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Wheel/tire discussion (carry-over)


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John made a good point about our meandering conversation on someone's wheel/tire post so I started a new one. 

 

@JMortensen, @Dat73z

 

Attached is the specific tire we run in EP (I say "we", as if I actually have the car on the road). Il post some pics of the wheel/tire combo on the car. Agree with Jon that the racing tires certainly feel a lot lighter than DOT street tires, although I have not weighed a 245 tire as a comparison. As I said in my previous post, the combo came-in at 33lbs w/ a wheel weight of 13.6lbs. I am still amazed how Koenig can achieve that knowing the top-of-the-line TE37V is just under 11lbs in the same size. The Koenig's were $109 ea on Summit and lighter than the conventional (and much more expensive) panasports. 

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Wow. Those cantilevers are giving up some weight. Must be the sidewalls. I guess they're 19 or 20 lbs.

The FA rears are 13.75 x 24.5 x 15, only weigh 23 lbs, and they're 100mm wider and 1.5" larger diameter. The FA fronts are 9.4 tread width and 17 lbs. Wheels are a lot heavier though. The steel wheels I'm running are 24 lbs IIRC, so 47 for each corner. Could probably get that down 10 lbs if I spent a whole bunch of money on wheels. I kinda like the steelies though. Shows how low dollar the build is, like the stained plywood splitter... 

image.png.41207cf524ff6c7934e6675ec5a5ebbb.png

Edited by JMortensen
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Hey if you have the torque and braking to make the steelies work, why not! The extra inertia can more easily be over-come through those upgrades than getting expensive lightweight alloy wheels anyway. 
 

EP’s is pretty darn restrictive, but that’s what I liked about it. Super limited on what the motor can output (Greg’s landed at 260hp in his most competitive seasons if I recall correctly) and improved braking beyond pads and slots comes with weight penalties. In that scenario, all you have left at your disposal is cutting rotational inertia, weight, etc. As I mentioned in the previous post, building the car makes me feel like It’s becoming more Miata and less a “hot rod” 😂 You end up “trimming the fat” like a welterweight fighter, but when those restrictions are lifted, who doesn’t want to bulk-up like Mike Tyson! 
 

hey just a thought on that splitter. I have been playing around with my spare polycarbonate from the windshield. This stuff feels like “wonder” material. It’s stiff but doesn’t buckle, bends but snaps-back consistently, super hard to scratch with even course sandpaper. I think I’m going to give-it-a-shot for my own splitter. I’m only allowed to cover the leading edge of the air dam back to the front wheel well opening, so for a limited distance it should work OK. Il probably use thin 3mm stock, but reinforce it with an AL beam near the rear. it’s also rather easy to cut with the “right” Bosch jig saw blade. 

 

 

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Brakes will be the hardest thing to make work.  My friends used the S130 vented discs and front calipers to try and help with temp and get a bigger pad.  In the end those required a bendix pad that worked at very high temps and as much air as can be sent to the disk and caliper.  The rotors had to be cryo treated or they were throw away items after a weekend or two of races (buy good quality versions).  When cooling down after races or practice I would use blowers and turn the wheels if you can.  On the rears they used disks and a wilwood calipers and a lot of ducting.

 

You're going to have knockback and all you can do is minimize it.  If you can, float the rotors on hats.  I'd also use bearing spacers and make sure you check all the tolerances with the bearings (REM finish them) as those and the spindle flexing will be a big factor in knockback.  Make sure you brace the struts.  On the wheel side I'd test their stiffness to lateral force.  The stiffer the better for their weight.  The stiffer wheels will work with slightly less camber.  I'm sure I'm missing some of the tricks that were used. 

 

EP sucks when it comes to brakes on the S30s.  Good luck and have fun.

 

Cary

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