Tire Questions: Need Help

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

shojuan

New Member
Joined
Aug 14, 2002
Messages
7,222
Reaction score
1
Location
sunny San Juan Bautista,
Yamaha V6 said:
I have VERY successfully used 235/45-17 tires on a 7" wheel (it was much better on a 7.5" wheel though). Now, you have a smaller profile, so the sidewall will have to come in on a steeper angle for the 7" wheel.

FWIW, I have also heard of 245/45-17's on a 7" wheel, but that's a little hairy in my book. I would not go to a 40-series tire on the SHO unless you're in 18's, personally.
On the other end of the spectrum, I used to run 205/50-16 tires on 16 X 7.5" rims on my old 90 and 91 Camry's (stock size was 185/70-14 on a 5 or 5.5" rim). I really felt the performance AND looks of that tire size on a 7.5" rim was perfect. To translate sizes in a simplified manner that would mean a 225 tire on an 8" rim would be even less aggresive (217, if they made them, on an 8" rim would be the same). A 215/50 on an 8 inch rim would be within a hair of the look and fit of that ideal 205/50-16 on 7.5" rim.

Seems like a lot of SHO owners are comfy putting relatively wide tires on narrow rims. Just because a 7" rim is wider than stock doesn't mean it's a very wide rim even for a stock sized tire.

Just putting out my $.02 for whoever might have themselves an opportunity to run a wider rim than the upgrade status quo on a narrower tire than the upgrade status quo. Shoot, when I bought those old rims (MSW type 55) and tires from tirerack in 1994 it was the tirerack rep who recommended that size tire and wheel as an excellent "plus 2" upgrade from my stockers. Tirerack tends to be fairly conservative in what they recommend, IMHO. They don't recommend stuff that is pushing what is safe or what will perform less than ideally. I had my worries that 7.5 was too wide for those tires but took a chance, paid my money, and was blissful ever after until the end of days for those cars. Those tires on those wheels saved my life twice and the lives of my wife and my dog once.
 

shojuan

New Member
Joined
Aug 14, 2002
Messages
7,222
Reaction score
1
Location
sunny San Juan Bautista,
SHOkid13 said:
Just a comment/question: Why is a narrow tire/wide wheel better than the inverse?

Does it have to do with tire roll and wandering?
More square inches of rim to support the pneumatic pressure. Action and reaction you have more pounds of force pressing down on the tire to keep it flat. A cheesy way to think of it is imagine the rim width as an imaginary contact patch planted on the ground instead of the rubber patch.

With a narrow rim more of the reactive force components from the rim will be vectored out towards the corners, forces that deform the sidewalls rather than planting themselves straight down where you want them to keep the contact patch flat and planted firmly. Yup, less downforce in that all important patch.

Also a wider rim with a bit of rim bulge-out can take better advantage of negative camber. That's just simple geometry. In a corner with negative camber the tire sidewall on the important side gets forced towards a more straight alignment with the rim. The tire gets forced into more grip before it gets forced into less grip. With a narrower rim with tire bulge the tire sidewall starts off getting forced into less grip. It never passes go and collects $200. It starts heading straight to jail.
 

SHOkid13

Take it to the track
Joined
Nov 25, 2003
Messages
564
Reaction score
0
Location
Temecula, CA
shojuan said:
It never passes go and collects $200. It starts heading straight to jail.

Got it. Makes sense... I think. Basically if the tire is bulging around the rim, it can contort itself in hard cornering and actully loose traction. And when compared to the same rim with a narrower tire (no bulge) the narrower tire would essentially have more grip due to less chance of the tire flexing out of it's shape and loosing grip with the road on the business end of the tire.

Right?

I definately see the advantage of a wider rim, it's just having the money to afford one. Anyone have any (or know where I can get any) 17"x8" rims that look good, for a cheep price? I'd like to go wider on the tire, but I would need to have an affordable rim. Oh, also, weight is important. :biggrin:
 

shojuan

New Member
Joined
Aug 14, 2002
Messages
7,222
Reaction score
1
Location
sunny San Juan Bautista,
Yup. The sad thing is it gets pretty hard to fit 8" rims to a SHO.

FWIW, I will probably find myself running a 215/50-17 tire on a 7.5" rim. My answer to traction problems is a Quaife.

Probably will get 95% of the benefits of a 235 tire 95% of the time and enjoy half the disadvantages most of the time to boot.

I'm expecting a SHO that will feel more fleet on its feet in general.
 

SHOkid13

Take it to the track
Joined
Nov 25, 2003
Messages
564
Reaction score
0
Location
Temecula, CA
shojuan said:
Yup. The sad thing is it gets pretty hard to fit 8" rims to a SHO.

FWIW, I will probably find myself running a 215/50-17 tire on a 7.5" rim. My answer to traction problems is a Quaife.

Probably will get 95% of the benefits of a 235 tire 95% of the time and enjoy half the disadvantages most of the time to boot.

I'm expecting a SHO that will feel more fleet on its feet in general.

You're saying that the 215/50-17 will give you the 95%s or the Quaife? I have a Quaife, which I agree made a huge difference. I love it. But, I'm more concerned with traction on sweeping turns at high speed. I have the suspension and Quaife, just need the rubber. ;)

FTR (for the record?) - I haven't spun out, or lost traction yet. And, I don't plan on that happening. I just felt like I could use more traction. Like horsepower. It's addictive...
 

Yamaha V6

SHO Enthusiast
Joined
Aug 12, 2002
Messages
3,125
Reaction score
10
Location
Rhode Island
There is a balance to be achieved between tire flex / roll over / sidewall stability & actual CONTACT PATCH.

It's the contact patch that helps stop you, helps plant you, and helps launch you (along with suspension, tire compound, etc. etc.).

Guys, for a street car, the 235/45-17 rubber is REALLY nice, fits well on a 7 or 7.5" wheel (which are much easier to find than an 8" with good looks, light weight, correct fitment and price to match).

I have 17x8 wheels which fit on my SHOs, running 245/45-17 track tires. The tire & wheel combo runs 51-52 LB... The 235/45-17 Toyo T1-S tires & Team Dynamics 17x7 wheels I just sold Kenny are 41 lb. Static weight - that's FORTY POUNDS of rotational mass saved over the wider wheels & tires.

I will be the first to admit, the car handles much better with the 17x8's and the wider race rubber. BUT, I'll also tell you that's on the racetrack. On the street, you rarely push the car to the braking & cornering limits like you do on the track - you consciously limit yourself vs knowing you have a rescue crew standing by, there's plenty of open runoff, etc. on the track. With a good, grippy compound (and I'm not talking about ANYTHING all-season, including "performance" all-seasons), a 235/45-17 on a 7.5" wheel is going to be a VERY nice handling wheel & tire combo. If you can get the rotational weight down, your acceleration won't be hurt, and it's a win-win-win-lose situation (17's usually cost more money for wheels and tires, thus the "lose"). On the Gen 2, I didn't have to trim or roll anything, I got better handling, better grip, without losing anything on acceleration or braking.

Assuming you're looking to keep with/near the SHO's stock rolling diameter of 26.15"...

Toyo Proxes T1-S (This is a lighter tire than many):
225/55-16: 24.0 lb, ø25.7", 6.0 - 8.0" wheel
235/40-17: 21.4 lb, ø24.4", 8.0 - 9.5" wheel
235/45-17: 23.8 lb, ø25.4", 7.5 - 9.0" wheel
245/45-17: 24.9 lb, ø25.7", 7.5 - 9.0" wheel

Kumho ECSTA KH11 "performance" tire, 215/60-16 = 26lb, for reference.

As you can see, the lower the profile, the wider the wheel they recommend. Same width on the 235's, but because the profile is smaller they're going with a wider tire (partially due to installation concerns, I'm sure, but you get the idea).

Looking at wheel weights ('95 Volvo 850, for example, since they display 8" wheels more frequently):

16x7.5 MM11-3: 22.1lb (w/ 225/55-16, combo = ~ 46-47lb w/ stems, weights, etc)

17x7.5 BBS RGR ($570 each!!!): 17.6 lb (w/ 235/45-17, combo = ~ 42 lb)

17x8 MM EV-S: 28.5 lb (w/ 245/45-17, combo = ~ 54 lb)

The TD wheels I just sold Kenny were 15.75 lb each upon receipt (digital bathroom scale, they advertise something like 18lb) in a 7" wheel. I put the 24lb tires on the 16lb wheels, came out with a balance weight of 41lb, with a 235 tire, 45-series profile, 7" wheel (1" wider than stock, using 20mm / .5" wider tire than stock). So I reduced weight by 3lb per corner (like losing 84 lb dead weight off the car), increased the contact patch by about 1/2" in width, lowered the profile from a 60-series to a 45-series and a 1" wider wheel for cornering stability, and went with a better, grippier compound for traction too.

It's not about getting the best of any one thing, it's about finding a great balance for your application. My personal preference is the 235/45-17 on a 7.5" wheel. I didn't see a huge loss or compromise in performance moving to a 7" wheel in my case.

As always, Your Mileage May Vary. :biggrin:
 

SHOkid13

Take it to the track
Joined
Nov 25, 2003
Messages
564
Reaction score
0
Location
Temecula, CA
Yamaha V6 said:
As always, Your Mileage May Vary. :biggrin:

Thanks for all of the detailed information. Very helpful! :hail:

Would you consider the KDW2 tire to have a, "good, grippy compound"? I'd like something with some good grippy feel, but that will also last at least !5K-20K miles. My ES100s are about shot at 15K miles, and they only saw one track day. Treadwear rating was 280 vs the KDW2's 300.
 

Yamaha V6

SHO Enthusiast
Joined
Aug 12, 2002
Messages
3,125
Reaction score
10
Location
Rhode Island
As I understand it, treadwear ratings are not really universal, more like a comparison between a manufacturer's own brands (like, a 300 from Goodyear will not last the same as a 300 from BFG, etc.).

The Toyos I just sold were also 280 treadwear, and were pretty grippy in wet or dry - I liked them a lot. If you're pushing limits, plan on replacing tires more often and go with a better tire is a good ground rule.

I have used BFG KDW tires for a few years before going to the Toyos. I liked the big, beefy blocks, they were ok for wet weather too, and the 300 treadwear is a good treadwear rating for a "performance" tire, for longer life. However, I had SERIOUS issues with the KDW: Tread separation, blowouts, and cord sticking through the sidewall at the tread / sidewall interface. Each of these things were discovered after I'd been on the track, so it might be due to extreme working / heat cycling of the tires, etc.. This happened on multiple SHOs (95 & 91), 3 different corners (driver's front, pass. front, driver's rear), 2 different tire & wheel sizes (225/55-16 & 235/45-17; 16x7 wheels, 17x7.5 wheels). I'd inflated the tires to max pressure for the track, was told afterwards that they liked to be over-inflated by up to 10psi by Larry Maletta at FPS in GA from their using that tire.
I bought all new KDW tires (warranty partially paid for them), use them on the street only with no ill effects so far. Might be they changed the design or compound, might be track-related, dunno. Maybe for the KDW-2 it has been addressed, but again, not sure.

I may buy new Toyo T1-S tires for my 911 when the time comes, may use Nitto 555's, may go Yokohama AVS-Sports, etc; these are all higher-performance / lower treadwear tires than the BFGs. The track SHO is going to use race rubber & whatever tires will get me to the track. My own daily SHO will use the BFG's until I sell the car or sell the wheel & tire combo, etc.; after that, whatever tire I use on that will have a MAX of 300 treadwear. Kumho MX tires are used often on the SHO lately, are cheaper by far than the BFGs. Might want to look at those, but the Kumhos are soft, typically.

Good luck.
 

shojuan

New Member
Joined
Aug 14, 2002
Messages
7,222
Reaction score
1
Location
sunny San Juan Bautista,
Yamaha V6 said:
As I understand it, treadwear ratings are not really universal, more like a comparison between a manufacturer's own brands (like, a 300 from Goodyear will not last the same as a 300 from BFG, etc.).
That's correct. The treadware ratings are manufacturer specific. The numbers might not even be linear but rather arbitrary. The way these numbers are presented is very suggestive that there is some standard. But there is no standard. It's just a case of consumers being presented often misleading numbers.
 

SHOkid13

Take it to the track
Joined
Nov 25, 2003
Messages
564
Reaction score
0
Location
Temecula, CA
This is an interesting topic....


Quoted from edmonds.com:

http://www.edmunds.com/ownership/techcenter/articles/43859/article.html

"Finally, you might find the word TREADWEAR on the sidewall followed by a number like 120 or 180. This is a rating of the tread's durability, as tested against an industry standard. The reference number is 100 so a tire with a treadwear rating of 180 has an 80 percent longer predicted tread life while a rating of 80 means a predicted tread life only 80 percent as long as the industry standard."

However, quoted from Consumers Union:

http://www.consumersunion.org/products/nhtsadc101.htm

"CU continues to view UTQG Treadwear designation with skepticism. A tire's assigned grade is more a marketing device than a true measure of treadwear. It requires calculation which provides only a comparison among tires, with no realistic measure of expected mileage. UTQG Treadwear grades should be eliminated in lieu of a sidewall statement like the following: "Expected Treadwear: XXXXXX km (XXXXX miles)." Other wording possibilities include: "Projected treadwear" or "Treadwear potential." Such information tracks the current treadwear warranties assigned to many tires. Manufacturers need to reinforce with consumers the fact that treadwear predictions are very much dependent on driving conditions to which the tire is subjected as well as whether the tire has been maintained properly."


And finally from DiscountTireDirect.com:

http://www.discounttiredirect.com/direct/brochure/info/tmpInfoSelectingTire.jsp

"When you are comparing tires within a particular brand, use the UTQG ratings (treadwear) to calculate value; divide the treadwear rating by the price—the highest number should be your pick if you want the best value by wear. This system won't help you compare between brands, however, because there is no standardization for wear scoring. Traction and temperature ratings are standardized and useful for making comparisons between brands."
 

Forum statistics

Threads
107,084
Messages
1,181,281
Members
16,152
Latest member
Satchmoz

Members online

Back
Top