Just picked up some 911 front suspension. A arms, torsion bars, rack, sway bar, droplinks and adjustable koni struts. Didn't have the callipers though and the spacing is 3.5 inches. The guy reckoned they were from a 911S and need the aluminium callipers...anyone know if I want "A" or "M" or what?

(Did a search and it wasn't very conclusive)

One other thing the hubs seem to have some corrosion in some places where the magnesium? looks kind of flaked, is this common?

"A" calipers are 3.5. M calipers are 3.0 . A calipers will work fine with your 914. Make sure your measuring center hole to center. Otherwise you may think you have 3.5 when you really have 3. As for the corrosion I have seen that on alot of hubs. Some get pretty nasty.

here ya go: Lotsa Brake Information Page

i've seen the corrosion too - it's just aluminum. it wasn't present on the hubs i'm using now, and i don't know if i'll put the affected ones back inservice (they're the backups to the spares...). i note that new production 7075-alloy aluminum hubs are available that are much harder and more durable (it says here on the 'product information' sheet...)

you can use 'S' or 'A' calipers - the 'A' caliper is basically a cast-iron 'S' caliper. i believe you can also bolt up 917-esque calipers from 2nd-gen Turbo's if you've got huge HP and lotsa money... i think the ubiquitous Brembo 'Big Red' calipers also use 3.5" spacing (but don't quote me on that) and i believe also require different hubs and disks and such.

Wow cheers guys -Thanks for that link to the Pelican summary of callipers. I've heard the aluminium S callipers, although lighter, have problems with corrosion and flexing? Anybody know if this is true? I'm thinking that the iron callipers might be in more plentiful supply and stiffer.

I have A calipers, If I was to go with a bigger caliper, I would go with a 951 caliper. 300-400 bucks.

http://cgi.ebay.com/ebaymotors/ws/eBayISAP...&category=33563

Andrew, again.. errr

I haven't really checked yet but I'm guessing that the Konis are internally adjustable as I can't see any knobs anywhere. It has markings on the side with an arrow indicating which way "harder" is.
Any one know how and what a good setting is? I will run it with the stock 911 bulkhead sway bar and 911 TBs.

corrosion is a potential problem, realized by people who don't change their brake fluid but every ten or 20 years. keep it fresh and it's not a factor. i'd probably try to minimise their exposure to road salt but i think it's internal corrosion that's the big deal.

i've heard of people who could feel the calipers flexing, mostly in serious track settings, but i never could. it was academic in my case - i bought 'S' calipers before there -was- an A caliper to compare it to, and i expect i'll run them a good long while (they were original fitment to the 911E i'm driving now).

Porsche discontinued the 'S' caliper despite the appeal of low unsprung weight when they determined the variations in tire weight among the factory-approved models was greater than the caliper weight difference.

skipping ahead a bit - a good setting for Konis is the softest that will keep the suspension in good control, accounting for wear in the damper. they're pretty easy to set - jack and support the corner, remove the roadwheel, loosen the top strut nut, compress the actuating rod fully, and you should feel the 'claw' engage the foot valve. i'd probably exercise the valve from side to side to see where you are, first, then adjust somewhere soft of the middle, or adjust relative to your current setting preference.

i found it useful to use the hydraulic jack under the A-Arm to raise the actuating lever back up through the top nut.

If you are using 3.2 Carrera discs, the Ate 4 piston caliper off the front of BMW 733 or 735 will bolt straight on.

Howard, What kinda M/C do you use with those....I have the 19mm and dont really want to change it. I'm guessing you need a 23mm for the 4 pots?

I've used both A & S calipers....different cars, but same MC & rear calipers. The S do flex.....but damn, they're light.

Both external and internal corrosion can be a problem.....but damn, they're light.

I have no problems with them.....cept they're a bitch to bleed....light, tho

I use a 23mm master cylinder, but the car has Girling 4 spots on the rear as well. I could get away with a 21 and may do it sometine soon. I think it would give a little bit more feel.

Do you know how many degrees or complete turns required to move from full hard to full soft?
The shocks are off the car and when fully depressing the unit I rotated the rod 3 times before reversing the direction...doesn't seem to be doing much? Will one definitely recognize when its engaged?
When you say "claw" that seems to indicate that the rod needs to be lined up to engage...unless its a splined end or something.

it's been -so- long that i went to Koni's Site and looked it up. and amazingly, what i remembered was in fact right - they call for 5 half-turns of total adjustment. they had this cool picture of what's going on inside the damper, too...



i was eventually able to tell when the claw engaged. yes - it engages in only two positions, half-a-turn apart.

good luck. i have some loose dampers here i can play with, but i remember it going pretty much just as advertised... Koni's site does have this note tho, for your consideration:

NOTE: Some shock absorbers include a bump rubber concealed under the dust cover and this must be removed prior to adjusting. Don’t forget to re-install.