Tire spec question - buy 4 or 5?

[BradleyB]

I getting ready for a road trip with some off-road detours in WBGV, and it's time to get off of the OEM Deulers H/T's (10K miles).

I'm in that classic conundrum of wanting a tire with it all: quiet enough to hear my wife's every word on the highway, good mileage, enough traction chops to make it home from fire trails or the snow. Most of my time is on the daily commute; several weekends a month on marginal roads and fire trails.

So, I'm looking at the (stock size) Kumho SAT KL61 because they seem to strike the balance I'm looking for. I'm just wondering if its specs are enough off of the Dueler currently mounted as the spare that I should go ahead and spring for a 5th Kumho. The Dueler is listed as 31.7" overall diam and 659 rpm. The Kumho is listed as 31.6" overall diam and 606 rpm (this confuses the hell out me, smaller overall diam and fewer rpm's).

Are these two specs different enough rotationally that I should consider a Kumho on the spare, too?

'Cause for the price of 5 Kumho's, I'm in the price range for 4 pretty darn good tires, like, GY Silent Armor.

Thanks,
Brad

 

[proquip]

The 606 number must be a typo. No, virtually no difference between 31.7" and 31.6". To put it in perspective, by the time the Dueler's are ready to be replaced (between 2/32" - 4/32" left of tread), the tires will be about 31.1" in diameter. Needless to say, a tenth of an inch difference between different tires is negligible.

Good luck!

 

[1engineer]

Lets do a little math:
I will pick 60 mph just because its easy -
(60mi/hr)*(5280ft/mi)=316,800ft/hr
(316,800ft/hr)/60min/hr)=5280ft/min duh

Tire 1:
((31.7in)*(3.14))/12=8.29ft/rev
(5280ft/min)/(8.29ft/rev)= 636.91 rev/min

Tire 2:
((31.6in)*(3.14))/12=8.27ft/rev
(5280ft/min)/(8.27ft/rev)= 638.45rev/min

Less than 2 rpm difference if all tires are inflated exactly right. NBD

 

[Jtraskell]

Lets do a little math:
I will pick 60 mph just because its easy -
(60mi/hr)*(5280ft/mi)=316,800ft/hr
(316,800ft/hr)/60min/hr)=5280ft/min duh

Tire 1:
((31.7in)*(3.14))/12=8.29ft/rev
(5280ft/min)/(8.29ft/rev)= 636.91 rev/min

Tire 2:
((31.6in)*(3.14))/12=8.27ft/rev
(5280ft/min)/(8.27ft/rev)= 638.45rev/min

Less than 2 rpm difference if all tires are inflated exactly right. NBD

Damm engineer's, makes all of us look stupid..........lol

Ok, maybe just me:lmao:

 

[Mtn.Rush]

Lets do a little math:
I will pick 60 mph just because its easy -
(60mi/hr)*(5280ft/mi)=316,800ft/hr
(316,800ft/hr)/60min/hr)=5280ft/min duh

Tire 1:
((31.7in)*(3.14))/12=8.29ft/rev
(5280ft/min)/(8.29ft/rev)= 636.91 rev/min

Tire 2:
((31.6in)*(3.14))/12=8.27ft/rev
(5280ft/min)/(8.27ft/rev)= 638.45rev/min

Less than 2 rpm difference if all tires are inflated exactly right. NBD

Christ I THOUGHT I did good in college. Thanks for making us look like 2nd graders......:thanks:

 

[MarkWalker]

Tire Dimensions Made Simple - Discount Tire

 

[Jtraskell]

Tire Dimensions Made Simple - Discount Tire

Not fair. You have to figure this stuff out like 1engineer, with a slide rule and an abacus. :lookout:

 

[BradleyB]

Lets do a little math:
I will pick 60 mph just because its easy -
(60mi/hr)*(5280ft/mi)=316,800ft/hr
(316,800ft/hr)/60min/hr)=5280ft/min duh

Tire 1:
((31.7in)*(3.14))/12=8.29ft/rev
(5280ft/min)/(8.29ft/rev)= 636.91 rev/min

Tire 2:
((31.6in)*(3.14))/12=8.27ft/rev
(5280ft/min)/(8.27ft/rev)= 638.45rev/min

Less than 2 rpm difference if all tires are inflated exactly right. NBD

Thanks to everyone who weighed in. All helpful. If I've got my math straight, 1engineer used the spec'd overall diameter to produce revolutions per mile -- rpm -- (same as revolutions per minute at 60mph).

Makes me think there's more to the manufacturer's specs for rpm than overall diameters, 'cause the OEM (Tire 1) spec for rpm is 657 vs. the calculated 637 rpm (about 3% fewer rpm than manuf. spec).

Still makes me wonder if the Kumho spec is a typo/misprint or not.

So, either way, if I end up with the Kumho's, it looks like using the spare won't be an issue.

 

[JB.]

So, either way, if I end up with the Kumho's, it looks like using the spare won't be an issue.

Agree.

Still makes me wonder if the Kumho spec is a typo/misprint or not.

Yeah, that 606 number looks bizarre. When I was researching tires I was getting quite a bit of conflict between the numbers I was getting from tire companies via email and the numbers coming from online tire stores, so take that into consideration.