Turbo6.0 Posted November 7, 2014 Share Posted November 7, 2014 So I am building a full frame for my 1973 240Z and I am considering making the track width wider than stock. I'm not sure how much wider at this point. I'm doing it for possibly better handling and also a more aggressive looking stance. Any reason not to do this? Is there a "rule of thumb" to follow when determining track width? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 7, 2014 Share Posted November 7, 2014 (edited) How are you going to make the track wider? Longer control arms? Wheel offset? I've got a car almost together with 15x14's, the splitter (not in the picture) is 76" wide. Mine is done mostly with the wheels. The control arms are about .5" longer per side than stock. Side effect of this is one hell of a lot of scrub in the front. I added power steering to help with that issue. Less scrub is better, but then you'd need longer control arms. I wouldn't widen the distance between the frame rails and try to keep the stock control arms. Longer control arms are better if you can do it. EDIT--I expect to go through lots of wheel bearings! Edited November 7, 2014 by JMortensen Quote Link to comment Share on other sites More sharing options...
johnc Posted November 7, 2014 Share Posted November 7, 2014 A wider track reduces lateral load transfer. In general its a good thing and in a front engine/rear wheel drive car you run a wider front track then rear. This lets you move roll stiffness forward and lets you soften the rear for better corner exit acceleration, but it can increase front understeer. A wider track in front has a negative affect on turn-in (slower) and can give more positive scrub radius depending on how the wider track is achieved. This makes the car more nervous under braking and give a less sensitive feel. A wider track in rear (on a front engine,RWD car) increases oversteer and makes putting power down in a corner more difficult. Reasons not to do this are: 1) Body interference, 2) if you don't get the steering geometry right the car will feel dead in the steering wheel and nervous under braking, 3) increases in under or oversteer depending on which end of the car has the wider track... Quote Link to comment Share on other sites More sharing options...
Turbo6.0 Posted November 7, 2014 Author Share Posted November 7, 2014 (edited) How are you going to make the track wider? Longer control arms? Wheel offset? I've got a car almost together with 15x14's, the splitter (not in the picture) is 76" wide. Mine is done mostly with the wheels. The control arms are about .5" longer per side than stock. Side effect of this is one hell of a lot of scrub in the front. I added power steering to help with that issue. Less scrub is better, but then you'd need longer control arms. I wouldn't widen the distance between the frame rails and try to keep the stock control arms. Longer control arms are better if you can do it. EDIT--I expect to go through lots of wheel bearings! I'm not looking to go crazy. I was thinking to move the control arm mounting points & camber plates outward 1" or so on either side. This is how the car sits now with stock control arms, Megan coilovers and Rota RBRs... Edited November 7, 2014 by Turbo6.0 Quote Link to comment Share on other sites More sharing options...
thezguy Posted November 7, 2014 Share Posted November 7, 2014 How are you going to make the track wider? Longer control arms? Wheel offset? I've got a car almost together with 15x14's, the splitter (not in the picture) is 76" wide. Mine is done mostly with the wheels. The control arms are about .5" longer per side than stock. Side effect of this is one hell of a lot of scrub in the front. I added power steering to help with that issue. Less scrub is better, but then you'd need longer control arms. I wouldn't widen the distance between the frame rails and try to keep the stock control arms. Longer control arms are better if you can do it. EDIT--I expect to go through lots of wheel bearings! Wow that is really cool! How wide are those tires? Quote Link to comment Share on other sites More sharing options...
Turbo6.0 Posted November 7, 2014 Author Share Posted November 7, 2014 Wow that is really cool! How wide are those tires? Thanks! 275/40/17 I think. They fit the wheels really well! Quote Link to comment Share on other sites More sharing options...
johnc Posted November 7, 2014 Share Posted November 7, 2014 Are you building a handling car or a style car? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 7, 2014 Share Posted November 7, 2014 Wow that is really cool! How wide are those tires? If that was for me, they're Formula Atlantic rear slicks, 13" wide. Quote Link to comment Share on other sites More sharing options...
Turbo6.0 Posted November 7, 2014 Author Share Posted November 7, 2014 Are you building a handling car or a style car? Little bit of both I guess Quote Link to comment Share on other sites More sharing options...
Turbo6.0 Posted November 7, 2014 Author Share Posted November 7, 2014 If that was for me, they're Formula Atlantic rear slicks, 13" wide. Haha, probably was for you Quote Link to comment Share on other sites More sharing options...
thezguy Posted November 7, 2014 Share Posted November 7, 2014 Yeah my Comment was directed towards J but turbo your car is looking good too! Quote Link to comment Share on other sites More sharing options...
thezguy Posted November 7, 2014 Share Posted November 7, 2014 Yeah my comment was directed towards J but turbo your car is looking good too! Quote Link to comment Share on other sites More sharing options...
Leon Posted November 8, 2014 Share Posted November 8, 2014 (edited) A wider track reduces lateral load transfer. In general its a good thing and in a front engine/rear wheel drive car you run a wider front track then rear. This lets you move roll stiffness forward and lets you soften the rear for better corner exit acceleration, but it can increase front understeer. A wider track in front has a negative affect on turn-in (slower) and can give more positive scrub radius depending on how the wider track is achieved. This makes the car more nervous under braking and give a less sensitive feel. A wider track in rear (on a front engine,RWD car) increases oversteer and makes putting power down in a corner more difficult. Reasons not to do this are: 1) Body interference, 2) if you don't get the steering geometry right the car will feel dead in the steering wheel and nervous under braking, 3) increases in under or oversteer depending on which end of the car has the wider track... How does increasing front track width increase understeer? EDIT: To clarify the question, my point is that widening front track by itself will decrease understeer. The question should be: why move roll stiffness forward when you've widened the front track? I'm curious to understand the reasoning. Edited November 9, 2014 by Leon Quote Link to comment Share on other sites More sharing options...
RebekahsZ Posted November 8, 2014 Share Posted November 8, 2014 I recommend that you do it with wheel offset. Any other way takes a huge commitment. If you do it with wheels and you later decide you don't like it , it is easy to change. I have changed my mind a lot over the 25 years Ive owned my Z. To do what JMortensen is doing is a commitment that few could follow thru on. And check my recent thread on how wide wheels really make a car a handful to drive. By just changing wheels, I can put skinnies on during the week and drink coffee when I drive, but no way can I do that with my track tires on. Quote Link to comment Share on other sites More sharing options...
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