Wheel slip on dyno

Hi all , i have a set of clayton rollers with a sport devices DAQ , it works really well most times but occasionally i get wheel slip when doing ramp runs or steady state which is really annoying . The car in question is a MK1 Escort with a YB cozzie motor T35 garret running Link monsoon , i think the problem is tyres , it has Toyo 888 semi slicks on 13 inch wheels , they are getting hot and are starting to leave rubber behind the car , i have tried different tyre pressures and this worked up to around the 320 hp mark then started slipping again , is it just the tyres are to small in width . We had a 417 bhp Saab 95 on yesterday and that held 500rpm solid at 1.8 bar boost . We use the same method of strapping for every car allowing it to climb the braked roller etc nd always use the same tyre pressure of 40 psi ..

Any ideas guys.

cheers Keith

Traction on a rolling road can be tricky with some cars. There are a variety of things you can try:

1. Try strapping the car down harder. It's important that you're strapping the car down and not backwards though (this is a really common mistake with rolling road dynos). The downside of this is that you'll end up with a lower power reading as a result.

2. You can try lowering the tyre pressure slightly to let the tyre deform more on the roller and increase the contact patch. you won't want to go too far here or you'll end up over heating the tyre and damaging it. I wouldn't suggest going below 30 but this may be enough to help you. Like my other suggestion, this will also result in a lower power reading.

3. Can you run the car in a higher gear to reduce the torque at the wheels? You may of course be limited by maximum roller speed.

Is it possible to try another tyre? I know of some teams that have dyno tyres specifically because they've suffered from this in the past using their race tyres. I've also seen people use big drums filled with water in the boot to add extra weight over the rear wheels instead of using people sitting in it.

The difference from the Saab to the Escort is the amount of weight over the driven wheels, the more weight there is the easier it is to get grip.

Thanks guys , yes all makes sense , i am getting bigger power cars all the time now so its that big learning curve time again . I will try strapping it down a bit at a time first and see if that sorts it out with the tyre pressures back @40psi. Dont have any other wheels for it either Chris but that did occur to me as well .

Thanks for your replies. Cheers Keith