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Captain Obvious

Steering Effort Differences Between Years

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So my local Z buddy @GGRIII got his 74 260Z on the road and we drove that to Zcon. During the short shake down testing, one of the things we noticed was that the steering effort was significantly lighter in his 260 compared to my 77 280. And then (thanks to other forum members @Zup and @wal280z ), I got the pleasure to drive a 240 and another 77 280 at Zcon for a larger sample size.

The steering effort was consistent, meaning that the 77 280 took way more steering effort than the earlier years. Now, some of this could be attributable to suspension mods and tire choice, but it's stark. Once you're moving, it's no big deal, but maneuvering in a parking lot at a crawl, the earlier years are waaaaay easier to steer than the 77. I don't know about 75 and 76 280s, but by the time they got to 77, it seems something had changed.

I took a look at the specs in the FSM's and according to the documentation, the alignment specs are pretty much the same. Maybe some minor tweaks to the right of the decimal places, but certainly nothing that would explain the difference. I was expecting some large change in caster or something, but no. It's the same.

Can anyone else confirm my findings? Anyone with seat time jumping back and forth between one of the late models and one of the early?

And if so, does anyone have an explanation? Is it just my imagination, or did something change?

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Did you look at tire width per car? That would make a big difference

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I have thought the same, Captain.  Having both I think it's the weight difference.  The steering wheel on my 240 also seems bigger which makes turning seem easier.  My $.02.

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agree with the steering wheel, I notice it seemed lighter with the 240 style. I attributed it to my tendency to turn by grabbing the spokes on the foam wheel (not wanted to damage the fragile foam covering). This is on a 75 280z

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My old ‘78’s steering was heavy at low speeds with the stock tire size.  

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It's not tire width as the 260's tires were even wider (and stickier) than what I have on my 280. I've got 195 "touring" tires, and the 260 has 205 "summer" tires. Point is, the 260 tires should be grabbier than mine both due to the compound and the width.

And I'm not sure about steering wheels... I'm running a wheel from the 1990 300ZX, but it's pretty much the same size as my original 280 steering wheel. Was there a change in wheel diameter from 240 to 280?

Also, I do believe that the weight went up over the years, but it's not by that much. Couple hundred pounds maybe? Not a big change in percent.

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Tire air pressure?  Probably have to swap wheels to be sure it's a car difference and not a tire/wheel difference.

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I don't think it's tire pressure. They were all within the same general range of "general use". No severely deflated mud bog tires were used for the eval.

So I was looking at the steering specs thinking that maybe I missed the most obvious answer... Maybe there was a change in the steering ratio over the years? Well it's hard to tell... The specs in the FSM's are all confused.

First, the spec for the number of turns lock-to-lock in 74 is given in both meters and feet. WTF is that all about?  :blink: And then in 75, they dropped the units for lock-to-lock (which is a good thing), but the number changed.

And then the spec for steering ratio changed in 75, going from 18 to 15. That would surely make a difference, right. But then in 77, it went back up to 18.

And I can't get any of the numbers to line up... If you have rack stroke, ratio, and turns lock-to-lock, you should be able to use any two to calculate the third. But none of them work out...

In 74, they said there were seven teeth on the pinion, and from that point forward, they stopped listing that spec. I've got pics of my pinion gear from when I had my rack all pulled apart, but it's hard to determine the number of teeth. It's clearly either six or seven....

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Yes, the steering racks are different, someone on hybrdZ measured the travel per revolution on both racks, and the 240 rack was a little faster. However, to me, that would mean that the 240 would have heavier steering, but the opposite is true.

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6 hours ago, Captain Obvious said:

.....and @wal280z ), I got the pleasure to drive .... another 77 280 at Zcon for a larger sample size.

The steering effort was consistent, meaning that the 77 280 took way more steering effort than the earlier years. Now, some of this could be attributable to suspension mods and tire choice, but it's stark. Once you're moving, it's no big deal, but maneuvering in a parking lot at a crawl, the earlier years are waaaaay easier to steer than the 77.

....Is it just my imagination, or did something change?

Awwwwww, did my car stress your biceps @Captain Obvious ?? LOL

Interesting topic. For the record, my specs for comparison, in case it is attributable.

Tires: Bridgestone RE-11, 205/50 R15, UTOG of 200 A A, tires mfr date of 2009 (maybe?) with approximately 60% wear at the time of testing at ZCon.

Larger front sway bar (although that should not effect the steering tension in a parking lot)

Lowering springs with KYB standard struts.

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All good information and reasons I am using the AZC Shortened steering knuckles along with the Silvermine Power Steering kit on my rebuilt 76 280Z rack.

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I only looked at the years in question on the rack specs and they are the same by FSM year.  But, maybe, as you found, you have a 15:1 (actually 15.8) instead of 18.

Here's 1976, and 1977.  Maybe you have a 76 rack.  I don't feel so wimpy anymore.  I assume the higher number is higher mechanical advantage?  Not sure. 

image.png

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Edited by Zed Head

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Are the steering knuckles the same length between these models. I wonder if they made the 280 cars have lower ratios to make the high speed steering less twitchy?

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17 hours ago, rturbo 930 said:

Yes, the steering racks are different, someone on hybrdZ measured the travel per revolution on both racks, and the 240 rack was a little faster. However, to me, that would mean that the 240 would have heavier steering, but the opposite is true.

Can you point me to that thread? Would be an interesting read. And I agree... Seems counterintuitive, and would like to read that.

 

15 hours ago, Zed Head said:

Here's 1976, and 1977.  Maybe you have a 76 rack.

Zed Head, My 77 manual says 18.0 ratio. Both .pdf and hard copy. Are you sure you were looking at the 77 manual?

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17 hours ago, wheee! said:

All good information and reasons I am using the AZC Shortened steering knuckles along with the Silvermine Power Steering kit on my rebuilt 76 280Z rack.

Exactly.

I was like all like T-Rex arms after driving Wayne's car at Zcon. Couldn't lift my elbows off my waist.  ROFLThankfully there's still enough range of motion at the elbow to get the drink high enough to sip.

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1 hour ago, Captain Obvious said:

Zed Head, My 77 manual says 18.0 ratio. Both .pdf and hard copy. Are you sure you were looking at the 77 manual?

I posted a picture of the 77 18:1 below the 76 15.8:1, in my post #13.   By "as you found", I meant what you found in the early FSM.  I was trying to say that maybe you have an earlier rack, 1976, with the 15.8:1 ratio.  1977 was a change year.

I wonder if the gear changes might show up on somebody's parts CD?  It's not shown in carpartsmanual.com.

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19 hours ago, rturbo 930 said:

Yes, the steering racks are different...

Different between contemporary-build market/models too.

EG 1970 FSM for north American market HLS30U models gives rack ratio as 17.8:1 whilst 'rest of the world' got 15.8:1 and the 432-R model got the 'quick' knuckles as stock equipment.

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4 hours ago, Captain Obvious said:

Can you point me to that thread? Would be an interesting read. And I agree... Seems counterintuitive, and would like to read that.

Here: http://forums.hybridz.org/topic/99017-240z-rack-into-280z/

240Z (1972) - 1.81" of travel per 360 deg of steering.

280Z (1976) - 1.5" of travel per 360 deg of steering

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13 minutes ago, rturbo 930 said:

Here: http://forums.hybridz.org/topic/99017-240z-rack-into-280z/

240Z (1972) - 1.81" of travel per 360 deg of steering.

280Z (1976) - 1.5" of travel per 360 deg of steering

Sorry but, with respect (you are usually a saint in this respect, rturbo 930), "240Z (1972)" is not refined enough for this discussion. As I've pointed out, North American market got a 'slow' steering rack ratio from the get-go, whilst other markets got a relatively 'quick' ratio during the same period.

Market and/or variant needs to be specified if any of this is to be accurate.  

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2 minutes ago, HS30-H said:

Sorry but, with respect (you are usually a saint in this respect, rturbo 930), "240Z (1972)" is not refined enough for this discussion. As I've pointed out, North American market got a 'slow' steering rack ratio from the get-go, whilst other markets got a relatively 'quick' ratio during the same period.

Market and/or variant needs to be specified if any of this is to be accurate.  

Apologies, that was copied from the other thread to make it easier to find the relevant info. But yes, both racks measured were from US cars.

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