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GRC, weight transfer and The effects of a LSD


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#1 NeilR

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Posted 26 January 2012 - 09:48

Looking at formula fords is an interesting exercise as they are a highly developed package free of aero loads. They are also free of the effects of an LSD, so can be considered 'pure' in the efforts to get the maximum from the tyres - they can also be considered boring after the first 2 laps, but that's a personal thing.
Anyway, the front geometric roll centre on one leading car is around 10 mm and the rear is around 100-120 mm. I assume the difference has some significance. What I am thinking is that the hig rear grc reduces the rate (as in time) of rear weight transfer, relative to the front, though I might have this back to front...it's late!
What Then would the effect be of adding a LSD to such a car. Would the reduced risk of spinning the inside tyre (tire for our us friends) with the LSD alter the need for a slow rear weight transfer?

Edited by NeilR, 26 January 2012 - 11:31.


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#2 NeilR

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Posted 28 January 2012 - 10:31

this is a good post to demonstrate that three glasses of claret after a how day's renovation and painting is not a good idea. Anyway I found my answer in part on the www: an LSD in an unspecified FF supposedly cut 1.5sec from a lap. Since I do not know the exact circumstances I am suspicious, but it would appear someone has tested it.

#3 Tony Matthews

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Posted 28 January 2012 - 18:18

this is a good post to demonstrate that three glasses of claret after a how day's renovation and painting is not a good idea. Anyway I found my answer in part on the www: an LSD in an unspecified FF supposedly cut 1.5sec from a lap. Since I do not know the exact circumstances I am suspicious, but it would appear someone has tested it.

Perhaps they tested it after three glasses of claret...

#4 Lee Nicolle

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Posted 28 January 2012 - 23:30

Really it is fairly obvious that a LSD will always make the car faster. As you can get on the throttle harder earlier. And under brakes you are less likely to lock one rear wheel.My one few laps in a FF 1600 at conservative pace and I could feel that it needed 'hooking up'
While they are doubtfull on an open wheeler because of their better weight distribution for mine a spool is the greatest thing out. Positive and simple.


#5 NeilR

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Posted 29 January 2012 - 01:02

Actually it has yet again lead me to question the validity of such information on the www. As always a pinch of salt is required, but yes it should make some difference. Thing is you want a consistent driver to test these things and then do a back to back on the same day. Hell I can vary 1.5 seconds just by myself.
Tony it was a damn fine shiraz...which does not combine well with an ipad.

#6 cheapracer

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Posted 29 January 2012 - 07:37

It must be a tough call setting up a FF, you need some forward tilt on the roll axis (higher rear RC than front) to get some feel and initial bite into the front tyre at turn in but the higher you go with the tilt the more you unload the inner rear and lose traction.

The time difference without LSD would certainly be dependent on how tight the track was, with chicanes becoming more prevalent I guess they notice a bit more wheelspin now than they did in era's past. No doubt the biggest loss is at the start line.

#7 NeilR

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Posted 29 January 2012 - 08:43

I guess it depends on the FF, kent or zetec.
Anyway points moot in that they are not legal.
Current setup seems to work well. They are obviously trying to get the front pointy and to get the back to come around.

#8 24gerrard

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Posted 04 February 2012 - 12:02

Really it is fairly obvious that a LSD will always make the car faster. As you can get on the throttle harder earlier. And under brakes you are less likely to lock one rear wheel.My one few laps in a FF 1600 at conservative pace and I could feel that it needed 'hooking up'
While they are doubtfull on an open wheeler because of their better weight distribution for mine a spool is the greatest thing out. Positive and simple.


A 'spool' is effectively No diff.
This only works well in a flexible chassis like a go kart or in a strait line like a dragster.
In an FF it produces high corner entry understeer and breakaway corner exit oversteer.
We used welded diffs for comparison when working up an hydrolic diff design we had for F1.
Model one tenth scale cars use 4x4 with spool diffs however, seems to work well in them.

#9 MatsNorway

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Posted 04 February 2012 - 12:08

Model one tenth scale cars use 4x4 with spool diffs however, seems to work well in them.


They have a lot of chassie flex and spool is not so common anymore due to the new oilfilled diffs.

I run it in my RC car and it works fine on tight tracks. gets too understeery on faster tracks. But my car is rather primitive.

Edited by MatsNorway, 04 February 2012 - 12:10.


#10 Lee Nicolle

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Posted 05 February 2012 - 00:46

A 'spool' is effectively No diff.
This only works well in a flexible chassis like a go kart or in a strait line like a dragster.
In an FF it produces high corner entry understeer and breakaway corner exit oversteer.
We used welded diffs for comparison when working up an hydrolic diff design we had for F1.
Model one tenth scale cars use 4x4 with spool diffs however, seems to work well in them.

A spool is used in most tintop categorys where legal world wide, circuit, drags, speedway,US Ovals off road. The ones not using them are generally back in the pack somewhere. And most of those cars are not flexible, and generally have plenty of power.
A proper open wheel or sports car with a transaxle are the exception and quite a few of those use them too.