majik16106 Posted November 23, 2003 Share Posted November 23, 2003 i think ill be using a 235/245 up front with a 285 out back.. a happy medium between 235 and 335s... Quote Link to comment Share on other sites More sharing options...
Clifton Posted November 25, 2003 Share Posted November 25, 2003 I run 250/45/15 slicks at low pressure and it's not easy to turn at low speeds. Jon Sorry to get off topic. Are you running the Yokohama's? What kind of psi are you running cold/hot? Thanks Clifton Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted November 25, 2003 Share Posted November 25, 2003 Isnt it true that the offset and backspacing are going to have more of an impact on the "feel" than the rim diameter ever will? Everyone seems to be referring to rims in this thread like a 17" rim is a 17" rim and a 16" is a 16" and so on. The important part is going to be the specifics on the respective rims. One 17" rim could be extremely easy to turn, and another could be extremely hard to turn even if they are the exact same widths. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 25, 2003 Share Posted November 25, 2003 I PM'd you Clifton. Jon Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted November 26, 2003 Share Posted November 26, 2003 Now with the added weight of the 17's and the better tires it's like i'm suction cupped to the road. Puddles at high speed are no problem... cut's right through them.. It may SEEM like heavier wheels are helping, but it's the entire vehicle weight that you're talking about here, the total normal force at the tire. And total vehicle weight can't have changed much. Heavier wheels/tires will always result in less grip under dynamic conditions, as the suspension won't be able to control the unsprung mass as well. Lighter wheels/tires will always have better contact with the road in real-world conditions (i.e., bumps, undulations, etc in the road surface). The suction cup feel you describe is likely 100% due to better tires. Quote Link to comment Share on other sites More sharing options...
col Posted June 20, 2006 Share Posted June 20, 2006 I agree the tyre quality makes a huge diference.a narower tyre with better compound (and tread design)will out perform a wider one of inferior quality any day.I love wide tyres but only buy the best tou can afford(and afford to replace if its more than a show pony)The thing nobody seems to be concidering is geomitary .finding the right camber caster toe out front and rear can and will make or brake your cars ability to grip the road and get a good life from the rather large investment in good tyres. col Quote Link to comment Share on other sites More sharing options...
iaconsultants Posted June 20, 2006 Share Posted June 20, 2006 Tire sizes is always an interesting subject. In the past I talked with BFG and GoodYear and asked them how this works and they both seemed to have about the same answer which actually makes sense. The senerio is two tires made of the same compound and tread style but one is a skinny tire and the other is a wide tire. Also the side wall are the same compound and flex the same way. What was explained to me is that if you assume the car weight is the same for either tire then the only thing that changes is contact distance. So a skinny tire will have a longer contact distance and a small width distance, which would mean it would have better traction front to back. A wide tire will have a short front to back contact distance and a wide side to side contact distance, which is better for side to side traction. If you really think about this it makes sense because the contact area of the same exact tires, just different widths, will have the same contact area on the ground. Since it is the same contact area the wider one has to have a wider contact distance and a shorter front to back distance. There are points that must be recognized which is that if you have a skinny tire with very little side wall verses a wide tire with a lot of side wall, the contact area can change because there will be a convex or concave portion that can make differences to the contact patch (just like under inflating and over inflating the tire). I hope all this makes sense to you guys and if not I would recommend just calling one of the tire manufacturers and they seem to be willing to discuss it fairly easily at least when I called that time they were. One thing about wide tires on the streets with grooves that are in a some what parallel direction to the direction you drive. The wide tires will tend to catch and track along a groove or edge much more than a skinnier tire does. Quote Link to comment Share on other sites More sharing options...
BWRex Posted June 20, 2006 Share Posted June 20, 2006 The stock rims and tires make it easier to maneuver in my garage....Man I've got to get my Z running.....I like the hands on info,It'll make my choice easier when that time arrives.Keep the posts coming on this topic. Quote Link to comment Share on other sites More sharing options...
iaconsultants Posted June 20, 2006 Share Posted June 20, 2006 I forgot to mention at one time I had Comp T/A 295-50 15's in the rear and 245-40 14's in the front with flares of course on a 77 280Z. The car could spin the tires in all 5 speeds but held on like glue in the turns. lots more was done to this car also. Quote Link to comment Share on other sites More sharing options...
col Posted June 21, 2006 Share Posted June 21, 2006 in reference to the tyre area in contact with the road I must disagree If you need more surface in contact with the road with a lighter car simply use lower tyre pressure. It is however better to use softer compounds the wider you go col. Quote Link to comment Share on other sites More sharing options...
Wiisass Posted June 21, 2006 Share Posted June 21, 2006 What are you disagreeing with? And you have to consider a lot more when you lower the tire pressure. This will affect how much force the tire can generate, it's stiffness in several different directions, etc. Adjusting the pressure does a lot more than just put more or less area on the ground. And softer compounds, stiffer construction is the way to go. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2006 Share Posted June 21, 2006 Tire temps generally determine tire pressures and to get the most grip you run as low a tire presure as possible while maintaining an even temp progression across the tread and not rolling over onto the sidewall. With 275/45-16 Hoosier R3S05s on the 2160 lb. 240Z I raced, cold temps were around 25 psi and hot temps around 30/32. That was counter to Hoosier's recommended hot temps around 40 but the pyrometer doesn't lie. Quote Link to comment Share on other sites More sharing options...
Wiisass Posted June 21, 2006 Share Posted June 21, 2006 So what temps were you getting at pressures of 30/32 and what temps were you supposed to be getting at a pressure of 40? Also how was "grip" quantified? Accelerometer, lap times, driver feedback? Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2006 Share Posted June 21, 2006 So what temps were you getting at pressures of 30/32 and what temps were you supposed to be getting at a pressure of 40? Also how was "grip" quantified? Accelerometer, lap times, driver feedback? Am I being tested? Quote Link to comment Share on other sites More sharing options...
Wiisass Posted June 21, 2006 Share Posted June 21, 2006 C'mon, they're easy questions. It's not a test, maybe a pop quiz. I'm just curious and trying to elevate the discussion to a higher level. I didn't mean to come off like I don't believe you, I just want more information. Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2006 Share Posted June 21, 2006 I've got tire temp data for the 275/45-16 Hoosiers from the following race tracks: Willow Springs Buttonwillow LVMS Club Track Thunderhill Sears Point Multiple sessions for each track. Pick one. Quote Link to comment Share on other sites More sharing options...
Wiisass Posted June 21, 2006 Share Posted June 21, 2006 Doesn't matter to me, I'm just interested to see how far people are going with this stuff. Quote Link to comment Share on other sites More sharing options...
Dan Baldwin Posted June 21, 2006 Share Posted June 21, 2006 Even temps across the tread does not *necessarily* imply the quickest setup. No direct experience meself (not nearly consistent enough to make a judgment, and besides, I'm lazy. I just run conservatively high pressures) but at least one successful 240Z race effort found they had quicker lap times with higher temps on the inside of the tread. Tire sizes were somewhat skinnier than 275, though. Just playin' devil's advocate! (plus, who am I to resist an opportunity to stir the pot?) Quote Link to comment Share on other sites More sharing options...
johnc Posted June 21, 2006 Share Posted June 21, 2006 WSIR: LF (O, M, I) 192 - 199 - 202 / RF (I, M, O) 188 - 178 - 170 LR (O, M, I) 198 - 205 - 210 / RR (I, M, O) 191 - 189 - 181 WSIR's most important corners are all high speed right turns. Turn 9 (the last turn before the pits) is a decresing radius 100 mph right hand corner that's right after turn 8 which is a big radius right hand turn. Above temps were taken after a series of high 1:27s/low 1:28 laps which is right at the SCCA GT2 lap record for the track at that time. BTW... I wasn't driving, I took the tire temps. Quote Link to comment Share on other sites More sharing options...
jonzer12 Posted June 21, 2006 Author Share Posted June 21, 2006 Lol, I started this thread 11-17-2003! Quote Link to comment Share on other sites More sharing options...
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