e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[duracellttu]

Even the TCK DA rear shocks (Koni 8242-1009) only support up to 700#, not more than that.

The GC DA rear (Koni 8042-1134) can support up to ~1100#.

Thanks for that advice. I’ll look into GC. Is there a source that I can reference which shows different spring rate ranges for all the shocks out there?

[IamFODI]

Isn't there a rule of thumb that most dampers can reasonably accommodate spring rates 20-30 percent above or below what they're valved for?

[Obioban]

Isn't there a rule of thumb that most dampers can reasonably accommodate spring rates 20-30 percent above or below what they're valved for?

TCK says they’re good for 300-700. If they targeted 500, that would be 350-650 with a 30% variance 🤔

[duracellttu]

TCK says they’re good for 300-700. If they targeted 500, that would be 350-650 with a 30% variance 🤔

TCK did recommend 500# springs to me, but that throws off the whole flat ride attempt I’m making. So what you are stating makes more sense for the range. He says it’s rated to 700# but doesn’t have enough compression that high.

[timmo]

Thanks for that advice. I’ll look into GC. Is there a source that I can reference which shows different spring rate ranges for all the shocks out there?

I wish lol, I called up both GC and TCK because I'm trying to figure out what rates I can run for my kit.

I have a bit of a conundrum on my hands - I bought a GC DA kit used but the rear shocks appear to be the ones from TCK. I managed to get the build sheet from GC and the part numbers don't match.

Build Sheet:



What I actually got:



The thing is, the seller was a very nice and upfront guy, he said nothing was replaced and those were the rear shocks that came with the kit. I do give him the benefit of the doubt, because on the local forum he has a pic from when the kit was new, with the same shocks:



It's just a bit odd how if these rear shocks did truly come with the kit, why it doesn't match the original build sheet. I'm being a bit hopeful that somehow these TCK were revalved to accommodate higher spring rates. On mine, there are these two holes that appear to have been plug welded right above the compression adjusters, and I haven't seen that on any other pics of these shocks, so I'm hoping that is somehow part of the revalve process.



Regardless the pricing was such that even if these rear shocks are original TCK it was still well worth it. But since they can only accommodate 700# that would make it very hard to run flat ride, which would suck - I was hoping to keep the 440# front and bump the rears up to ~900-1000#.

[Tbonem3]

Don't forget, our rear springs' location means that they provide about 2/3rds their advertised rate, for our cars. So if a shock's limit is 700lbs, you could run 1000lb springs in the car.

The spring is inboard, but the damper connects to wheelhub.

Unless TCK and others are giving that 700lb limit at the control arm and not the damper (which would mean the damper can only control up to about 467lbs, which I doubt is the case).

[Obioban]

Tck is saying your can run up to a 700 lb spring, not a 700# wheel rate.

[timmo]

Don't forget, our rear springs' location means that they provide about 2/3rds their advertised rate, for our cars. So if a shock's limit is 700lbs, you could run 1000lb springs in the car.

The spring is inboard, but the damper connects to wheelhub.

Unless TCK and others are giving that 700lb limit at the control arm and not the damper (which would mean the damper can only control up to about 467lbs, which I doubt is the case).

When I was talking to TCK over the phone, from what I gathered this accounts for the motion ratio due to having the spring inboard. This is also reflected from TCK's website, where in the drop-down menu you can choose rear spring rates from 400# - 700#.

[mrgizmo04]

I would assume that they would quote it for every car based on suspension geometry of every car, i.e. for our cars since they are a "divorced" setup (spring doesnt sit over the shock), they would account for the wheel rate/leverage affect. I think rear rate is about .53 (I might be remembering incorrectly), so I doubt they would stack the washers in the shock to be originally valved for nearly 2x spring rate.

Sent from my SM-G950U using Tapatalk

[r4dr]

That's so bizarre, do you know if he bought it from a 3rd party dealer? Maybe the dealer put together a kit for him.

[timmo]

That's so bizarre, do you know if he bought it from a 3rd party dealer? Maybe the dealer put together a kit for him.

Yeah it's really odd - no, it was purchased directly from GC, the build sheet shows that it was shipped directly from GC to him. GC's view is that the kit was definitely pieced together, which obviously makes sense from their POV.

It's kind of crappy but aside from dynoing the shock, I guess I'll have to bump up the rear spring rate, maximize the stiffness on the adjusters, then see if it feels underdamped, to see if the rear shock was revalved or not

[maupineda]

Question for those with more experience and knowledge. I have a Z4M, and this car is particularly stiff, in all possible setups, even the OE suspension is overly stiff. I currently have H&R Coils, and the rear is rock hard, so I was thinking about getting TCK 400 rear springs, the front is ok, stiff but not jarring, the rear is particularly bad. Many swear by KW V3 and how it makes it the best of two works, but to be honest, when I see the spring rates, I don't think they will be much better. The good about TCK springs is they are linear, and this may be a good compromise for me. I don't track the car, so I don't care much about extreme flat cornering, but after a sporty drive I can enjoy as much as possible.

I don't know the rates of my setup, could not find anything online. These are the spings I am looking at. https://www.tcklineracing.com/webdoc...Details379.cfm

EDIT: I called H&R and they don't release their spring rates, but the rep did tell me the Coilover kit has the race spring, which are stiffer. so my idea of going to the TCK may work for me.

[Chas3n]

Was the first post hidden?

[T.J.]

Question for those with more experience and knowledge. I have a Z4M, and this car is particularly stiff, in all possible setups, even the OE suspension is overly stiff. I currently have H&R Coils, and the rear is rock hard, so I was thinking about getting TCK 400 rear springs, the front is ok, stiff but not jarring, the rear is particularly bad. Many swear by KW V3 and how it makes it the best of two works, but to be honest, when I see the spring rates, I don't think they will be much better. The good about TCK springs is they are linear, and this may be a good compromise for me. I don't track the car, so I don't care much about extreme flat cornering, but after a sporty drive I can enjoy as much as possible.

I don't know the rates of my setup, could not find anything online. These are the spings I am looking at. https://www.tcklineracing.com/webdoc...Details379.cfm

EDIT: I called H&R and they don't release their spring rates, but the rep did tell me the Coilover kit has the race spring, which are stiffer. so my idea of going to the TCK may work for me.

It’s probably the bump stiffness of the damper rather than the spring

[maupineda]

It’s probably the bump stiffness of the damper rather than the spring

That was the first thing I thought. But i have plenty of travel before hitting the bump stops.