Sping Rates too Stiff?

[spitfire4v8]

you're right in most of what you say about preload, however the droop stop is the open length of the damper, you can have just 5grams of preload on a spring at full droop and it's still pre-loaded .. but you would still get the full droop travel as you raise the car. If you preload a spring you don't lose that droop travel unless you have enough preload to fully support the car at rest onto the droop stop. On a typical tvr this would be around 250kgf per corner as you say, but most preloaded springs will only be around say 100kg at full droop and the rest of the loading is taken by the natural compression of the spring as you lower the car to it's ride height. The std springs are very soft rate and long .. 11 inches maybe?

[ChrisPap]

spitfire4v8 said:

you're right in most of what you say about preload, however the droop stop is the open length of the damper, you can have just 5grams of preload on a spring at full droop and it's still pre-loaded .. but you would still get the full droop travel as you raise the car. If you preload a spring you don't lose that droop travel unless you have enough preload to fully support the car at rest onto the droop stop. On a typical tvr this would be around 250kgf per corner as you say, but most preloaded springs will only be around say 100kg at full droop and the rest of the loading is taken by the natural compression of the spring as you lower the car to it's ride height. The std springs are very soft rate and long .. 11 inches maybe?

Right you are. It was late and I wasn't thinking it through properly!I'm not used to the damper body working as the droop stop!

I have access to a range of damper dynos at work but what a pain to strip the dampers back off, and the original set has been binned by now I'm sure.

Not convinced the dampers are the problem, as I say, I've backed the adjuster off to the point the suspension feels underdamped like a pogo even at low damper speeds, and it just doesn't feel right.

I need to get to the bottom of the spring rate issue because if it is in fact true that the aftermarket companies are doubling the original spring rates then I need to sort something out because it seems ludicrous. I have the same ride height, same roads, but suddenly twice as stiff springs and it feels more like a go kart than a sports car now.

[RedSpike66]

glow worm said:

ChrisPap said:

Does anyone know what the TVR standard rate is?

Because the geometry is different between a Sag and a Tuscan I don't think you can compare them.

Edited by glow worm on Friday 3rd May 21:06

It's a pity this table doesn;t have Tamora/T350 factory settings aswell as Tuscan and Sagaris. We know the Sagaris is quite different than the T350/Tamora, but is Tuscan different than T350/Tamora ??? As you say, the extra leverage from the wider Sagaris track probably goes some way to explaining the significant increase in spring rates between Tuscan and Sag.

I might be stating the obvious here, and am no expert, but if nothing has changed except Damper/Spring on your car, it's like you're now running Sag spring rates on a non Sag car and they're probably simply too stiff for that suspension ??

But what are standard T350/Tamora spring rates ????

[fredd1e]

RedSpike66 said:

It's a pity this table doesn;t have Tamora/T350 factory settings aswell as Tuscan and Sagaris. We know the Sagaris is quite different than the T350/Tamora, but is Tuscan different than T350/Tamora ??? As you say, the extra leverage from the wider Sagaris track probably goes some way to explaining the significant increase in spring rates between Tuscan and Sag.

I might be stating the obvious here, and am no expert, but if nothing has changed except Damper/Spring on your car, it's like you're now running Sag spring rates on a non Sag car and they're probably simply too stiff for that suspension ??

But what are standard T350/Tamora spring rates ????

Same as those listed in the file for pre 05 Tuscan. IMO the 27NM rear is far to soft on anything but a billiard table. Any roa with a rise dip camber change like most northern roads will have the rear on the bumpstops in the blink of an eye. This is made worse if Bilstiens are fitted in place of the old Harvey Baileys as the Billie bumpstops are shorter, note that's not saying the HBs were good but the longer bumpstop came into effect very early effectively meaning the spring rate was the rubber bumpstop and not the soft steel spring.

[SergSC]

IMO I think spitfire4v8 hit the nail on the head about the high speed resistance.

[ChrisPap]

To any curious onlookers: No one seems to know for sure but the best guidance I have (from Jason at Str8six) is that the Tamora factory spring rates are 300 front and 250 rear.
If correct that means that the standard Nitron springs are 30-33% stiffer than the factory set up, which may explain why I went from feeling the car was suprisingly good on the lanes to feeling it was quite uncomfortable. Nitron did confirm that them being 30% stiffer sounds 'about right' and that it's something they've done in response to customers desire for 'fast road and track use'- ie, feels like a go kart.


I've ordered a pair of 275 springs for the rear and will move the current rear 325 on to the front and see how I like it. Might stick the dampers on a dyno while I'm at it- just to see what's going on and will report back.

[phazed]

275/325 is standard Chim/Griff fare iirc and is too soft.

You need approx + 20% for slightly spirited driving IMHO.

[ChrisPap]

Thanks, although I suspect the Chim and Grif are a different kettle of fish to the T cars.

Maybe the factory rates are too soft for track use, it does feel mighty on smooth roads on the stiff springs, but I don't do track days, I do 80% british B-roads, and I was pretty happy with the car before. I'm hoping to have the springs toward the end of next week and will update once I get them on.

[TVR_owner]

Billies with Sagaris valving and Sagaris spring rates was an excellent upgrade on a previous Tuscan I owned. It provided a very compliant set up. Not too stiff for the road, never felt too harsh.

[SergSC]

A little update. Finally got round to getting the car up in the air to change the settings.
Was previously at 10 all round and now on 7. The result is a corresponding 30% increase in comfort (very scientific I know) but no pogo'ing. Bear in mind these are the 46mm set.

To summarise, at delivery settings (10) my set was definitely cringe inducing on crap public roads, but at 7 they are IMHO in the realm of acceptability and without adverse effects.. these things are very subjective though.

I look forward with great interest to hear about the result of spring rate experiments.

cheers
S

[Sevenman]

SergSC said:

I look forward with great interest to hear about the result of spring rate experiments.

I got the Tamora back from Neil Garner last week with refurbed dampers (Gaz Gold Pro), uprated rear springs, and geo done.

The difference is fairly subtle. The original geo was not too far off so I wasn't expecting anything dramatic.

The rear springs have gone from 325 lb/in to 375 lb/in.

I can't tell much difference so far on a few drives. It might be a little more controlled over bigger bumps, but seems no worse on the little stuff.

I might play around with the rear damping, try a click stiffer / softer than where it has been set.

More info on the settings at this link to my blog.

[ChrisPap]

Update:

I have since bought new TVR OE spec springs for my car. The fronts are the original dark green, the rears are the newer spec light blue (originals were white). As they are not marked I got them tested for rate at the only damper place I trust, and WHOA!

The fronts are 195 lb/in, and the rears are 230 lb/in. That means the springs supplied with Nitrons are over TWICE as stiff on the front (205%), and the rears are 152% of the original stiffness!

No wonder my car went from feeling suprisingly nice on B roads to being really quite unpleasant. I can't wait to get them on the car now and see what's what!

[RobertoBlanco]

ChrisPap said:

Update:

I have since bought new TVR OE spec springs for my car. The fronts are the original dark green, the rears are the newer spec light blue (originals were white). As they are not marked I got them tested for rate at the only damper place I trust, and WHOA!

The fronts are 195 lb/in, and the rears are 230 lb/in. That means the springs supplied with Nitrons are over TWICE as stiff on the front (205%), and the rears are 152% of the original stiffness!

No wonder my car went from feeling suprisingly nice on B roads to being really quite unpleasant. I can't wait to get them on the car now and see what's what!

Whoa, that sounds like really low figures to me. I always thought, that the 325 at the rear axle is a bit too soft, when two passengers in the car (GAZ GP). So, I'm looking forward to what you will report, Chris

I softened the dampers now to 6 front and back and tested the setting on some b-roads in the area. Very comfy ride, a huge improvement! No hopping over smaller bumps anymore. Downside is, that the rear is so soft now, that the splitter almost grounds, when i floor it (1 passneger!). Front feels a little too wobbly and unrefined. And I didn't even corner hard on the test run.

So will try 7 at the front and at least 8 on the rear now. Will see if there is truly a threshold setting, where it changes abruptly from soft to hard, like i read here on the forums.

[Walford]

are they the same free length

[ChrisPap]

No, the eibach free length is much longer and requires pre-load in the spring for ride height. I'll measure the differences once I have the nitrons of the car.

[QBee]

Note to all damper-changers. Always keep the old ones unless they are totally broken. Dampers have to be sent back to te manufacturer for refurbing, re-speccing, and if they just break. You need something on the car while your current set are off the car, if only to sit on.

Spring rates, damper type, damper spec, ride height, damper adjustment, bushes......so many things that can affect ride.

Don't forget three more -
accuracy of your geo settings: your car will need a full geo after changing dampers
tyre stiffness: the load rating of the tyre is indicative of sidewall stiffness
tyre aspect ratio: lower profile = stiffer ride

[phazed]

ChrisPap said:

No, the eibach free length is much longer and requires pre-load in the spring for ride height. I'll measure the differences once I have the nitrons of the car.

I wonder what your experience of the 46mm Pros are now after all this time?

Mine have been back to Nitron at least 5 times and have been fully revalved and spring rates changed.

Still unhappy so changed back today go my Gaz Monos.

Best thing I've done this year! Bye bye crashy, hello damping...................

[QBee]

I know, as has been pointed out above, that the Chim/Grief are different from T trolleys, but I am upgrading my Chim front springs on Monday from 400 to 500 lbs to try to stiffen the front end a tad. All done in consultation with my TVR guy and Derek at Absolutely Shocking.

I am told race cars can and do run 800 lb springs, but I only track day mine as well as general/fast road. I have been running with the dampers on rock hard on 400 lb springs.

If you are feeling your ride is too soft, do try stiffer springs - they aren't exactly expensive.

[Andy_mr2sc]

Is this all to do with comfort or is it about yaw control too. I'm wondering if anyone has tried stiffer anti roll bars instead of keep upping the spring rates then complaining about the ride quality?
Andy

[phazed]

I've recently fitted stiffer ARBs but as yet not tried the car on the track, (last 2 TDs written off because of bad weather!).

I'm running 450/400 with my set of Monos and it doesn't feel too stiff at all.