Rear shocks for a 75, what's different than 74's?

[RetroSC]

I'm trying to go with Koni Classics on my 75, but it looks like they only make them for up to model year 74. Seems those would fit a 75 as I can't see any difference, but was there a change back there from 74 to 75's??

Bill

[Trackrash]

There should not be any difference in rear shock size from ~'73 through '88.

EDIT: after researching I should have said '74 to '86.

[RetroSC]

Originally Posted by Trackrash

There should not be any difference in rear shock size from ~'73 through '88.

That was my thought, but all catalogs break down the rears to 72-74, then 75-89. Trailing arms look the same, and I can't identify what would be different up top, but there's got to be something.

[Trackrash]

Originally Posted by RetroSC

That was my thought, but all catalogs break down the rears to 72-74, then 75-89. Trailing arms look the same, and I can't identify what would be different up top, but there's got to be something.

Yes, I am looking at the catalog, and indeed Koni makes a distintion between '72-'74 and later. I know that '72 and '73 were the last years with the steel trailing arms AND the longer rear shock. '74 would be the first year with the aluminum trailing arms. Not sure why '74 would be listed different than '75 on.

Unless '74 is unique and had a different bottom mount size bolt? When Porsche went to the aluminum trailing arms they also went from a 12mm bottom bolt to a 14mm bolt.

At any rate the old catalog I have lists '75 to '86 as the same shock.

Edit: Looking further, I see that Bilstein lists the same rear shock from '73 to 89. So go figure.

[Tyson Schmidt]

!975 was the year they went to 5mph bumper law, and i would suspect it also coincides with the bumper height being raised.

So it makes sense that '75-on would come with a slightly longer shock.

For our use, the '72-'74 should work just fine in later cars, as I don't think there are too many cars on the road anymore that are still running that crazy high U.S. ride height they came off the boat with.

There's a chance that the extended and compressed lengths are the same but have different length bump rubber.

[Otter74]

big bumpers on 911s came in 74, not 75. US Bumper law was 5mph front and 2.5mph rear for 1973, 5mph on both ends for 1974.

[Bill Verburg]

I know of 2 changes to the 911 rear suspension
'72 E-series relocated both the upper and lower shock mounts to eliminate a rear ward and inboard tilt of the shock

'74 G-series got alloy semi trailing arms

[RetroSC]

Originally Posted by Tyson Schmidt

!975 was the year they went to 5mph bumper law, and i would suspect it also coincides with the bumper height being raised.

So it makes sense that '75-on would come with a slightly longer shock.

For our use, the '72-'74 should work just fine in later cars, as I don't think there are too many cars on the road anymore that are still running that crazy high U.S. ride height they came off the boat with.

There's a chance that the extended and compressed lengths are the same but have different length bump rubber.

This makes the most sense to me, they raised the ride height in 75 on US cars, so maybe the shocks are just a tad longer. From what I can see everything else is the same, so it looks like I'm ok to order some Koni's spec'd for 74. Thanks all!

[Matt Monson]

I’ve got the full suspension from an 85 Carrera on my 74.

[Tyson Schmidt]

Originally Posted by Otter74

big bumpers on 911s came in 74, not 75. US Bumper law was 5mph front and 2.5mph rear for 1973, 5mph on both ends for 1974.

Crash bumper came in ‘74, with small bumperettes. In ‘75 they got the big bumperettes and the ride height raised. The big bumperettes I had believe were done to meet the increase from 2.5mph to 5 mph. Didn’t know the front and rear were different speeds on the ‘73, that’s odd.

But the point of my earlier post was about the bumper height law resulting in the raised ride height.

[Matt Monson]

Originally Posted by Tyson Schmidt

Crash bumper came in ‘74, with small bumperettes. In ‘75 they got the big bumperettes and the ride height raised. The big bumperettes I had believe were done to meet the increase from 2.5mph to 5 mph. Didn’t know the front and rear were different speeds on the ‘73, that’s odd.

But the point of my earlier post was about the bumper height law resulting in the raised ride height.

You are correct. 914 saw similar “evolution”, first with bumperettes for 73-74, and then the all new bumper in ‘75.

[Bill Verburg]

Raised ride height was for US '75-83

[group911@aol.co]

This is the correct answer which means in theory, you should use the 74 shock if you are lowering your car. Went around with the suppliers about this for a long time including our host. There really should be a footnote on the product page explaining it.
In the front, they dealt with it by adding the famous spacer on top of the strut which everyone says you have to remove when lowering your suspension.

Originally Posted by Tyson Schmidt

!975 was the year they went to 5mph bumper law, and i would suspect it also coincides with the bumper height being raised.

So it makes sense that '75-on would come with a slightly longer shock.

For our use, the '72-'74 should work just fine in later cars, as I don't think there are too many cars on the road anymore that are still running that crazy high U.S. ride height they came off the boat with.

There's a chance that the extended and compressed lengths are the same but have different length bump rubber.

[75 911s]

I should dig my woodhead shocks out from my 75 and see how long the bump stop is..I did have the 10mm spacers up front. They stopped using the spacers just a few years later though, I think maybe 81? So wonder if that changed the rear shock length at all...