Happy to help Normy, don't mention it... <img border="0" alt="[byebye]" title="" src="graemlins/wave.gif" />

 

Yeah, I assumed I would have to remove the spacers that came with the stock set up to go with a 275/40.

That is ok to do with 17 in. wheels but with the original 16 in wheels (club sport, forged, '89 GT), the wheels will make contact with the calipers if the spacers are removed. It is interesting to note that the spacers are 21mm and the increase in tire width is 20mm.

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> ..or stay with the cool-looking 275's.</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Definitely, especially if they're not rubbing.

Ps. Stop eating all those waffles!

 

Just changed tires on my other car from Bridgestone RE 730's to Yokohama ES100's in size 215/45/17.

My impression after a month is that the Yokes are smoother quieter, and more comfortable than the 730's, but not quite as sticky and responsive as the 730's when it comes to the twists and turns of high speed mountain driving.

 

Normy, The trick is the fancy custom offset wheels I have <img border="0" title="" alt="[Wink]" src="wink.gif" /> I had 911 offset wheels when I bought the car. I wanted the wider fronts for the cool factor and the track <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

 

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Randy V:
<strong>THe 275 tires are recommended to be mounted on a wheel 9" to 11" wide.

See the Tire Rack chart:

I've got RE750 275's on 8.5" wide wheels (17 inch wheels).

Bridgestone no longer makes the RE730 in 275 size for 17" wheels.</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Randy:
The Tire Rack is in the business of selling tires. As long as they can be pried onto the rim they'll likely say it's an OK fit. On the other hand, although DEVEK also wants to sell you tires, they don't want to jeopardise your safety to do so. Sure a 275mm can fit on a 9" rim, but how close is it to the limit of a "safe fit", especially for a heavy car like a 928 that is usually driven around corners as if it were on rails? :^(

Unless there is a need for that extra 20mm, the 255mm tires fit perfectly on a 9" rim. That's why Porsche did it!

Lastly, back when I autocrossed, I found the 255mm tires to be better than the 275mm tires, especially in tight corners where it was often beneficial to get the car to oversteer-a bit. ;^) YMMV.

 

Split the difference. Bridgestone makes a 265 for a 17" rim in their S03's.

 

Point taken Ed, but since my car is more 'show' than 'go' (though it does go good) - compared to track cars which are often the opposite - I should be OK.

I wouldn't have gone with such a fat tire if it was a significant safety risk.

 

Randy:
As long as you don't push the car too hard on the street - you'll be ok. However, keep in mind that the speedo will read about 2.5% less than the actual speed.

That may not seem like much, but if you're trying to keep the speed within 20% of the posted limit (over which may be considered "reckless" in some places) it means you'll have to keep it within 17% of the limit - or else you'll be in the "reckless" zone. :^( YMMV.

 

Hi:

I am happily running 285/40/17 RE 730's, and have done so for about 20K miles on 9" 993 rims--stock, no mods. These replaced 275/40/17 RE 71's that I burned up in about 10K (soft). Tires are great, and speedo. is dead on. I can probably run another 25K on the rears at current wear pace.

Also happy with front size @ 245/45/17, but struggle to not burn them up due to bad alignments like most of us. Those are running on 7.5" 993's.

I will replace both with same sizes w/necessary--they are perfect. Driving is combo. of street, highway, trips, and "hobby" driving (saw 160 recently).

Now if I could only get the soft cast 993's to stop bending. Oh well.

Thanks,

Jeff
'87 5-spd
Chips, RMB, Ott
What a machine

 

Not to split hairs with you Ed (well, maybe a little), but considering that the original stock 15" wheels on my car were shod with 215/60/15 tires, replacing them with 17" wheels fitted with 275/40/17 tires, the overall radius of the wheel and tire goes from 12.6 inches to 12.8 inches, resulting in a speedo reading that is only 2% slower. This equates to a speedo reading of 60 mph, when I'm actually travelling at 61.2 mph.

See for yourself here:

<a href="http://www.miata.net/garage/tirecalc.html" target="_blank">Tire Size Calculator</a>

It's a risk I'm willing to take to look stylish I guess.

 

Jeff- Out of curiosity, do you get any rubbing from the front 245's or the rear 285's? I had heard that these sizes were "no-no's" on 17 inch wheels in general...

N!
'85 S2 5 Speed

 

The wheel to tire ratio for a 285mm tire on a 9" rim is 0.80. That's swell below the safety margin for proper fit of 0.85.

I'm glad to hear that it's working for you, but for some of us that might be dangerous. I've seen oversized tires come off their rims during autocross events. Trust me when I say, "It's not a pretty site." <img border="0" title="" alt="[Eek!]" src="eek.gif" /> YMMV.

 

Come on Ed, if you saw a tire come off the rim it was because of an inflation problem not a rim to tire size ratio.

For use as an example, my other vehicular hobby is off-roading, specifically rock crawing. I run a 285 section tire on a 7.5" rim(.67 ratio for those keeping track). I run them at about 15 psi and often the whole wieght of my 5500 lb Mercedes is leaning on one tire (way off camber against sharp rocks etc.). I have never seen a bead pop in ten years of doing this.

I just think that you are badly overstating the potential for a problem. Ease up on the old "safety first" mantra please. We are not all in need of being saved from ourselves.

 

Brent,

Thanks, I appreciate hearing empirical evidence and real world experience even more than I detest being preached to.