Where to attach the straps when on a dyno? (rolling road)

[disquek]

I'm considering heading to the dyno to sort out some tuning.

But there isn't really a great place to strap to on the back of these cars. I'm curious how others have done it.

Thank you.
-Kyle

[elancoupe]

I had them wrap around the front crossmember with soft straps, it worked out fine.

[disquek]

That keeps the Elan from moving backward.

What keeps it from going forward?

I've dyno'd cars dozens of times, and they're always strapped down at both ends.

-Kyle

[Stevie-Heathie]

Two different rolling road tuners both put soft straps around the rear wishbones, which I was nervous about but it was absolutely fine.

Best
Steve
PS My 1967 S3 sailed through her annual MOT test yesterday without so much as an advisory )

[rgh0]

I have tied down on the front and rear wishbones with all my dyno testing . Do it on the inside ends of the rear not the middle as you can bend the tubes easily. You can also do on the outside ends but need to then angle in to the middle a little to clear the disks and tyres.

The angle down and the tension of the initial of the tie-downs affects the dyno reading significantly as it affects the tyre rolling losses. This contributes to a lot of the inaccuracy with rolling road dyno testing. Try to keep them as horizontal as possible to minimise the downwards force and when doing back to back testing of different setups which is what rolling road testing is really all about ensure you use the same tie down arrangement every time.

Dyno operators with worn / polished rollers tend to tie the car down heavily to stop tyre slippage on the rollers

cheers
Rohan