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Front/rear track ratio
https://ausmini.com/forums/viewtopic.php?f=5&t=16406		 Page 1 of 2
Author:  smac [ Mon Feb 20, 2006 7:42 am ]
Post subject:  Front/rear track ratio
Front/rear track on a drum car is about 40mm difference.

Front/rear track on a standard disk car is about 30mm difference.

I just measured up my car sitting on metro disks and spacered drums and it was more like a 70mm difference.

I realise I need to space the rears more, but how much? Would square be better? Or just close to square. I can only assume the original design had a narrow rear for a reason...

This is an ex-race car and has HUGE rear arches...either they weren't filled by the wheels (what's the point?) or they ran a REALLY wide rear.

I have a set of 23mm spacers I could use on top of the spacered drums - that would bring me back close to a disk set-up.

Anyone else out there running metro vented disks, and if so, how is your rear set up? 8)
Author:  minstar [ Mon Feb 20, 2006 8:56 am ]
Post subject: 
Mate I am running the metro four pots at the front and spacered drums on the back no sure how spacered though and there is a marked difference between front and back. This is normal for Minis and is one reason for their great handling. How much is correct I am not sure I will check tonight.

Cheers

matt
Author:  smac [ Mon Feb 20, 2006 8:57 am ]
Post subject: 
umm...I already stated the stock figures 8)
Author:  fuzzy-hair-man [ Mon Feb 20, 2006 9:57 am ]
Post subject: 
I would be a bit cautious about putting spacers on top of spacer drums, I am guessing that there is a limit to how far the wheels can be spaced out safely (but I don't really know) besides spacers (not spacer drums) are illegal here in NSW anyway.

Maybe finding some drums with an increased space or different offset wheels for the rear would do it :?:

Why does a narrower rear help handling :?: (not saying it doesn't just wondering)
Author:  Sir Yun [ Tue Feb 28, 2006 3:20 am ]
Post subject: 
before i had spacered drums in the rear (after the 7.5 S disk setup had been put on) i found the handling to be not as good as when the car was on drums..put then stopping was a problem :)
the difference beween from and rear was huge ( much wider up front).

after fitting wide rear drums the handing became quite a bit more sorted
Author:  simon k [ Tue Feb 28, 2006 7:22 am ]
Post subject:  Re: Front/rear track ratio
smac wrote:
I just measured up my car sitting on metro disks and spacered drums and it was more like a 70mm difference.

Anyone else out there running metro vented disks, and if so, how is your rear set up? 8)


are you using the metro uprights? they usually recommend using mini uprights and fitting the metro callipers and rotors to them as the metro ones change the front end too much.... not sure how much but I know they say you need adjustable bottom arms to get the camber any where near negative which must mean that the top of the wheel is a long way out - therefore a much wider track
Author:  smac [ Tue Feb 28, 2006 8:14 am ]
Post subject: 
I'm not actually sure, as this set up was on a car I bought. I have no mini disk hub to compare them too - any easy way of spotting the difference?

Quite correct about needing longer bottom arms - otherwise positive camber is huge.
Author:  simon k [ Tue Feb 28, 2006 9:38 am ]
Post subject: 
smac wrote:
I'm not actually sure, as this set up was on a car I bought. I have no mini disk hub to compare them too - any easy way of spotting the difference?

Quite correct about needing longer bottom arms - otherwise positive camber is huge.


dunno - I've never actually seen one up close, but hopefully someone will give you a response... I know 13sec has metro brakes on his car, not sure about his uprights

it's a safe bet that if you have adjustable bottom arms that you have metro uprights. If you like, measure from the centre of the bottom balljoint pin (where the nut is right at the bottom of the upright) to the end of the arm - a standard mini arm is 201mm from the centre of the balljoint pin to the edge of the flat part of the long bolt type thingy that holds on to the rubbers and goes through the subframe
Author:  cush [ Tue Feb 28, 2006 9:55 am ]
Post subject: 
superb use of the word thingy, simon.. ;)


what would be the effect on handling by reducing/increase the difference in track front/rear


eg... making the track equal between front and rear...
Author:  awdmoke [ Tue Feb 28, 2006 10:01 am ]
Post subject: 
I believe the reduced rear track on FWD vehicles is to enhance stability so that the lighter rear end doesn't "break away". All modern vehicles (Camry etc) are designed this way.

Anyone have a more definative answer?
Author:  smac [ Tue Feb 28, 2006 10:13 am ]
Post subject: 
cush and awdmoke, that's exactly what I'm trying to establish! :lol:

I posted this same point on minimania as well, and the same thing happened there: people start going off on a tangent about front track width, front camber, etc etc - I have my front track dictated by the metro brakes and am not interested in putting spacers at the front (it's already yummy and wide). All I'm trying to establish is the possible negative effect of the increased difference between front and rear, and/or, is there value is trying to get toward an equal set-up.

awdmoke - if it's donwe on new cars to prevent the rear braking, that implies to me that if it could be controlled, it could promote turn-in? (as we know modern cars are built to do the 'safe' thing which is understeer rather than oversteer).

Sir Yun seems to have had the most relevant actual experience - where TOO much of a difference is a bad thing. I guess in the extreme it would promote roll.
Author:  fuzzy-hair-man [ Tue Feb 28, 2006 10:27 am ]
Post subject: 
awdmoke wrote:
I believe the reduced rear track on FWD vehicles is to enhance stability so that the lighter rear end doesn't "break away". All modern vehicles (Camry etc) are designed this way.

Anyone have a more definative answer?


I was thinking along those lines, After mulling it around a bit I think it would try to plant the outside back wheel as you are going around a corner giving the outside back wheel more weight and grip and lessening the tendency to slide.

Reasoning.... :oops: if you take a line between the front and back wheels on the outside of the turn this the line the car is trying to roll over if you draw a line at right angles to this this what has to be lifted in order to roll :?: With unequal track this line is further forward meaning on a front wheel drive(where weight is up front) it transfers more weight to the rear outside wheel :?: decreasing the tendency to slide or go into oversteer therefore increasing the difference in track further would give a tendency to understeer out of the corner :?: Decreasing the difference in track width would increase the tendency to oversteer. :?:

Kinda Cool if this is true cause it means that using different offset wheels and spare drums etc you can tune your cars handling characteristics :twisted:

/ end random probably wrong incomprehensible thoughs. :oops:
Author:  fuzzy-hair-man [ Tue Feb 28, 2006 10:35 am ]
Post subject: 
smac wrote:
Sir Yun seems to have had the most relevant actual experience - where TOO much of a difference is a bad thing. I guess in the extreme it would promote roll.


I think the tendency to roll would not be increased or decreased it still requires the same amount of Gs to lift the other side of the car IMO it changes where the weight is felt.

It would be easy enough to test the case of even track width.... get a drum braked mini and put spacer drums on the rear and keep the normal drums on the front and go and see what it does... carefully :shock:

I agree some of the guys running Metro disks setups should be able to tell us whether the tendency to understeer was increased.

<EDIT> has anyone driven those three wheeled things ie engine and two wheels up front and a single wheel at the back. :?: the tendency would be most pronounced there I would think. :?
Author:  awdmoke [ Tue Feb 28, 2006 10:36 am ]
Post subject: 
Here is something interesting I dug up.
Note that they are refering to the New MINI:

<edit> deleted this as it was misleading!

and this is well worth a read:
http://forums.corner-carvers.com/archive/index.php/t-7677.html
If you ignore the bits about Karts, it makes a lot of sense.
Author:  cush [ Tue Feb 28, 2006 10:59 am ]
Post subject: 
so is that saying that modern cars have more of a difference between front/rear track? and less tendency to understeer?
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