heavy85 Posted November 21, 2005 Share Posted November 21, 2005 I've now decided to go with slicks vs DOT rubber for next year. I'm thinking about Hoosiers in either 23x9.5x15 or 23.5x11x15 in a R35 compound. Either way I'm guessing I'll run Diamond Racing wheels in 15x10 size. I've got flairs and coilovers and stock brakes so clearance is not a concern. Any recommendations on which would be better - is wider always better here as looking at National pictures it seems to be the trend. And then would the 11" wide ones better fit on 12" wheels? I haven't bought the wheels yet so I'm flexible and just trying to decide what I really need. Last question is any recommendations on offsets? Thanks Cameron Quote Link to comment Share on other sites More sharing options...
Guest 81na ZX Posted November 21, 2005 Share Posted November 21, 2005 I'd suggest R25 compound. Depending on how your local/region set up events, R35's might not get warm enough. Quote Link to comment Share on other sites More sharing options...
gramercyjam Posted November 21, 2005 Share Posted November 21, 2005 I assume you are going to run in Prepared or Modified, as slicks are not allowed in Stock, Street Prepared or Street Modified or Touring classes. A 10" wide rim is the widest you can go in Prepared without penalties. I would guess an R25A might be problematic on such a heavy car but I haven't tried such a soft compound myself. Think of soft tar on a hot day. Thats about the consistency of an R25. Most folks run 22.0 X 10.0-16 R35 on a 16X10 rim round here. Or go for the 23.0 X 9.5-15 on a 15X10. I think you will like the responsiveness of the tire with the shorter sidewall though. Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 21, 2005 Share Posted November 21, 2005 If you run with a pavement temp under 95 degrees the 25A may be faster. It also depends on how long you run and how hard the car is on tires. If the temps are higher or your car is hard on tires then I'd opt for the 35. Cary Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 22, 2005 Author Share Posted November 22, 2005 I'm going with the R35 compound as I dont want two sets and will run over the summer. So for size I come up with two options - the 16's or the 15's. The 16 inchers weigh 156 lb and cost $1428 (including the 16x10 diamond racing wheels) while with 15 inchers would come in at 140 lb and $1104 again including the wheels. I realize that the smaller diameter 16" tires might actually have a lower PMOI to offset the additional weight of the wheel so I think it would probably be somewhat close to a wash effective rotational weight wise well other than the obvious 16 extra pounds of unsprung weight. Also, JohnC has said before that you cant effectively run very low profile tires without $$$$ struts which I dont have. So is it worth it to go with the 16's in the end and will they work the best on my non-trailered dual purpose car? Also any recommendations on wheel offsets w/ flairs would be greatly appreciated. Thanks again for the advice Cameron Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 22, 2005 Share Posted November 22, 2005 A friend of mine runs the goodyear 16 inch radial in a 250 compound with 550 springs and koni insterts. It works very well although many claim the shocks can't deal with this. There's nothing wrong with picking a known quantity and the 16s certainly are. You might be faster on 15s or even 13s. But you'll have to figure out how to make them work. If you're up for the challenge it can be fun. It can also be very frustrating when you start going backwards. Cary Quote Link to comment Share on other sites More sharing options...
zlalomz Posted November 22, 2005 Share Posted November 22, 2005 The 23x9.5x15 slicks are cantilever and are designed for a 7 inch wheel. Thats what I used since they are plentiful and cheap used but they don't have the most even wear pattern. Pics of the Goodyear version 23x9x15 on 15x8 wheels are in my gallery on the green car. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 22, 2005 Share Posted November 22, 2005 If you're just going to slicks you might want to get something that lasts a little longer and isn't quite as competitive. I was running Yokohama A005s which are a pretty hard compound road race tire in a 250/45/15. I wasn't as fast as I could potentially have been, but one set of tires would last a full season of autox with a couple track days, and then I'd switch them out because they were hard thru heat cycling, not because they had worn out. The problem for me was always $$$. I didn't have fully adjustable suspension when I first put slicks on. I couldn't get enough neg camber at that time, so if I had high $$$ slicks I would have just burned them right off the car in a weekend. By running a harder compound and easing into adjustable LCAs and TC rods, I was able to make the tires I had work pretty well. I now feel that next time out I might have a chassis and suspension that can really use high $$$ slicks to full advantage, but I'm still a bit hesitant at throwing lots of money at tires, because they are the most expensive consumable in racing as Cary pointed out and I'm not shooting for the national championship. Quote Link to comment Share on other sites More sharing options...
zguitar71 Posted November 22, 2005 Share Posted November 22, 2005 If you are running your car with the full interior like mine then weight penalties for wheels over 10" do not matter. The penalty is 100LBS for wheels over 10" (per inch I think). Your car is at least 2300LB, 200 LBS over the minimum. I use the r250 compound (like the Hoosier 25A) with out any problems like over heating, and they have lasted 2 years and I have raced in 100 degree heat. Your car will not be competitive with most FP cars so I would go for the lighest wheel/tire combo and less $$$ you can. A set of 15x7 with cantalivers is fairly light and so are 13" combos and they cost much less. I paid $980 for my new Diamond wheel and New Goodyear 23x9x15 R250's. Even though most are running 16x10 wheel you will be amaized at the handeling of the cantilevers and smaller wheels. You will have to run a -12 offset with the combo like I run. The tires are about 1/2" from the strut tubes and 1/2 under the spring perch (small diameter). You might be able to find a set of alum. wheels in a 0 offset and run a 1/4"-1/2" spacer and loose 8+ LBS over the Diamond wheels (mine weigh 21 LBS each, too heavy). Quote Link to comment Share on other sites More sharing options...
Guest AlsoRanFPrepared Posted November 23, 2005 Share Posted November 23, 2005 I personally run Hoosier R25 C3000's in the 22.5x9.5x15 up front on 10" wheels and run the 23.5x11x15's out back on 12" wheels on my EM car. You do not want to run the 11's on a 10" wheel as they were designed for a 14. Even a 12" or 13" wheel is a compromise and I have to run fairly low pressures in the back to keep the tread relatively flat and maintain even heat/wear. I dont have my notes with me but 17psi comes to mind for a ballpark pressure in the rear. The 9.5's I use are designed for a 10" rim and are not cantilever. I can usually get a season out of a set of R25 take offs. Keep in mind they don't wear out before they get hard and dont stick as well. But, if you are really looking for speed at any one event, buy some new tires and have at it. FWIW, I was still able to take first at the national tour event locally on my old tires and dying motor. For my setup at the local autocrosses I dont get too greasy and overheat them even in the summer time. So, if you haven't bought wheels yet you can run the same setup I do and should have some success at a relatively low cost. Even with the 12" rims, you may have to put some pretty big flares on there to stuff things in between the uprights and the fenders. Alternatively you can run the 9.5's at both ends. Something else to keep in mind, my EM car is nowhere near a BSP or FP car in terms of weight, distribution and suspension setup. -Mark Quote Link to comment Share on other sites More sharing options...
tube80z Posted November 23, 2005 Share Posted November 23, 2005 I personally run Hoosier R25 C3000's in the 22.5x9.5x15 up front on 10" wheels and run the 23.5x11x15's out back on 12" wheels on my EM car. I dont have my notes with me but 17psi comes to mind for a ballpark pressure in the rear. The 9.5's I use are designed for a 10" rim and are not cantilever. I can usually get a season out of a set of R25 take offs. Keep in mind they don't wear out before they get hard and dont stick as well. But, if you are really looking for speed at any one event, buy some new tires and have at it. The 15 inch Atlantic tires are a good choice and readily available. For what it's worth I run the 13 inch Atlantics and have similar pressures (looking for 18 to 18.5 HOT). Make sure you get fronts if you go for the smaller tires all round. In the 13s there is the same size that is a rear and when you get them on the front the car won't turn for crap. Just something to watch out for. If you go to a pro Atlantic race you may be able to haul off some of the yokohama radials. They are designed to run on a 12 inch rim in the rear and you'll be in the 24 to 26 HOT pressure range. I've found it much easier to use two sets of wheels/tires. I keep notes on use and match them that way and flip each on the wheel after three events. The bias ply tires will grow as they are used you can use this as a guage on what tires to match up if you buy used. Each year I introduce a new set to replace those that are in the worst shape. This has allowed me to drastically reduce my tire budget. I have the tires on nitrogen and they are bagged when not in use. Cary Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 23, 2005 Author Share Posted November 23, 2005 I've decided to go with the FA 22.5x9.5-15 in R35 compound. These seem to be a good compromise with enough sidewall for my dual pursose set-up while being much lighter (and cheaper) overall than the 16's and the cantilever's I dont fully understand but from what I read they seem to be on a bit lower level of performance than the others. Even though I'm not going for Nationals here if I'm going to do it I might as well go as fast as I can. I'll run them on 15x10 Diamond wheels and think I need 5" backspace (?) - can anyone cofirm that? So now that I've decided I'm going to start trying to find some used tires. Now I just need to find some struts. Last night I finished taking appart my suspension in preparation to section the struts. I was planning on SA Konis but since they are NLA I dont know what to do. My Illumina's are tired and I wanted to upgrade but there doesn't seem to be any other options for < $1,000. Cameron Quote Link to comment Share on other sites More sharing options...
zguitar71 Posted November 23, 2005 Share Posted November 23, 2005 The tires are 10.8" wide and a -12 offset (5" bs) puts them at a 4.9" to the inside of the wheel well. The small diameter will have the tire below the spring perch unless your coil overs are set lower down than the original spring perch. If you have 4.9" of clearence to the strut tube then you are ok. My tires are 10.4 inched on a -12 offset so they are 4.7" to the inside and have more than .2" to spare so you should be good but I would measure the area 3 times and mabey once more too make sure, once you buy the wheels they are yours, no returns (do not ask why I know this). The clearence will be very close. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted November 24, 2005 Share Posted November 24, 2005 Heavy85: Koni has superseded their strut for the Zcar with another, it's model '8610 1437 Race'. I got mine from shox.com for around $130 ea. They are single adjustable. They are made to section the strut 2 inches, although I have not done that with mine yet, I'm running them in my full length strut housings with spacers under them. My car is a 78, the struts housings have a larger diameter then the 240s. If your car is a 240 you might better check the fit. JohnC seems to think the compression damping is to high for road racing. I can't confirm this as of yet because I haven't driven it on the track yet. Just a thought, because the general consensus seems to be the tokico illuminas wear out quickly with spring rates above 250 lbs. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted November 24, 2005 Author Share Posted November 24, 2005 Heavy85: Koni has superseded their strut for the Zcar with another, it's model '8610 1437 Race'.... JohnC seems to think the compression damping is to high for road racing... general consensus seems to be the tokico illuminas wear out quickly with spring rates above 250 lbs. When I got the car it had 500 lb/in springs which were just scary on the street as there was not enough compliance and it felt like it was just skipping around bumps. I think this is what killed my Tokicos as the strut rods are actually discolored in a very small range of travel like they got hot. I'm now running 225F / 250R. Anyway I'm aware of those new Konis but at least according to JohnC they have something like double the compression damping of the old ones and are therefore not suited to the Z unless you get them revalved which adds like $100 per strut! That's why I'm still looking. Cameron Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 24, 2005 Share Posted November 24, 2005 When you get Tokicos hot they get that blue discoloration. That in and of itself doesn't mean the strut is bad. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted February 18, 2006 Author Share Posted February 18, 2006 The 23x9.5x15 slicks are cantilever and are designed for a 7 inch wheel. Thats what I used since they are plentiful and cheap used but they don't have the most even wear pattern. For $$ reasons I'm starting to rethink my choice. I've googled and Ebay'ed but not found anything. Where can I get these cheap? Considering saving for ls1 instead ..... but still need some sticky tires. Thanks Cameron Quote Link to comment Share on other sites More sharing options...
zguitar71 Posted February 18, 2006 Share Posted February 18, 2006 http://www.jbracingtires.com I have never bought from these people but they have an add in the back of Sports Car mag. They clam to have all sizes of Goodyear slicks from full to 1/2 tread left. Quote Link to comment Share on other sites More sharing options...
zguitar71 Posted February 18, 2006 Share Posted February 18, 2006 Just tried the web site and it took me to a search engine not the web site, sorry I should have tried it before posting it. Quote Link to comment Share on other sites More sharing options...
tube80z Posted February 19, 2006 Share Posted February 19, 2006 http://www.jbracingtires.com I have never bought from these people but they have an add in the back of Sports Car mag. They clam to have all sizes of Goodyear slicks from full to 1/2 tread left. Their site is http://jbracingtires.net/index.htm Cary Quote Link to comment Share on other sites More sharing options...
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