17 replies to this topic

[B1RMA]

I am in the process of changing a few things on my recently purchased VX. I am of the opinion (limited as it is) that the geo set up done by Guglielmi is spot on, so will putting 16 inch fronts alter what was set-up with the existing 17 inch wheels?

[CocoPops]

Depends on the rolling radius change, but possibly yes.

[B1RMA]

Depends on the rolling radius change, but possibly yes.

Thanks I guess there is a little so ill check out the comparison site I have.

[smiley]

(oem 2 channel) abs also does not like large difference, so try to get as close as possible to original with those 16".

 

[B1RMA]

(oem 2 channel) abs also does not like large difference, so try to get as close as possible to original with those 16".

 

At great expense I have bought a four channel ABS unit, all part of my upgrade plan.

[Nev]

BTW, I wouldn't completely assume the car was correctly geo'ed when you bought it, unless you have some recent evidence/proof.

 

[james_ly]

I swapped to 16" fronts a year ago and have no dodgy tyre wear and it definitely has more front end grip than the Bridgestones ever did.

[B1RMA]

BTW, I wouldn't completely assume the car was correctly geo'ed when you bought it, unless you have some recent evidence/proof.

 

I've got the invoice the previous owner gave with the service history, looks like the geo was done less than 500 miles ago.

Fitted the 4 channel ABS module just now which I bought secondhand from Junks on SELOC quick easy installation ABS light stayed on when started but went out as soon as I touched the brake pedal. Stooped the car started again ABS light went out so it seems all is sweet there.

Next step is to fit the Racelogic Traction Control unit.

Going back to geo settings, would it be an idea for me to pop along to a guy in Southampton who all the local Pistonheads guys rate very highly and get him to record my settings then after I've had the Spitfire toe links and fitted the TD wheels put on go back and ask him to replicate the settings? or have I got something wrong with my thinking.

 

For some reason the car I bought felt more precise than the other two cars I drove before buying it, despite being a complete newbie it just felt more precise.

[B1RMA]

I swapped to 16" fronts a year ago and have no dodgy tyre wear and it definitely has more front end grip than the Bridgestones ever did.

I'm hoping with all the upgrades I'm doing to the car I'll get slightly better handling although I have no complaints about the standard wheels and tyres apart from I don't like the look of the standard wheels that came with the car.

[TFD]

Changing tires/wheel combo should not alter your geo. The only thing that could change is the radius (maybe some ABS problems... switch it off. And your speedo is reading some mph off) and the total ride height due smaller tires.

 

This change in rideheight does not alter your geo arm (toelinks etc.) and therefore your geo should remain the same as with the previous tire/wheel combo.

 

You only alter the geo by changing the rideheight by shocksadjusment.

 

... and if you're not sure... spend the 60,- quid on a new geo and find out yourself.

 

Grtz,

D.

[Samwise]

I was under the impression (through what i've read and thinking about it logically) that changing almost anything to do with wheels/tyres will have atleast a small effect on Geo. Be it the size, width, offset, etc of the wheels or tyres unless you were going to be fitting the exact same size/width/offset wheel with the same spec tyres as at the end of the day anything that effects where or how the wheel sits on the ground is going to have an effect on the Geo settings either when the car is stationary or when it is in a corner.

[anz3001]

Technically it DOES affect geo, in reality it won't make a noticeable difference to the vast majority of us.

[vocky]

for whatever reason fitting the ats dtc wheels to mine screwed the tracking, was spot on with the standard type wheels and the geo was quite a way out after fitting them

[B1RMA]

I think I'll play it safe and go down and get it recorded on the machine and seek the owner of the set-ups best advice.

[TFD]

Technically it DOES affect geo, in reality it won't make a noticeable difference to the vast majority of us.

 

How does it affect geo? 

A geo contains adjustment for toe (toelinks), camber (camperplates) and caster (casterarms/plates). Then there is Ackerman as wel..

When changing to different wheels/tires, non of the above are altered. So technically nothing has changed and the geo should still be the same.

 

The driving experience and feel can be different with a different tire/wheel combo, but this is because of the combo, not the geo.

 

No bitchin'   just my understanding of things. If you can tell me why it does technically effect geo, please do so.

[Nev]

for whatever reason fitting the ats dtc wheels to mine screwed the tracking, was spot on with the standard type wheels and the geo was quite a way out after fitting them

 

Could be attributed to new tyres assuming your old wheels had worn tyres.

Edited by Nev, 19 June 2016 - 07:40 AM.

[B1RMA]

Hera are the figures that the website gave for my standard wheels and tyres and the replacement TD's with r888r's

 

Existing                                      New

Diameter 624.3mm                    601.4mm

Circumference 1961.3mm         1889.4mm

Poke 55.3mm                            55.3mm 

Inset 135.3mm                          135.3mm

Speedo error 0%                       3.81%

Reading at 30mph 30mph         31.14mph

Reading at 60mph 60mph         62.28mph

Ride height gain 0mm              -11.45mm

Arch gap loss 0mm                  -11.45mm

 

Edited by B1RMA, 19 June 2016 - 09:30 AM.

[Crabash]

Speedo on rear wheel anyway...... I would suggest if geo is out after putting new wheels/tyres on then it was before, perhaps you only felt it after because of the higher grip, sharper steering or whatever, as FLD says it defies logic and physics that the angle of the wishbones would change, only the ride height. However it may be the case that a new geo is required to extract the best from your new tyre dimensions.

Edited by Crabash, 19 June 2016 - 01:41 PM.