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Discussion Starter #1
..was just thinking there over lunch, has anybody attempted to stiffen a 166?

it's a bit of a weakness in the cars.. i'm sure you're all familiar with the creaking from the door seals as you work your way across a big speed bump for instance, the creaking indicating that the whole body is twisting.

Apart from tidying up the car's handling, a stiffer body would also be quieter, and furthermore you'd imagine it would add to the car's longevity.

The first obvious option is the strut brace, though i'd imagine this would be of limited use as the car seems to twist quite a bit around the middle.


Another option would be a full brace underneath like this;

Cusco Press Release – Chassis Stiffening For 06-11 Honda Civic Si & Type R! | RPMWare

I wonder how feasible this would be..? (anybody got any pics of the 166 underside handy..? :) )


Also there's stiffening foam, which seems cheap, if a little messy;

How To


any thoughts..?
 

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Also there's stiffening foam, which seems cheap, if a little messy;

How To
I don't know how to judge this stat properly but it seems like a small improvement in flex over the body length:

a simple garage measurement yielded a stiffer chassis with a 1/4-inch front and 1/8-inch rear increase in frame to ground height as the car was jacked up at the front left, with a floor jack saddle height of 10.75-inches. Road testing the car also provided a noticeable difference, with less creaks going up driveways and a noticeably smoother ride over broken pavement.
and :D :

If you left any cable or wires in there, you can just forget about reaching them now.
 

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I've got to say that I probably wouldn't go for it myself.

The car will be loaded in torsion via the suspension. I do a lot of work with wheelchair accessible vehicles and one industry standard test involves loading the vehicle up to maximum permitted weight, then centre-punching four marks at opposite corners of the tailgate recess. You then measure diagonally across it and note the readings. You then jack the car up and rest the right hand front wheel and left hand rear wheel on 6" packers and measure the diagonals again, noting the difference. You have to be pretty accurate in the measurements - typically +/- 0.1mm, which means using an internal micrometer. You then make your modifications and repeat the tests to see what effect you've had.

In the case of the 166, you could probably measure cross sections along the body (say betwen the top of the right hand B pillar and the bottom of the left hand one). I guess you could also do the 4 door apertures if you were keen?

The problem is knowing what to do next to stiffen it. A roll cage would be favourite, but a bit extreme. Seam welding everything is also quite good (if you fancy stripping it to a bare shell)! I doubt the foam would work well after a while. It's just builders' foam. The first time you take the measurement, it will probably effect some sort of improvement. After a few thousand miles, I imagine the foam will be crushed locally at the points where the shell moves and you'll be back to your old 166 shell (but with a load of blocked drain holes)!

I'm deeply sceptical about aftermarket braces of the type shown in those links. If they're any good, they'll put quite big point loads into the sheet steel they're bolted to as it flexes. That could start fatigue cracks after a while. To be honest though, I don't think most of them are any good - especially ones with bends in them, they just bend a bit more! I also don't like the ones with big offsets on the ends - they'll just twist. If a bit of tube is going to be stiff, it needs to be loaded in pure tension (i.e. running down the length of the tube). Anything else and they're not that stiff.
 

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Discussion Starter #9
..Avocet i get everything you're saying (top post :thumbs: ) , but instinctively i kinda feel an X-type brace underneath would be a big help. It'd have to be fabricated especially of course, but that wouldn't be the end of the world. As you say the mounting points would be crucial, and could make or break the idea. I can't help thinking about those inboard jacking points at the front :) but off the top of my head i can't really remember what else is going on underneath....

@ken, all us 166ers have a can of silicone spray in the boot :)
 

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Ta. Before you go too far, it might be worth mocking something up and then trying the 150mm block test WITH ONE END OF EACH TUBE DISCONNECTED. So you'd make your X brace, fit each tube at one end and leave the other end loose. You can then take careful measurements from the free end of the tube to a nearby point on the chassis before the car is twisted, then put it on the 150mm blocks and do it again. That way, you'll get a good idea of how much movement there is under those conditions and whether it's worth putting the braces in those locations. I haven't seen the bottom of a 166, but I assume they have a transmission tunnel - which is usually the weakest bit in torsion.
 

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Discussion Starter #11
..thanks avocet, that's a good plan. I may be able to get her up on a ramp next month, so i'll have a look around and see how feasible it is from a mounting point of view...
 
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