Chassis strengthening for Chim/Griff
Discussion
If you're looking for performance/handling upgrades the most important thing to upgrade is the driver, and the next most important is all the connections between the driver and the car. Suspension tuning and mild upgrades would come next - these cars can be set up to handle very nicely without any chassis mods.
All elements of the car are being assessed during the rebuild - and there is reams and reams of information on most of them on PH.
What there is NOT, is information on chassis stiffening, which I am also in a position to do - hence this post requesting information from the knowledgeable about possibilities, which I can then assess individually during this part of the rebuild.
No point in starting the millionth post about the other components - the search functionality delivers all...
Just keeping it to chassis modifications from the collective knowledge and experience - please keep them coming! Thanks!
What there is NOT, is information on chassis stiffening, which I am also in a position to do - hence this post requesting information from the knowledgeable about possibilities, which I can then assess individually during this part of the rebuild.
No point in starting the millionth post about the other components - the search functionality delivers all...
Just keeping it to chassis modifications from the collective knowledge and experience - please keep them coming! Thanks!
It’s worth checking the integrity of the existing welds as a starting point.
Get the chassis shot blasted and carry out a close inspection of all the welded joints.
On an M chassis I did I found what I think was a Friday afternoon chassis. The welder must have run out of shield gas near the end of shift , but carried on welding anyway, leaving a lot of porous welds, proper aero chocolate!
I had to back grind and TIG over a lot of the welds.
That said the aero welds had lasted twenty odd years without breaking!
Get the chassis shot blasted and carry out a close inspection of all the welded joints.
On an M chassis I did I found what I think was a Friday afternoon chassis. The welder must have run out of shield gas near the end of shift , but carried on welding anyway, leaving a lot of porous welds, proper aero chocolate!
I had to back grind and TIG over a lot of the welds.
That said the aero welds had lasted twenty odd years without breaking!
IMHO, there is nothing apart from the rear top camber washer system NEEDS to be done to the chassis you 'could' replace all the body chassis body mounting plates with bespoke items folded with 15mm lips (then plasma cut down to 3mm) to increase the integrity of the flat plate and tie that lip into the round tubes (the shell is on 6mm rubber mountings anyway). Again in IMHO a rear hoop on a road car could damage you, if you went in backwards and got scooped up and hit it! For me connecting the steering to the chassis IN the shell would be a major improvement, tied into the outriggers and column (reward in feed back to your hands) and totally agree adding floor strengthening (I have 3" S/S plates above/below the shell on each bolt), but not connecting it to the chassis, they were only added to the later TVR's because the belts are attached to the seats not to the chassis (reward in feel to your bum!). A@ (100% agree with John on welding as there are so many missing/poor welds)
Edited by Adrian@ on Wednesday 26th July 07:57
LucyP said:
I don't know how many they have actually sold, or whether their website is up to date or whether the near £20K including VAT for a chassis is a standard or Evo one, or what that includes.
.
Be worth talking to them? .
£12K plus vat with own chassis the £20k is to replace the chassis with a whole new one, or just outriggers supplied fitted at £2,200 means if you just wanted a few extra bars it wouldn't cost too much more?
Certainly nowhere near 'Money you would never recoup' territory
https://www.sportmotive.com/tvr-chassis-outriggers...
Hi Dominic
I thought I would comment as we are getting a few recommendations. We have put a lot of development and research into chassis design over the years which lead to our Evolution chassis of which we are currently building car number 8, they tend to be full car rebuilds though with LS power so substantial costs.
What we do a lot of is apply what we have learned to standard chassis restoration and you are right to suggest doing it now when you do your body off resto as there are lots improvements that can easily be made to a standard chassis which will increase its rigidity and therefore improve the car’s handling.
We do add seat frames which helps and outriggers can be made in CDS which is a much stronger tube than the seamed tube TVR used and will give improved rigidity and side impact protection.
The main area though is installing additional tubes around the top of the transmission tunnel area and leading into the engine bay these reduce the amount of flex in this area, if you consider you have a large open area of the chassis where the engine and gearbox sit you can imagine how much this will move around so adding tubes here helps greatly, we often see lower box sections of chassis corroded due to the powder coat failing in a particular area where the engine bay meets the transmission tunnel and this indicates a lot of fatigue and movement at this point.
Your comments are correct about also tying the lower box sections together but you already have that in the exhaust carrier plate which is not just there to carry the exhaust it does tie the two lower box sections together so it is important to make sure that the plate is good and not corroded.
I would advise against a rear cage, we used to make them and yes they definitely add rigidity and would save you in a roll but the disadvantage of having tubes running very close to your head that you are likely to bash against in a minor collision far out ways the benefits in our opinion so we stopped making them, fine if you are building a track car and are going to be wearing a helmet but not in your road car.
Let me know if you want us to quote, we can restore you chassis and return it back to you freshly powder coated ready to build. We use a 3 stage powder coat system now that uses two epoxy primers bound together before applying the final colour coat.
I thought I would comment as we are getting a few recommendations. We have put a lot of development and research into chassis design over the years which lead to our Evolution chassis of which we are currently building car number 8, they tend to be full car rebuilds though with LS power so substantial costs.
What we do a lot of is apply what we have learned to standard chassis restoration and you are right to suggest doing it now when you do your body off resto as there are lots improvements that can easily be made to a standard chassis which will increase its rigidity and therefore improve the car’s handling.
We do add seat frames which helps and outriggers can be made in CDS which is a much stronger tube than the seamed tube TVR used and will give improved rigidity and side impact protection.
The main area though is installing additional tubes around the top of the transmission tunnel area and leading into the engine bay these reduce the amount of flex in this area, if you consider you have a large open area of the chassis where the engine and gearbox sit you can imagine how much this will move around so adding tubes here helps greatly, we often see lower box sections of chassis corroded due to the powder coat failing in a particular area where the engine bay meets the transmission tunnel and this indicates a lot of fatigue and movement at this point.
Your comments are correct about also tying the lower box sections together but you already have that in the exhaust carrier plate which is not just there to carry the exhaust it does tie the two lower box sections together so it is important to make sure that the plate is good and not corroded.
I would advise against a rear cage, we used to make them and yes they definitely add rigidity and would save you in a roll but the disadvantage of having tubes running very close to your head that you are likely to bash against in a minor collision far out ways the benefits in our opinion so we stopped making them, fine if you are building a track car and are going to be wearing a helmet but not in your road car.
Let me know if you want us to quote, we can restore you chassis and return it back to you freshly powder coated ready to build. We use a 3 stage powder coat system now that uses two epoxy primers bound together before applying the final colour coat.
Thank you so much Sportmotive - can't tell you how much I appreciate you taking the time out of your busy schedule to post.
Absolutely invaluable insight, based on real world research and experience - this is the kind of information that makes PH indispensable.
I will most likely be contacting you once the build commences...
Absolutely invaluable insight, based on real world research and experience - this is the kind of information that makes PH indispensable.
I will most likely be contacting you once the build commences...
Purely out of interest Dom, what do you intend to use the car for once completed, will it be a track car? Unlike some of the people commenting on this thread I don't race, I've done some track days in my Griff but it's really used as a weekend fun car that I've owned since new. If you are intending to race your car then ignore my comment but having driven numerous sports cars I do not find the Griffith chassis flexes much and there is minimal scuttle shake because it has a separate chassis. Good luck with whatever your do.
I’d tend to agree with Rich above.
Unless your driving at 10/10ths I doubt you’d notice any real difference on a road car.
Tyre grip levels are not consistently high enough and bumpy roads will cause lack of traction much sooner than a bit of flex hear and there.
If it’s a track car there would be far more justification for it but even then given the fact that 20 mins on track is a long time the chassis and engine should be rested and cooled down for at least an hr in between runs if you want the performance window back.
Tvr are very difficult to drive fast on uneven roads such as ours here in the U.K
They are far more suited to smooth tracks where you know where the bumps are and corner speeds are truly fast.
Unless your a Lando Norris kind of flat out driver and on busy roads that’s almost impossible or very dangerous I can’t really see where or when your going to push the car so heavily to recognise chassis flex.
I’ve done both trackdays and thousands of road miles in my TVR and rarely if ever did I feel the Chassis flex.
It might have been there but my senses never picked it up.
Strengthening can never be a bad idea though so and if your in a re build stage it makes very good financial sense to do it now based on the good advice from those who have done it. Goodluck
Unless your driving at 10/10ths I doubt you’d notice any real difference on a road car.
Tyre grip levels are not consistently high enough and bumpy roads will cause lack of traction much sooner than a bit of flex hear and there.
If it’s a track car there would be far more justification for it but even then given the fact that 20 mins on track is a long time the chassis and engine should be rested and cooled down for at least an hr in between runs if you want the performance window back.
Tvr are very difficult to drive fast on uneven roads such as ours here in the U.K
They are far more suited to smooth tracks where you know where the bumps are and corner speeds are truly fast.
Unless your a Lando Norris kind of flat out driver and on busy roads that’s almost impossible or very dangerous I can’t really see where or when your going to push the car so heavily to recognise chassis flex.
I’ve done both trackdays and thousands of road miles in my TVR and rarely if ever did I feel the Chassis flex.
It might have been there but my senses never picked it up.
Strengthening can never be a bad idea though so and if your in a re build stage it makes very good financial sense to do it now based on the good advice from those who have done it. Goodluck
Another mod , though not strength related , that I have done with great results is mount the rear shocker in a more upright position . I did this first on my griff sometime in the last century . I made a bracket that bolted onto my chassis through the original shocker mounting and down to the main chassis rail . It changed from the standard unpredictable backend to a car that could outcorner an integrale overnight even on spax adjustables .
I have since done something similar to all my TVRs and recently tried on my T350 but could not do it due to the boot floor being in the way so I mounted the shocker under the wishbone instead.
I have since done something similar to all my TVRs and recently tried on my T350 but could not do it due to the boot floor being in the way so I mounted the shocker under the wishbone instead.
LucyP said:
Someone mentioned the Sportmotive Evo chassis. Read their website about it: https://www.sportmotive.com/tvr-evolution-chassis/
They seem to have done actual research, and changed many parts including hubs, brakes, wishbones, dampers, materials, shapes, tube size.
Since Sportomotive appear to be reading this thread, they may wish to comment on this themselves, but I note that their website says:They seem to have done actual research, and changed many parts including hubs, brakes, wishbones, dampers, materials, shapes, tube size.
Back when I had my Griffith, I did my own analysis of the suspension geometry (I used to mess around setting up suspension on hillclimb and race cars as a hobby/sideline), in response to certain 'foibles' (to put it politely) that I'd identified with the handling on my car.
It turned out that (as Sportomotive are saying) the rear roll center in particular showed significant sideways migration and (perhaps more importantly) under some combinations of roll and squat would leap from one side to the other, migrating vertically as it did so. Without wishing to get too technical, the roll couple (the distance between the geometric roll centre and the centre of gravity of the sprung mass) is one of the factors that dictates diagonal weight transfer when you're cornering, so this sort of sudden movement is a very bad thing. The best analogy I can give is that it's like an over-centre catch going over centre, so that at one instant you're having to apply maximum force, then the next instant that force drops away suddenly.
If the geometry on the Sportomotive chassis resolves this issue, I'd say that it's worth it on those grounds alone - it might just save your life - never mind any benefits to torsional stiffness.
It would be good if Sportmotive could clear up what I think is confusing here. As I understand it, they offer:
(1) an outrigger replacement;
(2) repairs to your existing chassis;
(3) a new standard chassis;
(4) an evo chassis.
As I understand it, (and I might be completely wrong) only the evo chassis offers the changes and upgrades that they have made after studying the TVR chassis carefully. This is really aimed at or perhaps exclusively is for the cars being converted to take a US V8. They are currently making their 8th evo chassis I think. I don't think that they have quoted a price for the evo chassis, but I expect that it is £20something thousand plus vat.
(1) an outrigger replacement;
(2) repairs to your existing chassis;
(3) a new standard chassis;
(4) an evo chassis.
As I understand it, (and I might be completely wrong) only the evo chassis offers the changes and upgrades that they have made after studying the TVR chassis carefully. This is really aimed at or perhaps exclusively is for the cars being converted to take a US V8. They are currently making their 8th evo chassis I think. I don't think that they have quoted a price for the evo chassis, but I expect that it is £20something thousand plus vat.
plasticman said:
You could also weld on some mounting bobbins on to the spine in line with the out riggers which would make the tunnel more of a stressed member .
Plasticman, I wonder if you have the time, whether you might be able to elaborate on the mounting bobbins you refer to - are these extra connections for the body to bolt on to, or are they in reference to bracing the outriggers somehow?Many thanks,
Dom
Dominic TVRetto said:
Perhaps I should have used the word "stiffness" - if rigidity is different?
Loads of anecdotal feedback, Maclaren test rig story, analysis document PDF from the time TVR were developing the Cerbera (used to be available on MCS Software website, but unfortunately now unavailable).
Thanks all, keep them coming!
Harry Metcalfe referenced that McLaren rig story in his last Griff update on his YouTube channel.Loads of anecdotal feedback, Maclaren test rig story, analysis document PDF from the time TVR were developing the Cerbera (used to be available on MCS Software website, but unfortunately now unavailable).
Thanks all, keep them coming!
It surprises me. As a (very) unscientific observation, I noticed when jacking up the rear of my Chim on one of the triangulated reinforcement plates on the outrigger corner, the front wheel comes off the ground at about the same time as the rear does, which to my untrained mind suggests exceptional rigidity. Never actually had a car that did this before (although a 106 XSi came close).
MikeE said:
the only real way to stiffen a backbone chassis (other than a very comprehensive full cage) is to do what Gordon Murray's i-stream does and put sandwich panels bonded between the chassis tubes to brace them and reduce the flex, that's what they did on the T400's and Cerbera S12 I believe
That´s exactly what I did as part of my ´Black Label´ suite of upgrades. Cost me a couple of years of my life, but the difference is very noticeable on the road - the car feels much more precise and direct, squeaks and rattles from the structure have gone and you have a far better idea of what´s going on underneath. This all in normal road driving, just like with having top grade suspension, the notion of ´it´s only detectable when you´re driving 10/10ths/ on track etc.` is a falsehood. My chosen TVR whisperer in the Netherlands - one of two TVR-approved workshops there - was sceptical whether it would make any difference, too. He was converted the moment he had the car on the lift and noticed how much better the doors opened/closed with the wheels in the air!
In summary, after you´ve sorted everything else the lack of main chassis stiffness is what makes TVRs of this generation feel like an ´old´ car compared to more modern sports cars. It makes much more sense to address this area than to swap bigger/newer engines, gearboxes etc. in.
plasticman said:
Another mod , though not strength related , that I have done with great results is mount the rear shocker in a more upright position . I did this first on my griff sometime in the last century . I made a bracket that bolted onto my chassis through the original shocker mounting and down to the main chassis rail . It changed from the standard unpredictable backend to a car that could outcorner an integrale overnight even on spax adjustables .
That´s extremely interesting - sounds like this could be a strictly bolt-on item that you could make & sell for easy DIY install? 
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