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PostPosted: December 4, 2017, 4:27 pm 
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Joined: November 13, 2017, 7:35 pm
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Thanks to all that has responded so far. Yesterday I typed out a reply that had all the specs from what I have and what I'm going to but the site went down and it never got saved. After I get the basic frame done I think I will put my 17" wheels that I have up against it to see what way I want to go. The main reason for going with the bigger R brakes is purely aesthetic. The factory front Volvo rotor is actually smaller than the rear and I feel that it should be the opposite, especially when I am building the car myself. For the next few days I am out of town for work, so that might give me more time to do math (hopefully better) and see which direction I will actually end up going.


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PostPosted: December 4, 2017, 9:09 pm 
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Always Moore!
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KB58 wrote:
Approach the problem from the opposite direction. Go to Tire Rack or equiv, bring up the super high performance street rubber and see what sizes they carry - end of story. It's an academic argument if what's "right" can't be had; pick something that exists and move on.

I future-proofed Midlana design by designing around tire diameter, so what builders use for wheel size doesn't matter. I had the advantage of starting from a clean sheet, where tire selection is the first design decision. You guys building per plans that assume a really small tire diameter, yeah, that's going to be a problem. Go by tire OD and work backwards.


Tirerack currently carries 12 tires in 195/50R15, 32 in 195/55R15, and 23 in 205/50R15. I wouldn't panic and say the sky is falling when one distributor has 67 different choices. I get the point of making sure tires are still available but as long as the 1st and 2nd generation Miatas are around we're going to see a handful of high performance and all season 15" tires.

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PostPosted: December 4, 2017, 9:40 pm 
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Except, now filter that for tire compounds suitable for really light cars - which means tread compounds of less than 200 or so. All-season radials will never get up to temperature when only loaded with 400 lbs instead of the usual.

Just to see what tire makers are having to deal with these days, how many know that the Hellcat weighs around 4500 lbs?! Sheez.

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PostPosted: December 4, 2017, 11:26 pm 
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Always Moore!
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From what I've seen most builders are not putting extreme performance summer tires on their cars.

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PostPosted: December 5, 2017, 10:41 am 
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Fair enough, a cruiser doesn't need performance rubber, though stopping distance will still be an issue.

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PostPosted: December 5, 2017, 1:24 pm 
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The voice of reason
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I was hoping for 225/15 tires. I saw all season and also what are DOT racing slicks but not much in the middle. Not even finding 8" rims that are suitable, at least not easily. It seems the slightly narrower tires and 7 inch rims are more common?

I think Kurt was a little more forward looking in his choice of 25" rubber. I was thinking 23" for the street and ~21" for the track. Perhaps 25" street and 23"-24" track makes more sense

I'm having a hard time getting myself to move from the 14.5 lb. 10" rotors to the 21 lb. 11" rotors. The 10" rotors are only available in 5x5", So that makes the rim choice more complicated too, along with wanting a large positive offset for scrub radius reasons.

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PostPosted: December 5, 2017, 4:19 pm 
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horizenjob wrote:

I'm having a hard time getting myself to move from the 14.5 lb. 10" rotors to the 21 lb. 11" rotors. The 10" rotors are only available in 5x5", So that makes the rim choice more complicated too, along with wanting a large positive offset for scrub radius reasons.


Do 2 piece rotors that way you can use any hat you'd like, plus they tend to weigh less than one piece rotors

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PostPosted: December 6, 2017, 2:02 pm 
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My answer to this is completely dictated by what you plan to do with the car. The car I detailed on this forum is only used for the track. It's never seen the street, and I don't envision it ever will. In that case, my choice of tires is pretty much dictated by what fits my annual budget. In a single track day season, I could go through a couple sets of tires, so my main concern is cost per tire. I've run everything from 255/17's to 335/18's. I've used high performance street tires; but mostly R compound slicks. I've used Hoosiers, Pirellis, Hankooks, Kumhos, and the odd Goodyear. How I choose tires is based on what is available on the used market. I started with 17 rims because they fit the brakes, and it's what many racers in the area were using. Finding slicks with only a few heat cycles for pennies on the dollar was pretty easy. Then, they all upgraded to 18 inch wheels, so I had to as well. Now, I run 17's on the front because I can still find 275 or smaller tires used. The rears I run 18's in widths of 305 or larger.

I asked the race teams about why they would switch to 18's (and now 19's) when that meant a heavier wheel/tire and more rotating mass. Longevity was the answer. The larger the tire, the longer it stays consistent on the track. The contact patch is longer, and they get less local distortion of the tread so the tire doesn't heat up as much during a longer race (say 30 minutes or more).

For a street car, the tires should be lasting much longer so it goes from an annual budget to a once every couple of years budget. In that case, I would be more worried about what looks good and much less worried about performance. Tires are so good these days, and you are so limited on what you can do on the street, looks simply becomes the major factor.

Ken


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PostPosted: December 6, 2017, 6:22 pm 
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On my (stalled) build I started with wheels and tires, bought new, and then discovered that I struggled with roll centres using the uprights I had and had to buy another set of lower-profile tires. As was just said, pick a rolling radius associated with some common sizes and do some preliminary suspension calculations before buying tires, wheels and brake rotors. I followed hot rodders' advice and bought wheels and tires right at the beginning, but got burnt. Design first, buy once. :BH:

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PostPosted: December 6, 2017, 9:13 pm 
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Warren,

Sorry to read that your build is stalled. I fully realize life can get square in the way. Hope the distraction doesn't involve any pain or tragedy.

Hope you can get back to it soon.

Cheers,

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