Outer Limits 4x4 Board

Gidday all, I have just fitted 33x12.5x15 MTR,s to my 88 GQ LWB and the handling s pretty crap compared to the 31 inch AT I had on.
I expected some degradation but this seems a bit excessive.
The car tracks along ridges on the road and bumps throw it off line. Is this normal for the more agressive tyres or is there a mod I need to do to improve the handling?
On the plus side the are as good as I hoped offroad

Thanks for any advise
Jim

jumankum wrote:Gidday all, I have just fitted 33x12.5x15 MTR,s to my 88 GQ LWB and the handling s pretty crap compared to the 31 inch AT I had on.
I expected some degradation but this seems a bit excessive.
The car tracks along ridges on the road and bumps throw it off line. Is this normal for the more agressive tyres or is there a mod I need to do to improve the handling?
On the plus side the are as good as I hoped offroad

Thanks for any advise
Jim

what pressures do you run?

do you have a good steering damper, maybe try a RTC damper

I run 33x12.5's and didnt notice any real difference in on road driveability at all in going from 31's

castor issue?

you may find the tyres pumped up to about 40 psi they do that when they put them on the bead

bad_religion_au wrote:castor issue?

caster will not change with bigger tyres only with lift

I checked the tyre pressures after they where fitted. Pressures ranged from 40 PSI to 48 PSI Good old tyre shops aye
Am now running them at 36 PSI all round and dropping the pressure did help a little.

The steering damper was replaced approximately 6 months ago with an Old man emu but its not a RTC.

Vehicle does have a 2-3 inch spring lift but the only thing that has changed is the new rubber. Would fitting the larger rubber possibly show up a already existing problem?

Panhard bushes have also been replaced to stop bump steer problem approx 2 months ago

thanks for the replies guys
Jim

1)What rim width you running? If running of 7's the tyre moves around when cornering because of sidewall bulge. 36 - 40 psi should be OK on-road.

2) Maybe the tyres need a couple weeks running to fully cure.....


A mates car tramlines badly on all-terrains, but doesn't with Centipedes on, go figure......

Cheers,

Pat

ZOOK60 wrote:

bad_religion_au wrote:castor issue?

caster will not change with bigger tyres only with lift

but castor issues are more likely to raise their head with bigger rubber... well bigger rubber tracks better with more castor... so perhaps the castor was already out a little with hte lift, and the bigger rubber has showed it up

Apart from the slight gearing change my ride actually improved when I went from 31" BFG's to 33" Claws......

If you changed rims to fit the larger tyres, do the new rims have the same offset? Changing offset changes your scrub radius, which may have an impact on your steering.

Cheers,

Scott

If I run my claws above 33psi on the road i get the same symptoms as you are describing. Drop them down to 33psi and give them a shot

TUFFRANGIE wrote:If I run my claws above 33psi on the road i get the same symptoms as you are describing. Drop them down to 33psi and give them a shot

Ok I will try that. I used to run the AT's at 32psi but they wore funny
Thanks


I did change the rims. I went from 7's to 8's If its the rims is there a fix?

bad_religion_au wrote:

ZOOK60 wrote:

bad_religion_au wrote:castor issue?

caster will not change with bigger tyres only with lift

but castor issues are more likely to raise their head with bigger rubber... well bigger rubber tracks better with more castor... so perhaps the castor was already out a little with hte lift, and the bigger rubber has showed it up

rail/tram tracking ... sounds like castor ...

I noticed the same going to a wider tyre, I put it down to the extra width giving more friction on the road surface and tugging at the steering a bit more. Also the sidewall construction will affect the handling. Believe it or not, my car responds to steering better, and handles better or is more stable with the Simex ET's than the BFG AT's because of the stiffer sidewalls.

I'd suggest a heavy duty, return to centre steering stabilizer. With the increase in track and width in tyre they have a tendency of following the undulations and "tram tracking" as bogged said.
Cheers,
Ryano

I would describe the steering more as vague rather than tram traking

If I were to turn the wheel going into a bend (say a slight bend) what i would normally expect to be the correct amount, the car may not move at all. So slightly more wheel would then be applied until the car turns in. Unfortunately it turns in the full amount of lock that has benn applied meaning you have to then correct again for the corner. giving a lurching feeling around corners
Same thing happens along a straight road if the wheels hit bumps or ridges. The car moves of line and you tend to have to over correct and then bring it back.

Steering dampers arn't cheap. Anyone wanna lend me one to see if it helps?

jumankum wrote:I would describe the steering more as vague rather than tram traking

If I were to turn the wheel going into a bend (say a slight bend) what i would normally expect to be the correct amount, the car may not move at all. So slightly more wheel would then be applied until the car turns in. Unfortunately it turns in the full amount of lock that has benn applied meaning you have to then correct again for the corner. giving a lurching feeling around corners
Same thing happens along a straight road if the wheels hit bumps or ridges. The car moves of line and you tend to have to over correct and then bring it back.

Steering dampers arn't cheap. Anyone wanna lend me one to see if it helps?

getting your castor checked is cheap

try it, what have you got to lose? the symptoms sound like my 40 when the castor was messed up

jumankum wrote:I would describe the steering more as vague rather than tram traking

If I were to turn the wheel going into a bend (say a slight bend) what i would normally expect to be the correct amount, the car may not move at all. So slightly more wheel would then be applied until the car turns in. Unfortunately it turns in the full amount of lock that has benn applied meaning you have to then correct again for the corner. giving a lurching feeling around corners
Same thing happens along a straight road if the wheels hit bumps or ridges. The car moves of line and you tend to have to over correct and then bring it back.

Steering dampers arn't cheap. Anyone wanna lend me one to see if it helps?

check tierod ends and other sources of movement in the steering

with car off and parked on concrete, get someone to move the steering wheel back and forward just until the wheel starts to turn each way.

check if the tierods ends are moving up and down, if they are they are shagged, if there is no bouncing or wierd movements in the steering linkages you may simply need to tighten up your steering box.

How far does the steering wheel move without the wheels turning? if its more than about an inch and a half you can wind the steering box in a bit, see if this helps (dont wind it in so far that it starts binding).

its possible that the bigger tyres are exagerating a problem with your steering that already exsisted.

otherwise as others have suggested get your castor checked. can do it yourself id guess?

Ok Thanks guys. I have got heaps to look at now.

I think i'll wait to the weekend to get started

thanks again
jim

My MTRs were terrible when new, they took 1500 - 2000Km to settle in,
I would put some Ks on it before I went changing things

TOm

[
check tierod ends and other sources of movement in the steering

Ok Checked the tie rod ends and couln't see any up/down movement but could feel a definate clunk with hand around tie rod with the wheel being moved from side to side. Does this clunk mean replace. The rubber boots are also split
The steering box seems tight enough with very little wheel movement before the wheels start nudging
I have it booked in for a wheel alignment on Fri afternoon but if I replace the tie rods will I need an alignment afterwards? And should I also replace the relay rod at the same time?

cheers Jim