Leith280zlt1 Posted July 31, 2007 Share Posted July 31, 2007 Ok, I've been looking for wide wheels for my z for a while now. I've got about 400hp to the wheels and i've flared the fenders so I can put some rubber in there. I can go as big as 12" wide if I want to. My question is, for road racing, how much rubber do I need? Will too wide wheels affect how the car handles? Also, in order to fill out the flares, if I decided to go with say a 10.5" wheel, I would have to use a huge negative offset. Something like a 2" backspacing. I'm getting kodiak wheels, so they'll make them like I want. But where do I need to be in terms of offset and width so that I optimize handling and minimize wheel bearing load. I don't want to have too much negative offset. But I don't know what I need. Any help will be appreciated. Quote Link to comment Share on other sites More sharing options...
greenmonster80 Posted July 31, 2007 Share Posted July 31, 2007 I cannot answer with specifics but I run a 12 rear and a 9.5 front with no issues at all. Feels fine as far as handling and steering. I have not tracked the car simply spirited driving to and from work. Quote Link to comment Share on other sites More sharing options...
Wedge Posted July 31, 2007 Share Posted July 31, 2007 id say 9 or 9,5 in front and 10 in the back is a great combo but i dont have much experience its just what my track buddy told me . Quote Link to comment Share on other sites More sharing options...
jknc90 Posted July 31, 2007 Share Posted July 31, 2007 I just got my wheels in and they're 15x8 in the front and 15x10 in the rear. I'll let you know if I have any issues when I put them on b/c I don't have tires yet. lol Quote Link to comment Share on other sites More sharing options...
JMortensen Posted July 31, 2007 Share Posted July 31, 2007 The issues so far as I'm aware of them are: 1. Scrub radius increases with wider tires, so more kickback going over bumps through the steering wheel. 2. The farther you get from 0 offset the worse the leverage is on the wheel bearings. The larger the tire the worse for the wheel bearings too, but I would think your example of 10's with 2 inch backspacing would be pretty hard on the bearings. 3. I think there is a point at which you can have too much tire, but I think you'll have a really hard time getting to that point on a Z. I know tube80z ran 10's and 13's on his FP car that weighed under 2000 lbs. Quote Link to comment Share on other sites More sharing options...
Clifton Posted July 31, 2007 Share Posted July 31, 2007 Look at what size tires you want to run before getting the wheels. If you want a 315 in the rear, a 10.5 would be the minimum. 335 would need more. Quote Link to comment Share on other sites More sharing options...
Leith280zlt1 Posted July 31, 2007 Author Share Posted July 31, 2007 I'm leaning toward going with 12" wide wheels and 16" dia. That would make a decent offset wheel so that I wouldn't load the bearings too bad. I could then do a little better than the stock bs if I went with the 12" wheels. I'm planning on road racing with this car, so I am concerned primarily with what will perform best. I don't think the 12" will be too wide because I know many models of the vettes and vipers run wheels that wide, and then some... And I think I have enough power to utilize that much rubber. I can't go over 16" dia if I want to do SCCA events. 15" may be better, but I'm having trouble finding tires for either one. 12" is just sooo freaking wide. Greenmonster, what tires are you running on the rear of yours? Quote Link to comment Share on other sites More sharing options...
tube80z Posted August 1, 2007 Share Posted August 1, 2007 I'd be careful with wheel widths if you're planning to run a particular class. Some have class max widths. Adding on to the first point Jon raised above, you need to remember increased scrub leads to increased steering induced weight transfer and higher steering linkage forces. You're going to have a car that has a tendency to follow ruts and is going to be hard to control at the limit with the amount of steering kickback. You may want to consider power steering at some point. With regards to the vette it's a completely different type of suspension and doesn't have these issues as much. So they can run a wider wheel without having to deal with as many issues. Carrol Smith once said not to go over 20% of your wheel/tire width in scrub as a max. I'm pretty close to that running a 10 inch wide wheel. And I can tell you that at times it feels like the car drives me. So be careful. A good combo I think is 10 front, 12 rear. And think about power steering. Cary Quote Link to comment Share on other sites More sharing options...
Leith280zlt1 Posted August 1, 2007 Author Share Posted August 1, 2007 I'm not planning to go super wide up front. I think the max I want to go is about 9.5". I don't want the problems with steering you guys are talking about. But I do need some meat under the rear with the v8 power. I just don't know what the issues are on the rear. I don't think theres as much to worry about back there, but I just wanted some other opinions. Thanks alot for all your help. Quote Link to comment Share on other sites More sharing options...
evildky Posted August 3, 2007 Share Posted August 3, 2007 I'm an autocrosser and have 300 whp in a car that weighs 2100 lbs, I have 17x11's up front with a 295 series tire and 17x12's in the rear with a 315, the problem I've run into is that the car isn't heavy enough to get full use of the tire, a 10" wheel with a 265 would probably be about as usefull but cheaper and easier to fit and weigh a whole lot less weight, I honestly didn't notice the extra weight at the wheel at all, the previous keizer 15x7's with 225's weighed only about 30 lbs each, the ccw's with the fat rubbers weight about 50 lbs each! if your car is heavier than maybe the big fatty tires will be of more use but at 2100 lbs it requires judicial use of the go pedal Quote Link to comment Share on other sites More sharing options...
johnc Posted August 3, 2007 Share Posted August 3, 2007 I can't go over 16" dia if I want to do SCCA events. What class? Quote Link to comment Share on other sites More sharing options...
Leith280zlt1 Posted August 8, 2007 Author Share Posted August 8, 2007 I would be in the GT class with all the modifications I've made so far. I need to talk to someone who really knows the SCCA rules to be sure, but that's what I saw that fit my car best. Quote Link to comment Share on other sites More sharing options...
johnc Posted August 8, 2007 Share Posted August 8, 2007 A Datsun 280Z with a LT1 V8 is not legal for any SCCA GT class. Its also not legal for any national SCCA road racing class, but within your region look for a Super Production class (SPO). Here in Cal Club that would be your only choice. They would not let you run the car in their ITE class because of the rim width and the engine swap. Buy the rule book. Quote Link to comment Share on other sites More sharing options...
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