Tuscan front suspension facts and experiment
Discussion
yzf1070 said:
Gob smacked reading this.... the single biggest improvement (IMHO) that can be made over the standard set up is replacing the Bilstein dampers... I went for the tried, tested and proven Nitrons and the difference... well lets say the earth moved for me n my TIV. Stability at high speed, cornering and standing starts - awesome, cars handling is beyond my capabilities. I am however, intriuged by the authors intent on experimentations... Is the car being set up for track days, or racing?
What spring rates ?spitfire4v8 said:
Good set up wouldnt cure massive bumpsteer. Ive never measured massive bumpsteer is what im saying (and ive measured a lot of tvrs over the last 20 years of working on them) , so the tiny bumpsteer isnt the issue as far as im concerned, bad set up might be however.
What was the mod you used to do re bump steer? I remember you mentioning it when I asked you about Nitron fitting and setup. Basil Brush said:
What was the mod you used to do re bump steer? I remember you mentioning it when I asked you about Nitron fitting and setup.
hmm can't remember. I did refine a kit that a guy at a previous garage i worked at had done but he got it wrong so I fixed it for him. however that was a rack extender and rack raise shim kit. I wasn't convinced of it anyway, just i was asked to sort it out so I did. I think they made something like 20 kits made and sold 2 which probably tells you all you need to know. 
yzf1070 said:
I am however, intriuged by the authors intent on experimentations... Is the car being set up for track days, or racing?
My aim from all of this is to learn about suspension geometry and to dispel/validate the myths about Tuscan cornering and stability over bumps. As I mentioned before, I was the first to try the 3mm spacers from Silverstone Performance on my 04 Tuscan. Prior to fitting the spacers it was a pig to drive over rough stuff. The car had 7500miles from new and had been checked and set up at TVR Power. To all intents and purposes it was new and as the factory intended. Post spacers its was SO much better. There's a road with dips and bumps on the curb side near my house that throws most cars around as you ride over them. The Tuscan used to be the worst of the cars I owned, in terms of handling as it went over these bumps. Post 3mm spacers it was the best and I could hold onto the wheel with my finger and thumb (perviously had to use firm grip and white knuckles!).Having learnt that my current Cat D car was built in Jan '00 (very early car) and that there were differences between the geo implemented over time, I was keen to understand what changes TVR made and when they occured. Due to all the whispers and hearsay, I decided the best way to know for sure what was happening, was to do as scientific an experiment as possible use new parts and write it up as an experimental report for TVR enthusiasts to digest and comment on. This thread is the result of that work.
I'm now at a cross roads where I cold change all the bits for post 2002 parts it becuase it is just at rolling chassis at the moment. However, the bump steer traces show minor 1mm deflection in the middle 80% of travel, so to me that looks OK. Time and money is also against me. I want to make progress, not go backwards in the rebuild. I am also curios to experience the current set up. So I'm going to leave it as is, drive it on the road and track and then consider what changes to make next winter.
spitfire4v8 said:
hmm can't remember. I did refine a kit that a guy at a previous garage i worked at had done but he got it wrong so I fixed it for him. however that was a rack extender and rack raise shim kit. I wasn't convinced of it anyway, just i was asked to sort it out so I did. I think they made something like 20 kits made and sold 2 which probably tells you all you need to know.
Interesting! Widening/extending and rasing the rack is what TVR did in 2001, but they also moved the top ball joint outwards to reduce KPI.So by moving the steering rack ball joint out was to address the fact that the rack's/rod's inner ball joint did not align with the line between the upper and lower wishbone's chassis pick up points?
Edited by MPETT on Tuesday 7th February 10:40
It was done purely because that's what tvr did with the later cars so must be the right thing to do right?
I have a theory that tvr with the later cars had a flagship track/road car with the sag and so based the steering rack length around that car, and tvr being tvr they gave every other car the same rack? I would love to know if there were actually separate racks for the sag and then for the other cars. The sag moves the wishbone inner pivots outwards so a longer rack would seem logical. I'm not convinced it's a worthwhile upgrade for non sag wishbone point cars though, but it depends what you're trying to achieve of course and ive never experienced the kind of unruly behaviour with the lesser cars that others have reported either. Also people are obsessed with moving the rack up and down, but rarely give any thought to moving it forwards or backwards or changing the hub steering arms to change the apparent ackermann effect/toe out on turns.
I have a theory that tvr with the later cars had a flagship track/road car with the sag and so based the steering rack length around that car, and tvr being tvr they gave every other car the same rack? I would love to know if there were actually separate racks for the sag and then for the other cars. The sag moves the wishbone inner pivots outwards so a longer rack would seem logical. I'm not convinced it's a worthwhile upgrade for non sag wishbone point cars though, but it depends what you're trying to achieve of course and ive never experienced the kind of unruly behaviour with the lesser cars that others have reported either. Also people are obsessed with moving the rack up and down, but rarely give any thought to moving it forwards or backwards or changing the hub steering arms to change the apparent ackermann effect/toe out on turns.
yzf1070 said:
Gob smacked reading this.... the single biggest improvement (IMHO) that can be made over the standard set up is replacing the Bilstein dampers... I went for the tried, tested and proven Nitrons and the difference... well lets say the earth moved for me n my TIV. Stability at high speed, cornering and standing starts - awesome, cars handling is beyond my capabilities. I am however, intriuged by the authors intent on experimentations... Is the car being set up for track days, or racing?
Is your car a Tuscan Sis this not the first of the cars with all the updated parts on, reduced KPI on uprights tuscan rack ect ect
or are you talking about other early cars
yzf1070 said:
Gob smacked reading this.... the single biggest improvement (IMHO) that can be made over the standard set up is replacing the Bilstein dampers... I went for the tried, tested and proven Nitrons and the difference... well lets say the earth moved for me n my TIV. Stability at high speed, cornering and standing starts - awesome, cars handling is beyond my capabilities. I am however, intriuged by the authors intent on experimentations... Is the car being set up for track days, or racing?
I thought a 2003 Tuscan Mk1 would have Harvey Bailey Springs and Dampers when it left the factory not Bilstein and Eibach springs .... stand to be correctedNo I havent but as I said ive never noticed anything in the std geo that's made me really want to change it or investigate anything else. However having said that Ive got a couple of cars that are used on track and I'm looking at front and rear changes to those but focussed on roll centre and damper positioning primarily, it might involve a change to the lower front hunb steering arm so could look at both upper and lower ball joint positions in more detail then.
Edited by spitfire4v8 on Wednesday 8th February 07:41
Just watched your bump steer measurement vids Martin and it's interesting to see the rate that it goes into toe-out on droop. It looks as though each wheel could have 1" bump toe-in anywhere between 1mm and 3.5mm depending what ride height it was set at. May partly explain why fitting Nitrons etc with a slightly lowered ride height gives such an improvement.
How did you define ride height?
How did you define ride height?
Basil Brush said:
Just watched your bump steer measurement vids Martin and it's interesting to see the rate that it goes into toe-out on droop. It looks as though each wheel could have 1" bump toe-in anywhere between 1mm and 3.5mm depending what ride height it was set at. May partly explain why fitting Nitrons etc with a slightly lowered ride height gives such an improvement.
How did you define ride height?
Hi mr Brush,How did you define ride height?
I'm not sure where you've got 1" from??
. My take on the results was that for 80% of the travel, the most used range of travel, the toe out and in was acceptable (with an extra 2-4mm of rack spacing.) Toe in was minimal (less than 1mm) in the middle 80% of travel) with toe out mainly at the extremes of bump and droop. The interesting results were when I did the test with 10-15degs of steering lock. In this instance at the top end of the compression/bump, the toe out was pretty extreme (5mm). So... I have concluded, that for my set up on my early car, that I need a firmIsh shock setting with an anti roll bar that limits travel at the extremes of bump and under heavy cornering. Im thinking the standard anti roll bar will do the trick?
This ties into the established general knowledge for Tuscan handling, that a replacement of the shocks with firmer shock settings along with the correct profile tyre helps to create a less twitchy car.
I'll be trying the spacers as well as there seems to be some positive feedback on the early cars that have used the spacers. I'll report back when I get the car on the road. Hopefully before the end of the summer.
Martin
What sort of ride height do you think Walford? I suppose to get it right you would need to do the bump test.
I agree with mpett as well, i have found that my car on gaz gold pro and using 10mm of rack spacers does handle a lot better the stiffer it gets.
Stiff as it goes all round is very good but its also VERY stiff and just too uncomfortable, i backed off the adjusters about a quarter and its really quite good. On track it really benefits from fully stiff.
I also find tyre pressures make a huge difference.
I notice some recomend 26-28psi, well i put some yoko ad08 on and even at 24 the car felt a bit vague, i think with these that 22 when warm is good, so maybe 20 when cold. That said the tyre walls are much stiffer than a normal tyre. Steering feels much nicer like this.
I agree with mpett as well, i have found that my car on gaz gold pro and using 10mm of rack spacers does handle a lot better the stiffer it gets.
Stiff as it goes all round is very good but its also VERY stiff and just too uncomfortable, i backed off the adjusters about a quarter and its really quite good. On track it really benefits from fully stiff.
I also find tyre pressures make a huge difference.
I notice some recomend 26-28psi, well i put some yoko ad08 on and even at 24 the car felt a bit vague, i think with these that 22 when warm is good, so maybe 20 when cold. That said the tyre walls are much stiffer than a normal tyre. Steering feels much nicer like this.
MPETT said:
Hi mr Brush,
I'm not sure where you've got 1" from??. My take on the results was that for 80% of the travel, the most used range of travel, the toe out and in was acceptable (with an extra 2-4mm of rack spacing.) Toe in was minimal (less than 1mm) in the middle 80% of travel) with toe out mainly at the extremes of bump and droop. The interesting results were when I did the test with 10-15degs of steering lock. In this instance at the top end of the compression/bump, the toe out was pretty extreme (5mm).
So... I have concluded, that for my set up on my early car, that I need a firmIsh shock setting with an anti roll bar that limits travel at the extremes of bump and under heavy cornering. Im thinking the standard anti roll bar will do the trick?
This ties into the established general knowledge for Tuscan handling, that a replacement of the shocks with firmer shock settings along with the correct profile tyre helps to create a less twitchy car.
I'll be trying the spacers as well as there seems to be some positive feedback on the early cars that have used the spacers. I'll report back when I get the car on the road. Hopefully before the end of the summer.
Martin
My query was, with the standard set up, as you drop the suspension the laser trace looks to almost go horizontal as it moves into toe out. If the car ride height was raised so that it sat in this part of it's travel, it could result in large toe in or out deviations for not much suspension movement. That's why I was asking about your ride height start point.I'm not sure where you've got 1" from??
. My take on the results was that for 80% of the travel, the most used range of travel, the toe out and in was acceptable (with an extra 2-4mm of rack spacing.) Toe in was minimal (less than 1mm) in the middle 80% of travel) with toe out mainly at the extremes of bump and droop. The interesting results were when I did the test with 10-15degs of steering lock. In this instance at the top end of the compression/bump, the toe out was pretty extreme (5mm). So... I have concluded, that for my set up on my early car, that I need a firmIsh shock setting with an anti roll bar that limits travel at the extremes of bump and under heavy cornering. Im thinking the standard anti roll bar will do the trick?
This ties into the established general knowledge for Tuscan handling, that a replacement of the shocks with firmer shock settings along with the correct profile tyre helps to create a less twitchy car.
I'll be trying the spacers as well as there seems to be some positive feedback on the early cars that have used the spacers. I'll report back when I get the car on the road. Hopefully before the end of the summer.
Martin
Marcus
Hi Marcus, I get what your saying and think that makes sense.
My set up to determin the ride height was to ensure the bottom wishbone mount and bottom upright ball joint were level.
In my case I'm definitely going to benefit from the rack being raised a little. To me the standard set up trace is not acceptable.
My set up to determin the ride height was to ensure the bottom wishbone mount and bottom upright ball joint were level.
In my case I'm definitely going to benefit from the rack being raised a little. To me the standard set up trace is not acceptable.
Have you checked to see what scrub rad your car it is running
I was looking at my car which has the drillings for the both top ball joint positions on the upright and i think TVR moved the scrub rad inboard (more positive) by about 9mm in 2001
I was looking at my car which has the drillings for the both top ball joint positions on the upright and i think TVR moved the scrub rad inboard (more positive) by about 9mm in 2001
Edited by Walford on Friday 2nd March 07:41
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