Cloud9...68

Thanks; I was wondering about the durability of the magnesium centers. I'll pay careful attention to this. I sure do like the looks of the E26 a lot more that the "basket weave" E50's - too busy for my taste.

Oddjob

Some example cracks.

The E50s are dated, but they are light. E26s do look better. 9s in front, 10s rear. 245s front, 275s rear.

Cloud9...68

Here you go - as you can see, my tires don't look stretched at all - the lip of the tire still sticks out noticeably from the edge of the rim:







This is a very controversial subject on which I'm sure many people have very strong opinions, based on their own experiences. But Grassroots Motorsports runs more tests of track-oriented tires than any publication I know of, and they have found on multiple occasions dramatic improvements when moving a tire from a rim, even one that isn't particularly small for the given tire, to a wider rim, often one outside the bounds of conventional wisdom. This doesn't mean that going from a narrower tire to a wider one on the same rim will make the car slower - it just indicates that it may not make it any faster.

Of course, there are a lot of factors at play. For example, a wider tire is typically taller, which reduces the numerical final drive ratio and lowers the revs for any given speed and could hurt acceleration coming out of corners, and it's also heavier. Depending on the car, any possible benefits from a wider tire may be outweighed by disadvantages such as these.

In my particular case, my car has solid and spherical bushings in place of the stock rubber bushings, along with a half cage, so my car has very little compliance. This may make it uncommonly sensitive to any "squish" left anywhere in the system, including the tire sidewalls. In any event, my best times have been on tires that are by conventional standards "stretched" on the rims, so I'm happy with this approach. The tires are a little cheaper, too.

Cloud9...68

Jim,

That is a beautiful car.

sm

Thanks Cloud! Do you have a link to the GMS article?

How does your car ride on the street, with all of the metal bushings?

Cloud9...68

I'm afraid I don't have a link, but the issue was December 2013. I'm going to email them and suggest they run a test where they take the same brand and model of tire, and test combinations of different rim widths and tire widths to quantifiably answer the question of what works best. My hunch is that for a given rim width, a wide range of tire widths will give lap times that are within the margin of error. The real benefit comes from taking a specific tire, and mounting it on a wider rim.

If I drove the car on poor quality streets, I'm sure it would beat me up pretty bad, but the streets here in Austin are quite smooth for the most part, so the ride quality really isn't too bad.

Humboldtgrin

What brand/model tire is that?

Cloud9...68

They're SUmitomo HTRZIII's. They have a listed section width of 9.4", measured (I assume, based on Tire Rack's table) when mounted on an 8" wide rim. I've also run BF Good F-Force Rivals, and I don't remember the wheels sticking out beyond the tires, but I never took a picture. That tire's section width is listed at 8.9", but Tire Rack list the tire measured when mounted on a 7.5" rim. My most recent tires were Nitto NT01's, and the rim stuck out beyond the visible tire edge on those, but I can't find a listing for that tire's section width.

Humboldtgrin

I thought they looked familiar. I have a couple sets of sumioto HTRIII's. 285/30 18's mounted on 10" wide rims and 295/30 18's mounted on 11" wide rims.

Cloud9...68

How do you like your HTRZIII's? I had a set several years ago, before doing all the modifications to my car, and I liked them. My reason for going back to them after running more aggressive tires was that after a 7-month layoff (long story), I thought it might be a good idea to ease back into things on a set of tires that would give me more warning before breaking loose. At first, they were very squishy, probably because they have such a deep tread (10/32"), but after a few sessions, I'm starting to like them. I can definitely run some serious slip angles without fear of ending up in the weeds. And you can't beat the price, and the fact that they should last longer than extreme performance summer rubber (BFG Rival, Bridgestone RE71R, Kumho V720, etc.) is a bonus. I'm wondering if maybe shaved HTRZIII's (Tire Rack charges about $30/tire for shaving) might not be a reasonable compromise of price, grip, and longevity.

Humboldtgrin

I wish I could tell you how I liked them. I got them for the same reasons, price/threadwear/ traction. My turbo engine bay is kinda bare with everything else rebuilt and ready to go, the 295's are on the rear of my turbo on 02 hollow spoke turbo twist rims. And I need to repair one front BBS classic sport 2 18x7.5 rim before I can mount that set of rims on my 89 944. I only have those mounted on the rear of both sets of rims, still brand new.

Oddjob

The E26's show up from Woodman yet?

Cloud9...68

No - I've sent them a couple of follow-up emails, but they haven't responded. But in fairness, I did tell them I'm not in any rush, because I just put new tires on my existing wheels. I plan to call them tomorrow.

Cloud9...68

I finally heard back from Bob Woodman tires - September is a very busy month for them, and since I just installed a new set of tires on my current rims, I'm not in a huge rush to buy a new set of wheels, anyway. But in case anyone is interested, we're having a little back-and-forth as to what width inner/outer barrel I would need to fit 10.5" wide wheels all around. The back is no problem - it looks like I could stuff at least 12" wide wheels with the proper offset back there. Up front, I have 2.25" id coilovers, and with my current 17 x 9" ET55 wheels, I have 19 mm of space between the inside of the wheel and the spring. These wheels have, by my calculation, a backspacing of 169.3 mm. The BBS E26 wheels they've assembled for me, with a 7.5" wide inner barrel, and a 3" wide lip, have a very similar backspacing of 168.4 mm. So, this gives me a solid 20 mm of clearance between the inside of the wheel and the spring, which tells me a wheel with an 8" wide inner barrel, and a 2.5" outer lip, would fit comfortably. A wheel of this size would protrude to the outside only one inch more than my current wheel, and it looks like I have plenty of room under my fender for that, probably without even rolling the fender lip. Am I missing something? Even if Bob Woodman Tires is correct and an 8" inner barrel doesn't provide enough clearance to the spring, I could always add a small spacer to "customize" the fit. Comments?

Oddjob

What is the center part number? They have many different center depth options, which is the offset between the rim flange and the hub face (shown as 1" in the drawing below as an example and labeled as "center backspace").