VIDEO : SCRUB RADIUS - What it's All About & The Dynatrac PRO 1550 Knuckle

chitown35 said:
Haha oops I hear knuckles and it translates to reid. I wonder if it's similar though.
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They are similar. I sent Jeeeep a private msg about this so as not to clutter up the Dynatrac thread anymore. The Dynatrac knuckles are massive and badass for sure.
 
Very interesting, but now I have a scrub radius question.
A Jeep JK stock wheel backspace is 6.25". With 32" tires this has the stock factory scrub radius.
Changing to aftermarket wheels with a backspace of 4.5", the scrub radius is now off from stock.
Adding 37" tires changes the scrub radius again, moving it closer to stock.
I would like to know, with aftermarket wheels backspaced at 4.5". What size tires will put you back to the stock scrub radius, or the best scrub radius.
 
cameleer said:
Very interesting, but now I have a scrub radius question.
A Jeep JK stock wheel backspace is 6.25". With 32" tires this has the stock factory scrub radius.
Changing to aftermarket wheels with a backspace of 4.5", the scrub radius is now off from stock.
Adding 37" tires changes the scrub radius again, moving it closer to stock.
I would like to know, with aftermarket wheels backspaced at 4.5". What size tires will put you back to the stock scrub radius, or the best scrub radius.
Click to expand...

Only back spacing will change the center line of your wheels.
 
We are excited to see the positive response. If you've asked us a question, we need time to go over each one and make sure we answer accurately. Please be patient as we're working to answer everyone, and thanks for the questions!
 
cameleer said:
Very interesting, but now I have a scrub radius question.
A Jeep JK stock wheel backspace is 6.25". With 32" tires this has the stock factory scrub radius.
Changing to aftermarket wheels with a backspace of 4.5", the scrub radius is now off from stock.
Adding 37" tires changes the scrub radius again, moving it closer to stock.
I would like to know, with aftermarket wheels backspaced at 4.5". What size tires will put you back to the stock scrub radius, or the best scrub radius.
Click to expand...

wayoflife said:
Only back spacing will change the center line of your wheels.
Click to expand...

I was just about to answer this the same thinking tire size won't change the scrub radius. That is by width. But then I thought about it....the height of the tires would change it as the lines intersect at a certain height. But I don't know the answer of the question. I would take a picture from the front of the Jeep, then on your PC, draw your imaginary lines, then look at how much more or less you would have to increase/decrese the tire height to get the lines to intersect right where the tire patch meets the ground.

Then you'll have to measure on the tire itself, etc.

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WJCO said:
I was just about to answer this the same thinking tire size won't change the scrub radius. That is by width. But then I thought about it....the height of the tires would change it as the lines intersect at a certain height. But I don't know the answer of the question. I would take a picture from the front of the Jeep, then on your PC, draw your imaginary lines, then look at how much more or less you would have to increase/decrese the tire height to get the lines to intersect right where the tire patch meets the ground.

Then you'll have to measure on the tire itself, etc.
Click to expand...

Yes, that was my point. The steering axis inclination line will be at a different point with larger tires. If I understand it right, this will change where the scrub radius is according to tire size.
I'm running a Dynatrac ProRock 44 with Reid racing knuckles, but the scrub radius does not change with this setup. Also have wheels backspaced at 4.5" and 37" tires. I'm thinking this may bring me close to the proper scrub radius.
 
very interesting and informative explanation - you always like it when a pro can make it sound so straight forward.
 
This is turning out to be a pretty interesting thread.

So if Im understanding this right the taller you go the more negative scrub radius you have (at the same BS) and having less back spacing to push the tire out pushes you closer to a zero or positive?
 
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Dynatrac said:
We are excited to see the positive response. If you've asked us a question, we need time to go over each one and make sure we answer accurately. Please be patient as we're working to answer everyone, and thanks for the questions!
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Could you explain any relationship between scrub radius and turning radius?

Thanks!

Edit: I guess even just having a wider axle, instead of less backspacing, helps the arc that the wheel turns in to be smaller. Maybe I misunderstood about it being related to scrub radius?
 
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VIDEO : SCRUB RADIUS - A Look into the Design of the Dynatrac PRO 1550 Knuckle

WJCO said:
I was just about to answer this the same thinking tire size won't change the scrub radius. That is by width. But then I thought about it....the height of the tires would change it as the lines intersect at a certain height. But I don't know the answer of the question. I would take a picture from the front of the Jeep, then on your PC, draw your imaginary lines, then look at how much more or less you would have to increase/decrese the tire height to get the lines to intersect right where the tire patch meets the ground.

Then you'll have to measure on the tire itself, etc.
Click to expand...

Right, I guess I wasn't thinking of it in terms of tire height or at least, in that it would make enough of a change to make that much of a difference. I would be interested to know what the actual measurements look like.
 
VIDEO : SCRUB RADIUS - A Look into the Design of the Dynatrac PRO 1550 Knuckle

Now hopefully more wheel companies like ATX and KMC will make their popular wheels with 5.5" of back spacing if they don't.

I think I know what axle package I want!!

Sent from my iPhone using WAYALIFE mobile app
 
Interesting information. Don't know how much that applies to my tj but I was thinking of going with a 4" bs or 3.5 to push the tires out a little more but this has got me thinking!
 
I'm impressed. That's certainly some useful information that is probably missed frequently when building or modifying any off road vehicle (I know I have). I can definitely relate to the lack of turning ability with the front locker engaged, I've had a situations where this has significantly hindered the line(s) I'm trying to take through obstacles. - Many thanks for sharing, I know I'll strongly be focusing on this more when I start replacing the axles on my build. :thumb:
 
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