Kind of as the title mentions, newbie question.

I notice it seems the chain tensioners, whether on a modern bike or vintage machine use a non roller style wear block.

Is there a valid reason for the slide to be preferred over rollers?

I don't know , Maybe because trials bikes don't generally run @ high speeds and don't have the same suspension travel / speed of MX/ Enduro bikes ? 

 But we have had chain tensioners since the dawn of time , to help smooth the power transfer and increase traction ...

My Panda still have a roller type chain tensioner and this type is a bit bulkier and too needs maintaince as the roller bearing installed to the roller tensioner wears down depending the weather circumstances.

While the slide doesn't need any maintaince beside regularly control and a swap when necessary

You can run without them on most bikes.

Roller type tensioners have been used on trials bikes, but are more prone to damage which affects their function. This is avoided by using the slider type, which does the job adeqately.

I wouldn't dream of running a trials bike without a tensioner.

 Beta USA trials team manager has ridden the 4T ever since it came out as the rev 4. Always without the tensioner.

Considering he could presumably get one for nowt, I'd put that down to lazy bike prep

The dawn of time being the late Sixties as I recall ☺

See here for all parts of a roller type, as long as the roller is attached near the rim/tire it's at a relatively secure spot, as the roller does have it's height especially when using bearings.

 

 

Is the tensioners purpose to allow a slack chain to be used due to long travel suspension?

Yep that's the case as the sprocket and the swing axel are not at the same point instead a couple of centimeters away from each other there are different lengths between front and rear sprocket when the swing arm moves. This effect can be minimized by less suspension travel, less angled swing arm and less distance between swing axle and front sprocket.

Less moving parts, less to go wrong.......

Guys, thanks for the replies. The machine I have is a vintage OSSA MAR, so the rear travel is pretty short travel. As original it has a springloaded tensioner with rubber type material slide block.

Seems the slider style is still viable as they are used on modern machines also.

There is no law against using a roller. I've seen plenty of twinshocks with a roller on the tensioner arm instead of a slider. Whatever rocks your boat.

If the tensioners purpose is to to allow enough chain slack for use with long travel suspension, why aren't they fitted to MX and enduro bikes?