Tire size and "heavy steering"

[nagel]

Ok,

Here's my question.  I know tires get "heavier" in feel the larger you go.  Having no power steering eans you take all the hits..

I like the look / capability of the 26" bighorn tires that I have, but they are HEAVY mofo's to steer..  to turn from full left to full right (or vice versa) you feel like it starts easy, then gets harder and then easier. (imagine a bell curve).

I got the wheel adapters from Livewire here, modified them for my hubs, mounted up a pair of 21" tires I had from the ATV's, and they look WAY WAY too small..  I mean, hillariously small, like putting a mid-size car tire on a lifted / jacked truck.

So.. What tips can you offer to help eliminate a little bump steer / make the front end feel not so heavy with the 26" tires.  I have a "stick type" (gibson) stabilizer from the YFZ's that I may try to mount up to the steering column.  But that doesn't make it easier to turn the wheel, it will only help with some bump steer..

Thoughts on tire size vs. how "heavy" the steering feels?

[vidio1]

If the 26" tires are wider than the 21" tires that will change your scrub radius and could make your steering feel heavy........

[LiveWire]

I don't see pictures. Did the inside edge of the tire move in or out? Outside? as vidio 1 said, extra scrub radius will make it turn harder. If either the inside or outside edge of the tire moves out, that moves the center out and increases scrub. Do you have a rack or bell crank style steering? Adjusting the steering for proper Ackermann will reduce steering effort at low to mid speeds.

[fabr]

Control scrub,control scrub,control scrub,control scrub,control scrub,control scrub,control scrub,...................................just cannot be stressed enough.

[Yummi]

So, rumor has it it may be a scrub issue?   

[fabr]

At least that's the rumor.

[Carlriddle]

Hey I was reading on another forum (traitor  ) and they were dead set on bad steering being caused by poor ackerman and scrub radius. 

All I know, once I corrected mine it turned 3 times as sharp.  Get it right or get a bigger place to turn around.

[nagel]

Well, since the 26's were the first tires on the buggy, I don't have something to compare to..  I just think the steering feels heavy..

As for scrub.. Both sets of rims (for 21's or 26's) are 3:2 offsets (3" back, 2" front).  On the race quad I take off the stockers with a 3:2 spacing and change my offset to a 4:1 rim (wider a-arms keep my width there).

Can't be buying ANOTHER set of rims.  LOL not in the budget..  And I've used the 3:2 offsets on my 4x4's forever with no issue (only thought on that is its a 4x4, and the front wheels pull too).

The plans are Stock piranha front single a-arm.  Do I just have to deal with this until I this winter when I can swap in a double a-arm front end?

[vidio1]

If the backspacing of both rims are the same but one set of tires are a different width than the other the scrub radius will be different. Does it feel "lighter" with the 21" tires? Since the 26" tires were the first tires used was the KPI and scrub built to that wheel/tire combo? Is it heavy at slow speed like 5 mph or heavy everywhere? Slow speed maneuvering may be an Ackerman issue especially on hard pack. Going to larger tires won't make a car feel harder to steer if set up correctly. You should be able to move the scrub around to the point it feels so light it will be twitchy at speed.......

[Doug Heim]

scrub radius is set for 21" as per plans. I run 23" with minimum noticable difference.

[fabr]

The diameter will have little to no influence on scrub. Differing wheel offsets do.

[fabr]

If the backspacing of both rims are the same but one set of tires are a different width than the other the scrub radius will be different. Does it feel "lighter" with the 21" tires? Since the 26" tires were the first tires used was the KPI and scrub built to that wheel/tire combo? Is it heavy at slow speed like 5 mph or heavy everywhere? Slow speed maneuvering may be an Ackerman issue especially on hard pack. Going to larger tires won't make a car feel harder to steer if set up correctly. You should be able to move the scrub around to the point it feels so light it will be twitchy at speed.......

This is not correct. Tire width has nothing to do with scrub radius as scrub is determined at tire centerline.

[Carlriddle]

If it was built right for 21" and you put 26" the tire/wheel will need to move out, wider.  Wheel spacers or bigger forearms?  Pics, pics.  Or did I miss them

[LiveWire]

If built for 21 and using 26, with the same offset wheels, scrub radius will be ever so slightly less due to KPI. A heavier tire is harder to turn though.

Can you weld aluminum? 12" wheels? I have a set of 12" aluminum beadlocks, $90 for a pair. If you weld them on the inside of the wheel, you will reduce scrub by about 1/2"

Is it front or rear steer? Rack or bell crank steering?

[nagel]

Not sure what the "planned" tire sizes was, think 21" like Doug mentioned..  But when I put 21's on, it looks like a monster truck with compact car tires.  I didn't even bother to drive it with the 21's because they were so small. (I also knew there would be ground clearance issues in a few areas with them).  They just dont look right (and I'm not fond of the ground clearance, lots of rocks and roots/stumps around).  I used to have a pair of 23" Maxxis Razr II's but stupidly sold them about 8 months ago not even thinking about the buggy..  (Bought them for a rocky race in RI, and HATED how much flex they had and how they pushed in turns on the ATV, but they might have been a better option for the buggy)

For offset, I know I have 3:2 offsets..  Edge plans doesn't specify an offset.  I am familiar with how offset will affect bumpsteer (hence the 4:1 offsets that I change the fronts to on the race quads).  the 3:2 is a very common 4x4 quad offset for the front, hence why I used that offset (also because, well, I had a spare set of rims)

The front is your basic Piranha single a-arm setup.  I bought Doug's old XRV rack from him and am using that for the steering.  Front steer on the rack (scary for me with the amount of trees that can jump out at ya around here!)

In terms of tire sizes, fronts are both 8"  (21x8-10 or 26x8-12). I usually run 8's on the front and 10's or 12's on the rear of my atv's, figured it would transfer over to the buggy.

As for what do I have to compare to?  well, other than quads, a lawn tractor and my non-power-steering '79 chevy monza I had in HS, not much..  For all I know, this may be what you guys are used to..  But it just seems like when turning from full lock (L or R, doesnt matter) that you are riding a bicycle up a hill.  When you reach the center (aka straight forward), you hit the peak and its easier to continue down the other side.  Hmm, am I explaining the feeling correctly?  Basically, its way easier to go from straight forward to L or R full lock, and its way harder to turn from lock to center.

Alignment is done, have about 1/4" or so of toe-in..  Perhaps I should play with toe a little more?  I know on the quads if the tie rods are twisted wrong, or too long, that I get binding at full lock.  And what I'm getting now is resistance (if I added to the tie rod length now I think it would bind like the quads).

The tires I am sure DO play a BIG part, you can not discount the affect of my tread patterns:

http://www.rockymountainatvmc.com/productDetail.do?navType=type&webTypeId=138&navTitle=Tires+and+Wheels&webCatId=8&keyword=trilobite&prodFamilyId=29207

These are primarily for 4x4 quads and utes / SxS's..  Do ya think they may be pulling a bit on the steering?  The pics don't do the lugs depth justice, these tires can really hook up, the rears are just trench diggers if I dump the clutch hehehe..  And I DO have a set (same sizes, front and rear) on a 2000 Wolverine 350 4x4 w/ a Warn 424 to make it 2WD, and the steering on that doesnt seem heavy in 2WD.

I saw in another thread that ITP has released the "Holeshot" series in SxS sizes, aka 25x10-12 and 25x8-12.  When the checkbook allows I want to pick up a pair of the fronts from that line and try them.  If Maxxis made the Razr II's in that size, I would jump on them as well...  I also have a pair of Carlisle 489's in 23x8-12 size that I may mount up to see if they make a difference.. 

In terms of when it feels heavy..  Well, its hardest when you get to full lock.  Slower is worse.  Its almost like it falls in a groove when at full lock and you need to pull out of the groove..

Livewire - I can weld, but not aluminum   And getting the 1 friend around here who CAN weld aluminum, TO weld for ya is tough..  He'll always agree to, but then takes forever / is never available even though ya see him at the local bar all the time. LOL

Pics of the build are here: 

https://www.facebook.com/media/set/?set=a.402506271838.180745.552481838&l=5c8f0818cb

about 1/2 to 2/3 the way down the page you can see some pretty good front end shots..

Thanks guys!