Tyres and the Dyno

[ProVK]

Just after some information regarding what effect the following tyre comparisons has to dyno figures.

Worn Tyres Vs New Tyres ?

Soft Compound Vs Hard Compound ?

Low Profile Vs Tall Profile (Same overall Dia).

Last time i has my car was on the dyno it just had some 50% tread 225/60-15's on the rear, this time i have the choice of some brand new 225/60-15's or my other rims with worn and not real soft 235/40-18's.

I'm going back to the same dyno this week for a new tune now i have a new ECU and Injectors, i would like to try and keep the figures as comparable as possible, but i don't have access to the same tyres as i used last time, i really want to be able to see the difference the tune makes on the car, but i'm hoping the tyres don't either decrease or inflate the figures too much and hide the real difference.

What are peoples thoughts ?

[Big_Valven]

I would think that you need a fairly impressive engine to be getting any major wheelspin on the dyno, or it's not strapped down and operated right...

[duke5700]

It makes some difference but not much. I wouldnt worry about it.

[ProVK]

Its not the wheel spin that worries me.

[Martin_D]

Tyres can make a huge difference........

Here is a cutout from a magzine piece that some bozo tech bloke came up with -
"CONCLUSIONS
If it’s consistently big numbers on a dyno that you are chasing then look no further than cheap tyres with low traction ratings, in the shortest sidewall height, and widest possible footprint. While they might be terrible on the road, they will give you the biggest dyno bragging rights, and to some folks that surely is everything. Look at the dyno printout and notice that the red line, for the Nankang tyres traveled the shortest possible distance, there is a story there in itself, and shows why the hardest, slipperiest, and cheapest tyre is – when it comes to dyno readings – the very best!"

[awddynotodd]

I'd stick with the same profile/rim diameter if your trying to test against existing data.

The 18's could induce lower numbers due to the higher inertia as more weight is further out from the centre of the wheel, even with the same overall height as the 15" tyre combo.

[duke5700]

Is it really that much difference? back to back 19" rims running Pirelli's vs stock VX SS 17's with long ling burnout tyres made 3rwkw when I was trying to win dyno day.

[ProVK]

I'd stick with the same profile/rim diameter if your trying to test against existing data.

The 18's could induce lower numbers due to the higher inertia as more weight is further out from the centre of the wheel, even with the same overall height as the 15" tyre combo.

I'll probably stick with the 15's, hopefully the new tyres don't make too much of a difference, they are not fancy sticky ones, might just take the newness off the tyres on the way to the dyno.