rivnuts or not?

[SteveH]

ive been trial fitting my seats recently and have decided im going to mount them on 25mm x 25mm tube thats welded to both chassis rails
my question is what would be the best or preferred method of fixing the seat runners to the tubes
do i drill straight through the tube and put crush tubes in and bolt all the way through the floor
or do i use m8 rivnuts and bolt them up that way
using the crush tubes would make it very solid indeed but does the roadster need to be like that

[RichardH]

i dont think rivnuts are up to the job, may not even be acceptable

[flyerncle]

Why not use 25x3mm flat bar across floor and weld to outer chassis and trans tunnel,25x25 may be a little too high.

[SteveH]

i did think about some 25mm flat bar but thought it might be a bit flimsy and maybe flex a bit

Originally Posted by flyerncle

Why not use 25x3mm flat bar across floor and weld to outer chassis and trans tunnel,25x25 may be a little too high.

[flyerncle]

Depends on what floor you have,but if fixed to side chassis rails and trans tunnel I would have thought it would be ok.

[SteveH]

my floor is 1.5mm aluminium

[voucht]

Hi,

I would not use rivnuts because in my opinion, they are way too weak to resist the constraints of a seat + a person, especially in case of a crash.

I think crush tubes are not necessary here. They are on high tightening torques only, and the torque you need to tighten M8 bolts to fit your seat is not high enough for you to need to put crush tubes in the 25x25 tubes the runners are fitted on in my opinion.

I did exactly like you want to do: 2 transversal 25x25 tubes welded to the chassis tubes. Seat runners are fitted with M8 bolts, washers and nylock nuts through these 25x25 tubes, and no crush tubes. So far so good!

Hope that will help

Good luck!