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Protecting bolt heads/nuts under the floor
jps - 17/5/21 at 08:56 AM

I'm wondering how - if at all - others have protected either bolt heads or bolt ends/nuts that are exposed underneath the floor? I don't have many, but will have some bolts for my seat subframes where either the bolt head, or the end of the bolt, with nut, will be exposed to the elements, and potentially to bumps and scrapes from speed bumps, stones in the road, enthusiatic approches to hump-back-bridges, etc...

I had considered drilling a suitable hole (so it could double as a washer), then bending into a 'U', some 2mm stainless to make some minature 'skid plates' which would at least give some protection against a frontal scrape, but am wondering if there are any ready made solutions?


r1_pete - 17/5/21 at 09:09 AM

How about putting the bolt in from the bottom and using dome nuts on the inside with a dab of loctite?


coyoteboy - 17/5/21 at 09:22 AM

https://www.ballisticfabrication.com/products/bolt-protector-spacer-38


nick205 - 17/5/21 at 09:23 AM

From memory the only ones I had ony my MK Indy were for the seats. I used socket cap (Allen head) bolts going up through the floor from underneath. I then popped some of those plastic nut covers over the Nyloc nuts inside the car (below the seats).

Other than that I made a point of not having any exposed nuts and bolts below the floor to avoid the risk of scraping or corrosion.

Nearly all tin tops these days have plastic engine under trays. A mechanic friend of mine says they're a PITA as most drivers have no idea they're there and consequently when the car is dropped off for service/repair the mechanic has to remove the under tray and fight with broken plastic and kanckered fixings. He's got to the point before of not being able to refit the tray and having to advise the customer. Invariably then dealing with a nowty customer asking for money off the invoice.


jps - 17/5/21 at 09:57 AM

quote:
Originally posted by r1_pete
How about putting the bolt in from the bottom and using dome nuts on the inside with a dab of loctite?


I can for some - and did think it was better to have the bolt head underneath than exposed thread and a nyloc, but with 4 of the bolts (under the 'bum' part of my GRP seat) I think it's unavoidable - there's just not space for anything more.

quote:
Originally posted by coyoteboy
https://www.ballisticfabrication.com/products/bolt-protector-spacer-38

That looks like a great solution - seemingly only sold in the USA - can't find any UK ones! I will keep Googling...

[Edited on 17/5/21 by jps]


coyoteboy - 17/5/21 at 10:15 AM

What sizes would people be interested in do you think?


jps - 17/5/21 at 10:53 AM

quote:
Originally posted by coyoteboy
What sizes would people be interested in do you think?


I'm looking at M8 myself, thinking about it I will have bolts securing the pedal box too - which I might as well protect too - so probably need about a dozen. They seem to be something people fit on off-roaders, where they're bolting skid guards, etc - so will have a look at our local Landrover place

[Edited on 17/5/21 by jps]


Mr Whippy - 17/5/21 at 05:16 PM

Could just use them to bolt on some plastic skids and give your floor a bit more protection.


loggyboy - 17/5/21 at 08:13 PM

Depending on how structural they are use dome head allen bolts.


steve m - 17/5/21 at 09:09 PM

Just run a xflow, for that underside self lubricating system


ReMan - 18/5/21 at 07:42 AM

Contraversial I know, but I would bother. Mine seats bolts are just ZP and are still not corroded after 15 years, but then I don't take it out in snow and salt?
And really you shouldn't be scraping the bottom too often...


Mr Whippy - 18/5/21 at 08:47 AM

Put it this way your sure going to know when the seat bolts hit the road


David Jenkins - 18/5/21 at 02:34 PM

quote:
Originally posted by steve m
Just run a xflow, for that underside self lubricating system




Oh, that's so true... even my local MOT inspector commented that nothing was going to get rusty under my car!


David Jenkins - 18/5/21 at 02:40 PM

I have to say that if you're concerned about the abrasion of bolt heads under the floor of the car then you have many other issues to think about...

I wouldn't expect the floor of the car to be closer than 1 cm from the road at any time. Mine will go over standard speed humps without problems, with the bottom of the bellhousing being the nearest thing to the floor. If that clears, I've got at least 5 cms floor clearance.

Using wide dome-head bolts with the heads downwards/threads upwards would help, if you are getting close.


jps - 18/5/21 at 04:09 PM

quote:
Originally posted by David Jenkins
I have to say that if you're concerned about the abrasion of bolt heads under the floor of the car then you have many other issues to think about...

I wouldn't expect the floor of the car to be closer than 1 cm from the road at any time. Mine will go over standard speed humps without problems, with the bottom of the bellhousing being the nearest thing to the floor. If that clears, I've got at least 5 cms floor clearance.

Using wide dome-head bolts with the heads downwards/threads upwards would help, if you are getting close.


Honestly -I would expect yes it's unlikely - but just trying to factor it in if I can.

Once built I would like to take the car into Europe at some point - and the ramps on those Chunnel carriages do seem a bit severe!


coyoteboy - 20/5/21 at 01:00 PM

quote:
Originally posted by David Jenkins
I have to say that if you're concerned about the abrasion of bolt heads under the floor of the car then you have many other issues to think about...

I wouldn't expect the floor of the car to be closer than 1 cm from the road at any time. Mine will go over standard speed humps without problems, with the bottom of the bellhousing being the nearest thing to the floor. If that clears, I've got at least 5 cms floor clearance.

Using wide dome-head bolts with the heads downwards/threads upwards would help, if you are getting close.


Totally depends on your car design I guess!


HowardB - 20/5/21 at 02:39 PM

quote:
Originally posted by jps
quote:
Originally posted by David Jenkins
I have to say that if you're concerned about the abrasion of bolt heads under the floor of the car then you have many other issues to think about...

I wouldn't expect the floor of the car to be closer than 1 cm from the road at any time. Mine will go over standard speed humps without problems, with the bottom of the bellhousing being the nearest thing to the floor. If that clears, I've got at least 5 cms floor clearance.

Using wide dome-head bolts with the heads downwards/threads upwards would help, if you are getting close.


Honestly -I would expect yes it's unlikely - but just trying to factor it in if I can.

Once built I would like to take the car into Europe at some point - and the ramps on those Chunnel carriages do seem a bit severe!




the local speedbumps catch the underside of my car! They are EVIL


coyoteboy - 20/5/21 at 05:02 PM

I think that they can legally be up to 125mm high.

My bone stock 370z bounces the chassis on short steep 100mm ones when taken slowly...