bluejae

i know there can be quite a few factors that can influence dyno numbers... and i was wondering if tires would play a big role in it...

i had dynos done on 2 different mustang dynos... during 2 different times of the year... july and april... and the hp/tq difference was approx. 30hp/30tq..

july mustang dyno#1 on good tires... 471/438

april mustang dyno#2 on nearly bald rear tires... 442/405

i'm just curious... i do have a tune on my car but i am very confident that the tune is still intact... i don't believe my car would be running as smooth as it is if it somehow revert back to a stock tune...

Mort

I am no dyno expert but I think tires can play a role in results. The tires can slip/spin on the rollers causing the revs to go up but the results to go down. This is probably especially true on a mustang dyno which places a load on the rollers to simulate real world conditions. It would take even greater traction between the rollers and tires to avoid a slip/spin of the tires on the rollers. My .02

Also your tune can not revert to stock unless someone replaces/flashes your tune with a stock tune.

BAD430BENZ

i can promise you that tires have a little something to do with dyno results . i am going to do a writeup on my Weistec monster and in it , you will see my dyno results . the dyno looks funny because the line dips every so often due to traction issues .

bluejae

you've got quite a different beast compared to my car...

Even Money

that's your problem right there, primarily different dyno. But that said, you should probably see a hp increase with bald tires, not a loss. less rubber on the tires, less weight to spin

BAD430BENZ

but easier chance to spin the tires . you are on a metal roller with bald tires . i know my car spun the tires

Dads C63

Tires WILL have an effect on the dyno numbers but you shouldn't compare dyno's, especially different times of the year when the temperature and humidity will also play a factor. There are many things that effect the cars performance that effects the dyno. If the car feels good then I wouldn't worry about it.

EkS

Wouldn't a bald tire act like a DR or slick at the track and give better traction?

PetroC63

Definitely not.

Even slicks have a certain amount on rubber on them.

EkS

Well I guess it depends on your definition of bald. My definition of bald on a street tire is no tread, no steel showing.

khmergod

I will be dynoing my car by end of year using semi new 275 PSS on the same dyno. My first dyno was on almost bald 255 conti 3.

4ramin

Tires for sure impact dyno numbers, I've tested 19 vs 18, sticky tires vs stock.
The best numbers come from stock 18's and none sticky tires. If tires are sticky they create more resistance on the rollers. I've seen as much as 30 rwhp loss with 19's and sticky tires vs stock ... All testing done on the same dyno .

ArthurJGuy

Tire pressure can change dyno numbers
Tire type can change dyno numbers (street, summer, DR, or slicks)

Bald tires are not anything like slicks, not due to the amount of rubber but due to the tread compound

What I think happened is the dyno at two different times of year. The dyno correction factor only corrects the results that it sees, it does NOT correct the cars performance from say denser air, more timing, fuel temperature or octane, etc. It's a half assed correction at best.

If you ask the dyno operator for the file (the actual file, not a printout) I can look at it in the software and tell you if it is slipping by the gear ratio table.

4ramin

remember how you strap the car down can also change numbers x pattern or straight. how hard you strap it can also change numbers. the point being made is DON'T bother too much with the dyno and just have fun with it