Welcome Guest 

Show/Hide Header

Welcome Guest, posting in this forum requires registration.

Pages: [1]
Author Topic: Tyre sizes
classictin-
ker
Newbie
Posts: 5
Permalink
classictinker
Post Tyre sizes
on: June 12, 2018, 20:40
Quote

Hi.

I just did quite a nice model for the front end then realized I had entered the wrong tyre size (185/60 13) but when I enter the correct size (205/60 13) it screws up the roll centre movement ๐Ÿ™

When I change the size from 185 to 205 everything is fine as the aspect ratio is automatically changed to 54 but when I correct it to 60 that's when the roll centre movement becomes horrid.

However when I look at the tyre spec (Yoko A048) it gives the tyre size as 190/580R13 and the 205/60 13 is only used as a reference size so which dimensions should I enter?

racingaspi-
rations.co-
m
Moderator
Posts: 103
Permalink
Racing Aspirations
Post Re: Tyre sizes
on: June 13, 2018, 19:47
Quote

Can you post the link to your model?

Huw

classictin-
ker
Newbie
Posts: 5
Permalink
classictinker
Post Re: Tyre sizes
on: June 14, 2018, 10:49
Quote

This is the link to the model https://www.racingaspirations.com/mods/klw36qmn/

Basically I want to build a 750F so using my "logic" the best way to learn how ti do that is to 1st build a class B Sports special based loosely around the "standard" Locost book chassis. The "logic" behind this approach is that it will allow me to gain experience of altering the suspension geometry (from a know acceptable starting point) so that I can experience 1st hand what difference it makes to the car when it's on the track rather than on the laptop screen.

My plan is to correct any errors introduced to the front geometry by lowering the ride hight (chassis) to 80mm and improve it, if possible/necessary, and also to have an independent rear oooerr madam ๐Ÿ™‚

At the moment I seem to have let myself become bogged down in roll centre migration instead of focusing on controlling castor change.

I changed the tyre size to 205/60-13 again and the report for the roll centre Y movement has gone wild again but I also downloaded the data and in excel it looks fine moving only 1mm with 2 degrees of roll and 5mm with 5 degrees of roll, so the problem may just be a glitch in the reporting software???

Since I mentioned caster control what would be a good camber change at say 5 degrees of roll?

And speaking of roll what amount should I be aiming for?

Those 2 questions are probably "how long is a piece of string" type questions but I'm just looking for a ball park type answer ๐Ÿ™‚

racingaspi-
rations.co-
m
Moderator
Posts: 103
Permalink
Racing Aspirations
Post Re: Tyre sizes
on: June 14, 2018, 11:02
Quote

Sorry, I canโ€™t access your model. Can you open it and change it to friends or public (press the single person icon above the model so it becomes two people or a globe)

Do you mean caster or camber? The calcs donโ€™t display caster at this time. I like running only a few degrees of caster as any more makes my wrists hurt, but some people prefer more feel so increasing the caster will achieve that.

2 - 4 degrees roll for a 750f car with downforce, although some run more roll and do better than I do. With my very stiff, high cpm setup, the car feels very compliant and I can take lots of curb - lack of power is my problem.

classictin-
ker
Newbie
Posts: 5
Permalink
classictinker
Post Re: Tyre sizes
on: June 14, 2018, 19:24
Quote

Hmmm seems like I've fixed the tyre size issue but now my top arms appear to explode for the fun of it lol.

Anyway the new model is here http://racingasp.com/klw36qmn

I was talking about camber earlier...I read through my post several times to make sure I hadn't written caster by mistake and still managed to miss the typo lol.

racingaspi-
rations.co-
m
Moderator
Posts: 103
Permalink
Racing Aspirations
Post Re: Tyre sizes
on: June 15, 2018, 19:24
Quote

Everyone loves those exploding control arms!

For my camber, I looked up what the manufacturer specified as the ideal camber to maximise grip. -2.5deg in my case (Yokos) and that was not easy to find. I then set about altering the geometry, so that the outside tyre would be around that figure during roll (and with a bit of droop). That seems to have worked well for me.

classictin-
ker
Newbie
Posts: 5
Permalink
classictinker
Post Re: Tyre sizes
on: June 18, 2018, 09:32
Quote

That seems like a much better approach to solving the problem...start at the end (were I want the geometry to end up mid corner) and work back from there lol.

Where you say "(and with a bit of droop)" do you mean you aim to have around -2.5 degrees of camber of the outside wheel AND some droop of that wheel at the same time? I'd always imagined that the outside wheel would be in bump while cornering due to weight transfer or do jacking forces course droop? Basically I suppose I'm asking what attitude I should put the model in to simulate cornering movement of the wheel...roll with bump, roll with droop or just roll???

Pages: [1]