Scottish Elises

While I have the car in bits I plan to replace many suspension parts, I would rather fit Stainless steel screws to the suspension, should make things easier to remove in the future, is there any problem doing this, and what should I go for A2 or A4 stainless.

Thanks

Giles

Elisepart, seriously Lotus and Elise shop all do kits I think.

I would be absolutely sure that you're not going to cause accelerated corrosion (and I'm not saying you will, it's just the first question that pops into my mind when you talk about putting stainless stuff in the chassis).

I daresay someone cleverer than me about this stuff will advise.

GilesM wrote:While I have the car in bits I plan to replace many suspension parts, I would rather fit Stainless steel screws to the suspension, should make things easier to remove in the future, is there any problem doing this, and what should I go for A2 or A4 stainless.

Thanks

Giles

please tell me you are not talking about the bolts used on suspension parts?

Seriously, DO NOT use Stainless bolts on *any* part of the cars suspension, they are NOT up to the job, Stainless is nothing like the same as high tensile steel.

All the wishbone bolts are 8.8 grade, and some others are 10.9, you need to maintain this.

Also, using shiny BZP (Bright Zinc Plated) bolts can be problematic too as the plating process can make them brittle and thus more likely to fail, always by bolts from named source and that are designed for the application.

Only use OEM bolts in the suspension. Stainless bolts have different metallurgical properties that might make them unsuitable for use in the suspension.

The 8 top plinth bolts were uprated to the 10.8 grade at some point I believe. All the rest that are 8.8 grade are so for a reason and I wouldn't want to change them for a much harder (and more brittle) bolt without understanding a lot more about metallurgy and the stresses and strains on the bolts.

You can do what you like with clam and undertray fixings but not the suspension bolts.

I would order a complete set from Lotus and be happy that they are as new and the correct grades

As I think Simon S pointed out before you need to inspect or replace the top plinth bolts from time to time - I don't do that many track miles any more so I alternate between replacing them all one year and checking they are still torqued the next year - any under torqued suspension bolt needs to be discarded and replaced with new. In my limited experience these plinth bolts are the most likely to fail on track (must have seen it 5 times on S2s including my own). If you were racing or doing a lot of track days you really ought to check them after each event (and they are so cheap that you may as well simply discard and replace at that point).

Cheers,
Robin

[Simon beat me to it ]

Thanks guys, exactly what I wanted to know, I'll buy the proper lotus ones and a spare set.

robin wrote:[Simon beat me to it ]

(Again )

PS. it's 10.9 (not 10.8 ), there's a good chart on Wikipedia that covers this:

http://en.wikipedia.org/wiki/ASTM_F568M

LOL - well it was from memory and I am a software engineer so that's my excuse ....

I'm in the process of fitting a set purchased from EP. I replaced a single bolt and nut with ones from lotus last year and they were significantly more expensive. i.e. two bolts costing the same as an entire set. Having had both types of bolts next to each other they were difficult to distinguish from each other. The EP ones claim to be specific for the job so I should expect them to be ok. Interested to hear if you think otherwise.

EP ones will be fine, Geary uses a major bolt supplier for his stuff, they will be to spec.

the problem comes when smaller places buy checp std bolts, then have them plated to make them look nice, without considering the issues of Hydrogen embrittlement.

galvanic corrosion can occur when there are dissimilar metals present ..normally base metals (Anodic) and noble metals(cathodic)

as the connection brackets are aluminium alloy ...avoid zinc bases bolts or carbon steel and Magnesium alloys......stainless fine.

Grading of bolts 8.8 eg the 8 stands for 800MPa tensile stress and the .8 represents a ratio of the ratio of the Proof (or Yield ) stress

the shear stress is normally .6 of the tensile stress, sometimes less..

The ali bracket would be the item of concern as it is made of ali and would therefore have a lower yield stress value and subjected to pull out and bearing stress’s and would fail before the bolt.

Note the UTS and yield strength is not the same as the yield strength is located in the elastic region and UTS is usually higher, however is in the plastic region and so, it has been deformed and therefore failed, but not fractured.

in the engineering circles it is normally good pratice to over engineer that under engineer eg...if the calc's say 8.8 is acceptable great....then anything that is the same or high is okay....not the reverse

dirkpitt wrote:as the connection brackets are aluminium alloy

care to expand on this?

can't think of a single suspension bracket that's Ali?

nearest I can think of is the old S1 Ali uprights (that have the M10 plinth bolts into them)

I was about to ask a similar question. Mine are definately not Aluminium.

Interestingly I see the same problem but back to front. Aluminium alloy Nitron fittings corroding due to exposure to the bottom wishbone and top mount (although that one is better due to large washers). I've put that there corrosion prevention stuff in to try and abate the process.

Scuffers wrote:

dirkpitt wrote:as the connection brackets are aluminium alloy

care to expand on this?

can't think of a single suspension bracket that's Ali?

nearest I can think of is the old S1 Ali uprights (that have the M10 plinth bolts into them)

sorry im referring to the chassis frame itself..not the suspension bush end..but the bracket were the bolt goes through to allow to connect to the frame...im assuming is made of ali alloy ...however, i not sure if the rear suspension arms connect to the steel sub frame or not

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