I have read the great write up in the how to section on belt changing

my car is on 100k miles both the belts are perished do I need to change the tensioners as well ?

thanks

seems like you are spending a lot of time with your new car, which is a good thing plus I am sure you got some mechanical skills'

change both belts if you think they are worn/perished. . its always advisable to change tensioners as that's what keeps the belts running smooth in shape. if a tensioner wears out or seizes it will wear out or chew the belts you are going to change.

choice is yours -

+1

If you intend on keeping this car for some time, tensioners are always good to change when changing the belts.
It's good practice...

Usual issue is, these tensioners can be pretty pricey. What I have done is, inspect the ones on by seeing how smooth they spin. like an alternator, they should be able to spin with VERY little resistance.

I go through cars quite quickly so, I've been known to just... not bother with the tensioners. All tensioners are changed on my E28's new engine

Daz

I hand build mx5 s mk2/mk2.5 turn them into fast road cars

change most components from the 5 speed box to a r/s 6 speed one change the diff, suspension brakes

really most items including the trim

just love it

I am known on most of the mx5 forums for this