260DET

Agree with you totally Jon re your table of fitments. Right now I have 205 R tyres on 7" rims, would you believe, and am presently chasing some 8" rims so 225's can be fitted.

For hard use the high end of the manufacturers rim width recommendations seems to work best. With R tyres anyway. They sit flatter and don't get the edges rounded off as much.

Road or race? Makes a difference re seat height eg helmet. Anyway my race seat was fixed hard against the transmission tunnel to give sufficient elbow room against the door. Even then the armrest had to be removed.

For the 240 IIRC there were two types of 5 speeds. Up to mid 71 they had the close ratio box with a flanged output shaft. After that they had the wider ratio box with a recessed splined output shaft. So if your tailshaft has a bolt on flange at the front you have the earlier box. It does sound like your syncros are buggered. Depends on the general condition of the box as to if it would be worthwhile rebuilding or not. And there is only one real way of finding that out...........

Thought the following might be of interest, an extract from some comments by a Marc Sayer. Who is/was some sort of US Z guru? Anyway, here it is - "...yes it (a rear strut bar) is a good idea, as is a roll bar which is also tied into the rear strut brace. Cary mentioned the interior creaking, most every Z owner has seen the crack in the roof between the rear quarter windows and the hatch, up near the top of the hatch. This is where a factory seam is and the body flexes so much at this point that it cracks the lead filler the factory uses. You can hear the body flex at this point from inside the car, the plastic interior panels creak and squeak every time it happens. The reason for this is the car while stiff from the seat forward, and in the area of the rear strut towers, has a weak zone in between these two areas, and the seam that cracks is right in this weak zone (my emphasis). By tying the stiffer front zone to the stiffer (rear) strut tower area with your roll bar you will significantly stiffen the chassis in this area....." One man's opinion but makes sense to me. There is a bit more but two finger typing.......................

Agree with TimZ and the dreaded trauma bar syndrome. BTW is it really 2 degrees celsius where you are, right now its around 35 celsius and over 80% humidity here, at 9am I was sweatin like a pig. Think I'll move to somewhere cooler. Anyway, after some considerable research my all behind the driver half cage has been designed and is nearly finished. It has been specifically designed to minimumise rear end twist, as indicated by the Z squeaking rear plastic condition. So if it works I'll do some pics in due course, if it doesn't, well.......

Yes, bad lad Chris. Yes too, flat spotted tyres may be skimmed, someone I know used a large lathe at work to do that. On certain surfaces you can flat spot a tyre when the wheel locks up without making a noise eg on a very thin layer of sand over tarmac.

You make lots of sense. I too would look at heating and quenching to shrink the metal and so tighten it up. Maybe do a bit in the middle and see how it goes? Might be worth while to get a pro in to do that though, could be tricky and end up a mess.

Excellent display, David. Looks like you have solved the 'where can I fit this large ducting hose in' problem by using two smaller hoses each side.

Worst thing I ever did was to sell my Toyo Proxes. For the type( street legal) a bit darty on the road but not too bad, they all seem to dart a bit, quiet. For the track, they perform much better when they have worn down to at least half. Nice predictable grip, quite a soft tyre but will last well providing they are run in properly, thats important. Can take a fair bit of heat if you get that kind of weather.

I use Ultimates on the road and track but my brakes are upgraded and the fronts have ducted cooling. With stock brakes I'd guess you would want somthing able to stand higher temps. Talking of higher temps, I saw a pair of Ultimate pads the other day which had got so hot that all the paint had flaked away from the metal plates and while the brakes were still working, the pad material was looking very sick. On Hawk blacks, my single experience reaction was 'how can they sell this rubbish?' They screamed in use and ripped hell out of the rotors. There are far, far better racing pads around than those. Ferodo DS3000 compound are a pretty good dual use pad. Will take more heat than the Ultimates but are bloody expensive.

Ultimates are a good dual purpose pad and will take a fair bit of heat. Kind to rotors too.

Interesting about roll cages. With 250 - 300 springs the rear of my '77 creaks when reversing diagonally over spoon drains. My mate's Z has a 'behind the driver' half cage ie hoop, stays back to the strut towers and a strut bar. It does not creak and seems to turn in, particularly, better than mine. So I've designed a structural type half cage that will give protection and am building it now. Pics some time in the future, if it works that is. But it is the driver that really matters, still it is fun to 'improve' the car.

Mate, I know I'm not the best of drivers. You are absolutely right about investing in driving skills, probably the best race investment one can make. I rode with an instructor on a race track the other day, by my standards he braked late and deep into corners, trail braked and lent on to the front wheels to get turn in grip, lined it up, bang on the accelerator and out of there. Seemed like he would have been picking up at least a second per corner over me.

Well the material per unit cost will be low so there should be a decent margin there for you. So do it, providing you offer a big discount to the good people who frequent this dive, eerrr, forum.

Jeez, I'm not going to go bare with you. But I will bear with you, as I guess most others will too.

There is some merit in using progressives in a car that is used for ordinary and competition purposes. But compared with linear rate springs you would have to go up more in the spring rate.

Are you going to stiffen up the body eg with a roll cage? The heavier the springs the more your stock body will flex, and Z bodies are flexy. I'm in the process of striffening mine, with springs around 250 - 300 body flex was making it impossible to set the suspension up properly. I think, we'll see.

Doing a good job there, looks like it won't break in a hurry. Can't advise you on your roll cage but talking with people who have them in their cars won't do any harm. Get some names and recommendations.

What IMHO would look good and perform some function is some self adhering rubber strip, it may even be legal for a bumper. Nice strip that suits the car, not the daggy stuff.

Yes, wheel well side vents are functional and this has been known for some time. For example, the Austin Healy le Mans cars had huge vents there and they were built, what, in the 1950's?

Does the box look the same from the outside? Sounds like you have got a truck box now which would explain the low gearing. I'm pretty sure that Nissan used a similar looking box in some commercial vehicles.

What some do is take them to an electroplater and get them done in zinc. New car stuff is zinc plated, there are several different finishes available including black. Won't last forever but its economical.

Glad you all liked it. The roll cage info is being used in my new design half roll cage.

The site below has got some good stuff on various items and issues concerning competition and performance cars. For roll cages go to the Roll Cage Symposium, the other stuff is under Myths or Tech. And don't be put off by it being a BMW enthusiast's site, he seems to know what he is talking about. http://e30m3performance.com/index.html