Griff - Go for Gaz?
Discussion
I am going for the protech set up from www.track-car-solutions.co.uk
They are a nice alloy damper with rose jointed ends and lovingly built up by some strange bloke with glasses
.
They are a nice alloy damper with rose jointed ends and lovingly built up by some strange bloke with glasses
. torquemada said:
My 65k Griff is getting a tad tired in the undercarriage and I'm considering having Gaz shocks fitted, with the standard bushes. Thought about Nitrons, but are they really worth the extra? I only do maybe one trackday a year and only 4k miles pa average.
Any opinions appreciated.
great for the money and have set ups from a certain WELL KNOWN Tvr expert
fine for what you need and excellent value IMHOI've fitted GAZ to both my "S2" and Griff and been happy with them both times......I only use the car for blatts around the roads (still trying to find the nerve to get on the track.....a training day is calling me 
)
Warning ..... get them set-up properly otherwise you will think they are crap.
I can not make any comment on how these compare with the more expensive shocks such as nitrons etc. as I have no experience of them....... but the more serious trackers seem to favour the Nitrons.
) Warning ..... get them set-up properly otherwise you will think they are crap.
I can not make any comment on how these compare with the more expensive shocks such as nitrons etc. as I have no experience of them....... but the more serious trackers seem to favour the Nitrons.
The bottom line is you pretty much get what you pay for .. Gaz dampers will be perfectly alright for the use you are putting the car to. If you're not a track day hero then you'll not need the extra heat dissipation or lower unsprung weight of an alloy body damper so i would suggest a Gaz is ok.
Blimey i can't believe I beat hawk-eye Bugsy to a suspension topic!!
Blimey i can't believe I beat hawk-eye Bugsy to a suspension topic!!
I have asked this question of the boffins and was told that frothing can be a problem on sustained track use but gas charged shocks are more affected than shocks fitted with a gas bag, so that is why the better steel and alloy shock manufacturers fit a gas bag.
According to the experts I talk to, a steel shock can perform quite well, as long as it's properly valved and set up decently but will never give the same performance as a two or three way adjustable shock.
According to the experts I talk to, a steel shock can perform quite well, as long as it's properly valved and set up decently but will never give the same performance as a two or three way adjustable shock.
bugsy said:
According to the experts I talk to, a steel shock can perform quite well, as long as it's properly valved and set up decently but will never give the same performance as a two or three way adjustable shock.
Excuse my ignorance here but are you saying NITRON are 2/3 way adjustable and GAZ are not?
Cheers
Lazy
The Nitron NTR are single adjustable but they do have a gas cylinder underneath and gas is introduced via a needle valve through the piston, it's quite a neat way of doing the job but I think Jools is going the double adjustable route soon and this would give better control of rebound for the track boys.
I do supply double adjustable and even remote gas canister shocks but only to the pure race guys and don't see the need to retail such specialist products.
I do supply double adjustable and even remote gas canister shocks but only to the pure race guys and don't see the need to retail such specialist products.
There seems to be a couple of threads running at the moment ref' dampers/suspension geometry etc. I'm intending, in the near future, to be looking for a new set up for my Griff and there seems to be a lot to take into consideration, not least of which is expense/use.
There's a marked jump in cost between those which are steel bodied and those which are allu bodied. Perhaps the allu bodies require steel sleeving? They do tend to come with mounting bearings that'd be superior in performance when compared to a cushioned plain bush. I can also appreciate the benefit on track in having a reduced unsprung weight or valving for both compression and rebound.
However, I've also read more than once that the allu bodied items also dissipate heat more effectively allowing the damping medium to be kept at a near constant temperature and thereby providing a more consitant control of what the spring is doing. Is this so? Surely both have a similar surface area and the wall thickness would render the material insignificant? Doesn't the medium come with VI improvers to maintain an improved regulation of viscosity?
There's a marked jump in cost between those which are steel bodied and those which are allu bodied. Perhaps the allu bodies require steel sleeving? They do tend to come with mounting bearings that'd be superior in performance when compared to a cushioned plain bush. I can also appreciate the benefit on track in having a reduced unsprung weight or valving for both compression and rebound.
However, I've also read more than once that the allu bodied items also dissipate heat more effectively allowing the damping medium to be kept at a near constant temperature and thereby providing a more consitant control of what the spring is doing. Is this so? Surely both have a similar surface area and the wall thickness would render the material insignificant? Doesn't the medium come with VI improvers to maintain an improved regulation of viscosity?
I have asked this question of Gaz and they only see the difference in weight as an issue with the types of material used.
I like the idea of more profit but at the end of the day, I haven't bothered much with rose joints or alloy shocks unless asked to supply but they are available from most manufacturers.
I like the idea of more profit but at the end of the day, I haven't bothered much with rose joints or alloy shocks unless asked to supply but they are available from most manufacturers.
bugsy said:
I have asked this question of the boffins and was told that frothing can be a problem on sustained track use but gas charged shocks are more affected than shocks fitted with a gas bag, so that is why the better steel and alloy shock manufacturers fit a gas bag.
Unfortunately you seem to have been fed a bit of propaganda bollox there Bugsy ..
All twin tube dampers have to run a gas bag, except one particular design of ohlins damper which has a minute gap between the inner and outer tubes which are open at each end, and oil displacement by the piston is accomodated by a remote reservoir under pressure. All other ohlins dampers are monotube design.
There are NO advantages of a gas bag damper over a pressured damper .. get that right first. Whoever has been telling you that shouldn't! I suspect it's a twin tube damper manufacturer.
A gas bag is nothing more than a crisp packet type structure containing a small volume of gas. It deforms (crushes) as the piston rod enters the damper and displaces oil from the inner tube to the outer tube. It's sole purpose is to accomodate oil displacement.. it does NOTHING to stop aeration and frothing of oil.
There are some disadvantages of twin tube dampers .. especially steel ones .. these are more unsprung weight, poorer heat transfer, smaller piston, etc etc.
Twin tube dampers cannot be run inverted unless each one is individually bled of air, this takes hours and makes it unrealistic to manufacture as the whole point of twin tube dampers is that they're cheap to produce and that is the ONLY reason they're twin tube.
Having a cheap manufacture process means though that you can spend money elsewhere on the damper .. alloy bodies for instance improve heat transfer, you can afford a larger piston rod and better quality valving and you can make a proper bleed valve system.
Larger piston rods are important because all the oil that goes through the valving is oil displaced by the piston rod. The oil displaced is pi times radius squared times rod movement, a small increase in rod size makes a much larger oil displacement .. this is good for two reasons : firstly the oil displaced is a greater volume so the oil has an easier life in the damper, but also large displacement of oil takes place even on very small rod movement so they're much more sensitive to small movements.
Gas pressure Mono tube dampers have many advantages.
The gas pressure stops aeration of the oil as the oil would normally like to cavitate behind the piston rod and valving.
The gas pressure is behind a floating piston which keeps the oil and gas separate, this means that all the oil in the damper body stays there. This in turn means that they can be run inverted reducing unsprung weight.
Because all the oil is in contact with the damper outer body the heat transfer is much greater, so oil viscosity is much more consistent.
There is no restriction on piston valve area on a mono tube up to the size of damper body used.
So:
general rules are :
Steel body gas bag type twin tube damper is the basic type entry level damper. Oil heats up more in these and loses viscosity, they are *more* susceptble to aeration/frothing. cannot be run inverted. high unsprung weight.
alloy body twin tube is the next step up, has manufacturing build costs of a std twin tube, but money usefully spent on better heat transfer of alloy body and usually better valving/bleed systems. lower unsprung weight. cannot be run inverted. the minimum spec of damper you should consider for track use.
alloy body mono tube gas pressure is the best type we can consider at sensible pricing. maximum heat transfer, best valving area, best oil transfer across valving, no aeration of oil. best performance. can be run inverted.
I hope that clears up much of the confusion and mis-information surrounding dampers and what they're suitable for.
its all getting technical again
Anyway back to the original question.... like Hoover I wanted my Griff sorting mainly for road use and decided to go for GAZ shocks after lots of questions and looking around.
Just got the car back today from Steve Guglielmi's... had a full set of GAZ shocks and springs(400/325) fitted and the car setup properly... first impressions are very good, it has totally transformed the handing especially on fast uneven roads and cornering is now something else
Big thanks to Steve Guglielmi and Dave for fitting them and setting up the car and also thanks to Bugsy for answering all my questions and emails.
Off out to play again now!
Anyway back to the original question.... like Hoover I wanted my Griff sorting mainly for road use and decided to go for GAZ shocks after lots of questions and looking around.
Just got the car back today from Steve Guglielmi's... had a full set of GAZ shocks and springs(400/325) fitted and the car setup properly... first impressions are very good, it has totally transformed the handing especially on fast uneven roads and cornering is now something else
Big thanks to Steve Guglielmi and Dave for fitting them and setting up the car and also thanks to Bugsy for answering all my questions and emails.
Off out to play again now!
I don't think it's misinformation Jools, it's a fact that almost anything can be turned to an advantage, as we saw in the recent sprint article, separating the wheat from the chaff is easy if you go to an expert installer
I checked out the shocks in question and was unsure about a sealed gas charged shock that couldn't be rebuilt easily, as being viable or effective, which is why I asked the question.
What you are saying is that alloy shocks with rose joints do have an advantage over steel shocks and are worth the extra £320, if thats the case I'm sure that the experts will all ask for them.
I checked out the shocks in question and was unsure about a sealed gas charged shock that couldn't be rebuilt easily, as being viable or effective, which is why I asked the question.
What you are saying is that alloy shocks with rose joints do have an advantage over steel shocks and are worth the extra £320, if thats the case I'm sure that the experts will all ask for them.
redboy said:
its all getting technical again
Anyway back to the original question.... like Hoover I wanted my Griff sorting mainly for road use and decided to go for GAZ shocks after lots of questions and looking around.
Just got the car back today from Steve Guglielmi's... had a full set of GAZ shocks and springs(400/325) fitted and the car setup properly... first impressions are very good, it has totally transformed the handing especially on fast uneven roads and cornering is now something else
Big thanks to Steve Guglielmi and Dave for fitting them and setting up the car and also thanks to Bugsy for answering all my questions and emails.
Off out to play again now!
Nice one, I just spoke to Gugi and he is now much happier with the new valving and revised bumpstop but at the end of the day it's down to the punter who has to drive the car to decide if it works for him, please keep me posted on how you get on.
I hope no one will mind a brief thread hi-jack but Bugsy's last comment made me think of this and whilst there are experts around...
Can someone explain this to me? Had Nitrons fitted with 325lbF/250lbR. When set on "comfy" road settings it would wallow and float a little over bumps particularly when pressing on. (Easily solved by stiffening the dampers.) However, I changed the springs for 400lbF/300lbR and even on those same soft settings, it feels much more solid. Much more controlled than with the softer springs.
Common sense seems to suggest that harder springs should have more damping but that doesn't seem to reflect what I've experienced.
Can someone explain this to me? Had Nitrons fitted with 325lbF/250lbR. When set on "comfy" road settings it would wallow and float a little over bumps particularly when pressing on. (Easily solved by stiffening the dampers.) However, I changed the springs for 400lbF/300lbR and even on those same soft settings, it feels much more solid. Much more controlled than with the softer springs.
Common sense seems to suggest that harder springs should have more damping but that doesn't seem to reflect what I've experienced.
What you're experiencing is the difference between the two spring rates. .. hardly surprising you say as that's the only thing you changed .. so I'll try and explain.
On soft springs you'll get a large wheel deflection for any given input, and the only things stopping the wheel moving a longer way are the spring rate itself and the compression resistance of the damper.
The damper has a wide range of compression and rebound resistance depending on how fast the wheel is being asked to move .. typically you would narrow these down into low speed , medium speed and high speed rates. In effect what you are talking about is piston speeds, ie the speed the rod is moving in the damper body.
To get good ride quality at sane speeds most dampers will run a low amount of low speed compression .. so that as you're pootling around town you aren't subjected to jarring through the car .. the piston rod has minimal damper resistance to movement and the majority is done by the spring. Any given input will allow the damper rod to move a significant distance on soft springs thus the wheel follows the bump but the car body doesn't.
At higher piston speeds the resistance is ramped up so it's possible to get a damper that offers good compliance at low piston speeds but good control at high piston speeds.
With low spring rates and low amount of damping you can get long piston rod travels at low piston speeds and also at low speeds get low damping forces .. hence the float you feel over long undulations .. in effect these are low piston speeds so low damping effects.
This in itself if kept limited is not a bad thing .. if the wheel follows the bump then the tyre contact patch is kept relatively stable .. the effect is called contact patch variation with load .. and if you stiffen the suspension you limit how freely the wheel can move .. the tyre then distorts more as it goes over the bump .. grip levels change and on the limit the handling will be unpredictable.
It's important not to go too soft .. that's why i always say for road use : use the softest damper setings you can whilst still giving you the control over the car that you require. This keeps the car as stable as possible whilst maintaining as consistent a contact patch as possible too. it makes for predictable, grippy on-road driving.
What you've noticed though now is that with the higher rate springs you've physically restricted the travel you can put the piston rod through because if you increase the spring rate you need more force to deflect it any given distance .. so if you drive the same road again with stiffer springs you'll notice that that car follows the bump in the road rather than it being absorbed by the spring/damper.
In actual fact your damper is exerting less control over the higher rate spring than before as the rebound damping hasn't been uprated .. but it *feels* more connected to the road because the car is following the bump rather the bump being absorbed.
Furthermore if you go stiffer on springs you increase the contact patch variation as you go over bumps .. finding the compromise that works for you is all the fun in suspension presumably you've found a compromise that suits you and your driving better.
On this note, someone came to me at a recent track day and said that *cerberas like to run stiff at the back* .. well as with so much in suspension circles it's utter garbage.
The general rule for a powerful rear drive car is front stiff rear soft .. how stiff and how soft you go is dependant entirely on what you want from the car. I think the person in question also doesn't appreciate the difference in wheel rate bewteen the front and back of most TVRs .. if you fitted the same spring to the front and the back you would still end up with a softer back end as the spring's mechanical advantage over the wheel is less.
What you need is a suspension that works for you and you alone .. if it does what you require and gives you the feel, handling and feedback and grip you require then no-one should tell you it's wrong!
On soft springs you'll get a large wheel deflection for any given input, and the only things stopping the wheel moving a longer way are the spring rate itself and the compression resistance of the damper.
The damper has a wide range of compression and rebound resistance depending on how fast the wheel is being asked to move .. typically you would narrow these down into low speed , medium speed and high speed rates. In effect what you are talking about is piston speeds, ie the speed the rod is moving in the damper body.
To get good ride quality at sane speeds most dampers will run a low amount of low speed compression .. so that as you're pootling around town you aren't subjected to jarring through the car .. the piston rod has minimal damper resistance to movement and the majority is done by the spring. Any given input will allow the damper rod to move a significant distance on soft springs thus the wheel follows the bump but the car body doesn't.
At higher piston speeds the resistance is ramped up so it's possible to get a damper that offers good compliance at low piston speeds but good control at high piston speeds.
With low spring rates and low amount of damping you can get long piston rod travels at low piston speeds and also at low speeds get low damping forces .. hence the float you feel over long undulations .. in effect these are low piston speeds so low damping effects.
This in itself if kept limited is not a bad thing .. if the wheel follows the bump then the tyre contact patch is kept relatively stable .. the effect is called contact patch variation with load .. and if you stiffen the suspension you limit how freely the wheel can move .. the tyre then distorts more as it goes over the bump .. grip levels change and on the limit the handling will be unpredictable.
It's important not to go too soft .. that's why i always say for road use : use the softest damper setings you can whilst still giving you the control over the car that you require. This keeps the car as stable as possible whilst maintaining as consistent a contact patch as possible too. it makes for predictable, grippy on-road driving.
What you've noticed though now is that with the higher rate springs you've physically restricted the travel you can put the piston rod through because if you increase the spring rate you need more force to deflect it any given distance .. so if you drive the same road again with stiffer springs you'll notice that that car follows the bump in the road rather than it being absorbed by the spring/damper.
In actual fact your damper is exerting less control over the higher rate spring than before as the rebound damping hasn't been uprated .. but it *feels* more connected to the road because the car is following the bump rather the bump being absorbed.
Furthermore if you go stiffer on springs you increase the contact patch variation as you go over bumps .. finding the compromise that works for you is all the fun in suspension
presumably you've found a compromise that suits you and your driving better. On this note, someone came to me at a recent track day and said that *cerberas like to run stiff at the back* .. well as with so much in suspension circles it's utter garbage.
The general rule for a powerful rear drive car is front stiff rear soft .. how stiff and how soft you go is dependant entirely on what you want from the car. I think the person in question also doesn't appreciate the difference in wheel rate bewteen the front and back of most TVRs .. if you fitted the same spring to the front and the back you would still end up with a softer back end as the spring's mechanical advantage over the wheel is less.
What you need is a suspension that works for you and you alone .. if it does what you require and gives you the feel, handling and feedback and grip you require then no-one should tell you it's wrong!
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