295s On All 4's anyone?

[jsnyng]

Those on backwards?

LOL, yes they were in that picture. I wasn't paying attention because I was dog tired when I first got them and put them on backwards.

 

[Deez-67]

I've heard tires over 255 on the front want to track some what.

 

[19COBRA93]

This is 295-40-18 Falken Azenis on powder coated 2008 GT500 18x9.5 Ford wheels (the best pics I can find of his car):

 

[FR500GT]

http://www.s197forum.com/forum/showthread.php?t=24879&page=3

^^I ran 295/30/19's on all 4 corners with Sportlines then switched over to Saleen Speedlab Coilovers. No rubbing or problems here...

 

[19COBRA93]

I've heard tires over 255 on the front want to track some what.

I can't even tell my 295's are up there. They don't track at all. Fox/SN different story.

 

[whtcanbrwnd04u]

http://www.s197forum.com/forum/showthread.php?t=24879&page=3

^^I ran 295/30/19's on all 4 corners with Sportlines then switched over to Saleen Speedlab Coilovers. No rubbing or problems here...

My god. I still think thats my favorite looking car on this board. Simple, yet so fucking amazing.

 

[Shotokan1509]

I can't even tell my 295's are up there. They don't track at all. Fox/SN different story.

When I ran those Falkens staggered 255/40 & 295/40 18's it tramline pretty badly. When I switched to 275's (20's) all around it is much better.

Go figure

 

[FR500GT]

My god. I still think thats my favorite looking car on this board. Simple, yet so fucking amazing.

Thanks brotha...I was going for a different look than the traditional Saleen.

 

[Norm Peterson]

I see they do bulge on that graph you posted. A little bulge won't bother me as long as its not sticking out the fender line. The pics posted above with the gt500 looks great to me..

Here's a slightly different spreadsheet plot, showing the 295/40 on 9.5" overlaid with the same size tire on its "measuring width" rim (10.5"). I gave up trying to make the shoulder area a curve, but the general shapes of the sidewall bulges should be close enough once you get half an inch or so above the ground. The thin vertical lines are at the point of maximum section width for comparison against the rim flange, though the tighter curvature of this tire on the 9.5" rim should be evident.

Norm

 

[19COBRA93]

If anything, that 10.5" wheel looks too wide for a 295. Trust me, the 295 fit's really well on a 9.5" wheel, and absolutely perfect on a 10" wheel.

 

[whtcanbrwnd04u]

If anything, that 10.5" wheel looks too wide for a 295. Trust me, the 295 fit's really well on a 9.5" wheel, and absolutely perfect on a 10" wheel.

I've got 295 on a 10" wheel right now and it feels really well. I think it should be just fine on a 9.5" like you said.

My next set-up will be 19x9.5 sve's all around in 295/35/19s. I just hope i dont rub being dropped on sportlines.

 

[Al Guapo]

I'm running 295-40-18 Falken Azenis on all four corners. They're mounted on 18x10 Roush's.

Do you have any rubbing at all!? I want to do the same with AM bullitts (same offset) and nittos in the same size. Looks killer btw

 

[19COBRA93]

Do you have any rubbing at all!? I want to do the same with AM bullitts (same offset) and nittos in the same size. Looks killer btw

No rubbing at all. It's not even really close.

 

[whtcanbrwnd04u]

No rubbing at all. It's not even really close.

What lowering springs?

 

[19COBRA93]

What lowering springs?

FRPP K Springs. GT500 takeoff shocks/struts.

 

[Norm Peterson]

The mfr and TRA approved rim widths for this size range from 10" through 11.5", inclusive. That tire size is measured on (and almost certainly its design is based on) a 10.5" wide rim. I suppose I should say "generally range", because you might find a tire that lists a slightly different range.

Anyway, 40 profile tires are not supposed to have much sidewall bulge or "belly", no matter what traditional musclecar/ponycar tire sizes and their required wheel specs made them end up looking like. Those older tires were all tall enough to require the measuring width to be relatively narrower then the same section width tire in 40-ish profiles. Quite a bit narrower in the wider sizes.

In simple numbers, a 295/60 would have been measured on an rim 70% as wide as the tire (so 8", possibly 8.5"). Compare that against the 295/40 needing a full 2" wider rim.

All the nontechnical, visual, and emotional reasons on the planet aren't going to change the technical specs by themselves. I'm not saying that the range of acceptable rim widths won't ever change, but if it ever does it will be due to technical acceptability.

That said, I think somewhere I've seen "85% of section width" used for tires below 50 profile, but I don't know if that applies all the way down to and below 40 profile. If so, that might give you just enough slack if you look hard enough to find somebody's 295/40 that specifically includes 9.5". That does not mean that all other 295/40's are accepted on 9.5" though. Just that one.

For short durations, which includes dragstrip and autocross runs, you can usually get away with crowding or cheating the limits a bit.

It's road-racing, open-tracking - and your extended trips and other situations that occur in normal driving - that are more heavily influenced, due to the accumulation of sidewall flexing heat happening over extended time spans.

45 seconds or less at the dragstrip (counting your deceleration time) and maybe a minute at autocross between tire cooldown periods is not nearly as severe from a heat buildup perspective as, say, three four-hour stints a day driving across Texas this past summer with the car loaded up near its listed capacity would have been.


Norm

 

[19COBRA93]

The above 2010 GT500 with 295-40's and 9.5" wheels made a 900 mile trip this summer without a hiccup. No, I don't have any technical data, but a quick hand on the tire, and visual inspection of the tread-wear suggest there's no problem, or potential problem to be had.

If he decides to road race or open track, maybe we'll give it a second look. Otherwise, they have an OEM appearance and feel, so we're sticking with it. I'd expect just about everyone to agree they're just fine as well.

 

[Digital_Synapse]

The mfr and TRA approved rim widths for this size range from 10" through 11.5", inclusive. That tire size is measured on (and almost certainly its design is based on) a 10.5" wide rim. I suppose I should say "generally range", because you might find a tire that lists a slightly different range.

That said, I think somewhere I've seen "85% of section width" used for tires below 50 profile, but I don't know if that applies all the way down to and below 40 profile. If so, that might give you just enough slack if you look hard enough to find somebody's 295/40 that specifically includes 9.5". That does not mean that all other 295/40's are accepted on 9.5" though. Just that one.

For short durations, which includes dragstrip and autocross runs, you can usually get away with crowding or cheating the limits a bit.

It's road-racing, open-tracking - and your extended trips and other situations that occur in normal driving - that are more heavily influenced, due to the accumulation of sidewall flexing heat happening over extended time spans.

45 seconds or less at the dragstrip (counting your deceleration time) and maybe a minute at autocross between tire cooldown periods is not nearly as severe from a heat buildup perspective as, say, three four-hour stints a day driving across Texas this past summer with the car loaded up near its listed capacity would have been.

I've wondered about this. So the tire designs are different, which is why we see Nitto's running very narrow, their 315 is like a 295. The measured width which is ideal for that tire places the sidewall at an angle which it can tolerate more flex and stress from a neutral position, much like stock dampers on a stock height car. Once you narrow the width of rim and keep the same tire, the beads are now flexed inwards and you basically start stressing and flexing from a non-neutral position, and increased heat and forces are now placed on the tire...much like lowering a car with springs only and not changing up the dampers to compensate for the decreased travel and increased rate, causing the dampers to fail or blow out early in life...or going FI on a motor w/o upgrading the necessary internals, the life is cut down because the material and design isn't made ti withstand that amount of stress for that amount of time. It can, but it will reduce the life expectancy of the part. What if we wear out our tread faster than the sidewalls are wearing due to heat stress? Then we're ok? But that's a gamble...hmmm.

So since not every tire with the same measurements is designed the same, and therefore doesn't fit the wheel the same...is it safe to say that the tires also might have different tolerances of how narrow the rim can run for a respective tire? Then we really couldn't use a blanket equation to apply to all applications.

Sounds much easier to just use the manufacturer's recommended widths, and play it safe. Find a company that designs a width you want for the rim width you have so you're covered.

 

[1SickSaleen]

I fixed it in my above post, but here it is.

http://www.lowered.eu/misc/files/Tyre_Calculator_English.xls

Copy and paste error by me I guess. Sorry about that!

Wow..what an awesome resource. Thanks for posting!

 

[Sharad]

I like this thread! I definitely want to switch the 18x9.5s & 275/40s on my car for a set of 18x10s with 295/40s when my NT05s wear out!