Mustang Owners Club Australia Forum
Technical & General Discussion Area => Tech Torque Pre 1973 => Topic started by: lukep6470 on May 09, 2022, 03:38:39 pm
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Hi,
I've had this car with RRS suspension for about 12 years now and I've finally decided to do something about the front springs. It's a 1967 coupe with a 347, alloy heads, power steering and AC. My issue is when you hit a small pothole or a bit of a lip of traffic calming it hits so hard you think you have broken the car as the fillings fall out of your teeth.
It currently has 275lb springs in it from RRS. What spring rate are other people using with this combo and what experience are you having?
Also has anyone taken a look at the shocks to see what part number they are? I am pretty sure they are KYB AGX using Google foo but that is as far as I could get without ripping the struts apart. I'm sure they are getting due to be replaced soon.
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Sorry off topic but can I ask how you have found the struts other than the spring rate? Do you have the power rack and pinion also? I bought this kit for my 65 maybe 10 or so years ago and have only just finished mock up and strip ready for paint with never having driven on them. I have heard the turning circle is not very good but interested to know. From my research, struts are basically VT Commodore spec.
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The hubs are absolutely VT Commodore, the car had what I think they call the phase 2 brakes on and I got some bigger brakes off a VZ SSV and once the rotors were drilled for the Ford bolt pattern all of it just bolted on. This gave me 320mm rotors that need 17" wheels to fit. The struts however seem to be completely custom as there is no way a 2.5"idx10"long spring will fit the front of a VT-VZ.
It has the full front end with the RHD rack power rack and while it does have a large turning circle compared to a modern car I had used it as a daily driver for about 5 years (I haven't needed to drive to work for years). A lot of people seem to blow the ends out of the rack with the wrong pressure power steering pump. Mine has the RRS supplied pump on it and the rack is still leak free 35000Ks and 12 years later.
I haven't driven a stock 67 Mustang to compare turning circles. I'll have to track one down at a cars and coffee or something and see if we can do a test with the 2 cars.
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Sorry off topic but can I ask how you have found the struts other than the spring rate? Do you have the power rack and pinion also? I bought this kit for my 65 maybe 10 or so years ago and have only just finished mock up and strip ready for paint with never having driven on them. I have heard the turning circle is not very good but interested to know. From my research, struts are basically VT Commodore spec.
Can you take a look at the springs and see what rate they are please? RRS are supposed to supply ones suited to your combination and ride preference. If they are similar to mine they will be QA1 springs with the length and rate written on them. Mine has 10-275 on them which means 10" long and 275lb spring rate.
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Hey Luke,
I think you need to see a professional.
It all depends on the front weight of your car, your travel compression and rebound, Shock or strut angle and dampening and rebound and how much you want it to compress and what the bump stops are if any.
You probably need something over 500lb/in.
Cheers Phil.
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Hey Dan,
This is how I worked out the rear spring rates on my car.
Car weight,
Total, 1500kg / 3300lbs
Rear, 860kg / 1900lbs (need to minus unsprung weight, about 300lb)
1900 minus 300 = 1600lbs. X .8 for spring angle = 1280lbs.
Divid that by 2 = 640lb, so with 400lb springs should move 1.6”
Then I set the Shock height on the axle and screwed the Shock spring to give desired preload and desired road height.
With that I have my AVO coil overs 14 clicks into 22 full clicks.
I haven’t changed weight into dynamic force, that’s where you need a professional.
Cheers Phil.
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Hey Luke,
I think you need to see a professional.
It all depends on the front weight of your car, your travel compression and rebound, Shock or strut angle and dampening and rebound and how much you want it to compress and what the bump stops are if any.
You probably need something over 500lb/in.
Cheers Phil.
Hi, thanks for the info, I think you misunderstood I am looking for a more comfortable ride :smile01: It currently has 275lb springs which I reckon the PO got from RRS as a "more race car" ride.
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Hi, thanks for the info, I think you misunderstood I am looking for a more comfortable ride :smile01: It currently has 275lb springs which I reckon the PO got from RRS as a "more race car" ride.
Hey Dan,
Sorry I misunderstood you, I was thinking the struts were bottoming out.
With the struts, have they adjustable. (Compression and Rebound)
Standing beside the car and pushing down on the fenders does it seem stiff or soft.
Cheers Phil.
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Real stiff, the adjustment on the shocks doesn't seem to make any difference to the severity of the hit that's why I now think it is the springs. The bump doesn't have to be anywhere near big enough to bottom out the springs.
That's why I was wondering if maybe RRS are now shipping the struts with different rate springs on them. Mine is apparently one of the first installs.
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Hey Luke,
What’s the road height of the car, could the springs be wound up tight against the stops and you have zero preload.
If so you car would be very high at the front.
Cheers Phil.
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I swapped in Gabriels, which are softer and I've found them much more comfortable, and IMO better for the car
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Hey mate, are the Gabriel's the classic shock?
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Hey Luke,
What’s the road height of the car, could the springs be wound up tight against the stops and you have zero preload.
If so you car would be very high at the front.
Cheers Phil.
No it is lowered at the front by an inch or so. If you go over a speed bump slowly it does move up and down as expected. It's when you hit a small sharp bump at speed that it really thumps.
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275lbs doesn't sound like a stiff front spring to me.
If they are stiff then they surely won't be bottoming out on small bumps. I think more likely the dampening of your shocks is way too firm, preventing the springs from doing their job properly and so the front end is crashing into bumps rather than reacting and absorbing them.
I have a '67 FB. When I restored it many years ago I installed KYB shocks, seemed to be pretty much a standard catalog item that everyone used.
But on the FB I thought them too firm, the front end seemed too unyielding over bumps, so eventually I swapped in Gabriels, which are softer and I've found them much more comfortable, and IMO better for the car too.
Trial and error to some extent isn't it?
My 2c worth anyway.
Interesting as I think these are KYB AGX adjustable strut inserts. There appears to be little difference between the hardest and softest settings. I'd love to get the part number without pulling the car apart.
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Hey Luke,
Sorry to say but it seems it Time to pull the springs off and check the struts.
I’ve got to apologise about saying 275Lb/in not very stiff, being a strut there is no overhang so 275 or less would be correct.
Cheers Phil.
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Can you take a look at the springs and see what rate they are please? RRS are supposed to supply ones suited to your combination and ride preference. If they are similar to mine they will be QA1 springs with the length and rate written on them. Mine has 10-275 on them which means 10" long and 275lb spring rate.
I can't seem to find any numbers on my springs. They are blue and probably more than 10 years old so I might in the same boat as you. Where did you see the numbers. I do recall something around 275lb. Is it possible you haven't done the nut up to the bottom of spring of enough to get enough a preload into the spring?
I am just about to pull my struts out as have finished mock up so will try and pull them apart and have a look. Mine is still lefthand drive and was having loads of problems getting pulleys to line up so have bought a vintage air kit with power steering pump so won't be using the RRS one. Hopefully it all works.
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This is a pic with the wheel dangling in the air. The 10-275 means 10" long springs with 275lb rate. When I got the car I had the front end setup by Bob Grant in Milton who does a lot of racing car setup so hopefully they know how to adjust coil overs.
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Mine are different to that. I will post up a couple of pics in the morning but I can't see any numbers anywhere on my springs. I will try and pull the struts apart off the springs hopefully on the weekend and come back.
Not sure what they are called but you have refitted the inner fender plates that go around the spring bolting to the shock tower of engine bay. The ones that hide the spring looking in the wheel well. I thought I read in the RRS instructions somewhere, that you don't refit that. I was going to get the holes welded up but wonder if they are part of the strengthening of the shock towers. I have the notch plates installed on mine as well as a one piece export brace/monte carlo bar from Maier racing so figure there should be plenty of strength?
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Sorry the previous owner got them installed and engineered so I can't say exactly what was done. I can only say there have been no visible stress crack or deformation in over 40,000Ks of street driving. I did however replace the factory brace with the RRS one with the cross brace.
One thing to be aware of, mine had the red urethane bushings that went brittle with age and the steering rack tried to fall out of the car!! I don't think RRS use the red ones any more.
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Have you contacted RRS to ask them what spring rate they recommend ?
Because the springs on yours are QA1's , RRS use lovells springs which are blue in colour. At some stage someone has swapped the QA1's in, possibly for a firmer ride.
The coils also look really close together , I'd be wary that they get coil bind which could give quite a jolt through your body work.
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Have you contacted RRS to ask them what spring rate they recommend ?
Because the springs on yours are QA1's , RRS use lovells springs which are blue in colour. At some stage someone has swapped the QA1's in, possibly for a firmer ride.
The coils also look really close together , I'd be wary that they get coil bind which could give quite a jolt through your body work.
Hey FB and Luke,
I was thinking the same but there is no thread at the bottom to adjust it off.
What’s at the top of the spring, hopefully not a packer.
Easy fix though!
Cheers Phil.
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At the top is the bearing cap like you see in the RRS Youtube videos. Actually I just took a quick look at the really old video where the guy is installing them in the Falcon and the springs are silver. Maybe years ago they used QA1 springs. I bought the car in 2008 with the setup installed.
On the weekend I will back the springs off 1/2 an inch and see what that does to the ride height.
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At around 1:27 they do a close up of the spring and you can see QA1 written on it.
https://www.youtube.com/watch?v=74PUns_dQQE
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At the top is the bearing cap like you see in the RRS Youtube videos. Actually I just took a quick look at the really old video where the guy is installing them in the Falcon and the springs are silver. Maybe years ago they used QA1 springs. I bought the car in 2008 with the setup installed.
On the weekend I will back the springs off 1/2 an inch and see what that does to the ride height.
Hey Luke ,
I think backing them off is a good idea!
Cheers Phil.
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Yep that photo is with the wheel dangling so the springs are actually more opened up than when it is on the ground. There is about 6 inches of thread below the lock nut it just doesn't show up in the photo.
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Yep that photo is with the wheel dangling so the springs are actually more opened up than when it is on the ground. There is about 6 inches of thread below the lock nut it just doesn't show up in the photo.
Hey,
I think you’re on the right track, I couldn’t see any thread on the photo, So that’s a good thing!
Cheers Phil.
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Is it really worth mucking around with that system any more? Seems to be most unsuitable and is spoiling your enjoyment of your car. :thud:
Any reason why you can't just fit normal '67 Mustang suspension, available from any of the Mustang parts suppliers in Australia, and happily drive off into the sunset? The stuff is relatively inexpensive. I mean, go back to basics with the simple factory design that the majority of us owners still use. :bolt:
Don't take that the wrong way, no offence intended, but I thought it worth asking the question. :thumb:
He'd have to put original towers back in, and then also an entire new RHD steering setup.
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Hey Luke,
You’ve got what you’ve got, we’ll massage it until we get it right.
The system may be 10-15 years old, but our cars are 50+ years old.
McPherson struts and coil overs are a great innovation and taken over the world.
You get rid of a heap of moving parts, wear points, top arms and extra ball joints.
Yours is just not set up yet.
Maybe the bloke you bought it off didn’t understand it and made it worse.
I’m sure with a bit of tinkering and reporting back to the forum we’ll get it right.
I’ve been tinkering (Enjoying every minute) with my car for six years and it might be right next year! Hahaha 🤣
Cheers Phil.
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Hey Luke,
I’ve just looked at a pair of Tein VE Commodore Ute coil overs on Gumtree and they have a very short helper spring with less compression fitted at the bottom.
Have a look, you’ll get the idea.
You may be able to set up something like this to give you softer ride.
Cheers Phil.
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Ive got RRS struts on my 68 with a 460 big block.
RRS made a blunder with shipping my struts originally with small block springs, initially setup with quite a bit of preload so they sacked out.(Mine are a later version then yours with Lovells blue springs.) It wasnt untill I got past their sales people and talked to their engineer did we realise the mistake and they then sent a set of big block springs.
Since then, really happy with the way it handles, great system . And with the RRS rack, steering is fantastic even with a lightly larger turning circle.
I'll see if I can find the old small block springs and check if they have the label still on them. Will let you know the outcome.
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Even if you do lose some height, have you still got a bit of adjustment at the bottom of the strut to fix this? Mine ride height needs to come down about an inch and would still have maybe another inch of thread left at the bottom of strut after
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OK I will report back with my homework. I measured the initial ride height from the pivot point of the lower control arm as I figured that was the most precise point to do it. I then backed the springs off by exactly 5 turns on both sides and drove the car backwards and forwards a few times to settle the suspension. This lowered the car by the same amount as what I had lowered the springs (Just over 1cm or more than the width of the lock nut). I then tried a bump that I know makes the car thump and got the same result :-(
I also took a photo of the spring with the car on the ground and as you can see it is quite compressed. If I go for a lighter spring I will just have to compress it more to get the same ride height. I think 67FBGT is right it is the shocks that are the problem. Are the newer adjustable shocks the same 4 position adjustment or are they different?
The motor is a Dart 347 with Alloy heads and an 8 stack. It does however have air and steer so that adds quite a bit of weight over the front.
I will have to put the pics up 1 post at a time due to server limits.
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Pic 1
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Strut at full extension
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Strut with wheel on the ground
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Where I measured ride height
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Hey Luke,
Good homework.
I reckon you can drop it some more but those springs are very compressed with the weight on it.
Flat conical springs are overloaded. I think you say they have passed their helix angle.
If you are looking for heavier springs VPW are a local agent.
You may not have to go much, 325Lb/in.
Cheers Phil.
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Phil ,
325 springs will make it ride like its solid they are for a big block.
I found the tags off of the small block RRS strut springs , they were p/no 65-275
bigblock springs like I have in my 68 are 65-325.
they are both 10 inches in length.
Luke , whats your shocks set to ? They have a setting of 1 through to 4 . RRS normally set them to 2
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Phil ,
325 springs will make it ride like its solid they are for a big block.
I found the tags off of the small block RRS strut springs , they were p/no 65-275
bigblock springs like I have in my 68 are 65-325.
they are both 10 inches in length.
Luke , whats your shocks set to ? They have a setting of 1 through to 4 . RRS normally set them to 2
Good to know WRT to BB spring rates. I've tried them from 1 to 4 with little difference, when you try to shake the car side to side it barely moves. How compressed do your springs look with the car on the ground? If you bounce it over a speed bump you can feel the springs compress once then it rebounds and that's it.
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There no sign of any leaks is there? Maybe the struts are faulty.
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They seem to be as dry as a bone. It's always been like this. I've been doing a bit of reading and it seems QA1 springs are thicker than most other brands and seem to be more prone to binding.
I might be exaggerating how bad this is as I have actually put up with it for about 12+ years now but it is something I would like to address.
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Hey Luke,
I definitely think your coils are to soft.
There is definitely marks on those springs where they have bottomed out.
Lowering it like I said is not right!
I think we need to jack it up high, to high and take it for a drive.
That’s not going to help either! I think you need heavier springs!
On this case I’ve changed my opinion so much.
Cheers Phil.
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It looks like QA1 redesigned their springs in 2015 to use thinner wire and less coils for the same rate and length. They must have done that for a reason.
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Hey Luke,
I’ve had another thought, if they’ve wound the springs up to hard plus the weight of the car the springs would compress like that, wind the nuts down another inch.
The front will be low but if you’ve got 7” rims and 225 tyres they will only scrub lightly if so.
Cheers Phil.
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I think your going into coil bind then spring rate will go basically infinite.
Given you know required compressed length ( and current uncompressed), rate required and approx corner weight I would just track down some new springs to suit. I have Hyperco in my coilovers.
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I don't think installing RHD 1960s engineering is the real fix. Except for hitting a big enough bump to cause the springs to bind the car drives great.
I have ordered a pair of 300lb Eibach springs. I will fit them, set the car to the same ride height and report back.
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What is your static compressed spring length?
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OK I have fitted the new springs.
BTW they are Strange Hypercoil 300lb springs not Eibach like I said previously.
RESULT!!!! I set the ride height to 10mm higher than it was originally set (Still lowered for a 67) and I cannot make the suspension thump like it used to. I went as fast as I safely could over a bump that I know shows the issue at much lower speed and there was no noise from the suspension at all!!! It just went over it like a late model car.
The new springs have fewer coils than the QA1 springs so I probably would have been fine with 275lb rate.
Anyone with the silver QA1 springs in their RRS setup they need to go IN THE BIN!!!!
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That's a good result. Bit late but got mine stripped and found this tag on them.