« previous next »
Pages: 1 [2]   Go Down

Author Topic: Tire size and "heavy steering"  (Read 6201 times)

0 Members and 1 Guest are viewing this topic.

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #15 on: July 07, 2011, 06:41:14 AM »
Offsets do not affect bumpsteer. Do you know how to check bumpsteer? IMO your issue is entirely due to the steering geometry of the Edge single arm setup.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

nagel

  • Guest
Re: Tire size and "heavy steering"
« Reply #16 on: July 07, 2011, 07:04:45 AM »
Its quite common for the ATV racers to change from 3:2 to 4:1 to minimize the effects of bumpsteer as well as make the machine easier to steer. Everybody from B class on up has usually made the change.  And we don't necessarily want to add width as its typically 48" limit. 

See this link for an explanation:
http://www.exriders.com/archive/topic/300433-1.html

As for how to check, remove shock, lift front end and move the arm through its travel with tie rods connected and watch from above for change in toe.  Correct?? 
Logged

Offline Carlriddle

  • Another build? What are you thinking?
  • Hero Member
  • ****
  • Posts: 4593
Re: Tire size and "heavy steering"
« Reply #17 on: July 07, 2011, 07:16:17 AM »
Yep.(bumpsteer check)

KPI is off, inside by 1-1.5" guessing

Hard to tell ackerman from photos.

large wide heavy tread tires multiply effort

Rack could be locking up at ends of turning, but with above list.

Logged
You can keep your CHANGE, I'd like to keep my DOLLAR.

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #18 on: July 07, 2011, 08:07:54 AM »
+1.  Carl hit it on the head IMO.
« Last Edit: July 07, 2011, 08:16:04 AM by masterfabr »
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #19 on: July 07, 2011, 08:14:55 AM »
Quote from: nagel on July 07, 2011, 07:04:45 AM
Its quite common for the ATV racers to change from 3:2 to 4:1 to minimize the effects of bumpsteer as well as make the machine easier to steer. Everybody from B class on up has usually made the change.  And we don't necessarily want to add width as its typically 48" limit. 

See this link for an explanation:
http://www.exriders.com/archive/topic/300433-1.html

As for how to check, remove shock, lift front end and move the arm through its travel with tie rods connected and watch from above for change in toe.  Correct??
I don't disagree with that in the least. At least not the thought.  I maintain  that wheel offset has no effect on bumpsteer.  Bumpsteer is bumpsteer . What is being changed  with an offset change is SCRUB.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

LiveWire

  • Guest
Re: Tire size and "heavy steering"
« Reply #20 on: July 07, 2011, 08:34:20 AM »
Scrub then causes wheel whip where you hit a bump and it yanks the wheel to that side hence why some people think that is what bump steer is. So when everyone is saying you have too much scrub, that is the same thing the quad guys are fixing. They are just not using the correct terminology.

 ;D
Quote from: vidio1 on July 04, 2011, 11:57:29 AM
...that will change your scrub radius and could make your steering feel heavy........
Quote from: LiveWire on July 05, 2011, 09:00:08 AM
..extra scrub radius will make it turn harder...
Quote from: masterfabr on July 05, 2011, 11:23:04 AM
Control scrub,control scrub,control scrub,control scrub,control scrub,control scrub,control scrub,...................................just cannot be stressed enough.
Logged

LiveWire

  • Guest
Re: Tire size and "heavy steering"
« Reply #21 on: July 07, 2011, 08:41:51 AM »
Ways to reduce scrub:

More offset wheels: 4+1 instead of 3+2
Hubs with mounting flange closer to center of buggy
Increase KPI by moving lower ball joint mount out on knuckle or upper ball joint mount in. What is important is the pivot point, not the mounting point. Depending on your knuckles, if the lower ball joint is below the mount and you can move it above, that will increase the angle. It will also decrease camber gain. Crap, I just remembered you have single A-arm so don't have ball joints.  If you can tilt the knuckle pivot more, it will increase camber as well making the tire ride more toward the inside. You could angle the spindles down the same amount of the knuckles to change the camber back and then have higher KPI.
Logged

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #22 on: July 07, 2011, 08:44:46 AM »
Quote from: LiveWire on July 07, 2011, 08:34:20 AM
Scrub then causes wheel whip where you hit a bump and it yanks the wheel to that side hence why some people think that is what bump steer is. So when everyone is saying you have too much scrub, that is the same thing the quad guys are fixing. They are just not using the correct terminology.

 ;D
YUP,YESSIR,CORRECTOMUNDO!!!!
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline vidio1

  • Fabricator
  • **
  • Posts: 123
Re: Tire size and "heavy steering"
« Reply #23 on: July 07, 2011, 10:37:50 AM »
Quote from: masterfabr on July 06, 2011, 06:54:48 AM
This is not correct. Tire width has nothing to do with scrub radius as scrub is determined at tire centerline.

Yep your right I wasn't thinking.
 As for tire diameter, wouldn't a larger tire change the scrub? The KPI angle would be the same, but the difference in length from the spindle to the ground would move the center line of the tire to KPI imaginary spot on the ground relation. I would be minimal, but a 21" to a 26" might be noticeable....
Logged

Offline Carlriddle

  • Another build? What are you thinking?
  • Hero Member
  • ****
  • Posts: 4593
Re: Tire size and "heavy steering"
« Reply #24 on: July 07, 2011, 10:48:17 AM »
correct.  Even the taller tires, the KPI looks as if its still too far inside.  More KPI or 32" tires?
Logged
You can keep your CHANGE, I'd like to keep my DOLLAR.

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #25 on: July 07, 2011, 10:50:22 AM »
Yes tire diameter will change the scrub but only slightly. Very slightly unless the KPI is radical. It MAY help with steering effort also. Honestly, I feel you should just live with it ,change wheel offset to help out for now and in the end get a "real" front suspension design in place in the future.
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"

Offline BDKW1

  • Hero Member
  • ****
  • Posts: 896
Re: Tire size and "heavy steering"
« Reply #26 on: July 09, 2011, 10:23:49 PM »
Quote from: Carlriddle on July 07, 2011, 10:48:17 AM
correct.  Even the taller tires, the KPI looks as if its still too far inside.  More KPI or 32" tires?

Bigger tires. I run 31" fronts on My glass car with manual steering. No issues......
Logged

nagel

  • Guest
Re: Tire size and "heavy steering"
« Reply #27 on: July 10, 2011, 06:14:18 AM »
Quote from: masterfabr on July 07, 2011, 10:50:22 AM
Honestly, I feel you should just live with it ,change wheel offset to help out for now and in the end get a "real" front suspension design in place in the future.

Thats what I was figuring..  Just wanted to see if there was something simple and easy and obvious that I was missing...  The KPI on the single a-arm though is not a quick fix :(  And did I understand it correctly, that the top of my spindle should be angled in about 1 - 1.5" more to get a more correct KPI?

Thanks for the education too between scrub and bump-steer... I started educating my friends on that one..  Its amazing how two niches of off-road riding call the same thing something different..
Logged

Offline fabr

  • Administrator
  • *
  • Posts: 93176
Re: Tire size and "heavy steering"
« Reply #28 on: July 10, 2011, 08:44:50 AM »
Quote from: nagel on July 10, 2011, 06:14:18 AM
Thats what I was figuring..  Just wanted to see if there was something simple and easy and obvious that I was missing...  The KPI on the single a-arm though is not a quick fix :(  And did I understand it correctly, that the top of my spindle should be angled in about 1 - 1.5" more to get a more correct KPI?

Thanks for the education too between scrub and bump-steer... I started educating my friends on that one..  Its amazing how two niches of off-road riding call the same thing something different..
I don't know. I don't guess at these things. You will need to scale that out if you really want to know how much.
We are certainly a niche BUT WE use the CORRECT terminology. ;D ;D ;D ;D ;D ;D
Logged
"There can be no divided allegiance here.  Any man who says he is an American,
but something else also, isn't an American at all.  We have room for but one
flag, the American flag... We have room for but one language here, and that is
the English language... and we have room for but one sole loyalty and that is a
loyalty to the American people."
Theodore Roosevelt 1907

-----------------------------------------------------------
 " You have all the right in the world to believe any damn thing you'd like, but you don't have the right to demand that I agree with your fantasy"
Pages: 1 [2]   Go Up
« previous next »
 
SimplePortal 2.3.7 © 2008-2024, SimplePortal