wheelman Posted February 27, 2011 Share Posted February 27, 2011 (edited) Today I started looking to buy race tires for this year's auto-x season and ran across a special deal. I can get a set of Kumho V710s for $440.00 plus shipping, the catch is they are closeouts and were manufactured in 2008. So, are they worth buying or should I spring for tires manufactured in 2010? The vendor is a major firm so I'm not worried they were stored outside but wonder if they change chemically just sitting for several years. Edited February 27, 2011 by wheelman Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 27, 2011 Share Posted February 27, 2011 I wouldn't buy a 3 year old set of race tires unless they were bagged and treated with VHT or similar. If you're looking for cheap, try used slicks. Quote Link to comment Share on other sites More sharing options...
mark Posted February 27, 2011 Share Posted February 27, 2011 I just bought a couple of the older victor racers. For half the price of new I gambeled they would be OK. I'll go to the track in April for sure and maybe March for a quick shake down. I'll let you know. Quote Link to comment Share on other sites More sharing options...
wheelman Posted February 28, 2011 Author Share Posted February 28, 2011 (edited) Thanks for the replies. Turned out they were gone by the time I decided to move forward with it so ended up buying a set of this years manufacture. BTW: It was Tire Rack closing out the last of the 2008 production they had in stock. I imagine they store the tires in a controlled environment but not bagged or treated with VHT. I've thought about trying slicks but haven't done enough research to know which would be best for my application (auto-x). One of the guys I run against drives a Midget with a rotary, he ran takes offs last season, had a real hard time getting enough heat into them, even in the Tri-Cities where we get high 90, low 100 temps during the summer. The Z is very easy on tires so I think I'd have the same problem, I was able to get the v710s up to temp late in the day last season but only when I had a co-driver. Any recommendations on slicks to consider? I run 16x9.5" rims in the front and 16x10" rims in the rear. Edited February 28, 2011 by wheelman Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted February 28, 2011 Share Posted February 28, 2011 smaller tires will run hotter.i run 225-50-15 on 15x7 wheels.but its a daily driver/track car with stock fenders.if the car is well balenced and tire temps are equal across the tread but on the cool side it would tell me that you could run a smaller tire or a softer tire like an old goodyear race slick Quote Link to comment Share on other sites More sharing options...
jhm Posted February 28, 2011 Share Posted February 28, 2011 If you decide to check out used slicks, I highly recommend this fellow: "http://shop.ebay.com/i.html?_nkw=usdrrt&_sacat=0&_dmpt=Race_Car_Parts&_odkw=usdrrt+13&_osacat=0&_trksid=p3286.c0.m270.l1313". High marks for availability, prices, and quick shipping. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 1, 2011 Share Posted March 1, 2011 I think the reason to run used slicks would be price. If you want to make the most competitive use of your slicks, it will require a lot of changes to the car, probably most notable would be the spring rate. When I ran them I couldn't get them up to temp either (I did see temps in the 180 range as I recall at a track day, operating temp was supposed to be 220 for the tires I was running), and my understanding now is that the spring rate was much too soft. A harder spring works the tire which builds up heat. More grip also equals more roll so more camber loss and worse wear compared to a less sticky tire. Still, I could get a full season of autox and a couple track days out of the Yokohama slicks that I was running. For the price you can't beat them. Goodyear and Hoosier make 16 x 10 slicks in bias ply (more forgiving and requires less neg camber) and radial (more ultimate grip). I'm sure there are others as well: http://www.hoosiertire.com/rrtire.htm http://www.racegoodyear.com/tires/sports.html Quote Link to comment Share on other sites More sharing options...
wheelman Posted March 4, 2011 Author Share Posted March 4, 2011 It's interesting you mention changing spring rate Jon, I just went from 250/225 F/R to 350/325 and changed from Tokico HP Blue to Koni 8610-1437 struts. Last season I ran tire pressures as follows: 22 front, 20 rear with the Kumho v710s. At those pressures I had great grip, could get some heat into the tires and the wear line went all the way to the edge of the "tread". Measured with an IR sensor at the surface the highest temps I saw was in the mid 120* range, biased a little to the inside edge of the tire. Fronts didn't get as hot as the rears, maybe 5* lower on average. I was running -2.5* camber front and -.5 to -1 camber rear. this season I'm going to try -2 front, -1.5 rear and see if I can run a little higher pressures. The rounded edge on the Kumhos likes less camber, I think I had to much dialed in last year. My next big change to the car will be adding some sort of toe adjustment to the rear end, either adjustable arms or offset bushings. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 4, 2011 Share Posted March 4, 2011 These might provide some insight: http://forums.hybrid...nquaiffetorque/ http://forums.hybridz.org/index.php/topic/80753-where-to-focus-to-take-it-to-the-next-performance-level/page__p__766000__hl__%2Bspring+%2Bheavy85__fromsearch__1#entry766000 http://forums.hybridz.org/index.php/topic/70348-poor-wear-on-hoosier-radial-slicks-need-advice/page__p__665785__hl__%2Bspring+%2Bheavy85__fromsearch__1#entry665785 Quote Link to comment Share on other sites More sharing options...
wheelman Posted March 4, 2011 Author Share Posted March 4, 2011 Thanks for the links Jon, makes me think I'm headed in the right direction except I may want to add droop limiters or leave the front camber where it is. That brings up a couple questions: 1. Are you guys running droop limiters on both ends of the car? I was considering adding them only to the rear. 2. Do we have any pictures of droop limiters installed so I can steal some ideas from how others have done it? (I'll search after posting this but figured I'd ask while I'm here) 3. I'm assuming you measure toe out at the tread of the tire, correct. Example: distance between front edges - 40", distance between rear edges - 39 7/8" gives 1/8" toe out. Those distances are just made up, I have no idea right now the actual width of the front of my Z. BTW: In relation to the first thread you linked, I'm running a clutch type LSD, I assume this makes the weight transfer off the inside rear tire less of an issue as compared to an ATB but introduces more tendency to push on corner exit under power. I run a relatively large rear bar to combat this, is that a good idea or just a band aid? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 4, 2011 Share Posted March 4, 2011 Cary has run the limiters on both ends, I believe 74_5.0L_Z did as well. I have made them for both ends but haven't actually run them yet, car is just about to come off of the rotisserie, so I'll be able to tell you how they work in 2027 when the car actually moves under its own power. If you search you'll find my threads on how I did them for my car. The rear came out really good, it's simple out of the way, etc. The front is a bit iffy. It's hard in front because of the steering. I'll have to get everything set up and then make sure there is clearance, but I think it will be OK as it is. Yes, toe is at the tire, or a toe plate which basically is a plate strapped to the tire or bolted to the hub which sticks out front and rear. I don't know about the LSD, to be honest. I think there is a traction advantage to be had with no rear bar (the bar puts a lifting force on the inside rear in order to level the car out). But if you have too much roll by removing the bar, then you might be better off with it on. I would say take one end link off and see what happens, but in order for it to be a fair comparison you'd still have to get the same roll resistance in the rear which means you'd have to up the spring rate to try it in a way that the balance would be the same but the lifting effect of the bar would be neutralized. Quote Link to comment Share on other sites More sharing options...
DrSideways Posted March 4, 2011 Share Posted March 4, 2011 Today I started looking to buy race tires for this year's auto-x season and ran across a special deal. I can get a set of Kumho V710s for $440.00 plus shipping, the catch is they are closeouts and were manufactured in 2008. So, are they worth buying or should I spring for tires manufactured in 2010? The vendor is a major firm so I'm not worried they were stored outside but wonder if they change chemically just sitting for several years. Race tires are like bread. There is fresh bread, not so fresh,stale, then moldy. I like fresh race tires and fresh bread:) Alan Quote Link to comment Share on other sites More sharing options...
wheelman Posted March 4, 2011 Author Share Posted March 4, 2011 Ok, I think I have two more question left, at least in this thread anyway. The links you posted above mention running springs in the 400/450 range, what strut inserts are run with those spring rates? Are they custom built units, revalved Konis, Bilstiens, what? What has changed the thinking in using higher spring rates? When I first joined HZ people were thinking 250s were to much and over time would damage the unibody structure, now 450s are being used and nobody seems to be concerned. I added sub-frame connectors to my Z but haven't put in a cage yet, is it the additional stiffening that makes it possible to run the higher spring rates without damage or was that really a false concern? Quote Link to comment Share on other sites More sharing options...
johnc Posted March 4, 2011 Share Posted March 4, 2011 I generally don't recommend spring rates above 350 lb. in. (2.5hz) unless the car is hugely stiffened and you know exactly why you want that rate. I have a customer that's transplanted a BMW E36 front suspension into his S30 and he's running 450 lb. in. front springs. He knows why and is very specific in what he wants the front to do. Quote Link to comment Share on other sites More sharing options...
wheelman Posted March 4, 2011 Author Share Posted March 4, 2011 Fair enough, I was just curious about the apparent change in attitude toward the higher rates. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 4, 2011 Share Posted March 4, 2011 (edited) Gotta keep the tires happy. If the tires aren't happy at 350 lbs, then you up the spring rate and do what it takes to make that work. The trend in autox is towards higher spring rates with wide sticky tires. I would love to know what John Thomas is running, but I know Vic Sias ran 400+, Tom Holt is up over 400 if I recall, and from what I gather a bunch of the guys that Cary races with are over 400. I've been picking up a bunch of springs from 500 to 700, going to do some experimenting. I don't think this works on a stock car, but it does if you reinforce the chassis. Is your car still a street car? This is where you start getting into that point where it's not going to be for much longer. Edited March 4, 2011 by JMortensen Quote Link to comment Share on other sites More sharing options...
wheelman Posted March 4, 2011 Author Share Posted March 4, 2011 technically it's still street legal but I never drive it on the street any more and it's trailered to events now. I'll try these springs for this season, keep notes (or at least attempt to) and then re-evaluate next fall. Like I said the next big change I plan to make is adjustable rear geometry, maybe I'll do a cage at the same time. I supposed it's time to gut the interior and build a dash with guages that are accurate. Neither you or John C. addressed the strut question, what are the guys who run 400 and higher spring rates using for struts? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted March 4, 2011 Share Posted March 4, 2011 Konis mostly from what I've heard. I don't think they need a revalve, John would know more about that, but I seem to remember that when they last updated the struts they were really valved for stiffer springs anyway... Tom Holt and Cary ran the Ground Control Advance Design struts. I am going to try Bilsteins. I think katman also said they ran Bilsteins with these kinds of rates in the strut thread, and of course I forgot Dan, 74_5.0L_Z as another Z running 400 in/lb springs (Konis I think). Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted March 4, 2011 Share Posted March 4, 2011 Yeah IIRC katman's setup was the bilsteins revalved to 300/100: http://forums.hybridz.org/index.php?showtopic=69623&view=findpost&p=643255 Maybe pertinent (and related?) summary by katman on general setup in another forum: http://www.improvedtouring.com/forums/showpost.php?p=179217&postcount=7 Dave Quote Link to comment Share on other sites More sharing options...
mark Posted April 16, 2011 Share Posted April 16, 2011 Just to follow up. I was at VIR on the north course with the THSSC a couple of weekends ago. I bought a set of victor racers for the rear that were on close out. The production date was 2007. I ran a personal best time on the north course and set FTD on sunday. I'll buy another set if they still have a few left the next time I need tires. They were half the cost of new. Money well spent. Quote Link to comment Share on other sites More sharing options...
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