Tire Fitment

A forum for owners of S30 and S130 Datsun Z's... 240Z, 260Z, 280Z and 280ZX!
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davidmoralesbello
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Car: 1078 Datsun 280Z

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So I'm sure there are numerous threads regarding this topic but since it's pretty specific I'm hoping someone might have an opinion/answer.
My recently purchased '78 280Z came with Cooper Cobra 215-60-15 mounted on Konig Rewind 15x7 wheels. I want to mount 16 inch wheels with 55 or 60 profile tires and want to keep the same 215 width. The MSA site sells the Konig 16x7 wheels but recommends using no larger than 205-55-16 tires. I realize I would be gaining 1 inch by going from 15 to 16 inch wheels but I would be decreasing tire profile by going from 60 to 50 profile so my desired tire/wheel set up would not be any taller. Wouldn't it make sense that I could keep the same 215 width?


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AZhitman
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Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
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Those tire size recommendations (no offense to MSA) are bunk.

In order to retain the same OD as what's on there now, I'd be looking for 225/55/16. Very common size, so there's lots of choices.

What you have now: 25.4" OD, 6.7" tread width
225/55/16 tires: 25.7" OD, 7.1" tread width

http://www.tirerack.com/tires/TireSearc ... iameter=16

Keep in mind, the Z can swallow up some pretty decent-sized tires. We run 255/45/16 on all four corners on our Z (of course, that's on an 8" wheel).

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davidmoralesbello
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Car: 1078 Datsun 280Z

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Thanks very much Hitman. So it seems as if I go with your suggested 225/55/16 I could eventually even lower the car a bit and not run into any clearance issues, right? Any tire recommendations for all season high perf?

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AZhitman
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Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
Location: Surprise, Arizona
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Correct. There's quite a bit of leeway - The Z sat WAY high from the factory. Make sure you get a good alignment afterwards.

As far as tire recommendations, there are 70 tires in that size on TireRack. I'd lean towards something in the treadwear range of 250-350. Other than that, let the reviews be your guide. :)

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davidmoralesbello
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Car: 1078 Datsun 280Z

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Hitman, if I went to a 17 x 7 wheel with 225/50/17 tires I would have a 0.7" increase in heigth and 0.4" increase in width. I would love the look of 17s on the Z but do you think I would get into clearance issues with that tire/wheel combo?

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davidmoralesbello
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Car: 1078 Datsun 280Z

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I just found another tire option: 225/45/17. This would actually be 0.2" lower in diameter and 0.4" increase in width when compared to my actual 215/60/15 setup. This might be a "safer" alternative. Agree?

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AZhitman
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Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
Location: Surprise, Arizona
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Personally, I'm not a fan of 17's on a Z - too modern. However, opinions are a dime a dozen! :)

Keep in mind, any increase in diameter and width carries with it the penalty of additional rotational mass AND unsprung weight, both of which sap handling, acceleration, and braking performance.

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Speedgato
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Hitman couldn't be more correct. Remember, your wheels and tires are just another set of gears your drive train needs to turn.

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davidmoralesbello
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Speedgato and Hitman, point well taken but is there really a difference in usprung weight between going with 16x7 wheels with 225/55 tires VS 17x7 wheels and 225/45 tires? Isn't the increased wheel weight compensated by the decreased tire weight?

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Speedgato
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No. Weight isn't the only concern. The larger circumference of the wheel (gear) makes the available inertia loose it's power. Like when you're on a bicycle and you have the chain on the highest sprockets, your pedal doesn't translate into more speed. It may be easier to turn but the energy you expend doesn't translate to more power.

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davidmoralesbello
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But wouldn't the "gear" be the whole whee/tire unit, not just the wheel? So if the diameter of the wheel/tire unit doesn't change appreciably changed (whether you have a larger wheel with a lower profile tire or a smaller wheel with a taller profile tire) wouldn't the inertia loss be similar?

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AZhitman
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Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
Location: Surprise, Arizona
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As long as OD remains constant, correct. We're getting into minutiae - the important point is, larger wheel = more material = more weight.

That applies to the tires as well. A 17" tire will weigh more than a 16" (of the same brand, aspect ratio & width). Not a lot.

But there's no "offsetting" involved - larger wheels and tires weigh more.

Realistically, this decision should really hinge on three factors:
-Personal preference
-Fitment
-Price

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davidmoralesbello
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Thanks again Hitman. After reading tons of stuff online most people tend to go for 16s instead of 17s based on vintage look, overall ride quality, availability and cost. There are still conflicting reports of fitment and I don't want to order a wheel/tire combo that might force me to do bodywork. I hate to dwell on the point and become a PITA but are you sure 225/55/16 on 16x7 will clear everything?

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AZhitman
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Posts: 71061
Joined: Mon Apr 29, 2002 2:04 am
Car: 58 L210, 63 Bluebird RHD, 64 NL320, 65 SPL310, 66 411 RHD, 67 WRL411, 68 510 SR20, 75 280Z RB25, 77 620 SR20, 79 B310, 90 S13, 92 SE-R, 92 Silvia Qs, 98 S14.
Location: Surprise, Arizona
Contact:

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Absolutely. Remember, we run 255/45/16 on all four corners on our Z on an 8" wheel, and our Z is lowered about 4".

Offset is important - If you're looking at the setup MSA sells, they'll be fine, and will leave you plenty of space.


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