Testing weight distribution figure

[Highlandor]

Unlike all other GT games, GT7's weight distribution figure (the split between Fr and Rr i.e. 60/40 or 51/49) doesn't seem to be working as it should(?), or at least, as accurately as it has done in previous games.

So this was a bit confusing for me at first as it didn't change when taking weight off (stage 1-5 weight reduction) or adding weight, like with the MX5 '15 (110kgs) engine swap. So I did a couple of tests to try and get an idea of what the game was doing.

Tried googling it, and checking all the way back through the tuning forum, but couldn't see something specific for this(?), happy to be corrected.

I only had 3 cars that would go to full (stage 5) weight reduction, the idea was to see if there were any changes at each stage. For all 3 cars, at every stage the indicated Fr / Rr weight distribution didn't change, but the Stability and Rotational G figure were, so something was happening.



I then did a similar test (to the engine swap cars - see below) whereby I moved 200kgs of ballast one position at a time, from centre to the heavier end of the car (I was curious to see if the same thing happened with cars that have had weight reduction). But it didn't, it looks like the game is correct when using and moving ballast around, aslong as it's not an engine swapped car - but again, happy to be corrected.



So the Fr / Rr weight distribution figure changes when ballast is applied / moved around, but doesn't change when doing weight reduction?

I also did a very quick test whereby I added ballast back to the GTR and 918 to equal a previous 'stage' of weight reduction and see if there were any changes:

GTR got 192kgs, taking it back up to stage 2 (1479kgs) but I couldn't match the Stability or Rotational G whilst keeping within the range of the original Fr / Rr weight distribution (54/46).

However, doing the same thing to the 918, adding 184kgs (stage 2 @ 1422kgs), no match for the Stability but the Rotational G was a perfect match

0.63 & 1.18 / 1.22 / 1.38​

So, I think:

• Weight reduction doesn't show on a car's Fr / Rr figure, but something is happening according to Stability & Rotational G figures
• This doesn't seem to be the same for ballast, as using this shows a difference in the Fr / Rr figure, as expected
• Unless, you're using ballast on an engine swapped car then it's going to have the opposite affect (see below / post in engine swap thread)
• Even if you use ballast to to return a car to the exact correct weight and weight distribution, there's no guarantee the car will be exactly the same (Stability / Rotational G)
• I need to get out more yaaay, summers nearly here

Engine swap data from quick test, originally posted in engine swap thread but thought I'd add it to here as well as it also shows weird things with weight distribution in GT7. What's different about this is the engine swap cars (admittedly, only tested 3 of them), the Fr / Rr weight distribution should be worse on the engine swap cars because they have more weight going to the heavier end or the car. But they don't,



Smirnoff durability test incoming......

 

[bread82]

There could be some F/R weight distribution changes being hidden when doing weight reduction, but, even if the F/R distribution is correctly being preserved, you would definitely expect to see higher rotational G with a lighter car. Lighter cars corner better because of less lateral load transfer.

You might see balance changes too, as the tyres will now be on different parts of their grip curve due to less loading to begin with and also less load transfer during cornering, though this could have complex outcomes depending on the specifics of the suspension.

i.e. a car which understeers horribly when stock could see that understeer reduced when weight reduction is applied, as the poor front tyres are now not being overloaded as much.... but less load transfer could also benefit the rears, and ultimately it's the front to rear grip ratio that creates the under or oversteer.

Depending how GT models the weight reduction, the centre of gravity height could change too, further complicating things. A carbon fibre roof IRL would reduce weight and lower CG height.

 

[Highlandor]

There could be some F/R weight distribution changes being hidden when doing weight reduction, but, even if the F/R distribution is correctly being preserved, you would definitely expect to see higher rotational G with a lighter car. Lighter cars corner better because of less lateral load transfer.

Cool, many thanks for the reply and having a look.

Depending how GT models the weight reduction, the centre of gravity height could change too, further complicating things. A carbon fibre roof IRL would reduce weight and lower CG height.

Yeh, this 100%, it's weird how GT recognises it with the Stability and Rotational G figures but not the Fr / Rr weight balance.

I wondered about testing the Stability and Rotational G figures from different variables and seeing what turns up. I don't know if anyone has 'cracked' these yet (?) i.e. interpreting these into values for each or any of the different parts of the setup, or a setup as a whole.

I started to look into this, but it doesn't look like a rabbit hole, more like doing a Doug McClure and tunnelling to the centre of the earth.

It's weird/interesting how different parts of a setup impacts this, but then you see the rabbit hole and all hell break loose. Start chucking comfort tyres on the front, racing rear and vica versa and it all gets a bit silly.

But, if you limit your changes to say a single variable, or two, then that's when things start to get more interesting, but like I say, I imagine someone must've cracked this, or they're just not saying - if anyone knows(??)

You might see balance changes too, as the tyres will now be on different parts of their grip curve due to less loading to begin with and also less load transfer during cornering, though this could have complex outcomes depending on the specifics of the suspension.

i.e. a car which understeers horribly when stock could see that understeer reduced when weight reduction is applied, as the poor front tyres are now not being overloaded as much.... but less load transfer could also benefit the rears, and ultimately it's the front to rear grip ratio that creates the under or oversteer.

This is interesting.

I'm just a numbers guy, don't know anything about real life stuff, which, sooner or later (probably sooner) is going to mean the end for people like me in GT.

People like yourself, Greycap, Ode, GTI from diff thread, Eran etc etc I don't have any of this knowledge so have no idea how to interpret stuff like this either into the game, or get it out of the game.

I don't know, but I think I don't explain things very well sometimes and it probably seems like I'm trying to prove people wrong when it's actually the opposite and I'm just trying to turn the numbers I see into the knowledge people like you guys have (I think that's what happened in the spool diff thread - sorry ).

It's like seeing your post (last quote) I start thinking about the crazy GR1 Nissan LMP, things got very weird with this car, and I have no idea why, wold love it it someone could 'have a look'?

Don't suppose u have a stock one?