Optimum scrub radius thread (1 Viewer)

[grinchy]

This is what I get assuming a 13* SAI:

Tire Size - Rev/Mile	Driven Diameter - in	Ideal Offset Change(negative direction) - mm	Tire Reference
665	30.3	-	Approximately Stock LX570 285/50R20(665)
660	30.6	0.0	Approximately Stock 200 Land Cruiser 285/60R18(662)	<-Used as zero point
655	30.8	0.7	Approximately Stock LX570 275/50R21(656)
650	31.0	1.4	-
645	31.3	2.1	-
640	31.5	2.8	Typical 285/70R17 range
635	31.8	3.5	Typical 285/70R17 range
630	32.0	4.3	-
625	32.3	5.0	-
620	32.5	5.8	-
615	32.8	6.6	-
610	33.1	7.3	Typical 315/70R17 Range
605	33.3	8.1	Typical 315/70R17 Range
600	33.6	9.0	Typical 315/70R17 Range and 35x12.5
595	33.9	9.8	-
590	34.2	10.6	-
585	34.5	11.5	-
580	34.8	12.4	Typical 37" tire range
575	35.1	13.2	Typical 37" tire range
570	35.4	14.1	Typical 37" tire range
565	35.7	15.1	Typical 37" tire range
560	36.0	16.0	-
555	36.3	17.0	-
550	36.7	17.9	-
545	37.0	18.9	-
540	37.3	19.9	-
535	37.7	20.9	-

What is the definition of 'driven diameter'? For example the 35x10.5x17" tires I run are 34.6" diameter . . . I previously ran 275/i80r18 which were 35.3" diameter. I'm asking as the Tire referrence column seems to be about three rows too high.

 

[grinchy]

I think you can order EvoCorse's as a +45mm too.

That was my recollection too. They weren't listed on the maine overland site just now. Could be a search error on my part. Perhaps a custom order?

 

[skrypj]

What is the definition of 'driven diameter'? For example the 35x10.5x17" tires I run are 34.6" diameter . . . I previously ran 275/i80r18 which were 35.3" diameter. I'm asking as the Tire referrence column seems to be about three rows too high.

Driven diameter is the published REV/mile converted to diameter. So:

5280/Rev per mile = Driven circumference

Driven Circumference/Pi = Driven Diameter

A 35" tire with a 34.6" actual diameter does not put the hub of the truck at 17.3" off the ground. Its lower than that. Unfortunately, Kenda doesnt seem to publish their Revs/mile

My Territory MT 315/70R17's have a spec diameter of 34.4, but the Rev/mile is 608, which puts its driven diameter at a 33.2. When I actually go measure my ground to hub distance, its more like 16"

 

[grinchy]

Driven diameter is the published REV/mile converted to diameter. So:

5280/Rev per mile = Driven circumference

Driven Circumference/Pi = Driven Diameter

A 35" tire with a 34.6" actual diameter does not put the hub of the truck at 17.3" off the ground. Its lower than that. Unfortunately, Kenda doesnt seem to publish their Revs/mile

My Territory MT 315/70R17's have a spec diameter of 34.4, but the Rev/mile is 608, which puts its driven diameter at a 33.2. When I actually go measure my ground to hub distance, its more like 16"

Ok, it's the 'squished' measurement, got it.

 

[grinchy]

For funsies I put in the stock size rim/tire vs RW vs my current rim using my current tires to see what the scrub lands at. The scrub radius is the distance on the ground that the center line moves. It isn't a 'squished' measurement in this tire calculator.

RWs (17x8, 50ET) + skinny 35s (35x10.5x17) is a zero scrub change from stock (20x8.5, 60ET) with 285/55r20 tires.
ET Alphaequipt Echo (17x8.5, 35ET) + skinny 35s (35x10.5x17) is 16 mm positive scrub change from stock (20x8.5, 60ET) with 285/55r20 tires.

 

[skrypj]

For funsies I put in the stock size rim/tire vs RW vs my current rim using my current tires to see what the scrub lands at. The scrub radius is the distance on the ground that the center line moves. It isn't a 'squished' measurement in this tire calculator.

RWs (17x8, 50ET) + skinny 35s (35x10.5x17) is a zero scrub change from stock (20x8.5, 60ET) with 285/55r20 tires.
ET Alphaequipt Echo (17x8.5, 35ET) + skinny 35s (35x10.5x17) is 16 mm positive scrub change from stock (20x8.5, 60ET) with 285/55r20 tires.

Which is essentially what my table says. The Rev/mile for a 35" tire is right around 600 so 9mm offset change from the stock tire/wheel