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Location:
Brisbane
Registered:
May 2004
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Location:
Melbourne
Registered:
May 2004
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 00:59
 
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Id say the only problem may be the gueard clearance.
and a little more load on wheel bearings...
Jezza
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I supported Toymods
Location:
melbourne
Registered:
June 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 01:24
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i have 14 by 6 inch rims on my car, with P10 offset, and the tyres rub on the plastic guards around corners (but my car is very low at the front)
i would reccomend you lip your guards, rip out the plastic guards or at least replace the oblts that attatch them to the body with zip ties, if the wheels you mention will fit at all.
just do lots of dummy fitting i guess
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Location:
Brisbane
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 01:40
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At least you are incresing the front and rear track the same....efects should cancel out?
You might find that the car tends to tramline with the much wider tyres, but these things happen 
Cheers
Wilbo
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Location:
Terrigal
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 01:47
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You'll be changing the scrub radius also at the front.. Not real sure what effect thats going to have but I understand its not a good thing.
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I supported Toymods
Location:
melbourne
Registered:
June 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 01:57
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oh yeah, mine does tramline fairly noticably (meaning when you turn in it turns more itself basically) this isnt too bad, makes the steering easier, and still seems to self correct, but you have to correct yourself coming out of corners, need to try a few things out to see exactly what is happening.
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Location:
Brisbane
Registered:
May 2004
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 03:32
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Yer, I know they are going to be hard to fit, but I'll order them first, then see whether lipping the guards will do, or I may even need some fibreglass replacement guards.
What's scrub radius? I've heard that term used before but never really understood it.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 04:40
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disadvantage?
much much greater load on bearings (since you are increasing the moment arm by which the cars weight acts on the bearings = bad)
stock may have the weight centred between bearings, and by moving that point outwards.....
increased self centreing effect from castor, and greater sensitivity to changes in road conditions (ie the tramlining)
meh, if it breaks, it breaks  just hope it is not at high speed when/if it happens...
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 04:59
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I'm about to find out all the bad points, having just put +0 offset rims on the back of my car
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 05:04
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back not so bad.. worst is the rim falls off the extra load on rear bearings will not be that much more.. it's the fronts you gotta be careful of.... or maybe i'm smokin the good stuff..
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Location:
Brisbane
Registered:
May 2004
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 05:21
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Interesting, so you say the castor effects the tramlining effect, I'm guessing there is some way to counter this then?
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 05:58
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| draven wrote on Sat, 30 April 2005 12:59 |
I'm about to find out all the bad points, having just put +0 offset rims on the back of my car
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+0's would be legal in WA and I think we have the strictest laws for rims, so I think you'll be fine.
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 06:06
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oh, legal absolutely.
just not sure whether I'll take out a bearing or some such, considering the sort of cornering I tend to do
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I supported Toymods
Location:
Australia
Registered:
November 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 08:09
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| draven wrote on Sat, 30 April 2005 14:06 |
oh, legal absolutely.
just not sure whether I'll take out a bearing or some such, considering the sort of cornering I tend to do
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Yeah, but the reason why I said its legal in WA, is that they have decided that you can only reduce the offest by max 12mm to be safe.
Any more and you'll be putting stress on bearings.
That said, the MA61 hub was setup for wheels ranging from +8 to +27mm offsets.
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Location:
Newcastle
Registered:
August 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 08:33
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Interesting.
I came in her about to ask the damn same question!!!!!
Say hypothetically, getting CBF or J-Blood flares on an ae86, and adjustments to make the wheels fill out the guards as much as possible, with just enough mm for clearance needed in suspension run..
The wheel weight being outside the axles if using wheel offset to achieve this; instead is it fesable making mofifications to the axle assemblies, to make that wider instead. Any suggestions on this one? What would need be done it so.
So ignoring the running tracks structural integrity for ht emoment.
How would it handle. Both in general race-line cornering or even drift? (Remembering that the sprinter is slightly wider at the rear, so the rear track would be slightly wider than the front).
Bad, good? etc etc????
So I gues in essence there are 2 questions, a general wider track; and a slightly narrower front track.
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I Supported Toymods
Location:
Sydney
Registered:
December 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 08:51
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I wouldn't go changing the front track without first consulting an engineer.
This is the problem as I see it.
Before the diagram is of any use to illustrate you must remember that the manufacturers of all vehicles work very hard to ensure the suspension geometry is such that the "tyre contact patch" (i.e. where the tyre contacts the road) stays in the same place whether the car is going straight or turning a corner.
Essentially the "tyre contact patch" is the pivot point for the whole setup.
Now if you were to move the tyre contact patch out a few inches from where it is supposed to be (due to incorrect offset) your contact patch will vary in an arc around the original contact patch thus it will not be constant throughout its range of movement.
As you now have a variable contact patch your steering is no longer linear as it should have been from factory.
The resultant "feel" you will get through the steering wheel is similar to if you had major play in your steering rack.
i.e. there will be a dead spot when you go to turn the steering wheel.
Now you "may" be able to correct some of this by altering caster/camber/toe settings.
If you change your front track by a large amount you may find that the problem can not be totally corrected in the limited range of alignment available from the factory setup.
Now although a lot of people will refer to this "dead spot" as "bump steer" but I do not believe that is correct.
Bump steer is usually caused by poor wheel alignment, usually major toe problems (toe in or toe out).
What happens is that if one wheel loses grip from the road momentarily (e.g. because of a bump in the road) the car will start to turn by itself.
Imagine that you have a toe out problem
i.e. your front wheels look like this \ /
If your left wheel loses contact from the road then the car will start moving towards the right.
If the right wheel lost contact from the road the car will move to the left.
The inverse will be true if you have a toe in problem.
i.e. your front wheels look like this / \
If anyone knows the technical term for a "dead spot" caused by an altered front track please post up (/me looks towards norbie)
Also I am not an alignment expert so I may have oversimplified the problem or even be totally misinformed, however, if I were considering changing my front track I would definately want to talk to a good engineer about the possible issue I have mentioned above.
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Location:
Brisbane
Registered:
May 2002
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Location:
Brisbane
Registered:
May 2004
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 13:25
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Thanks Wilbo, that site was very helpful, it expands on your diagram Toobs.
Ok, so now we see that these wider tyres will give me increased load on my wheel bearings, increased scrub radius (which causes tramlining, reduced directional stability). It appears that adding some positive castor will help the wheel return to straight ahead after a corner. I'm guessing this means that as more negetive CAMBER that is added directional stability is further reduced, so maybe I should leave that as is.
Now two questions... How do I increase castor? And also, to answer no_tofu_speed's question (and to make me feel a little better ), what are the advantages?
Thanks heaps for your help.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 13:31
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| Quote: |
A large amount of scrub radius can cause severe shimmy after hitting a bump. Four-wheel-drive vehicles with large tires use a steering damper to compensate for an increased scrub radius. Scrub radius is not directly measurable by the conventional methods.
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scary...
increase castor? either move bottom of strut forwards, or top of strut backwards, each 10mm is about 1 deg change...
the more casotr you have, the more you notice the difference between the castor on each side.
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Location:
Hobart, Tas
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 13:31
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Just to keep this discussion going - what are the handling effects of having a wider track (from stock) at the back than the front, either by increasing the offset of the rear wheels or decreasing the offset of the front wheels?
More specifically, the rims I will be fitting to clear my break upgrade at the front have a slightly more +ve offset. I have the choice of selecting rear rims to also narrow the track by the same amount, or keeping them close to stock.
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I supported Toymods
Location:
melbourne
Registered:
June 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 13:49
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in general, having the rear track narrower than the front will tend to induce oversteer.
and its brake, not break.
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Location:
Hobart, Tas
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 14:10
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Thanks. So I assume that the inverse holds - increasing rear track will increase a tendency to understeer.
That was a typo from being tired, not ignorance or an americanism 
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 14:25
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think of it this way... if you had a three wheeler, would it corner better with two wheels at the front or the back?
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Location:
Hobart, Tas
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 15:02
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| oldcorollas wrote on Sun, 01 May 2005 00:25 |
think of it this way... if you had a three wheeler, would it corner better with two wheels at the front or the back?
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Depends on whether it was fwd or rwd etc, and lots of other things. The analogy is too general for me to understand what you're getting at - do you have another one?
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: increases in track width -good / bad?
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Sat, 30 April 2005 16:34
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well that's a plus at least - I've increased my rear track minimally, and decreased my front track even more minimally (about 3mm a side), which should, in theory, help to curb the ma61's tail happiness a teensy bit (which is what I'm after)
I won't be able to comment on other effects of grip, due to a massively improved rubber compound (no even comparison).
but very helpful information... I plan to take my car to a suspension specialist to get my camber, castor and toe-in altered to whatever is best for my current setup (my suspension geometry understanding is fairly rudimentary, so I don't want to go playing around with that myself)
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Location:
Finland
Registered:
November 2002
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Re: increases in track width -good / bad?
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Tue, 03 May 2005 11:17
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I tried effects of alternated scrub radius by playing with rims.
Conclusion: with rims that wide the track, steering felt un-sharp and sloppy compared to original setup, not by much thou. Of course there were some increased tramlining also. I'm not conserned about bearing issues after watched rally cars. Most cars here use offset of +10 to -10 and these cars dont have issues after long jumps and coarse competitions... My friend has AE86 rallycar and I have been maintenance man for him.
and with Saab rims (ET45) car was very VERY weird!!! It was going all over the place. Like when you were driving 80kmh car went straight (occasionally) and all the sudden steering wheel shooted to extreme position or allmost atleast. I'm not going to test Saab rims anymore, It felt that dangerous. My two friends have reported about same symptoms with Saab rims. Cars were my TT132 Corona, TA40 Carina and 180B sss Datsun.
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Location:
Adelaide
Registered:
May 2003
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Re: increases in track width -good / bad?
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Tue, 03 May 2005 11:29
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Simple note, most cars will have a wider rear track than front track. 86 is no exception. Manufacturers consider it safer to oversteer than understeer in RWD cars.
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Banned user
Location:
ADELAIDE - The Drift City
Registered:
July 2002
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Re: increases in track width -good / bad?
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Tue, 03 May 2005 11:56
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other way roundf buddy... manufactures consider it safer to dial in natural understeer rather then over steer... its to cater for the idiot factor as its much easier to control under then over!
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I supported Toymods
Location:
Epping, Sydney
Registered:
May 2002
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Re: increases in track width -good / bad?
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Tue, 03 May 2005 12:05
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interesting... ma61 has wider rear track, but is still a tail happy little slut, hence me going for an even wider rear track
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