Will a 27.1" tire/wheel diameter, adversely affect trans shift points?

[QuickSilver]

Thinking about purchasing a set of 255/50/17 tires for my '92 Q with a '93 TCU. The total diameter of the tires and wheels will be 27.1". I know that my speedo will read slow. But, will my transmission shift points be effected at all?

The reason that I'm considering using a 27.1" set up (vs. the OE of 26.0") it's the only size with a high enough load index for my existing 17x7.0" aftermarket("cheapo") wheels. The 255/50/17 size is manufacture approved for 7.0" wide tires.

It seems to be the best compromise in regards to safety, looks, and handling.

245/45/17 tires will have need at least a 7.5" wide wheel. 255/45/17 need a 8.0". 235/45/17 ride too rough. (It's what I have now. 93W:hiding:) 225/55/17 have load indexes of 94 and 95.

Like other Q owners, I will be searching for a proper set of wheels(size and strength) to use better size tires in the future.

[AZhitman]

245/45/17's will be fine on your wheels.

Several others are running the same size without problems, including Fred (PalmerWMD).

I have 255/50's on a 7" rim, and I ran 245/50's previously.

[Q45tech]

26" is the nominal unloaded diameter, what counts is the loaded diameter which is more like 25".........same the 27 will be 26" loaded..................center to top 13.5 center to bottom 12.5".

Anyway 4% worst case REAL 60mph would read 57- 57.6-58 mph on speedometer.

The equivalent of changing the 3.538 diff gear to 3.40. Acceleration will be slower say 0.1-0.2 seconds in quarter mile.Highway mileage might go up by 0.3-0.4 mpg especially at 70-75 mph.

I have seen this done succefully with 235/60/16 tires. What you have to watch out for is rubbing on the FRONT-- upper part of the third link.......the rears will be fine.

[QuickSilver]

I thought others were running tires that pushed the restrictions of 7.0" wide wheel. The 245/45/17 size was my first safe, but "uninformed" choice. But I wanted to pusht to 255/45/17 for looks and a higher load index.

However in the NICO tire forum, I was told that 245/45/17's would cause tram lining, poor handling, and have tendency to follow grooves in the road because of crowned treads.

No one was willing to say it would get poor handling with the manufactures blessing of 255/50/17 on 7" wheels. I guess the added height causes less bowing of the tire.

I'm willing to live with a 0.1 or 0.2 seconds loss in acceleration for the meantime. I'll take better gas mileage anytime. It would be nice to have a more filled in wheel well without having to lower the car.

What do you guys say, 245/45/17 or 255/50/17?

FYI- Did you guys know there is aTire/Wheel combination calculator link in Tire/Brakes section? You guys chime in before I could enter the numbers.

[QuickSilver]

Hitman,

You're running your 255/50 with 16" OE chromes, right? Have you noticed a different in handing or wear?

I had a set of 245/50/16 Yokohama's (96 load index) on them for awhile. They were a lot better than my 235/45/17 (96) now.

Fred, I feel for you when you had the 18"'s. I never going to get 18"s, I'm way too cheap.

[AZhitman]

I'd go 245/45/17.

Tried and true, more availability, and the fact of the matter is, tramlining occurrs with ALL wide tread widths. Has very little to do with aspect ratio.

I love my current setup. The Falken Ziex, is, to me, one of the best tires for the money. Great traction, wearing evenly, quiet, sticky, spectacular in the wet, and great lateral stability - Far better than my prior Yoko's in the 245 width.

Plus, they look kick-a$$.

[QuickSilver]

You forgot about the rim lip. Nothing like rim rash to ruin your day, expect maybe a ticket.

I'm going to get my tires from the shop AZhitman posted about, Victoria Tire. The Falken Ziex ZE-512 (99load) is listed for $113.00. It's also #3 on Chet's list of personal favorites in his "econo" list and are far less expensive than the other two favorites.

The 255/50/17 BF Goodrich G-gorce T/A have a load index of 101 and are $130 a peice.

All others things being equal, I guess the 2 extra load index points is not worth the extra $68.00?

[QuickSilver]

Hitman,

I just realized: If you love your 255/50/16's, why recommend the 245/45/17? I think your set up is closer to 255/50/17 and not the 245/45/17.

If that's the case, the extra $68.00 is totally worth it, and the added load index is gravy. I just got to make sure there is not going to be any rubbing in front before I get the Tokico blues.

[SmithSR]

Let's go back to OD...

215/65-15.. 26.00"245/50-16.. 25.65"255/50-16... 26.04"245/45-17.. 25.68"255/50-17.. 27.04"

Hitman's tire OD is ideal..

Toyo Tire has a cool 500 page fitment guide which suggests 245/45-17 for plus sizing into the 17" for the Q45, for all years listed.

Also, 245/45-17 is more readily available, with more options to choose from. ..meaning, you can price shop if you need to. Availability is a huge issue! Ever seen the look on the face of an X5 owner when you tell him a replacement tire for his blowout is 3-5 days away?? Not cool. Point is, rare sizes are just that. Be sure to look ahead and prepare for contingencies(sp?) when buying tires.

Also be aware of that load index and speed rating.http://www.tiresafety.com/size...a.htmh ... e_nav2.htm

[QuickSilver]

Hitman's set up is as close as you can get the OEM OD. But how important is mantaining the OEM OD to handling? Or,

Though the 245/45/17 tires are much close to the OEM OD with only a 0.32" variance, do they necessary handle better than the 255/50/17 tires with a larger 1.10" variance?

I thought I learned today that the 245/45/17 tires on 17x7.0" wheels will handle worse because it is not designed for such a narrow tire. Some 255/50/17 tires are approved for 17x7" tires because the geometry of the taller side wall and wider width allows the tire to handle close to spec. Did I lean it wrong?

The 255/50/17 BF Goodrich tire approved for a 17x7" wheel, while the 245/45/17 is not recommended by any manufacturer.

I'd rather have better handling and adjust to an inaccurate speedo.

[SmithSR]

Handling can be increased to a greater degree by a stickier tire... in either size.

With the differences we're talking about here, the issue becomes pretty much a wash. Either tire size will work, and work well, on the 7" wheel in the real world. With the taller tire, as we know, you get a slightly altered speedo and odometer reading, as well as a minor change in effective axle ratio...geared "taller" means slightly less grunt, but maybe not too obvious with such small differences in OD. Differences, but small ones.

So no matter what, we know that both tires will work. 245/45-17 on a 7" wide wheel is commonplace at a tire shop... and to the ordinary Joe Customer, it works just fine..

As long as the load index and speed rating meet or exceed OEM, and you're aware of the changes, 255/50-17 is a win-win. Unless availability becomes an issue.

[maxnix]

What's genereally missing from this discussion is that with a lower aspect ratio tire, there is less latitude for running a narrower rim. 16x245/50 is different from a 17x245/45 on a 7" wide rim.

I would stay at 26" diameter unless you drive highways exclusively.

[Q45tech]

There is a wide varation by brand in the same size.Hard to make generic comments about a size.Think carefully about adding more than 1.0 inches in real actual loaded tread width above oem tire tread width.The oem XGTV had a wide tread for a 215 on a 6.5" wheel, roughly 7.2" at 33 psi with Q weight..........as you go to lower aspects the tread width becomes closer to the section width.

A 255/16 and a 255/17 can be very different between brands and models.

But you must at least match the oem load index to get decent tire life............gotta watch the void ratio as an 8" wide tread can vary 10% by the actual amount of rubber in the cross section.It may be no better than a 7" wide tire.

Confused almost everyone is.The softest compound almost always wins verse shear size.Tires are a lot easier to change than cars.

[QuickSilver]

Q45tech,

Is the "void ratio" a function of the amount of narrowing of the contact patch caused by a narrow width and smaller aspect ratio?If yes, wouldn't the 245/45/17 tire have a larger void ratio than a 255/50/17 tire?

Also, the 1.10" increase from the unloaded OEM OD with the 255/50/17 tire may actually be much greater than 1.10" depending on the model of the tire? If this is the case with the BF Goodrich tire, which change concerns you the most?

Third link rubbing seems to be the only critical one.

[szh]

I'm going to get my tires from the shop AZhitman posted about, Victoria Tire. The Falken Ziex ZE-512 (99load) is listed for $113.00. It's also #3 on Chet's list of personal favorites in his "econo" list and are far less expensive than the other two favorites.

The 255/50/17 BF Goodrich G-gorce T/A have a load index of 101 and are $130 a peice.

All others things being equal, I guess the 2 extra load index points is not worth the extra $68.00?

I got Falken Ziex's from Victoria Tire. Good company and price, by the way. Tire Rack does not carry Falken! BTW, there is no 255/50-17 in the Ziex though ... there is a 245/45-17 and these are $100 from Victoria Tire and $113 from Discount Tire.

Z

[QuickSilver]

Thanks for the heads up,Z.

The 255/50/17 will be BF Goodrich G-Force T/A. Like the guys have warned, they will have to be special ordered but will only take an extra day or two.

A guy at Victoria Tire, warned about groove following complaints with all BF Goodrich tires. Have been unable to confirm this with other sources. However, the concern could be mute as Hitman say its to be expect with all wide high performance tires.

[TgduMg]

As long as the load index and speed rating meet or exceed OEM, and you're aware of the changes, 255/50-17 is a win-win. Unless availability becomes an issue.

[quote=" Q45tech But you must at least match the oem load index to get decent tire life............[/quote] That said, would you consider a 235/50VR17? This one has a diameter of 26.3, a load index of 96 and the UTQG is 320/AA/A. I'll post again after I get info on others.

[TgduMg]

The Tire Rack has several brands in that size including the Kumhos on their web site. The 235/50R17 is a OEM size for the new Thunderbird and Jag S-Type/Lincoln LS with 17 inch wheels. Another option is the Cooper Lifeliner Touring SLE. I put a set on my Max last March in a 225/50VR17. When I got em the road hazard they gave me included sidewall punctures. The total installed price was under $510. The specs for the SLE 235/50VR17 are UTQG 360/A/A, load index 96 and diameter 26.3.

[QuickSilver]

Yeah, that's a nice option in that its taller(less rough) and stays within manufacturer's spec. But the size is rare enough, I doubt it can beat the value of the Falken's.

I can now rule out the 255/50/17's because the chances of the tire rubbing the third link is too great with my wheels.

I'm going to get the Falken's unless TgduMg can come up with something that makes better sense.

Thanks for all the input guys!!!

[QuickSilver]

Hi TgduMg,

Thanks. I'll visit tirerack to look further into those tires. Having road hazard maybe a nice option. The cars you mentioned seem similar in weight to the Q.