Front springs, dampers

[gdr]

Here's another query - with the front ride height adjusted to 110mm, when suspension on full droop, springs are completely loose (no preload) such that they could come off the seats. Is this a potential problem and is it normal with Ultima's with the Intrax dampers? I don't intend to get airborne, but imagine if it did happen there would be a fair bit of banging and crashing on landing and if springs did not reseat properly result could be a bit unpredictable to say the least. Can't see any way to prevent this when using the spring/damper supplied other than winding up the ride height to higher than recommended. Rears are OK.

[davefiddes]

Sounds alarming! I saw this on an XTR2 at Knockhill a few months back and thought it was pretty shoddy...didn't think that it would be a problem for an Ultima though.

[jschwartz]

it's normal.

[gdr]

jschwartz said:

it's normal.

I'd better keep off these Knockhill kerbs in that case.

>> Edited by gdr on Friday 3rd October 14:13

[USCANAM]

gdr said:

Here's another query - with the front ride height adjusted to 110mm, when suspension on full droop, springs are completely loose (no preload) such that they could come off the seats.

According to Carrol Smith, this is an absolute No No, and is a reflection of poor engineering.
I do have the problem with the CanAM, and I intend to machine some aluminum spacers this winter to eliminte it.
Jack

[gdr]

Jack,
where would the spacers fit so ride height not affected?

[USCANAM]

gdr said:

Jack, where would the spacers fit so ride height not affected?

George
All the spacers would do is take up the space when ride height as been set, and the springs are unloaded. It would stop the springs from rattling around.
It really wouldn't matter where they were located, but I'll probably put them at the top.
My Cobra has this problem at the rear. When I jack the body up, the springs will move off their perches at the top, and not relocate themselves when re-loaded. I have to bang them with a soft mallet to "spring" them back into position.
I think what Carrol was trying to say is "get springs of the correct length for the job"
Jack

[gdr]

Jack,
Yes, that makes sense.
Having had a browse through my Demon Teeks catalogue (popular UK race/tuning parts mail order outfit), I see they sell the following.
"Flat section helper srings used to fill the gap between spring and spring seat when the main spring is too short to load the shock absorber seats" - 2 1/4" ID items come in 2" and 4" lengths and cost only £5 or £6. They also sell hard plastic adapters to mate the main and helper springs together for £8.
Would appear the helper springs are very low rate and have a short compressed length, only coming into play when main is fully extended. Should be able to keep the spring preloaded on the seat at all time - I will give these a try.
George

[gtrclive]

These (of the shelf) Shocks are to long. The rears on my car did the same, so I sent them back to the manufacturer and got them to shorten them. It was dam dangerous and after nearly loosing a spring seat a couple of times, I had no choice. Also the rear wheels touched the cill because they where to far down. So measured the best shock lenght both front and rear and had pistons made to the right lenght.
Now can hit the same bad bumps and be sure I won't loose a spring seat. You get what you pay for so I was told.

[gtrclive]

PS the easy cure is to fitt Spring assister, there about £9.5 each. They only uncoil when the wheel leaves the floor, but it's enoough to put some load on the spring seat to stop it falling out.

www.merlinmotorsport.co.uk/

They call them Helper springs on this sight.

>> Edited by gtrclive on Saturday 4th October 09:09

[davefiddes]

Helper springs sound like a reasonable band-aid for the problem. No substitute for getting the right throw on the shocks and length of springs...it'd be nice if our "custom" Intrax shocks really were...though for the money I suppose we shouldn't complain.

Since we're talking about putting stuff beside the springs. Has anyone good any opinions good/bad on fitting thrust bearings between the springs and the seat post? It seems to be a good way to stop the springs binding when adjusting the ride height.

[USCANAM]

davefiddes said:

Since we're talking about putting stuff beside the springs. Has anyone good any opinions good/bad on fitting thrust bearings between the springs and the seat post? It seems to be a good way to stop the springs binding when adjusting the ride height.

Dave
I have these radial thrust washers (very expensive) on my Penske shocks for the F2000. Supposed to allow the spring to work easier by allowing the spring to rotate as it expands and compresses (?).
I think this would be overkill on an Ultima unless it lived only on the track.
Not sure if it would help in adjusting the spring as on the F2000 my springs are pre-loaded on the inboard mounted shocks, and there are pushrods and bell-cranks going to the hubs. Have never had to adjust the springs while they had the weight of the car on them. All height adjustments are done with the turn-buckles on the main pushrods. (a very precise method when the car is on the scales).
The spring helpers look interesting.
Jack

[andycanam]

Hate to say this but I'm sure mine don't do this on the Ultima (front or rear) even with the ride height at factory settings.....

I do have a set of those helper spings on my shelf but they are for my other car which also has coil overs and DOES dislocate when jacked up.

They do more than one size helper spring, I needed the biggest one on the cossie as it dislocates by nearly 100mm! not good.

[davefiddes]

Got my car down and driving about for the first time yesterday () which gave me a chance to see what the ride height is with a representative weight in the car. I had just left the springs with the seats finger tight. The back was down about 5mm so I'll have to jack that up esp as I don't have a full load of fuel in. The front however was up about 35-40mm. I figure that this will lead to about 25mm of slop on the front springs at full droop. How does this tie up with what you guys have seen?

Andy, I don't suppose you'd happen to know what the open length of your springs are? Maybe Ultima changed the springs or Intrax changed the throw of the shocks at some point? I got my set back in Nov 2002 which I'm guessing is quite a bit after you but about the same time as Jack, George and Jeff???

I think you're right about the thrust bearings being a bit overkill for road/light race duty Jack. They're almost the same price as a good spring! I'll maybe save them for my next car which will definitely have inboard springs and other goodies too...

[USCANAM]

davefiddes said:

I'll maybe save them for my next car which will definitely have inboard springs and other goodies too...

Dave
I got my kit Sept 2002. Will be re-setting up the car for the track date next week, and will document the new settings and pass them on.

Inboard spring and shock systems brings up another good topic for discussion. While impressive looking, I think they tend to be fragile and expensive. (replacement cost for ONE of my Penske shocks on the F2000 is $1500!!). A few weeks ago when I hit some debris on the track after a crash in front of me with the F2000, replacement for the bent pushrod was $138 from VanDiemen. Had this been a conventional setup, there would have been no damage when the front wheel bottomed, and I would have been able to complete the race. However, a conventional system cannot be finely tuned like an inboard system.
Having said that, before I made the plunge into the Ultima, I spent 3 days at the Daytona Rolex 24 Hour in 2002. That was when K&N Filters were competing with the GTR. I checked out some of the other cars in the same class,(i.e. Saleen, Mosler) to see what they had for suspension and they were basically coil over, except they all had some form of sway bar control.
What does that tell you?
Jack

[gdr]

davefiddes said:

I figure that this will lead to about 25mm of slop on the front springs at full droop.

Sounds about same as mine. I got my springs dampers much the same time as you, late last year so perhaps it is a later batch compared to Andy's that dislocate at full droop. I think shorter pushrods on the dampers would be the way to go.

>> Edited by gdr on Monday 6th October 14:31

[bigmack]

Just a note of interest. Your springs should have a number stamped to them. The first number is the free length in millimeters and the second number is the rate(N/mm). You can go to H&R's website to get the conversion from (N/mm) to (lbs/inch). Also, these Intrax springs have a 60mm ID.
Cheers!
-Mack

[davefiddes]

Just had a look and my car has 180mm free length springs at both ends. With 110 N/mm on the back and 80 N/mm on the front. It would appear to be fairly cheap to swap out the stock springs and fit longer 200mm ones with the same rate (figuring they won't behave too differently)? I guess the best solution though is to shorten the length of the damper. Do you have any contact details for Intrax in the UK Clive?

USCANAM said:

Inboard spring and shock systems brings up another good topic for discussion.

I know what you mean about pushrod suspension being fragile. Long and necessarily slender rods in compression are always going to be prone to buckling. Pushrod suspension allows you to do cool things like rising rate though which strikes me as a useful thing to have if you have a heavy aero download. Course you've got to cool the dampers and specially duct airflow to them which you don't bother with in the wheelwell I guess. In a closed sportscar there's very little to gain on the aerodynamic front compared with FF, F3, etc...

I'll add the current racing TVRs to your list. On the otherside pretty much every LMP 675 and 900 I can remember, Lister(?), Stealth, Radical, Westfield XTR2 (and all their clones) all seem to run some form of inboard suspension at least at the front.

[USCANAM]

Good points Dave, but I believe you really have to look at the application. If you're just going to be driving the car on the road, and in the per-chance the car might someday be on a track, is it really worth all the extra time, work and money.
I read all these posts about how they need all the power and handling etc. etc. for the track, which in most cases it will never see.
To really enjoy your home-built car to the fullest, I really believe in the "KISS" principle.
But that's just my humble opinion.
Regards to all
Jack

[davefiddes]

USCANAM said:

To really enjoy your home-built car to the fullest, I really believe in the "KISS" principle.

I agree. I still figure that the Ultima is a good blend of simplicity and raw power for use on road and track. Don't intend on getting rid of mine until either the car or myself is worn out .

Course it doesn't stop me musing about my next project though...which will be a 100% race car. As it has to be able to keep up with fast race only Radicals, a ProSport 3000, nimble 600bhp ex-thundersaloons to be competitive the approach I want to take is a little different from an Ultima (though probably with a similar drivetrain). As I already have a fun weekend car I don't care if it takes 10 years too....