Suspension advice needed

[John Coffey]

There are no bump stops on the 240Z control arms.

[EuroDat]

My bumpstops were missing. I think the PO removed them or they broke up and fell off, but not certain. It made for a harsh ride. It now has the urethane stops which are pretty hard but better than nothing. Next time Im doing anything with the suspension, Ill change over to the Fatcat bumpstops in the link above.

I have never seen bump stops on the control arms. Did that start on the 280zx?

Chas

[Zed Head]

Seems like there should be some serious engineering work in to the bump stops if they play such an important part in the suspension performance. Maybe there is for the stock Nissan stops. Their damping characteristics should, ideally, be matched to the shock and spring that they're used with. The common name may be misleading.

Edit - actually, I don't even see a "bump stop" on the Nissan stock suspension setup. Maybe they only come with the aftermarket shocks. It's kind of odd that a shock maker would require an extra ring of elastic material around the shaft of the shock to alter its performance or save it from damage, bit not supply it with the shock. Just saying that the whole "bump stop" thing is kind of confusing. Maybe the bump stops are an after-after-market fix.

http://www.carpartsmanual.com/datsunS30/DatsunZIndex/Axle/RearSuspension/tabid/1731/Default.aspx

Edit - I did find the "#3 - Bound Bumper Rubber" in the 1978 FSM Front Axle chapter. I've never seen one in person even though my front and rear suspensions appeared to be all original and still full of whatever fish-based oil they put in there. Seems weird that they could disappear without a trace. Still wondering...

Edited November 27, 2012 by Zed Head

[jmortensen]

I just threw away 4 factory stops off of a 280 that had the original struts. On that car they were attached to the boot. Didn't look close enough to see if it was one piece or if the boot was clamped to the bump stop. Bump stops aren't that critical on a stock height Z because it has a lot of suspension travel. When you lower the car and don't spring it stiff enough or if you have too much rebound damping, then they become pretty critical.

I picked up a Miata this spring and the thing was beating the wizz out of me on the freeway around here. Looked into it and saw that Miatas are sent out from the factory with a comparatively small amount of travel before they hit the bumpstops, and riding on the stops is considered normal. I understand that Minis are the same way. Not much of a newer car guy, but this is what I've been reading. Since my Miata has the factory Bilsteins, they tend to pack down and ride on the bumpstops because they have a bit more rebound damping than they should for the spring rate. The spring rate is pretty mild, and the car is pretty comfortable until you get on the part of the freeway where it is one concrete join after another. In that area, riding on the bump stops is like driving a jackhammer. The Miata forums is where I learned about FatCat and all the rest of the bumpstop info. I needed stops quick and so I ended up buying some Koni units and they were a lot better than stock, but from what I've read the FatCat units are better.

I would venture a guess that most people with Z's are running poly bumpstops out of an Energy Suspension kit. They have the advantage of being relatively short, so if you're sprung stiff enough to keep off of them that's probably a good thing. If not, then I think they are most likely a pretty bad choice. By the looks of it, Koni and FatCats are much softer and longer.

[John Coffey]

My 350Z used progressive bump stops in front as part of the spring rate. They engaged after about 1.5" of bump travel. Its a common practice on new cars.

[jmortensen]

Not just Miatas and Minis then. Funny thing is that the stock spring rate on my Miata is something like 120 in/lbs, and people go to spring rates north of 500 in/lbs and say that the ride quality improves dramatically. I was talking to a guy who has the same year Miata as me and he has 600 in/lb springs in the front and 400 in the rear with better valved shorter stroke shocks (like sectioning a strut). He described the stock suspension with its soft springs as a "pogo stick" and I have to agree wholeheartedly. He also said that his rides MUCH better than stock. I haven't ridden in his car but I've been in similarly modded Miatas and I would agree with that assessment of those cars as well.

Those FatCat bumpstops are more linear, and that's why they are supposed to be more comfortable. You're not literally bouncing off of them as you do the stock stops. Still the best option is to stop riding on the bumpstops if possible.

[Zed Head]

I just looked through the FatCat site, thanks for suggesting it. The Technical Data link under Bump Stop Kits is worth a click. My post would have been shorter if I had looked at it first. $100 to do all four corners doesn't seem too bad.

I tried to get some Jinba Ittai but the link was broken. Bummer.

[grannyknot]

UPDATE,

Finally got the front suspension off and this is what I have,

Front shock, Tokico Illumina T0BZ3015 (BZ3038) Front spring, Tokico 5020F (140 lbs)

Rear shock, Tokico Illumina TOBZ3016 (BZ3038) with a 1-7/8ths" spacer, Rear spring, 5020R (165)

Talked to Tokico today and they confirmed that this is the set up they sell for 70-74 240z and gave me the weight rating for the springs. So, I have the proper kit for the car, the springs are a lot less than the P/O told me and seem to be all most exactly what the European spring set were. Also, of the four shocks there was only 1/2 of a bump stop on the passenger side front. (urethane bump stop cut in half) the other 3 shocks had nothing in the way of bump stops.

So... obviously the bump stops were a major problem that will be fixed, bump travel probably isn't a lot because of the lowered ride height, and I guess I'm driving the car harder than I think I am : )

I'll start with installing the missing bump stops, if that solves the problem, great. If it doesn't then I guess I'm looking at stiffer springs to prevent me from hitting them in the first place, does that sound like a good plan?

Thanks ,

Chris

[John Coffey]

The front springs are progressive and have a "working rate" of 140 lb. in. The range is from 90 lb.in. to 150 lb. in. Most people do not like that front spring because a lot of dump travel is lost.

[Zed Head]

I screwed up way back when I said that I had 5020's for my 280Z. I have 5022's, which are the 280Z springs. Sorry for any confusion.

[grannyknot]

The front springs are progressive and have a "working rate" of 140 lb. in. The range is from 90 lb.in. to 150 lb. in. Most people do not like that front spring because a lot of dump travel is lost.

But John, my front and back springs don't have the usual progressive shape, tapered. Mine are a straight column springs 4.25" wide top to bottom and 11" tall, 11 coils. Can there be a softer and stiffer section of such a spring?

[LeonV]

But John, my front and back springs don't have the usual progressive shape, tapered. Mine are a straight column springs 4.25" wide top to bottom and 11" tall, 11 coils. Can there be a softer and stiffer section of such a spring?

Yes, if coil spacing is unequal when they're unloaded.