46 replies to this topic

[Spandex]

My VX had a full Geo performed by the previous owner shortly before I bought it earlier this year. This was done on the car as standard. It handles well especially on the road but on track it has a tendency to understeer when pressing on.

 

I am assuming this is due to the limitations of standard front tyres. These are quite old now and scrubbed pretty badly so I'm planning replace them with 195/45/17's (GY Eagle F1's)  

 

My question ?

 

Will this totally throw the Geo out and cause the replacement tyres to rapidly wear, potentially badly and/or unevenly ?

 

I genuinely don't understand the implications but am hoping a bit of extra and fresher rubber width is my solution as my budget is tight and i'm on at Snetterton on Thurs.

 

Any help appreciated.

[james_ly]

Nope, won't affect the geo, and yes will help the understeer a lot. One of the best mods IMO.

[Spandex]

Great. What pressure should they be run at ?

[james_ly]

How long is a piece of string... forum tradition is 24/26 PSI, which is what I use on AD08s (on track that's hot pressures so drop by about 4 PSI at start of track day)

[Tareim]

I find 24 psi too low and steering feels heavier, I tend to go 28/30

[turbo boy]

Hi Spendex, Great name by the way 😊. Also consider Continental 3's. Arguably better than Eagle F1's. I have a full as new set for sale in the sale column. Kind regards, Jon

[james_ly]

I find 24 psi too low and steering feels heavier, I tend to go 28/30

 

Interesting, mine are like teflon at that pressure car feels very nervous!  

[Spandex]

Hi Spendex, Great name by the way 😊. Also consider Continental 3's. Arguably better than Eagle F1's. I have a full as new set for sale in the sale column. Kind regards, Jon

 

Yep - heard they were good too, I've got my eye on a pair just for the front that I can use on track and am on a tight budget. Appreciate the thought though.

[Tareim]

 

I find 24 psi too low and steering feels heavier, I tend to go 28/30

 

Interesting, mine are like teflon at that pressure car feels very nervous!  

 

 

I can't say that it feels nervous to me but then again I prefer a more nimble/quick response to the steering so probably suits me well

[anz3001]

Nope, won't affect the geo, and yes will help the understeer a lot. One of the best mods IMO.

 

Splitting hairs but it does have a small affect on geo, not enough to cause any concern but the absolute readings would be different.

[chris_uk]

on the road i tend to use 26/28 cold pressures.. But on track they are not measured the same way, your target is a "hot" psi reading, the basic reason for this is that all tyres have an optimum working temperature.. because we dont know, or its harder to find out the temps, psi is used as a quicker method.. toyo r888's seemed to work well at about 30psi hot.. (what the equates to in temps i dont know). Usually, my method of working this out is start with 20/22 psi from cold and do 5/6 laps. Come in and read the psi.. i try aim for about 29psi all round to account for cooling on the last lap and the getting back to my spot. Just lower all the tyres until they hit 29 (or what ever your target is.) when you go back out do another 5/6 fast laps and re check.. usually it takes 1/2 a morning to get it somewhere close then i just leave it unless the weather changes a lot or it starts to feel different then i will recheck. Each tyre will have differeent operating temps, and different wall stiffnesses all account for various readings.. if you can try find out your optimal working temp range and take a push in tyre thermometer and read across the tyre. Then alter your pressures to suit. You could take it one step further and alter your cambers based from that info. I believe that you want no more than 10c between inner and outer temps.

[Spandex]

Useful advice chaps - thanks.

 

And just before I fit and test - should I expect any issues with ABS ? Rears are as standard, I'm just changing the fronts from the standard original Bridgestones to 195/45/17's.

 

[Nev]

To avoid issues with the ABS try and keep the same difference (i.e. delta %) in rolling circumference between the OEM front and rear tyres.

 

This is a useful online tool to achieve this: http://www.willtheyfit.com/

 

Edited by Nev, 05 September 2017 - 11:57 AM.

[Foxy]

What people often forget is that you are adjusting pressure in order to maintain the profile of the tyre and keep to contact patch and wall stiffness optimised.

 

I've had big issues with Cup 2s on the evora where starting with, and perhaps running at, too low a pressure damaged the tyre.

 

I was give two tips by Michelin's (ex F1) tech guy:

1. Start at target pressure and bleed air out.

2. Use a tyre chalk or tyre pen to put a mark around the shoulder of the tyre so you can see clearly how for over the sidewall the tyre is rolling.

 

The above will also help you understand if your geo setup is working.

 

Target pressures are unlikely to be far from the manufacturers recommended. IMO 24 is much too low for a hot pressure...but there are too many variables to be definitive. 

[james_ly]

Useful advice chaps - thanks.

 

And just before I fit and test - should I expect any issues with ABS ? Rears are as standard, I'm just changing the fronts from the standard original Bridgestones to 195/45/17's.

 

 

On track I'd unplug the ABS otherwise you'll scare yourself silly!  

[Spandex]

Ok, so I have read up a bit on this quickly. Seems that whilst wiring-in an ABS on/off switch or putting some in-line bullet connectors sounds like the way to go, I am assuming that if I can also live without the speedo the simplest way to do deactivate ABS temporarily is to remove fuse 22 ?

 

This wheel-tyre combo is just for track so I'm not bothered about having speedo. I'm happy to have ABS (and speedo) when I switch the wheels back to my road set-up, presumably by simply replacing the fuse ?

 

Anything I'm not aware of but should be ?

 

Incidentally, on the track days I've done with the OEM tyre/wheel combo the ABS wasn't overly intrusive..

[TheRealVXed]

Having run the goodyears for many years, and just switching to the contis, my experience on the same geo/pressure settings is that the goodyears are a much better tyre for the VX on track.  They are stickier from the outset and I have found the conti's to break away much sooner than the goodyears.  Next time around I will be going back to goodyears...

 

VXed 

[TheRealVXed]

Ok, so I have read up a bit on this quickly. Seems that whilst wiring-in an ABS on/off switch or putting some in-line bullet connectors sounds like the way to go, I am assuming that if I can also live without the speedo the simplest way to do deactivate ABS temporarily is to remove fuse 22 ?

 

This wheel-tyre combo is just for track so I'm not bothered about having speedo. I'm happy to have ABS (and speedo) when I switch the wheels back to my road set-up, presumably by simply replacing the fuse ?

 

Anything I'm not aware of but should be ?

 

Incidentally, on the track days I've done with the OEM tyre/wheel combo the ABS wasn't overly intrusive..

 

You clearly aren't braking hard enough

 

In all seriousness though, when you first trigger the ABS you'll know about it!  Mainly because you won't be able to slow the car down.  The ABS is pretty shocking in the VX 

[Foxy]

If you remove fuse 22 you will find that the car stalls at low speed. soon get used to it though.

 

 

[SteveA]

If you remove fuse 22 you will find that the car stalls at low speed. soon get used to it though.

 

 

 

Unless you knock it out of gear and blip the throttle before it stalls.