Suspension Component Weights

[03whitegsr]

Thought this might be useful for anybody looking to get deep into suspension work on these cars (or E30 guys looking for 5-lug swap info that stumble through here).

Weights for individual components are from a 1998 318ti.

Trailing Arm (with E-brake Cable and mounting bushings) - 19lb 6oz
Rotor - 9lb 1oz
Hardware (ebrake pads and adjuster, dust shield, brake lines, small bolts, etc.) - 3lb 7oz
Caliper and bracket (with pads) -6lb 4oz
Wheel bearing and Hub - 5lb 10oz

Total per side - 43lb 12oz


I made an attempt at measuring the unsprung mass by holding the mounting positions while the other end was on the scale. I would estimate the unsprung weight to be about 39 pounds. Almost all of the weight is out on the wheel end.

[anassa]

Thanks! Good info, quick question though, I am assuming this is all stock for the '98 ti? I thought later year ti's came with vented front discs? Did this year have the vented or solid ones?

[mtlblue]

9lb rotor? for both maybe

[mike156]

This is the rear rotors. They are solid. I believe it's only vented on the fronts on the newer ti's? Either that or I swapped the cars up in my head that these came off of. These didn't come off my car, which is a '95. They came off a wrecked car, which I thought I saw '98 on the computer when we were looking them up.


mtlblue, it was on an accurate digital shipping scale. It's right. Realize the rotor includes a drum for the E-brake as well.

[mtlblue]

Ok then. i have some new ones lying around in storage, didnt recall them being so heavy. But then again, they are Brembo, drilled and slotted ;-) . Good thing i have some lightweight kosei wheels to slap on!

[mike156]

A 9lb rotor is pretty light, in reality. I think the rear vented rotors on my EVO are like 14-15 pounds and even the 2-piece aluminum hat aftermarket ones with thin wall rotors get it down to only ~11. The 1/4" thick drag rotors with aluminum hats are around 8 pounds for the EVO. They are larger in diameter of course.


17x8.5 Kosei K4R + 215/45/17 Hankook R-S3 = 38 pounds
I'll be going up to the 245/40/17 range after these wear out. Either RS-3s or if something comes out that is faster...

Edit:
Just did some research and some part design and even using an aluminum hat, the rotor is still going to be 8 pounds, although it would be 11.44" in diameter instead of 10.7". There aren't many off-the-shelf rotors under 11". Going scalloped and drilled would drop another pound and a half. Full on 1/4" scalloped drag brakes you could probably get down to 5.5 pounds.

I wouldn't be looking for drag brakes though. Just something with stock like capacity but lighter and at that point, it's going to be maybe 2 pounds lighter. There is some weight savings to be had by going to a fixed mount 2-pot billet aluminum caliper for the brakes and floating single pot billet aluminum hydraulic E-brake caliper, eliminating the drum E-brake items. In total, I think you could drop about 7.5 pounds a corner and maintain the stock braking capabilities. Might even be slightly better due to better airflow with the two piece hat setup and the larger diameter. Lots of work and expense for 15 pounds, but it is unsprung. Rotational inertia would probably be about equal due to the larger diameter.