lose because we did or didn't have X, Y, or Z parts.

All IMHO of course:smile:

I've read several posts on the SCCA Forums from Falken employees and techs that said the FK-451 shares NO similarities with the Azenis - not the same compound, nothing. The shaved 451's did well because they were being run on Subies, weren't they?

Azenis and MX's still rule the day, IMHO... I prefer the Azenis even here in Texas, and run a bit more pressure in them in the summer to compensate for higher ambient temps. Worked great all season long.

I believe the 215/45R16 Azenis are 1/2" wider than the 205/50R15... FWIW, I run 205/50R15's on Flik Blast-C rims and it's proven to be a rather sweet combination. But, another buddy of mine runs 215/45R16 on Rota Slipstreams on his Cooper S and likes them, too and has no rubbing with H&R springs (with a 40mm drop all around)...

IMHO, the Cooper benefits from the lower gearing of the 205/50R15's reduced diameter - it really squirts out of corners and gets into the powerband MUCH quicker than when I was running 205/50R16's. The other side benefits are the LIGHT weight of the 15's and the cheap price tag on the 205/50R15 Azenis! I'm looking forward to some new sizes in the new Azenis, though.

I have also talked with the Falken reps about the FK-451 and they told me the 451 is a good tire but by no means does it share the same carcus or compound as the Azenis. Not only is the treadwear rating different but the sizes it comes in are dramatically different then that of the 215 Azenis.

I think I agree with the 15" setup for STS. While it would be nice to have 7.5" of wheel underneath the Cooper the disadvantage of weight, gearing and price might very well add up to an inferior choice for STS.....Of course, I already found a set of cheap Koseis 16x7.5 locally.

Wether or not I'll run STS next year goes beyond wether or not I want to be competitive. I know I can be competitive in HS at National events....The question remains, will anyone else be there to run against me?

In STS......There always lots of competition:thumbsup:

Stuart

Results don't lie. Shaved to 2/32" the FK-451's are basically a 3-grooved slick. And what does the fact that they were on a Subie have to do with anything? The cars used in the Mazda RevItUp Finale were on shaved FK-451. I never said they shared anything with the Azenis, I just said they performed as well as (if not better than) the Azenis when shaved.

FYI a shaved 225/35/17 FK-451 will be a shorter tire than a 205/50/15.

You've never weighed the Azenis then. I certainly didn't run the Azenis because they were lighter than teh MX in the same size. Azenis are heavy.

I could be wrong but I think he was referring 15" wheels and tires in genreal as being lighter then the 16" option. I'm pretty sure everyone is aware that the Azenis is one of the heaviest tires on the market. Unfortuneately the same can be said for the 451's and the 205/50/16's I just installed weighed in close to 23lbs:eek2:

I do not doubt you will get good results from the 451's shaved to 2/32nd's. To be honest you should get pretty good performance out of any tire shaved down that far....My only problem with shaving street tires is that it complicates the class for which they were intended. Yeah, this is racing and there will always be someone willing to do it but it's frustrating to see a class that was originally intended to draw in new drivers to our sport turn into another class where people cannot compete without taking extreme measures.

Stuart

My dad remembers the advent of the Street Prepared classing structure.

Just like the SP classes, the ST classes are still in their 'infant' stages and have a lot of maturing to do. Rules will become more specific as competitors start exploiting the rules (or skirting the rules depending how you look at it).

FWIW, GRM tested the 15" holey (15x5.5) and a 16" (x7 I think) with the same tire type, back to back. The 16's were 0.3 seconds faster on their test course. The tires on the 16's were wider but than the wider wheels allow that. Essentially, there may not be any performance gain to be had by going small.

Yes, the Azenis are heavy... the wheels are not! :)

Part of the problem with the MX's is that their sizes suck in anything smaller than 17's... I also personally don't think they perform as well on the surface we hold our autocrosses on - very rough asphalt.

I think it all depends on the width of the rim and the cross section of the tire... I wouldn't doubt that the 5.5" rim width had a tiny tire on it, which contributed to poorer performance. Also, less rim width can mean the tire runs more on the center if the pressures aren't right...

IMHO, it's not a very valid test - I remember thinking that when I was reading that GRM article. Now, had they tested similar setups in 15" and 16" I'd say it was more valid...

I remember a GRM where they tested all the various wheel and tire packages on a newer Honda Civic. This was a street test so they did not use race tires but their test showed that the 17" wheel and tire had produced the best lap times.

There is an argument to be made that when you increase the diameter of your tire you increase the contact patch for your vehicle. This is what Porsche used to do back in the 70's while running the lemans series. They were limited to width on their tires so by increasing the height of their tire they were able to increase their contact patch on the road. It would also explain why Drag cars use very large tires in the back to increase traction........

Something to think about.

It's no argument, it's pure fact. Increasing tire width makes the traction patch wider and increasing tire height makes the traction patch longer.

Part of what makes the Azenis so attractive to most and leads most to believe that they perform better than the MX is their ubAr stiff sidewall. The MX's are actually faster on rough surfaces where more friction is generated and thus more heat.

225/50/15 Azenis RT 615s on 15 x 7.5" wheels. Nobody makes any reasonbly cheap, reasonbly light wheels in that size but I'm working on something for the Civic/miata/MR2/MINI guys. :wink:

Actually, on our roughly surfaced autocross lot, the Azenis seem to perform a lot better... shrug.

Are those that are runnig the MX running them shaved? Because if they aren't that is why the azenis are faster.

Ah, nope... could be why... The battle for street tire class supremacy will continue, I reckon. I still prefer the Azenis, and am looking forward to the next generation Azenis. They'll be out when I need my next set, next year!

My thoughts.

The 205/50/15 Azenis will give up very little on a 7" wheel vs a 7.5" because of it's stiff sidewalls but this would not apply to a soft side wall tire.

215/45/16 Azenis is at most 1/4" wider than the 205/50/15 and weighs less than 1lb. more. I have both mounted on 7.5" SSR's. I run the 15's because of the reduced wheel weight and the location of that weight as well as the .4" less diameter of the 15's and the lower costs of the 15" Azenis. It was a total no brainer for me and 15" tire choices, in the past, have been more plentiful than 16's in the sizes and kinds of tires we need to run, though this seems to be changing. We seem to be stuck with the 205/50/15 in anything but a R tire but there soon will be some good 16" tires out in MINI sizes and the most important thing will be to have the best tire but you will also need the wheel to control that tire. That's why I got a set of 16x8's ce28n's for my STX MCS.

Contact patch is the same if the cars weigh the same and the tires have the same amount of air in them, it's the shape of the patch that changes with diameter. Taller is longer, shorter is wider. Generally longer is better for acceleration and braking, more grip in that direction and less subject to less than perfect alignments. (camber) Wider is better for turns if the alignment is anything close to right but with the 2 sizes of Azenis mentioned I don't think patch shape is an issue.
I will soon be testing the Falken FK-451 shaved, 215/40/16 and other tires as well. See my STX T&T thread. :smile: :smile: :smile: